Axon Diameter Mapping in the Presence of Orientation Dispersion using Diffusion MRI

Hui Zhang¹, Penny L. Hubbard², Geoff J. M. Parker², Daniel C. Alexander¹

Axon diameter mapping using diffusion MRI provides more specific biomarkers than DTI indices. Earlier works assume a model of strictly parallel axons. However, such approximation is inadequate for most white matter regions in which axons fan or bend, resulting in significant orientation dispersion. Such dispersion, if unaccounted for, leads to overestimation of axon diameters. We ameliorates this problem by proposing a model that captures orientation dispersion explicitly. We demonstrate that recovery of axon diameters is possible even in the presence of orientation dispersion, supporting accurate axon diameter mapping in a much wider set of white matter than previously possible.