Dear Min,
the partial volume estimation (PVE) approach should have some advantages esp. in the basal ganglia or thalamus. These structures will reveal PVE segmentation values which are in the middle between pure gray and white matter segmentations. Typical values are around 0.5 for both gray as well as white matter. However, sometimes bias correction might fail (esp. or scanners with >=3T) and these structures will be identified as white matter. This can be checked by displaying the bias corrected T1-image, where these central structures are too bright. In this case I recommend to modify the settings for bias correction (e.g. bias regularization and/or fwhm).
Regards,
Christian
____________________________________________________________________________
Christian Gaser, Ph.D.
Departments of Psychiatry and Neurology
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 Thu, 31 Mar 2011 15:42:09 -0600, Min Liu <[log in to unmask]> wrote:
>Dear all,
>
>It comes to me that using VBM8 toolbox has an advantage over the common SPM
>routine introduced by the 'Partial Volume Estimation' function. That means
>it can better segment GM-WM mixed classes such as thalamus and other
>subcortical structures. It turns out that most part of the thalamus and
>subcortical grey matter are designated as white matter as shown in the graph
>I appended to this email. I am currently doing a VBM on white matter between
>a cohort of patients and normal subjects. Significantly reduced WM volume
>was shown in red and overlapped on a representative WM segmentation map. I
>am wondering how much I can trust the result. The detected change in yellow
>box consist of thalamus, putaman, pallidum and caudate, those regions that
>shouldn't be classified as white matter. The detected change in green box
>seems nail some true white matter. Can I say change in green box reliable
>and change in yellow box not? Thank you for your comments in advance!
>
>Min
>
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