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Introduction dMRI tractography needs to be constrained by a white matter (WM) mask defining the 3D space within which fibers are tracked. Most techniques usually threshold the fractional anisotropy (FA) maps (typical threshold between 0.1-0.2) assuming that when FA is too small, the uncertainty of the principal diffusion direction is high. However, this criterion is rough as the FA value is not specific of a particular structural configuration and therefore constrains tracking results to region of WM with high anisotropy. In particular, FA (or GFA) can be very low in fiber crossings representing more than 2/3 of WM voxels, thus putatively discarding many valid tracts. Furthermore, because the dMRI resolution is generally coarser than standard T1-weighted MRI (on the order of 2mm isotropic), voxels at the interface between the WM and the cortex may suffer from severe partial volume effects, artificially diminishing the FA values. Therefore, many true-positive neuronal pathways may not be revealed. In this work, we propose the creation of a robust propagation mask stemming from T1 anatomy. A preliminary step consists of adequately correcting the geometrical distortions of dMRI data, and of accurately matching it to the T1-weighted data. Many post-processing pipelines already provide brain, WM or gray matter (GM) masks from T1 data relying on a robust analysis of its histogram. However, they may suffer from several limitations. First, the partial volume effect will fail at delineating some small structures like the fornix, the posterior (PC) and anterior commissures (AC). In addition, deep brain structures, commonly crossed by efferent and afferent fibers …