Which Reorientation Framework for the Atlas-Based Comparison of Motion from Cardiac Image Sequences?
Abstract
The present paper builds upon recent advances in the spatiotemporal alignment of cardiac sequences to construct a statistical atlas of normal motion. Comparing cardiac sequences requires considering both the temporal component (changes along the sequences) and the inter-subject one. The objective here is to understand the changes in the comparison of myocardial velocities depending on (1) the chosen reorientation action (finite strain [local rotation only], local rotation and isotropic scaling, or full Jacobian matrix using the push-forward) and (2) the chosen system of coordinates (Lagrangian, Eulerian, or if a compromise between both [e.g. hybrid-Eulerian] is possible). Myocardial velocities are estimated locally using speckle tracking on echocardiographic (US) sequences, then aligned to a reference timescale, and finally reoriented to the anatomical reference according to the chosen reorientation framework. The methodology was applied to 2D US sequences in a 4-chamber view from 71 healthy volunteers. Experiments highlight the limitations of the hybrid-Eulerian scheme, showing that the intra-subject transformation should be taken into account, and discuss the options to perform the inter-subject one.