29th MRA: New Perspectives The Abstractssociety4mra.org/wp-content/uploads/2017/10/SMRA... · Exploring Binning Strategies for Respiratory Motion-resolved Coronary MRA in Patients

SMRA 201729th Annual International ConferenceMRA: New Perspectives

The Abstracts

StellenboschSpier 1692 – Hotel | Spa | Vineyard

Pre-Conference Educational WorkshopTuesday, October 3rd

Main ConferenceWednesday, October 4th

Thursday, October 5th Friday, October 6th

President: James Carr

Organizer: David Saloner

Endorsed by: International Society of Magnetic Resonance in Medicine Society for Cardiovascular Magnetic Resonance Radiology Society of South Africa

SMRA 201729th Annual International ConferenceThe Abstracts

Table of Contents

SMRA 201729th Annual International ConferenceThe Abstracts: Table of Contents

Oral PresentationsAlphabetical by last name.

— Bradley AllenCardiac MRI Heart Deformation Analysis Demonstrates Regional Heterogeneity in Myocardial Strain in HIV+ Patients

— Maria AristovaAutomated Analysis of 4D-flow MRI Data in Cerebral Arteriovenous Malformations

— Alex BarkerFeasibility of 4D-flow-based PCMRA Volumetry to Measure Longitudinal Ascending Aorta Growth

— Thorsten BleyMRI Displays Mural Inflammatory Changes of Intracranial Arteries in Giant Cell Arteritis

— Romain BourcierMRI Quantitative T2 Mapping on Thrombus to Predict Recanalization After Endovascular Treatment for Acute Anterior Ischemic Stroke

— Nicholas BurrisInitial Experience with 4D-flow Imaging in Patients with Dissection of the Descending Thoracic Aorta

— Nicholas BurrisEccentric Flow in the Ascending Aorta is Associated with Aortic Growth in Patients with Isolated Bicuspid Aortic Valve

— Mariana BustamanteAutomated Cardiac Segmentation in 4D-flow MRI

— Huijun ChenImaging Findings in Pulsatile Tinnitus Patients Using Black-blood MRI: a Retrospective Study

— Jeremy CollinsPredicting Hepatocellular Carcinoma Treatment Response to Yittrium-90 Radioembolization by Quantitative Perfusion Using Contrast-enhanced Magnetic Resonance Angiography with Echo Sharing and Radial K-space Sampling

— Ryan DolanRole of Structure-function Cardiac MRI in the Detection of Acute Cardiac Allograft Rejection after Heart Transplantation

— Charles DumoulinA Novel Approach to Reduce Scan Times with Simultaneous QFlow & bSSFP Imaging within the Same Breath Hold

— Tora DunåsAutomatic Blood Flow Measurements in 4D-flow MRI

— Robert Edelman Breath-hold Coronary MRA at 3 Tesla Using Fast Interrupted Steady-state

— Robert Edelman Ungated, Free-breathing, “No Hassle” Imaging Strategy for Nonenhanced Peripheral MR Angiography at 3 Tesla

— Laura Eisenmenger MRI Compatible Animal Model of Vessel Wall Imaging Using a T1-weighted Black Blood Technique and DCE MRI



— Zhaoyang FanQuantitatively Monitoring Regression or Progression in Intracranial Atherosclerotic Plaques Using 3D Vessel Wall Imaging

— Farshid FarajiEffect of Reference Vessel Selection on an Image Processing Pipeline for the Longitudinal Surveillance of Intracranial Aneurysms

— Sylvana García-RodríguezComparison of Contrast and Non-Contrast Phase Contrast Magnetic Resonance Angiography in Infants

— Dariusch HadizadehIntra-individual Quantitative and Qualitative Comparison of Macrocyclic Contrast Agents in Multi-phase 3D-MRA and 4D-MRA at 1.5T and 3T in Minipigs

— Henrik HaraldssonHighly Accelerated Multi-directional Motion Encoded 4D-flow MRI

— John HeerfordtExploring Binning Strategies for Respiratory Motion-resolved Coronary MRA in Patients

— Carson HoffmanContinuous Intracranial Flow MRI with High Frame Rates

— Rami HomsiPreliminary Experience with Simultaneous Arterial and Venous High-resolution Late-phase Imaging of the Run-offs Using Gadobutrol

— Keiji IgasePrediction of Progressing Stroke in Branch Atheromatous Disease Using 3T MRI

— Haruo IsodaParameters Based on Blood Flow Velocity of Cerebral Intracranial Aneurysms: Comparative Study with Computational Fluid Dynamics

— Kevin JohnsonAccelerated, SMS-MOTSA, Radial 4D-flow Imaging with Magnetization Transfer Preparation

— Lilli KaufholdImage-based Assessment of Uncertainty in Carotid Lumen Quantification

— Seong-Eun KimMeasurement of T2 of Symptomatic and Asymptomatic IntraPlaque Hemorrhage by Using Motion Insensitive 3D Multiple Echo Inversion Recovery Stack of Star (ME IR SOS) Technique

— Ioannis KoktzoglouRapid, Large Field-of-View Neurovascular MRA Using an Ungated Radial Quiescent-Interval Slice-Selective (QISS) Protocol



— Ioannis KoktzoglouRadial Fast Interrupted Steady-State (FISS) Magnetic Resonance Angiography

— Dara KraitchmanValidation of MRA and CBCT to Evaluate Response to Stem Cell Therapy in a Rabbit Model of Peripheral Arterial Disease

— Joseph LeachMRI/MRA Based Models of Abdominal Aortic Aneurysm Mechanics

— Tim LeinerCardiovascular MR Image Segmentation in Congenital Heart Disease Using a Dilated Convolutional Neural Network

— Rui LiIntegrating a Novel Low-rank Model with Parallel Imaging, to Enable Real time 4D-flow MRI

— Bo LiFast Carotid Artery MR Angiography with Compressed Sensing Based Three-dimensional Time-of-Fight Sequence

— Jing LiuCardiorespiratory-resolved 3D Continuous First-pass Cardiac Perfusion MRI

— Xian LiuSaccular Intracranial Aneurysm Wall Permeability and Shear Stress Distribution: a Further Insight into Rupture Pathogenesis

— Michael LoecherOptimizing TE and TR of 4D-Flow Acquisitions for Reduced Scan Times

— Daniel LudwigTime-resolved Three-dimensional Phase-contrast (4D-flow) MRI of the Portal Circulation Before and After Branch Portal Vein Embolization

— Kai LudwigPlacental Perfusion MRI: ASL FAIR and Ferumoxytol DCE in the Rhesus Macaque

— Liliana MaAortic 3D Hemodynamics in Patients with Unicuspid and Partial Fusion Bicuspid Aortic Valve Disease

— Jeffrey MakiFinding the Optimal Injection Strategy for Contrast-enhanced MR Angiography

— John OshinskiCircumferential Heterogeneity of Aortic Wall Displacement and Strain Assessed with Cine DENSE MRI

— Onur OzyurtIntegration of ASL into Stereotactic Radiosurgery of AVMs



— Davide PicciniAutomated Cardiac Resting Phase Detection in 2D Cine MR Images for Acquisition Window Selection in Coronary MRI: Preliminary Results

— Nils PlankenBileaflet Mechanical Aortic Valves do not Alter Shear Stress or Aortic Diameter

— Qin QinCerebral Arteriography and Venography Using Velocity-selective Pulse Trains

— Aleksandra RadjenovicMyocardial Fractional Blood Volume Estimation Using Ultra Low Dose Ferumoxytol Enhanced MRI and Three-compartment Model of Water Exchange in Patients with Chronic Kidney Disease

— Amir Ali RahseparComprehensive Evaluation of Extracellular Volume Measurements and Myocardial Scar Detection by Late Gadolinium Enhanced Cardiac MR using Gadoterate Meglumine

— Vitaliy RayzComparison of 4D-flow MRI Measurements to PIV and CFD Modeling

— Alejandro Roldán-AlzateVentricular Kinetic Energy in Healthy Volunteers Using Respiratory Gated 4D-flow MRI

— Trisha RoyMRI Characteristics of Lesions Relate to the Difficulty of Peripheral Arterial Endovascular Procedures

— Trisha RoyFrom Bench to Bedside: Validation of Native-contrast MRI Techniques to Characterize Popliteal and Tibial Chronic Total Occlusions from Critical Limb Ischemia Patients

— Mark SchieblerInitial Experience with Velocity Selective Arterial Spin Labeling for Non-contrast Neurovascular Imaging

— Mark SchieblerPET-MR of a new Fibrin Binding Agent in a Porcine Model of Acute Pulmonary Embolism

— Susanne SchmidVisualizing Small Arteries in the Brain Using Fluid Suppressed Balanced SSFP MR Angiography

— Michaela SchmidtLow-dose Dynamic CE-MRA Employing Iterative Reconstruction: Gains and Limitations

— Xin Shen Voxel-by-Voxel 4D-flow MRI Based Assessment of Reverse Flow in the Aorta

— Zhang ShiCharacterization of the Vulnerable Intracranial Atherosclerotic Plaque Features by High Resolution MRI and a Quantitative Radiomics Approach



— Monica SigovanEvaluation of Inflammatory Processes in Carotid Atherosclerosis Using 18F-NaF Enhanced PET/MRI: Preliminary Results

— Roberto SouzaCommon Carotid Artery Lumen Segmentation from Cine Fast Spin Echo Magnetic Resonance Images

— Eric StinsonHigh Spatiotemporal Resolution 3D Contrast-enhanced MR Angiography with a Compact 3T Scanner

— Sokratis StoumposFerumoxytol-enhanced Magnetic Resonance Angiography (FeMRA) for the Assessment of Potential Kidney Transplant Recipients

— Sokratis StoumposFerumoxytol-enhanced Magnetic Resonance Angiography (FeMRA) for the Assessment of Patients with Complex Anatomy Due for Vascular Access Creation

— Matthias StuberFully Self-gated Push-button Non-contrast 5D Imaging of the Heart

— Bing TianApplication of 3D SPACE MRI on Intracranial Aneurysm: A Preliminary Study

— Johannes TögerCerebrospinal Fluid (CSF) Flow in the Cerebral Aqueduct can be Quantified with High Resolution Using Magnetic Resonance Imaging at 7 Tesla

— Mostafa TolouiIn-vivo 4D-flow MRI at 10.5T: Feasibility Study

— Alireza ValiAutomatic Quantification of the Impact of Intracranial Atherosclerotic Lesions on Cerebrovascular Hemodynamics Using 4D-flow MRI

— Xinrui WangUnruptured Intracranial Aneurysms: Relationship Between Wall Enhancement and Rupture Risk Factors Based on High-resolution Magnetic Resonance Imaging

— Yan WangInternal Jugular Vein and Common Carotid Artery Separation in Pulsatile Tinnitus Patients Using Level Set Based Shape Prior Segmentation

— Sebastian WeingärnterHigh Resolution Dynamic T1 Mapping Using a Combination of Cardiac-phase Resolved Steady-state Look-locker Imaging and Locally Low-rank Denoising

— Yan WenFirst Experience with Free-breathing Cardiac Quantitative Susceptibility Mapping in Patients Post Gadolinium Administration



— Oliver Wieben4D-flow MRI of Uterine Blood FLow in the Pregnant Rhesus Macaque: Flow Distribution and Reproducibility

— Yibin XieCarotid All-In-One: Comprehensive Quantitative Evaluation of Atherosclerosis in One Scan

— Chun YuanCharacterization of Carotid Plaque Magnetic Resonance Imaging with Deep Learning Convolutional Neural Networks

— Qiang ZhangAutomatically Identify Plaque Components in Carotid Artery using Simultaneous Non-contrast Angiography and IntraPlaque Hemorrhage (SNAP) Imaging

— Chengcheng ZhuGated Thoracic Magnetic Resonance Angiography at 3T: Is Contrast Needed?


Poster PresentationsAlphabetical by last name.

— Manuela AschauerMR Angiography in Patients After MRI Compatible Pacemaker/IECD Implantation

— Waleed BrinjikjiComparison of Efficacy of Standard Neurovascular Coil to Dedicated Carotid Surface Coil in Evaluation of Intraplaque Hemorrhage

— Ty Cashen3D TOF with Compressed Sensing for Peripheral Non-contrast MRA

— Hou-Jen ChenCalf Reactive Hyperemia Indicates Severity and Predicts Functional Outcome of Limb Ischemia: a Pilot Study Using Arterial Spin Labeling and Model-based Analysis

— Yalun ChenThe Atherosclerosis of Circle of Willis Detected by Black-blood MRI are Different Between Stroke Patients and Asymptomatic Controls

— J. Rock HadleyRF Coil for Comprehensive Neurovascular Imaging

— Rami HomsiAortic Stiffness, Epicardial Fat, Left Ventricular Myocardial Fibrosis and Contractility in Patients with Hypertension and Diabetes Mellitus

— Tim LeinerTowards a 256-channel Cardiac Receive Coil Array to Facilitate One Order of Magnitude Faster Cardiac MR

— Sébastien LevillySpatio-temporal Filtering of Blood Flow in 4D Phase-contrast Magnetic Resonance Imaging

— Dong Woo ParkPerfusion Abnormality in Posterior Inferior Cerebellar Artery Termination of Vertebral Artery on Arterial Spin Labeling and Dynamic Susceptibility Contrast Perfusion MRI

— Vitaliy RayzOntological Approach to Detecting Imaging Artifacts in MRA images

— Emma RoditiBody Shape Index, Left Ventricular Remodelling and Atherosclerosis — An Observational Study

— Monica SigovanRespiratory-resolved Self-gated 3D Radial 4D Flow MRI: Initial Results

— Julia VelikinaHighly Accelerated Dynamic MRI Using Information-based, Rank-adaptive Reconstruction

— Xihai ZhaoAtherosclerotic Diseases in Entire Craniocervical Arteries from Aortic Arch to Intracranial Arteries and Stroke Risk: A 3D Multicontrast MR Vessel Wall Imaging Study


Oral Presentations


— Bradley AllenCardiac MRI Heart Deformation Analysis Demonstrates Regional Heterogeneity in Myocardial Strain in HIV+ Patients

Cardiac MRI heart deformation analysis demonstrates regional heterogeneity in myocardial strain in HIV+ patients.

Bradley D. Allen1, Matthew J. Feinstein2, Shanna Fang1, Daniel C. Lee2, James C. Carr1, Jeremy D. Collins1

1. Northwestern University, Department of Radiology; 2. Northwestern University, Department ofCardiology

Purpose: Human immunodeficiency virus (HIV) infection appears to be associated with cardiac dysfunction beyond that expected from epicardial coronary artery disease alone. Metabolic dysfunction, virus- and HIV medication-related toxicity, and microvascular dysfunction may all contribute to HIV-associated myocardial dysfunction. Myocardial strain is a sensitive quantitative marker of subclinical cardiac dysfunction that may be useful in evaluating cardiac disease in HIV+ patients, and cardiac MRI heart deformation analysis (HDA) can be used to quantify myocardial strain. We hypothesize that HIV+ patients will demonstrate regional heterogeneity and reduced HDA-quantified circumferential and radial myocardial strain compared to healthy controls.

Methods: The study included 32 HIV+ subjects identified from an IRB approved registry who had undergone clinically indicated cardiac MRI (49 ± 11 years, 27 men, 23 with adjudicated heart failure (HF)), and 18 healthy volunteers (46 ± 11 years , 18 men). Balanced SSFP, ECG-gated cine MRI in short axis was performed at the base, mid, and apex (temp res 39.2 msec). Deformation fields were evaluated using prototype software (Siemens Corp., Princeton, NJ) to calculate peak circumferential (Ecc) and radial (Err) strain at each short axis slice. Groups were compared using t-test or ANOVA with Bonferroni correction as appropriate.

Results: HIV+ patients demonstrated reduced regional Ecc and Err compared to controls (p ≤ 0.001). While Ecc at the apex was relatively reduced compared to the basal slice in controls, there was a distinct base-to-apex gradient of Ecc reduction in HIV+ patients (p < 0.02 for all interslice comparisons). Err also demonstrated regional heterogeneity in HIV+ patients, with relatively less strain reduction in the mid myocardial slice compared to the base and apex (p < 0.001 compared to base and p = 0.1 compared to mid).

Discussion: HDA-derived circumferential and radial myocardial strain is reduced in HIV+ patients relative to healthy controls, and there is regional heterogeneity in the relative impact on both radial and circumferential strains. These findings may reflect disease-specific patterns which could aid in risk-stratification and surveillance of HIV+ patients using cardiac MRI. Correlating these findings with HIV disease status, HIV and cardiovascular treatments, and other comorbidities is needed to better understand the utility of cardiac MRI with HAD-derived myocardial strain in this cohort.

References:

C Holloway, et al. "Comprehensive Cardiac Magnetic Resonance Imaging and Spectroscopy Reveals a High Burden of Myocardial Disease in HIV Patients." Circulation (2013): CIRCULATIONAHA-113.

DK Thiara, et al. “Abnormal Myocardial Function Is Related to Myocardial Steatosis and Diffuse Myocardial Fibrosis in HIV-Infected Adults.” J Infect Dis 2015; 212 (10): 1544-1551.

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— Maria AristovaAutomated Analysis of 4D-flow MRI Data in Cerebral Arteriovenous Malformations

Automated analysis of 4D Flow MRI data in cerebral arteriovenous malformationsMaria Aristova1, Alireza Vali2, Eric Schrauben4, Sameer Ansari3, Ali Shaibani3, Michael Markl2, Susanne Schnell2

1. Northwestern University McCormick School of Engineering – Department of Biomedical Engineering. 2. NorthwesternUniversity Feinberg School of Medicine – Department of Radiology. 3. Northwestern University Feinberg School of

Medicine – Department of Radiology, Neurosurgery, Neurology. 4. The Hospital for Sick Children, Toronto

Purpose: Cerebral arteriovenous malformation (AVM), an abnormal high-flow shunt between arteries and veins, exposes patients to complications including seizures and hemorrhagic stroke. Flow in these pathological connections is routinely assessed by invasive catheter digital subtraction angiography (DSA) but has been difficult to quantify with non-invasive techniques, due to the small, tortuous vessels of the AVM nidus. Recently, 4D flow MRI has been used to characterize the flow distribution of the highly connected vasculature around the nidus1,2. Previous analysis methods, however, used manually placed analysis planes, with time consuming analysis, limited reproducibility, and underutilization of 4D flow information. To address these limitations, we have developed a novel automated segmentation tool with integrated plane placement and minimal operator input. In a 4D flow MRI study of 10 AVM patients, we demonstrate identification of vessels feeding into and draining from the AVM nidus and characterize flow distribution between AVM and whole brain.

Methods: 10 AVM patients (mean age 40±11, 7 male) were scanned with 1.5T (Avanto) or 3T (Trio, Skyra) MRI (Siemens, Erlangen, Germany) using ECG-gated 4D flow sequence (TR/TE = 4.8/2.8 ms, flip angle 15°, venc = 100 cm/s, spatial resolution 1.36-1.79x1.09-1.31x1.4-1.8, 14-22 cardiac phases). Of these, 3 were re-scanned after each of 2 embolization stages. 4D flow data was pre-processed (phase offset, noise correction) and pseudo-complex difference angiograms (PCMRA) computed with an in-house tool. PCMRAs wereanalyzed with a new automated segmentation, centerline extraction and plane placement tool based on previous work3. Blood vessels were identified via PCMRA thresholding, skeletonized, then a centerline was found by quadratic spline interpolation. Analysis planes were placed using the spline derivative, and secondary region-growing refined segmentation at each plane. Flow rate [ml/s] at each cardiac phase and total flow [ml/cycle] were computed along left and right ICA, MCA, ACA, PCA, and transverse sinuses, basilar artery, superior sagittal and straight sinuses, and nearest branch to these arteries feeding or draining the AVM nidus.For each scan a mass balance was computed from these quantities across the brain (total outflow divided by total inflow: e.g. left ICA + right ICA + basilar artery divided by left + right transverse sinus), across the nidus (sum of draining veins divided by feeding arteries) and as fractional flow distribution (sum of draining veins divided by sum of brain inflow, sum of draining veins divided by sum of brain outflow). Paired two-tailed Student p-values were calculated for null hypotheses: inflow equals outflow acrossthe AVM nidus, across the whole brain, and across the AVM nidus as afraction of the whole brain, across time points (net flow) and across thecardiac cycle (flow/cycle). Factorial ANOVA characterized changes in flowdistribution between 1 feeding and 1 contralateral artery in each of 3 longitudinally followed subjects, where the feedingartery remained through embolization (analysis on individual plane measures of net flow per second and per cycle, with

feeding vs. contralateral status and embolization stage 0-2 as levels).

Results: An average 131±40 analysis planes per dataset were placed, as in Figure 1, with results for 10 unique subjects in Figure 2. While results varied between cases, indicated by standard deviation in mass balance across the AVM, there was no significant difference between inflow and outflow to the AVM and whole brainProportion of flow diverted to the AVM nidus was conserved between

for flow per cycle, but not net flow(potentially influenced by velocity noise in non-draining veins). Figure 3 shows the results of factorial ANOVA analysis of longitudinal data, with significant results to detectable within-subject using about 7 planes per vessel.

Discussion: These results demonstrate the feasibility of 4D Flow MRI segmentation and quantification in AVM using the described tool. The resulting flow network is self-consistent by conservation of mass and enables error analysis and longitudinal within-subject statistics for measurements. Future work includes further investigation of proportional flow through the AVM, characterization of whole-brain changes throughout embolization, anddetailed analysis of flow waveform transmission in the nidus. References:1. Ansari et al. Am J Neuroradiol 34:1922–28 (2013).2. Wu et al. Am J Neuroradiol 36:1142– 49 (2015).3. Schrauben et al. J Magn Res Imaging 42:1458–1464 (2015).



— Alex BarkerFeasibility of 4D-flow-based PCMRA Volumetry to Measure Longitudinal Ascending Aorta Growth

4D Flow PC-MRA to Measure Longitudinal Ascending Aorta Growth Alex Barker1, Ozair Rahman1, Jeremy Collins1, James Carr1, Michael Markl1,2

1Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, Il, USA 2Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA

Purpose: Patients predisposed to aortic pathology such as those with ascending or descending aortic dilatation require serial imaging to understand need or timing of intervention. Despite MRA being a recommended modality to monitor aortic growth, there is no standardized methodology for diameter measurements.1 Among many confounders, measurements are affected by plane angulation, ECG- and respiration-gating, the method of sinus measurement, or the unintentional omission of focal aortic growth regions. Thus, reproducibility among users is limited when tracking subtle changes of thoracic aorta aneurysms. In an effort to mitigate these errors, volumetry of contrast enhanced (CE)-MRA images was found more sensitive and reliable than diameter measurements to detect ascending aortic growth.2 Given a potential relationship of aortic growth with valve disease-mediated blood flow, 4D flow MRI may prove a useful complementary tool; however, it is difficult to regionally co-register with CE-MRA exams and thus assess flow-mediated growth. Here, we investigate if aorta growth can be measured in both bicuspid (BAV) and tricuspid aortic valve (TAV) patients undergoing longitudinal surveillance for ascending aortic dilation using phase-contrast (PC)-MRA images derived using 4D flow MRI. Methods: A retrospective, IRB approved and HIPAA compliant study was conducted to enroll all patients who underwent MRI surveillance over a period greater than 2 years. Inclusion criteria required both a FLASH-based CE-MRA sequence carried out during intravenous injection of 0.2 mmol/kg of gadolinium-DTPA (Magnevist; Bayer) and a 3D time-resolved phase-contrast gradient-echo sequence with three-directional velocity encoding (4D Flow MRI). All exams were performed at 1.5T (Avanto, Siemens). Scan parameters are shown in Fig.1. 45 BAV patients (48.2±12 years old, 29% female), and 17 TAV patients (54.6±16.5, 18% female) were identified. In addition, 9 volunteers were scanned at a year interval to understand the stability of the measurement. PC-MRA images were computed as described previously.3 An independent observer measured the diameter at the mid ascending aorta (MAA) and sinus of Valsalva (SOV) using the CE-MRA data and Vitrea (Vital Images). PC-MRA volumes were measured between the aortic valve annulus and innominate branch using Mimics (Materialise) (Fig. 1). All data is presented as mean±SD. Two sided, paired Student’s t-test was calculated to detect longitudinal differences; p<0.05 was considered statistically significant. Results: The mean time between baseline and follow up was 2.7±0.6 years for the BAV patients, 2.8±0.5 years for the TAV patients, and 1.1±0.5 years for the volunteers. No significant difference for diameter or volume was found for the volunteers during follow up (p>0.05). Follow up diameters and aortic volume were significantly greater than baseline volume for both BAV and TAV (Fig. 2, P<0.05). MAA and SOV diameters had significant growth in BAV patients and TAV patients, while growth was equally as significant or more significant when examining the volumetric measurements. Discussion: No growth was found in volunteers over a 1-year period (both diameter and volume). Aortic volume growth was equivalent or more pronounced (as deemed by statistical significance) than diameter growth in BAV patients and TAV patients. It was previously demonstrated that CE-MRA volumetry may be more sensitive than diameter to size changes in the ascending aorta; however, 4D flow PC-MRA has a lower resolution than CE-MRA, thereby potentially lowering the sensitivity of the volume measurement. Based on these results, volumetry by PC-MRA may be equivalent to diameter measurements for quantifying differences in aortic dilation. Future work will include a comparison of the CE-MRA and PC-MRA measurements

Fig 1. (A-C) Multiplanar reformat of the CE-MRA diameter measurements for MAA and SOV. (D-E) Volumetry of the ascending aorta using PC-MRA data.

Fig 2. Growth measured by diameter (CE-MRA) and volume (PC-MRA) in dilated TAV and BAV patients over two-plus years.

References: [1] Asch, FM, et al. JACC Cardiovasc. Imaging, 2016. 9(3): p. 219-26. [2] Trinh, B, et al. Invest. Radiol., 2016; doi: 10.1097/RLI.0332. [3] Bock, J, et al. in ISMRM. 2007. Berlin, Germany.



— Thorsten BleyMRI Displays Mural Inflammatory Changes of Intracranial Arteries in Giant Cell Arteritis

MRI displays Mural Inflammatory Changes of Intracranial Arteries in Giant Cell Arteritis

Bley TA, Brekenfeld C, Holst B, Kaufmann-Buehler AK, Fiehler J, Siemonsen S

University Medical Center Würzburg, Germany University Medical Center Hamburg Eppendorf, Germany

Synopsis: Manifestation of GCA was believed to be restricted to extradural arteries (1). This study demonstrated mural contrast enhancement and thickening of intradural intracranial arteries similar to the findings in the extradural superficial temporal arteries in a subset of patients with biopsy proven GCA (2,3). The inflammatory process of the cranial arteries in GCA may therefore proceed across the dura and manifest in intracranial arteries despite their different architecture as compared to the extracranial arteries. Results of this study and a perspective of future research directed to isotropic MR imaging of mural changes in intracranial arteries with high spatial resolution will be presented.

Purpose To assess mural inflammatory changes of intracranial arteries in patients with biopsy proven GCA depicted byhigh resolution MRI.

Methods 28 patients with suspected GCA received 3.0 Tesla MRI utilizing a contrast enhanced fat saturated T1weighted spin echo sequence (TR/TE = 11/549ms, α = 150°, Matrix = 320x320, FOV = 200mm, thickness = 2mm). Two observers evaluated mural thickness and contrast enhancement of extra- and intracranial arteries independently.

Results 20 of the 28 patients had GCA, 9 of which biopsy proven. Mural inflammatory changes of the superficial temporal arteries were detected in 16 patients with GCA. Corresponding mural changes were seen in the intradural segment of the carotid artery in 10 patients, of the vertrebal artery in 8 patients and medial cerebral artery in 1 patient. 2 patients with GCA presented with cerebral infarct. No association to ischemic events was found.

Figure 1: MRI revealed mural inflammatory changes of the superficial temporal artery (1a) and intradural internal carotid arteries (1b) in a patient with GCA. No mural changes were seen in the healthy volunteer (2).

Discussion We observed mural inflammatory changes of the intradural internal carotid arteries in a substantial subgroup of patients with GCA who presented mural inflammation MR-signs of the extradural superficial temporal artery. On the other hand, MRI of the patients without GCA did not reveal any such finding. Intradural involvement did not seem to be associated with vessel occlusion or stenosis and cerebral infarction in the patients of this study.

References 1) Wilkinson IM, Russell RW. Arteries of the head and neck in giant cell arteritis: a pathological study to show

the pattern of arterial involvement. Arch Neurol 1972;27:378–91.2) Siemonsen S, Brekenfeld C, Holst B, Kaufmann-Buehler AK, Fiehler J, Bley TA. 3T MRI reveals extra- and

intracranial involvement in giant cell arteritis. Am J Neuroradiol 2015 Jan;36(1):91-7.3) Klink T, Geiger J, Both M, Ness T, Heinzelmann S, Reinhard M, Holl-Ulrich K, Duwendag D, Vaith P, Bley TA.

Giant cell arteritis: diagnostic accuracy of MR imaging of superficial cranial arteries in initial diagnosis-resultsfrom a multicenter trial. Radiology 2014 Dec;273(3):844-52.

Oral presentation is favored over poster presentation.



— Romain BourcierMRI Quantitative T2 Mapping on Thrombus to Predict Recanalization After Endovascular Treatment for Acute Anterior Ischemic Stroke

MRI quantitative T2* mapping on thrombus to predict recanalization after endovascular treatment for acute anterior ischemic stroke

Romain Bourcier 1 , Nicolas Brecheteau 1, Hubert Desal 1, Oliver Naggara 2, Jean-Michel Serfaty 3 1 Department of Neuroradiology, University Hospital of Nantes, France 2 Department of Neuroradiology, Saint Anne Hospital, Paris, France 3 Department of Cardiac Imaging, University Hospital of Nantes, France

Background: In anterior acute ischemic stroke (AAIS) treated with endovascular treatment (EVT), the susceptibility vessel sign (SVS+ or SVS-) is related to recanalization results (TICI 2b/3) and clinical outcome. However, a binary qualitative assessment of thrombus using SVS does not reflect its complex composition. Our aim was to assess whether a quantitative MRI marker, Thrombus-T2* relaxation time, may be assessable in clinical routine and may to predict early successful recanalization after EVT, defined as a TICI 2b/3 recanalization obtained in 2 attempts or less.

Material and methods: Thrombus-T2* relaxation time was prospectively obtained from consecutive AAIS patients treated by EVT (concomitant aspiration and stent retriever). Quantitative values were compared between early recanalization and late or unsucessfull recanalization.

Results: Thirty patients with AAIS were included and Thrombus- T2* relaxation time was obtained in all patients. Earlier TICI 2b/3 recanalization were obtained in 22 patients (73%) and was significantly associated with SVS+ (1/8 vs. 16/22, p=0.01) and a shorter Thombus-T2* relaxation time (meanSD, range: 257, 18-50 ms vs. 45 9, 35-60 ms, p<0,001).

Conclusion: A new quantitative MRI biomarker, the Thrombus-T2* relaxation time is assessable in clinical routine. In a preliminary study of 30 patients, a shorter Thombus-T2* relaxation time is related to earlier recanalization after EVT.

MR imaging showing left MCA SVS- occlusion. The mean T2* relaxation time (Thrombus-T2*) is measured at 25ms. Successful recanalization post-EVT in one attempt has been reached. A, GRE sequence show a SVS- occlusion (black arrow). B, TOF show an MCA occlusion (black arrow). C, Thrombus-T2* sequence show the clot (white arrow). D, Thrombus-T2* with maximal zoom and manual contouring.



— Nicholas BurrisInitial Experience with 4D-flow Imaging in Patients with Dissection of the Descending Thoracic Aorta

Initial Experience with 4D Flow Imaging in Patients with Dissection of the Descending Thoracic Aorta

Nicholas S Burris MD1, David Williams MD1, Bo Yang MD PhD2, Himanshu Patel MD2, C. Alberto Figueroa PhD3, Michael D Hope MD4

1University of Michigan, Radiology, 2University of Michigan, Cardiothoracic Surgery, 3University of Michigan, Biomedical Engineering and Vascular Surgery, 4University of California San Francisco, Radiology

Purpose: The false lumen (FL) of the descending thoracic aorta is prone to aneurysmal degeneration in the setting of type B dissection or residual dissection after surgical repair of type A dissection. Hemodynamic properties of the false lumen are the result of a complex interaction between a number of factors including including intimal tear characteristics (e.g., size, location, number) and mechanical properties of the intimal flap and aortic wall. Prior studies have identified partial thrombosis of the false lumen to be associated with increased mortality, likely due to obstructed re-entry pathways for blood flow, resulting in higher diastolic false lumen pressure.1 Other factors such as false lumen flow volume/velocity and flow eccentricy have been associated with growth.2 The purpose of this feasibility study was to describe anatomic and hemodynamic characteristics of the dissected descending thoracic aorta using time-resolved three-dimensional phase-contrast MRI (4D Flow).

Methods: Patients with type B aortic dissection (n=7) or repaired type A dissection (n=3; DeBakey type I) were prospectively enrolled and underwent 4D Flow MRI of the thoracic aorta after the administration of the MR blood pool contrast agent ferumoxytol (3 mg/kg). 4D Flow data was processed and analyzed using a cloud-based computing platform (Arterys Inc.). Flow volumes and velocities were measured at the location of the dominant entry tear and at several locations in the thoracic false lumen, with 3D MRA images used to measure anatomic characteristics such as maximal diameter and entry tear size. Clinical information, including history of progressive FL growth, was abstracted by chart review.

Results: Mean patient age was 51.9 ± 8.2 y, the majority were male (70%), and the minority had partial false lumen thrombosis (30%). The mean age of the dissection at imaging was (3.8 ± 3.0 years, range 0.4-8 y). The majority of patients with type B dissection had a history of progressive FL growth (5/7) whereas none of the repaired type A dissection patients had an enlarging FL. Maximal diameter in the descending aorta was higher in patients with progressive FL growth (53.6 ± 10.5 vs. 38.4± 3.0 mm, p=0.01). Among type B patients with proximal entry tear in the distal arch, the regurgitant flow fraction at the proximal entry tear was significantly higher among patients with history of FL growth (37.3 ± 10.2 vs. 4.5 ± 2.5%, p=0.02)(Figure). The degree of intimal flap displacement between end-systole and end-diastole was significantly lower in patients with history of progressive FL growth (1.0 ± 1.4 mm vs. 4.6 ± 2.7 mm, p=0.04). There were no differences in dominant entry tear size, FL flow eccentricity, or peak FL velocity at the distal arch or proximal entry tear between the growing and stable groups.

Discussion: Chronic aortic dissection has variable clinical course, with a significant proportion of patients requiring eventual open or endovascular treatment for aneurysmal degeneration of the false lumen; however, methods to predict the risk of FL enlargement are lacking. Our preliminary results demonstrate an association between growth and both an elevated regurgitant fraction at the proximal entry tear and a less mobile intimal flap. These findings are most likely due to a combination of restricted distal re-entry pathways and chronic stiffening of the aortic wall/flap resulting in elevated diastolic FL pressure. If these observations are confirmed by larger studies, 4D Flow MRI may provide important information about a patient’s individual risk of FL growth based on assessment of FL hemodynamics.

References: 1.) Tsai TT et al. New Engl J Med. 2007;357(4):329-359. 2.) Clough RE et al. J Vasc Surg. 2012 Apr;55(4):914-23.

Figure: Patient with type B dissection, history of FL enlargement and an elevated regurgitant faction at the entry tear.



— Nicholas BurrisEccentric Flow in the Ascending Aorta is Associated with Aortic Growth in Patients with Isolated Bicuspid Aortic Valve

Eccentric Flow in the Ascending Aorta is Associated with Aortic Growth in Patients with Isolated Bicuspid Aortic Valve

Harkimal Singh BS1, Jimmy C Lu MD2, Prachi P Agarwal MD1, Monica Sigovan PhD, Michael D Hope MD3, Nicholas S Burris MD1

1University of Michigan, Radiology,2 University of Michigan, Pediatric Cardiology, 3CREATIS Laboratory, University of Lyon ,4University of California San Francisco, Radiology

Purpose: Despite the strong association of eccentric blood flow patterns with ascending aortic dilation in cross-sectional studies of bicuspid aortic valve (BAV) patients, few studies have investigated the impact of eccentric blood flow on future aortic growth.1 A recent small study showed that systolic flow displacement, a measure of blood flow eccentricity, predicts future aortic growth rate; however, the patient population was heterogeneous and a majority of patients had co-morbid congenital heart disease, mainly coarctation.2 The purpose of this study was to investigate the association between baseline eccentric blood flow and future aortic growth in a population of young patients with isolated BAV and limited cardiovascular comorbidity.

Methods: Using a local cardiac magnetic resonance imaging (MRI) database, we retrospectively identified patients with isolated BAV who had baseline cardiac MRI studies that included 2D phase-contrast sequences (2D PC) in the ascending aorta, and also had two or more echocardiograms separated by a minimum of 1 year (used to determine growth). Patients with connective tissue disease, interval aortic valve replacement and off-axis 2D PC data were excluded. Given that both pediatric (<18 y/o, n=9) and adult (≥18 y/o, n=9) patients were included, ascending aortic growth was defined as an interval increase of ≥3 mm in adult patients or increase of ≥2 z-score in pediatric patients. Systolic flow displacement was measured using a research version of commercial flow analysis software (Medis, Netherlands).

Results: Among 18 patients [mean age: 20.4 ± 10.7 y (range 9-45), 56% male], the majority had RL fusion pattern (n=11 RL, n=7 RN). No patients had history of hypertension or atherosclerosis and the majority had either no/mild aortic stenosis (17/18) or insufficiency (14/18) at baseline. The mean interval between echocardiography studies was 4.0 ± 2.3 years. Baseline systolic flow displacement was significantly higher in patients who showed interval growth (n=9) compared to those with stable aortic dimensions (n=9) (0.15 ± 0.7 vs. 0.09 ± 0.03, p=0.03)(Figure). There were no significant differences in age, sex, BSA, valve fusion pattern, aortic stenosis severity, aortic insufficiency severity, anti-hypertensive medication use, or family history of aortic disease between the growing and stable groups.

Discussion: Among a group of young patients with isolated BAV and low rates of valve dysfunction, systolic flow displacement was found to be significantly higher at baseline among patients who demonstrated future ascending aortic growth, further supporting the role of eccentric flow in BAV aortopathy. Despite a small sample size, this study is the first to identify differences in baseline ascending aortic flow eccentricity between stable and growing patients in the absence of associated congenital abnormalities or other risk-factors for aortic dilation. Flow displacement is an easily measured parameter that can be derived from routine clinical 2D PC data and may aid in risk-stratifying BAV patients.

References: 1.) Hope MD et al. Radiology. 2010;255 (1):53-61. 2.) Detaint D et al. Heart. 2014;100(2):126-34. 3.) Burris NS et al. Investigative Radiology. 2014;49(10):635-9.

Figure: Systolic Flow Displacement Values by Growth Outcome



— Mariana BustamanteAutomated Cardiac Segmentation in 4D-flow MRI

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— Huijun ChenImaging Findings in Pulsatile Tinnitus Patients Using Black-blood MRI: a Retrospective Study

Imaging findings in pulsatile tinnitus patients using black-blood MRI: a retrospective study Yunduo Li1, Le He1, Xiangyu Cao2, Xianling Wang3, Shubin Chen4, Rui Li1, Chun Yuan1,5, Huijun Chen1

1. Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China. 2.Neurosurgery department of the general hospital of PLA, Beijing, China. 3. Xuanwu Hospital, Capital Medical University, Beijing, China. 4.

Department of Otolaryngology Head and Neck Surgery, Beijing Tongren Hospital, Capital Medical University, Beijing, China. 5. Department of Radiology, University of Washington, Seattle, Washington, United States.

PURPOSE: Pulsatile tinnitus (PT) accounts for 4% of all tinnitus patients1. Various causes, especially abnormalities of transverse- and sigmoid-sinus, were reported in previous studies2,3. Black-blood (BB) MRI is an emerging tool for characterization of vessel wall conditions and can be used for cerebral venous thrombosis imaging4. Thus, we aim to investigate and classify venous wall abnormalities using black-blood (BB) MRI among venous PT patients. METHODS: 31 consecutive patients with clinical diagnosed PT were included in this study. All subjects were approved by the local ethics committee and written informed consent were obtained. MR scans were performed on a 3T Philips scanner. DANTE-VISTA5,6 was used for evaluation of transverse- and sigmoid-sinus. Imaging parameters were: TR/TE = 800/19 ms, FOV = 200 x 180 x 50 mm3, acquired voxel size = 0.7 x 0.7 x 0.7 mm3. MR venography scan was also used in this study. Imaging parameters were: TR/TE = 22/4.6 ms, flip angle = 10°, FOV = 220 x 160 x 144 mm3, acquired voxel size = 0.9 x 1.2 x 1.6 mm3. Demographic data were collected for patients. Drainage dominance, defined by a 20% difference in the size of transverse sinuses, was investigated using MR venography, Readers interpreted BB images to identify venous stenosis, defined as a 30% reduction in caliber of the vessel, and other abnormalities. All BB images were exported to Philips workstation where curved multi-planar reconstructions were created. Statistical analysis was performed using MedCalc (MedCalc Software, Mariakerke, Belgium). RESULTS: Of 31 patients, 29 patients and 32 veins on symptomatic side were included in this study. Two cases were excluded because of the poor image quality. Table 1 shows that, drainage dominance (18/29, 62.1%) and stenosis (19/32, 62.5%) are two main characteristics of PT patients. Overall, 14 symptomatic sides are consistent with dominant side. We also found that, arachnoidal granulations (11/32, 34.4%) and congenital stenosis (8/32, 25.0%) are two causes of stenosis (Fig.1 shows examples). Other anomalies (mastoiditis (Fig.3), 2/32, 6.3%; double lumen (Fig.2b), 1/32, 3.1%; arterio-venous fistula (Fig.2a), 1/32, 3.1% and malformation, 1/32, 3.1%) were also observed in this study. DISCUSSION: In this study, we successfully imaged venous anomalies using BB imaging techniques among PT patients. Our study found a high PT prevalence of female to male, which is consistent with previous studies2. MR Venography showed a high prevalence in drainage dominance (18/29, 62.1%) of which most (14/18) were in the symptom side, further indicating that drainage dominance might be one marker of PT. Conventional techniques, such as DSA, CTA/V, or MRA/V, can only find the stenosis, while BB MR images can identify the reason of stenosis. We also found that arachnoidal granulations overgrowth was frequently observed, which should be an important cause of stenosis in transverse-sinus. In addition, anatomical anomalies, such as arterio-venous fistula and double-lumen, can cause stenosis. However, our study did not found obvious stenosis in 40% patients, indicating the bruit causing venous flow are not only caused by stenosis. Since mechanism of PT is complicated, there can be several possible causes occurring at the same time, as shown in Fig.2b and Fig.3. More importantly, differentiate those sources of tinnitus using BB imaging technique is essential for treatment selection. For example, knowing the double lumen condition could help the surgeon a lot in stenting. In conclusion, our study showed that BB imaging has the potential to provide more pathological information and guide surgical treatment of PT, which is of great clinical value. REFERENCES: 1. Lockwood AH, et al. N Engl J Med 347(12):904–10. 2.Stephen S, et al. Otolaryngol Head Neck Surg 150(5): 841–6. 3.Zhao P, et al. Eur Radiol (2016) 26:9–14. 4.Yang Q, et al. Stroke, In Press. 5.Wang J, et al. Magn Reson Med (2016) 75:831-38. 6.Viessmann O, et al. Magn Reson Med, In Press.

Table 1. Demographics and imaging findings ofPT patients (29 patients, 32 ears)

Fig.1 Two PT patients with stenosis. (a) No drainage dominance. (b) Expanded arachnoidal granulations (dashed box). (c) Right-side drainage dominance and collaterals (white arrow heads). (d) Congenital stenosis (yellow arrow heads) in transverse-sinus.

