Advances in Musculoskeletal Imaging

❖Barry G. Hansford, MD❖Oregon Health & Science University ❖Associate Professor Radiology

❖Musculoskeletal Radiology Fellowship DirectorOHSU

Overview

MR Neurography

Dual Energy CT

Low Dose Screening CT

Limited and Rapid MRI Protocols

Metal Artifact Reduction Sequence (MARS) MRI

OHSU

MR Neurography

Increasingly used to evaluate peripheral nerve disease

Advantages of MR Neurography over Traditional Diagnostic Imaging 1.) Precise assessment of neuromuscular anatomy

2.) Localize neuropathy

3.) Show extent and nature of neuromuscular abnormality or nerve injury

4.) Identify organic lesions

5.) Evaluate adjacent joint or tendon derangement that could predispose or contribute traction neuropathy

OHSU

MR Neurography

Just one piece of the diagnostic puzzle

MR Neurography must be used in concert with clinical history and electrodiagnostic information

MR Neurography can guide surgical planning, nerve blocks, and tissue sampling when necessary

MR Neurography has high negative predictive value

-Normal nerves in case of suspected neuropathy can favor psychological or psychosomatic etiology over organic cause in chronic pain patient

OHSU

MR Neurography

When to Order/Proper Clinical Indication for MR Neurography?

Peripheral nerve pathology can be classified as 1) Local versus 2) Systemic

Systemic broad category including: -Vasculitidies-Radiation-induced neuropathy/plexopathy-Metabolic Disease (DM, hyperlipidemia, amyloidosis)-Neurocutaneous syndromes (NF and schwannomatosis) -Infection such as viruses -Hereditary disease (Charcot-Marie Tooth)-Acute or chronic demyelinating disease (CIDP)-Idiopathic disease (Multifocal motor neuropathy)

OHSU

MR Neurography

Systemic Peripheral Nerve Disease

-Result in multifocal/multicompartmental neuropathy -Typically clinical diagnosis -Biochemical markers and electrodiagnostic tests

Role of MR Neurography in Systemic Peripheral Nerve Disease

Limited to problem-solving applications:

-Clinical suspicion of mass lesion -Worsening focal neuropathy -Suspicion of primary or superimposed nerve entrapment

OHSU

MR Neurography

Local Peripheral Nerve Disease

Neuropathies secondary to: -Trauma-Compressive neuropathies (tunnel syndromes at specific anatomic locations)-Traction neuropathies (repetitive activities, bad footwear, ankle instability)-Functional compartment syndromes-Neoplastic conditions (perineural tumors or PNSTs)-Focal infection

Role of MR Neurography in Local Peripheral Nerve Disease

-Primary investigative modality

OHSU

MR Neurography

Do I need to order MR Neurography with intravenous (IV) contrast? -MR Neurography is performed without IV contrast unless suspicion for 1) tumor or 2) infection

What the Radiologist Looks for on MR NeurographyOHSU

MRI 101

T1 = Fluid Dark

T1 Anatomy

T2 = Fluid Bright

T2 Pathology

OHSU

MR Neurography

Iatrogenic Fibrotic Entrapment Neuropathy of Sciatic and Pudendal Nerve: 41 y/o female history of complicated vaginal delivery presented with pain and swollen feeling of perineum

Fibrotic bands and scar tissue along right posterolateral pelvic wall in close proximity to course of sciatic and pudendal nerves

Asymmetrically T2 bright right sciatic nerve (thick arrow), right pudendal nerve (thin arrow), and its inferior hemorrhoidal branch (small arrow)

Ax T1

Ax T2 FS

DTI

OHSU

MR Neurography

Neuroma In-Continuity Common Peroneal Nerve: 23 y/o man with worsening foot drop and calf pain several months after posterolateral corner injury of the knee

Axial T2 FS mildly bright tibial nerve (arrowhead) in keeping with stretch injury and markedly enlarged hyperintensecommon peroneal nerve (CPN) with disrupted fascicles (short arrow)

Coronal DWI MIP shows normal caliber CPN distally

Ax T2 FS Cor DWI MIPOHSU

MR Neurography

Traumatic Neurotmesis of the Ulnar Nerve: 21 y/o man traumatic forearm injury

Soft tissue edema and hemorrhage (white arrow) at site of injury with thickening of the ulnar nerve (black arrow) and probable nerve discontinuity (arrowhead). DWI shows two hyperintense dots corresponding to ulnar nerve and hematoma

Ax T2 FS Cor STIR Ax DWI

OHSU

MR Neurography

Sciatic Nerve Stump Neuroma in 67 year-old man h/o left transfemoral lower limb amputation after muscular sarcoma recurrence

