Highly diffusion-sensitized MRI of brain: Dissociation of gray and white matter

The brains of six healthy volunteers were scanned with a full tenser diffus ion MRI technique to study the effect of a high b value on diffusion-weight ed images (DWls). The b values ranged from 500 to 5000 s/mm(2). Isotropic D Wls, trace apparent diffusion coefficient (ADC) maps, and fractional anisot ropy (FA) maps were created for each b value. As the b value increased, ADC decreased in both the gray and white matter. Furthermore, ADC of the white matter became lower than that of the gray matter, and, as a result, the wh ite matter became brighter than the gray matter in the isotropic DWls. Quan titative analysis showed that these changes were due to nonmonoexponential diffusion signal decay of the brain tissue, which was more prominent in whi te matter than in gray matter. There was no significant change in relation to the b value in the FA maps. High b value appears to have a dissociating effect on gray and white matter in DWls, (C) 2001 Wiley-Liss, Inc.