Toward an accurate MR measure of the axon radii by accounting for myelin-specific attenuation of the diffusion MRI signal in the brain

An accurate, noninvasive measure of axonal radii could play a crucial role in the understanding of healthy and diseased neural processes. Several diffusion-weighted MRI (dMRI) methods report on the axon radii distribution or mean axon radii. However, these measurements systematically overestimate histologically derived values. In this preliminary study, we address this limitation by formulating a model which explicitly includes the myelin contribution to the cerebral dMR signal. In detail, we introduce a myelinic compartment in both the AxCaliber and ActiveAx models and demonstrate a significant improvement of axonal radius estimation using synthetic data simulation.