Evidence for Mesoscale Gaussian Water Diffusion in Living Human Brain

Motivation: Diffusion MRI is a promising means to map mesoscopic human brain architecture in vivo, however an appropriate model is required that relates the MR signal and features of the underlying microstructure within the voxel. Goal(s): The goal of this study is to determine whether a Gaussian diffusion model is applicable at the mesoscale. Approach: We compared single and double diffusion encoded signals acquired with large b-values at two different diffusion times to test for Gaussianity. Results: We found no significant time-dependence in the diffusion weighted signals in brain parenchyma, confirming the applicability of the Gaussian diffusion at the mesoscale. Impact: The study resolves the ongoing debate on the appropriate model to use to analyze the diffusion weighted signals in live human brain at clinically accessible spatiotemporal scales.