Fig.3 Patient with left ear PT. (a) Right-side drainage dominance. (b) Mastoiditis (arrow head) and expanded arachnoidal granulations (dashed box) on left side.

Fig.2 Two patients with right ear PT. (a) Arterio-venous fistula (white dashed box), (b) Double-lumen (white dashed cicle) and arachnoidal granulations overgrowth (yellow arrow head).



— Jeremy CollinsPredicting Hepatocellular Carcinoma Treatment Response to Yittrium-90 Radioembolization by Quantitative Perfusion Using Contrast-enhanced Magnetic Resonance Angiography with Echo Sharing and Radial K-space Sampling



— Ryan DolanRole of Structure-function Cardiac MRI in the Detection of Acute Cardiac Allograft Rejection after Heart Transplantation

Role of Structure-Function Cardiac MRI in the Detection of Acute Cardiac Allograft Rejection after Heart Transplantation

Ryan Dolan MD1, Amir Rahsepar MD1, Julie Blaisdell1, Kenichiro Suwa MD1, Kambiz Ghafourian MD,MPH2, Jane Wilcox MD2, Sadiya Khan MD,MSc2, Esther Vorovich MD2, Jonathan Rich MD2, Allen Anderson MD2,

Clyde Yancy MD2, Jeremy Collins MD1, Michael Markl PhD1,3, James Carr MD1 1Dept of Radiology, 2Dept of Cardiology, 3Dept of Biomedical Engineering,

Northwestern University, Chicago IL, USA Purpose: Cardiac MRI (CMR) is gaining use as a non-invasive surveillance tool for acute cardiac allograft rejection (ACAR) following heart transplantation (Tx). ACAR can be cell-mediated (ACR) or antibody-mediated (AMR). The majority of CMR research in Tx recipients has focused on demonstrating that T2 increases during active ACR [1-3], but little research has been devoted to other CMR parameters (T1, extracellular volume fraction (ECV), myocardial velocities). In addition, the role of ACAR history on CMR parameters and CMR differences between ACR and AMR are not well understood. The goal of this study was to apply comprehensive structure-function CMR (T2, T1, ECV, tissue phase mapping (TPM)-derived tri-directional myocardial velocities) to test the hypotheses that T2, T1, ECV, and myocardial velocities will differ 1) between healthy controls and Tx recipients without history of ACAR, 2) between Tx recipients with and without past or active evidence of ACAR, and 3) between Tx recipients based on history of ACR and AMR.

Methods: CMR at 1.5T (Aera/Avanto, Siemens, Erlangen, Germany) was performed prospectively on 91 Tx recipients (50.8±17.6 yrs, 42% female) and 14 controls (47.7±16.7 yrs, 36% female) for 160 total CMRs (Figure 1). Studies were stratified into four cohorts (based on myocardial biopsy grade): Controls (N=14), No ACAR (no history of ACAR, N=81), Past ACAR (history of ACR or AMR prior to MRI, N=43), ACAR+ (active grade≥1R ACR or grade≥pAMR1 AMR at time of CMR, N=22). Separately, studies of patients with history of AMR (N=13, all had history of ACR as well) were compared to studies of patients with only history of ACR (N=26). Structure-function CMR included T2-mapping, pre- and post- contrast T1-mapping (to calculate ECV), and TPM in short-axis orientation (base, mid, apex) of the left ventricle (LV). Data analysis included delineation of endo- and epi-cardial contours and calculation of regional (AHA 16-segment model) and global (average over entire LV) myocardial T2, native T1, and ECV. TPM data was used to derive peak systolic and diastolic radial and longitudinal LV velocities.

Results: Comparisons of CMR parameters between the four cohorts are summarized in Table 1. T2 was significantly elevated in patients with Past ACAR compared to No ACAR (51.6±4.1 ms vs. 49.4±3.2 ms, P<0.01) and in No ACAR patients compared to controls (49.4±3.2 ms vs. 45.2±2.3 ms, P<0.01). ACAR+ patients demonstrated increased T2 compared to the No ACAR group (52.8±4.8 ms vs. 49.4±3.2 ms, P<0.01), but not compared to the Past ACAR group. T1 was significantly higher in ACAR+ patients compared to No ACAR patients (1067.7±78.5 ms vs. 1027.3±47.5 ms, P<0.01). ECV was significantly elevated in ACAR+ patients compared to recipients without ACAR (31.2±3.7% vs. 26.9±3.3%, P<0.01) regardless of history of ACAR (No ACAR and Past ACAR). TPM identified lower peak systolic longitudinal velocities and higher peak diastolic radial velocities in No ACAR patients compared to controls (2.8±1.0 cm/s vs. 4.9±1.1 cm/s, P<0.01; -3.7±0.9 cm/s vs. -2.9±0.7 cm/s, P<0.01). Patients with Hx of AMR demonstrated increased T1 compared to patients with history of ACR only (1097.2±38.3 ms vs. 1030.4±55.5 ms, P<0.01), but there were no significant differences in T2 or ECV.

Discussion: CMR parameters were sensitive to structural and functional change in Tx recipients. T2, T1, and ECV were significantly elevated during episodes of active ACAR, showing promise of multiparametric CMR for detection of ACAR. T2 and ECV demonstrated similar elevation with both ACR and AMR, but T1 increased more with history of AMR than with ACR alone.

References: [1] Marie et al. J Am Coll Cardiol. 2001. [2] Usman et al. Circ Cardiovasc Imaging. 2012. [3] Butler et al. J Cardiovasc Magn Reson. 2009. Acknowledgements: Grant support by NHLBI R01 HL117888.

Table 1: Comparison of CMR parameters between four cohorts (1. Controls, 2. No ACAR, 3. Past ACAR, 4. ACAR+). Significant differences between cohorts are found on right. PV: peak velocity, Rad: radial, Long: longitudinal, Sys: systole, Dia: diastole.

P 1&2 2&3 2&4 3&4Global T2 45.2 ±2.3 49.4 ±3.2 51.6 ±4.1 52.8 ±4.8 <0.01 x x xGlobal T1 993.8 ±34.1 1027.3 ±47.5 1046.8 ±53.3 1067.7 ±78.5 <0.01 xGlobal ECV 25.9 ±2.7 26.6 ±3.1 27.4 ±3.8 31.2 ±3.7 <0.01 x xPV Rad Sys 2.7 ±0.4 2.6 ±0.4 2.5 ±0.5 2.6 ±0.5 0.77PV Rad Dia -2.9 ±0.7 -3.7 ±0.9 -3.9 ±1.0 -3.7 ±1.0 0.01 xPV Long Sys 4.9 ±1.1 2.8 ±1.0 2.9 ±1.1 2.5 ±0.9 <0.01 xPV Long Dia -3.5 ±1.4 -2.9 ±1.1 -3.3 ±1.3 -3.0 ±1.0 0.22

1. Controls (N=14) 2. No ACAR (N=81) 3. Past ACAR (N=43) 4. ACAR+ (N=22)

Figure 1: Schematic diagram of study design.



— Charles DumoulinA Novel Approach to Reduce Scan Times with Simultaneous QFlow & bSSFP Imaging within the Same Breath Hold

A novel approach to reduce scan times with simultaneous QFlow & bSSFP imaging within the same breath hold

Matthew Lanier1, Ryan Moore2, Michael Taylor2, Charles Dumoulin1, and Hui Wang3

1Radiology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States, 2Cardiology, Cincinnati Children’s Hospital Center, Cincinnati, OH, United States, 3Philips, Cincinnati, OH, United States

PurposeCardiac Magnetic Resonance (CMR) provides excellent diagnostic imaging of congenital heart defects, cardiomyopathy, valve disease, and coronary artery disease. Cardiac Phase-Contrast MRI (PC-MRI) is a non-invasive method for evaluating cardiopulmonary hemodynamics (ref 1, 2) during cardiac MRI. PC-MRI is typically implemented as a spoiled gradient echo sequence. Consequently, the delineation of the vessel wall can be poor, when compared to a bSFFP sequence. We propose a novel method to reduceacquisition time and improve visualization of flow near the vessel wall with a sequentially acquired QFlow and bSSFP cine sequences as shown in fig1. Acquiring QFlow and bSSFP cine images in a single breath hold eliminates the need to have scans acquired in separate breath holds.

MethodsAll imaging was performed on a Philips 1.5T Ingenia™ using anterior and posterior phased array coils. “Multiple Instantaneous Switching between Scans” (MISS) (ref3 and 4), was used to interleave QFlow and bSSFP cine acquisitions within the same breath hold as shown in fig2. Cardiac synchronization was obtained with vector cardiographic (VCG) gating. Seven healthy volunteers were imaged for this feasibility study. For the QFlow sequence, the scan parameters were as follows: TR=4.1ms, TE=2.5ms,FA=120, FOV=200-300x200-300mm, in plane resolution=2.5x2.5mm, slice thickness=8mm, SENSE factor=2, and VENC=200cm/s. For the bSSFP cine sequences, the scan parameters were as follows:TR=2.4-2.7ms, TE=1.2-1.4ms, FA=600, FOV 200-300x200-300mm, in plane resolution 2x2mm, slice thickness=6mm, and SENSE factor=2. Both sequences used retrospective gating and 30 cardiac phases were reconstructed. QFlow and bSSFP sequences were acquired across the ascending and descending aorta. bSSFP was acquired first for a period of 3-5 seconds, and the QFlow sequence was acquiredimmediately afterward for 10 seconds. The entire breath hold duration was 13-15 seconds.

fig1 fig2ResultsIn all subjects, the combined QFlow and bSSFP cine approaches were acquired successfully in a single breath hold. Acquiring both QFlow and bSSFP images in the same breath hold kept the image geometry the same for both sequences, obviating the need for registration of the images. Since the bSSFP cine and QFlow sequences were set to the same number of cardiac phases, no phase adjustments needed to be applied to the data.DiscussionWe have demonstrated the feasibility of a combined multi-sequence acquisition improving the visualization of vessel walls and contour accuracy. This approach not only halved the number of breath holds from n=2 (1xcine + 1xQflow) to n=1 (combined), it kept the image geometry the same without inter-breath hold motion. The next step is to further optimize the protocol to shorten the breath hold times, and apply this technique on patients. AcknowledgementsWe would like to thank Jouke Smink and David Higgins of Philips for providing technical advice.References[1] – Lotz et al. Radiographics 2002, 22(3):651-71. [2] – Gatehouse et al. Eur Radiology 2005. [3] –Henningsson et al. MRM 2015, 73(2):692-6240



— Tora DunåsAutomatic Blood Flow Measurements in 4D-flow MRI

Automatic blood flow measurements in 4D flow MRITora Dunås1, AndersWåhlin1,2, Laleh Zarrinkoob4, Jan Malm4 and Anders Eklund1,2,3

1. Department of Radiation Sciences, Umeå University, 2. Umeå Center for Functional Brain Imaging, Umeå University, 3. Centre forBiomedical Engineering and Physics, Umeå University, 4. Department of Pharmacology and Clinical Neuroscience, Umeå University

Purpose: Automatic measurements of blood flow rate in cerebral arteries makes it possible to conduct standardize analyses on large cohorts. Standardized flow calculations in a large number of arteries give a new possibility to evaluate collateral circulation. The aim of this study was to add flow quantification capability to an automatic arterial identification method for 4D flow MRI [1], [2], and to validate flow rate results to corresponding manual measurements.

Methods: 4D flow MRI was collected on a 3T GE Discovery MR 750 scanner with a 32-channel head coil. Imaging parameters: 16000 radial spokes, imaging volume, 220 × 220 × 220 mm; reconstruction matrix size, 320 × 320 × 320 (zero padded interpolation); voxel size 0.7 × 0.7 × 0.7 mm3. Scan time was ~9 min; velocity encoding, 110 cm/s; TR/TE, 6.5/2.7 ms; flip angle, 8°; bandwidth, 166.67 kHz.

Ten patients with carotid artery stenosis were included (9 men, 72.9 ± 6.9 years). In each patient, nine arteries were investigated; basilar artery (BA) bilateral internal carotid arteries (ICA), middle cerebral arteries (MCA), posterior cerebral arteries (PCA) and anterior cerebral arteries (ACA) (Fig. 1).

The manual measurements were done by scrolling through axial images and selecting the artery of interest. A three voxels thick plane through the point, perpendicular to the direction of flow, was calculated and used for measurements. Vessels were separated from background by thresholding at ten percent of the maximum value in the angiographic image. Flow rate was calculated by summing all velocity values within the plane and multiplying with pixel area divided by slice thickness [3].

For each artery, regions of interests were defined in a stereotactic atlas [4]. The middle point of each identified segment was used to calculate flow, in the same way as for the manual measurements.

Manual measurements were obtained for 87 arteries (three ACA were anatomically missing). Out of those, 83 arteries (95%) was correctly identified by the automatic method and used for flow validation.

Results: No significant difference was found between the methods (p=0.38 with paired t-test, mean difference 1.2 ml/min, standard deviation 12.3 ml/min, see correlation plot in Fig. 2).

Discussion: The automatic flow measurements agreed with manual measures. The difference in flow values can only result from difference in location of the flow measurement in the vessel since the same method is used to calculate the perpendicular plane, segment the vessel from the background, and calculate flow. This pilot study shows that automatic flow assessment of the large cerebral arteries is feasible and does result in flow values close to those obtained by manual measures.

References

[1] T. Dunås, A. Wåhlin, K. Ambarki, L. Zarrinkoob, R. Birgander, J. Malm, and A. Eklund, “Automatic labeling of cerebral arteriesin magnetic resonance angiography,” Magn Reson Mater Phy, vol. 29, no. 1, pp. 39–47, 2016.

[2] T. Gu, F. R. Korosec, W. F. Block, S. B. Fain, Q. Turk, D. Lum, Y. Zhou, T. M. Grist, V. Haughton, and C. A. Mistretta, “PCVIPR: a high-speed 3D phase-contrast method for flow quantification and high-resolution angiography.,” Am. J. Neuroradiol.,vol. 26, no. 4, pp. 743–9, Apr. 2005.

[3] A. Wåhlin, K. Ambarki, R. Birgander, O. Wieben, K. M. Johnson, J. Malm, and A. Eklund, “Measuring Pulsatile Flow in CerebralArteries Using 4D Phase-Contrast MR Imaging.,” Am. J. Neuroradiol., vol. 34, pp. 1740–1745, 2013.

[4] T. Dunås, A. Wåhlin, K. Ambarki, L. Zarrinkoob, J. Malm, and A. Eklund, “A Stereotactic Probabilistic Atlas for the MajorCerebral Arteries,” Neuroinformatics, vol. 15, no. 1, pp. 101–110, 2017.

Fig 1. Results from automatic labeling in one subject

Fig 2. Correlation between automatic and manual measurements



— Robert EdelmanBreath-hold Coronary MRA at 3 Tesla Using Fast Interrupted Steady-state

Breath-hold Coronary MRA at 3 Tesla using Fast Interrupted Steady-State Robert R. Edelman1,2, Ioannis Koktzoglou1,3

1Radiology, NorthShore University HealthSystem, Evanston, Illinois, United States, 2Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States, 3Radiology, Pritzker School

of Medicine, University of Chicago, Chicago, Illinois, United States

Purpose: Current efforts for coronary MRA are generally directed towards free-breathing, motion-compensated 3D techniques with scan times of at least several minutes. Alternatively, one can image during a breath-hold using quiescent-interval slice-selective (QISS) MRA with a radial balanced steady-state free precession (bSSFP) readout [1]. However, the use of a radial bSSFP readout is not ideal for several reasons, including difficulty in obtaining uniform fat suppression and artifacts from through-plane flow. Another breath-hold technique, cine bSSFP, is in widespread use for multi-phase evaluation of the heart but is not helpful for coronary imaging. With cine bSSFP, high signal from epicardial fat and chemical shift artifact impair coronary conspicuity. To overcome these limitations, we implemented a radial fast interrupted steady-state (FISS) readout [2,3] for both QISS and cine acquisitions. Methods: Imaging was performed in healthy volunteers at 3 Tesla (Skyra Fit, Siemens Healthcare, Erlangen, Germany) using a body phased array coil. Each radial FISS module consisted of a series of 3 to 6 bSSFP readouts sandwiched between a pair of alpha/2 RF pulses. Gradient and RF spoiling were applied between modules. The excitation flip angle was ~70 degrees, slice thickness ~1.5 to 3 mm, in-plane resolution ~ 1.0 to 1.6 mm before interpolation, equidistant azimuthal view angles, 1 to 4 shots (i.e. number of heartbeats) per slice, fat suppression (for QISS only) using a chemical shift-selective RF pulse. Results: Approximately 5 to 20 QISS slices could be acquired in each breath-hold depending on the number of shots. Comparing FISS and bSSFP readouts, the FISS readout provided substantially better epicardial and subcutaneous fat suppression, as well as more uniform intravascular and intra-cardiac signal with less through-plane flow artifact than a bSSFP readout (Fig. 1).

Figure 1: A) Breath-hold radial QISS FISS showing the LAD and RCA. Vascular signal appears homogeneous, while fat appears uniformly dark. B) Two frames from a multi-phase cine acquisition. Top row: FISS, bottom row: bSSFP. Suppression of the epicardial fat signal with FISS greatly improves LAD conspicuity.

Discussion: Using a FISS readout for QISS and cine acquisitions can provide substantial benefits for breath-

hold imaging of the coronary arteries, and for cardiac imaging more generally. First, compared with bSSFP, the suppression of epicardial fat signal enhances the conspicuity of the coronary artery lumen, while the suppression of subcutaneous fat signal reduces streak artifacts from the use of high radial undersampling factors. Second, the gradient and RF spoiling that are applied between FISS modules suppress steady-state magnetization from out-of-slice spins as well as strongly oscillating signals from off-resonant spins in the transient-state that occur using a bSSFP readout. The main drawback of FISS is slightly reduced imaging efficiency. Based on these initial results, clinical evaluation appears warranted.

References: [1] Edelman RR, et al. JCMR 2015 Nov 23; 17:101. [2] Derbyshire JA, et al. MRM 2005; 54:918. [3] Koktzoglou I, Edelman RR. Proc. of 25th Annual Meeting of ISMRM, Honolulu, 3959; 2017. Funding: NIH grants R01 HL130093 and R21 HL126015.



— Robert EdelmanUngated, Free-breathing, “No Hassle” Imaging Strategy for Nonenhanced Peripheral MR Angiography at 3 Tesla

Ungated, Free-Breathing, “No Hassle” Imaging Strategy for Nonenhanced Peripheral MR Angiography at 3 Tesla

Robert R. Edelman1,2, Shivraman Giri3, Ioannis Koktzoglou1,4 1Radiology, NorthShore University HealthSystem, Evanston, Illinois, United States, 2Radiology, Feinberg School of

Medicine, Northwestern University, Chicago, Illinois, United States, 3Siemens Healthcare, Chicago, Illinois, 4Radiology, Pritzker School of Medicine, University of Chicago, Chicago, Illinois

Purpose: Nonenhanced MRA techniques provide a useful, risk-free alternative to CTA and contrast-enhanced MRA. Existing approaches such as quiescent-interval slice-selective (QISS) MRA and fresh blood imaging (FBI) typically use ECG gating, which increases patient set-up time and can be unreliable at 3 Tesla due to magneto-hydrodynamic interference or cardiac arrhythmias. Free-breathing FBI scans of the pelvis and abdomen are susceptible to motion artifact, whereas the use of multiple breath-holds with QISS can be tiring. The goal of this study was to develop a simple-to-use, “no hassle” strategy for nonenhanced peripheral MRA that eliminates the need for ECG gating or breath-holding, while maximizing patient comfort and exam simplicity. Methods: Imaging was performed in volunteers and patients at 3 Tesla (Skyra Fit, Siemens Healthcare, Erlangen, Germany). A prototype single-shot radial QISS pulse sequence was modified to allow the use of a balanced steady-state free precession (bSSFP), fast interrupted steady-state (FISS) [1], or FLASH readout. Each FISS module consisted of a series of three bSSFP readouts sandwiched between a pair of alpha/2 RF pulses. Differences from ECG-gated QISS included the use of a radial instead of Cartesian k-space trajectory, equidistant azimuthal view angles, in-plane and tracking inversion pulses rather than saturation pulses, a longer TI (~1800 msec,) and more

views (147 for the legs, 441 in the pelvis). A single-shot readout was used for the legs and 3 shots for the pelvis and abdomen. 40 3-mm thick slices were acquired for each table position with 1-mm in-plane spatial resolution before interpolation. All sequences used fat suppression. The FLASH readout used an out-of-phase TE (3.69 msec) and flow compensation. Results: Excellent image quality with uniform fat suppression and intravascular signal was obtained in the legs using ungated QISS (UnQISS) with a FISS readout (Fig. 1), whereas the use of a bSSFP readout resulted in horizontal striping artifacts within the arteries as well as inferior fat suppression. UnQISS using a FLASH readout resulted in the best image quality in the abdomen and pelvis, but showed fewer branch vessels than a FISS readout in the legs. Respiratory motion artifacts were effectively suppressed with a 3-shot radial readout.

Discussion: We have demonstrated the feasibility of a simple-to-use, easily tolerated approach for nonenhanced peripheral MRA at 3 Tesla. It avoids the use of ECG leads or breath-holding, while eliminating any need for patient-specific changes in imaging parameters or the acquisition of scout images. Based on initial studies, an optimal approach may consist of UnQISS FISS in the legs and UnQISS FLASH in the pelvis and abdomen. References: [1] Koktzoglou I, Edelman RR. Proceedings of the 25th Annual Meeting of the ISMRM, Honolulu, 3959; 2017. Funding: NIH grants R01 HL130093 and R21 HL126015.



— Laura EisenmengerMRI Compatible Animal Model of Vessel Wall Imaging Using a T1-weighted Black Blood Technique and DCE MRI

MRI compatible animal model of vessel wall imaging using a T1-weighted black blood technique and DCE MRI

Authors: LB Eisenmenger, SE Kim, EJ Huo, J Mendes, EK Morton, DL Parker, JS McNally

Purpose: Development of an MRI-compatible animal model of vessel wall enhancement will allow testing of novel therapeutics against endothelial dysfunction and vessel wall pathology prior to clinical trials. Our goal is to use the rat sepsis model and 7T vessel wall MRI to detect vessel wall enhancement and characterize contrast leakage kinetics.

Methods: Two-month-old male Sprague Dawley rats were divided into control and lipopolysaccharide (LPS)-injected rats (10 mg/kg) using a previously established rat sepsis protocol. Rats were then imaged on a Bruker 7T MRI with 3D T1-weighted Rapid Acquisition with Relaxation Enhancement (RARE) sequence with black blood technique to evaluate vessel wall enhancement. Black blood images were obtained at 1hr, 4hrs, 8hrs, 24hrs, and 48hrs after LPS injection. At the same time points, dynamic-contrast enhanced (DCE) was obtained to detect changes in contrast transfer kinetics by calculating Ktrans using OleaSphere 3.0.

Results: Black blood MRI demonstrated progressive enhancement along the vessel wall of the bilateral intracranial internal carotid arteries after LPS injection, and this was most evident at 24 hours. Delayed contrast enhancement was imaged using a 3D T1-weighted RARE MR black blood technique. There was no enhancement along the intracranial vessel walls in the 0 hour controls, A. and C. (magnification view), but avid enhancement was seen after LPS injection at the 24 hour timepoints, B. and D. (magnification view). Similarly, DCE images showed elevated Ktrans after LPS treatment after 24 hours compared to 0 hour controls (mean±SD= 0.42±0.01 versus 0.08±0.07 min-1, p=0.003). Representative 0 hour animals are shown in F. and H. (magnification view) and 24 hour animals are shown in G. and I. (magnification view). In these representative animals, Ktrans values were higher at 24 hours (0.42 min-1) compared to the control (0.06min-1).

Discussion: 7T black blood and DCE MRI sequences may be used to detect and characterize early events in endothelial dysfunction with the small animal rat sepsis model. This model can be used to identify new therapies and assess mitigation of endothelial dysfunction non-invasively, with high potential for clinical impact.



— Zhaoyang FanQuantitatively Monitoring Regression or Progression in Intracranial Atherosclerotic Plaques Using 3D Vessel Wall Imaging

Quantitatively Monitoring Regression or Progression in Intracranial Atherosclerotic Plaques Using 3D Vessel Wall Imaging

Zhaoyang Fan1, Qi Yang1, Xiuhai Guo2, Feng Shi1, Yujiao Yang2, Shlee Song1, Nestor Gonzalez1, Marcel Maya1, Debiao Li1

Cedars-Sinai Medical Center, Los Angeles, CA, USA; Xuanwu Hospital, Beijing, China.

Purpose: Intracranial atherosclerotic disease (ICAD) is one of the most common causes of ischemic stroke worldwide [1]. Despite aggressive medical management, the rate of recurrent stroke is 13% at 1 year [2]. A tool that can directly probe atherosclerotic plaques and accurately quantify longitudinal changes of plaque features may help early identify non-responsive patients in whom an alternative therapy can be initiated. Intracranial vessel wall imaging (VWI) is a noninvasive, “looking-beyond-the-lumen” imaging method that can directly characterize the geometric and signal features of ICAD lesions. In the present work, we sought to assess the feasibility of quantitatively monitoring regression or progression of intracranial atherosclerotic plaques using 3D VWI. Methods: Six patients (1F, 5M; age 27-66 years) with ischemic stroke secondary to ICAD were recruited for this feasibility study. All subjects were treated with intensive medical therapy including statin. Initial and follow-up MR examinations were performed within 8 weeks of symptoms and at 5-9 months, respectively. The MR protocol consisted of 3D TOF-MRA, pre-contrast 3D VWI, and post-contrast 3D VWI. A recently developed CSF-suppressed whole-brain VWI was used to acquire 3D VWI images with isotropic 0.5-mm spatial resolution and an 8-min scan time [3,4]. Images were randomized and reviewed by two neuroradiologists to determine the culprit lesion in each subject. A custom-designed intracranial vessel analysis (IVA) software package [5] was used to quantitatively measure the geometric and signal features of the culprit lesion, including peak normalized wall index (NWI), plaque volume, pre-contrast plaque-wall contrast ratio (CR) (defined as SIplaque/SIwall), and plaque enhancement ratio (ER) (defined as [SIplaque/SIgraymatter]post/[SIplaque/SIgraymatter]pre). Results: No subjects except for Subject #5 had a recurrent stroke during the period. Quality of 3D VWI in all subjects was good for visualization and quantification. The quantitative plaque features derived by IVA exhibited different change patterns over the treatment period as shown in Figure 1. Subject #1 and #5 demonstrated an increase in plaque ER, plaque volume, and peak NWI, whereas others had a decrease or no change in these features. The burden of the culprit lesions in the two subjects became larger as visually determined by neuroradiologists.

Discussion: In this work, an increase in plaque ER, volume, and peak NWI of culprit lesions appeared positively correlated with stroke recurrence. Plaque ER has been shown to be associated with culprit lesions. Enhanced plaque ER may suggest a more active inflammatory status. Enlarged plaque volume and peak NWI are clearly markers of a growing plaque. Hence, our results suggest that temporal changes in these features may have a strong indication on culprit lesions’ response to medical therapy. A large-scale clinical validation is warranted. References: [1] Gorelick PB et al. Stroke 2008;39:2396-2399. [2] Derdeyn CP Lancet 2014;383:333-341. [3] Fan et al. MRM 2017;77:1142-1150. [4] Yang et al. JMRI. [5] Shi F et al. ISMRM 2017; 4706.

Figure 1. In six subjects on intensive medical therapy due to ischemic stroke, quantitative plaque features demonstrated different change patterns over the period of 5-9 months. Only subject #5 had a recurrent stroke duringthe period. MR images shown are his post-contrast VWI ofhis culprit lesion at two time points along with pre- andpost-contrast cross-section images.



— Farshid FarajiEffect of Reference Vessel Selection on an Image Processing Pipeline for the Longitudinal Surveillance of Intracranial Aneurysms

Effect of Reference Vessel Selection on an Image Processing Pipeline for the Longitudinal Surveillance of Intracranial Aneurysms Farshid Faraji, Evan Kao, Florent Seguro, Cecilia Huang, David Saloner

Department of Radiology, University of California San Francisco; Vascular Imaging Research Center, San Francisco Veterans Affairs Medical Center

PURPOSE We have previously described a method of evaluating longitudinal changes in aneurysm volume that provides consistent signal intensity calibration by constraining the estimated volume of a healthy vessel segment to remain unchanged over time. Intensity-based threshold values are adjusted between serial studies such that the volume of the reference segment is held within 2% across all studies. Using these study-specific intensity thresholds, a systematic longitudinal comparison of aneurysm volumes is possible. The purpose of the current study is to evaluate the sensitivity of this methodology to three characteristics of the user-selected reference vessel: its size, location, and baseline threshold. The impact of these user-dependent choices on the generation of the reference vessel were measured on a distal “target” vessel (one that would otherwise be expected to remain unchanged over serial studies).

METHODS CE-MRA was acquired for 10 intracranial aneurysm patients, each with at least 4 imaging time points. All images were acquired on a 1.5T Philips Intera (Philips Medical Systems, Best, Netherlands), using an elliptic-centric K-space reordering schema. Primary imaging parameters were as follows: TE/TR/flip angle = 2ms/5ms/30°. Images had an acquired resolution of 0.6 x 0.63 x 1.2 mm3 interpolated to 0.47 x 0.47 x 0.6 mm3. The total acquisition time was 30s. Each patient received 20mL of Gd with contrast injection timed to maximize concentration in the intracranial arterial circulation during the acquisition of the center of K-space.

Acquired DICOM images were exported to VTK format using an in-house software DICOM Toolbox. The VTK images were then transferred to another custom software package, ClemSTL, for iso-surface generation using intensity-based thresholding, with the threshold value selected to maximize intra-luminal signal while excluding any extra-luminal signal. Iso-surfaces for baseline and follow-up studies were imported into 3D modeling software GeoMagic (INUS Technology, Seoul, South Korea), and were co-registered to the baseline study using a picked-point, landmark-based registration. Once iso-surfaces from serial studies were aligned, reference vessels were segmented and the volumes of these surfaces recorded. Intensity thresholds were adjusted such that the reference vessel volume remained unchanged to within 2% across time points. The volume of the target segment was then measured using the corresponding threshold values.

Sensitivity to reference vessel characteristics was investigated as follows. The co-registration/segmentation pipeline was completed for all patients through all time points using a reference vessel of: 1) two different sizes [fig 1]; 2) two different locations [fig 2]; and 3) a range of baseline thresholds. In order to assess the sensitivity of the pipeline to these 3 characteristics, a coefficient of variation (CoV) metric was calculated by taking the standard deviation of target volume divided by the mean target volume. Baseline and follow-up DICOM images were imported into ParaView, and follow-up images were co-registered with the baseline study using the transformation matrix attained from GeoMagic’s picked-point registration. Once image data was aligned, the reference vessel was isolated across all time points using cut planes, and surfaces were extracted [fig 3]. Threshold values were varied to determine the Threshold/Volume relationship curves for the reference vessel at each time point [fig 4]. Threshold values were estimated at each time point to match reference volumes between studies, and volume of the target segment was noted at each of these corresponding threshold values [fig 5]. CoV was calculated for the target segment at various baseline threshold selections [fig 6].

RESULTS Paired T-tests show insignificant difference for CoV of target vessel volumes when comparing reference vessels of different location/size. We have noted an optimal baseline threshold selection that provides a minimum CoV value providing volume reproducibility to under 4%, however this metric appears to be relatively insensitive to baseline threshold selection.

Figure 4 Figure 5 Figure 6

DISCUSSION This analysis has demonstrated that the previously proposed reference vessel segment method provides estimates of aneurysm volumes that are robust. Specifically, the volume of the distal target vessel segment (which in practice would be the aneurysm) is little affected by the specific location or size of the selected reference vessel. Further analysis is warranted to better understand the relationship of size and location of reference vessels to the error in reproducibility of measurement of the target vessel segment. Additionally, future studies will seek to aid in the improvement of selecting the baseline imaging threshold values which will minimize coefficient of variation and thus the error in reproducibility of measurement across longitudinal studies.



— Sylvana García-RodríguezComparison of Contrast and Non-Contrast Phase Contrast Magnetic Resonance Angiography in Infants

Comparison of Contrast and Non-Contrast PC MRA in Infants Sylvana García-Rodríguez1, Alejandro Roldán-Alzate1,2,3, Mark L. Schiebler1, Christopher J. François1

1Radiology, 2Mechanical Engineering, 3Biomedical Engineering; University of Wisconsin, Madison, WI, USA

Purpose: The quality of phase contrast magnetic resonance angiography (PC MRA) from 4D flow MRI images improves with IV contrast. However, there is increasing interest in minimizing use of gadolinium-based contrast agents (GBCA’s) in pediatric MRI studies.1-4 In addition, if the need for anesthesia can be avoided, this would decrease costs and improve the safety of this technique. The purpose of this study was to compare PC MRA quality and flow measurement consistency in neonatal and infant 4D Flow MRI studies with or without contrast. Methods: MR Imaging: This was an IRB approved and HIPAA compliant retrospective study. Twelve subjects under 6 months of age (1 - 126 days; 44 – 61 cm; 1.96 - 7.27 kg), who had 4D flow MRI with PCVIPR5 were identified. 4D Flow MRI scans were performed on clinical 1.5T and 3T scanners (HDx, 450w, 750w, GE Healthcare, Waukesha, WI) with parameters FA 8 - 12, TR 6.1 - 8.1 ms, TE 1.9 - 2.7 ms, ST 0.63 - 1.25 mm. GBCA (0.1 mmol/kg gadobenate dimeglumine, Bracco Diagnostics, Cranbury, NJ) was administered prior to scanning in 4/12 subjects. 4D Flow MRI was performed in 10/12 subjects using an oral feed and scan technique while for 2/12 subjects sedation/general anesthesia was used. Scan data was automatically reconstructed, generating a PC MRA (Figure 1a,c). Qualitative Analysis: Two experienced observers with clinical training in cardiovascular radiology evaluated PC MRA images of each anonymized subject. Image quality of the vena cavae, cardiac chambers, pulmonary arteries, pulmonary veins, ascending aorta, descending aorta and aortic arch was scored as follows: 0: not visible/not present; 1: Non diagnostic; 2: Poor image quality; above average noise and/or artifact; 3: Average image quality; average noise and/or artifact; 4: Very good image quality; minimal noise and/or artifact; and 5: Excellent image quality. Quantitative Analysis: 4D Flow MRI data was processed in Ensight (CEI; Apex, NC) where an isovolume was generated based on complex difference values. Double-oblique planes (Figures 1b,d) in the main, right and left pulmonary arteries (MPA, RPA, LPA, respectively) and three locations in the descending aorta (DAo1-3) were used to calculate net volumetric flow and assess continuity (QMPA = QRPA + QLPA and QDAo1 = QDAo2 = QDAo3). Statistical comparisons were made with two-tailed t-test, = 0.05. Statistical Analysis: Qualitative and quantitative data for contrast-enhanced (CE) and non-contrast-enhanced (NCE) 4D Flow MRI studies were compared with each other. Results: Qualitative scores in all vessels were slightly higher for NCE-4D Flow MRI, 4.00 0.29, than CE-4D Flow MRI, 3.34 0.97; the difference between both groups was not statistically significant (p > 0.05). The overall mean percent difference in flow between MPA and RPA + LPA was 10.0% ± 5.36% and among descending aorta measurements was 6.46% 4.18%. The NCE group obtained a mean percent difference of 8.78% ± 4.80% and the CE group had a mean percent difference of 4.49% ± 2.27%. Percent differences ranged from 1.74% to 16.2%. No significant difference was found between CE and NCE-4D Flow MRI continuity measurements (p > 0.05). Conclusion: There were no significant differences when using CE vs NCE-PC MRA in the present study. Neonatal and infant 4D Flow MRI can be successfully performed without GBCA or sedation/anesthesia, thereby improving safety and decreasing costs. The resulting PC MRA can be used for assessment of thoracic vascular anatomy and flow quantification. References: [1] François CJ. Radiology, 2011. [2] François CJ. AJR Am J Roentgenol, 2008. [3] Morita S. Radiographics, 2011. [4] Paiman EHM. J Magn Reson Imaging, 2017. [5] Gu, T. AJNR Am J Neuroradiol, 2005.

Figure 1. Representative cases showing a) PC MRA and b) pathlines in a NE-PC MRA (3 days old; ascendingaorta aneurysm, hypoplastic arch, PDA). c) and d) show PC MRA and pathlines, respectively, in a CE-PC MRA (11 weeks old; AV canal, elevated velocities in pulmonary veins, double outlet RA).

a) b)

c) d)



— Dariusch HadizadehIntra-individual Quantitative and Qualitative Comparison of Macrocyclic Contrast Agents in Multi-phase 3D-MRA and 4D-MRA at 1.5T and 3T in Minipigs

Intra-individual quantitative and qualitative comparison of macrocyclic contrast agents in multi-phase 3D-MRA and 4D-MRA at 1.5T and 3T in minipigs

Dariusch Reza Hadizadeh1, Gregor Jost2, Vera Keil1, Christian Marx1, Max Rauch1, Carsten Schmeel1, Hubertus Pietsch2, Hans Heinz Schild1, Winfried Albert Willinek3

1Radiology, University of Bonn, Bonn, Germany, 2MR and CT Contrast Media Research, Bayer AG, Berlin, Germany, 3Department of Radiology, Neuroradiology, Sonography and Nuclear Medicine, Brüderkrankenhaus Trier, Trier, Germany

Purpose

Time-resolved contrast-enhanced magnetic resonance angiography- (4D-MRA) is increasingly used for flow analysis, while high-resolution multi-phase 3-dimensional MRA (3D-MRA) is still the standard of reference for vascular imaging (1-5). In order to make the ideal choice of contrast agent (CA) for these applications, parameters such as relaxivity, bolus application and gadolinium concentration and both the arterial and venous imaging phases have to be considered (6-10). This study offers an analysis of bolus kinetics, signal enhancement and diagnostic image quality of gadoterate meglumine (0.5 M) and gadobutrol (1 M) at half- and standard dose in both time-resolved thoracoabdominal 4D-MRA and multi-phase 3D-MRA at 1.5T and 3T.

Methods

8 Goettingen minipigs (7 female, body weight = 33.4±3.7 kg) received 3D- and 4D-MRA examinations in a whole body 1.5T Siemens Avanto and 3T Philips Intera scanner under general anesthesia. The animals were handled in compliance with the German animal welfare legislation and with the approval of the state animal welfare committee. Technical parameters: 4-phase 3D-MRA [1.5T: 3D FLASH, 64 slices, dynamic scan time = 12s, voxel size = (1.2mm)³; 3T: 3D FFE, 40 slices, dynamic scan time = 12s, reconstructed voxel size = (1.1×1.1×1.5 mm)³]; 4D-MRA [1.5T: TWIST, 36 slices, image update time = 1.48s, 40 dynamics, voxel size = (1.7mm)³; 3T: 4D-TRAK, 25 slices; keyhole scan duration = 1.5s, 40 dynamics, reconstructed voxel size = (1.2×1.2×1.6)mm³]. CA applications: 4-phase 3D-MRA [gadobutrol standard dose (0.1 mmol/kg, 1 ml/s, sGB); gadoterate meglumine standard dose (0.1 mmol/kg, 2 ml/s sGM)]; 4D-MRA [sGB, sGM, gadobutrol half dose (0.05 mmol/kg, 1ml/s, hGB). Quantitative analysis: Signal intensity analysis of aorta, inferior vena cava and vena portae. Qualitative analysis: three independentradiologists; visibility of small and large arteries and veins.

Results

4D-MRA at 3T: sGB provided the highest signals in all examinations (figure). Peak signal cut-off effects (plateau or peak reversal) in first pass arterial bolus were observed in 7/8 animals when using sGB and sGM, none in hGB at 3T and none in all examinations at 1.5T. 4D-MRA peak signals were significantly higher with sGB than sGM or hGB in all vessels at 1.5T and in venous vessels at 3T. In 3D-MRA signal enhancement was significantly higher using sGB compared to sGM. Again, these differences were particularly marked in the venous imaging phases. Image quality analysis of 3D-MRA revealed significantly higher image quality in venous phases with sGB compared to sGM at both 1.5T and 3T with excellent overall interobserver-agreement (Fleiss Kappa = 0.94).

Discussion

sGB offers the highest signal both in 3D-MRA and 4D-MRA at 1.5T as well as at 3T. Peak signal cut-off effects are observed in arterial first passage boluses at 3T after sGB and sGM as shown earlier using sGB at 3T (11). Venous phase vessel enhancement particularly profits from sGB application compared to other CAs.



— Henrik HaraldssonHighly Accelerated Multi-directional Motion Encoded 4D-flow MRI

Highly Accelerated Multi-Directional Motion Encoded 4D Flow MRI Henrik Haraldsson1, Sinyeob Ahn2, Michael Hope1, Evan Kao1, Yan Wang1, David Saloner1, Jing Liu1

1 University of California San Francisco, 2 Siemens Healthcare

Purpose: 4D flow MRI has enabled comprehensive access to the hemodynamics, and has been applied in multiple applications, for instance: congenital heart disease, valvular diseases, and aortic disease. Some of the challenges of the technique includes its long acquisition time, and a limited dynamic range of velocities which can be acquired with high velocity-to-noise ratio (VNR). A multi-directional encoding scheme using the direction of the vertices of an icosahedron 6, termed ICOSA6, to extend the velocity range outside the prescribed velocity encoding (VENC) has been shown to improve the VNR ~1.7 times compared to dual-VENC methods [1]. 4D flow with ICOSA6 encoding has further been exploited to improve the assessment of the Reynolds stress tensor describing the turbulent fluctuations and its associated pressure loss [2, 3]. However, extended velocity encoding schemes, such as multi-directional encoding or dual-VENC, requires additional data acquisition which further extend the acquisition time. In this study, we developed a highly accelerated 4D flow acquisition with multi-directional motion encoding targeting improved VNR as well as the acquisition of the Reynolds stress tensor within a clinical relevant acquisition time. Methods: A 4D flow acquisition with multi-directional motion encoding (ICOSA6) and time-resolved sparse data acquisition using Circular Cartesian Undersampling (CIRCUS) [4, 5] was implemented on a 3T MRI system. The sequence was applied to image both abdominal aortic aneurysms (AAA) and the heart. Data was acquired on a Siemens Skyra system with an 18-ch body coil and a 32-ch spine coil. For AAA, the scan settings were: VENC=150cm/s, FOV=280x280mm2, slice thickness=2.2 mm, matrix=128x128x58, FA=8o, TR/TE=5.5/3.3ms; for cardiac: VENC=50cm/s, FOV=32x32cm2, slice thickness=7.0 mm, matrix=128x128x16, FA=6o, TR/TE=6.1/4.0ms. With CIRCUS acquisition and kt-sparse-sense reconstruction [6, 7], the temporal resolution can be chosen retrospectively. In this study, 7 TRs ~40ms was chosen with acceleration factor of R=8 for the AAA case and R=7 for the cardiac cases. The velocity data was post-processed using an in-house developed toolkit written in python. The processing pipeline included: background offset phase correction to compensate for eddy currents, phase unwrapping, segmentation of the vessel/left ventricle and myocardium, computation of velocities from the phase data as well as computation of the relative pressure by solving the Pressure Poisson Equation. Visualizations were generated using Paraview. Results: The AAA case required an acquisition time of 10.2 minutes and the results are shown in Figure 1. The figure shows the streamlines in both the high-speed tubular lumen, the low-speed saccular aneurysm, and a jet causing an onset of turbulent flow in the iliac artery. The cardiac case was acquired in 4.5 minutes. The magnitude and the three unwrapped velocity components from a single slice of the 4D data are shown in Figure 2. Discussion: We have implemented and tested a highly accelerated multi-directional velocity encoding 4D flow MRI method for overcoming some of the current technical limitations. The technique allows for unwrapping, which can be used to improve VNR, and the quantification of the Reynolds stress tensor, which improves the computation of pressure maps in presence of turbulent flow. Our preliminary results show great potential of the method for applications such as aneurysm and cardiac flow evaluation. References: 1. Zwart et al, MRM 2013; 2. Haraldsson et al, ISMRM 2015; 3. Kefayati et al, ISMRM 2015; 4. Liu et al, QIMS 2014; 5. Liu et al, NMR in Biomed 2016; 6. Otazo et al. MRM 2010; 7, Feng et al. MRM 2013.

