Longitudinal Alignment of Brain Cortical Anatomy using Strain-Constrained MSM

摘要: Methods:We retain the spherical registration framework as this results in a simplified and consistent set of discrete displacements for all control points, and instead implement two fundamental changes to the original MSM method: 1) anatomical warps are estimated from spherical warps using a barycentric resampling procedure (figure 1); 2) displacements of the anatomical mesh are regularized using a biological strain based penalty, similar to that proposed in [4]. Biological strain calculations require at least 3 points. This requires modification of framework from use of pairwise smoothness penalty terms, to triplet terms. To allow this to be solved using conventional discrete solvers this requires the triplet terms to be reduced to pairwise terms using the methods proposed in [5][6][7].Results:The approach is applied to longitudinal registration of neonatal cortical surfaces acquired for the developing Human Connectome Project. White matter cortical surfaces are extracted [8] following tissue segmentation [9], and are projected to spheres using FreeSurfer protocols [10]. Registration is performed longitudinally between 22 subjects at 38 weeks PMA and 27 subjects at 42 weeks PMA, for all pairs of subjects within one week of each time point, where registration is driven to match cortical folding patterns.