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Hi Matt, On Fri, Mar 27, 2009 at 10:54 PM, Matt Glasser <[log in to unmask]> wrote: > I always track from white matter. If it is a cortical ROI I use the 1st > voxel of the white matter surface. That's an interesting approach. How do you get from cortical ROI to the 1st voxel of the WM? > Honestly, I have found that tracking > from/into cortical grey matter results in more error than useful > information > (its easy to get pathways crossing sulci for example, if you combine > partial > voluming with the fact that the principle diffusion direction in cortical > grey matter is oriented perpendicular to the cortical surface, and cortical > grey matter ROIs may be very close to brain rim voxels). Could this simply be because of the nonlinear distortions between DTI and FreeSurfer input image? It could be several voxels in most of the brain. Thanks, Martin