Figure 1: Flow data from a patient with saccular aneurysm and an iliac stenosis. The velocities are shown to the left and the turbulence to the right.

Figure 2: (Left) The magnitude and three velocity components in a single slice from a 3D volume. The data has been unwrapped, and includes velocities exceeding the VENC. (Right) Streamline showing flow during systole.



— John HeerfordtExploring Binning Strategies for Respiratory Motion-resolved Coronary MRA in Patients

Exploring Binning Strategies for Respiratory Motion-Resolved Coronary MRA in Patients John Heerfordt1,2, Jérôme Yerly1,3, Lorenzo Di Sopra1, Pier-Giorgio Masci4, Matthias Stuber1,3, Davide Piccini1,2

1Department of Radiology, University Hospital (CHUV) and University of Lausanne, Switzerland; 2Advanced Clinical Imaging Technology, Siemens Healthcare AG, Lausanne, Switzerland; 3Center for Biomedical Imaging, Lausanne, Switzerland; 4Division of Cardiology and Cardiac MR Centre, CHUV, Lausanne, Switzerland

Purpose: To increase acquisition efficiency and obtain predictable scan durations in free-breathing coronary MRI, recent research has moved from navigator-gating to advanced approaches where respiratory motion is either resolved [1] or corrected for [2]–[4] using the acquired image data. One approach to resolve respiratory motion consists ofextracting a respiratory self-navigation signal which is used to sort segments of readouts into respiratory motion binsand reconstruct one 3D volume for each bin, exploiting the redundant information [5]. In healthy volunteers, respiratoryself-navigation signals extracted from k-space centre amplitude modulations [1] generally show littlebaseline variation over time making binning straightforward. However, in self-navigation signals from patients drift and irregularities in the baseline are more common. Whether thecause of such variations is physiological or not affects theadequacy of respiratory bin assignment. In these cases,direct data sorting may mix end-expiratory and end-inspiratory positions within the same bin causing adegradation of image quality. The scope of this work was toevaluate the impact that removal (“detrending”) of suchbaseline variations in self-navigation signals has on imagequality of motion-resolved reconstructions. Methods: The study included datasets from N=8 patients (45 12 yrs., 6/2 M/F) acquired with a prototype imaging protocol described in [1]: bSSFP acquisition on a 1.5T clinical MRI scanner (MAGNETOM Aera; Siemens Healthcare) with an ECG-triggered segmented 3D radial trajectory [6]. Parameters: TE=1.71-1.79 ms, TR=3.42-3.58 ms, matrix=2083–2243, resolution=0.893–0.963 mm, flip angle=114-115º. The first readout in each heartbeat was oriented in the superior-inferior direction and thus respiration modulates the magnitude of its central k-space coefficients [1]. One time series per coil comprising the averaged magnitude of the three central coefficients of these readouts was input to an independent component analysis (ICA) algorithm [7] as described in [1]. The component with the highest spectral peak in the typical respiratory frequency range of 0.1-0.5 Hz was assumed to represent respiratory motion. This self-navigation signal will be referred to as the original signal (OS). A detrended signal (DS) was obtained by zero-phase filtering the OS with a length five moving average window and subtracting it from the OS. After outlier removal (>2 s.d. from mean), both signals were independently sorted into four respiratory bins containing an equal amount of data segments [1]. Extraction of self-navigation signals, binning and reconstruction using XD-GRASP [5] were performed in an automated pipeline in MATLAB 2015a (MathWorks, Natick, MA). Total variation regularization was applied along the respiratory dimension. To compare image quality between the two approaches qualitative visual assessment as well as quantitative measurements of visible vessel length and proximal sharpness of the RCA were computed for the end-expiratory position using dedicated software [8]. Paired sample two-sided t-tests at 5% significance level were carried out as statistical analysis of vessel sharpness and length. Moreover, the difference in the resulting binning was investigated. Results: Detrending had high impact on the binning procedure: 33.6±9.3% (range 18.8-48.3%) of all heartbeats were assigned to a different bin or considered an outlier in one of the signals but not the other. In signals with highly varying baseline, detrending removed longer periods without any data being assigned to the boundary positions end-inspiration and end-expiration as depicted in Figure 1a. Visually, the reformats of the RCA, image quality and resolved respiratory motion from the two approaches were highly similar (cf. Figures 1b-c). The similarity was confirmed by the quantitative measures. The vessel sharpness in the first 4 cm of the RCA was 42.1±9.4 for OS and 40.2±7.3 for DS with no significant difference (p=0.31). The visible vessel length was 10.5±2.3 for OS and 10.8±2.5 for DS also here without significant difference (p=0.50). Discussion: The minor impact that detrending had on the reconstructed images suggests that as long as the dominant part of the data in a bin was acquired in a similar position, respiratory motion will be partially resolved. It also emphasizes the robustness of 3D radial acquisitions to motion, especially when combined with regularized compressed sensing reconstructions. Since no improvement in image quality was obtained with the detrending procedure, a physiological cause of baseline variations in respiratory self-navigation signals from k-space centre amplitude modulations (e.g. respiratory drifts) cannot be excluded. Future work could include normalization of respiratory periods to similar amplitudes, optimization of the filter used for detrending and correlating baseline variations in gating signals from respiration bellows, navigators and self-navigation both in patients and healthy volunteers. References: [1] Piccini D, MRM 2017, 77(4):1473-1484 [2] Pang J, MRM 2014, 72(5):1208–1217 [3] Aitken AP, MRM 2015, 74(3):756–764 [4]Bhat H, MRM 2011, 65(5):1269-1277, [5] Feng L, MRM 2016, 75(2):775–788 [6] Piccini D, MRM 2011, 66(4):1049–1056 [7] Hyvarinen A, IEEE NNLS 1999, 10:626–634 [8] Etienne A, MRM 2002, 48(4):658–666

Figure 1: Analysis of the subject where most heartbeats were assigned differently between OS (top) and DS (bottom) a) Binned signals, green bin = end-expiration, red star = outlier b) Reformats of RCA at end-expiration c) Coronal views at end-expiration (left) and end-inspiration (right) showing little translational motion in the superior-inferior direction

(a) (b)

(c)



— Carson HoffmanContinuous Intracranial Flow MRI with High Frame Rates

Title: Continuous Intracranial Flow MRI with High Frame Rates Carson A. Hoffman1, Oliver Wieben1,2, ,Tilman Schubert2, Charles Mistretta1, Charles Strother2, and Kevin M. Johnson1,2

1Department of Medical Physics, University of Wisconsin, Madison, WI, 2Department of Radiology, University of Wisconsin Madison, WI,

Purpose: Phase Contrast (PC) MRI can be used for quantitative intracranial velocity and flow measurements. However, standard approaches use acquisition schemes that extend over several cardiac cycles and thus are not suitable to assess beat-to-beat changes in flow and heart rate. This precludes their use to assess the response to functional challenges including breath holds, exercise, contrast injections, or others. Here we investigate the feasibility of a 2D PC acquisition and reconstruction scheme that allows for continuous flow measurements with a temporal resolution of 54 ms in a canine model during intra-arterial contrast injection. Methods: A 2D radially undersampled PC sequence1 with golden angle view ordering was implemented on a clinical 3T scanner (MR 750, GE Healthcare). In vivo imaging was performed with institutional approval in the neck of an anesthetized canine before, during, and after an 11 s intra-arterial injection of an iodinated contrast agent (Omnipaque, X-ray agent, injection: 33 ml @ 3ml/s) into the right carotid artery (CA). An axial slice was located proximal to the carotid bifurcation and perpendicular to the jugular veins (JV) and common CAs. Breathing was controlled by a ventilator and suspended for 20 s during contrast injection. Scan parameters: 0.5x0.5mm in-plane resolution, FOV: 160x160 mm, slice thickness=8mm, TR/TE = 6.7/2.9 ms, flip angle = 10°, Venc = 100 cm/s, scan duration: 4,800 projection angles x 2 velocity encodes x TR = 64 s, 8 channel knee coil. Frame-by frame PC data were reconstructed offline with locally low-rank constraints: 1,200 frames with a temporal resolution of 53.6 ms (4 projections x 2 velocity encodes x TR). Post-processing was accomplished with a semi-automated algorithm (Matlab 2016a). A mouse-click in each of the four vessels initiated the automated vessel segmentation based on a local k-mean clustering algorithm using the complex-difference and velocity magnitude data as previously applied to 4D flow MRI cranial data3. Results: Fig. 1 shows the flow measures for the left and right JVs and CAs during the injection and smoothed to remove cardiac pulsatility. The flow in all four vessels increases with the onset of the injection and eventually decreases to a new, higher baseline. Fig. 2 shows the flow in the right CA without filtering (a). Note the cardiac pulsatility capturing systolic and diastolic flow. The flow waveform over the cardiac cycle at 3 representative time points show that the systolic flow stays fairly constant while the diastolic flow increases during injection and then decreases. Conclusion: We demonstrated the feasibility of capturing rapid changes in flow to response of a functional challenge with a radial 2D PC MRI acquisition and a low rank reconstruction. Changes in flow and flow waveforms due to cardiac pulsatility, respiratory motion, and contrast injection were shown due to the high temporal resolution of the continuous acquisition. The underlying mechanisms for the observed flow changes during contrast injection are complex and currently under investigation in a coupled MRI and DSA study (superimposed blood flow and flow from injection coupled with local and global cranial autoregulation mechanism). This approach has potential for the investigation of other functional challenges Valsalva maneuvers (e.g. Chiari malformations), response to exercise, and more. Additional quantitative in vivo flow studies are needed for further validation but, unfortunately, not trivial for the lack of an accessible gold standard. References: [1] A. V. Barger, MRM 43.4 (2000): 503-509.[2] J. Trzasko , ISMRM 2011, p. 4371.[ 3] E. Schrauben, JMRI 42.5 (2015): 1458-1464. Acknowledgements: The authors acknowledge the support of NIH grant (NINDS) R01 NS066982 and thank GE Healthcare for their support.

Fig. 1. Magnitude image and vessels segmentation of the jugular veins and carotid arteries (top panel) and corresponding flow waveforms after low-pass filtering. The flow in all vessels increases after the start of the injection at 17 s. Also note the respiratory modulation in the venous waveforms except during injection when the respirator is switched off.

Fig. 2. Unfiltered flow measures in the left common carotid artery distal to the catheter tip (a) and flow measures from selected cardiac cycles prior (1, red), during (2, blue) and after (3, black) contrast injection (b).



— Rami HomsiPreliminary Experience with Simultaneous Arterial and Venous High-resolution Late-phase Imaging of the Run-offs Using Gadobutrol

Preliminary experience with simultaneous arterial and venous high-resolution late-phase imaging of the run-offs using gadobutrol

Rami Homsi1, Patrick Kupzcyk1, Frank Träber1, Winfried Albert Willinek1, Hans Heinz Schild1, Dariusch Reza Hadizadeh1

1Radiology, University of Bonn, Bonn, Germany

Purpose: Three-dimensional contrast enhanced magnetic resonance angiography (MRA) is a routine application in the assessment of run-off vessels in patients with peripheral arterial disease (PAD) in many centers1,2. Late-phase high resolution imaging (LPMRA) with blood-pool contrast agents (BPCA) in the equilibrium phase (“steady state”) using gadofosveset trisodium has been shown to provide better delineation of arteries helping to prevent both under- and overestimation of stenosis grades and excellent venous delineation that allowed for the diagnosis of unexpected venous thromboses in many cases3,4. However, BPCA are currently not available on the market and steady state imaging became unavailable. Pre-clinical data on minipigs has suggested benefits of gadobutrol over a .5 molar contrast agent for venous imaging suggesting a possibly beneficial role for LPMRA. The purpose of this study was to assess image quality and contrast parameters of both arteries and veins in first pass and in LPMRA using the macrocyclic 1-molar contrast agent gadobutrol.

Methods: Nine patients (4 men, 5 women; mean age, 70 +/- 8.4 years) with suspected or known peripheral arterial occlusive disease underwent FPMRA after administration of a single dose of gadobutrol at 1.5 Tesla and immediately afterwards LPMRA in the order 1.calfs, 2. upper legs, 3. pelvis. Technical parameters for first-pass imaging (FPMRA) were as follows: TR/TE, 2.9-4.1; slices, 94-117; acquired voxel, 1.73-2.40 mm³; acquisition time, 8.9-34.1s; FOV, 450mm². Those for LPMRA: TR/TE, 6.1-6.4; slices, 237-280; acquired voxel, 0.36-0.43mm³; acquisition time, 206-221s5; FOV, 450mm². In 3/9 patients catheter angiographies of the lower extremities were available for comparison. Two investigators with >5yrs. of experience in MRA evaluated the image quality of arteries in FPMRA and both arteries and veins in the run-off vessels. Arteries were evaluated regarding the visibility of plaques and stenosis grades, whereas veins were evaluated with respect to their delineation, the assessability of thrombosis and the ability to differentiate arteries from veins on a 3-point scale. Quantitative analysis was performed by calculation of contrast-ratios (CR) = (A - B) / (A + B) of vessel lumen compared to adjacent muscle and fat with A being the vessel lumen of the vessel of interest and B adjacent muscle or fat.

Results A total of 111 arterial segments were available for intra-individual comparison of FPMRA and LPMRA and 130 venous segments were evaluated in LPMRA. Delineation of vessel walls/atherosclerotic plaques was rated significantly higher in LPMRA than in FPMRA (1.75±0.47 vs. 1.05±0.42; P<0.05). Ability to confidently rule out stenosis was rated similarly high with both methods in the calfs and upper legs (>90.2-100%), whereas in the pelvis region, FPMRA was rated significantly higher (P<0.05). Delineation of veins and the ability to differentiate them from arteries as well as the ability to rule out thrombosis were rated high in the upper legs and epifacial veins of the entire leg, but only average in the veins of the pelvis and calfs. In 7/111 arterial segments, LPMRA and FPMRA stenosis grading differed due to partial volume effects in FPMRA (figure). Incidental thrombosis was found in one patient in the posterior tibial vein. Vessel to both fatty tissue and muscle CR were significantly higher in FPMRA compared to LPMRA (p<0.05). In LPMRA there were no significant differences regarding arterial and venous vessels.

Discussion As expected, CR was significantly higher for FPMRA compared to LPMRA. Nevertheless, high-spatial-resolution LPMRA with gadobutrol led to a significantly better delineation of the vessel wall that allowed better stenosis grading and visualization of veins and led to the diagnosis of an incidental thrombosis not visible in FPMRA. The latter is in line with earlier results revealing incidental thromboses in up to 10% of patients. LPMRA may therefore serve as a valuable add-on in imaging of the run-off vessels.

Figure: 59 year old female with peripheral arterial occlusive disease Fontaine Grade II

A: subtracted MIP of the upper legs shows irregularities, but now major stenosis.

B: Non-subtracted transversal multiplaner-reformat of FPMRA shows no stenosis at the position of the arrow in A.

C: Transversal multiplaner-reformat of LPHRMRA at the same lodcation as B reveales high grade stenosis caused by a plaque at the medial vessel wall.

References: 1: Willinek WA et al. Stroke 2005;36:38–43; 2: Prince MR et al. J Magn Reson Imaging 1993;3: 877–881; 3: Hadizadeh DR et al. Radiology 2008;249(2):701-11; 4: Hadizadeh et al. AJR Am J Roentgenol. 2012 May;198(5):1188-95 5: Homsi et al. Magn Reson Imaging. 2015 Nov;33(9):1035-42


1.Preferred presentation: oral

2.Scientific categories for your presentation: Contrast media, High-resolution MRA, venous imaging

3.Synopsis:

Late-phase high resolution imaging (LPMRA) with blood-pool contrast agents has been shown to be superior in the evaluation of both arteries and veins in dynamic 3D-MRA. However, the possible value of the macrocyclic 1-molar contrast agent gadobutrol for LPMRA has not yet been investigated. This study assesses parameters of image quality of both arteries and veins of gadobutrol-enhanced LPMRA in comparison to first-pass MRA (FPMRA). Though contrast ratios were higher in FPMRA, LPMRA with gadobutrol allowed for better vessel wall delineation, stenosis grading and visualization of veins and may thus serve as a valuable add-on in imaging of run-off vessels.



— Keiji IgasePrediction of Progressing Stroke in Branch Atheromatous Disease Using 3T MRI

Prediction of Progressing Stroke in Branch Atheromatous Disease Using 3T MRI

Keiji Igase, Ichiro Matsubara, Nari Tei, Takanori Ohnishi, Kazuhiko Sadamoto

Department of Neurosurgery, Washokai Sadamoto Hospital, Matsuyama, Japan

(Introduction) Branch atheromatous disease (BAD) is one of ischemic brain diseases due to the

injury of the perforating artery involving its parent artery, and is considerably difficult to treat.

Etiology of this disease is profoundly related to the parent artery atherosclerosis, however, which is

difficult to be assessed using imaging modalities. Recently 3T MRI has shown up and the new

technique has been also developed. This time we used new protocol enabling the vessel wall to be

clearly delineated and evaluated the difference between cases with progression and those without,

besides, whether we could predict whether the case would have progression or not.

(Methods) Consecutive 23 patients (mean age: 69.4 years

old; Male 13 and Female 12) with BAD (both territories of

middle cerebral artery and basilar artery) diagnosed with 3T

MRI during 2 years (April 2015 to March 2017) were enrolled

in this study. All patients underwent 3T MRI (SIGNA HDxt or

Discovery 750w: GE healthcare), with which both two images

of 3D-TOF MR Angiography (MRA) and T1-BB CUBE, which is

one of 3D-FSE sequence created by GE healthcare, were

obtained. We graded TOF-MRA findings point 0 to 2 depending on the

appearance of parent artery. In respect to T1-BB CUBE we assessed the

appearance as well as the plaque calculating its length and height on T1-BB

CUBE, further we compared the difference between cases with progression

and those without, where progression was regarded as an apparent

deterioration of symptom in 7 days.

(Results) Regarding the grading scale on TOF-MRA progression case

was 1.3 ± 0.5 and no progression case was 1.1 ± 0.7, where no significant

difference was seen. On T1-BB CUBE most of cases disclosed high

intensity plaque of the parent artery except 2 cases, out of 21 cases revealing high intensity plaque

8 cases had progression in symptom, whereas 13 cases had no progression. Mean length of plaque

in progression and no progression cases was 4.3 ± 0.7 mm and 3.0 ± 0.6 mm, and mean height was

1.0 ± 0.4 and 1.2 ± 0.3, respectively, where there was a significant difference between cases only in

length of plaque (p < 0.05)

(Conclusion) Using T1-BB CUBE protocol progression cases of BAD might be predicted before

deterioration, accordingly there would be a possibility to start a better treatment before deterioration.

However, further investigation should be necessary to confirm these results.


1. Preferred presentation: oral, poster, or either

2. Scientific categories for your presentation: Intracranial vessel wall analysis

3. Synopsis: Brief summary of the abstract (max. 100 words):

Branch atheromatous disease (BAD) is one of ischemic brain diseases and occasionally

has deterioration in symptom. We tried to predict progression case using new protocol of 3T

MRI. Consecutive 23 patients with BAD during 2 years were enrolled. All patients

underwent 3T MRI and T1-BB CUBE, on which 21 cases revealed high intensity plaque,

and length of plaque in 8 cases with progression was 4.3 ± 0.7 mm, which is significantly

different with length of 3.0 ± 0.6 mm in 13 cases with no progression. Using T1-BB CUBE

protocol progression cases of BAD might be predicted before deterioration.



— Haruo IsodaParameters Based on Blood Flow Velocity of Cerebral Intracranial Aneurysms: Comparative Study with Computational Fluid Dynamics

Parameters Based on Blood Flow Velocity of Cerebral Intracranial Aneurysms: Comparative Study with Computational Fluid Dynamics

Kenta Ishiguro1), Haruo Isoda2),1), Yasuo Takehara3), Masaki Terada4), Takehiro Naito5),6), Chiharu Tanoi6), Takafumi Kosugi7), Yuki Onishi8), Atsushi Fukuyama1)

1) Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School ofMedicine, Nagoya, Japan, 2) Brain & Mind Research Center, Nagoya University, Nagoya, Japan,

3) Department of Fundamental Development for Advanced Low Invasive Diagnostic Imaging,Nagoya University, Graduate School of Medicine, Nagoya, Japan, 4) Department of Diagnostic Radiological

Technology, Iwata City Hospital, Iwata, Japan, 5) Department of Neurosurgery, Komaki City Hospital, Komaki ,Japan, 6) Department of Neurosurgery, Iwata City Hospital, Iwata, Japan, 7) Renaissance of

Technology Corporation, Hamamatsu, Japan, 8) Department of Systems and Control Engineering, Tokyo Institute of Technology, Tokyo, Japan

PURPOSE Hemodynamics plays an important role in intracranial aneurysm initiation, growth and rupture. In the clinical field the criterion standard for hemodynamic analysis is computational fluid dynamics (CFD). Magnetic resonance fluid dynamics (MRFD), however, has a faster processing time and some previously published papers have reported that there is good correlation between velocity vectors of aneurysms obtained with MRFD and CFD. Recent research has been focusing on the hemodynamic differences between unruptured and ruptured aneurysms to predict future aneurysm growth and rupture. The purpose of our study was twofold; to investigate whether blood flow velocity biomarkers acquired from MRFD are as accurate as CFD and to predict aneurysm growth and bleb formation based on these biomarkers. METHODS This study included 57 aneurysms of 48 patients who were followed up with 3D TOF MRA and 3D cine PC MRI. One aneurysm ruptured 2 years after the imaging and 12 aneurysms were growing. Others were unruptured. Twenty three aneurysms had blebs. Using these data, we performed MRFD and CFD. Maximum and spatial averaged inflow velocity into aneurysms, inflow concentration index (ICI) [1], energy loss (EL) [2], pressure loss coefficient (PLc) [3] and EL aneurysms [4] were obtained with MRFD and CFD. We correlated biomarkers of MRFD with those of CFD using a regression analysis and calculated interclass correlation coefficients (ICC). We classified aneurysms into subgroups based on growth and bleb formation and performed statistical analysis. We performed ROC analysis for the statistically significant different biomarkers. Youden index was used as the threshold value to calculate sensitivity and specificity for MRFD and CFD. RESULTS and DICUSSION Good correlation was shown by regression analysis (0.819<r<0.97) and ICC (more than 0.8). Aneurysms were classified into subgroups based on growth and bleb. In EL and PLc, growing aneurysms had higher values than stable aneurysms for both methods (p<0.05). In ICI, aneurysms with bleb had higher values than aneurysms without bleb for both methods (p<0.04). Sensitivity for these biomarkers was 0.7 or higher for both MRFD and CFD; this suggests that MRFD can predict aneurysm growth using EL and PLc and predict bleb formation with ICI. Patients who have high values in these biomarkers should be followed up as risk of growth and bleb formation may be high. CONCLUSIONS Blood flow velocity biomarkers obtained from MRFD show the same accuracy as CFD. MRFD can predict aneurysm growth using EL and PLc and bleb formation with ICI. REFERENCES [1] Cebral JR, et al. AJNR Am J Neuroradiol. 2011; 32: 145-51.[2] Qian Y, et al. AJNR Am J Neuroradiol. 2011; 32: 1948-55.[3] Takao H, et al. Stroke. 2012; 43: 1436-9.[4] Farnoush A, et al. J Clin Neurosci. 2014; 21: 1514-9.



— Kevin JohnsonAccelerated, SMS-MOTSA, Radial 4D-flow Imaging with Magnetization Transfer Preparation

Accelerated, SMS-MOTSA, Radial 4D-flow imaging with Magnetization Transfer PreparationKevin M. Johnson1,2, James Holmes2, Oliver Wieben1,2, Patrick A. Turski2

Department of Medical Physics1 and Radiology2, University of Wisconsin – Madison, USA

Purpose: 4D-flow imaging encodes velocity information in the phase of the signal; however, its accuracy and precision can depend on the signal magnitude. Twoexamples include the direct relationship to velocity to noise ratio (VNR) and the presence of aliased signal from high intensity background which can obscure vessel characterization. For these reasons, 4D flow often performs much better after the administration of a contrastagent. In this work, we explore the possibility of improving the quality of non-contrast enhanced 4D-flow by (1) enhancing the inflow signal with an accelerated simultaneous multiple overlapping slab (SMS) approach and (2) reducing background signal using magnetization transfer (MT).

Methods: Acquiring multi-thin slabs improves 4D flow imaging1 but leads to slab boundary artifacts. As is well known from 3D time-of-flight, this artifact can be corrected but acquiring multiple overlapping slabs prolongs scan time. SMS has been suggested to accelerate the acquisition of 3D TOF2 and non-overlapped 4D-flow acquisition3,4. Our proposed method combines these priniciples to create 4D-flow images with similar magnitude to 3D-TOF: Slabs are excited utlizing a multi-band transformed minimum phase RF excitation, exciting multiple slabs as shown in Figure 1. Multiple acquisitions are required to achieve contigous coverage with overlap to reduce slab boundary effects. K-spacesamples are collected utilizing 3D radial sampling which enables constrained reconstruction and self-calibration of the slabexcitation magnitude and phase profiles. Intermitent MT preparation is performed to reduce the signal from muscle andbrain matter. Complex images are reconstructed jointly with sensitivity maps estimated from the central k-space data and asparse-SENSE solution. Following reconstruction, slab merging is performed independently for magnitude and phase, usinga magnitude weighted least squares aproach to maximize SNR. Initial feasibility images were collected on a 3T MRI with a32ch head coil. Imaging included 4 slabs with a SMS factor of 2, TE/TR=2.8/8.8ms, Venc=80cm/s, Imaging flip angle=11°,Slab thickness=46mm, Overlap=15%, and 0.7mm isotropic resolution. MT saturation was applied every 30 TR’s with an8ms fermi RF pulse at 1600 Hz off resonance with a flip angle of 1500°.

Results and Discussion: Figure 2 shows representative images from the non-contrast SMS accelerated 4D acquisition. Magnitude images show substantial contrast with brain tissue (~3x at the MCA level). PC-MRA and flow fields show contiguous depiction of vessels and flow. These results suggest the technique may be useful for improved non-contrast imaging, although controlled studies are needed. Magnitude partial volume will need to be considered to prevent overestimation of flow parameters.

References: [1] Schulz et al. MRM 16’ 75(4):16662, [2] Hafalir et al. ISMRM 17’ #2845 [3] Schmitter et al. ISMRM 17 #1257 [4] Feinberg & Chen ISMRM 17’ #1504

Figure 1. Reformatted magnitude and phase images from a 4 slab (2xSMS) 4D flow acquisition. Magnitude merging is performed by taking the location with the highest flip angle, while phase is combined with magnitude weighted least squares to reduce the noise variance.

Figure 2. Example MT prepared SMS, limited MIP PC-magnitude images (a) showing substantially increased vessel conspicuity compared to a standard PC image (b). In magnitude images, the signal ratio of the MCA to white matter was ~3x(MT-SMS) vs ~1.3x(Std). Coronal MT-SMS PC-MRA (c) and streamline (d) images show limited slab boundary artifacts. The slab overlap is indicated with arrows in streamline images.



— Lilli KaufholdImage-based Assessment of Uncertainty in Carotid Lumen Quantification

Image-based Uncertainty in Carotid Lumen Quantification

Lilli Kaufhold1, Andreas Harloff2, Lennart Tautz1, Markus Huellebrand1, Christoph Strecker2, Axel J.Krafft2 and Anja Hennemuth1,3

1Fraunhofer MEVIS 2University Hospital Freiburg 3Charite Berlin

1 Purpose Measurements of the lumen in carotid arteries are an important tool for the assessment of pathologies.However, the measurements depend on imaging parameters, patient position and other factors (see [1]). Therefore, weaim at providing a tool, that gives an estimate of lumen uncertainties, so that they can be taken into consideration forfollow-up examinations and therapy planning.

2 Methods Contrast-enhanced magnetic resonance angiography (CEMRA), subtraction images (SUB) and Time-of-flight-MRA (TOF) were performed in seven patients with severe carotid atherosclerotic plaques. All images wereacquired on a Siemens 3T scanner. The CEMRA and SUB images have voxel dimensions of 0.6× 0.6× 0.7mm3, whilethe TOF images were acquired with voxel dimension 0.5× 0.5× 1.0mm3.For each image type, the lumen was segmented automatically using an intensity-based segmentation with partial volumecorrection. The segmentation was guided by an interactively generated centreline. Measurements for statistical analysiswere extracted at specific planes which were oriented perpendicular to the centreline and cover the CCA, ICA and ECAin close proximity of the bifurcation. Starting on the CCA 2cm below the flow diverter , the planes were positioned in stepsof 4mm along the centreline within a sphere with radius 2cm around the flow diverter. Furthermore, we added 5 moreplanes 2cm along the CCA further away from the bifurcation for comparison, denoted as CCAref (see Fig. 1a). Thus,corresponding planes of the same vessel in different image types can be compared. Distances between cross-sectionalgravity center and lumen wall are calculated for 12 sectors in each plane (see Fig. 1).

3 Results The results can be explored in an intuitive bulls eye plot 3D visualisation and be rendered as a curve(values for CCAref are not shown, see Fig. 1). The visualisations show an increase of disagreement close to thebifurcation. Table 1 summarises the quantification of the diameter differences between the three image types availablein our dataset.

(a) (b) (c) (d) (e)Figure 1: (a) Positions for the measurement planes (b)+(c) Extracted carotid anatomy with bulls eye views rendered atthe plane positions for one patient (d) The inner ring illustrates the lumen diameter averaged within the sectors of oneplane, where green means a larger diameter compared to the rest of the vessel and red indicates smaller values. Theuncertainty is visualised in the outer ring. Here, a brighter blue means a larger disagreement between TOF and CEMRA(e) Plots of difference between corresponding planes in TOF and CEMRA image peaking right after the bifurcation

Differences [mm] All w/o CCAref CCAref

|TOF − CEMRA| 0.44 (± 0.45) 0.39 (± 0.29)

|SUB − CEMRA| 0.13 (± 0.18) 0.12 (± 0.07)

TOF − CEMRA -0.09 (± 0.63) -0.13 (± 0.48)

SUB − CEMRA -0.11 (± 0.19) -0.12 (± 0.07)

Table 1: Mean differences and standard deviation inmillimeters for the diameter measurements in differentimage types for corresponding planes. Values in thelast two rows may indicate a bias.

4 Discussion We have presented a tool for the quantita-tive and visual analysis of angiography based lumen assess-ment of the carotid arteries. In the application to TOF, CEMRAand SUB images, we observed that the average absolute er-ror between TOF and CEMRA was 0.44mm, which is smallerthan the actual spacial resolution. The disagreement could beexplained by differences in image orientation, resolution, andimaging techniques. Another uncertainty comes from the place-ment of planes, since they are oriented perpendicular to thecentreline, their orientation and thus potentially also the diame-ter will vary, if the centreline is curved differently.We have seen that there are regions that are prone to inaccu-racies as for example the bifurcation. Our tool could be helpfulin identifying such regions and considering the uncertainties inthe interpretation of quantitative results.

References[1] Jean Marie K. S. U-King-Im et al. Measuring carotid stenosis on contrast-enhanced magnetic resonance angiogra-

phy. 35(9):2083–2088.



— Seong-Eun KimMeasurement of T2 of Symptomatic and Asymptomatic IntraPlaque Hemorrhage by Using Motion Insensitive 3D Multiple Echo Inversion Recovery Stack of Star (ME IR SOS) Technique

Measurement of T2* of Symptomatic and Asymptomatic IntraPlaque Hemorrhage by using Motion Insensitive 3D Multiple Echo Inversion Recovery Stack of Star (ME IR SOS) Technique

Seong-Eun Kim1, J Rock Hadley1, J Scott McNally1, Bradley D Bolster, Jr. 2, Gerald S Treiman3, and Dennis L Parker1

1UCAIR, Department of Radiology and Imaging Sciences, University of Utah, 2Siemens Healthcare, 3Department of Veterans Affairs, VASLCHCS

Purpose: Intraplaque hemorrhage (IPH) detected with carotid MRI identifies plaques at increased risk of future and recurrent stroke.1-3 We developted a 3D Multiple Echo (ME) IR SOS technique to reduce off resonance blurring and allow measurement of T2* in atherosclerotic plaque4,5. We hypothesized that T2* measurements from 3D ME IR SOS would help identify IPH and further characterize symptomatic and asymptomatic IPH.

Method: MRI studies of eight symptomatic and seven asymptomatic patients with known carotid IPH were performed on a Siemens Prisma 3T MRI scanner with neck-shape-specific (NSS) coil arrays5. The imaging parameters for 3D ME IR SOS were: coronal plane, FOV = 180x180mm2, voxel dimension = 0.73mm3, TI = 320ms, TE1/TE2/TE3/TR = 2.05/4.15/6.25/9.0ms, 80slices/slab. The scan time was 2min 40sec. The T2* was calculated with least-square estimation based on the semi-log linear regression of the signal values from all echoes and their corresponding echo time. We measured ADC using 3D DWDE SOS sequence.6 T2* and ADC maps were calculated and displayed using IDL. Three ROIs per each patient were selected in IPH for T2* and ADC measurement.

RESULTS:

The mean T2* and ADC for IPH obtained from 18 subjects are summarized in Table 1. Symptomatic compared to asymptomatic had significantly lower plaque T2* values (16±3.6 vs. 27±4.2ms, respectively, p<0.005). This value is close to the T2* value reported previously7,8. Fig 1 displays 3D ME IR SOS, T2* and ADC maps from a symptomatic subject with IPH. The ROI drawn by the red lines in the maps Fig 1 demonstrate a typical ROI selection. T2* and ADC values were 15±1.6ms and 0.91±0.17x10-3mm2/s, mean±SD.

DISCUSSION: 3D ME IR SOS could detect and characterize carotid IPH in atherosclerotic plaque. In symptomatic IPH, T2*-shortening suggests an equilibrium shift of intraplaque iron complexes. Given the greater local effects on magnetic susceptibility, our finding suggests that aggregate iron complexes preferentially form in symptomatic plaque. Further study is needed to determine the amount, species, and chemistry of intraplaque iron complexes and their relationship with the T2* signal change in IPH development and maintenance. The SOS sequence is less sensitive to motion artifacts due to the repeated high-density sampling of the k-space center but is more sensitive to off-resonance effects. The off-resonance sensitivity can be reduced by increased sampling bandwidth. This paper presented triple echo measurements with moderately increased bandwidth. Acquiring more than three echoes with higher bandwidth may allow gradient timing calibration and multi-point fat-water separation in addition to T2* determination.

REFERENCES: 1. Saam T, et al. Radiology 2007;244(1):64. 2. Gupta A, et al. Stroke 2013;44(11):3071.2. Moody AR, et al. Circulation 2003;107(24):3047. 4. Kim SE, et al. JMRI (2016) 45(2):410-417.5. Beck MJ, et al. MRM (2017) Accepted. 6. Kim SE, et al.Proceedings of the 24th ISMRM, Singapore, 2016.7. Zhu DC, et al. MRM. 2010 64:1341.. 8. Raman SV, et al. JACC Cardiovasc Imaging 2008;1(1):49.

Table 1: Mean T2* and ADC measured on IPH Symptomatic Asymptomatic P value

T2*(ms) 16±3.6 27±4.2 p<0.005 ADC(10-3mm2/s) 0.72±0.21 1.12±0.38 0.03

Fig 1. 3D ME IR SOS, T2* and ADC maps from a symptomatic patient with IPH. Three red ROI’s were taken on the T2* and ADC maps as indicated.



— Ioannis KoktzoglouRapid, Large Field-of-View Neurovascular MRA Using an Ungated Radial Quiescent-Interval Slice-Selective (QISS) Protocol

Rapid, Large Field-of-View Neurovascular MRA Using an Ungated Radial Quiescent-Interval Slice-Selective (QISS) Protocol

Ioannis Koktzoglou1,2, Shivraman Giri3, Robert R. Edelman1,4

1Radiology, NorthShore University HealthSystem, Evanston, Illinois, USA, 2Radiology, Pritzker School of Medicine, University of Chicago, Chicago, Illinois, USA, 3Siemens Healthineers, Chicago, Illinois, United States,

4Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA

Purpose: MRI evaluation of the extracranial carotid and intracranial vessels is routinely performed using nonenhanced time-of-flight (TOF) protocols. TOF, however, has drawbacks including sensitivity to saturation artifact and limited anatomical coverage that necessitates the acquisition of multiple scans (e.g. 2D TOF extracranially and 3D TOF intracranially) to portray the neurovascular anatomy. Recent work has shown that nonenhanced quiescent-interval slice-selective (QISS) can be used for carotid1 and intracranial MRA2. To date, these QISS protocols have predominantly used Cartesian k-space sampling trajectories and cardiac gating, and have not demonstrated feasibility for portraying the extracranial carotid and intracranial arteries in one rapid and easy-to-use scan. We present a time-efficient radial QISS protocol that enables carotid and intracranial MRA without the need for cardiac gating, and covers a large field-of-view comparable to contrast-enhanced MRA.

Methods: Imaging was performed in healthy volunteers at 3 Tesla (MAGNETOM SkyraFit, Siemens Healthcare, Erlangen, Germany) under an IRB-approved protocol. A prototype QISS MRA protocol was implemented with a radial fast low-angle shot (FLASH) readout using slices tilted ( 22.5°-45.0°) from the coronal plane. Radial sampling was used in place of Cartesian sampling to provide robustness against flow and motion artifacts. Static tissue and veins were suppressed using in-plane and tracking inversion pulses. Typical imaging parameters included: 96-128 2.0 mm-thick slices acquired with 33% overlap, 416mm field-of-view with 1.0/0.5mm acquired/reconstructed spatial resolution, 1-3 shots (i.e. QISS repetitions) per slice, 68 radial views per shot, QISS repetition and inflow times (to center of readout) of 1068ms and 530ms respectively, TR/TE/flip of 15ms/4.9ms/30°, 501Hz/pixel receiver bandwidth, azimuthally equidistant or golden angular view increments. Comparisons were made with TOF protocols.

Results: Ungated radial QISS FLASH MRA displayed the full lengths of the extracranial carotid, vertebral and proximal intracranial arteries in a single protocol taking 5 minutes for 3-shot imaging (Figure 1) and <2 minutes for single-shot imaging. By comparison, standard-of-care TOF MRA provided much less anatomical coverage.

Discussion: Radial ungated QISS FLASH appears to be a promising protocol for rapid, convenient, large field-of-view (>40 cm) imaging of the extracranial carotid and proximal intracranial arteries. Image quality and anatomical coverage are superior to TOF. Further work is needed to determine the clinical accuracy of the technique.

References: 1. Koktzoglou I, Murphy IG, Giri S, EdelmanRR. Magn Reson Med. 2016 May;75(5):2072-7.2. Koktzoglou I, Edelman RR. Magn Reson Med. 2017 May 3. doi: 10.1002/mrm.26715.

Funding: NIH grants R01 HL130093 and R21 HL126015.

Figure 1. Coronal maximum intensity projections obtained with 3-shot radial ungated QISS FLASH MRA (4.8 min) and 2D TOF MRA (5.2 min).



— Ioannis KoktzoglouRadial Fast Interrupted Steady-State (FISS) Magnetic Resonance Angiography

Radial Fast Interrupted Steady-State (FISS) Magnetic Resonance AngiographyIoannis Koktzoglou1,2, Robert R. Edelman1,3

1Radiology, NorthShore University HealthSystem, Evanston, Illinois, United States, 2Radiology, Pritzker School of Medicine, University of Chicago, Chicago, Illinois, United States, 3Radiology, Feinberg School

of Medicine, Northwestern University, Chicago, Illinois, United States

Purpose: Nonenhanced MRA often employs balanced steady-state free precession (bSSFP) or fast low-angle shot (FLASH) readouts. Respective advantages of bSSFP- and FLASH-based readouts include high signal-to-noise ratio and robustness against main magnetic field inhomogeneity. However, drawbacks of bSSFP include sensitivity to off-resonance and coherent out-of-slice transverse magnetization, whereas FLASH is prone to saturation artifact in vessels containing slow flow. We present a variant of bSSFP, termed ‘fast interrupted steady-state’ (FISS) [1] that, when incorporated into a quiescent interval slice-selective (QISS) protocol [2], provides the high signal-to-noise associated with a bSSFP readout while suppressing undesirable out-of-slice spins and high signal from fat, and reduces saturation artifact as compared to FLASH.

Methods: Imaging was performed in healthy volunteers at 3 Tesla (Skyra Fit, Siemens Healthcare, Erlangen, Germany). Each FISS module consists of a series of one to several radial bSSFP readouts positioned between alpha/2 tip-down and tip-up RF pulses. Gradient and RF spoiling were applied between modules to saturate off-resonance spins and out-of-slice magnetization. QISS-based FISS MRA was applied to imaging the lower extremities, carotid arteries, and intracranial arteries. Comparisons were made with QISS protocols acquired with bSSFP and/or FLASH readouts. Radial sampling with azimuthal equidistant projections was used to lessen artifact from arterial pulsation and respiration.

Results: Radial QISS FISS MRA produced angiograms that were distinct in appearance from QISS bSSFP and FLASH MRA. In general, QISS FISS MRA provided better arterial-to-background contrast than QISS bSSFP, with an improved degree of fat suppression. For ungated MRA of the lower extremities, QISS FISS MRA suppressed flow artifacts that were seen with QISS bSSFP MRA. In the carotid and intracranial arteries, QISS FISS MRA reduced saturation artifact compared with QISS FLASH MRA, and suppressed artifacts associated with off-resonance and flow that were seen with QISS bSSFP MRA (Fig. 1).

Figure 1: Comparison of QISS FISS MRA (top row) and QISS bSSFP MRA (bottom row) in the brain. (a) Axial maximum intensity projection images show that QISS FISS MRA avoids signal loss in the left middle cerebral artery apparent with QISS bSSFP MRA (arrow). (b) Sagittal reformations show that QISS FISS MRA avoids artifact from off-resonance and out-of-slice magnetization that is seen with QISS bSSFP MRA (arrow).

Discussion: Radial QISS-based MRA leveraging a FISS readout reduced flow and off-resonance artifact compared with a bSSFP readout, with reduced saturation artifact compared with a FLASH readout. Due to its reduced sensitivity to artifacts relating to rapid systolic flow, the radial FISS readout approach appears to have particular merit for ungated MRA, but may also be beneficial for gated acquisitions because of improved fat suppression. Further work is needed to optimize the approach in various angiographic applications.

References: [1] Koktzoglou I, Edelman RR. Proceedings of the 25th Annual Meeting of the ISMRM, Honolulu, 3959; 2017. [2] Edelman RR et al. Magn Reson Med. 2010 Apr;63(4):951-8.

Funding: NIH grants R01 HL130093 and R21 HL126015.



