Material and Methods
MRI scans were performed on 32 healthy volunteers at a 3.0T Phililps Achieva INTERA scanner with a 32-channel head coil. Written informed consent was obtained from all participants in accordance with ethical approval from the Dartmouth College Internal Review Board.
High spatial resolution dMRI sequence was acquired with a single-shot spin- echo echo-planer imaging sequence at an isotropic voxel size of 1.6 mm with four repetitions (TE/TR = 79/3382 ms, FOV = 230 mm x 230 mm x 35.2 mm, in-plane matrix size = 114 x 114, and 22 slices). Diffusion-weighted (DW) images were acquired with one volume at b-value = 0 s/mm2 (b0) and 61 noncollinear DW directions at b-value = 1000 s/mm2 with a total acquisition time of 45 min. Other imaging protocols included: A matched field-of-view (FOV) gradient-echo sequence with 2-echo times (TE = 7 and 8 ms) to generate fieldmap to correct for dMRI geometric distortion; and a whole brain T1W image using a magnetization-prepared rapid acquisition gradient echo sequence (MP-RAGE) with TE/TR = 3.72/8.18 ms, FOV = 224 mm x 224 mm x 220 mm, and isotropic voxel size of 1 mm3.