Hi Keith
the average white/pial surface doesn't have any topological or smoothness
constraints, which is why we don't really use it. Yes, mris_expand is slow,
but that's precisely because it prohibits self-intersection. The good nes
is that compared to the rest of the recon stream it doesn't add that much
time :)
Bruce
On Sat, 6 Apr 2013, Keith Jamison wrote:
I have seen that the official recommendation for making a mid-gray surface
is to use mris_expand. This seems to be a very slow procedure on my
machine. I have also tried just loading the ?h.white and ?h.pial surfaces
into matlab, averaging their vertices, and exporting the result. This seems
to result in a nearly identical surface as mris_expand. On a test subject,
only 48 out of 127,998 (0.0375%) vertices differed by more than 0.1mm, and
these were almost entirely around the edges of the corpus callosum.
Is there a reason this alternative is a bad idea? I imagine mris_expand
does additional topology checks along the way, but if the vertices vary so
little, can that be a major problem?
I'm inclined to go with the faster solution, but since I'm relatively new to
this procedure, I wanted to see what the community's experience might be.
Thanks!
Keith
_______________________________
Keith Jamison
Graduate Research Assistant
Department of Biomedical Engineering
University of Minnesota
7-105 NHH, 312 Church St. SE
Minneapolis, MN 55455
Office: 6-112 Nils Hasselmo Hall
Mobile: 607-227-0696
kjami...@umn.edu
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