Corpus callosum shape deformation analysis for multiple sclerosis

Neurological diseases can cause atrophy of the corpus callosum resulting in a change in its size and shape. The measurement and analysis of this change is one of the goals of clinical research. We perform statistical analysis of the shape of the corpus callosum extracted from MR brain scans of a group of multiple sclerosis patients undergoing a longitudinal (serial) study. In contrast to the classical boundary-based, global shape variability measures, e.g. kernel principal component analysis (KPCA) of corpus callosum boundary vertices, we perform a deformation-specific KPCA for analyzing the global and regional shape of the corpus callosum. This deformation specific KPCA is based on a medial-based shape representation. The adopted shape representation describes shape variability in terms of intuitive deformations. We present qualitative and quantitative results for MR images of the corpus callosum. We show that our method is successful in identifying and quantifying the effect of each type of deformation on the shape variability of the corpus callosum. In addition to analyzing the spatial shape variability in the corpus callosum, we explore shape changes as the disease progresses. Our method allows the exploration of the shape variability quantitatively as well as in a qualitative visual manner (e.g. by visualizing, say, the 2nd principal mode of shape variation due to bending at the 4th sub-region of the corpus callosum) which is useful for developing an intuitive understanding of the effects of MS on the corpus callosum shape.