Fig. 4.

DTI results. A) Visualization of diffusion encoding directions on a sphere for DTI protocols at each site. Note that UCLA and Stanford used two different DTI protocols for MAPP Network neuroimaging. B) Voxel-wise differences in fractional anisotropy (FA) throughout the brain relative to NU (Siemens 3 T Trio, 60 directions + 8 b = 0 s/mm²) in healthy volunteers. C) Mean FA measurements in the genu of the corpus callosum demonstrating significant differences across sites. D) Regions of interest (ROIs) for major fiber tracts were selected for between-site comparison of FA in the cohort of normal healthy females age 20–35: the left geniculate fiber system (blue) left splenium of the corpus callosum (red) and left cingulum bundle (green). E) Comparison of mean FA measurements from the ROIs illustrated in (D) stratified by site. Results show significant site differences in the corpus callosum (red ROI, H = 13.17, P = 0.0043), cingulum bundle (green ROI, H = 17.30, P = 0.0006), and geniculate fibers (blue, ROI) H = 13.00, P = 0.0046). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)