Measurement of non-rigid motion using contour shape descriptors

The problem of measuring the motion of deformable objects from image sequences is addressed. The approach is based upon modeling the overall boundary of the object as a deformable contour and then tracking local segments of the contour through the temporal sequence. Motion computation involves first matching the local segments between pairs of contours by minimizing the deformation between the segments using a measure of bending energy. Results from the match process are incorporated into an optimization functional, along with a general smoothness term, whose local minimum results in a smooth flow field that is consistent with the match data. The computation is performed for all pairs of frames in the temporal sequence, resulting in a composite flow field over the entire sequence. The technique is applied to synthetic contour sequences and the problem of tracking left ventricular (LV) endocardial motion from medical image sequences