— Dara KraitchmanValidation of MRA and CBCT to Evaluate Response to Stem Cell Therapy in a Rabbit Model of Peripheral Arterial Disease

Validation of MRA and CBCT to Evaluate Response to Stem Cell Therapy in a Rabbit Model of Peripheral Arterial Disease

Y. Xu, MD1, Y. Fu, PhD2, S. M. Shea, PhD3, T. Ehtiati, PhD4, B. A. Wasserman, MD2, Y. Qiao, PhD2, andD. L. Kraitchman, VMD, PhD2

1Department of Radiology, The First Affiliated Hospital of NanJing Medical University, NanJing, JiangSu, CHINA; 2 Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD, USA;

3Department of Radiology, Loyola Medical Center, Chicago, IL, USA; 4Siemens Medical Solutions USA, Inc., Baltimore, MD, USA

Purpose: In this study, we sought to determine whether MRA could be used to determine changes in vessel size as a response to mesenchymal stem cell therapy in a rabbit model of peripheral arterial disease (PAD).Methods: All animal studies were approved by the institutional animal care and use committee. Endovascular occlusion was performed in rabbits (n=7) using platinum coils in distal left superficial femoral artery (SFA) from a carotid artery approach (1). Distal aorto-iliac and femoral MRA and digital subtraction angiography (DSA) Cone-Beam Computed Tomography (CBCT) were performed on a 3T MRI scanner (Siemens TIM Trio) and flat-panel X-ray angiographic system(Siemens AXIOM Artis), respectively, prior to SFA occlusion, and at 10 and 17 days post-occlusion. 3D Time-of flight (TOF) MRA was acquired in the axial plane with multiple overlapping slabs using a T1-weighted fast spoiled gradient-echo sequence. Imaging parameters were as follows: 30 ms TR; 3.69 ms TE; 18° flip angle (FA); 238 Hz/pixel bandwidth (BW), 0.6 X 0.4 X 0.6 mm3 voxel size; and 7 m 24 s acquisition time. A 3D contrast-enhanced (CE) MRA was then acquired in the coronal plane with the following parameters: 4.27 ms TR; 1.73 ms TE; 18° FA; 510 Hz/pixel; BW; 0.4 X 0.4 X 0.8 mm3

voxel size; and a 31 s per acquisition scan time during IV injection of diluted 0.1 ml/s gadobenate dimeglumine(Multihance; Bracco Diagnostics, Inc., Princeton, NJ). CBCT was acquired using the vendor preset (8s DSA; 240° total projection angle at 0.5° projection increment; 42Omnipaque 350 mgI/mL; GE Healthcare Inc, Princeton, NJ) IV injection. CBCTs were reconstructed using the vendor software at 0.37 X 0.37 X 0.37 mm3. As both TOF MRA and DSA-CBCT were in the axial plane, no image post-processing was performed. The coronal CE-MRA was reconstructed in the axial plane using a multiplanar reconstruction tool in Vesselmass (Division of Image Processing, Leiden University Medical Center, Netherlands).

Quantitative vessel area measurement was derived semi-automatically from the edge detection tool in VesselMass based on the transluminal attenuation of signal intensity. Vessel area was measured at: 1. the terminal abdominal aorta 6 mm above the aortic bifurcation; 2. within the bilateral proximal external iliac artery (EIA) 6 mm below the iliac bifurcation; and 3. 6 mm below the SFA bifurcation. SNR and CNR were determined on the baseline images in five rabbits.

Values are reported as mean ± SD. Changes in vessel area over time and CNR between techniques were compared using an ANOVA. Inter-observer agreement in vessel area measurements from baseline scans was assessed using an intraclass correlation coefficient (ICC). Correlation among TOF MRA, DSA-CBCT, and CE MRA was assessed using a Pearson correlation coefficient. A Bland-Altman analysis was performed to determine whether there was any systematic bias in favor of either the MRA techniques or CBCT in the vessel area evaluation at baseline. Statistical analyses were performed using SPSS commercial software (version 13, Chicago, IL). A P value < 0.05 was considered statistically significant.Results: No animal exhibited clinical signs of PAD despite SFA occlusion. CNR for CBCT, TOF-MRA, and CE-MRA were 39.6 ± 14, 31.81± 8.09, and 22.3 ± 10.49, respectively. CNR was significantly lower for CE-MRA as compared to CBCT and TOF-MRA. Inter-observer agreement for vessel area measurement was high regardless of imaging technique (ICC=0.997 for CBCT, 0.999 for TOF, and 0.992 for CE-MRA). At baseline, vessel area measured by CBCT decreased from the abdominal aorta (11.66 ± 3.36 mm2) to the EIA (5.16 ±1.01 mm2) to the SFA (1.72 ± 0.18 mm2) as expected.Similar values were obtained for vessel measurements by TOF-MRA and CE-MRA. Bland Altman analysis showed a bias towards smaller vessel size by MRA than CBCT (0.37 ± 1.2 mm2 mean difference CBCT vs. TOF and 0.77 ± 1.16 mm2

CBCT vs. CE-MRA). The vessel areas in the right SFA did not change over time. However, the area of the left SFA proximal to occlusion increased significantly from baseline to ten days with CBCT and TOF-MRA (P=0.008 for CBCT and P=0.04 for TOF-MRA) but not by CE-MRA. No further changes in vessel area were observed from ten to 17 days post-occlusion. Discussion: CNR was reduced in CE-MRA relative to other techniques. Reformatting of the coronal CE-MRA images into the axial plane may have further degraded image resolution resulting in less ability to determine the size of the smallest vessels that might be associated with angiogenesis or vessel dilation due to regenerative therapy. Vessel area measurements showed a high agreement between CBCT and MRA with a slight bias towards larger vessel size by CBCT, which had the highest spatial resolution of the three techniques. In the current study, there is a suggestion that vasodilation proximal to the occlusion occurs relative early as part of the angiogenic response. However, the ability to determine response to therapy with MRA without the use of contrast agents would be attractive for gauging the response to stem cell therapy.References:1. Liddell RP, Patel TH, Weiss CR, et al. Endovascular model of rabbit hindlimb ischemia: a platform toevaluate therapeutic angiogenesis. J Vasc Interv Radiol 2005; 16:991-998.



— Joseph LeachMRI/MRA Based Models of Abdominal Aortic Aneurysm Mechanics

MRI/MRA Based Models of Abdominal Aortic Aneurysm Mechanics Joseph Leach MD, PhD; Chengcheng Zhu PhD; David Saloner PhD; Michael D. Hope MD Department of Radiology and Biomedical Imaging, University Of California, San Francisco

Purpose: Abdominal aortic aneurysms (AAA) are common and often lethal when they rupture. Patient-specific mechanical stress analysis could help to better identify at-risk AAAs warranting early intervention. Much progress has been made basing such analyses on CT imaging. MRI however offers unique capabilities to delineate intraluminal thrombus heterogeneity, to image inflammation using USPIOs, and to elucidate physiologic boundary conditions using 4D-flow and cine imaging, all features of interest in our group’s ongoing prospective study on AAA progression (n>50).1 Similar to other imaging-based mechanical analyses, AAAs are imaged in a loaded state, subjected to systemic blood pressure. As a first step toward a comprehensive MRI-based modeling of AAA mechanics, the relative merits of three common methods to account for this pre-loaded state are considered.

Methods: Contrast-enhanced MRA data (1.3 mm isotropic) of three thrombus-free AAAs were used to construct 3D finite element representations of the aneurysmal vessel wall. Three methods found in the literature to account for a loaded imaging configuration were employed: 1 - IMG) Assume the imaged geometry is unloaded; 2 - SS) Determine a “shrinking factor” using a representative cross-section of the AAA, and displace the inner and outer wall boundaries using this factor in a near volume-conserving way to approximate a “no-load state” (NLS) such that the pressurized NLS recaptures the imaged geometry; and 3 - BI) Use a “backwards incremental” finite element procedure to estimate the NLS by prescribing simulated forward displacements in reverse until local and global convergence is achieved.2 Nonlinear, large deformation analysis using 8-node linear hexahedral elements with uniform wall thickness 1.5 mm, an incompressible hyperelastic material model, inlet/outlet fixation, and patient-specific blood pressures was performed using the ABAQUS solver.

Results: The SS and BI methods use single-slice (2D) and global geometric information (3D) respectively to approximate the NLS, achieving volume conservation to the order of ~3% and solver tolerance (<<0.1%). The error of the pressurized NLS using IMG, SS, and BI methods, presented as the mean and max distance between the pressurized NLS and the imaged diastolic geometry, are listed in the Table. For AAA-1 and AAA-2, cine imaging through the aneurysm belly allowed comparison of the simulated displacement to the measured luminal circumference. Despite small introduced errors at multiple modeling steps, and 2D versus 3D approaches to approximating the NLS, both SS and BI methods predicted diastolic and systolic luminal circumferences in similar agreement with cine measurements, with ~1-4% error in diastole. Maximum intensity projection MRA data and systolic Von Mises stress at the luminal surface are shown for AAA-2 in the Figure, revealing key differences related to the three methods.

Discussion: The three methods to account for a loaded imaged vessel have important effects on computed wall deformation and stress. Common trends were seen for the AAAs studied. Assuming an unloaded imaged vessel (IMG) resulted in increased deformation, and artificially smoothed the geometry, giving a more uniform stress field. The shrinking-factor (SS) method used here is an adaptation of the method of Tang et al.3 While it is quick to implement and results in better geometric accuracy, it also leads to smoothing, ties global behavior to that of an arbitrary cross section, and has limitations for surface-based and multi-component modeling, important when considering thrombus. The backward incremental (BI) method minimizes smoothing and better captures curvature-related stress peaks, avoids assumptions on local-global behavior, and is naturally volume conserving, but is more time consuming to implement. The BI method is also better suited to more sophisticated fluid-structure interaction (FSI) modeling, as the accurate lumen volume will avoid artificial reductions in velocity and wall shear stress seen with IMG-method type assumptions. As not only average stress magnitudes, but also peak stress locations were seen to vary depending on the method used, careful consideration must be given when comparing wall stress to local features like aneurysm growth, inflammation, or thrombus deposition. Our data suggest that CINE imaging may be of limited value for calibrating and/or validating such methods, possibly because diastolic-to-systolic displacements are small and hard to measure. While both SS and BI methods had similar agreement with cine-measured circumference changes, they resulted is substantially different displacement errors (Table) and stress fields (Figure).

References: 1) Zhu C, et al. European Radiology 2017, May 27(5) 1787-1794 2) Riveros F et al. Ann Biomed Eng 2015, 43(9): 2253-22643) Tang D et al. Biomed Eng Online. 2009, 8:15

Error Mean (max) in mm AAA-1 AAA-2 AAA-3

IMG 1.5 (2.9) 0.84 (1.7) 0.8 (1.9) SS 0.3 (1.0) 0.31 (1.1) 0.38 (1.3)BI 0.03 (0.32) 0.02 (0.1) 0.03 (0.2)



— Tim LeinerCardiovascular MR Image Segmentation in Congenital Heart Disease Using a Dilated Convolutional Neural Network



— Rui LiIntegrating a Novel Low-rank Model with Parallel Imaging, to Enable Real time 4D-flow MRI



— Bo LiFast Carotid Artery MR Angiography with Compressed Sensing Based Three-dimensional Time-of-Fight Sequence

Fast Carotid Artery MR Angiography with Compressed Sensing Based Three-Dimensional Time-of-Fight Sequence

Bo Li 1,2, Hao Li 3, Li Dong 4

1 Center Laboratory, The Third Affiliated Hospital of Nanchang University, 330008, Nanchang, P.R.China 2 Department of Radiology, The Third Affiliated Hospital of Nanchang University, 330008, Nanchang, P.R.China

3 Department of Radiology, University of Cambridge, CB2 0QQ Cambridge, UK 4 Department of Radiology, Beijing Anzhen Hospital, Capital Medical University, 100029, Beijing, P.R.China

Purpose: Three-dimensional (3D) time-of-flight (TOF) is widely performed to depict vessel morphology and detect carotid artery thrombus.However, 3D TOF with high spatial resolution requires prohibitively long scan time, probably leading to patient motion such as swallowing, respiration, and neck movements during such a long scan time (1). Compressed sensing (CS) acceleration method has attracted wideattention due to its ability to recover an image from data sampled below the Nyquist frequency without degrading image quality (2).Therefore, in this study, we combined CS with a spoiled 3D TOF sequence to produce fast carotid artery MRA. We investigated thefeasibility of the fast 3D carotid artery imaging method at a 3T MR scanner.

Materials and Method: After institutional review board approval and written informed consent, seven healthy volunteers (three females and four males, age 62 ± 11 years) and one patient (females, age 75 years) with carotid artery stenosis were recruited in this study. CS-3D TOF Scans with 1- to 5-fold acceleration were carried out. The scan times at 1, 2, 3, 4 and 5-fold acceleration were 6 min, 3 min, 2 min, 1.5 min, and 72 s, respectively. To effectively generate hyper-intense vessel, a pseudo-sequential phase encoding order was developed, Because the reason is that SPEO generates a uniform k-space shift while phase encodings are acquiredsequentially from one edge of k-space to the other, and theimpact on the image quality due to the eddy currents could be negligible (3), as shown in Fig. 1. A CS reconstruction algorithm was used to recover dataset (2). The blood signal-to-tissue ratio (BTR) was used as a measure of blood signal intensity. The BTR is calculated by BTR = 100×Sblood/T, where Sbloodis the mean signal intensity of blood and T is the mean signal intensity of a muscle tissue. And two board-certified radiologists with at least 5 years of experience in vascular MR imaging, who were blinded to the technique used, evaluate image quality for images at 1 to 5-fold acceleration.

Results: The mean and standard deviation (SD) of BTR are 136.96±15.37, 136.93±16.07, 136.71±16.51, 135.84±16.76 and 135.76±15.60 for accelerations of 1×, 2×, 3×, 4× and 5×, respectively. There were no significant differences between the fully sampled dataset and each under-sampled (P > 0.05 for all comparisons). Figure 2 depicts the axial and oblique reformatted images obtained from CS-3D TOF at 1×, 2×, 3×, 4× and 5× accelerations in a patient with carotid artery stenosis. Both axial and oblique reformatted images at 2× to 5× exhibit the comparable vessel morphology and contrast between blood vessels and background tissues to those of fully sampled images. And the under-sampled axial images provide similar delineation of calcifications to fully sampled images (see arrows in Fig. 2a and Fig. 2b). However, some calcifications at 5× acceleration shows lower contrast than those at 1× to 4× accelerations (see dashed arrow in Fig. 2a and Fig. 2b), and the depiction of the boundaries between these calcifications and surrounding tissues are blurred.

Conclusions: This technique provides excellent visualizations for carotid vessel and calcifications in a short scan time. It has the potential to be integrated into current multiple blood contrast imaging protocol and help to visualize arterial vessel and calcifications with high scan efficiency.

References: [1] Boussel L,et al. J Magn Reson Imaging 2006;23:413–415.[2] Lustig M,et al. Magn ResonMed 2007;58:1182–1195.[3] Bernstein MA, et al. Handbook of MRI pulse sequences. 2004. p.318.

Fig. 1. The colored solid circles represent the random samples in the 3D k-space. The blue and orange groups perfectly match the sequential phase-encoding order. The green, purple and red groups approximately coincide with the sequential order. The numbers in the colored solid circles show the order in which that group is filled.

Fig. 2. Representative axial (a) and oblique reformatted (b) images obtained from CS-3D TOF at 1- to 5-fold acceleration in a patient with carotid artery stenosis.



— Jing LiuCardiorespiratory-resolved 3D Continuous First-pass Cardiac Perfusion MRI

Cardiorespiratory-Resolved 3D Continuous First-Pass Cardiac Perfusion MRI Jing Liu, Yan Wang, David Saloner, Karen Ordovas

University of California San Francisco, San Francisco, CA

Introduction: First-pass cardiac perfusion MRI provides important insights into coronary artery disease. However, routine clinical use is still limited by current technical challenges. Conventionally a small number of 2D slices are acquired with moderate spatial resolution in a single cardiac phase, and breath-hold is often required. Whole heart 3D perfusion MRI is desired but acceleration is essential given the limited first-pass perfusion window. In this study, we proposed a highly accelerated continuous 3D perfusion imaging without saturation preparation [1,2] and explore cardiorespiratory-resolved perfusion imaging. Methods: A undersampled [3-5] 3D gradient-echo sequence (SPGR) was applied on a 3.0T MR scanner (GE Medical Systems, Milwaukee, WI) using an eight-channel cardiac coil in short-axis view, FOV=34x25.5cm, TR/TE=2.8/1.2ms, FA=12°, BW= ±125kHz, image matrix=256×120, 1.3×2.1×8.0mm3, 16 slices. First-pass perfusion imaging was acquired for 1 minute with 20s delay following injection (Gd-DTPA, 0.1mmol/kg). 3D images were reconstructed at every 50 TRs (temporal resolution of 142ms, acceleration factor R=38). A profile of signal intensity across the left ventricle (LV) through time was exploited to derive respiratory motion information [5]. Two patients (55/85 years, 1 female/1 male) were tested with this cardiorespiratory-resolved 3D perfusion MRI method. Results: Fig.1 demonstrates the image intensity change through time (30s data showed, starting 10s after contrast injection). Fig.2 shows reformatted images with pre-contrast, RV, LV and myocardium enhanced at different time points. Fig.3 shows the images at peak enhancement (5 middle slices shown), at two cardiac phases and two respiratory phases. This indicates that this approach could provide a more comprehensive evaluation of myocardial perfusion. The effect of respiration on myocardial perfusion needs to be further investigated. Conclusion: We have achieved highly accelerated continuous 3D cardiac perfusion providing evaluation in systole and diastole, as well as in the inspiration and expiration phases. References: 1. DiBella E, et al. MRM, 67:609-13, 2012. 2. Sharif B, et al. MRM, 74:1661-74, 2015. 3. Liu J, et al. QIMS, 4(1):57-67, 2014. 4. Liu J, et al. NMR Biomed 29(1):15-23, 2016. 5. Liu J, et al. MAGMA, 2017.

Fig. 2 Images at four time points during perfusion with enhancement in differenttissues. ES: end-systolic, ED: end-systolic, RV: right ventricle, LV: left ventricle.

Fig. 1 3D images acquired continuously during free-breathing first-pass perfusion MRI without saturation or ECG triggers. Respiratory motion is derived from image data and allows respiratory-resolved imaging.

Fig. 3 Images (middle 5 slices out of 16) shown at the phase with peak enhancement.


1. My preferred presentation type is:

Oral >Electronic Poster >Traditional Poster

2. Keywords:

Dynamic contrast-enhanced, perfusion, cardiac, undersampling, acceleration

3. SynopsisThis study aims to develop a highly accelerated continuous 3D cardiac perfusion MR approach during freebreathing, which allows cardiorespiratory-resolved 3D perfusion MRI.



— Xian LiuSaccular Intracranial Aneurysm Wall Permeability and Shear Stress Distribution: a Further Insight into Rupture Pathogenesis

Saccular intracranial aneurysm wall permeability and shear stress distribution: a further insight into rupture pathogenesis.

Xian Liu1, Yu Chen1, Haikun Qi1, Peng Liu2, Le He1, Youxiang Li2, Rui Li1, Chun Yuan1,3, Huijun Chen1 1. Center for Biomedical Imaging Research, School of Medicine, Tsinghua University, Beijing, China.

2. Department of Interventional Neuroradiology, Beijing Neurosurgical Institute and Beijing Tiantan Hospital, China3. Department of Radiology, University of Washington, Seattle, Washington, United States

Purpose: Aneurysmal subarachnoid hemorrhage (SAH) is a leading cause of stroke disability and death in young patients, with an estimated initial mortality rate of 50% and up to 50% morbidity in survivors[1]. However, its pathogenesis in vivo remains unclear [2]. Reported as the most frequent cause of non-traumatic SAH [3], intracranial aneurysm (IA) is of great interest to researchers. Previous researches suggested many possible indicators of IA progression or rupture, such as the inflammation [4] and hemodynamic conditions [3, 5]. In recent studies [6, 7], researchers found that pharmacokinetic analysis of the IA DCE-MR images, which may quantify the IA wall permeability, may be an imaging biomarker associated with IA progression [6] and rupture [7]. However, its relationship with hemodynamic conditions remains unclear. In this study, we aimed to explore the relationship between wall permeability and the hemodynamic conditions of IA. Methods: After written informed consent obtained, 17 patients (6 males, mean SD age: 51.77 16.53 years) with unruptured saccular cerebral aneurysms IA detected by proceeding CTA examination were recruited. MR imaging: All patients were scanned on a 3.0T whole-body MR scanner (Achieva TX, Philips, Best, The Netherlands) with a 32-channel head coil. The MRI protocol included: 3D TOF sequence for subsequent scans localization, 4D flow MRI and 3D DCE-MRI. The further parameters of 3D PC MRI and DCE MRI were shown in Table 1. Image analysis: For DCE-MRI, the extended Kety/Tofts model [9] was used to generate the transfer constant ( ) map. A DCE-ROI covering the highest region outside but adjacent to the IA wall across all the slices was placed by one neuroradiologist blinded to patient information for each case, after pixels with blood signal contamination ( > 0.5) excluded[6]. For 4D flow data, wall shear stress (WSS) magnitude and 3D oscillatory shear index (OSI) were calculated with a validated method [10, 11]. Since we only choose one slice from DCE images for each case in analysis, the corresponding image plane were found from 4D flow images and were analyzed. The circumference of the IA in the selected slice were split to 12 sections for each case, and the WSS magnitude and 3D OSI were calculated for each section. These sections could be classified into 2 groups: group 1, sections correspond (adjacent) to the DCE-ROI with high values, reflecting the hot spot of IA wall permeability; group 2, other sections without hot spot. Statistical analysis: To investigate the relationship of the hot spot of IA wall permeability ( ) and the hemodynamic conditions inside IA, independent-sample T test was performed to compare the WSS and OSI between two groups. Results: Totally 204 sections from 17 patients were classified into 2 groups: 69 sections in group 1, while 135 segments in group 2. Fig 1 shows a typical case of registered 4D flow image and excessive values distribution, lower WSS and higher OSI can be seen for the sections near the IA wall permeability ( ) hot spot in this case. Overall, sections in groups 1 have significantly lower WSS magnitude than group 2 (0.460 0.058 vs. 0.6280.032 , p<0.01, Fig 2a). Also, the 3D OSI of sections in group 1 were significantly higher than group 2 (6.923 0.996 vs. 3.3700.443 %, p<0.005, Fig 2b). Discussion: In this study, high region outside but adjacent to the IA wall, which should reflects the hot spot of IA wall permeability [6, 7], was found spatially related with lower WSS magnitude and higher 3D OSI. Previous investigation had found that low WSS was associated with IA rupture area [3]. Our results further suggested that the pathogenesis of IA rupture might be an interaction of IA wall permeability and abnormal hemodynamic conditions. Thus, IA wall permeability could be a potential method for IA rupture risk assessment. References: [1] Lazzaro M.A. et al., J. Neurointerv. Surg. 2012, 4: 22–26. [2] Miyamoto T. etal., J. Cereb. Blood Flow Metab. 2016,. [3] Frösen J. et al., Acta Neuropathol.2012, 123: 773–786.[4] Chalouhi N. et al., J. Cereb. Blood Flow Metab. 2012,32: 1659–1676. [5] Lu G. et al., Am. J. Neuroradiol. 2011, 32: 1255–1261. [6] Vakil P. et al., Ajnr. 2015, 36: 953–959. [7] Qi H. et al., in: ISMRM., 2016. [8] Wetzel S. et al., Am. J.Neuroradiol. 2007, 28: 433–438. [9] Tofts P.S., JMRI. 1997, 7: 91–101. [10] Stalder A.F. et al, MRM. 2008, 60:1218–1231.[11] Meckel, S. et al.,Neuroradiology. 2008, 50: 473–484.

Table 1. Scan parameters

Fig 1. Image analysis results of one typical case.

Fig 2. Comparison of hemodynamic parameters.

p

have significantly lower 60 0.058 vs. 0.628D OSI of sections in group (6.923 0.996 vs. 3.370

egion outside but adjacentthe hot spot of IA wall



— Michael LoecherOptimizing TE and TR of 4D-Flow Acquisitions for Reduced Scan Times

Optimizing TE and TR of 4D-Flow Acquisitions for Reduced Scan Times Michael Loecher1, Patrick Magrath2, Eric Aliotta3, Daniel B. Ennis1,2,3

1Departments of Radiological Sciences, 2Bioengineering, 3Biomedical Physics, University of California, Los Angeles, CA, United States

INTRODUCTION: 4D-Flow MRI is an emerging clinical tool for simultaneously imaging vascular anatomy and hemodynamics. However, one of the major limitations for clinical use remains the long scan times, often on the order of 10-20 minutes. While there continues to be advances in accelerated (undersampled) acquisition techniques, methods to accelerate scanning by optimizing TE and TR times are still needed. For decades, the standard method for creating efficient bipolar gradients has been based on the work by Bernstein et al. [1]. This work, however, only allows for trapezoidal or triangular gradients, and does not account for optimization of the RF waveform, the use of balanced flow encoding for three-directional velocities. Particularly with high performance gradients, the maximum slew rates cannot be achieved without triggering peripheral nerve stimulation (PNS) limits, so the slew rates are derated, despite the fact there might only be short durations during the TR where slew rates need to be decreased to satisfy PNS constraints. This work aims to asses a series of optimization methods to reduce the TE and TR of 4D-Flow exams. THEORY: Four optimization techniques were used: 1) VERSE optimization was applied to the RF waveform and slice select gradient to maintain the slice profile and time bandwidth product (TBW) in a reduced amount of time. Previous work from our group has shown this to be effective and to produce no significant error in flow measurements [2]. 2) Convex optimization of the gradient waveforms was used to select the shortest possible gradients of arbitrary shape [3]. As in previous work, the convex optimizer was bound by hardware limits on gradient amplitude and slew rate, plus target gradient moments (M0, M1). Herein we also add a PNS [5] constraint. 3) Independent shifts (asymmetric encoding) of M1 (maintaining ΔM1) along thex, y, and z axes were optimized simultaneously. 4) Gradient waveforms were calculated inphysical coordinates to fully use the gradient hardware, rather than derating by √3 as in therotationally invariant case.METHODS: Gradient waveforms were simulated assuming hardware with: Gmax = 80 mT/m, Slew rate = 200 T/m/s, and PNS limits as in [5]. Relevant sequence parameters (affecting M0 and M1): 7 cm slab thickness, 8° flip angle, BW = 450 Hz/px, no partial Fourier or asymmetric echo, and an axial slab profile. For comparison values, a reference sequence was used that contains optimizations as in [1] with symmetrically balanced velocity encoding. The reference sequence de-rates on each individual axis to account for PNS limits. A range of resolutions (M0) and Vencs (M1) were used to simulate waveforms with our proposed optimized method and compared to the reference sequence. RESULTS: Figure 1 shows the gradient events prior to the readout for the optimized method and the conventional approach with Venc = 80 cm/s and 1.0mm resolution. In this example, the TE is reduced from 3.75 ms to 2.75 ms (27% reduction) and TR was reduced from 6.61 ms to 5.25 ms (21% reduction). Figure 2 shows TE and TR reductions over a range of parameters where TE reductions range from 20% to 35% and TR reductions range from 17% to 26%. DISCUSSION: Using a series of optimization techniques, the TE and TR of 4D-flow exams were substantially reduced in theoretical simulations. We are currently implementing the techniques described here in-line on a scanner for real-world validations and comparisons. Besides saving on scan time due to decreased TR, the decreased TE should also boost SNR due to reduced T2* decay, though this will most likely only be significant with contrast. Convex optimization is particularly effective when combined with high performance gradients, where PNS becomes just as significant as slew rate or gradient amplitude limits. Shifting the M1 of the encoding matrices improves sequence efficiency, but shifting away from symmetric balanced encoding could lead to more intravoxel dephasing in turbulent flow regions, which needs to be considered when modifying the encoding matrix. Performance over a wider range of parameters also needs to be investigated, particularly the use of asymmetric echoes, partial Fourier, and non-Cartesian trajectories. CONCLUSION: 4D-Flow scan times can potentially be reduced by a significant amount (2-5 minutes for common scanning parameters), by applying a more complete RF and gradient waveform optimization approach. REFERENCES: [1] Bernstein et al. "Minimizing TE in moment-nulled or flow-encoded two-and three-dimensional gradient-echo imaging" JMRI 1992. [2] Magrath et al. “Design and Validation of a Minimum Time Verse Pulse for 4D Flow MRI” ISMRM 2016. [3] Middione et al. "Convex gradient optimization for increased spatiotemporal resolution and improved accuracy in phase contrast MRI" MRM 2014. [4] Schulte, et al. "Peripheral nerve stimulation-optimal gradient waveform design" MRM 2015.

Figure 1: Pulse sequence diagram for a single TR of a the optimized (blue) and conventional (green) sequences. Stimulation estimates are also shown. The optimized method has a shorter TE and TR, and PNS levels are still within limits (1.0)

Figure 2: TE (top) and TR (bottom) reductions as compared to the conventional methods. Greater reductions are seen with higher resolutions and higher Vencs



— Daniel LudwigTime-resolved Three-dimensional Phase-contrast (4D-flow) MRI of the Portal Circulation Before and After Branch Portal Vein Embolization

Time-resolved three-dimensional phase-contrast (4D-flow) MRI of the portal circulation before and after branch portal vein embolization

Daniel R Ludwig1, Tyler J Fraum1, Joseph W Owen2, Nael E Saad1, Kathryn J Fowler1

1Mallinckrodt Institute of Radiology, St Louis, MO 2University of Kentucky College of Medicine, Lexington, KY

PURPOSE: Among patients with hepatic malignancy, branch portal vein embolization (PVE) is increasingly utilized to promote hypertrophy of the future liver remnant (FLR) prior to curative partial hepatectomy. We evaluated the feasibility of measuring PVE-induced hemodynamic changes in the portal circulation with time-resolved 3D phase-contrast (4D-flow) MRI. Furthermore, we sought to assess whether conservation of flow is maintained after PVE and whether changes in flow can predict increases in FLR volume.

METHODS: Ten patients with hepatic malignancy were enrolled prior to PVE. 4D-flow MRI of the upper abdomen (velocity-encoded gradient, 30 cm/s) was performed prior to (pre), 24 hrs after (early-post), and 1 mo after (late-post) PVE. The 4D Flow software package (Siemens) was used for image post-processing (Fig 1). Conservation of flow was assessed at the portosplenic confluence (PSC), main portal vein (MPV), and portal bifurcation.

RESULTS: Pre-PVE flow at the MPV, portal bifurcation, and PSC were 12.8 ± 4.4 ml/s, 12.7 ± 3.1 ml/s (mean error of 15.6% v. MPV), and 11.3 ± 4.2 ml/s (mean error of 25.8% v. MPV), respectively. Furthermore, flows within the MPV and portal bifurcation were strongly correlated (R2 = 0.79, p = 0.004). Flow in the non-embolized branch portal vein increased following PVE (10.4 v. 4.5 ml/s for early-post v. pre, p < 0.001; 13.5 v. 4.5 ml/s for late-post v. pre, p = 0.007). Conservation of flow was not maintained after PVE, as flow within the non-embolized branch portal vein was significantly lower than flow within the MPV (11.8 v. 14.4 ml/s, p = 0.04). Increase in flow in the non-embolized portal vein branch late-post PVE demonstrated a moderate but statistically insignificant correlation (R2 = 0.27, p = 0.36) with increase in volume of the FLR at 1 mo after PVE.

DISCUSSION: 4D-flow MRI is feasible for detecting PVE-induced hemodynamic changes in the portal circulation. Conservation of flow within the non-embolized branch portal vein was not maintained after PVE, suggesting the development of shunting, collateralization, and/or incomplete embolization. Further work is needed to ascertain whether changes in portal hemodynamics after PVE can predict increases in FLR volume.



— Kai LudwigPlacental Perfusion MRI: ASL FAIR and Ferumoxytol DCE in the Rhesus Macaque

Placental Perfusion MRI: ASL FAIR and Ferumoxytol DCE in the Rhesus Macaque Kai D. Ludwig1, Sean B. Fain1,2,3, Sydney Nguyen4, Thaddeus G. Golos4,5, Scott B. Reeder1,2,3,6,7, Ian M. Bird5, Oliver

Wieben1,2, Dinesh M. Shah5, Kevin M. Johnson1,2 Departments of Medical Physics1, Radiology2, Biomedical Engineering3, Comparative Biosciences4, and Obstetrics &

Gynecology5, Medicine6, Emergency Medicine7 at the University of Wisconsin-Madison, Madison, WI, USA Purpose: Characterizing placental vascular function is crucial to understanding the placenta’s role throughout pregnancy and identifying dysfunction in diseased states. Placental perfusion deficiencies impede nutrient exchange between the maternal and fetal blood1 and an early-pregnancy MRI assessment of placental vascular function would be valuable to predict outcomes and personalize treatments. Non-contrast arterial spin labeled (ASL) MRI methods are promising for safe evaluation of placental perfusion in utero2; however, the quantitative accuracy of ASL in the placenta is uncertain. Here, we evaluate ASL flow-sensitive alternating inversion recovery (FAIR) with tag modification to assess placental intervillous perfusion in a pregnant rhesus macaque animal model and compare with ferumoxytol dynamic contrast enhanced (DCE) MRI. Methods: Five healthy, pregnant rhesus macaques, all late second trimester (99.8±5.8 days), were imaged at 3.0T (MR750, GE Healthcare) with a 32-channel coil. ASL imaging used respiratory-triggering, FAIR labeling, and a single-shot FSE readout. 90° outer volume suppression (OVS) RF pulses were applied above and below the ASL imaging plane after FAIR preparation to truncate the tag (label time=1s, post-label delay=1s, 4mm slices, and 20 control/tag pair images). A 3D T1-weighted spoiled gradient echo (DISCO) sequence acquired dynamic volumetric data (TR=4.8ms, 68 slices 2mm thick, 5.0s temporal res., flip=12°) throughout injection of 4mg ferumoyxtol/kg diluted with saline (AMAG Pharmaceuticals). ASL FAIR tagged and control images were co-registered, separately averaged, then subtracted to generate a perfusion-weighted difference image. 3D DCE volumes were registered to the 2D ASL slice using Advanced Normalization Tools and DCE time curves were fit to a Fermi function in MATLAB (MathWorks) on a voxel-wise basis. Contrast arrival times (50% max.) were compared to the ASL difference image for each placental voxel using box plots and a Wilcox-rank sum test was performed between groups where p<0.05 was deemed to be statistically significant. Results: Fig. 1 shows an axial T2-weighted anatomical reference image of the macaque bi-lobed placenta (highlighted). After subtraction of the mean ASL FAIR tagged and control images, several localized regions of intense signal in the difference image (arrows) are seen within the placental tissue with predominately noise elsewhere. DCE MRI of the ferumoxtyol infusion enables direct measurement of contrast arrival time to placental tissue. Fig. 2 demonstrates heterogeneous contrast arrival times with localized regions of in-flow. This can be observed in the serial axial DCE slices (arrows), the DCE time curves of voxels in ‘early’ or ‘late-enhancing’ regions, and the contrast arrival time map with arrival times on the order of 10s of seconds [1-60s]. In corresponding slices on DCE and ASL, similar regions of early contrast arrival and high perfusion signal ASL were observed. This spatially correlation was statistical significance as shown in Fig. 3. Discussion: Blood delivery to the placenta is detectable using both ASL FAIR and ferumoxytol DCE in pregnant rhesus macaque placenta. The maternal utero-placental spiral arteries are likely being identified in regions of high ASL perfusion and early arrival times from ferumoxytol DCE. The observed extended arrival time from ferumoxytol DCE are similar to those observed by Gd DCE in the rhesus macaque3. ASL FAIR may be limited by extended transit times to placental tissue beyond the immediate vicinity of the maternal utero-placental spiral arteries. References: [1] Krishna, Bhalerao. J of Obs and Gyn of India. 2011. [2] Derwig I, et al. Placenta. 2013. [3] Schabel et al. MRM. 2015. Acknowledgements: NIH awards NICHD U01HD087216, P51OD011106, K24DK102595, UL1TR000427 and TL1TR000429, UW Departments of Medical Physics, Radiology, and Obstetrics and Gynecology for funding and GE Healthcare for research support.

Figure 1: ASL FAIR Perfusion. The bi-lobed placental tissue of the rhesus macaque is highlighted in an axial T2-weighted MR image corresponding to the ASL FAIR OVS slice location. Subtraction of the mean FAIR tagged and control image resulted in a perfusion-weighted difference image, shown as the overlaid color map. Regions of high local perfusion are observed within the placental tissue (arrows).

Figure 2: Ferumoxytol DCE. Serial T1-weighted DCE MR images (A) shows In-flow of ferumoxytol in separate functional lobules (arrows). A DCE time curve (B) depicts a large range of contrast arrival times depending on ROI position relative to the intervillous space as shown also on the contrast arrival parametric map (C).

Figure 3: Quantitative Comparison. A box and whisker plot, shown for one of the macaques, demonstrates that early contrast arrival regions from ferumoxtyol DCE have statistically significant correlation with high perfusion signal on ASL FAIR OVS within the placenta.



— Liliana MaAortic 3D Hemodynamics in Patients with Unicuspid and Partial Fusion Bicuspid Aortic Valve Disease

Aortic 3D hemodynamics in patients with unicuspid and partial fusion bicuspid aortic valve disease

1,2Liliana Ma, 1Alireza Vali, 1Carmen Blanken, Alex Barker, Jeremy Collins, James Carr, 1Susanne Schnell, 1,2Michael Markl

1Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, Il, USA2Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA

Purpose: Bicuspid aortic valve (BAV) disease has long been associated with increased incidence of cardiovascular events and aortopathy. Wall shear stress (WSS) has been implicated in aortic histopathologic changes and remodeling in these patients, and increased peak velocities (PV), which often coexist with increased WSS, are a sign of impaired valve function. Sievers type 2 BAV is a rare subtype of BAV disease, with an estimated incidence of 0.02%, that involves the fusion of more than two cusps, resulting in a functionally single-leaflet, or unicuspid, aortic valve (UAV, fig. 1).1, 2 Truly single leaflet valves are rare, but there are many partial fusion subtypes, hereafter referred to as the UAV group for simplicity (fig 1). The purpose of this study was to use 4D flow MRI to evaluate 3D aortic hemodynamics using WSS and velocity parameters in the largest cohort of type 2 BAV patients to date and compare these patients to the most common subtype of type 1 patients (right-left cusp fusion). Due to the more stenotic nature of UAV morphology, we hypothesized that the UAV cohort would have increased WSS and peak velocities (PVs) compared to the right-left (RL) BAV cohort. Methods: An IRB-approved retrospective query identified 32 UAV patients (6F/26M, age=45.9±11.8Y, mean ascending aortic (MAA) diameter =41.0±3.8mm, sinus of Valsalvadiameter (SOV)=41.0±5.3mm) diagnosed with four variants of UAV disease (fig. 1a-d) who underwent cardiothoracic MRI including 4D flow MRI of the thoracic aorta. As a control group, 32 RL fusion BAV patients matched for aortic dimensions (MAA and SOV diameter) and age were also included (7F/25M, age=49.2±11.9Y, MAA=41.1±3.7mm,SOV=41.1±5.1mm). 4D flow data wereacquired on a 1.5T/3T Aera, Skyra, or Avanto system (Siemens, Germany) with k-tGRAPPA, R=5, spatial resolution=2.8-3.4x2.1-2.4x2.5-3.5 mm, temporalresolution=36.8-39.2 ms and Venc=150-450 cm/s. A 3D segmentation of the thoracic aorta (Mimics, Materialise, Belgium) was created based on a calculated 3D phase contrast-MR angiogram (PC-MRA). Maximum intensity projections (MIPs, fig. 2c) of systolic velocities were used to visualize blood flow and quantify peak systolic velocities in 3 selected regions of interest: the ascending aorta (AAo), aortic arch (arch), and descending aorta (DAo). In addition, systolic 3D WSS along the entire aorta surface was calculated.4 Mean and top 2%systolic WSS were calculated in ten anatomical regions of interest (fig. 2d).3Results (table 1): Mean WSS in all four regions of the AAo (fig. 2d: 1,2,6,7)as well as the outer arch (8) were significantly increased in the type 1 cohort compared to the control (proxAAo inner(1): p=0.0002, rank-sum(RS).proxAAo outer(6) : p=0.028, t-test (tt). distAAo inner(2): p=0.0024, RS.distAAo outer(7): p=3.0e-05, tt. arch outer(8): p=0.0056, tt). Maximum 2% WSS was also significantly increased in the same regions. Peak velocity was significantly increased in all three aortic ROIs compared to the controls (AAo:p=3.2e-07, RS. Arch: p=8.8e-6, RS. DAo, p=4.1e-02, tt). Discussion: This study was the first to evaluate and compare aortic 3D hemodynamics in a large cohort of patients with rare type 2 BAV (functionally UAV) to type 1 BAV patients using 4D flow MRI. We found significantly increased WSS and peak velocities in the UAV compared to the RL fusion BAV patients, supporting our hypothesis that the abnormal anatomy in UAVs results in more severe values in markers of aortic remodeling and further impaired valve function. Future investigations will include subgroup analysis of the type 2 cohort (fig. 1), as well as evaluation of flow patterns/directions within groups to potentially identify reasons for specific areas of increased WSS. References: [1] Michelena, HI et al. Circ 2008. [2] Sievers H, et al. Euro JCTS 2016. [3] van Ooij P, et al. Ann. BME 2015.[4] Potters WV, et al. JMRI 2015.

Figure 1. UAV variants.a) entire RL/entire right-non (eRN) fusion. b)eRL/partial right-non (pRN). c) partial right-left (pRL)/eRN. d) pRL/pRN.

Figure 2. Workflow. a) 4D flow magnitude and 3D velocity-encoded images. b) 3D segmentation of the aorta. c) MIP. d) WSS quantification regions: 1,6 = proximal AAo; 2,7 = distal AAo, 3,8 = arch; 4,9 = proximal DAo; 5,10 = distal DAo. Regions 1-5 = inner, 6-10 = outer.

Mean WSS (Pa)

max 2% (Pa)

PV AAo(m/s)

Type

1 R

L (n=

32) 1 0.71±0.23 1.59±0.66 2.31±1.06

6 0.68±0.13 1.48±0.50 PV Arch2 0.57±0.24 1.05±0.47 1.31±0.407 0.84±0.31 1.28±0.56 PV DAo

8 0.54±0.12 0.99±0.33 1.16±0.23

Type

2, U

AV (n

= 3

2)

Mean WSS (Pa)

max 2% (Pa)

PV AAo(m/s)

1 0.84±0.16 2.42±0.82 3.92±1.006 0.77±0.17 1.98±0.60 PV Arch2 0.71±0.20 1.42±0.33 1.79±0.52 7 1.17±0.26 1.94±0.49 PV DAo 8 0.67±0.22 1.36±0.42 1.31±0.32

Table 1: WSS and peak velocity data.blue=type 2, grey = controls). 1,6,2,7, 8 correspond to the regions in figure 2.



— Jeffrey MakiFinding the Optimal Injection Strategy for Contrast-enhanced MR Angiography

°

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— John OshinskiCircumferential Heterogeneity of Aortic Wall Displacement and Strain Assessed with Cine DENSE MRI

Circumferential heterogeneity of aortic wall displacement and strain assessed with cine DENSE MRI

John S. Wilson1, John Oshinski1,2 1Department of Radiology, Emory University, Atlanta, GA, USA

2Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA

Introduction: Local vascular wall mechanics play a key role in the maintenance and remodeling of the aortic wall, and may influence aortic wall rupture vulnerability in the setting of dissection and aneurysm. Patient-specific aortic wall displacements have been quantified in-vivo using displacement encoding with stimulated echoes (DENSE) in the aortic arch [Haraldsson, JCMR 2014]. However, wall strain is the quantity that is most biologically relevant as it has been related to cellular signaling and vascular remodeling [Califano, J Biomech 2010]. In this study, we acquired cine DENSE imaging to determine 2D in-plane displacement of the aortic wall, and from the displacement field calculated circumferential strain at 3 locations in the aorta. We hypothesized that locations of maximum displacement would not be co-localized with locations of maximum wall strain.

Methods: Transverse, ECG-gated, 2D, spiral cine DENSE images were acquired on a 3T Siemens MRI (Trio or Prisma) in 18 healthy volunteers at three aortic locations: infrarenal abdominal (IAA), descending thoracic (DTA), aortic arch (AA). Images were acquired over the cardiac cycle to quantify displacement in the phase-encoding and readout directions (resolution = 1.3 x 1.3 x 8 mm, TE = 1.2 ms, TR= 16 ms, = 0.17-0.25 cycle/mm). Using in-house Matlab code, wall motion was tracked and Green strain was calculated using a quadrilateral interpolation function. Time and displacement smoothing, overlapping sectorization, and reference point averaging were employed to reduce noise while preserving regional heterogeneities in displacement and strain.

