A Local Force Model for Cardiac Dynamics Analysis Based on CTVolumetric Image Sequences

We present in this paper a local force model and its integration to a hierarchical analysis in the estimation of the left ventricle motion over a cardiac cycle. The local force model is derived from the dynamics of independent point masses driven by local constant forces over a short time period. A force eld is assumed to remain constant over short periods of time driving independent point masses within a regional patch of the left ventricle surface from one time instant to another. The trajectory that minimizes the energy required to move the point mass from one surface to another is considered as the local displacement vector. This estimated trajectory takes into account surface constraints and previous estimations derived from the volumetric image sequences so that the point masses travel along smooth trajectories resembling the realistic left ventricle surface dynamics. This proposed model is able to recover the point correspondences of the nonrigid motions between consecutive frames when the surfaces and the initial conditions of left ventricle at consecutive time frames are given. The local force model is incorporated to a hierarchical analysis scheme 1 providing us a complete global and local dynamics of the left ventricle compared to only local kinematics analysis of previous approaches. Experimental results based on synthetic and real left ventricle CT volumetric images show that the proposed scheme is very promising for cardiac analysis.