afni.nimh.nih.gov

Hi Dan,

There is no standard, and it certainly depends on
the voxel size. If not enough is removed, masks
can include voxels with partial gray matter. If too
much is removed, it can wipe out most of a mask.

The current method uses an NN2 neighborhood,
meaning neighbors can share a face or an edge,
the 19 non-corner voxel in a 3x3x3 grid. Eroding
at that rate goes quickly.

- rick