Odf-based Morphometry and Application to Brain Asymmetry

Introduction: The Orientation Distribution Function (ODF), the angular profile of the diffusion probability density function of water molecules, can be estimated from High Angular Resolution Diffusion Imaging (HARDI) data [2]. We present an extension of voxel-based morphometry to ODFs and apply it to brain asymmetry. While little is known about white matter connectivity asymmetry, several recent studies have examined left-right differences from DTI-derived measures in large human populations (N = 374; [1]). ODF-based morphometry allows us to extend the study of hemispheric asymmetry by examining differences in fiber characteristics across hemispheres rather than just differences in shapes and volumes. We estimate voxel-wise maps of asymmetries between the ODFs in the left and right hemispheres, using a generalized Hotelling’s T-squared test for ODFs. Voxel Based Morphometry (VBM) is a neuroimaging analysis technique to investigate regional differences in brain anatomy. VBM-type methods have made a significant contribution to the understanding of brain changes in several disorders and their relation to clinical measures. For example, VBM has been used to study a