Figure 1:

Local 3D anisotropic Gaussian filter-based denoising of cortical dMRI data using the cortical reference frame estimated from the structural MTR volume. From a structural magnetization transfer ratio (MTR) volume, we generated a white matter mask using FSL-FAST. Next, using LayNii, we computed the cortical depth of each voxel (i.e., distance from GM/WM boundary) and derived the direction perpendicular to the orientation of the cortical surface. This radial orientation of the cortical reference frame (CRF) implicitly defines the corresponding orthogonal plane locally tangent to the cortical surface, which determines the orientation of the local anisotropic Gaussian filter used to process the motion- and distortion-corrected MAP-DWIs.