Dear Paul:
There hasn't been an upgrade that I know of at least not since spm99
came out. We also use spm99 for this purpose and find it does
reasonably well especially considering it is non-interactive (oh the
joy of hand-editing scalp). You might try correcting for intensity
inhomogeneities as this can improve tissue distinctions. Also the
problem might lie in your T1 acquisition (or whatever sequence you're
using for the anatomical scan). In our case, our physicist had to
tune our axial t1 sequence to correct the RF profile particularly
over the vertex, but if you're acquiring the sequence in a different
plane there may be other inhomogeneities. I know that in other groups
work on the RF profile has resulted in demonstrated improvement in
gray-white and gray-CSF junctions.
As an aside I'll bet it's not just from the subjects lying on their
back. I wonder if anyone has scanned people lying prone to see if
that's the case.
HTH,
Darren
>Darren,
>
>Your message reminded me of a rendering question tha I have. When I
>extract my brains I get poor resolution in the occipital area as the
>dura is just not stripped well. I assumed this was due to minimal
>CSF space when subjects are lying down. However, at HBM 2000, i saw
>many posters that used SPM to extract brains and they did not have
>this problem. Has there been an up-grade in the extraction algorithm
>that I may have missed. Your comments would be helpful.
>
>Paul
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Darren R. Gitelman, M.D.
Cognitive Neurology and Alzheimer's Disease Center
E-mail: [log in to unmask] WWW:
http://www.brain.northwestern.edu
Voice: (312) 908-9023 Fax: (312) 908-8789
Northwestern Univ., 320 E. Superior St., Searle 11-470, Chicago, IL 60611
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