Figure 4.

HARDI acquisition scheme and detected crossing fibers. (a) The graph visualizes 63 unique MR field gradient directions uniformly sampled over two spherical shells of the q-space. Caruyer et al.⁵⁷ sampler was used to design the HARDI acquisition scheme. (b) Voxels with significant 2^nd fiber orientations (i.e. crossing fibers) were detected for all dMRI protocols. No significant difference in voxel numbers was found between groups. (c) As shown for results of HARDI-ZOOMit Interp protocol in native diffusion space, detected crossing fibers are mostly located near the dorsal horns and in the anterior white commissure. Visualizations are shown for three representative participants with four selected C3–C6 axial slices. Orientations are the same over all presented slices with A anterior, P posterior, Lleft, R right directions. The orientation of detected fiber bundles are visualized as RGB (red–green–blue) color-coded lines (i.e. red—right–left direction, green—anterior–posterior direction, blue—superior–inferior direction). The blue dot in the middle of each SC voxel demonstrates an axial projection of the intra-voxel primary fiber bundle with a major superior–inferior direction. In voxels where projections of two lines are present, crossing fibers were detected.