Focal lesion (arrow) at distal edge of sciatic nerve edge, lesion has moderate diffusion restriction with intermediate ADC consistent with neuroma

Morphologic and functional continuity of the lesion with the proximal left sciatic nerve

Ax STIR Ax DWI Ax ADC

Cor MIP

OHSU

MR Neurography

Sciatic Nerve Perineurioma: 13 y/o boy with foot drop for many months

Enlarged common peroneal nerve component of sciatic nerve (arrow), denervation changes at anterior compartment (arrows)

Ax T2 FS Ax T2 FS Cor FS DWI

OHSU

Dual Energy CT

Gout and Beyond…

Dual energy CT (DECT) works by simultaneously scanning the subject at two different energy levels using two X-ray sources and corresponding detector arrays within same gantry

-Measurable attenuation difference between urate and calcium

-Urate and calcium can be coded with different colors and fused over regular gray scale to create map of urate within body

Sensitivity = 78 to 100%Specificity = 89 to 100%

OHSU

Dual Energy CT

When should I order dual energy CT for evaluation of gout?

Gold standard for diagnosis of gout is aspiration of monosodium urate crystals

If fluid not obtained: 1.) Disease manifestation, 2.) serum urate levels, and 3.) radiologic findings often adequate for clinical diagnosis

Diagnosing gout straightforward, DECT reserved for challenging cases:

1) Unusual clinical presentation 2) Acute gouty attack with normal serum urate levels3) Active attack (rather than sequela of chronic disease)4) Hyperuricemia with an inflammatory disease that mimics gout

OHSU

Dual Energy CT

OHSU

Dual Energy CT

Patellar Gout in 87 y/o man with anterior knee pain, elevated serum uric acid level, no pain in any other joints, and no history of gout

-Lytic lesion (arrow) superior pole of patella

-Non-specific intermediate deposit on PD MRI with abnormal signal intensity at distal quadriceps tendon

-Sagittal color coded DECT shows urate deposition (green) in periphery of lytic lesion

-Anterolateral 3D CT oblique projection shows lytic patellar lesion

Sag PD

OHSU

Dual Energy CT

Osteomyelitis in 64 y/o man with history of gout, swelling and pain in second right toe and borderline high serum uric acid level

Radiograph shows soft tissue swelling at second toe. DECT no urate crystal deposition excluding gout

T2W MR shows bone marrow edema like signal abnormality and soft tissue edema at distal second toe

Cor T2 FSOHSU

Dual Energy CT

Overall tophus burden or volume of uric acid may be calculated for individual lesions, joints or entire scanned area

DECT can quantify tophi without significant user variability making it an ideal tool for evaluating even small changes in tophus burden

Can document response to treatment for daily practice or clinical trials

Studies obtained 6 weeks apart on DECT -Difficult to quantify visually with different positioning and small amount of change

-Volumetric analysis: 8.3% volume decrease with medical treatment and serum urate drop from 10.5 to 8.3mg/dL

OHSU

Dual Energy CT

Possible future uses of DECT include:

1.) Bone marrow edema detection2.) Metal artifact reduction 3.) Tendon analysis 4.) Arthrography 5.) Metastasis detection 6.) Bone mineral density analysis

Is there an increased radiation dose with DECT?

-No the radiation dose is equivalent to standard CT-Spatial resolution should also be equal to standard CT

OHSU

Dual Energy CT

Metal Artifact ReductionAxial DECT images in patient with screw fixation of tibial plateau fracture

Artifact decreases as tube voltage increases toward 130 kV (70, 100, 130 and 190 kV)

At higher levels, noise increases limiting evaluation of soft tissues

OHSU

Dual Energy CT

Bone Marrow Edema (BME) Detection -Numerous studies have validated DECT for BME detection

-Sensitivity and specificity for BME on DECT has been reported as 96.3% and 98.2% respectively

-Reported accuracy of 97.6% when compared to MRI

Limitations: -Incapable of showing BME lesions adjacent to cortical bone

-Increased false negative rates in sclerotic vertebral bodies

-Use of color images increase sensitivity Cor T2 FS

OHSU

Dual Energy CT

Iodine Application in CT Arthrography (CTA)

-MR arthrography considered superior to CT given soft tissue detail and improved contrast resolution

-Not all patients may undergo MRA

CT arthrography considered superior for cartilage and bone lesion assessment

Value of DECT CT arthrography beyond standard CTA

-Iodine mapping to enhance minimally filled clefts and labral tears improving contrast resolution

48 y/o woman CTA for labral tear

Iodine mapping makes superior labrum tear more conspicuous (arrowheads)

OHSU

Low Dose CT

Sacroiliac Joints (SIJ)Given advances in technology, low dose CT of the SIJ can be consistently performed with less than 1 mSv effective dose

