App for running mrtrix3 dwipreproc and then performing nonlinear registration of dwi to T1 (by running ANTs affine+nonlinear registration of CSF masks of mean b0 and T1). Bvectors are rotated with the affine transform. App is recommended for bringing dwi to T1 space if no phase encoding contrast between b=0 images was collected (so mrtrix3 dwipreproc cannot perform inhomogeneity field estimation).