Effect of Slice-wise Bmatrix Rotation due to Intra-Volume Motion on dMRI-derived Directional Information

Motivation: Intra-volume motion correction of dMRI, results in spatially-varying "effective" diffusion gradients within a volume. The effects of these slice-wise-rotated Bmatrices is generally disregarded in dMRI analyses. Goal(s): To determine whether considering slicewise-rotated Bmatrices improves fiber tractography results. Approach: Simulated data was used to perform tractography with slicewise-rotated and traditional Bmatrices and compared to the ground-truth. An in-vivo dataset with longitudinal scans was used to assess longitudinal reproducibility. Results: For most fiber bundles, the effect of slicewise Bmatrices was negligible, however, for several long range connections, the differences in reconstructed tracts were present and quantifiable with slicewise Bmatrices resulting in anatomically more faithful representations. Impact: This study determined that tractography studies performed on a population susceptible to large motion would benefit from using slicewise-rotated Bmatrices for a more accurate analysis.