Results: At all 3 locations, systolic aortic wall displacement and circumferential wall strain were heterogeneous. In the infrarenal abdominal aorta, maximum displacement occurred in the anterior direction in the anterior wall opposite the spine, however, maximum circumferential strain occurred in the lateral walls, figure 1. In the descending thoracic aorta, displacement is more complex due to cardiac motion, with primary displacement toward the left lung and/or anterolaterally toward the left ventricle. As was seen in the infrarenal aorta, circumferential strain in the descending thoracic aorta occurs in the lateral wall and is not co-localized with locations of maximum displacement. In the aortic arch, displacement was directed toward the left apical lung, but maximum circumferential wall strain occurred at a localized region between the spine medially and the pulmonary artery inferiorly. As expected, an inverse correlation of maximum or average displacement was seen with biological age,

Conclusion: Cine DENSE MRI is a viable technique for assessing patient-specific aortic wall kinematics in- vivo. Local aortic displacement and strain are heterogeneous and vary depending on aortic location, surrounding structures, and patient-specific characteristics, such as age. Our results show that areas of maximal wall displacement are not co-localized with regions of maximal strain. Quantification of these heterogeneities may provide new insights into regional mechanobiological stimuli and provide novel metrics for assessing patient specific aortic remodeling and vulnerability.

Figure 1. Representative displacement vectors (top row) and circumferential Green strain (bottom row) in the aortic wall at the three locations examined: infrarenal aorta (27 y.o.), descending thoracic aorta (30 y.o.), and aortic arch (38 y.o.). In the infrarenal aorta, displacement is maximum in the anterior wall, but strain is maximum in the lateral walls. Similar results are seen in the descending thoracic aorta. In the aortic arch, displacement was more uniform but maximum strain was often very localized.



— Onur OzyurtIntegration of ASL into Stereotactic Radiosurgery of AVMs

Integration of ASL into Stereotactic Radiosurgery of AVMs

Onur Ozyurt1, 2, Alp Dincer2, Selcuk Peker3, Cengizhan Ozturk1

1Bogazici University, Institute of Biomedical Engineering, Istanbul, Turkey; 2Acibadem University, Neuroradiology Research Center, Istanbul, Turkey; 3Koc University Hospital, Department of Neurosurgery, Istanbul, Turkey.

Purpose: To test whether the combined use of 4D arterial spin labeling angiography (4D ASL) and contrast-enhanced magnetic resonance angiography (4D CE-MRA) can work as a prospective alternative to digital subtraction angiography (DSA) for the delineation of the arteriovenous malformation (AVM) nidus in stereotactic radiosurgery (SRS) planning.

Methods: We have implemented a custom 4D ASL sequence and a proof-of-concept software tool to integrate 4D ASL data into SRS planning. Ten AVM patients were scanned at 3T. Preparation part of 4D ASL included four pre-saturation pulses [1], a FOCI pulse [2] and a post-saturation pulse. A segmented 3D gradient spoiled FLASH readout was used with voxel sizes of 1x1x2 mm. Depending on the size of nidus, number of slices ranged from 12 to 24. Eight temporal phases, 120 msec temporal resolution (ie, covers between40–1000 msec after labeling) was obtained. 4D ASL imaging times rangedbetween 3:38 and 6:26. For 4D CE-MRA, TWIST [3] sequence was used withvoxel size 0.6 x 0.6 x 1.6 mm, 1 slab and 32 axial slices per slab and 1.43seconds temporal resolution. MR fiducial positions (Fig. 1a-b) are necessary fortransforming of images to stereotactic frame of reference. However, in 4D ASL,subtraction eliminates fiducial signals (Fig. 1c). To restore the MR fiducialsignal, control image was used to draw and remove a region of interest (ROI)that included only the patient’s head (Fig. 1d). The resultant fiducial-onlyimages were then superimposed on 4D ASL (Fig. 2c and e).

Two observers independently contoured niduses in two separate sessions. Reference niduses were contoured using DSA, 4D ASL, and 4D CE-MRA. Test niduses were contoured using 4D ASL and 4D CE-MRA only. Reference and test niduses from both observers were compared in terms of volume, distance between centers of volumes (dCOV), and the Jaccard index (JI).

Results: Maximum intensity projections (MIPs) of 4D ASL data from an AVM patient are given in Figure 2. Figure 2 is for demonstration only, since the nidus contouring were performed on slice data. In nidus volume comparisons, excellent intra-observer and inter-observer agreements were obtained (intraclass correlation coefficients: 0.99 and 0.98, respectively). Median dCOV, JIs between reference and test niduses were 0.55 mm, 0.78 for Observer 1 and were 0.6mm, 0.78 for Observer 2. None of the dCOV and JI parameters varied significantly among the delineation methods or the observers (P = 0.84, P = 0.39).

Discussion: Our preliminary results indicate that reproducibility of the target volumes with high agreement levels is achievable without using DSA. The combined use of high temporal resolution 4D ASL and high spatial resolution and vessel-to-background contrast 4D CE-MRA provided sufficient spatiotemporal angiographic information for the delineation of AVM niduses. ASL was able to bring the high temporal resolution component to the AVM nidus delineation, which was thought to be unique to DSA. Therefore, the proposed relatively less invasive MRI set could be considered an alternative to DSA; but before being used in routine SRS planning as the replacement for DSA, additional studies with larger patient groups need to be performed [4].

References: [1] Golay X et al., MRM 2005 [2] Ordidge RJ et al., MRM, 1996 [3] Vogt FM et al., ISMRM 2007 [4] Ozyurt O et al., JMRI, 2017



— Davide PicciniAutomated Cardiac Resting Phase Detection in 2D Cine MR Images for Acquisition Window Selection in Coronary MRI: Preliminary Results

Automated Cardiac Resting Phase Detection in 2D cine MR images for Acquisition Window Selection in Coronary MRI: Preliminary Results

Piccini D1,2,3, Demesmaeker R1, Vincenti G4, Masci PG, Kober T1,2,3, and Stuber M2,5 1Advanced Clinical Imaging Technology, Siemens Healthcare AG, Lausanne, Switzerland, 2Department of Radiology, University Hospital (CHUV) and University of Lausanne

(UNIL), Lausanne, Switzerland, 3LTS5, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland, 4Division of Cardiology and Cardiac MR Center, University Hospital of Lausanne (CHUV), Lausanne, Switzerland, 5Center for Biomedical Imaging (CIBM), Lausanne, Switzerland

PURPOSE. In coronary MR angiography (MRA), synchronizing the EGC-triggered imaging sequence with a period of minimal myocardial motion (resting phase) is of utmost importance. As the average displacement of the coronary arteries during a 120ms time period can be as high as 6mm [1], timing imperfections in the ECG synchronization can lead to strong blurring and sub-optimal image quality of the MRA dataset. The preselection of the resting phase is usually performed manually by expert users, based on visual assessment of a 2D-cine dataset acquired previous to the MRA [2]. Although some algorithms for automated detection of the periods of minimal myocardial motion were previously proposed [3,4], these studies were only applied to phantoms and volunteer data. Here, a new prototype algorithm for automated detection of the myocardial resting phase is proposed and tested on a patient population on clinical cardiac MRI data. METHODS. Data acquisition: The cine datasets for the 2-chamber, 3-chamber, and 4-chamber views in N=10 subjects were randomly selected from the patient database of the local cardiac MRI center. Acquisitions were performed on a 1.5T clinical scanner (MAGNETOM Aera, Siemens Healthcare) with parameters: 2D bSSFP, spatial / temporal resolution 1.2x1.6mm2 / 40ms, slice thickness: 8mm, TR/TE: 2.4/1.2ms. Automated extraction of cardiac motion parameters: All 30 image series were first pre-processed using a pixel intensity normalization. Then, for each pair of consecutive images in one series, the difference images were computed as the magnitude of the difference of their gradient magnitudes. Such difference images are ideally zero when borders are not moving. Finally, the Frobenius norm was calculated for each difference image as a representation of the overall amount of motion. This parameter is directly linked with the overall heart motion at each cardiac phase and can be represented as a 1D motion curve. Detection of the cardiac resting phases: A threshold-based region growing algorithm was applied on the cardiac motion curve to determine two sets of cine frames with the least amount of motion. First, the systolic and diastolic minima were extracted by automated peak detection. Then, a threshold (TH) was calculated as a percentage of the amplitude difference between these minima and the local maximum between systole and diastole. This threshold was optimized in a subset of M=18 datasets, where a manual selection of the cine frames corresponding to the resting phases was performed by two experienced cardiologists. Threshold selection: The problem of assigning each cine frame to a resting phase was considered as a statistical test, with the ground truth being the manual selection by one of the readers. For TH ranging from 0.00 (0%) to 1.00 (100%) in steps of 0.01, true positives (TP) and true negatives (TN) were computed. The maximum positive predictive value (PPV=(TP+TN)/M) was used to select the optimized threshold. Validation: The resting phases automatically selected with the optimal threshold were compared with those manually selected in the remaining Q=12 datasets. The manual selection of the second reader was also compared to that of the first reader for reference. Validation results were reported as sensitivity and specificity. RESULTS. Motion curve extraction and automated selection of the frame with minimal cardiac motion in both systole and diastole was successful for all datasets (Fig.1). The optimal threshold was selected at TH=0.32 with corresponding maximum PPV=84.44%. The validation step resulted in sensitivity and specificity at 73.2% and 90.6%. Comparable results were obtained when considering the comparison between readers with values of 78.3% and 80.1%. DISCUSSION. The automated selection of the cardiac resting phase showed very good correspondence to the manual selection in our patient cohort. While there was no specific patient selection criterion in this study, we speculate that the threshold could be optimized for different beat morphologies of different patient cohorts. An image quality comparison of the coronary MRA acquisitions obtained using either manual or automated acquisition window selection will be performed in a future prospective study. An automated selection algorithm could decrease operator-dependency when performing coronary MRA acquisitions and consequently increase the ease of use of this imaging technique which could thus be available to a wider range of users. References: [1] Hofman et al, JMRI, 8:568-576 (1998); [2] Wang et al, Radiology, 218:580-585 (2001); [3] Jahnke et al, JCMR, 7:395-399 (2005); [4] Ustun et al, AJR, 188:W283-W290 (2007).

Fig. 1: Automated cardiac motion estimation. A 4-chamber time series is displayed side by side with the respective difference images. The overall signal in the series of difference images is minimal in correspondence with the resting phases at end-systole and mid-diastole. This is very well represented by the cardiac motion curve on the right, obtained by calculating the Frobenius norm of the difference images.



— Nils PlankenBileaflet Mechanical Aortic Valves do not Alter Shear Stress or Aortic Diameter

Bileaflet mechanical aortic valves do not alter shear stress or aortic diameter

Farag ES a, Schade EL a, van Ooij P b,, Boekholdt SM b, van Kimmenade R d, Nederveen AJ b, de Mol BAJM a, Kluin J a, Planken RN b

a Department of Cardiothoracic Surgery, Academic Medical Center, Amsterdam, the Netherlands b Department of Radiology and Nuclear Medicine, Academic Medical Center, Amsterdam, the Netherlands

c Department of Cardiology, Academic Medical Center, Amsterdam, the Netherlands d Department of Cardiology, Radboud University Medical Center, Nijmegen, the Netherlands

Purpose Surgical aortic valve replacement (AVR) is the preferred treatment for severe aortic valve disease and is performed by replacing the native aortic valve by a either a mechanical or bioprosthetic aortic valve.1 Mechanical valves are designed to last a lifetime, but it is possible that their bileaflet design induces changes in blood flow patterns and wall shear stress (WSS) in the ascending aorta resulting in progressive aortic dilatation. The aim of this study was to examine the effects of bileaflet mechanical aortic valves on WSS in the ascending aorta using time-resolved three-dimensional flow magnetic resonance imaging (4D flow MRI).

Methods Fourteen patients with mechanical aortic valve prostheses and ten healthy individuals with no history of cardiac disease were prospectively enrolled in a single center cross-sectional pilot study. All participants underwent cardiac and respiratory-gated sagittal 4D flow MRI and a non-contrast enhanced MRA of the thoracic aorta on a 3 Tesla MRI scanner. Peak systolic hemodynamic parameters (mean and peak velocity, WSS) and mid-ascending aortic diameters were assessed in the ascending aorta.2 Three-dimensional heat maps were used to quantify abnormally elevated WSS between patients and healthy individuals (figure 1).3

Figure 1: Individual WSS maps are compared with reference atlases to identify areas of abnormal WSS

Results Mean time after AVR was 3.2 ± 1.3 years. Peak blood flow velocity in the ascending aorta was higher in the mAVR group than in the control group (2.73 ± 0.81 m/s versus 1.83 ± 0.49 m/s, p < 0,01). No differences in mean velocity were found between groups (0.53 ± 0.13 m/s versus 0.57 ± 0.10 m/s, p = 0.467). Furthermore, no differences in mid-ascending aortic diameters were found between the mAVR group and controls (3.59 ± 1.69 cm versus 3.08 ± 1.13 cm, p = 0.39).

Compared with healthy individuals, the mAVR group displayed no significant differences in peak WSS (2.27 ± 0.75 Pa versus 2.01 ± 0.49 Pa, p = 0.299). Abnormally elevated WSS was present in 1.5% ± 1.8% of the wall of the ascending aorta in mAVR patients. Abnormally decreased WSS was present in 0.6% ± 0.9% of the wall of the ascending aorta.

Discussion The present study shows no difference in ascending aortic diameter WSS. The hemodynamic effect of the bileaflet mechanical aortic valve prosthesis is therefore comparable to the native aortic valve with respect to WSS and ascending aortic diameter. Our results suggest that there is no indication for routine or aggressive replacement of the ascending aorta at the time of mechanical AVR.

References 1 Wollersheim, L.W., Li, W.W, De Mol, B.A. Current status of surgical treatment for aortic valve stenosis. J Card Surg. 2014;29(5):630-7 2 Potters W V., van Ooij P., Marquering HA et al. Volumetric arterial wall shear stress calculation based on cine phase contrast MRI. J Magn Reson Imaging 2015;41(2):505–16. 3 van Ooij P., Potters W V., Collins J., et al. Characterization of abnormal wall shear stress using 4D flow MRI in human bicuspid aortopathy. Ann Biomed Eng 2015;43(6):1385–97.


Synopsis [ max 100 words ]

Mechanical valves are designed to last a lifetime, but their bileaflet design may induce changes in blood flow patterns and wall shear stress (WSS) in the ascending aorta resulting in progressive aortic dilatation. In this 4D flow MRI study we investigated the effect of bileaflet mechanical aortic valve implantation on blood flow characteristics in the ascending aorta. No significant alterations in WSS distribution were seen after mAVR compared to healthy individuals with no history of cardiac disease. Our results suggest that there is no indication for routine or aggressive replacement of the ascending aorta at the time of mechanical AVR.



— Qin QinCerebral Arteriography and Venography Using Velocity-selective Pulse Trains

Cerebral Arteriography and Venography Using Velocity-Selective Pulse TrainsWenbo Li1-2, Feng Xu1-3, Michael Schär1, Jing Liu1,4, Taehoon Shin5, Peter van Zijl1-2, Bruce Wasserman1, Ye Qiao1,

Qin Qin1-2

1Johns Hopkins University, Maryland, USA; 2Kennedy Krieger Institute, Maryland, USA;3Children’s National Medical Center, Washington DC, USA; 4Guizhou Medical University, China; 5University of Maryland, USA;

Purpose: TOF is the most established non-contrast-enhanced (NCE) MRA for cerebral applications but suffers from limited spatial coverage and poor delineation of slow flow. The emerging velocity-selective (VS) MRA technique allows for large spatial coverage and slow-flow sensitivity (1,2). VS-MRA has shown great promise in its initial application for cerebral arteries but with sensitivity to B1 inhomogeneity and limited separability between arteries and veins. In this study, we aim to develop a 3D NCE MRA sequence which allows arteriography and venography using the newly constructed velocity-selectivesaturation (VSS) pulse train for improved immunity to B1 inhomogeneity. Methods: The VSS pulse train is composed of a series of 9 excitation pulses (10° each), interleaved with pairs of 180° hard pulses for refocusing and velocity-encoding gradient lobes (Fig. 1a). Previously, the excitation pulses in the VSS pulse trains werehard pulses (1,2), which were sensitive to B1+ inhomogeneities,leading to inhomogeneous saturation of background tissues. To tackle this issue, a 10° optimized composite (OCP) pulse (Fig. 1b) was generated using an optimal control method (3). Fig. 1c displays the Mz responses of VSS pulse trains employing hard pulses (the 1st column) and OCP pulses (2nd column), respectively, over velocity (x-axis) vs. B0 off-resonance (the 1st row) and B1+ (2nd row). The substitution with 10° OCP pulses significantly mitigates the dependence of the tissue saturation on the B1 effect.For arteriography or venography, a spatially selective inversion(SSI) pulse was applied to the entire intracranial region or the cervical region with a delay time (Tinv) inserted before the VSS pulse train (Fig. 2). At the time of the acquisition, the inverted magnetization of downstream venous blood or upstream arterial blood recovers to the nulling point, resulting in an arteriogram or venogram, respectively.3D arteriograms, venograms and combined angiograms of 6 healthy volunteers (36+/-9 y, 3F) were obtained using a 3T Philips scanner (a 32-channel head coil for reception). The turbo field echo (TFE) was used for axial acquisition:FOV=180 180 220mm3; voxel size=0.7 0.7 1.4mm3;TR/TE=7.5/2.4 ms; flip angle=7°; SENSE=2 2; total scan time=5min. The combined angiograms with 10° hard excitation pulses in VSS pulse trains were obtained for comparison. VSS prepared arteriography was added on two patients during their referred MR angiographic exams for suspected intracranial arterial stenosiswith matched TOF protocol for comparison (0.55 × 0.55 × 1.10 mm3, 77 mm, 5.5 min). Results: The MIP images of VS MRA angiograms acquired with 10° hard pulses and OCP pulses are shown in Figs. 3a and 3b,respectively. The background tissues were more uniformly suppressed when OCP pulses were used. The arteriograms (Fig. 3c) depict all major cervical and intracranial arteries and their small branches. The venograms (Fig. 3d) delineate all the major intracranial and cervical veins. Fig. 4 shows one clinical example of VS MRA in a patient withocclusion of the left M1 segment, which is consistent with the corresponding TOF images. In addition, VS MRA better depictssmall distal branches with slow in-plane flow.Discussion: We have shown improved reduction of B1 sensitivity using VSS pulse trains and developed protocols for 3D arteriography and venography by placing SSI pulses before the VSS-prepared acquisition to selectively null signals from venous or arterial blood. The whole-brain angiography protocols are promising and will be further evaluated in patients with various cerebrovascular disorders.References: (1) Qin, Q, et al. MRM, 2016, 75:p1232; (2) Shin, T, et al. MRM, 2016, 76:p466; (3) Liu, H, et al. MRM, 2011, 66:p1254;

Fig.1: (a) VSS pulse train using hard pulses or OCP pulses as the 10° excitation pulses with corresponding RF waveforms (b). (c) The simulated Mz-V response of VSS at various B0/B1 conditions.

Fig.3: MIP angiograms using 10° (a) hard pulses and (b) OCPpulses as the excitation pulses in VSS pulse train, (c) arteriogram and (d) venogram acquired using the inserted SSI pulses.

Fig.4: Coronal MIPs of a 46-year-old male patient with occlusion ofthe left M1 segment (arrows): (a) VS MRA; (b) TOF MRA.

Fig.2: The VS MRA with the VSS pulse train before the acquisitionand the SSI pulse applied for arteriography or venography.



— Aleksandra RadjenovicMyocardial Fractional Blood Volume Estimation Using Ultra Low Dose Ferumoxytol Enhanced MRI and Three-compartment Model of Water Exchange in Patients with Chronic Kidney Disease

Myocardial fractional blood volume estimation using ultra low dose ferumoxytol enhanced MRI and three-compartment model of water exchange

in patients with chronic kidney disease

D.Black1, S.Stoumpos1, M.Jerosch-Herold2, P.Gatehouse3, G.Jayasekera1, D.Kingsmore1, C.Berry1, P.Mark1, G.Roditi1,A.Radjenovic1

1 Institute of Cardiovascular and Medical Sciences, University of Glasgow and Greater Glasgow and Clyde NHS Trust, Glasgow, UK; 2 Harvard Medical School, Boston, USA; 3 Imperial College, London, UK

Background: Patients diagnosed with chronic kidney disease (CKD) frequently suffer from a range of comorbidities, and their cardiovascular system is often compromised. Central to this pathology is the impaired glomerular filtration, so these patients are not able to benefit from diagnostic imaging involving gadolinium based contrast agents (GBCA).Therefore, the intravascular contrast agent ferumoxytol is of particular interest in CKD as a potential alternative to GBCA. The benefits of ferumoxytol-enhanced magnetic resonance angiography (MRA) are already well established. However, the potential utility of ferumoxytol in the assessment of myocardial microvasculature is still insufficiently explored.Because ferumoxytol does not cross capillary walls, the observed changes in longitudinal relaxation time (T1) following intravenous administration enable estimation of myocardial fractional blood volume (FBV) from the ratio between the change of relaxation rates R1 = (1/T1) in myocardium and blood (FBV = R1myo/ R1blood) respectively,and assuming fast 1H exchange between intra- and extra-vascular spaces. However, this ratio is reduced, and FBV is significantly underestimated at higher concentrations of ferumoxytol, e.g. at doses used clinically for MRA (~4mg/kg),because 1H exchange is no longer sufficiently fast: blood capillaries perfuse two larger compartments - extracellular and intracellular. When R1 is high, limited water exchange between tissue spaces cause gradients of water relaxation within this complex system, as previously described[1]. Such water exchange processes, described by Hazlewood[2],and later investigated by Donahue[3], may explain the seemingly paradoxical reduction of FBV as the intravascular concentration of ferumoxytol is increased. One approach to overcoming this problem is to model the effects of water exchange. An alternative approach is to perform measurements of myo R1blood in the ultra-low dose range, where intrinsic R1 differences between intra- and extra-vascular space are small relative to the rate of water exchange. In this study, we compared FBV estimates obtained using both approaches.

Figure 1. An example of measured R1myo and R1bloodvalues, fitted model curve, estimates of FBV and kvi,and ultra low dose estimates FBV0.2 and FBV0.3.

Methods: Twelve patients with severe CKD were recruited following approval by the regional ethics board (7 male; median age 50 (28-72); BW = 77±17 kg; BMI = 28±5 kg/m2). Scanning was performed at 3T (Prisma, Siemens Healthcare). All patients received fractionated injections of diluted ferumoxytol (1:5), up to the maximal dose of 3mg/kg. Three initial aliquots each contained 0.3mg/kg, and were followed by a remaining dose of 2.1mg/kg. Before and after each injection, T1 maps of the mid-ventricular left myocardium were acquired using a modified Look Locker inversion recovery method (MOLLI). R1myo and R1blood values were recorded at each step.

Results: FBV estimated using a 3-compartment model was 0.11 ± 0.02, with a mean estimated vascular-interstitial exchange rate of kvi = 5.5 ± 2.2 [s-1]. Model assumptions included a fixed extracellular volume (ECV) of 0.3 and intracellular water lifetime of 100 myo blood estimates of FBV for 2 and 3 dose aliquots were FBV0.2 = 0.10 ± 0.02 and FBV0.3 = 0.09 ± 0.02, (corresponding to Cblood of up to 0.2 and 0.3 mM, respectively).

Discussion: The proposed model fitted our data well (e.g. Figure 1.). Estimates of FBV obtained in the ultra low dose range, after 2 or 3 dose aliquots (FBV0.2 and FBV0.3) were slightly lower than the model-derived FBV. The marginalFBV0.2 > FBV0.3, may indicate that limited water exchange already affects the Cblood within 0.2- 0.3mM range. Our model-based FBV estimates agree with previously reported values in healthy volunteers (0.12 ± 0.02, [4]). This is a surprising finding, suggesting that these CKD patients have intact myocardial microvasculature. On the other hand, FBV0.2 is 20% below the model-derived normal value in [4] and ~25% below their equivalent of FBV0.2 (~0.13± 0.02, estimated from scatterplot). Without direct comparison with healthy volunteers, we cannot exclude the possibility that the proposed water exchange model overestimates FBV and that ultra low dose FBV0.2, provides a more accurate estimate.

Conclusion: Ultra low dose estimates of FBV are similar to those obtained using modelling of water exchange over a wide range of concentrations, but seem to be more sensitive to pathology. Further work to improve understanding of these initial results could significantly extend the scope of ferumoxytol enhanced MRI as a method for myocardial tissue characterisation in a range of pathologies, including CKD.

References: [1] Kroeker RM & Henkelman RM, JMR, 1986; [2] Hazlewood CF et al, Biophys J, 1974; [3] Donahue KM et al. MRM 1996; [4] Chatterjee N et al, Proc. ISMRM 2015;

FBV0.2 = 0.098FBV0.3 = 0.094



— Amir Ali RahseparComprehensive Evaluation of Extracellular Volume Measurements and Myocardial Scar Detection by Late Gadolinium Enhanced Cardiac MR using Gadoterate Meglumine

Comprehensive Evaluation of Extracellular Volume Measurements and Myocardial Scar Detection by Late Gadolinium Enhanced Cardiac MR using Gadoterate Meglumine

Amir Ali Rahsepar, Ahmadreza Ghasemiesfe, Ryan S. Dolan, Monda L Shehata, Kenichiro Suwa, Monica Korell, Julie A Blaisdell, Nivedita K Naresh, Michael Markl, Jeremy D Collins, James C Carr

Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.

Introduction:

Late gadolinium enhanced cardiac MR (LGE-CMR) is the reference standard for myocardial scar evaluation. Additionally, CMR can detect microscopic scarring in patients suspected of having cardiac diseases by using extracellular volume fraction (ECV) mapping. Due to the recent introduction of Gadoterate Meglumine to the US market, we aimed to evaluate LGE- and ECV-CMR using this agent (gadoterate meglumine, Dotarem, Guerbet, France) compared with a more routinely used macrocyclic GBCA (gadobutrol, Gadavist, Bayer, Germany).

Methods:

40 subjects [61±11 years, 27 (67.5%) men] with suspected myocardial scar on LGE-CMR performed using 0.2mmol/kg gadobutrol were recruited for a research CMR scan using 0.2mmol/kg gadoterate meglumine. Research CMR scans were performed within an eight-week period using gadoterate meglumine. All clinical and research scans were performed on 1.5T MR scanners (Avanto/Aera, Magnetom, Siemens, Germany). Delayed enhancement imaging was performed 10 minutes after intravenous administration of GBCA. Quantitative assessment of myocardial scar was performed on LGE-CMR data on short-axis images using a conventional segmented gradient recalled echo phase-sensitive inversion recovery pulse sequence by using commercially available software (Circle 5.3, Calgary, Canada). The manual thresholding method was used to quantify the scar percentage. Qualitative scar analysis was performed by 2 observers scoring hyperenhanced myocardial scar on the 16-segment AHA model at LGE-CMR based on the area of scar per segment (0 = none, 1 =1–25%, 2 =26–50%, 3 = 51–75%, 4 = 76–100% of the segment area). Segmental ratings were summed across all 16 segments to derive a global scar score for each scan. Reader’s confidence in visualizing the scar tissue for each agent was recorded on a 5-point scale (1=poor, 2=fair, 3=good, 4=very good, 5=excellent). T1-mapping was performed using a modified Look-Locker inversion recovery (MOLLI) technique. Patient’s hematocrit was collected before the CMR exam. ECV was calculated for all subjects using the same software. Intraclass correlation coefficient (ICC) and the Wilcoxon signed rank test were used to check for reliability and differences in qualitative ratings between myocardial scar using the two GBCAs.

Results:

Overall, 40 subjects with various types and patterns of myocardial scar were enrolled in this study. Different scar patterns, including sub-epicardial, transmural and mesocardial, in different regions of myocardium were found. Representative LGE-CMR images from the same patient using gadobutrol and gadoterate meglumine are provided in Figure 1. Using Turboflash technique, percentage myocardial scar mass averaged 9.91±9.5 and 7.7±9.2 for gadobutrol and gadoterate meglumine, respectively. Intraclass correlation (ICC) showed excellent reliability (ICC=0.985) between the two GBCAs in quantifying LGE. Global qualitative segmental LGE scores showed a similar scar detection using gadobutrol vs. gadoterate meglumine (5.3±6.9 vs. 4.22±6.22, p>0.05). Reader confidence in scar visualization was similar between gadobutrol and gadoterate meglumine (4.51 vs 4.41, p>0.05). Among these 40 patients, 16 had T1-mapping for both the clinical and research scans. Average ECV for patients who had received gadobutrol and gadoterate meglumine were 28.41±4.88 vs. 28.46±4.73 with excellent reliability (ICC=0.979).

Conclusion:


Our results indicate that gadoterate meglumine has equivalent diagnostic accuracy to gadobutrol in quantitative and qualitative scar evaluation and for calculating ECV and identifying microscopic LV scar. Our results confirm that ECV value is independent of type of contrast agent and switching to a different contrast agent does not cause significant changes in ECV values. Additional studies are warranted to confirm our results in a larger patient cohort.

Figure 1. Short axis, 2-, and 3-chamber views of a patient with massive myocardial infarction 1.5-T scanner; gadoterate meglumine (left) and gadobutrol (right).



— Vitaliy RayzComparison of 4D-flow MRI Measurements to PIV and CFD Modeling



— Alejandro Roldán-AlzateVentricular Kinetic Energy in Healthy Volunteers Using Respiratory Gated 4D-flow MRI

Ventricular Kinetic Energy in Healthy Volunteers Using Respiratory Gated 4D Flow MRI David R. Rutkowskia,b, Christopher J. Françoisb , Alejandro Roldán-Alzatea,b,c

a. Mechanical Engineering, b. Radiology,c. Biomedical Engineering; University of Wisconsin, Madison, WI, USPurpose: Cardiac function can be evaluated with 4D flow MRI to monitor and manage heart disease.[1,2,3] One of these markers, ventricular kinetic energy, may be an early indicator of changes in cardiac efficiency.[4,5]

Developments in MR scanning procedures have also led to the capability of evaluating cardiac function in discrete phases of the respiratory cycle.[6] The purpose of this study was to examine the feasibility of ventricular kinetic energy and efficiency quantification and examine the differences in this metric between respiratory phases in healthy volunteers, with the intention of future application to pathological evaluation. Methods:MR Imaging: Fifteen healthy volunteers with no history of cardiovascular disease were included in this Institutional Review Board-approved and Health Insurance Portability and Accountability Act-compliant study. 4D flow MRI data were acquired with using PC-VIPR[7] on a clinical 3T scanner (MR750, GE Healthcare, Waukesha, WI). Scan parameters are described in previous work, and respiratory bellows were used for respiratory gating.[6] Ventricular Segmentation: Left ventricle (LV) volumes were segmented from the time averaged (TA) magnitude images using Mimics (Materialise, Leuven, Belgium)(Figure 1a) as described in past work.[8,9] LV fluid region cross-sections were manually segmented on axial slices across the ventricle volume each subject. KE Calculation: The kinetic energy (KE) within the ventricles was calculated in Matlab, using the standard formula for kinetic energy (k = ½ mv2). The velocity in each voxel of the ventricle region was obtained through out the cardiac cycle, and mass (m) was determined by multiplying the voxel volume by the density of blood. The KE values of each voxel within the segmented ventricle volume were then summed to determine the total KE within the ventricle throughout the cardiac cycle. Efficiency was defined as milijoules of ventricular KE per ml of aortic blood flow. This process was done for both respiratory datasets in all volunteers. Flow metrics and visualization were also obtained in the left ventricle and aorta using Ensight (CEI) (Figure 1b.). Statistical Analysis: The peak systolic and diastolic KE values, aortic KE values, and ventricular volumes were compared between inspiration and expiration phases using a student’s t-test with a significance level of 0.05.Furthermore, correlations between the measured parameters were analyzed using linear regression.Results: Among these 15 volunteers, mean peak systolic LV KE was 3.4 ± 1.9 mJ in expiration (exp) and 3.2 ± 1.6 mJ in inspiration (insp). Mean peak diastolic LV KE was 5.5 ± 1.7(exp) and 5.2 ± 2.3 mJ (insp). Neither systolic nor diastolic LV KE values showed significant 1-sided differences between respiratory phases(p=0.313,p=.122). Mean efficiency in systole was 0.0103±.004 (exp) and 0.0091±.003 (insp) and 0.2029±.115 (exp) and 0.1511±.055 (insp) in diastole, with units of mJ/ml of blood flow. Inspiration and expiration KE values were strongly correlated in systole (r = 0.89) and diastole (r=0.96), as were LV KE to Aortic Flow (r=.68(insp)) and (r=0.63 (exp)), and LV KE to Aortic KE in peak systole (r=0.66 (exp)). LV KE was also correlated to LV volume in systole (r=0.73 (insp), r=0.68(exp)) and diastole (r=0.55(insp) (r=0.54(exp)). Conclusion: In this study, we evaulated the efficiency of the left ventricle based on kinetic energy and aortic hemodynamics in healthy volunteers in discrete respiratory phases. In future work, these tools will be further developed and applied to pathological cases to provide insight into altered cardiac efficiency. References: [1] Hope MD. JACC Cardiovasc Imaging. 2011; [2] Markl M,. Int J Cardiovasc Imaging. 2016; [3] François CJ. J Cardiovasc Magn Reson. 2015; [4] Jeong D. J Thorac Cardiovasc Surg. 2015; [5] Kanski M. J Cardiovasc Mag Reson. 2015; [6] Schrauben, E.M.. J Magn Reson Imaging, 2014 [7] Gu T. AJNR, 2005; [8] Hussaini. JMRI, 2016 ; [9] Roldán-Alzate A. J Cardiovasc Magn Reson, 2014

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Figure 1.4D flow MRI analysis of a healthy left ventricle a) Ventricular segmentationand hemodynamic analysis plots b) Ventricular KE and Aortic flow visualization

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— Trisha RoyMRI Characteristics of Lesions Relate to the Difficulty of Peripheral Arterial Endovascular Procedures

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— Trisha RoyFrom Bench to Bedside: Validation of Native-contrast MRI Techniques to Characterize Popliteal and Tibial Chronic Total Occlusions from Critical Limb Ischemia Patients

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— Mark SchieblerInitial Experience with Velocity Selective Arterial Spin Labeling for Non-contrast Neurovascular Imaging

Initial Experience with Velocity Selective Arterial Spin Labeling for Non-Contrast Neurovascular Imaging

Susan L. Rebsamen1, James H. Holmes1, Zachary Clark1, Patrick A. Turski1, Mark L. Schiebler1, Prateek Sanan1, Kevin M. Johnson1,2 Departments of 1Radiology and 2Medical Physics, University of Wisconsin-Madison, Madison, WI

Purpose: Velocity selective arterial spin labeling (VS-ASL) is a technique for transit time insensitive, non-contrast perfusion and angiographic imaging [1-3]. Unlike the more common ASL techniques, the tagging module is targeted to be velocity rather than spatially selective. Thus, labeling can be effective in tortuous vessels without well-defined labeling planes andin slow or complex flow patterns. While, VS-ASL tagging is subject to other error sources including eddy currents, B1heterogeneity, subject motion and susceptibility artifacts; progress has been made in identifying these errors and subsequent strategies to minimize their impact. The goal of this work is to demonstrate our preliminary clinical experience utilizing a velocity selective ASL preparation for non-contrast 3D MRA/MRV and perfusion, with the ultimate goal of providing matched perfusion and angiography without the need for an exogenous contrast agent.

Materials and Methods: All subjects provided written consent under an institutional IRB protocol and imaging was performed on a 3T MR system. Velocity selective tagging was achieved with an eddy current and B1 insensitive tagging module [4]; where images are acquired with motion sensitizing gradients (Venc=2cm/s) inserted into an adiabatic T2-preparation module. Velocity selective imaging was interleaved with a control image acquired without explicit flow sensitization. For this work, control images were collected utilizing a T2-preparation (perfusion) and a novel a magnetization transfer (MT) preparation (angiography). Angiography imaging was accelerated utilizing an undersampled 3D radial trajectory [5], enabling 0.75mm isotropic resolution and whole head coverage in 5:14 (min: sec). Perfusion imaging was performed using the same preparation module with the addition of a 1.2s post label delay and background suppressionfollowed by a single shot fast spin echo acquisition (SSFSE).

Results: Non-contrast VS-ASL 3D MRA images depict both the cerebral arterial and venous vasculature. In addition, a component of signal from very low velocity CSF flow is also present. To counteract loss of signal in regions of high susceptibility a novel MT-preparation control may provide superior signal to noise ratio and overall decreased susceptibility effects compared to the initially implemented T2-preparation control preparation. Figure 1 shows representative perfusion(CBF) and angiographic images collected with the same VS-ASL tagging module, contrasting images collected in a young healthy subject with those from an older subject undergoing evaluation for suspected cerebral ischemia. Lower vessel density and blood flow are observed in the older subject (median CBF=47.7 vs. 58.4 ml/min/100g). These preliminary results demonstrate a relationship between decreased CBF and the number of angiographically visible vessels. This potentially indicates that some perfusion signal is “shine-through” from the large vessels and partially represents macroscopic flow rather than perfusion.

Conclusion: We have demonstrated that the application of VS-ASL for achieving non-contrast MRA/MRV and perfusion in the brain. VS-ASL has several advantages over othervolumetric non-contrast MRA techniques such as time-of-flight and phase-contrast imaging. Specifically, 3D-TOF MRA suffers from loss of signal related to in-plane directionality of flow and has poor sensitivity to slow flow. Likewise, PC MRA suffers from signal loss related to complex flow and relies heavily on velocity encoding parameters. Our initial results using VS-ASL, show this method to provide delineation of both arterial & venous flow without the need for intravenous contrast and is robust to artifacts from slow flow and complex vessel geometries.

References:[1] Wong E et al. Magn Reson Med 2006; 55:1334-134[2] Fan Z et al. Magn Reson Med 2009; 62:1523-1532[3] Zhang N et al. J Magn Reson Imaging 2016; 43:364-372[4] Guo J et al. Magn Reson Med 2015; 73:1085-1094[5] Johnson KM, et al. Magn Reson Med 2013; 70:1241-1250

Figure 1: Example images acquired in a young healthy subject (A) and a subject with an ischemic infarct (B). VS-ASLangiographic images show slow and fast moving blood, withsome background signal intensity due to the MT based control image. In subject B, there is a focal region of decreasedperfusion (CBF) observed within the right putamen small(arrow).



— Mark SchieblerPET-MR of a new Fibrin Binding Agent in a Porcine Model of Acute Pulmonary Embolism

PET-MR of a new fibrin binding agent in a porcine model of acute pulmonary embolism

ML Schiebler 1, T Schubert1,2, A McMillan1, K Johnson1, E Ehlerding ,B Oliveria3 , W Cai1, P Caravan 3,D Consigny1, C François, S Cho1

1- Department of Radiology, UW-Madison School of Medicine and Public Health2- Department of Radiology, Basel University Hospital

3- Martinos Center for Biomedical Imaging, Massachusetts General Hospital

Purpose: Create a porcine model for acute pulmonary embolism (PE) at angiography and test the binding of a new PET agent to fibrin (64Cu-FBP8) using a PET/MR device.

Materials and Methods: After animal use approval by IACUC, five 50 kg domestic swine were studied using a new method for the introduction of acute clot. We catheterized the LLL pulmonary artery and introduced silk suture material until a subsegmental pulmonary artery was occluded (PE generation procedure). After two hours of waiting for in-situ fibrin formation within the occluded vessel the animal was brought down to the PET/MR instrument for injection with the radiopharmaceutical (64Cu-FBP8) for imaging.(1) A total of 4 hours of continuous PET imaging (list mode) was performed along with multiple MRA exams.

Results: One animal was used to test the formation of PE without injection of the PET agent. Three animals were successfully imaged with the PET/MR machine. We found binding (high uptake at PET) of 64Cu-FBP8 to the area of in-situ thrombus formation (Fig.1). This was shown by increased PET activity within the occluded vessel and confirmed by contemporaneous MR angiography.(2) One of the five animals was not able to tolerate the PEgeneration procedure.

Discussion: We used a new radiopharmaceutical (64Cu-FBP8) which is a fibrin specific binding agent coupled to a cyclotron generated isotope of Cu that emits a positron. We successfully created a new large animal model for acute pulmonary embolism using silk suture. Also we were able to show that this fibrin specific PET radiopharmaceutical (64Cu-FBP8) works to bind the fibrin associated with this acute pulmonary embolism. Having a PET agent that binds fibrin will be of potential interest to those that wish to: (a) non-invasively titrate thrombotic therapy (complete clot lysis), (b) image acute pulmonary embolism in subjects allergic to iodinated contrast material and (c) help image occult sources of venous thromboembolism.

References:

1. Blasi F, Oliveira BL, Rietz TA, et al. Radiation Dosimetry of the Fibrin-Binding Probe Cu-FBP8 and ItsFeasibility for PET Imaging of Deep Vein Thrombosis and Pulmonary Embolism in Rats. J Nucl Med2015;56(7):1088-1093.

2. Bannas P, Bell LC, Johnson KM, et al. Pulmonary Embolism Detection with Three-dimensional UltrashortEcho Time MR Imaging: Experimental Study in Canines. Radiology 2016;278(2):413-421.

Figure 1: Ferumoxytol enhanced UTE MRA with embolus in LLL PA (arrow), (B) Simultaneous PET uptake in acute thrombus using 64Cu-FBP8, (C) Mirada combined overlay of A & B.



— Susanne SchmidVisualizing Small Arteries in the Brain Using Fluid Suppressed Balanced SSFP MR Angiography

Visualizing Small Arteries in the Brain using Fluid Suppressed Balanced SSFP MR Angiography

Susanne Schmid, M Louis Lauzon, Richard Frayne Biomedical Engineering, Radiology and Clinical Neurosciences, Hotchkiss Brain Institute, University of Calgary,

Calgary, AB, Canada; and Seaman Family MR Research Centre, Calgary, AB, Canada

Purpose: Image contrast in many MRA techniques relies on blood flow. Balanced steady-state free precession (bSSFP) is a pulse sequence with an inherently high signal-to-noise ratio, where image contrast is flow independent. Furthermore, high blood signal is obtained in bSSFP imaging due to the high T2/T1 ratio for blood. High blood-tissue contrast is advantageous for MRA but in the brain, the high signal contribution of fat and cerebral spinal fluid (CSF) poses a challenge. Here, we investigate the feasibility of a CSF-suppressed, inversion-recovery prepared bSSFP (IR-bSSFP) sequence for performing high-resolution angiography of the cerebral small vessels. A similar concept has been used to suppress synovial fluid in peripheral MRA in the ankle joint. [1]

Methods: To suppress CSF, an IR pulse similar to that used in FLAIR (fluid attenuated inversion recovery imaging), was applied to null the CSF. The inversion pulse was followed by a train of equally spaced bSSFP acquisitions with alternating flip angle. [1,2] To ensure CSF suppression, data were acquired with an interleaved, elliptic centric technique. The optimal imaging parameters were estimated using a Bloch equation simulation of this sequence. A 3D IR-bSSFP sequence was implemented and used to collect data on normal subjects using a 3 T scanner (Discovery 750; GE Healthcare, Milwaukee, WI) with flip angle = 75°, TR/TE = 4.0 ms/1.6 ms, TI = 800 ms, 1 mm partition thickness and an acquired matrix of 256 256 88. IR-bSSFP images were compared to a high-resolution time-of-flight (TOF) sequence (flip = 15°, TR/TE = 22 ms/2.4 ms).

