Use of a 4D planispheric transformation for the tracking and the analysis of LV motion with tagged MR images

A major issue in cardiac imaging is the assessment of cardiac function and particularly the identification of ischemic or infarcted tissues. We present in this article a method to reconstruct the motion of the left ventricule (LV) using 4D planispheric transformations of time and space combined in a first step with B-spline tensor products. Because of the 4D modeling, a) the use of planispheric coordinates makes the numerical evaluation more stable as compared to prolate spheroidal coordinates, the equivalent focal point being much further from the apical area of the heart, c) In the temporal modeling, a simple adaptation is possible to changing temporal dynamics, such as introduced by ectopic pacing or rapid filling after systole. d) Finally, the strain analysis and displacement parameters that are used for the spatial modeling are computed at any point of the LV volume. Experiments are conducted on a normal and a pathological LV (posterior infarct) in order to assess the tuning of the parameters of the method. The mean RMS-distance error is less than 0.5mm for both LVs. finally, the motion is analyzed as smooth zeroth (displacement) and first order parameters (strain).