I've been using fslstats to create a mask of voxels reaching a certain threshold and then using mri_volcluster to reduce the mask down to just clusters above 3 voxels. Now we're trying to filter them down to just those clusters that have more than 3 contiguous voxels in a single direction, rather than total volume. I can't find anything in the help file on this, but I was wondering if there's possibly an undocumented flag in mri_volcluster that would do this?