Results and Discussion: CSF suppression was demonstrated: the IR-bSSFP sequence nulled CSF (Fig. 1a) compared to the conventional bSSFP sequence (Fig 1b). In addition, more blood vessel details were visualized in a volunteer with IR-bSSFP: TOF visualized two vessel segments (indicated by the arrow in Fig 2b) whereas IR-bSSFP depicts three vessel segments in the same region (Fig 2a). The IR-bSSFP results appeared had less blurring.

Conclusions: Interleaved elliptic centric IR-bSSFP sequences achieve good CSF suppression and have the potential for non-contrast enhanced MR-angiography of the cerebral small vessels. Future work should focus on further imaging parameter optimization, implementing fat suppression and artifact reduction strategies, specifically those artifacts resulting from the implemented elliptic-centric acquisition pattern.

Reference [1] Shin T, et al., Magn. Reson. Imaging, 2016; 75: 653.[2] Bangerter NK, et al., Magn. Reson. Imaging, 2011; 29: 1119.

Fig. 1: Axial view using a) IR-bSSFP with Bloch equation optimized imaging parameters (see text) and b) standard bSSFP.

Fig. 2: Close-up axial view of blood vessels with a) IR-bSSFP sequence and b) standard TOF MRA. Reconstructed matrix was 512 512 for both images.



— Michaela SchmidtLow-dose Dynamic CE-MRA Employing Iterative Reconstruction: Gains and Limitations

GRAPPA acceleration

sampling (A/B) in %

spatial resolution interpolated

temp. footprintIT TWIST TWIST

Hand vasculature 4 (PE) x 3 (PA) A10 B20 0.7 mm3 1.4 s 6.9 sLung vasculature 4 (PE) x 2 (PA) A15 B20 1.0 mm3 2.4 s 10.8 sBrain vasculature 4 (PE) x 2 (PA) A14 B10 0.8 mm3 1.1 s 10.0 s

Fig. 1: Acceleration, spatial and temporal resolution and temporal footprint (imageupdate rate for both equals temp. footprint IT TWIST) for the 3 different body regions.

Fig. 2: Representative cases of all body regions. Better visual SNRof IT TWIST compared to TWIST. Vessel ghosting in IT TWIST, especially for very high subsampling, is marked with yellow arrows.

Fig. 3: Time-signal curve: Compared to TWIST, ITTWIST shows a gain inpeak signal intensityduring first pass.

Fig. 4: Retrospectively under-sampled hand MRA. TWISTshows ghosting (see arrows).

Low-dose dynamic CE-MRA employing iterative reconstruction: Gains and Limitations

M. Schmidt1, C. Fellner2, B. J. Wintersperger3, Y. Fushimi4, T. Okada4,L. D’Errico3, W. Uller2, C. Forman1, F. Lugauer5, J. Wetzl5

1Siemens Healthcare GmbH, Erlangen, Germany; 2Institute of Radiology, University Hospital Regensburg, Regensburg, Germany; 3Department of Medical Imaging, University of Toronto, Toronto, Ontario, Canada; 4Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate

School of Medicine, Kyoto, Japan, 5Pattern Recognition Lab, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany;

Purpose: To compare conventional time-resolved angiography with stochastic trajectories (TWIST) [1] with an iterative reconstruction of the same datasets (IT TWIST) and to identify gains and limitations of highly accelerated, low-dose MRA in multiple applications and at three different medical centers.

Methods: In all subjects (11 patients with AVM in the hand, 11 thorax and 14 whole-brain MRA), data acquisition was performed with a highly accelerated TWIST sequence on clinical 3T scanners (MAGNETOM Skyra, Siemens Healthcare) after bolus injection of 1/5 dose of gadolinium-based contrast agent. The parameters used for the different body regions [2-4] are shown in Fig. 1. As described in [2], the acquired datasets were reconstructed twice: While view-sharing of one central (A) and multiple peripheral (B) k-space segments were utilized in conventional TWIST reconstruction using GRAPPA, in our prototype IT TWIST approach only two consecutive A-B pairs are needed for the reconstruction of each time step using temporal regularization. In the reconstructed images, visual assessment of vasculature in all body regions was performed. “Apparent SNR” of the vessel was measured with the mean signal intensity divided by the standard deviation in ROIs placed in the major hand artery. Full width at half maximum (FWHM) was calculated in time-signal curves in the distal pulmonary arteries. Reconstruction times were compared for both methods. Additionally, a fully-sampled hand MRA was acquired and retrospectively undersampled with the TWIST and Poisson Disc pattern with nearly identical acceleration to evaluate the influence of a dedicated incoherent sampling in the B segments on image quality.

Results and Discussion: The visualization and delineation of central arterial feeders and hand arteries was significantly improved by iterative reconstruction. This was confirmed by an improved vessel SNR by a factor of 2.71. While large vessels like main pulmonary artery or cortical vein showed only slight improvements, the grading scores for the small pulmonary and intracranial vasculature (ICA, M1, M3) improved significantly as shown in Fig. 2. For the distal pulmonary vessel, time-signal curve analysis (Fig. 3) shows a gain in peak signal intensity, which may be an effect of removing the need for view-sharing during reconstruction in IT TWIST. However, compared to a reconstruction time of 1:30 min for TWIST, IT TWIST required between 8:30 min for the hand and 35 min for the whole-brain MRA. Furthermore, the sampling pattern has not been adapted for compressed sensing and the high scan acceleration induced residual ghosting artifacts (see Fig. 2). An optimized sampling pattern may enable such high sub-sampling rates without ghosting artifacts. This could be confirmed in the retrospectively undersampled data shown in Fig. 4. While the images reconstructed with the TWIST sampling scheme show residual ghosting artifacts, these artifacts disappeared in the images retrospectively reconstructed with Poisson Disc sub-sampling.

References: [1] Lim RP et al.; AJNR29:1847-54; 2008. [2] Wetzl J et al.; MRM 77(2):833-40; 2017; [3] Fellner C et al.; ISMRM p. 2793; 2017; [4] Fushimi Y et al.; ISMRM; p.1417; 2017

TWIST Fully sampledPoisson

IT TWISTTWIST

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— Xin ShenVoxel-by-Voxel 4D-flow MRI Based Assessment of Reverse Flow in the Aorta

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— Zhang ShiCharacterization of the Vulnerable Intracranial Atherosclerotic Plaque Features by High Resolution MRI and a Quantitative Radiomics Approach

Characterization of the vulnerable intracranial atherosclerotic plaque features by high resolution MRI and a quantitative radiomics approach

Zhang Shi1, Chengcheng Zhu2, Xia Tian1, Xuefeng Zhang1, Jianping Lu1, Tao Jiang1, David Saloner2, Qi Liu1 1. Department of Radiology, Changhai Hospital, Shanghai, China

2. Department of Radiology and Biomedical Imaging, UCSF, San Francisco, CA, USAPurpose: Intracranial atherosclerosis is a major cause of stroke, and high-resolution magnetic resonance imaging (HR-MRI) of the vessel wall has been used to evaluate the plaque vulnerability. Although many studies have shown differences in radiological features between symptomatic and asymptomatic intracranial atherosclerotic plaques, quantitative image features (radiomics or texture analysis) have rarely been studied. This study aims to evaluate whether radiomic features derived from HR-MRI can differentiate symptomatic and asymptomatic plaques. Materials and Methods: Study population: 95 patients (Male 67; Female 28) with intracranial atherosclerosis in basilar artery (BA) underwent HR-MRI (pre and post-contrast T1 and T2 weighted). Image analysis: Atherosclerosis plaques from BA were extracted as the region of interest (ROI) for quantitative evaluation. Radiomics features including intensity, shape based feature and textures were analyzed. Textures includes gray level cooccurence matrix (GLCM), gray level run length matrix (GLRLM) and gray level size zone matrix (GLSZM). For each sequence (T1, T2, T1+C), 94 radiomic features were extracted1. As a reference, the diagnostic performance of traditional imaging features, including the degree of stenosis, plaque area, contrast enhancement and intra-plaque hemorrhage (IPH) was also evaluated and compared with this new radiomics approach. Statistical analysis: Univariate analysis was applied first to find possible variable that was associated with symptoms. P-values <0.05 were considered as statistical significant. Significant parameters were then underwent multi-variate analysis. To further quantify the texture features, supervised machine-learning methods were applied to classify symptomatic and asymptomatic plaques. Features in each sequence were selected during statistical analysis, those were set as input for the random forest training. The performance of each sequence was compared. Results: Of the 94 included patients (mean age 61.1±10.6 years; M:F=67:28), 73 had ischemic strokes (44 acute, 18 subacute and 12 chronic), and 21 were asymptomatic. As the univariate analysis shown in Table 1&2, there were 10 and 7 positive characteristics in T1 and T1+C respectively while none of the features in T2 images were statistically significant. Random forest shows different classification accuracy with different sequences. The reported area under the curve (AUC) of 6 features of T1 images was 0.86 and the 15 features of T1+C was 0.90 which was the maximum AUC (Fig 1). For traditional imaging features, only IPH was an independent marker of symptoms with an AUC value of 0.76. When combining both radiomics and traditional parameters, the AUC values were 0.89 (T1) and 0.94 (T1+C). Conclusion: Radiomic features derived from HR-MRI can be used to differentiate symptomatic and asymptomatic intracranial artery plaques, and the features from contrast enhanced T1 images have the best performance. Radiomic analysis provides additional value other than traditional imaging bio-markers with significantly improved diagnostic performance. Radiomics approach has the potential to improve the risk stratification of patients with intracranial atherosclerosis diseases. However, its prognostic value needs to be validated in larger scale longitudinal studies. References: 1. Aerts, Hugo JWL, et al. Nature communications (2014).

Table 1 Radiomic features from T1 images Symptomatic Asymptomatic p-value

shape_Maximum3DDiameter 5.28±1.42 4.57±1.07 0.015 shape_Maximum2DDiameterSlice 5.25±1.42 4.55±1.06 0.016 shape_Volume 40.08±24.13 30.17±18.81 0.046 shape_SurfaceArea 75.08±29.99 60.52±24.06 0.019 shape_Maximum2DDiameterColumn 4.52±1.36 3.85±0.98 0.016 glcm_MaximumProbability 0.05±0.02 0.04±0.01 0.044 glcm_Entropy 6.49±0.69 6.11±0.51 0.007 glcm_Energy 0.01±0.01 0.02±0.01 0.031 glrlm_RunLengthNonUniformity 102.89±62.18 76.11±42.24 0.031 glszm_ZoneEntropy 4.70±0.37 4.51±0.28 0.009

Table2 Radiomic features from T1+C images

Symptomatic Asymptomatic p-value

firstorder_Uniformity 0.06±0.02 0.07±0.02 0.006glcm_MaximumProbability 0.03±0.01 0.04±0.02 0.003glcm_Entropy 6.85±0.78 6.43±0.85 0.009glrlm_RunVariance 0.07±0.03 0.09±0.03 0.005 glszm_SmallAreaEmphasis 0.83±0.05 0.80±0.06 0.005glszm_SizeZoneVariabilityNormalized 0.66±0.08 0.61±0.10 0.004 glszm_IntensityVariabilityNormalized 0.06±0.02 0.07±0.02 0.007

Figure-1: ROC curves for differentiating

symptomatic intracranial plaques



— Monica SigovanEvaluation of Inflammatory Processes in Carotid Atherosclerosis Using 18F-NaF Enhanced PET/MRI: Preliminary Results

Evaluation of inflammatory processes in carotid atherosclerosis using 18F-NaF enhanced PET/MRI: preliminary results

Monica Sigovan1 Laura Mechtouff2, Nicolas Costes3, Philippe Douek1,4, Diane Collet-Benzaquen5, Norbert Nighoghossian1,2, Yves Berthezene1,6

1 University of Lyon CREATIS Laboratory, CNRS UMR 5220, Inserm U1206, INSA Lyon, France 2 Stroke Department, Hôpital Pierre Wertheimer, HCL, Lyon, France

3 CERMEP - Imagerie du vivant, Lyon, France 4 Department of Interventional Radiology and Cardio-vascular and Thoracic Diagnostic Imaging, HCL, Lyon, France

5 Laboratory of anatomy and cellular pathology, HCL, Lyon, France 6 Neuroradiology Department, Hôpital Pierre Wertheimer, HCL, Lyon, France

Purpose: Current anatomical criteria for plaque vulnerability, obtained from the most common imaging modalities, CT and MRI angiography, fail to provide information on disease activity. PET radiotracers are bridging this gap by detecting and quantifying pathophysiological processes associated with plaque vulnerability. Of these radiotracers, 18F-NaF targets an active process of calcification, which is initiated by an inflammatory process in the context of vascular disease. In the present study we aimed at investigating 18F-NaF uptake in carotid atherosclerosis using a hybrid simultaneous PET/MR system. Methods: 4 patients with identified carotid atherosclerosis (>50% stenosis by Doppler US) were imaged using a Siemens mMR 3T scanner. The MR acquisitions consisted of a 3D TOF, 3D T1 weighted SPACE sequence, and MRA performed during Gd first pass (DOTAREM, Guerbet). The T1-w acquisition was repeated after contrast injection to evaluate plaque uptake. The PET acquisition was performed centred on the carotid arteries 60 min after administration of 18F-NaF over a 15 min interval. Plaque composition was evaluated qualitatively in terms of presence of intra-plaque haemorrhage, calcifications and large lipid core. Plaque was manually contoured on the morphological MR images and the obtained volume of interest (VOI) was transferred to the corresponding PET data to measure standardized uptake values (SUV). Additionally an ROI was placed in the jugular vein on the contralateral side to compute tissue to background ratios (TBR). Results: Table. CT and MRI plaque morphological characteristics vs. 18F-NaF PET uptake

Patient No

Patient classification

CT/MRI morphology

Plaque volume (mm3) SUVmax SUVmean TBR

1 Symptomatic Large lipid core 692.7 2858 1204 0.89 2 Symptomatic Ruptured 921.8 1574 979 1.08 3 Asymptomatic Highly calcified 271.7 9695 4852 3.3 4 Asymptomatic Non calcified 330.2 9170 3375 1.7

Discussion: We present here our initial experience in imaging carotid atherosclerosis with a simultaneous PET/MR system. We found 18F-NaF uptake in the asymptomatic patients (TBR>1.5) presenting with high cardiovascular risk factors, in agreement with previous studies (1). As expected based on literature data, the strongest uptake was measured in the highly calcified plaque. Nevertheless, we observed a lack of co-localisation between other vascular macro-calcifications in the same patient and 18F-NaF uptake (Figure), supporting the hypothesis that uptake reflects an active calcification process (2). Furthermore, we did not observe 18F-NaF uptake in the symptomatic patients, particularly in the ruptured plaque. This might indicate that passive diffusion is not a mechanism for tracer accumulation. In order to validate our findings with the hybrid simultaneous system PET/MR, future work will focus on the attenuation correction comparison between MR based correction and CT based correction using attenuation maps derived from patients CT scans.

References 1. Derlin T, Wisotzki C, Richter U, et al. In Vivo Imaging of Mineral

Deposition in Carotid Plaque Using 18F-Sodium FluoridePET/CT: Correlation with Atherogenic Risk Factors. J NuclMed. 2011;52(3):362–368.

2. Derlin T, Richter U, Bannas P, et al. Feasibility of 18F-SodiumFluoride PET/CT for Imaging of Atherosclerotic Plaque. J NuclMed. 2010;51(6):862–865.

Figure. Representative images of a highly calcified plaque (top) and a lipid rich plaque (bottom) acquired

with a standard CT system (left) and a hybrid simultaneous PET/MR system (right). 18F-NaF uptake is visible in the highly calcified plaque. To be noted, uptake

was not colocalized with other calcified regions in the arterial wall.



— Roberto SouzaCommon Carotid Artery Lumen Segmentation from Cine Fast Spin Echo Magnetic Resonance Images

Common Carotid Artery Lumen Segmentation from Cine Fast Spin Echo MR Images

Lívia Rodrigues,1 Roberto Souza,1-4 Mari Boesen,2,3 Letícia Rittner,1 Richard Frayne,2,3,4 Roberto Lotufo1

1MICLab, FEEC, University of Campinas, Campinas, SP, Brazil 2Radiology and Clinical Neurosciences, Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada

3Seaman Family MR Research Centre and 4Calgary Image Processing and Analysis Centre, Foothills Medical Centre, Alberta Health Services, Calgary, AB, Canada

Purpose: Stroke is a common cause of death in the developed world. A non-invasive method for visualizing and quantifying carotid artery stenosis and plaque morphology is required in order to identify individuals who are at high risk of future stroke due to large vessel atherosclerosis. Here, we focus on the challenge of segmenting the common carotid artery (CCA) lumen, i.e., the interior artery wall, by applying morphological techniques to a temporal series of cine fast-spin echo (FSE) magnetic resonance (MR) images.[1] By segmenting the lumen over the cardiac cycle, we can then analyze its cross-sectional area, distensibility, and shape variation, which we hypothesize will correlate with the severity of atherosclerotic disease and stroke risk.[2] Our method combines max-tree area signature analysis with the tie-zone watershed transform.

Methods: The method is based on two assumptions. We assume 1) an a priori range for the carotid artery lumen diameter (4.3 mm to 7.7 mm), and 2) that the image grey-level intensities over time are self-consistent (guaranteed by the temporal constraints imposed in the image reconstruction process [1]). The method has four main steps: 1) Selection of the lumen centroid (by the user), 2) Identification of internal (lumen) and external (vessel wall) markers by max-tree filtering, 3) Application of tie-zone watershed transform on the gradient image using these markers, and 4) Classification of tie-zone pixels into carotid wall or background using a random forest algorithm. The test dataset consisted of nine normal subjects each scanned five times at 3 T (total of 45 cine FSE [1] acquisitions). We compared the resulting segmentation obtained from our method against a consensus obtained from three manual segmentations (the ground truth). Only the left CCA was assessed and sensitivity, Dice coefficient and false positive rate (FPR) metrics were calculated.

Results: Our method successfully segmented the lumen in all 45 (100%) cases. Fig 1 shows the results of our method in a representative subject. The average metrics were sensitivity: 0.917 ± 0.033 (mean ± std dev), Dice coefficient: 0.930 ± 0.028, and FPR: 0.056 ± 0.046. Fig 2 shows an example of lumen segmentation over time.

Fig 1. Expanded view about the left carotid artery at one time point. Shown are: a) internal (blue) and external (green) markers, b) tie-zone watershed with the tie-zones (white), and c) final semi-automated (green) and expert segmentations (blue).

Fig 2. Expected CCA lumen segmentation area vs time curve. Images at a) systole and b) diastole are shown in the inset images. Systolic-diastolic lumen area change was 11.2 mm2 (25.8% larger than the diastolic area of 43.3 mm2)

Discussion: Our method performed well compare to other carotid artery lumen segmentation methods that reported a Dice coefficient of 0.93 ± 0.02 on static 3 T MR image.[3] We achieved similar results (0.930 ± 0.028) despite using a more challenging dataset, as dynamic FSE images typically have lower intrinsic signal- and contrast-to-noise ratios than static cine FSE images.[1]

Conclusions: This initial study differs from previous carotid lumen segmentation studies due to the use of dynamic images. Although many factors contribute to carotid artery segmentation quality, no other studies have employed temporally resolved images. In future work, we intend to 1) make better use of temporal correlations across time frames, and 2) generate local distensibility curves of the wall and relate them to atherosclerotic disease and eventually, to risk of future stroke.

References: [1] ME Boesen et al., Magnetic Resonance in Medicine 2015; 74: 1103.[2] M Naghavi et al., Circulation, 2003; 108: 1664.[3] E Ukwatta et al., IEEE Transactions on Medical Imaging 2013; 32: 770.

a) b) c)



— Eric StinsonHigh Spatiotemporal Resolution 3D Contrast-enhanced MR Angiography with a Compact 3T Scanner

High Spatiotemporal Resolution 3D Contrast-Enhanced MR Angiography with a Compact 3T Scanner

Eric G. Stinson, Joshua D. Trzasko, Erin M. Gray, Norbert G. Campeau, Eric A. Borisch, Matt A. Bernstein, John Huston III, Stephen J. Riederer

Radiology, Mayo Clinic, Rochester MN, United States

Purpose: Since its advent in the early 1990s (1), contrast-enhanced MR angiography (CE-MRA) has benefitted from ad-vances in acquisition and reconstruction to more accurately portray the transit of contrast material through the vascula-ture. Specifically, advances in gradient hardware that allow for faster traversal of k-space and shorter scan times, parallel imaging techniques that facilitate reduced sampling, and advanced reconstruction schemes that leverage a prioriknowledge of signal sparsity all combine to improve spatiotemporal resolution and signal-to-noise ratio (SNR). A compact 3T MR system (2) with high performance gradients, allowing for reduced TE and TR, and a 32 channel RF receive coil (Nova Medical, Wilmington, MA), enabling increased undersampling factors with the SENSE technique (3), has recently been brought online at our institution. Further, a sparsity promoting reconstruction technique (4) has been fully incorpo-rated into our clinical practice (5). The purpose of this work is to take advantage of these recent hardware and software advances to perform high spatiotemporal resolution 3D CE-MRA of the brain. Methods: The compact 3T scanner used in this study features a lightweight and low-cryogen (12 liters) superconducting closed-bore main magnet and high-performance gradient system (Gmax=80mT/m, Slew rate SR=700 T/m/s). Because of the smaller gradient size (42 cm inner diameter), the gradient switching limits for peripheral nerve stimulation (PNS) are higher than those for whole-body systems and enable shorter TEs and TRs (6). The linear concomitant field of the asymmetric gradient design was corrected by real-time gradient pre-emphasis (7). In this IRB-approved study, a healthy volunteer was imaged with the 32-channel head coil to show the feasibility of high-spatiotemporal CE-MRA on this system. Scan parameters are shown in Table 1. Images were reconstructed with both a standard SENSE reconstruction and with an iterative sparse reconstruction(4,8). Results: The study was performed successfully, and no PNS was reported by the volunteer. Thin-slab sagittal maximum-intensity-projection images of a single time frame of the time-resolved study reconstructed with standard SENSE (a) and sparsity-promoting SENSE (b) are shown in Figure 1. Note the improved SNR and contrast-to-noise ratios in the image reconstructed with the sparsity promotion. The reconstruction times for the entire time series were 20 s and 348 s (5.8 m) for the standard SENSE and sparsity-promoting reconstructions, respectively. Discussion: An approximately 31% reduction in TE and TR compared to a standard-bore whole-body 3T system was observed when using the compact system (Table 2), allowing for high spatial and temporal resolution in the 3D time-resolved exam. This was enabled by the receive coil with additional channels which allowed for additional undersampling in the RL direction (3 vs. 2 or 2.67 in previous work(9)) for compara-ble image quality. Further improvements were seen with the sparsity promoting reconstruction that is now performed with-in a clinically-feasible amount of time. Future work includes (i) continued refinement of the imaging protocol including as-sessment of sagittal imaging and increased undersampling, (ii) image comparisons to those acquired using a standard whole-body 3T scanner, and (iii) incorporation of single-echo Dixon CE-MRA techniques. References: 1. Prince MR et al. JMRI. 1993;3:877–881. 2. Foo T. ISMRM. Singapore; 2016. p. 3629. 3. Pruessmann KP et al. MRM. 1999;42:952–962. 4. Trzasko JD et al. MRM. 2011;66:1019–1032. 5. Froemming AT et al. ISMRM. To-ronto, Canada; 2015. p. 1169. 6. Chronik BA et al. MRM. 2001;46:386–394. 7. Tao S et al. MRM. 2017;77:2250–2262. 8. Trzasko JD et al. ISMRM. Toronto, Canada; 2015. p. 0574. 9. Haider CR et al. MRM. 2008;60:749–760.

Figure 1: Thin-slab (64 partitions) MIPs of a single time frame of a time resolved 3D CE-MRA exam in which both images provide good depiction of the intracranial vasculature. The image recon-structed with a sparsity-promoting penalty (b) shows improved im-age quality compared to that re-constructed with standard SENSE (a).

TR/TE (ms) 2.9/1.3 FA/BW (°/kHz) 12/±62.5 FOV (cm3) 22.0×22.0×22.4 Res. (mm3) 0.98×0.98×1.00 SENSE R RY×RZ = 3×2 Update Time 5.1 s Table 1: Imaging parameters for coronal CE-MRA. (SI×RL×AP)

Compact / whole bodyTR (ms) 2.9 / 4.2 TE (ms) 1.3 / 1.9 Table 2: Comparison of TR and TE for compact vs. whole body 3T



— Sokratis StoumposFerumoxytol-enhanced Magnetic Resonance Angiography (FeMRA) for the Assessment of Potential Kidney Transplant Recipients

FERUMOXYTOL-ENHANCED MAGNETIC RESONANCE ANGIOGRAPHY(FeMRA) FOR THE ASSESSMENT OF POTENTIAL KIDNEY TRANSPLANT

RECIPIENTS

Sokratis Stoumpos1,2, Martin Hennessy3, Alex T Vesey1, Ram Kasthuri3, Aleksandra Radjenovic2,David B Kingsmore1, Patrick B Mark1,2, Giles Roditi3

1. Renal & Transplant Unit, Queen Elizabeth University Hospital, Glasgow, UK2. Cardiovascular Research Centre, University of Glasgow, Glasgow, UK

3. Department of Radiology, Queen Elizabeth University Hospital, Glasgow, UK

Purpose: The traditional methods for scanning blood vessels using MRI or CT carry potential risks forpatients with chronic kidney disease (CKD). Ferumoxytol is a superparamagnetic iron oxidenanoparticle preparation that has potential as an MRI contrast agent in assessing the vasculature1.The aim of this study was to determine the utility of ferumoxytol-enhanced magnetic resonanceangiography (FeMRA) use in pre-transplant assessment of patients with CKD.Methods: Patients with CKD requiring aorto-iliac vascular imaging as part of pre-operative kidneytransplant candidacy assessment between December 1, 2015 and August 1, 2016 were included inthe study. We used a proton density-weighted, in-phase (PDIP) 3D stack-of-stars gradient-echo pulsesequence (StarVIBE), to detect arterial calcifications. This was followed by first-pass and steady-stateangiography using incremental doses of up to 4mg/kg body weight of ferumoxytol (diluted fourfold) asintravenous contrast agent. All scans were performed for clinical indications where standard imagingtechniques were deemed potentially harmful. Image quality was evaluated in arterial and venouscompartments.Results: Twenty patients [mean age 57.4 (SD 10.6) years, mean eGFR 14.0 (SD 4.5) mL/min)] wereincluded in this series. We successfully demonstrated calcifications in the abdominopelvic region,which appeared dark on source images with signal-to-noise ratio (SNR) near background noise levels(Figure 1). Good arterial and venous enhancements were achieved, and FeMRA was not limited bycalcification in assessing the arterial lumen (Figure 2). The scans were diagnostic and aided clinicaldecision making in all cases. A patient was found to have bilateral renal artery and infrarenalabdominal aorta stenoses/occlusions. Interesting anatomic variants were illustrated in a patient with adual inferior vena cava and one with a retro-aortic left renal vein. Two patients were found to haveincidental complex renal cysts which had enhancing components with ferumoxytol; both of these wereconfirmed to be renal cell carcinomas on histology. All patients completed their studies withoutadverse events.Discussion: Our preliminary experience supports the feasibility and utility of FeMRA for vascularimaging in patients with CKD due for transplant listing, which has advantages of obtaining botharteriography and venography with a single test without nephrotoxicity. StarVIBE sequence allowedidentification of arterial calcifications before contrast administration.

References:1. Prince MR, Zhang HL, Chabra SG, Jacobs P, Wang Y. A pilot investigation of new superparamagnetic ironoxide (ferumoxytol) as a contrast agent for cardiovascular MRI. Journal of X-ray science and technology. Jan 12003;11(4):231-240.

Figure 2. FeMRA of abdominal and aorto-iliac vasculature. (A)Steady-state acquisition showing enhancement of both arterial andvenous vasculature. (B) First-pass imaging showing selective arterialenhancement (arteriography). (C) Steady-state acquisition showingselective venous enhancement after subtraction of the arterialcompartment (venography).

Figure 1. Coronal maximum intensity projection(MIP) views from non-contrast-enhanced MRI(StarVIBE) view after grayscale inversion (A) wherethe location and conformation of the vascularcalcifications correspond with CTA (B).

A B



— Sokratis StoumposFerumoxytol-enhanced Magnetic Resonance Angiography (FeMRA) for the Assessment of Patients with Complex Anatomy Due for Vascular Access Creation

FERUMOXYTOL-ENHANCED MAGNETIC RESONANCE ANGIOGRAPHY (FeMRA) FOR THE ASSESSMENT OF PATIENTS WITH COMPLEX ANATOMY

DUE FOR VASCULAR ACCESS CREATION

Martin Hennessy1, Sokratis Stoumpos2,3, Alex T Vesey2, Ram Kasthuri1, Aleksandra Radjenovic3, Patrick B Mark2,3, David Kingsmore2, Giles Roditi1

1. Department of Radiology, Queen Elizabeth University Hospital, Glasgow, UK2. Renal & Transplant Unit, Queen Elizabeth University Hospital, Glasgow, UK

3. Cardiovascular Research Centre, University of Glasgow, Glasgow, UK

Purpose: Conventional vascular imaging techniques are often problematic in kidney disease patients due to associated risks, invasiveness, and imprecision. This is particularly true for patients with complex anatomy or stenoses due to previous central vein catheter (CVC) insertions1 or failed vascular access creations. Ferumoxytol is a superparamagnetic iron oxide preparation that has potential as a magnetic resonance imaging contrast agent in assessing the vasculature. Methods: Patients requiring vascular mapping of their thorax and upper arms as part of their assessment before upper limb vascular access creation underwent ferumoxytol-enhanced magnetic resonance angiography (FeMRA) between December 1, 2015 and August 1, 2016. All scans were performed for clinical indications where standard imaging techniques were deemed potentially harmful or inconclusive. Image quality was evaluated in arterial and venous compartments. Results: First-pass and steady-state FeMRA using 4mg/kg body weight of ferumoxytol (diluted fourfold) as intravenous contrast agent were performed in 18 patients [mean age 61.2 (SD 11.5) years] with previous failed vascular access procedures. Ten patients were pre-dialysis [mean eGFR 12.0 (SD 3.4) mL/min] and 8 were receiving dialysis via a CVC. Good arterial and venous enhancements were achieved in central vasculature, and FeMRA was equally reliable for evaluation of the peripheral vessels. The images allowed precise assessment of the arterial and venous walls, luminal diameter and the presence of stenosis, occlusion, or thrombus formation. Complex central vein occlusions were identified in 6 patients (Figures 1 and 2). All patients completed their studies without adverse events. Discussion: Our preliminary experience supports the feasibility and utility of FeMRA for vascular mapping in patients with complex anatomy due for vascular access creation, especially those with previous CVC insertions who are at a higher risk for central vein stenosis.

References: 1. Schillinger F, Schillinger D, Montagnac R, Milcent T. Post catheterisation vein stenosis in haemodialysis:comparative angiographic study of 50 subclavian and 50 internal jugular accesses. Nephrol Dial Transplant.1991;6(10):722.

Figure 1. Cephalic arch and proximal cephalic vein stenoses in patient with a patent left brachiocephalic fistula with high pressures during haemodialysis treatment.

Figure 2. Perianastomotic stenosis in right forearm fistula associated with central vein stenosis (occluded right brachiocephalic vein).



— Matthias StuberFully Self-gated Push-button Non-contrast 5D Imaging of the Heart

Fully Self-Gated Push-Button Non-Contrast 5D Imaging of the Heart Stuber M1,2, Piccini D1,3, Di Sopra L1, and Yerly J1,2

1Department of Radiology, University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, 2Center for Biomedical Imaging (CIBM), Lausanne, 3Advanced Clinical Imaging Technology, Siemens Healthcare AG, Lausanne, Switzerland,

INTRODUCTION: For MRI of the heart, data acquisition is synchronized to the heartbeat and to respiration. Significant aspects of cardiac MRI data collection strategies have remained unchanged

over the past two decades, and the main hurdles to overcome at this juncture include operator dependency and time inefficiency. In a deliberate attempt to break away from the decades-old paradigm where data are collected in a prospectively triggered and gated fashion - we propose to sample image data uninterrupted, continuously, without triggering or gating, and irrespective of the heart’s position and its contractile state. By exploiting a free-running 3D golden

angle radial imaging sequence1, compressed sensing and center of k-space physiology signal extraction, the above paradigm can be challenged. METHODS:

On the imaging side, we have implemented a non-triggered uninterrupted free-running 3D radial bSSFP imaging sequence at 1.5T1 and no contrast agent is used. For

fat saturation, we exploit water-selective excitation pulses. Each segment in k-space consists of ca. 40 radial readouts and consecutive segments are rotated by the golden angle. One single scout scan that shows the heart in the three major orientations suffices to localize the 3D imaging volume that encompasses the whole heart. For physiological signal extraction, the modulation of the continuously sampled k-space center signal isused to sort the data into 4 respiratory states and some 20 cardiac phases. The resultant 5D datasets (x-y-z-respiratory-cardiac) are then reconstructed with a k-t sparse SENSE algorithm that exploits sparsity along both the respiratory and cardiac dimensions2. In three healthy adult volunteers, images were generated with thisapproach. RESULTS: Eighty high spatial resolution 3D datasets originating from different respiratory levels and time points within the cardiac cycle are available for each subject. This supports the 3D assessment of cardiac function on the one hand and detailed anatomical visualization of small anatomical structures on the other hand. For optimized visualization of the coronary anatomy, end-expiratory data from end-systole or mid-diastole can be chosen and motion artifacts are effectively suppressed (The Figure shows two volunteer examples. RCA: Right coronary artery; LAD: Left anterior descending; LCX: Left coronary circumflex). The total scan duration amounts to 11min, the temporal and spatial resolution is 50ms and 1.1mm3, and SAR 56%. Plan scanning is kept to a minimum as volume targeting, navigator placement and acquisition window selection isnot needed. Without ECG electrode placement or contrast agent administration, volunteer setup is facilitated.

DISCUSSION & CONCLUSION: The here-described approach simplifies patient setup and scan planning and may contribute to reduced operator dependency and improved ease-of use through push-button functional and anatomical 3D imaging of the heart. Recovery periods in-between breath-holds and breath-hold instructions are no longer needed, and relative to navigator gated scans, the signal sampling efficiency has increased from 2% to 30% as the technique obviates the need for trigger delays, fat-saturation and ramp-up pre-pulses. In conclusion, the here-described approach to 5D imaging addresses two distinct shortcomings of contemporary cardiovascular MRI: Operator dependency and time inefficiency. While technical feasibility has been demonstrated, studies in larger cohorts that rigorously expose strengths and weaknesses of this method are now warranted, and 4D flow imaging or tissue mapping may also benefit from such an approach.REFERENCES: 1.) Coppo et. al. MRM 2015. 2.) Feng et al.: MRM 2017.

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— Bing TianApplication of 3D SPACE MRI on Intracranial Aneurysm: A Preliminary Study

Application of 3D SPACE MRI on intracranial aneurysm: A preliminary studyBing Tian1,2, Christopher Hess1, Farshid Faraji1, Megan K Ballweber1, David Saloner1,3

1 Department of Radiology and Biomedical Imaging, UCSF, San Francisco, CA, USA 2 Department of Radiology, Changhai hospital of Shanghai, Shanghai, China 3 Radiology Service, VA Medical Center, San Francisco, USA

Purpose:High resolution MRI(HRMRI) of the intracranial vessel wall provides important insights in the assessment of intracranial vascular disease including intracranial aneurysm. This study aims to compare the image quality on pre- and post- 3D isotropic T1-weighted fast-spin-echo sequence (SPACE) images and to explore whether there is change in wall enhancement at follow up. This would establish the value of 3D isotropic SPACE methods in evaluating the vessel wall characteristics of patients with intracranial aneurysms.Methods:16 patients (5 male, age 60±15) with 21 stable intracranial aneurysms were scanned on a 3T Siemens Skyra scanner with pre- and post-contrast 3D T1-weighted SPACE (0.5mm isotropic). Follow up studies were performed on 4 patients(average 7.2 months), that included 3 patients with 2 imaging time points and 1 patient with 3 imaging time points. Aneurysm (size, type and location) characteristics were recorded. Kruskal-Wallis H test or Mann-Whitney test was used to investigate the relationship between wall enhancement and aneurysm type and location. Qualitative image quality scores and wall enhancement scores were assigned by two neuroradiologists on pre- and post-contrast SPACErespectively. The criteria of image quality is shown in Figure 1. Aneurysm wall enhancement equal to or greater than that of the pituitary infundibulum was regarded as enhancement. The criteria for wall enhancement is shown on Figure 2.Wilcoxon signed rank paired test was used to compare the image quality between pre- and post-contrast SPACE images, as well as the wall enhancement between follow up and baseline SPACE studies. Intraclass correlation coefficient (ICC) was used to evaluate the agreement between two reviewers for image quality and wall enhancement.Results:The mean aneurysm size was 9.99±7.68 mm, and at follow up the aneurysm size was unchanged. Fusiform aneurysms(3.63±1.12) showed more enhancement compared to saccular aneurysms (2.33±1.33). There were no significant differences in location between the group displaying enhancement and the group that non-enhanced (p = 0.83).Post-contrast SPACE images(3.71±1.13) had significantly higher image quality compared to pre-contrast images (2.84±1.34) with higher scores. Agreement between two reviewers for the image quality are excellent with ICCs of 0.848 (pre-contrast only), 0.883 (post-contrast only), and 0.880 (pre and post-contrast together). A wall enhancement

was found on 70% (14/21) of the aneurysms. The average wall enhancement score was 2.52±1.40 (reader 1). There was no significant difference in wall enhancement scores on the follow up studies. Agreement between two reviewers is excellent with ICCs of 0.941 for wall enhancement.Discussion:Our studies showed that post-contrast 3D SPACE images have significantly higher image quality compared to pre-contrast images. This reflects that post-contrast SPACE image provided better contrast between the vessel wall and CSF compared to pre-contrast studies. Another finding of this study is that there is no significant difference in wall enhancement scores on follow up studies. This result is consistent with the stable status and size of these aneurysms.Aneurysm wall enhancement on HRMRI following gad ministration of a contrast agent was already shown to be animportant indicator of rupture[1]. Additionally, it is generally accepted that artery wall enhancement on HRMRI could be a sign of inflammation[2]. In our study,This result seems differ from previous reported studies. However the average wall enhancement was less than 50% of the aneurysm wall area (average score: 2.52±1.40). Further studies are needed to identify the difference in wall enhancement degree between stable and unstable aneurysms. Compared to most previous 2D black blood FSE techniques studies that were performed with limited coverage and partial volume effects, 3D SPACE with isotropic resolution allows multi-planar reconstruction (MPR) of the tortuous vessel in any obliquity. 3D SPACE also provides coverage of the whole brain and all major intracranial vessels in a single acquisition which provides high scanning efficiency especially for intracranial aneurismal disease[3].References:[1] Edjlali M, Gentric JC, Régent-Rodriguez C, et al. Does Aneurysmal Wall Enhancement on Vessel Wall-MRI Help

to Distinguish Stable From Unstable Intracranial Aneurysms?Stroke. 2014;45(12):3704-3706.[2] Hu P, Yang Q, Wang DD, et al. Wall enhancement on high-resolution magnetic resonance imaging may predict an

unsteady state of an intracranial saccular aneurysm. Neuroradiology. 2016;58(10):979-985.[3] Mandell DM, Mossa-Basha M, Qiao Y, et al. Intracranial Vessel Wall MRI: Principles and Expert Consensus

Recommendations of the American Society of Neuroradiology. AJNR Am J Neuroradiol. 2016. [Epub ahead ofprint].

Figure 1 Figure 2 Figure 3



— Johannes TögerCerebrospinal Fluid (CSF) Flow in the Cerebral Aqueduct can be Quantified with High Resolution Using Magnetic Resonance Imaging at 7 Tesla



— Mostafa TolouiIn-vivo 4D-flow MRI at 10.5T: Feasibility Study

In-vivo 4D Flow MRI at 10.5T: Feasibility Study

Mostafa Toloui, Yigitcan Eryaman, Russell Lagore, Kamil Ugurbil, Bharathi Jagadeesan, Pierre-Francois Van de Moortele

Center for Magnetic Resonance Research, Medical School, University of Minnesota

Purpose: MR 4D flow1 based on Phase-contrast MRI uniquely provides non-invasive 3D time-resolved quantitative measures of blood flow. However, accurate characterization of complex cardiovascular hemodynamics (e.g. wall-shear stress, vortical flow structures, Reynolds stresses, turbulent kinetic energy) critically relies on high spatial resolution to resolve strong local velocity gradients. With increased signal to noise ratio (SNR) and parallel imaging performance2-4, ultra-high field (UHF) MRI (≥7T) holds strong promise for higher spatial resolution. However, UHF MRI faces multiple challenges, including B1 inhomogeneity, static and dynamic (respiration) susceptibility artifacts and magneto-hydrodynamic ECG distortion. Initial work indicate that RF heating should not prevent safe operation in vivo at 10.5T5,6. Here, we aim to evaluate the feasibility of 4D Flow MRI in a pig on a large bore 10.5T Siemens scanner previously described5,6. Methods: 4D Flow MRI Acquisition Three puck RF coils developed in-house7 with high-dielectric disks (Ø=80mm, 16mm thick) were used to image the neck of an anesthetized pig (Fig.1). The vendor 4D PC-MRI sequence in prospective cardiac gated mode was used with excellent ECG triggering quality. Main parameters: 256×246×30 mtx, 0.89×0.93×1.2 mm3 voxels, TE 5.43ms, TR 32.85ms, FA 15°, VENC 50 cm/s (along x, y and z), 16 cardiac phases, GRAPPA acceleration R=2, scan duration 36 min, output: 480 magnitude (no VENC) and 1440 phase images. b) Processing After noise filtering, anti-aliasing and eddy current correction§, the 16 3D-velocity fields are derived8 from the phase images along the 3 encoding axes (x,y,z). (further phase unwrapping was performed in MatlabTM whenever velocity was in excess of 50cm/s). A PC-MR angiogram (based on magnitude and phase images) is segmented in MimicsTM to generate 3D arterial/venous anatomy (Fig. 2B) as well as 3D flow masks to restrict velocity analysis within vessel boundaries. The resulting 3D velocity fields are visualized using 3D flow visualization package (TecplotTM). Results: The axial and sagittal cross-sections of the carotid artery and the external jugular vein are marked in two axial views of the magnitude images in Figs. 2A & 3A. The corresponding vessel geometry is shown in Figure 2B. 3D visualization of peak systolic and mid-diastolic blood flow are presented in Fig. 3B. The contour plots of velocity magnitude overlaid with velocity vectors on middle planes of the carotid artery and the external jugular vein (Fig. 3B) show a continuous increase of velocity as one moves from the arterial wall to the center of the artery. The corresponding temporal profile of average velocity and flowrate on cross-section I of the carotid artery and the external jugular vein are shown (Fig. 3C) through the cardiac cycle, with the peak of the flowrate in the external jugular vein occurring 4 cardiac phases later compared to that of the carotid artery. Conclusion: Preliminary 4D flow MRI was successfully obtained in a pig at 10.5T, paving the way towards human studies (pending FDA clearance for human imaging) at this ultra-high magnetic field. References & acknowledgments: [1] Markl et al. JMRI 20121;36(5):1015-36 [2] Vaughan et al. MRM 2006;56(6):1274-1282 [3] Wiesinger et al. NMR Biomed 2006;19:368-78 [4] Ugurbil et al. MRI,2003;21:1263-81 [5] Ertuk et al. MRM 2017,77:434-43 [6] Eryaman et al. ISMRM 2017 [7] Lagore et al. ISMRM 2017 [8] Schell et al. JMRI 2014;39:120-31. §We acknowledge Dr. S. Schnell for velocity Matlab code.

