Array of spatial sensitivity encoding techniques

T1- and diffusion-weighted images (DWIs) were acquired on a 3.0-Tesla MR scanner (GE Healthcare, Milwaukee, WI, USA) with an eight-channel head coil. The parameters of the 3D T1-weighted fast spoiled gradient-echo sequence were: repetition time of 6.3 ms, echo time of 2.1 ms, flip angle of 12°, slice thickness of 1 mm, field of view of 256 × 256 mm², matrix of 256 × 256, and isotropic voxel size of 1 × 1 × 1 mm³.
An echo-planar imaging (EPI) sequence was utilized for DWIs (repetition time = 17,000 ms, echo time = 108 ms, field of view = 240 mm, matrix size = 144 × 144, slice thickness = 1.7 mm, and voxel size = 1.67 × 1.67 × 1.7 mm³). Eddy current effects were minimized by applying the double-echo option. An eight-channel head coil and an array of spatial sensitivity encoding techniques (GE Healthcare) with two sensitivity encoding speed-up factor were used to reduce the impact of EPI spatial distortions. Seventy axial slices parallel to the anterior–posterior commissure line covering the entire brain in 51 directions with a b-value of 900 s/mm² and eight baseline scans with a b-value of 0 s/mm² were acquired. The DTIs were approximated from DWIs using the least-squares method (approximate scan time: 17 min).

MRI data acquisition was performed at CHA Bundang Medical Center using a 3.0-Tesla GE Signa HDxt scanner (GE Healthcare, Milwaukee, WI, USA). Diffusion-weighted images (DWI) were acquired using an echo planar imaging (EPI) sequence with the following parameters: repetition time, 17,000 ms; echo time, 108 ms; field of view, 240 mm; matrix, 144 × 144; slice thickness, 1.7 mm; and voxel size, 1.67 × 1.67 × 1.7 mm³. A double-echo option was applied to reduce eddy-current-related distortions. To reduce the impact of EPI spatial distortions, an 8-channel coil and ASSET (Array of Spatial Sensitivity Encoding Techniques; GE Healthcare) with a SENSE factor of two was used. Seventy axial slices parallel to the anterior commissure–posterior commissure line were acquired in 51 directions with b = 900 s/mm². Eight baseline scans with b = 0 s/mm² were also acquired. DTIs were extracted from the DWIs using the least-squares method.