Diffusion characteristic analysis in human visual cortex

Since the birth of diffusion tensor imaging (DTI), diffusion characteristic has become a powerful tool to probe the internal structure of the subject. The diffusion anisotropy indices (DAIs) are parameters derived from DTI data which describe the morphological characteristics of diffusion tensor within specific range. It is of great importance to select a proper DAI for the analysis and interpretation of DTI data. In this work, the diffusion characteristic in human visual cortex is analysed with three DAIs: the commonly used fractional anisotropy (FA), ellipsoidal geometric ratio (EAR) proposed lately and ellipsoidal geometric ratio (EGR) that we proposed. The retinotopic mapping and surface-based analysis methods were applied to increase the power and precision studying longitudinal DAI changes in different visual fields (V1, V2, V3 et al). All three DAIs show the similar trend in visual fields, however, EGR and EAR both have higher magnitude and better contrast than FA. In addition, since EGR makes full use of the ellipsoidal volume information, its application result shows a certain improvement compared with EAR.