FIGURE 1. (left) photograph of the anesthetized pig with 3 puck coils and the ECG leads. Three out of five attached electrodes were chosen based on the best electrical ECG signal. (right) MR 4D Flow imaging parameters.

FIGURE 2. (A) Sample of reconstructed magnitude images on two different axial slices. (B) The corresponding 3D reconstructed geometries for two veins and carotid artery.

FIGURE 3. (A) Sample of reconstructed magnitude images on two different sagittal planes showing the carotid artery and the external jagular vein. (B) 3D velocity visualizations showing the blood flow on mid-planes of the carotid artery and the external jagular vein. (C) the corresponding in-time velocity and flowrate profiles.



— Alireza ValiAutomatic Quantification of the Impact of Intracranial Atherosclerotic Lesions on Cerebrovascular Hemodynamics Using 4D-flow MRI

Automatic quantification of the impact of intracranial atherosclerotic lesions on cerebrovascular hemodynamics using 4D flow MRI

Alireza Vali1, Eric Schrauben2, Maria Aristova1, Can Wu1, Shyam Prabhakaran3, Michael Markl1, Susanne Schnell1 1Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, 2Translational Medicine, The

Hospital for Sick Children, Toronto, 3Neurology, Feinberg School of Medicine, Northwestern University, Chicago Purpose: 4D flow MRI (time-resolved 3D phase-contrast MRI with 3-directional velocity encoding) is a promising method for the non-invasive measurement of cerebrovascular hemodynamics with full volumetric covarage of the major intracranial arteries and veins. However, quantification of flow and velocities throughout the complex cerebral vessels can be tedious, time-consuming, and prone to variability depending on user experience. Therefore, automated post-processing algorithms for cerebrovascular flow quantification in the Circle of Willis and major veins were developed and implemented in this study to segment the vessel anatomy, calculate and subdivide the vessels centerlines into anatomical segments, and quantify blood flow parameters. The feasibility of automated analysis was assessed in healthy controls and patients diagnosed with intracranial atherosclerotic disease (ICAD). Previous studies1 have shown that regional intracranial atherosclerotic lesions can significantly affect both arterial flow distal to the stenosis and the blood flow distribution in the entire cerebral arterial system. Hence, a systematic analysis of cerebral flow redistribution would be very useful to fully characterize ICAD. Methods: The study cohort (n=26; age: 68±14.2; 10 females) included ICAD patients with moderate (50%-70%) to severe (>70%) intracranial stenosis, as well as healthy volunteers (n=10; age: 60.7±8.1; 4 females). 4D flow MR images were acquired using a 1.5T or 3T MR scanner (Magnetom Avanto or Skyra; Siemens) with the following pulse sequence parameters: TR/TE=5.4ms/2.8ms, flip angle=15°, VENC=100cm/s, FOV= 220x160mm2, temporal resolution=43ms, and voxel size=1.1x1.1x1.2 mm3. The MRI data was preprocessed using an in-house analysis tool to remove random noise and to correct for velocity aliasing, phase offset, and eddy currents2. In addition, a 3D phase-contrast MR angiogram (PC-MRA) was derived using pseudo complex difference algorithm3. The new in-house post-processing tool (developed in MATLAB) is an extension of a previously published method4. However, the new tool is capable of simultaneous analysis of hemodynamic parameters in the major cerebral arteries and veins. First, the center points of blood vessels were extracted using a thinning procedure5 on binary volume obtained from the automatic segmentation of the PC-MRA4. A quadratic spline interpolation was used to find the centerline through the center points for every blood vessel individually. Representative results are shown in Fig. 1a where each artery has a centerline with a unique identification number. The derivative of the spline was computed along the centerlines for all blood vessels simultaneously to find the normal vectors for automatic placement of analysis cut-planes (Fig. 1b). At each cut-plane a secondary segmentation was performed to refine the regional definition of lumen boundaries. Finally, anatomical and hemodynamic parameters (i.e., diameter, peak velocity, net flow, and flow waveform) were quantified for each cut-plane. The average flow rate was determined as the mean over all cut-planes along a specific artery. Similarly, the maximum peak velocity was calculated for each vessel. For in-vivo verification, six cases (two healthy volunteers and four ICAD patients) that had been previously analyzed manually1 were re-analyzed with the new automatic tool. For manual analysis, on average ten analysis planes per case (overall 60) were placed at the major arteries of the Circle of Willis (left/right ICA, MCA, ACA, PCA, and BA) and major veins (sagittal and transverse sinuses). Then, peak velocity and flow rate were calculated using EnSight CEI. Results: Fig. 2 shows Pearson correlation graphs of the flow rate and peak velocity values from manual analysis versus the same quantities obtained from the new analysis tool for the matched cut-planes in the same arteries and veins. Correlations show a good agreement between the two methods (pflow_rate < 0.001 and ppeak_velocity < 0.001). As previously reported1, we also observed that flow rate and peak velocity asymmetry indices (the ratio of flow/velocity between left and right sides) for healthy volunteers were near unity, while for ICAD patients the indices were not balanced. The flow/velocity in the arteries on the side affected by ICAD could be reduced to 40% of the flow/velocity in the collateral blood vessels. For example, for patients with ICA or MCA stenosis flow rate/peak velocity asymmetry indices can be as low as 0.4/0.55 and 0.5/0.7, respectively. A complete quantification of brain arterial and venous hemodynamics can be achieved in 5-10min with the automated approach. Discussion: A fast and automated analysis tool is presented for the quantification of 3D cerebrovascular hemodynamics of the arteries in the Circle of Willis and major veins using 4D flow MRI data. This tool facilitates and simplifies postprocessing of 4D flow MRI data, especially when flow information from the entire FOV is required such as the analysis of flow redistribution in the case of ICAD patients. The comparisons of manual and automated analyses showed good agreement indicating specificity of the new automated in-house analysis tool. The automated method allows analysis of hemodynamic measures of the entire brain vasculature within 5-10 min with minimal user input. References: [1] Wu et al. AJNR 2017, 38, 515-522; [2] Bock et al. ISMRM 15, 2007, 3138; [3] Bock et al. ISMRM 16, 2008, 3053; [4] Schrauben et al. JMRI 2015, 42, 1458-1464; [5] Palagyi et al. IPMI 2001, 409-415

Fig. 1 Major arteries of the Circle of Willis displaying (a)centerline and (b) cut-planes perpendicular to blood vessel.

Fig. 2 Pearson correlation of manual versus automatedanalyses of (a) flow rate and (b) peak velocity



— Xinrui WangUnruptured Intracranial Aneurysms: Relationship Between Wall Enhancement and Rupture Risk Factors Based on High-resolution Magnetic Resonance Imaging



— Yan WangInternal Jugular Vein and Common Carotid Artery Separation in Pulsatile Tinnitus Patients Using Level Set Based Shape Prior Segmentation

Internal Jugular Vein and Common Carotid Artery Separation in Pulsatile Tinnitus Patients using Level Set based Shape Prior Segmentation

Yan Wang, Evan Kao, Bing Tian, Yue Zhang, Matthew R. Amans, Jing Liu, David Saloner Department of Radiology and Biomedical Imaging, University of California, San Francisco

Purpose: To develop and evaluate a segmentation method that extracts the internal jugular vein (IJV) and common carotid artery (CCA) from MR studies of patients with pulsatile tinnitus (PT). The distribution of IJV stenosis, cross-sectional area, and volume and the relationship between IJV and CCA, provide important information for evaluating clinical treatment options for PT patients.

Methods: MR Imaging: 17 patients with abnormal IJV underwent CE-MRA in a 3T Siemens Skyra scanner (Siemens Medical Systems, Erlangen, Germany). The 3D volume consisted of a 124mm-thick coronal slab, using a total acquisition time of 45 seconds. The acquisition parameters were: TR = 3.66 s; TE = 1.4 s; Flip angle = 20°; FOV = 200 mm; Matrix = 320 x 240; number of slices = 172; acceleration factor = 3. Image segmentation and analysis: Segmentation of IJV and CCA in MR images is fundamental for the quantitative measurement and assessment of IJV. In most individiuals the IJV and CCA are in close proximity and often abut each other. This renders their manual or automatic delineation difficult. We propose a level set based shape prior (LSSP) method to separate the IJV and CCA using in-house software developed in MATLAB [1,2].

Results: The results obtained on 17 patients showed that the proposed segmentation readily separates the IJV and the artery. A sample segmentation result is shown in Figure 1, where the lines in blue and in red represent the results obtained from the IJV and CCA respectively. The results showed that the proposed automated segmentation was comparable with manual segmentation. Quantitatively, the average Dice value reaches 87.6% for IJV segmentation, indicating good segmentation accuracy. The IJV analysis is shown in Figure 2. Reconstructed geometries of the IJV and the artery are shown in Figure 3. The good accuracy and fast speed of our proposed method makes it a potential tool for routine clinical use.

Figure 1: Example of segmentation of the IJV and artery in different slices. Top row: the original images; bottom row: the segmentation results.

Figure 2: The Left figure shows that which slices of the IJV and CCA are in direct contact and the right one shows those slices where the IJV has lumenal narrowing for each case.

Figure 3: The reconstructed segmented geometries of the IJV (blue) and the artery (red).

Discussion Our study indicates that the proposed segmentation method can quantify IJV dimensions reliably in good agreement with manual segmentation. The reduced segmentation time makes it suitable for clinical applications.

References [1] Wang Y, Zhang Y, Navarro L, Eker OF, Jerez RA, Chen Y, Zhu Y, Courbebaisse G. Multilevel segmentation ofintracranial aneurysms in CT angiography images. Medical physics. 2016 Apr 1;43(4):1777-86.[2] Wang, Y., Seguro, F., Kao, E., Zhang, Y., Faraji, F., Zhu, C., Haraldsson, H., Hope, M., Saloner, D. and Liu, J., 2017.Segmentation of Lumen and Outer wall of Abdominal Aortic Aneurysms from 3D Black-Blood MRI with a RegistrationBased Geodesic Active Contour Model. Medical Image Analysis.



— Sebastian WeingärnterHigh Resolution Dynamic T1 Mapping Using a Combination of Cardiac-phase Resolved Steady-state Look-locker Imaging and Locally Low-rank Denoising

Figure 1: Dynamic T1 mapping sequence: First the magnetization is driven to steady-state. Following an inversion pulse the recovery curve is then readout over multiple heart-beats using continuous FLASH excitations. The readouts are binned into several cardiac-phases providing multiple inversion times for each cardiac phase. Reinversion of the magnetization is applied after steady-state is reached again to fill the acquisition k-spaces.

Figure 2: a) Native cardiac-phase resolved T1 maps acquired in a healthysubject at a temporal resolution of 40ms, without (upper row) and with(lower row) LLR processing. Denoising restores visually appealing T1maps with low noise contamination. B) temporal cross-section of the pixel column indicated in the last cardiac-phase (white box), shows wellmaintained cardiac motion in the LLR denoised dynamic T1 maps.

High Resolution Dynamic T1 Mapping using a Combination of Cardiac-Phase Resolved Steady-State Look-Locker Imaging and Locally Low-Rank Denoising

Sebastian Weingärtner1,2,3, Steen Moeller2, Mehmet Akçakaya1,2

1Electrical and Computer Engineering, and 2Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, US 3Computer Assisted Clinical Medicine, University Medical Center Mannheim, Heidelberg University, Mannheim, Germany

PURPOSE: Conventional myocardial T1 mapping is restricted to the acquisition of a single snapshot of the cardiac cycle, hampering inter-phase comparability and potentially compromising diagnostic certainty1. Methods for cardiac phase-resolved T1 mapping have recently been proposed, allowing dynamic tissue characterization, for the trade-off against reduced acquisition matrix sizes2. In this study we sought to exploit noise information in a multi-dimensional cardiac phase-resolved T1 mapping data set to allow for quantification with improved spatio-temporal resolution. METHODS: Dynamic T1 maps are acquired using a cardiac-phase resolved, triggered Look-Locker sequence, with multiple inversions from the FLASH steady-state (Figure 1)2. In the reconstruction, the efficiency of the rectangular inversion pulse, as obtained from a three-parameter fit is used to provide a B1

+ estimate, is used to calculate a flip-angle corrected T1. We propose a locally low rank (LLR) denoising technique following parallel imaging, without the need for iterative processing. Local patches are extracted from a GRAPPA reconstruction, performed in SNR units3. Low-rank is enforced in the Casorati matrix of these patches by singular value thresholding. Denoising is applied in a multi-scale approach, with variable patch sizes. The threshold parameters for each scale were analytically calculated from the singular value distribution of a Gaussian random matrix, as described by Marchenko and Pastur4. Imaging was performed at 3T with the following parameters: TR/TE/α=5ms/2.5ms/3°, FOV/res.=300x225/1.3x1.3mm2, sl.thick=10mm, GRAPPA=3, part.-fourier=6/8, breath-hold=18s. RESULTS: Figure 2 depicts all cardiac phases of a dynamic quantitative T1 map in a representative healthy-subject at 40ms temporal resolution. Unprocessed T1 maps exert major noise variability especially in the later phases, due to unfavorable sampling of the inversion recovery curve. The proposed LLR processing successfully generates T1 maps with high spatio-temporal resolution, depicting homogeneous T1 times across the myocardium and sharp delineation towards the blood pools. As shown in Figure 2b) accurate representation of the cardiac motion throughout the R-R interval with no apparent temporal blurring is maintained in the proposed approach. Comparable end-diastolic T1 times are obtained from septal ROIs are in this healthy subject (unprocessed: 1399ms, processed: 1414ms). Spatial variability across the septal ROI was reduced by 60% using the proposed method (132.3ms vs 53.5ms). DISCUSSION: In this work we evaluated the use of LLR denoising in dynamic myocardial T1 mapping to arrive at high spatio-temporal resolution in quantitative imaging. LLR reconstructions have been previously explored in the context of MRI5, although mostly using heuristic parameter choices. The use of reconstruction in SNR units, maintained Gaussian noise in the Casorati Matrix and enabled the calculation of analytical threshold values, eliminating any heuristic parameter selection process. Denoising of the proposed multi-dimensional dataset suggests feasibility of dynamic T1 mapping at an in-plane resolution of 1.3x1.3mm and a temporal resolution of 40ms. This potentially increases sharpness of tissue interfaces and improves delineation of cardiac structures, ultimately benefiting diagnostic confidence and reproducibility in myocardial T1 mapping. Future work is warranted to assess the clinical value of detailed, phase-resolved T1 quantification in various cardiomyopathies, including the evaluation of highly mobile cardiac tissue, such as present in tachycardia or in the papillary muscles. REFERENCES AND FUNDING: 1. Kellman, JCMR, 2014, 16:2; 2. Weingärtner, ISMRM, 2017, 3102 ; 3. Kellman, MRM, 2005, 54:1439; 4. Marchenko, MatSb, 1967 72:507; 5. Zhang, MRM, 2015, 73:655; NIH: R00HL111410, NIH: P41EB015894 and AFOSR.



— Yan WenFirst Experience with Free-breathing Cardiac Quantitative Susceptibility Mapping in Patients Post Gadolinium Administration

First Experience with Free-breathing Cardiac Quantitative Susceptibility Mapping in Patients post Gadolinium Administration

Yan Wen1,2, Thanh D. Nguyen2, Pascal Spincemaille2, Jiwon Jim3, Jonathan W. Weinsaft3, and Yi Wang1,2

1Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, United States 2Radiology and 3Medicine, Weill Cornell Medicine, New York, NY, United States

INTRODUCTION: Cardiac MRI is widely used to assess cardiovascular function and tissue properties. Quantitative susceptibility mapping (QSM) performed without gadolinium has been shown to enable differentiation of oxygenated and non-oxygenated blood based on deoxyheme quantification (1). Gadolinium produces T1 shortening, but its impact on feasibility of cardiac QSM is unknown. This report details the first application of cardiac QSM using contrast-enhanced MRI. METHODS: Free-breathing cardiac QSM was optimized in four healthy volunteers prior to application post contrast in a clinical patient with systolic heart failure (SHF). Post-contrast cardiac QSM was performed 20 min after gadolinium infusion (0.2 mmol/kg) using an ECG-triggered diaphragmatic navigator gated multi-echo GRE sequence at 1.5T. Scan parameters were: 5 echoes, first TE 1.7 ms, ∆TE 2.3 ms, TR 15 ms, matrix=192x192x24, resolution 1.5x1.5x5 mm, bandwidth ±62.5 kHz, views per segment 10, GRAPPA acceleration factor 2. A graph cuts phase analysis method (2) and chemical shift update method (3) was used to compute a total field with no phase wrap and fat chemical shift, and a Total Field Inversion method (4) was used to obtain the final susceptibility map. RESULTS: Figure 1 shows the corresponding QSM maps as acquired from patient (top) and volunteer (bottom) cases. Both demonstrated higher susceptibility in the RV blood pool (bright) vs. LV blood pool (dark), consistent with increased RV deoxyheme concentration. The average susceptibility difference between RV and LV blood pools was 279.2 ± 18.2 ppb (78.9 ± 1.2% SvO2) in the four healthy volunteers, and 263.3 ppb (80.0% SvO2) in the SHF patient. Note the differential susceptibility between LV myocardium and LV blood pool in the patient contrast-enhanced QSM map (top), corresponding to known higher gadolinium concentration in blood vs. myocardium. Conversely, no such susceptibility differences between LV blood and myocardium are evident on non-contrast QSM map (bottom). DISCUSSION: This is the first study to report feasibility and results of free-breathing contrast-enhanced cardiac QSM. Our findings demonstrated differential blood pool oxygenation equivalent to non-contrast QSM maps, as well as potential utility for gadolinium concentration quantification as it is necessary for applications such as late gadolinium enhancement and extracellular volume fraction quantification. REFERENCES: 1. Wen Y, Nguyen T, Spincemaille P, Kim J, Weinsaft J, Wang Y. A Comparison Study between the 2D Breath-holding and 3D Free-breathing approaches to in vivo Cardiac Quantitative Susceptibility Mapping. Proc Int SocMagn Reson Med 2017;25:2885.2. Dong J, Liu T, Chen F, Zhou D, Dimov A, Raj A, Cheng Q, Spincemaille P, Wang Y., "Simultaneous Phase Unwrapping and Removal of Chemical Shift (SPURS) Using Graph Cuts: Application in Quantitative Susceptibility Mapping," in Medical Imaging, IEEE Transactions on , 2015. 34(2), 531-540. 3. Dimov A. V., Liu T., Spincemaille P., Ecanow J. S., Tan H., Edelman R. R. and Wang Y., Joint estimation of chemical shift and quantitative susceptibility mapping (chemical QSM). Magn Reson Med, 2015, 73: 2100–2110. 4. Liu Z, Kee Y, Zhou D, Spincemaille P, Wang Y. Preconditioned QSM to Determine a Large Range of Susceptibility Over the Entire Field of View from Total Field. Proc Int SocMagn Reson Med 2016;24:0032.

Figure 1. Cardiac QSM (left) and corresponding T2*W (right) acquired post-contrast (top) and non-contrast (bottom), in a patient and normative volunteer, respectively.



— Oliver Wieben4D-flow MRI of Uterine Blood FLow in the Pregnant Rhesus Macaque: Flow Distribution and Reproducibility

4D Flow MRI of Uterine Blood Flow in the Pregnant Rhesus Macaque: Flow Distribution and Reproducibility

Philip Corrado1, Jacob Macdonald1, Sydney Nguyen2, Kevin M. Johnson1,3, Chris Francois3, Scott Reeder3, Ian Bird4, Dinesh Shah4, Ted Golos2,5, Oliver Wieben1,3

Depts. of Medical Physics1, Endocrinology & Reproductive Physiology2, Radiology3, Obstetrics & Gynecology4, Comparative Biosciences5, University of Wisconsin, Madison, WI

Purpose: Reduced uterine blood supply causes complications in pregnancy including fetal growth restriction1. The uterine arteries and uterine branches of the ovarian arteries supply most of the oxygenated blood to the uterus, but assessment with conventional Doppler Ultrasound2 and 2D PC3 is challenging. Recently, we demonstrated the feasibility of 4D Flow MRI in the placenta and fetus4. Here we investigate the flow distribution and reproducibility of area and flow measures in the uterine and ovarian arteries and veins in a rhesus macaque model. Methods: Twelve healthy, pregnant rhesus macaques were imaged with a 3.0 T scanner (Discovery MR750, GE Healthcare, Waukesha, WI) with a 32 channel torso coil. All monkeys were in the early 2nd to early 3rd trimester of gestation and imaged in right lateral position. Pairs of 4D flow scans were acquired back-to-back in the same session (N=6) and on consecutive days within ~24h (N=8) with a radially undersampled (PC VIPR)5 acquisition (TR/TE=6.4/2.8ms; FA=8°; VENC=60cm/s; FOV=16x16x16cm3; matrix = 192x192x192; isotropic resolution: 0.83 mm, scan duration=10min) with retrospective ECG and respiratory gating (50% efficiency). During each scan, the mother and, thereby, the fetus were sedated with isoflurane. Flow and cross sectional area were measured and visualized at midpoints in the uterine and ovarian vessels. Reproducibility was quantified by computing the relative change in measures taken from paired scans. Results: Fig. 1 shows a representative example of the anatomy (magnitude – grayscale) and color-coded velocity field for selected vessels. A reformatted 2D view of the through-plane velocities is shown in the sub-panel. Table 1 shows the % of scans in which each vessel segment was identified. Fig. 2 shows blood flow through the uterine arteries and ovarian veins, color-coded for dominant vs non-dominant side. Fig. 3 summarizes the changes in area and flow assessed in Same-Day scans and in Consecutive Day scans. Discussion: With 4D Flow MRI, we found closely matched inflow and outflow flow volumes to the uterus in the rhesus macaque. Inflow was dominated by the uterine arteries with fairly even left/right flow distribution. The major outflow pathway was through the ovarian veins, which often showed uneven flow distribution. The 13% higher flow total in the ovarian veins (see Fig. 2) is likely due to flow contributions from the ovaries in addition to flow from the uterus. The ovarian arteries, which are known to contribute to the uterine blood supply in humans6, as well as the uterine veins, could not be seen, either due to low flows or technique limitations (VNR or spatial resolution). Reproducibility in flow measurements for back-to-back scans (<13%) was similar to prior studies of ours in other body regions. Increased day-to-day variability could be caused by diurnal variations, anesthesia effects, and other physiological variations. Variance in venous flow and area was greater, which are known to be sensitive to hydration, blood pressure, posture, and other factors. Area measurements also varied more on consecutive days than in back-to-back scans. References: 1. Browne et al.. Philosophical Transactions of the Royal Society B: Biological Sciences. 2015;370(1663):20140068. 2. Santolaya et al.. J Reprod Med. 1994;39(9):690-4. 3. Pates et al. MRM 2010;28:507-10. 4. J MacDonald et al, SMRA 2016. 5. Gu et al. PC VIPR: A High-Speed 3D Phase-Contrast Method for Flow Quantification and High-Resolution Angiography. Am J Neuroradiol 2005;26:743–749. 6. Degner et al. Reprod Sci. 2016;1-9. Acknowledgements: The authors acknowledge the support of the NIH Human Placenta Project (NICHD U01HD087216) and NIH grant number P51 OD011106 to the Wisconsin National Primate Research Center. We also thank GE Healthcare for their support.

Fig. 1. Flow Visualization in the abdomen and fetus with PC VIPR. Transverse velocity profile shows through-plane velocities in right uterine artery.

Fig. 2. Flow through the uterine arteries andovarian veins averaged over all scans.

Fig. 3. Same-Day and Consecutive-Day Flow andArea Reproducibility averaged over all scans.



— Yibin XieCarotid All-In-One: Comprehensive Quantitative Evaluation of Atherosclerosis in One Scan

Carotid All-In-One: Comprehensive Quantitative Evaluation of Atherosclerosis in One Scan Yibin Xie1, Anthony G. Christodoulou1, Nan Wang1,2, Zixin Deng1,2, Bill Zhou1,3, Wei Yu4, and Debiao Li1,2

1. Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, USA; 2. Department ofBioengineering, University of California, Los Angeles, USA; 3. David Geffen School of Medicine, University of

California, Los Angeles, USA; and 4. Department of Radiology, Anzhen Hospital, Beijing, China

Purpose: Despite extensive implementation and validation, multi-contrast MRI has yet to fully deliver on its promise to become the standard of care imaging method for evaluating carotid atherosclerosis. A few crucial limitations still exist, including long and motion-prone scans, complex procedures, and variability in image interpretation due to its qualitative nature. Relaxometry offers a potential solution with high reproducibility and portability of the results1,2. In this study, we extend our previous single-scan concept3 to Quantitative Multi-contrast Atherosclerosis Characterization (qMATCH). The goal is to provide a fully quantitative evaluation of carotid atherosclerosis, including bright-blood MRA, dark-blood wall morphology, T1- and T2-weighted images, and quantitative mapping, all in one scan.

Methods: The qMATCH technique is designed based on low-rank tensor (LRT) framework4, which exploits the partial separability of space and contrast dimensions in the multi-contrast images to achieve vast acceleration. It employs variable-duration T2-IR preparations to generate various T2 weightings and a continuous 3D flow-compensated spoiled gradient echo readout to capture various T1 weightings (Fig.1). Cartesian acquisition with randomized reordering was implemented according to a variable-density Gaussian distribution allowing frequent sampling of the central k-space. We represent our 5-D image in collapsed form as , where contains basis functions describing T1/T2 relaxation and contains spatial coefficients.

is determined from training data and then fitted to the remainder of the sparsely sampled data:

where is the measured data, describes MRI encoding and sampling, is the total variation regularization functional, and is the regularization parameter. All data were acquired on a 3T Siemens Verio scanner with the following parameters: spatial resolution = 0.7mm isotropic, coronal slab FOV=150x150x26mm3, FA=8°, TEs = 20/30/40/50/60/70ms, scan time = 8mins. Relaxometry by qMATCH was tested in a custom phantom using IR-SE as the reference. In vivo imaging was performed in 7 healthy subjects with no known carotid atherosclerosis. MOLLI5 and T2prep SSFP6 were used as the reference in vivo.

Results: T1 and T2 quantifications by qMATCH showed reasonable agreement in phantom compared with reference in the Bland-Altman analysis (Fig. 2). Multi-contrast images from qMATCH showed satisfactory image quality (Fig.3). Bright-blood MRA, dark-blood wall morphology, T1- and T2-weighted images are demonstrated as the corresponding phases noted in Fig. 1. Table 1 summarizes the T1 and T2 measurements for muscle, blood and vessel wall by qMATCH and 2D reference techniques, respectively, showing little relative differences between the two methods.

Discussion: Preliminary results from phantoms and healthy subjects demonstrated the feasibility of qMATCH showing satisfactory image quality and reliable T1 and T2 quantification. qMATCH may provide a comprehensive assessment of multiple lesion characteristics including luminal stenosis (by bright-blood MRA), plaque burden (by dark-blood images), and plaque composition (by multiple T1/T2 weightings and quantitative mapping). Additional advantages over conventional protocols include high-resolution 3D acquisition, large coverage and inherently co-registered image set. Future work will focus on validating qMATCH in patients with carotid atherosclerosis.

Reference: 1. Biasiolli, L. et al. JCMR, 15, 69 (2013); 2. Coolen, B. et al. MRM, 75, 1008-1017 (2016); 3. Fan, Z. et al. JCMR, 16, 53 (2014); 4. Christodoulou, A. et al. JMR, 270, 176-182 (2016); 5. Messroghli, D. et al. MRM, 52, 141-146(2004); 6. Giri, S. et al. JCMR, 11, 56 (2009).

Figure 1. Pulse sequence diagram for qMATCH and corresponding simulated signal evolution.

Figure 2. T1 and T2 quantification comparison between qMATCH and reference method (2D IR spin echo) in the phantom.

Table 1. Comparison between the in vivo T1 and T2 mapping results from qMATCHand 2D reference methods (MOLLI and T2prep SSFP).

Figure 3. A representative qMATCH image set from a healthy subject.



— Chun YuanCharacterization of Carotid Plaque Magnetic Resonance Imaging with Deep Learning Convolutional Neural Networks

Characterization of Carotid Plaque MRI with Deep Learning Convolutional Neural Networks

Chun Yuan1,2, Rui Li2, Xihai Zhao2,Yuxi Dong3, Yuchao Pan3, Gador M. Canton1, Yan Song4, Wei Xu3,

1. Department of Radiology, University of Washington, Seattle, WA, USA2. Center for Biomedical Imaging Research, Tsinghua University, Beijing, China3. Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing, China4. Department of Radiology, Beijing Hospital, Beijing, China

Purpose We propose a novel, deep learning, convolutional neural network (CNN) based method to identify and quantify carotid atherosclerotic plaque compositional features automatically using multi-contrast MRI of carotid arteries. Methods The problem of carotid plaque segmentation can be formulated as a pixel-wise segmentation prediction problem, where we take a location of an MR image as input and automatically output a pixel-wise label map, classifying the pixels into different tissues, using the CNN model. Our model is based on a residual network that was fine-tuned using 101 layers pre-trained on the ImageNet dataset. Each input location contains four gray-scale images (T1, T2, TOF and MPRAGE), and the output is the pixel-wise segmentation result. In the original residual net, the input layer connects with a convolution layer. Patient population: Our data set includes 1,098 subjects who participated in the CARE II study (1). Each MRI had four sequences T1, T2, TOF and MPRAGE (16 locations per subject, totaling 17,568 locations). Trained reviewers outlined vessel lumen and outer wall boundaries for all images and identified plaque components including: calcification, lipid rich necrotic core (LRNC), intraplaque hemorrhage (IPH), loose matrix (LM), and fibrous tissue (FT). This was performed with CASCADE, a custom plaque analysis software (Seattle, WA). Out of the 1,098 subjects, 880 were used for training and 218 for testing. We performed the experiments on an Ubuntu server with a Titan X GPU. Training took approximately 20 hour, while predicting a location takes less than 1 second. We evaluated the predictions with two metrics: 1). Comparison of our prediction with ground truth (manual segmentation), 2). We calculated intersection of unions. We also compared our results to another automated segmentation technique (MEPPS from CASCADE(2)). Results CNN performs a little better than MEPPS in fibrous tissue and calcification detection, and much better in LRNC and IPH. Neither method performed well for LM, due to the lack of positive samples in the training data set. Conclusion Automatic atherosclerotic plaque characterization may be possible using the CNN model. This model may be used as an effective tool to assist radiologists and to screen large dataset of carotid MRI.

1. Zhao X, Li R, Hippe DS, et al. Chinese Atherosclerosis Risk Evaluation (CARE II) study: anovel cross-sectional, multicentre study of the prevalence of high-risk atherosclerotic carotidplaque in Chinese patients with ischaemic cerebrovascular events—design and rationale. Strokeand Vascular Neurology 2017;2:e000053.doi:10.1136

2. Liu F, Xu D, et al.. Automated in vivo Segmentation of Carotid Plaque MRI with Morphology-Enhanced Probability Maps. Magnetic Resonance in Medicine, 2006; 55(3):659-668.



— Qiang ZhangAutomatically Identify Plaque Components in Carotid Artery using Simultaneous Non-contrast Angiography and IntraPlaque Hemorrhage (SNAP) Imaging

Automatically Identify Plaque Components in Carotid Artery using Simultaneous Non-Contrast Angiography and intraPlaque hemorrhage

(SNAP) imaging Qiang Zhang1, Huiyu Qiao1, Shuo Chen1, Xihai Zhao1, Zhensen Chen1, Chun Yuan1,2, Huijun

Chen1 1Center for Biomedical Imaging Research, Tsinghua University, China, People’s Republic of

2Vascular Imaging Laboratory, University of Washington, United States Purpose: For imaging plaque components, traditional 2D multi-contrast imaging technique [1] suffers from small coverage, long scan time and complex post processing. Recently, a SNAP technique [2] has been validated that can be manually qualitatively identify intraplaque hemorrhage (IPH) [2] and calcification (CA) [3]. The purpose of this study is to develop an automatic method to segment plaque components, including NC, CA and fibrous tissue (FIB) using SNAP images. Methods: In this retrospective study, 68 patients (44 males, mean±SD age: 61.67±9.49 years) with carotid plaque were included. For both sides of carotid arteries in each patient, the lumen, outer wall and plaque components (NC (including IPH) and CA) were delineated in the multi-contrast images by two experienced reviewers in consensus based on the acquisition protocol: T1, T2, TOF [4]. The rest part of vessel wall except NC and CA was considered as FIB. The SNAP sequence consists of an inversion recovery acquisition (IR) and a reference acquisition (REF). In this study, we chose the magnitude of IR, the real part of IR, the imaginary part of IR, the magnitude of REF, CR, and calculated SNAP2 [5] as the main features for plaque components segmentation. The manually delineated plaque components contours were mapped from multi-contrast image to SNAP image so that each pixel in SNAP image inside the vessel wall has a labeled class as NC, CA or FIB. Finally, we used a 3 layers artificial neural network (ANN) to automatically classify each pixel with the previous described six features and the morphology features [9], and leave-one-out cross validation was used to test the performance of the proposed segmentation method. Results and Discussion: The NC, CA and FIB areas between automatic and manual segmentation were significantly correlated (All R values larger than 0.79) (Table 1). The sensitivity and specificity of NC and FIB segmentation were high (all larger than 0.81). The CA segmentation of the proposed method has a moderate specificity (0.59) and a high sensitivity (0.98) (Table 2). In this study, the feasibility of using a single SNAP sequence to automatically segment the lipid rich/necrotic core, calcification and fibrous tissue has been validated.

References:

Tissue R P NC 0.82 <0.001 CA 0.79 <0.001 FIB 0.88 <0.001

Sensitivity Specificity NC 0.81 0.93 CA 0.59 0.98 FIB 0.92 0.85

Table 1. Correlation of components area between automatic/manual segmentation

Table 2. Sensitivity and Specificity of ANN classifier

[1]. Yuan, C., et al., Circulation, 2001 [3]. Chen, S., et al., ISMRM, 2015 [5]. Balu, N., et al., ISMRM, 2014

[2]. Wang, J., MRM, 2013 [4]. Zhao, X., Investigative Radiology, 2010



— Chengcheng ZhuGated Thoracic Magnetic Resonance Angiography at 3T: Is Contrast Needed?

Gated Thoracic Magnetic Resonance Angiography at 3T: Is contrast needed?Chengcheng Zhu, Henrik Haraldsson, Kimberly Kallianos, Travis Henry, David Saloner, Michael D. Hope

Department of Radiology and Biomedical Imaging, UCSF, San Francisco, CA, USA

Purpose: Renal failure is a common comorbidity in patients undergoing thoracic aortic magnetic resonance angiography (MRA). Several imaging techniques have been proposed in this population including non-contrast MRA1 and MRA with the iron-based blood-pool contrast agent which can be used in renal failure2. We compare qualitative and quantitative image quality measures for the two approaches, and assess the reproducibility of standard aortic measurements. Materials and Methods: Respiratory and cardiac gated MRA of the chest was performed at 3T in 45 patients (44 male, mean age 71 years): 23 after administration of iron-based USPIO blood pool contrast (Ferumoxytol), and 22 without contrast. Ferumoxytol MRA was performed in patients with clinical indications for thoracic imaging and significantly reduced renal function (eGFR < 40 mL/min/1.73 m2). An additional 20 patients with clinical gated chest CTA were also included as a reference. A FLASH sequence was acquired in the diastolic phase with 1.2mm×1.2mm×2mm resolution and 32cm×32cm FOV. An inversion recovery preparation (TI = 200ms) was used for contrast MRA and a T2 preparation of 40ms was used for non-contrast MRA to improve the contrast to surrounding tissues. The major chest vessels including aorta, pulmonary arteries and veins, superior and inferior vena cava, aortic valve, and coronary arteries were evaluated. Image quality was assessed with a 5-point Likert scale, vessel lumen-to-muscle contrast ratios, and vessel wall sharpness. Two reviewers measured the ascending aortic diameter and valve annulus area. Interrater agreement was assessed using Bland-Altman plots and coefficient of variation (CV). Results: Qualitative image quality was better with blood pool contrast in all principal vessels of the chest (mean Likert of 4.2±0.79 versus 2.6±0.77, p<0.001, Figure 1). Quantitative assessment was also improved with higher contrast ratios in all vessels (5.26±3.3 versus 1.9±0.53, p<0.001), and greater sharpness of the aortic annulus and ascending aorta (0.70±0.16 versus 0.56±0.14 mm-1, p<0.001, and 0.87±0.16 versus 0.62±0.16 mm-1, p=0.008, respectively). Reproducibility of measurement was marginally better for the ascending aortic diameter (CV of 2.80% versus 3.23%, CTA reference 2.46%), but substantially increased for the aortic valve annulus area with blood pool contrast (CV of 4.93% versus 7.32%, CTA reference 4.80%). Discussion and Conclusions: Respiratory and cardiac gated MRA is feasible for ascending aortic evaluation either with or without blood pool contrast at 3T. Non-contrast MRA is appropriate for serial imaging of aortic dilation. Blood pool MRI contrast improve the image quality and enables more reproducible measurements of the aortic valve annulus area for transcatheter aortic valve replacement (TAVR) planning.References: 1. Ruile P, EHJ Cardiovasc Img. 2016; 2. Kallianos K. International Journal of Cardiology. 2017

Figure 1. Representative images of non-aortic anatomy with contrast (left) and noncontrast (right) MRA: bifurcation of the pulmonary artery (A, Likert 4.5 versus 3), left lower lobe pulmonary vein (B with asterisk, Likert 5 versus 2.5), and superior vena cava (C with asterisk, Likert 4 versus 2.5). Note that the contrast MRA for the superior vena cava demonstration has an aortic valve replacement (white asterisk).



Poster Presentations


— Manuela AschauerMR Angiography in Patients After MRI Compatible Pacemaker/IECD Implantation

MR – Angiography in Patients after MRI Compatible Pacemaker/ IECD Implantation

Manuela A. Aschauer 1,2 ; Alexandra Hirn 1; Ingeborg M. Keeling 1,3; Otto E. Dapunt 1,3; 2 Department of Neuroradiology, Vascular and Interventional Radiology, 3Department of Cardiac

Surgery, 1Medical University of GRAZ/Graz/ Austria

Purpose: Analyzation of MRA examinations and patient (pt) follow up after MRI compatible pacemaker implantation Methods/Patients: We retrospectively analysed 40 consecutive MR examinations between 2011 and 2015 in 39 patients (10w/29m), age 30-87 years, mean 63+/-15, maximum BMI 46kg/m2, mean 29. All procedures were exactly handled as the MR and IECD manufacturer explained, at least a radiologist took care during the whole examination, at the same day before and after the examination a cardiologist examined the patient and handled the IECD duties. 1,5T MR machines were used: Espree, Sonata, Symphony and Tim (SIEMENS, R). Results: 20% of examinations contained an angiography only, 20% angio and other diagnostic sequences, 60% were without angio. No adverse reactions with need to treatment occurred during the examination and the follow up period that were classified as MR or IECD or contrast media (66% of pts. received) related. Duration of the examination: mean 32 +/- 9min in the MR room. Artefacts due to the IECD were seen in 12 % of patients, in two patients overlapping with artefacts from other postoperative materials. All MR/MRA examinations could answer the questions from the clinicians.74 % of patients subjectively rated no difference of comfort/discomfort regarding a comparable MR examination before IECD implantation. 52 % of examinations were done within 12 month after IECD implantation. IECD function after MR was unchanged in all patients. Discussion: Limitation of the study is the small number of patients. Every centre should evaluate the IECD patients with MR/ MRA to get more information about this topic and to convince the referring physicians with the results.

Fig.1: Right sided pacemaker pocked with mild artefacts

References: please ask [email protected]



— Waleed BrinjikjiComparison of Efficacy of Standard Neurovascular Coil to Dedicated Carotid Surface Coil in Evaluation of Intraplaque Hemorrhage

Title: Comparison of Efficacy of Standard Neurovascular Coil to Dedicated Carotid Surface Coil in Evaluation of Intraplaque Hemorrhage

Authors: Waleed Brinjikji M.D., J Kevin DeMarco M.D., Giuseppe Lanzino M.D., John Huston III M.D.

Background and Purpose: A number of studies have validated carotid plaque imaging with surface coils as the gold standard for in-vivo plaque characterization. One limitation of surface coil imaging is the fact that it is time intensive and requires special equipment and expertise. We recently added a 3D MPRAGE sequence for detection of intraplaque hemorrhage to our standard neck MRA protocol using a neurovascular coil (i.e. clinical plaque protocol). However, little is known regarding the accuracy of this technique in detecting intraplaque hemorrhage. The purpose of this study was to evaluate the sensitivity of our clinical plaque protocol to MRA with a carotid surface coil in detecting intraplque hemorrhage.

Materials and Methods: Consecutive patients with suspected carotid atherosclerotic disease were scanned using our carotid plaque protocol with MPRAGE obtained using a neurovascular coiland a dedicated carotid plaque MRI using surface coils. Two independent reviewers interpretedthe images. Intraplaque hemorrhage was defined as signal intensity >1.5 the adjacent sternocleidomastoid in the carotid plaque. Sensitivity, specificity and accuracy of the carotid plaque protocol compared to the gold-standard surface-coil neck MRI was obtained.

Results: Thirty-seven patients with 74 carotid arteries were imaged. On surface coil imaging, 20 arteries (27.0%) had intraplaque hemorrhage. Sensitivity and specificity of the clinical carotid plaque protocol in detecting intraplaque hemorrhage were 95.0% and 94.4% respectively. Accuracy was 94.6%. The overall degree of agreement was excellent (kappa=0.87).

Conclusions: Addition of a 3D MPRAGE sequence to a standard neck MRA at 3T is highly accurate in detecting intraplaque hemorrhage when compared to gold standard neck MRA with surface coils.


Figure 1. 68/M with recurrent transient episodes of right sided weakness. Both the clinical carotid plaque protocol large FOV exam (A) and surface coil exam (B) demonstrate intraplaque hemorrhage. Degree of stenosis was 55% (C).

Figure 2. 66/M with an acute ischemic stroke in the left MCA territory. Both the clinical carotid plaque protocol large FOV exam (A) and surface coil exam (B) demonstrate intraplaque hemorrhage. Degree of stenosis was 30% (C).



— Ty Cashen3D TOF with Compressed Sensing for Peripheral Non-contrast MRA

⋅ ⋅ ⋅

° ×

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— Hou-Jen ChenCalf Reactive Hyperemia Indicates Severity and Predicts Functional Outcome of Limb Ischemia: a Pilot Study Using Arterial Spin Labeling and Model-based Analysis

Calf reactive hyperemia indicates severity and predicts functional outcome of limb ischemia:a pilot study using arterial spin labeling and model-based analysis

Hou-Jen Chen a, Graham A. Wright a,b

a Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada b Physical Sciences Platform and Schulich Heart Research Program, Sunnybrook Research Institute, Toronto, Canada

Purpose: To investigate the clinical relevance of calf reactive hyperemia measured by arterial spin labeling (ASL). Previously, reactive hyperemia in a small group of patients with peripheral arterial disease (PAD) was analyzed based on a physiological model (Fig. 1). Model-derived perfusion indices potentially reflect macrovascular disease and microvascular dysfunction in PAD. In this study, the clinical indications of limb ischemia and perfusion indices were directly compared. Specifically, the relationship between indices of macrovascular disease and microvascular dysfunction and symptoms, response to revascularization, and short-term functional outcome were assessed.

