Microsoft Word - MIC2004_Proceedings_1015.DOC

The cardiac model of the 4D NCAT phantom was enhanced by incorporating a physiological basis from which to realistically model left ventricular (LV) motion defects. A finite element mechanical model of the LV was developed to simulate deficits in contractile function and to study the effect of ischemia on LV function. The model geometry was based on high resolution CT and MRI data sets of a healthy male subject. The myocardial wall was represented as a transversely isotropic material with the fiber angle varying from -90 degrees at the epicardial surface, through 0 degrees at the mid-wall, to 90 degrees at the endocardial surface. An elastance active contraction model was used to provide fiber contraction. Physiological intraventricular systolic pressure-time curves were used to load the ventricle. These features were incorporated into the 4D NCAT cardiac model through the control points, which are set to move according to the principles that govern the mechanical model. A normal model and two pathologic models were created in order to study the effects of ischemia on cardiac function. In the first pathologic model, a sub-endocardial anterior ischemic region was defined and an NCAT image data set was subsequently produced. A second ischemic model was created with a transmural ischemic region defined in the same location as the subendocardial ischemia model. These models were able to demonstrate differences in contractile function between subendocardial and transmural infarcts and how these differences in function are documented in the SPECT images that were produced by the NCAT phantom. As demonstrated in this study the 4D NCAT cardiac model provides a valuable tool for the evaluation of imaging methods that assess cardiac function through measurements of myocardial deformation.