This dose places low dose SIJ CT in same minimal risk category as SIJ radiography

Tighter collimation to the SIJ is possible with CT likely resulting in lower gonadal dose than radiography

Clinical Relevance: Reliability and sensitivity of SIJ radiography for sacroiliitis is poor, low dose CT should replace radiography for SI joint evaluation

OHSU

Low Dose CT

OHSU

Low Dose CT

Extremity Trauma Missed fractures comprise up to 80% of missed diagnoses in emergency department

Ultra-low-dose CT (ULDCT) has been proposed to increase diagnostic yield

Ultra-low-dose CT: Use of modern iterative reconstruction techniques while preserving diagnostic quality

Research StudyCompared ULDCT to radiography for evaluation of extremity trauma in ED setting

OHSU

Low Dose CT

Results-CT detected additional fracture related findings 15.9% of cases and confirmed or ruled out suspected fractures in 9.2% cases

-Radiation dose was comparable between radiography and ULDCT

-Mean combined examination time plus time to preliminary report was shorter for ULDCT

-Recommended treatment changed in 16.4% of extremities

Clinical Relevance: ULDCT detects significantly more fractures than radiography and provides additional clinically important information

OHSU

Low Dose CT

28 y/o female with fall and radiographically occult Lis Franc type injury

Fleck sign on ULDCT in keeping with avulsion fracture at base of second metatarsal

OHSU

Low Dose CT

29 y/o male fall on outstretched hand with radiographically occult scaphoid waist fracture

ULDCT shows non-displaced fracture at scaphoid waist

OHSU

Limited MRI Protocols

Proximal Femoral Fractures

Significant cause of mortality and morbidity in elderly patients

Meta-analysis across 11 studies and 938 patients found pooled weighted summary of sensitivity and specificity values for limited MRI protocols in detecting radiographically occult hip fractures as follows:

-99% (95% CI, 91-100%) and 99% (95% CI, 97-100%)

Mean scanning time for limited MRI protocols: Less than 5 minutes

Two sequence protocol: Coronal T1 and STIR was 100% sensitive

OHSU

Limited MRI Protocols

Clinical RelevanceLimited MRI protocols can be used as standard of care in patients with suspected, but radiographically occult hip fracture

Cor T1

OHSU

Rapid MRI Protocols

Advanced MRI acquisition strategies including combined multislice technique and parallel imaging accelerations enable four-fold accelerated clinical 5 minute knee MRI examinations at 1.5 and 3T

Clinical RelevanceRapid MRI protocols optimize efficiency by:

-Increasing availability and accessibility -Improving tolerability for adult and pediatric patients-Reducing motion artifacts -Decreasing need for sedation and anesthesia -Augmenting throughput

OHSU

Rapid MRI Protocols

OHSU

Metal Artifact Reduction Sequence (MARS)

Advances in MRI acquisition has resulted in novel sequences to significantly decrease metal associated artifacts

Clinical RelevanceMetallic orthopedic implants are being increasingly imaged at MRI with diagnostic results due to artifact suppression techniques OHSU

Metal Artifact Reduction Sequence (MARS)

Metallosis in a 61 y/o woman with metal on metal hip arthroplasty

Polylobulated fluid collection adjacent to greater trochanter (arrows)

Halo of susceptibility artifact is significantly decreased by using WARP, allowing for better characterization of fluid collection and its communication with the greater trochanter and arthroplasty hardware

Ax T2 Ax WARP with MARSOHSU

Metal Artifact Reduction Sequence (MARS)

Infection and septic loosening in a 42 y/o woman

Loosening and malalignment radiographically, CT reformat with streak artifact

Marked signal loss artifact on Cor PD imaging without MARS, PD with MARS shows high signal intensity (arrow) at irregular bone-metal interface, also increased detail at distal ulna (arrowhead)

Cor STIR is essentially non-diagnostic due to artifact, STIR with MARS shows extensive soft tissue edema (arrowhead), small effusion (curved arrow), and thin rim of high signal at bone-metal interface (arrow)

Cor PD Cor PD MARS

Cor 3D CT Cor STIR Cor STIR MARS

OHSU

Metal Artifact Reduction Sequence (MARS)

66 y/o female with suspicion for rotator cuff tear after injury with shoulder hemiarthroplasty

Radiograph is normal

Cor STIR is non-diagnostic due to severe in-plane and through-plane artifact

Cor STIR with MARS shows tear of supraspinatus (arrow)

Cor STIR Cor STIR MARS

OHSU

Conclusion

1.) Increasing awareness of new imaging techniques will allow clinicians to treat patients in the most cost-effective, accurate and efficient manner as possible

2.) Being as specific as possible with the clinical question will allow for a more detailed imaging protocol resulting in a more diagnostic exam

3.) Do not hesitate to reach out to a radiologist with any imaging questions including what is the most appropriate exam to order

OHSU

References

Chhabra A, Andreisek G, Soldatos T, Wang KC, Flammang AJ, Belzberg AJ, Carrino JA. MR neurography: past, present, and future. AJR Am J Roentgenol. 2011 Sep;197(3):583-91. doi: 10.2214/AJR.10.6012. PMID: 21862800.