Methods: The mid-calf reactive hyperemia was recorded with an experimental ASL sequence [1] in the more symptomatic leg of 19 patients with PAD. Contralateral leg perfusion was also measured in 7 of them for bilateral comparison of relative disease severity. The subjects underwent 2 minutes of arterial occlusion via cuff inflation on their thigh. Imaging was performed at 3 Tesla with a receive array coil placed in the calf region. The responses were characterized by the empirical indices, i.e. peak and time-to-peak (TTP), and physiological model-derived indices [2]. The model indices included the baseline perfusion fr, arterial resistance Ra and compliance Ca, and microvascular sensitivity gATP and response time τATP to the hypoxia-induced ATP release by erythrocytes. The model-derived perfusion indices were estimated by fitting the model to the temporal signal response of reactive hyperemia. Meanwhile, the disease severity and outcome within 6 months after revascularization was assessed by self-reported symptoms and measures from the vascular lab exam, which included ankle-brachial index (ABI) and duplex ultrasound blood velocity. Disease severity was categorized as asymptomatic, claudication, or critical limb ischemia (CLI). The outcome was categorized as resolved ischemia or limited improvement, the latter of which indicated claudication or CLI remained after successful revascularization.

Results and Discussion In the subgroup who participated in the bilateral comparison, the more symptomatic leg had lower ABI, lower peak perfusion, and higher arterial resistance (Wilcoxon matched-pairs signed rank test; n=7, p<0.05). All the measured limbs were categorized based on the symptom severity. The result showed that the ABI and peak perfusion decreased and arterial resistance increased with increasing severity (Fig. 2a, Kruskal-Wallis test; n=25, p<0.05). Other indices did not show significant differences in the bilateral and severity comparisons. The average perfusion waveforms are shown in Fig. 2b. A total of 11 patients had a successful endovascular procedure where x-ray determined lumen area was restored to the stenosed artery, with ABI improving from 0.62 ± 0.14 to 0.89 ± 0.23 (paired t test; p=0.001); 4 patients had technical failure. All the treated target lesions were above the mid-calf. Five of the treated patients returned for post-intervention measurement of perfusion, which consistently showed higher peak perfusion but with variable degree of increase. The outcome assessment was available for 10 of the 11 treated patients; 6 patients had no walking limitation in daily life and 4 patients had remaining leg pain after the treatment. Comparing the two outcome groups, only the model-derived microvascular sensitivity gATP pre-intervention showed a significant difference (Fig. 2c, Mann-Whitney test; p<0.05). This suggests that functional outcome might be predicted from reactive hyperemia response measures before revascularization.

Conclusion This work showed that the characteristics of reactive hyperemia contain multiple aspects of the pathophysiology. Measures of arterial resistance are related to the manifested symptom severity, whereas microvascular dysfunction indices predict prognosis following revascularization. A future study with a larger patient population and longer follow-up period will be required to confirm the current findings.

References: [1] Kim SG, MRM 1997; [2] Chen HJ, SMRA 2016.

Fig. 1: Perfusion assessment using ASL and model-based analysis.

Fig. 2: (a) The measurement indices and (b) averaged reactive hyperemia waveforms in the groups with different severity of limb ischemia. (c) The perfusion indices in the two outcome groups.

a

b c



— Yalun ChenThe Atherosclerosis of Circle of Willis Detected by Black-blood MRI are Different Between Stroke Patients and Asymptomatic Controls

Figure 1. example of atherosclerotic palque identification and maximal plaque length (blue line) & thickness (red line) measurements on black-blood VISTA image.

The atherosclerosis of Circle of Willis detected by black-blood MRI are different between stroke patients and asymptomatic controls

Yalun Chen1,2, Le He2, Ling Tang2, Xihai Zhao2, Zhensen Chen2, and Huijun Chen2 1Chongqing Medical University, Chongqing, People's Republic of China, 2Department of Biomedical Engineering,

School of Medicine, Tsinghua University, Beijing, People's Republic of ChinaPurpose As the major intracranial collateral circulation pathway, circle of Willis (CoW) has attracted significant attentions. Previous studies has found that the integrity of CoW identified by angiography (MRA, CTA or DSA) may affect the occurrence and outcome of stroke1-3. However, the atherosclerosis of CoW and its association with stroke/ transient ischemic attack (TIA) has not been investigated. In this study, we sought to investigate the atherosclerosis of CoW using black-blood vessel wall MR imaging. Methods Population: After written informed consent was obtained, a group of patients (44 subjects with 27 males, mean±SD age=58±8.7 years) with ischemic stroke/TIA occurred within 3 months and a group of age&sex matched asymptomatic controls (44 subject with 27 males, mean±SD age=58±8.6 years) were recruited. MR imaging: All subjects were scanned on a Philips 3T scanner with a 32-channel head coil. A black-blood VISTA4 sequence (TR/TE 800/20 msec, FA 90, FOV 200 * 200 * 80 mm3, voxel size 0.6 * 0.6 *0.6 mm3, interpolated to 0.3 * 0.3 *0.6 mm3) was utilized for vessel wall imaging of CoW. Data analysis: An experienced neuroradiologist review the VISTA image of CoW. The prevalence and distribution of atherosclerotic plaque on CoW were reported and compared for both group. Moreover, the maximal length and thickness of each plaque on CoW were also measured (Fig 1) using the MPR tools in Philips work station. After two weeks, the same reviewer reviewed the data again for reproducibility evaluation. Statistical analysis: Intraclass correlation coefficient (ICC) and Chi-square test were used to evaluate the intra-reader reproducibility. The Chi-square test was used to compare the prevalence and distribution of CoW atherosclerotic plaque between two groups. The unpaired t-test was used to compare the plaque length and thickness. Results Totally, 41 plaques were detected on CoW in 28 patients (63.6%) in symptomatic group. In asymptomatic group, 11 CoW plaques were found in 8 subjects (18.2%), much lower than symptomatic group (p<0.01). The plaque distribution on CoW of the two groups have no significant difference (p=0.9), as shown in Table 1. In both groups, majority of the plaques were found in the P1 segment, the interface between BA and P1, and the interface between ICA and A1. But the most plaques were distributed at the P1 segment (36.5%) in symptomatic group, while in asymptomatic group, most plaques distributed at the interface between BA and P1 (45.6%). No plaque was found in AcomA, PcomA and LPcomA segments. The maximal length and thickness of CoW plaques in symptomatic group were higher than asymptomatic group, but not significant (plaque length: 3.34±1.54mm vs. 2.91±1.32mm, p=0.49; plaque thickness: 1.39±0.37mm vs. 1.31±0.34mm, p=0.62). The intra-reader reproducibility of the prevalence and distribution of CoW plaque was good (K=0.77 for prevalence, K=0.74 for plaque distribution). The intra-reader reproducibility of the CoW plaque length and thickness measurements were also good (ICC=0.84 and 0.87, respectively). Table1. Atherosclerotic plaque distribution on the CoW of patients

Plaque Distribution P1 A1 AcomA vs A1* PcomA vs ICA* ICA vs A1 BA vs P1

symptomatic group 36.5%(15/41) 4.9%(2/41) 2.4%(1/41) 4.9%(2/41) 22.0%(9/41) 29.3%(12/41)

asymptomatic group 27.2%(3/11) 0 0 0 27.2%(3/11) 45.6%(5/11)

* : plaque exists on the interface of two arteries. A1: first segment of anterior cerebral artery (between origin and the AcomA); P1:first segment of posterior cerebral artery (between origin and the PcomA); AcomA: anterior communicating artery, ICA: internalcarotid artery, PcomA: posterior communicating artery, BA: basilar artery.

Discussion and Conclusion In this study, for the first time, the prevalence, distribution and quantitative measurements of atherosclerotic plaque on CoW were reported. We found that the prevalence of atherosclerosis in symptomatic group was higher than asymptomatic group, while the distribution, maximal length and thickness of plaque was similar. The reproducibility results also suggest the feasibility and reliability of black-blood VISTA sequence in assessing the atherosclerosis of CoW.

References 1. Y-M Chuang, et al. J Crit Care. 2013. 2. H Zhou, et al. Medicine. 2016. 3. A.W.J. Hoksbergen,et al. Cerebrovasc Dis 2003. 4.Y Qiao Y, et al. J Mag Res Imag. 2011.



— J. Rock HadleyRF Coil for Comprehensive Neurovascular Imaging

RF Coil for comprehensive Neurovascular Imaging JR Hadley, MJ Beck, R. Merrill, S McNally, DL Parker

Departments of Radiology and Electrical Engineering, University of Utah Purpose

Vascular imaging is important in monitoring and managing the variations of vascular disease that lead to stroke or affect the basic function of the brain. Ischemic stroke, which affects 700,000 Americans each year, is a debilitating event with a large number of possible anatomic origins. Of these,160,000 are recurrent stroke, which is one of the strongest predictors of morbidity and mortality1. Because optimal treatment, to prevent recurrent stroke, depends on etiology, it is critical to determine the cause of the primary stroke. Imaging studies to determine sources of vascular disease are often performed with imaging modalities that cannot directly visualize disease components that are becoming validated asimportant stroke risk factors. A consistent imaging modality that can detect and classify all important stroke risk factors is critically needed. Atherosclerosis requires multimodal aggressive medical management, moyamoya can lead to surgical revascularization, vasculitis and infective endocarditis treatment focuses on the underlying inflammatory or infectious process and may require antibiotics, and reversible cerebral vasoconstriction syndrome (RCVS) and arterial dissection are often triggered by avoidable toxic or traumatic exposures 1-4. There are major research initiatives and multicenter trials addressing the need to improve diagnosis and treatment of cryptogenic stroke, but they are focused on cardioembolic stroke sources, which can only explain a fraction of cryptogenic stroke 5,6. Arterial stroke sources accounts for over half of all stroke etiologies, and presumably are the underlying pathology in a large percentage of cryptogenic stroke patients 7-9. The accurate detection of arterial pathology in the setting of stroke will lead to more successful secondary prevention 10.

Lumenography methods such as DSA and CTA have become the primary evaluation methods for quantifying lumen stenosis, which is the primary treatment discriminating factor. Although MRA can in principle provide the samelumenography, currently head/neck CE-MRA is not as robust as CTA, which can efficiently cover from the aortic archthrough the circle of Willis in a single contrast injection. A major deficiency of MRA systems has been the lack of highperformance RF coils that conveniently cover this complete territory. CTA, on the other hand, provides very limitedvisualization of additional stroke risk factors beyond stenosis, such as lipid-rich necrotic core, intraplaque hemorrhage, and post contrast plaque enhancement.

We previously demonstrated the concept of neck-shape-specific (NSS) RF coils that operate simultaneously withthe OEM head coil, and provide excellent coverage from the neck through the circle of Willis 11. However, additional coils are required to see the aortic arch. Although disease at the arch is less common, the omission of coverage eliminates the capability of the full evaluation of all neurovascular stroke sources. Here we present the complete RF coil system for full comprehensive evaluation from the arch through the circle of Willis.

Methods The NSS-RF coils have been designed for the Siemens 3G and 4G MRI scanners, which have two coil ports at

the left and right sides of the head coil. With adapters, each port allows 8 channels. This NSS coil design makesadditional channels available for an anterior Aortic Arch coil. For proof of principle, 3 additional preamps were added to the preamp boxes for Aortic arch coil elements. Each element is 5x10 cm and configured in a ladder coil array. These coil elements were mounted on a separate plastic former from the neck coil elements. The final imaging solution for imaging from the arch to the circle of Willis includes the OEM 20 channel head coil, the OEM posterior neck coils, the superior OEM spine array elements, and the NSS coils and new additional anterior arch array (shown in Figure 1).

References: 1. Chen SP et al. Reversible cerebral vasoconstriction syndrome: current and futureperspectives. Expert Rev Neurother 2011;11(9):1265-1276. 2. Hajj-Ali RA et al. PrimaryCentral Nervous System Vasculitis. In: Ms GSHMD et al, editors. Inflammatory Diseases ofBlood Vessels: Wiley-Blackwell; 2012. p 322-331. 3. Jauch EC et al. Guidelines for the EarlyManagement of Patients With Acute Ischemic Stroke A Guideline for HealthcareProfessionals From the American Heart Association/American Stroke Association. Stroke2013;44(3):870-947. 4. Scott RM et al. Moyamoya Disease and Moyamoya Syndrome. NewEngland Journal of Medicine 2009;360(12):1226-1237. 5. Lammie GA et al. Whatpathological components indicate carotid atheroma activity and can these be identifiedreliably using ultrasound? Eur J Ultrasound 2000;11(2):77-86. 6. Diener H-C et al. Design ofRandomized, double-blind, Evaluation in secondary Stroke Prevention comparing theEfficaCy and safety of the oral Thrombin inhibitor dabigatran etexilate vs. acetylsalicylic acidin patients with Embolic Stroke of Undetermined Source (RE-SPECT ESUS). InternationalJournal of Stroke: Official Journal of the International Stroke Society 2015;10(8):1309-1312.

7. Kolominsky-Rabas PL et al. Epidemiology of Ischemic Stroke Subtypes According to TOAST Criteria Incidence, Recurrence, andLong-Term Survival in Ischemic Stroke Subtypes: A Population-Based Study. Stroke 2001;32(12):2735-2740. 8. Marnane M et al.Stroke Subtype Classification to Mechanism-Specific and Undetermined Categories by TOAST, A-S-C-O, and Causative ClassificationSystem Direct Comparison in the North Dublin Population Stroke Study. Stroke 2010;41(8):1579-1586. 9. Meschia JF et al.Interobserver Agreement in the TOAST Classification of Stroke Based on Retrospective Medical Record Review. Journal of stroke andcerebrovascular diseases : the official journal of National Stroke Association 2006;15(6):266-272. 10. Bang OY et al. Evaluation ofCryptogenic Stroke With Advanced Diagnostic Techniques. Stroke 2014;45(4):1186-1194. 11. Beck MJ et al. Interchangeable neckshape-specific coils for a clinically realizable anterior neck phased array system. Magn Reson Med 2017.

Figure 1: NSS coil integrated with Arch coil array



— Rami HomsiAortic Stiffness, Epicardial Fat, Left Ventricular Myocardial Fibrosis and Contractility in Patients with Hypertension and Diabetes Mellitus

Preliminary experience with simultaneous arterial and venous high-resolution late-phase imaging of the run-offs using gadobutrol

Rami Homsi1, Patrick Kupzcyk1, Frank Träber1, Winfried Albert Willinek1, Hans Heinz Schild1, Dariusch Reza Hadizadeh1

1Radiology, University of Bonn, Bonn, Germany

Purpose: Three-dimensional contrast enhanced magnetic resonance angiography (MRA) is a routine application in the assessment of run-off vessels in patients with peripheral arterial disease (PAD) in many centers1,2. Late-phase high resolution imaging (LPMRA) with blood-pool contrast agents (BPCA) in the equilibrium phase (“steady state”) using gadofosveset trisodium has been shown to provide better delineation of arteries helping to prevent both under- and overestimation of stenosis grades and excellent venous delineation that allowed for the diagnosis of unexpected venous thromboses in many cases3,4. However, BPCA are currently not available on the market and steady state imaging became unavailable. Pre-clinical data on minipigs has suggested benefits of gadobutrol over a .5 molar contrast agent for venous imaging suggesting a possibly beneficial role for LPMRA. The purpose of this study was to assess image quality and contrast parameters of both arteries and veins in first pass and in LPMRA using the macrocyclic 1-molar contrast agent gadobutrol.

Methods: Nine patients (4 men, 5 women; mean age, 70 +/- 8.4 years) with suspected or known peripheral arterial occlusive disease underwent FPMRA after administration of a single dose of gadobutrol at 1.5 Tesla and immediately afterwards LPMRA in the order 1.calfs, 2. upper legs, 3. pelvis. Technical parameters for first-pass imaging (FPMRA) were as follows: TR/TE, 2.9-4.1; slices, 94-117; acquired voxel, 1.73-2.40 mm³; acquisition time, 8.9-34.1s; FOV, 450mm². Those for LPMRA: TR/TE, 6.1-6.4; slices, 237-280; acquired voxel, 0.36-0.43mm³; acquisition time, 206-221s5; FOV, 450mm². In 3/9 patients catheter angiographies of the lower extremities were available for comparison. Two investigators with >5yrs. of experience in MRA evaluated the image quality of arteries in FPMRA and both arteries and veins in the run-off vessels. Arteries were evaluated regarding the visibility of plaques and stenosis grades, whereas veins were evaluated with respect to their delineation, the assessability of thrombosis and the ability to differentiate arteries from veins on a 3-point scale. Quantitative analysis was performed by calculation of contrast-ratios (CR) = (A - B) / (A + B) of vessel lumen compared to adjacent muscle and fat with A being the vessel lumen of the vessel of interest and B adjacent muscle or fat.

Results A total of 111 arterial segments were available for intra-individual comparison of FPMRA and LPMRA and 130 venous segments were evaluated in LPMRA. Delineation of vessel walls/atherosclerotic plaques was rated significantly higher in LPMRA than in FPMRA (1.75±0.47 vs. 1.05±0.42; P<0.05). Ability to confidently rule out stenosis was rated similarly high with both methods in the calfs and upper legs (>90.2-100%), whereas in the pelvis region, FPMRA was rated significantly higher (P<0.05). Delineation of veins and the ability to differentiate them from arteries as well as the ability to rule out thrombosis were rated high in the upper legs and epifacial veins of the entire leg, but only average in the veins of the pelvis and calfs. In 7/111 arterial segments, LPMRA and FPMRA stenosis grading differed due to partial volume effects in FPMRA (figure). Incidental thrombosis was found in one patient in the posterior tibial vein. Vessel to both fatty tissue and muscle CR were significantly higher in FPMRA compared to LPMRA (p<0.05). In LPMRA there were no significant differences regarding arterial and venous vessels.

Discussion As expected, CR was significantly higher for FPMRA compared to LPMRA. Nevertheless, high-spatial-resolution LPMRA with gadobutrol led to a significantly better delineation of the vessel wall that allowed better stenosis grading and visualization of veins and led to the diagnosis of an incidental thrombosis not visible in FPMRA. The latter is in line with earlier results revealing incidental thromboses in up to 10% of patients. LPMRA may therefore serve as a valuable add-on in imaging of the run-off vessels.

Figure: 59 year old female with peripheral arterial occlusive disease Fontaine Grade II

A: subtracted MIP of the upper legs shows irregularities, but now major stenosis.

B: Non-subtracted transversal multiplaner-reformat of FPMRA shows no stenosis at the position of the arrow in A.

C: Transversal multiplaner-reformat of LPHRMRA at the same lodcation as B reveales high grade stenosis caused by a plaque at the medial vessel wall.

References: 1: Willinek WA et al. Stroke 2005;36:38–43; 2: Prince MR et al. J Magn Reson Imaging 1993;3: 877–881; 3: Hadizadeh DR et al. Radiology 2008;249(2):701-11; 4: Hadizadeh et al. AJR Am J Roentgenol. 2012 May;198(5):1188-95 5: Homsi et al. Magn Reson Imaging. 2015 Nov;33(9):1035-42


1.Preferred presentation: oral

2.Scientific categories for your presentation: Contrast media, High-resolution MRA, venous imaging

3.Synopsis:

Late-phase high resolution imaging (LPMRA) with blood-pool contrast agents has been shown to be superior in the evaluation of both arteries and veins in dynamic 3D-MRA. However, the possible value of the macrocyclic 1-molar contrast agent gadobutrol for LPMRA has not yet been investigated. This study assesses parameters of image quality of both arteries and veins of gadobutrol-enhanced LPMRA in comparison to first-pass MRA (FPMRA). Though contrast ratios were higher in FPMRA, LPMRA with gadobutrol allowed for better vessel wall delineation, stenosis grading and visualization of veins and may thus serve as a valuable add-on in imaging of run-off vessels.



— Tim LeinerTowards a 256-channel Cardiac Receive Coil Array to Facilitate One Order of Magnitude Faster Cardiac MR

Purpose: Today’s Cardiac Magnetic Resonance Imaging (CMR) protocols can be time consuming, expensive, and uncomfortable for the patient, especially in multi parametric protocols that aid diagnosis. In order to substantially accelerate the image acquisitions, high-density receiver coil arrays [1-3] may be used. Increasing the density of coils coincides with reducing the coil size, which in turn will reduce tissue loading and therefore can reduce noise. As long as tissue load remains dominant, the density of loop elements can be increased without substantially adding noise to the signal [4]. In this study, we have investigated the feasibility and performance of high-density coil arrays for accelerated cardiac MRI [5-7] to investigate the possible acceleration performance of a 256 Channel digital Cardiac Coil Array at 3 Tesla.

Methods: A prototype 32-element coil array (2x16) (MR Coils BV, Zaltbommel, The Netherlands) with loop sizes of 55 mm in length and 33 mm in width (Fig.1) was designed. Measurements were performed on a Philips 3T wide bore system with digital receivers (Philips, Best, The Netherlands). Coil sensitivity maps were recorded using the standard Philips SENSE reference scan (resolution = 6 mm isotropic). A separate noise scan was obtained by switching of the RF transmit power to perform signal-to-noise (SNR) measurements. To simulate the expected improvement in acceleration of the 256 Channel Cardiac Array, the measurements were repeated 8 times, each time with the 2x16 channel array’s positioned at different locations around the chest of the patient (Fig. 2a). G-factor maps of a 3D acquisition were calculated with SENSE accelerations in FH-LR, LR-AP and FH-AP directions using the aligned sensitivity maps and the noise matrix.

Results: The noise correlation matrix of the 32 channel array in the position shown in Fig2 ab is shown in Fig. 3a. After alignment and merging the 8 acquisitions obtained with the 8 times 32 elements, good penetration of the reception is obtained throughout the body (Fig. 2c-f) with SNR levels comparable to the normal vendor setup (Fig. 2g-h). SENSE acceleration can go up to 5 in 2D, or 5x6 in 3D acceleration (Fig. 3b).

Discussion: We have demonstrated that the coil elements that can be used for a high-density 256 Channel Cardiac Array remain in tissue load dominance. It should be noted that the results are obtained with only 32 elements physically present during each scan. Consequently, potential coupling between elements in a full 256 Channel array have not been incorporated. However, average coil couplings within the 32 channel prototype were low. Potential mage acceleration of over 20 can be obtained with SENSE encoding. Consequently, these calculations demonstrate the motivation to build the 256 Channel digital Cardiac Array Coil to facilitate a boost in acceleration of the multi parametric cardiac MRI.

Fig 1: The coil design and the realisation of a 32 channel prototype. a) Coil design. All hardware is integrated in the MRI table top. b) the 32 channel prototype which is onethird of the table top. c) coil positioning on avolunteer in the scanner

Fig 2: a) Coil placements. b)signal and noise from single coil loop. c) sum of squares signal of 32 channel array. d) sum of squares signal for virtual 256 channel coil array

Fig 3: a) the noise correlation of each coil element with the other coils. b) g-factor maps of the virtual 256channel coil in the sagittal view withacceleration in the LR (columns) andFH (rows) direction. For SENSE 5x6the max g-factor remains below 1.5

Referecnes: 1. Roemer P.B. et al., MRM 16 (1990): 192-225. 2. Schmitt M. et al., MRM 59 (2008): 1431-1439. 3. Etzel R. et al.,ISMRM 2015:1780. 4. Schuppert M. et al., ISMRM 2015:1779. 5. Sodickson D.K. et al., MRM 38 (1997): 591–603. 6. Pruessmann K. P. et al., MRM 42 (1999): 952–962. 7. Griswold M.A. et al., MRM 47 (2002): 1202–1210.



— Sébastien LevillySpatio-temporal Filtering of Blood Flow in 4D Phase-contrast Magnetic Resonance Imaging

Spatio-temporal filtering of blood flow in 4D Phase-Contrast MRI

Sébastien Levilly1, Jérôme Idier1, Félicien Bonnefoy2, David Le Touzé2, Perrine Paul-Gilloteaux3, Saïd Moussaoui1, Jean-Michel Serfaty4

1Laboratoire des Sciences du Numérique de Nantes (LS2N), 1 rue de la Noë, BP 92101, 44321 Nantes Cedex 3, France

2Laboratoire de recherche en Hydrodynamique, Énergétique, et Environnement Atmosphérique (LHEEA), 1 rue de la Noë, BP 92101, 44321 Nantes Cedex 3, France

3CNRS, SFR Santé François Bonamy UMS 3556, IRS-UN, 8 quai Moncousu, BP 70721, 44007 Nantes Cedex 1, France

4UF Imagerie Cardiaque et Vasculaire Diagnostique, CHU de Nantes, France

Purpose4D PC-MRI allows spatio-temporal imaging of the blood-flow velocity in a region of interest such as the aortic system during a cardiac cycle [1]. However, the resolution and the signal-to-noise ratio (SNR) are limited by acquisition constraints. In order to improve the SNR, the regularization of the blood-flow velocity field is possible by introducing a physical constraint such as incompressibility [2]. It results in a spatial-only regularization without considering time evolution. The proposed method applies a spatio-temporal regularization through the incompressibility constraint and temporal quadratic penalization.

MethodsWe formulate the problem as the minimization of the sum of a fidelity-to-data term and a time penalization term under the constraint of incompressibility. For the sake of simplicity, both terms are assumed quadratic. The incompressibility hypothesis results in forcing the velocity field to be divergence-free and this problem has been solved by Song et al. [2] through the determination of an orthogonal projector onto the space of divergence-free field. The problem can be simplified by applying this projection to the data field. The optimal solution of this spatio-temporal regularization results in the application of two filters: a divergence-free one and a temporal one. The incompressibility projection, being a spatial filter, can be applied in parallel to each sample time with effective filtering techniques.

Results & DiscussionThis work has been tested on synthetic data. We use the Womersley simulation model [3] in a tube of 1 cm radius with a realistic cardiac flow rate [4]. Our filtering solution improves significantly the signal-to-noise ratio. It reveals that the time dependence of the fluid flow has to be considered in the problem. Nevertheless, we noticed some discrepancies close to thetube walls which might come from the coarse resolution. This error might have a significant impact on some local biomarkers such as the wall shear stress. Dealing with a thinner grid could reduce the error on the wall and enhance biomarkers precision.

References[1] M. Markl, A. Frydrychowicz, S. Kozerke, M. Hope et O. Wieben, « 4D flow MRI », J. Magn. Reson.Imaging, vol. 36, n°5, pp. 1015-1036, 2012.[2] S. M. Song, S. Napel, G. H. Glover et N. J. Pelc, « Noise reduction in three-dimensional phase-contrast MR velocity measurements », J. Magn. Reson. Imaging, vol. 3, n°4, pp.587-596, 1993.[3] J. R. Womersley, « Method for the calculation of velocity, rate of flow and viscous drag in arterieswhen the pressure gradient is known. », J. Physiol., vol. 127, n°3, pp. 553-563, 1955.

or blood flow usingRunge-Kutta discontinuous Galerkin methods », Appl. Num. Math., vol.115, pp. 114-141, 2017.



— Dong Woo ParkPerfusion Abnormality in Posterior Inferior Cerebellar Artery Termination of Vertebral Artery on Arterial Spin Labeling and Dynamic Susceptibility Contrast Perfusion MRI



— Vitaliy RayzOntological Approach to Detecting Imaging Artifacts in MRA images



— Emma RoditiBody Shape Index, Left Ventricular Remodelling and Atherosclerosis — An Observational Study

Body Shape Index, Left Ventricular Remodelling and Atherosclerosis - An Observational Study

Emma K Roditi, Jonathan R Weir-McCall, Stephen J Gandy, Matthew Lambert, Jill JF Belch, Ian Cavin, Roberta Littleford, Jennifer A Macfarlane, Shona Z Matthew, R Stephen Nicholas, Allan D Struthers, Frank

Sullivan, Shelley A Waugh, Richard D White, J Graeme Houston.

Purpose : Obesity, conventionally measured via Body Mass Index (BMI), has become an increasing problem worldwide and a major cause of morbidity and mortality across the globe

(1). However BMI does not

take into account the differential distribution of body fat, ignoring the greater risk associated with central adiposity than peripheral adiposity. A Body Shape Index (ABSI) is a novel parameter for body shape which encompasses both BMI and waist circumference (WC). The waist:height (wst:ht) ratio is another alternative held to be simpler to calculate and more accurate as it takes into account central adiposity. The aim of this study is to compare BMI, ABSI and Wst:Ht in their ability to predict atherosclerotic burden and adverse cardiac remodelling.

Methods : 1489 participants of the TASCFORCE study (62% female, 54.1 ± 8.3 years) underwent whole body MRA and a cardiac MRI. All were free from hypertension, diabetes and with a <20% 10 year cardiovascular risk. A standardised atheroma score (SAS) was calculated by scoring 30 vessels 0-4 according to the degree of stenosis and then summating these. The left ventricle was classified as either normal, concentric remodelling (increased mass:volume ratio), concentric remodelling with hypertrophy (increased mass:volume ratio and mass), and eccentric remodelling (increased mass and Left ventricular remodelling and atherosclerosis bend diastolic volume). These were then compared across the different body parameters : Body Mass Index (BMI), Waist-to-Height Ratio (Wst:Ht) and Body Shape Index (ABSI).

Results : BMI and Wst:Ht ratio both increased with increasing severity of left ventricular remodelling, with no significant difference in ABSI across categories of ventricular remodelling (see table 1).

Table1: ANOVA of Body Parameters against Remodelling Categories

*= p <0.05, compared to Normal ; = p <0.05, compared to Concentric Remodelling with Normal LV Mass ; ◇ = p <0.05, compared toConcentric Remodelling with Increased LV Mass ; ■ = p <0.05, compared to Eccentric Remodelling with Increased LV Mass

Spearman’s correlation was performed for each body parameter in relation to SAS. The only statistical significance (R=0.097, p = 0.020) found was between SAS and ABSI in males which was not evident in females. No significant correlation was seen between SAS and BMI or Wst:Ht. Similarily, if the cohort was split was split into normal weight and overweight groups according to BMI (BMI <30 versus >30), Wst:Ht (<0.5 versus >0.5) and ABSI (<0.081 and >0.081) there was no difference in SAS other than in males using ABSI (p=0.036).

Discussion : ABSI was a poorer predictor of ventricular remodelling than simpler metrics of body size such as BMI or Wst:Ht ratio. No measure of body size could accurately predict the extent of atheroma burden in this low-intermediate cardiovascular risk population.

References : 1. WHO | Obesity WHO. World Health Organization; 2016; http://www.who.int/topics/ obesity/en/ ; 2. WHO | Obesity and overweight. WHO. World Health Organization; 2016; http:// www.who.int/mediacentre/factsheets/fs311/en/

Normal Concentric Remodelling with Normal LV Mass

Concentric Remodelling with Increased LV Mass

Eccentric Remodelling with Increased LV Mass

BMI Males 26.87 (26.58-27.16) 26.45 (24.60-28.31) 31.12* (29.62-32.63) 23.21◇ (18.30-28.14)

BMI Females 26.21 (25.92-26.51) 27.38 (25.65-29.11) 31.53* (29.94-33.12) 31.34* (26.20-36.49)

Wst:Ht Males 52.30 (51.86-52.80) 53.31 (49.32-57.30) 56.25* (53.58-58.92) 45.09◇ (38.22-51.97)

Wst:Ht Females 42.55 (42.07-43.03) 44.37 (41.58-47.16) 50.78* (48.08-53.47) 51.09* (41.93-60.25)

ABSI Males 0.0774 (0.0770-0.0779) 0.0795 (0.0754-0.0836) 0.0754 (0.0735-0.0774) 0.0733 (0.0656-0.0821)

ABSI Females 0.0733 (0.0729-0.0736) 0.0761* (0.0735-0.0787) 0.0735 (0.0719-0.0751) 0.0765 (0.0727-0.0803)



— Monica SigovanRespiratory-resolved Self-gated 3D Radial 4D Flow MRI: Initial Results

Respiratory-resolved self-gated 3D radial 4D flow MRI: Initial results

M. Sigovan1, T. Schneider2, G. Cruz3, C. Mory1, R. Botnar3, L. Boussel 1,4, P. Douek1,4, C. Prieto3

1 University of Lyon, CREATIS Laboratory, Lyon, France 2 Philips Healthcare, Guildford, UK

3 Division of Imaging Sciences and Biomedical Engineering, King’s College London, London, UK 4 Department of Interventional Radiology and Cardio-vascular and Thoracic Diagnostic Imaging, HCL, Lyon, France

Background: Despite the high potential of four-dimensional (4D) flow MRI, its clinical use is hampered by long acquisition times, due in part to the need of navigator-based respiratory gating. Respiratory self-gating has the potential to reduce acquisition times if combined with motion correction and moreover enables velocity measurements at different phases of the respiratory cycle.

Purpose: Develop a respiratory self-gated 3D radial 4D flow MRI sequence and study the respiratory related variability of flow velocity in the thoracic aorta.

Materials and Methods: A 4D flow MRI sequence based on a spiral phyllotaxis pattern for 3D radial k-space sampling [1] was implemented on a 1.5T Philips Ingenia system. 4D flow imaging was performed on 3 healthy volunteers and consisted of a fast field echo interleaved acquisition, 8 projections per interleaf, turbo factor 8, TR/TE 6/2.5 ms, isotropic FOV 340 mm, 2.5 mm isotropic acquisition voxel, flip angle 6◦, and receiver bandwidth 723 Hz. A total of 54096 radial readouts were acquired in 6762 interleaves. Each projection was repeated 4 times for velocity measurements using Hadamard encoding scheme. The respiratory self-gated (SG) signal was derived independently for each velocity encoding step as the time variation of the z coordinate of the center of mass of the image[], computed from the first projection of each interleaf using a conjugate gradient method with L1 regularization. Using the respiratory SG signal, data was separated in 3 respiratory bins with equal number of projections. Subsequently, each respiratory phase was binned in 8 cardiac phases using the ECG signal. Respiratory- and cardiac-resolved images were reconstructed offline using a standard gridding algorithm and velocity images were computed using complex phase subtraction. Blood flow velocities were measured at different locations in the thoracic aorta. Results: All datasets were reconstructed successfully with minimal residual breathing artefacts. Respiratory amplitude of around 1 cm was observed. Time average velocity values in the thoracic aortas of the three volunteers varied between respiratory phases, from 59 ± 14 cm/s in phase 1 (corresponding to inspiration), to 57 ± 10 cm/s in phase 2, and 49 ± 5 cm/s in phase 3 (expiration).

Discussion: We presented a respiratory and cardiac resolved 4D Flow MRI sequence based on a 3D radial trajectory. Our preliminary results highlighted respiratory cycle related velocity variations, but will have to be confirmed with a Cartesian 4D flow sequence. This work is ongoing.

References: [1] D. Piccini et al, Magnetic Resonance in Medicine 66:1049–1056 (2011)[2] O. Wieben et al, Proc. Intl. Soc. Mag. Reson. Med 9 (2001) #737



— Julia VelikinaHighly Accelerated Dynamic MRI Using Information-based, Rank-adaptive Reconstruction

Highly Accelerated Dynamic MRI Using Information-Based, Rank-Adaptive Reconstruction Julia V Velikina, Alexey A Samsonov

University of Wisconsin – Madison, Madison, WI, USA Introduction: Dynamic MRI must contend with imaging time limits imposed by physiological and physical constraints. Many methods for dynamic MRI acceleration1-4 rely on the assumption that temporal signal can be approximated by a lower-dimensional model. However, restricting the model rank promotes a low-rank solution which compromises temporal fidelity and diagnostic information. Conversely, increasing the model rank deteriorates image quality as overfitting causes increase in noise and artifacts4. In this work, we recognize that temporal behavior varies significantly in the object ranging from simple (e.g., in static tissues) to complex (e.g., due to contrast accumulation or cardiac motion). To accommodate these differences, we propose a new method, which adapts model spatially during reconstruction and simultaneously refines temporal basis to preserve high temporal fidelity and achieve high reconstruction quality compared to existing state-of-art techniques. Theory: We adapt MOdel Consistency COndition (MOCCO) reconstruction4 that finds image series ( , ) p tn n

ks x tS C by

solving *2 2

min K tvectSS ES d s UH U I [Eq. 1], where s is the row of S corresponding to th pixel, E is the

joint encoding matrix for all time frames, d is a stacked vector of k-space data, It is the nt x nt identity matrix. U comprises temporal principal components (PCs) pre-estimated from fully-sampled k-space center, from which the first K PCs are selected by diagonal filter matrix KH to form a low-rank model. In the standard formulation, model order K is assumed to be low and spatially invariant. In our method, we allow K to vary within the full range. To guide the model rank selection for a given pixel, we identify the minimal K sufficient for an accurate representation of the pixel’s temporal dynamics utilizing the Bayesian information criterion (BIC)5, which for dynamic imaging is: *

2, = ln 1 lnt K t tBIC K n K ns s UH U I . The BIC

measures model’s efficiency by estimating the likelihood of the data being described by the model (the first term) while penalizing its complexity K. As pixel dynamics are not known beforehand, we start with non-regularized solution of Eq. [1], determine model order for th pixel as the one with minimum BIC value, argmin ,KK BIC K s [Eq. 2], and then alternatesolving Eq. [1] with refining PCs from the image series estimate and model order updates (Eq. [2]) until convergence. Results: Dynamic contrast-enhanced myocardial perfusion data were acquired on a 1.5T Siemens Sonata (saturation recovery TrueFISP, TR/TI=2.3/90 ms, FA=50°, 40 frames, 8-channel coil). Cardiac CINE data were acquired on 1.5T Siemens Aera (prospectively triggered breath-hold bSSFP , TE/TR=1.56/3.1 ms, FOV=360x360 mm, 360x210 matrix, 26 phases, 32-channel array). The fully-sampled images were obtained by combining the coil images6. Subsampled k-space data (2D VD random sampling, acc. factor R=4.3) were reconstructed using standard MOCCO, proposed adaptive MOCCO and adaptive blind compressed sensing (Blind CS)2. All reconstructions were optimized to yield minimized root-mean-squared errors. Figure 1 shows cardiac perfusion reconstruction results. All techniques except the proposed method produce significant errors. For cardiac CINE (Fig. 2), the proposed adaptive method demonstrated excellent preservation of temporal dynamics, which are noticeably blurred by the standard low-rank method. Discussion: We presented a novel model-based reconstruction approach that exploits statistical machinery to spatially adapt the model to the underlying signal. It overcomes deficiencies of low-rank techniques to preserve complex temporal dynamics of physiological processes. The ideas can be extended to other applications, including model-based parameter mapping, where multiple models may exist (e.g., in T2 mapping, single-exponent, two-exponent, and constant models to describe CSF, neural tissues, and background, respectively). References: [1] Liang ZP. In: Proc. of IEEE ISBI. Washington, DC, USA, 2007:988–91. [2] Lingala SG et al. IEEE Trans Med Imaging 2013;32:1132–45. [3] Otazo R et al. Magn Reson Med, 2015;73(3):1125-36. [4] Velikina JV et al. Magn Reson Medicine, 2015;74(5):1279-90. [5] Schwarz GE. Annals of Statistics, 1978;6(2):461–4. [6] Walsh DO et al. Magn Reson Med 2000;43:682–90.

Figure 1. Performance of the proposed adaptive MOCCOcompared to non-adaptive (K=4) and Blind CS methods fortwo representative time frames (1st column). The image differences are shown in x6 range.

Figure 2. Reconstruction of cardiac CINE dataset using standard (K=4) and proposed adaptive techniques.



— Xihai ZhaoAtherosclerotic Diseases in Entire Craniocervical Arteries from Aortic Arch to Intracranial Arteries and Stroke Risk: A 3D Multicontrast MR Vessel Wall Imaging Study

Atherosclerotic Diseases in Entire Craniocervical Arteries from Aortic Arch to Intracranial Arteries and Stroke Risk: A 3D Multicontrast MR Vessel Wall Imaging Study

Xihai Zhao1, Dongye Li1, Wei Dai2, Guoen Yao2, Huijun Chen1, Rui Li1, Chun Yuan1,3 1. Center for Biomedical Imaging Research, Tsinghua University, Beijing, China.

2. Department of Neurology, PLA 304 Hospital, Beijing, China.3. Department of Radiology, University of Washington, Seattle, USA.

Purpose: Disruption of vulnerable atherosclerotic plaques in entire craniocervical arteries, including aortic arch[1], extracranial carotid artery[2], and intracranial arteries[3], plays the key roles in ischemic stroke. This study sought to investigate the characteristics of atherosclerotic disease in the entire craniocervical arteries from aortic arch to intracranial arteries and their relationships with stroke risk using 3D multicontrast MR vessel wall imaging techniques. Methods: Fifty-two patients (mean age, 56.3 13.4 years; 38 males) with recent cerebrovascular symptoms were enrolled and underwent multicontrast MR vessel wall imaging for entire craniocervical arteries. MR imaging: The MR imaging was performed on a 3.0T Philips MR scanner (Achieva TX, Best, The Netherlands) and custom-designed 36-channel coil with three imaging sections: intracranial artery: 3D T1-VISTA[4] (TR/TE 800/20 ms; isotropic resolution0.6 mm) and 3D SNAP[5] (TR/TE 10.1/5.6 ms; isotropic resolution 0.8 mm); extracranial carotid artery: 3D MERGE[6]

(TR/TE 9.3/4.3 ms; isotropic resolution 0.8 mm) and 3D SNAP (TR/TE 10.0/4.7 ms; isotropic resolution 0.8 mm); aorticarch: 3D PD-VISTA (TR/TE 1000/20 ms; resolution 1.25x1.25x1.8 mm3) and 3D SNAP (TR/TE 9.4/5.3 ms; resolution1.25x1.25x1.6 mm3). A routine protocol was performed for brain imaging by acquiring T1W, T2-FLAIR and DWIsequences. The study protocol was approved by institutional review board and written consent form was obtained fromeach subject. Image analysis: intracranial artery, extracranial carotid artery and aortic arch MR images were reviewedseparately by experienced radiologists. Presence/absence of atherosclerotic plaque and intraplaque hemorrahge (IPH)was determined at each vascular bed. The maximum wall thickness (Max WT) and luminal stenosis of each plaquewere measured. Presence/absence of acute ischemic lesion (AIL) on DWI images was evaluated. Statistical analysis:The prevalence of plaques and IPH at each vascular bed was calculated. The correlation between atheroscleroticplaques in entire craniocervical arteries and AIL was determined.Results: Of 52 patients, 25 (48.1%) had AILs, and 21 (40.4%), 29 (55.8%), and 11 (21.2%) had plaques in intracranialartery, extracranial carotid artery, and aortic arch, respectively (Fig. 1). Intracranial arteries had the highest prevalenceof IPH and severe stenosis (>50% stenosis), followed by extracranial carotid arteries and aortic arch (Fig. 1). Indiscriminating presence of AIL, the odds ratio (OR) of Max WT of anterior circulation intracranial artery was 6.96 (95%confidence interval [CI], 1.09-44.36; p=0.040) and 6.64 (95% CI, 1.05-42.00; p=0.044) before and after adjusted forluminal stenosis. After adjusted for both stenosis and traditional risk factors, this association remained statisticallysignificant (OR, 9.49; 95% CI, 1.09-82.01; p=0.041). ROC analysis revealed that Max WT of anterior circulationintracranial artery had the highest AUC value (AUC=0.71), followed by posterior circulation intracranial artery(AUC=0.60), extracrannial carotid artery (AUC=0.53), and aortic arch (AUC=0.48) in discriminating presence of AIL (Fig.2). Fig 3 represents examples of high risk plaques in intracranial artery (a-d, arrows), carotid artery (f-g, arrows), andaortic arch (h-i, arrows) with hyperintense IPH on SNAP images and AILs on DWI in the same patient of Fig. 3a-d.

Discussion and Conclusions: In this study population, atherosclerosis and IPH were most prevalent in intracranial arteries across entire craniocervical arteries. The maximum wall thickness of anterior circulation intracranial artery was the strongest independent indicator for cerebral acute ischemic lesions among entire craniocervical vascular beds. References: [1] Circulation. 2009;119:2376-82. [2] JAMA. 2004;292:1845-52. [3] Lancet. 2014;383:984-98. [4] Magn Reson Med. 2016;75:831-8. [5] Magn Reson Med. 2013;69:337-45. [6] Magn Reson Med. 2011;65:627-37.


SMRA 2018www.smrangio.org

30th Annual International ConferenceA SuperCool MRA Experience

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Thursday, August 30th

Friday, August 31st

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Scientific Program Chair: Aleksandra Radjenovic

Endorsed by: University of Glasgow

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