they are in correspondence, but there may be shear in the pial deformation, so the link will overestimate the thickness. Easy to compute though, just the distance between the same vertex on the 2 surfaces On Wed, 22 Jun 2005, Fornito, Alexander wrote:
Is there some kind of correspondance between them that is specified in any of the files? I'm thinking of trying to use something like the link method (desrcibed in the Lerch & Evans, 2005 paper) for estimating thickness, but as I understand it, there needs to be some kind of established link between the points on each surface.
-----Original Message----- From: Bruce Fischl [mailto:fischl@nmr.mgh.harvard.edu] Sent: Wed 6/22/2005 9:20 PM To: Fornito, Alexander Cc: freesurfer@nmr.mgh.harvard.edu Subject: Re: [Freesurfer] vertex correspondance
Hi Alex,
yes, all the surfaces of a hemisphere (except qsphere) have the same # of vertices/edges and faces. I think Doug has something that will sample the mask. mri_vol2label or something like that?
Bruce
On Wed, 22 Jun 2005, Fornito, Alexander wrote:
Hi again,
So many questions!!
Is there some sort of correspondence between vertices on the inner (wm) and outer (pial) surfaces? Ie., for every vertex on the inner surface, is there a point on the outer surface, and if so, does Freesurfer retain this information in any of the files?
Also, I have some binary masks that I have manually traced using another program that I would like to apply to the surfaces to get regional measures of thickness. The mask images are in analyze format. Is there any way that I can do this?
Thanks as always,
Alex
Alexander Fornito
M.psych (Clin. Neuro.)/PhD candidate
Melbourne Neuropsychiatry Centre and Department of Psychology
The University of Melbourne
alexander.fornito@wh.org.au