Martín Noguerol T, Barousse R, Gómez Cabrera M, SocolovskyM, Bencardino JT, Luna A. Functional MR Neurography in Evaluation of Peripheral Nerve Trauma and Postsurgical Assessment. Radiographics. 2019 Mar-Apr;39(2):427-446. doi: 10.1148/rg.2019180112. Epub 2019 Feb 8. PMID: 30735470.

ChalianM, Chhabra A. Top-10 Tips for Getting Started with Magnetic Resonance Neurography. SeminMusculoskelet Radiol. 2019 Aug;23(4):347-360. doi: 10.1055/s-0039-1677727. Epub 2019 Mar 5. PMID: 30836387.

Desai MA, Peterson JJ, Garner HW, Kransdorf MJ. Clinical utility of dual-energy CT for evaluation of tophaceous gout. Radiographics. 2011 Sep-Oct;31(5):1365-75; discussion 1376-7. doi: 10.1148/rg.315115510. PMID: 21918049.

Mallinson PI, Coupal T, Reisinger C, Chou H, Munk PL, NicolaouS, Ouellette H. Artifacts in dual-energy CT gout protocol: a review of 50 suspected cases with an artifact identification guide. AJR Am J Roentgenol. 2014 Jul;203(1):W103-9. doi: 10.2214/AJR.13.11396. PMID: 24951221.

Mallinson PI, Coupal TM, McLaughlin PD, NicolaouS, Munk PL, Ouellette HA. Dual-Energy CT for the Musculoskeletal System. Radiology. 2016 Dec;281(3):690-707. doi: 10.1148/radiol.2016151109. PMID: 27870622.

Rajiah P, Sundaram M, SubhasN. Dual-Energy CT in Musculoskeletal Imaging: What Is the Role Beyond Gout? AJR Am J Roentgenol. 2019 Sep;213(3):493-505. doi: 10.2214/AJR.19.21095. Epub2019 Apr 30. PMID: 31039024.

Chahal BS, Kwan ALC, Dhillon SS, Olubaniyi BO, Jhiangri GS, Neilson MM, Lambert RGW. Radiation Exposure to the Sacroiliac Joint From Low-Dose CT Compared With Radiography. AJR Am J Roentgenol. 2018 Nov;211(5):1058-1062. doi: 10.2214/AJR.18.19678. Epub 2018 Sep 12. PMID: 30207791.

Alagic Z, BujilaR, EnocsonA, Srivastava S, Koskinen SK. Ultra-low-dose CT for extremities in an acute setting: initial experience with 203 subjects. Skeletal Radiol. 2020 Apr;49(4):531-539. doi: 10.1007/s00256-019-03309-7. Epub 2019 Sep 9. PMID: 31501959; PMCID: PMC7021773.

Wilson MP, Nobbee D, Murad MH, DhillonS, McInnes MDF, Katlariwala P, Low G. Diagnostic Accuracy of Limited MRI Protocols for Detecting Radiographically Occult Hip Fractures: A Systematic Review and Meta-Analysis. AJR Am J Roentgenol. 2020 Sep;215(3):559-567. doi: 10.2214/AJR.19.22676. Epub2020 Jul 13. PMID: 32755182.

Fritz J, Guggenberger R, Del Grande F. Rapid Musculoskeletal MRI in 2021: Clinical Application of Advanced Accelerated Techniques. AJR Am J Roentgenol. 2021 Mar;216(3):718-733. doi: 10.2214/AJR.20.22902. Epub2021 Feb 3. PMID: 33534618.

Del Grande F, Rashidi A, Luna R, Delcogliano M, Stern SE, Dalili D, Fritz J. Five-Minute Five-Sequence Knee MRI Using Combined Simultaneous Multislice and Parallel Imaging Acceleration: Comparison with 10-Minute Parallel Imaging Knee MRI. Radiology. 2021 Jun;299(3):635-646. doi: 10.1148/radiol.2021203655. Epub2021 Apr 6. PMID: 33825510.

Talbot BS, Weinberg EP. MR Imaging with Metal-suppression Sequences for Evaluation of Total Joint Arthroplasty. Radiographics. 2016 Jan-Feb;36(1):209-25. doi: 10.1148/rg.2016150075. Epub 2015 Nov 20. PMID: 26587889.

OHSU