METHODS FOR ANALYSIS OF TAGGED MR CARDIAC IMAGES

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DESCRIPTION (Adapted from Applicant's Abstract): The aim of this proposal is to further develop and validate algorithms for analysis of SPAMM MR cardiac images based on novel spline methods. MRI is unique in its ability to non-invasively and selectively alter tissue magnetization, and create tagged patterns within the deforming tissue such as the heart muscle. The resulting pattern defines a time-varying curvilinear coordinate system on the underlying tissue, allowing for precise and quantitative measurement of tissue motion and deformation. The investigators are developing two frameworks for analysis of SPAMM tagged images, both of these aimed at providing a more automated and reproducible approach to analysis of SPAMM data, as well as providing dense 3-D displacement information at all points within the LV myocardium. The investigators propose to (a) further develop and extend our analyses techniques. The extensions considered will all be related and based on currently developed computer vision-based techniques for regional LV wall motion analysis, that operates either on a sequence of SA slice stacks or on a time sequence of single slice. (b) The investigators will validate the motion tracking methods by comparing "true" and algorithm-estimated motion trajectories: 1) on dense field of points derived from 3-D tagged computer models of objects that simulate the moving LV, 2) on dense field of points derived from Finite Element Model simulations of the constitutive equations of LV deformations (once again tag planes will be superimposed on the time course of simulated geometries), 3) on selected points in the LV myocardium of the in vivo heart using a porcine model. Here, "true" motion will be determined by tracking implanted image distinguishable markers. (c) The investigators will test whether regions of postmortem myocardial injury imply similar-sized and locate regions of altered deformations (as measured by parameters developed in (a)). The algorithm-derived LV function assessment based on the analysis of in vivo tagged MRI sequences will be compared with postmortem myocardial injury assessment determined by myocardial staining techniques. The validated parameters will also be use to examine the time-course of change in the ischemic areas of the chronic animal models.