Sorry for the delayed response. Thank you for the example. The issue is at the very least known to us now. Fortunately this doesn't happen on all images. I will look into ways to restrict the region growing algorithm from cutting away voxels that may be periventricular hyperintensities. If you leave some CSF in the assessed region of interest it ptrobaby wont cause much of a problem because CSF will very likely not be detected as hyperintense white matter.