Dear Franz,
my first guess is that the GM/WM images are normalized, but the T1 image is not. You have to use the normalized T1 image to correctly compare it with its segmented counterparts.
Regards,
Christian
____________________________________________________________________________
Christian Gaser, Ph.D.
Assistant Professor of Computational Neuroscience
Department of Psychiatry
Friedrich-Schiller-University of Jena
Jahnstrasse 3, D-07743 Jena, Germany
Tel: ++49-3641-934752 Fax: ++49-3641-934755
e-mail: [log in to unmask]
http://dbm.neuro.uni-jena.de
On Tue, 16 Nov 2010 14:44:25 +0100, Franz Riederer <[log in to unmask]> wrote:
>Dear all,
>
>I see there is a lot of effort to support people working with structural MRI
>analyses, and I am grateful for that. Although I got some inspiration from
>the archives of the mailing list, I could not find an answer for the
>following problem:
>In some rare instances grey matter seems classified as white matter (please
>see attachment, blue arrow). In these instances, the dura over the cortex
>appears rather bright (lower image). Changing the bias regularisation to
>"extremely light" instead of the default "very light" seemed to have a minor
>positive effect.
>
>To my surprise, the Unified Segmentation within SPM8 seemed to be less
>sensitive to this artifact.
>
>I also see that this might be a problem of the sequence we used in this
>subject.
>
>I wonder whether there is a way to optimize post processing.
>
>Many thanks in advance,
>
>
>Franz
>
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