A Recursive Filter for Phase Velocity Assisted Shape-based Tracking of Cardiac Non-rigid Motion*

A framework for tracking pointwise periodic non-rigid motion of the heart's left ventricular (LV) wall is presented which incoporates information from two different magnetic resonance imaging (MRI) techniques. New developments in phase-contrast cine MR imaging have produced spatial maps of instantaneous velocity that have proven accuracy within the myocardium, or wall, of the heart. This infor-mation is combined with shape-based matching techniques to provide improved estimates of trajectories, especially in regions where shape information is limited. These raw tra-jectories act as input to a recursive least squares {RLS) filter which applies the constraints of temporal periodicity and spatial smoothness for the final estimate. The results of the RLS filter are compared with the motion of actual im-planted markers. Comparisons are also made between ex-clusively shape-based filtered and phase-contrast enhanced trajectory estimates using both phantom and actual canine heart llJR images.