Fig. 4.

Box plots displaying the 25^th, median and 75^th (box) as well as ±95^th percentiles (whiskers) of the NAA, Cr, Cho and mI absolute concentrations distributions for single voxels, intra-voxel, shaded; and the summed spectra: single time points across all subjects (inter-subject, right-hatched) and all time points of the same subject (intra-subject, cross-hatched). Note the dramatic, ×4 to ×5 fold, improvement in both cross-sectional and longitudinal repeatability of the sums compared with the single voxels. Insert: Box plots of the GM, WM and tissue fractions (GM_f, WM_f and T_f) distributions in the VOIs of all subjects. Note the narrow distribution of tissue types, indicating the minimal GM/WM/CSF partial volume repositioning error of the proposed approach.