Objective: •  Create a dynamic cardiac model, with patient

variability, for use in medical imaging simulations.

Motivation: •  Allow for in-silico cardiac CT simulations

leading to improved protocols.

•  Quantify measurement uncertainty in coronary computed tomography angiography (cCTA) leading to more robust assessment of coronary stenosis.

Methods:

Model Cardiac Biomechanics

Patient LV Volume Curves •  12 patients - Philips Epiq 7 Ultrasound •  LV endocardial border tracked in AP2 and AP4 views •  Semi-automated method incorporating speckle tracking. •  Simpson’s method provided LV volume.

FE Model - Fit to Patient Data •  Frames (time points) from the FE model were interpolated

to match the LV volume curves from patient echocardiography.

Track Coronary Arteries •  Coronary motion and velocity determined by tracking

points on the FE model.

Simulated CT (Preliminary)

Conclusions: •  Virtual cardiac phantom will provide a platform to

systematically investigate motion blur in cCTA and quantify measurement uncertainty.

Discussion: •  Augmented state-of-the-art biomechanical cardiac model with

dynamic LV filling curves from patient echocardiography. •  Obtained cardiac motion profiles with variable diastology. •  Coronary velocities compare well with other published

values.4

•  Systole and early diastolic filling are rapid, short duration events. As such, the average velocity in 75 ms acquisition is higher during these events than with a slower 150 ms acquisition, with similar velocities during diastasis. •  Effect of acquisition speed on image quality is one example

of the type of study that could be facilitated by our improved virtual cardiac phantom.

Results:

Coronary Artery Velocities •  Range of maximal velocities observed within two different

acquisition windows. Velocities were averaged within the sliding acquisition window and plotted against cardiac phase.

greg.sturgeon@duke.edu

ImprovedVirtualCardiacPhantomwithVariableDiastolicFillingRates

&CoronaryArteryVeloci?es

Gregory M. Sturgeon, TaylorW.Richards,E.Samei, and W.P. SegarsCarl E. Ravin Advanced Imaging Laboratories, Duke University Medical Center

Model Dynamic Variability

Finite Element (FE) Model Living Heart Project

Includes: •  Electrophysiology •  Ca+ ion channels •  Muscle properties

-  Time-varying elastance -  Fiber geometry

Validated against published data.1

Provides global strain information at high frame rate (not available from imaging data).

Dynamic variability and diastolic relaxation currently modeled to lesser extent, but augmented here with patient data from echocardiography.

See Also:

•  http://tiny.cc/XCAT_Heart •  “Quantification of the uncertainty in

coronary CTA plaque measurements using dynamic cardiac phantom and 3D-printed plaque models ” Poster 10132-197

References:

1 B. Baillargeon, N. Rebelo, D.D. Fox, R.L. Taylor, E. Kuhl, "The living heart project: a robust and integrative simulator for human heart function," European Journal of Mechanics-A/Solids 48, 38-47 (2014).

2 L. Husmann, S. Leschka, L. Desbiolles, T. Schepis, O. Gaemperli, B. Seifert, P. Cattin, T. Frauenfelder, T.G. Flohr, B. Marincek, P.A. Kaufmann, H. Alkadhi, "Coronary Artery Motion and Cardiac Phases: Dependency on Heart Rate—Implications for CT Image Reconstruction," Radiology 245, 567-576 (2007).

3 W. Segars, G. Sturgeon, S. Mendonca, J. Grimes, B.M. Tsui, "4D XCAT phantom for multimodality imaging research," Medical physics 37, 4902-4915 (2010).

4 M. Vembar, M. Garcia, D. Heuscher, R. Haberl, D. Matthews, G. Böhme, N. Greenberg, "A dynamic approach to identifying desired physiological phases for cardiac imaging using multislice spiral CT," Medical physics 30, 1683-1693 (2003).

Table 1: Diastatic Coronary Artery Velocity max mean minAcquisition Window

75 ms 36.5mm/s 21.4mm/s 2.0mm/s150 ms 39.1mm/s 24.3mm/s 5.6mm/s

Myocardium

Sample Projections

Blood

Coronaries

•  Cardiac geometry varied at each projection.

•  Linear interpolation of the node locations from the FE model.

•  Idealized mesh projections: •  Parallel beams •  500 projections over 180° •  75 ms acquisition •  Mono-energetic

150ms 75ms

Simulated cCTA MPR

•  Virtual cardiac phantom •  Normal motion profile, heart

rate of 60 bpm, acquired during mid-diastole.

•  Idealized projections: noise-free, no system blur, parallel beams.

•  Displayed as curved multi-planar reformation (MPR).

RCALAD

CX

Patient LV Volume Curves from Echocardiography