Hi Herve,
> Using the unified segmentation in SPM5 (with the more recent updates
> installed), we noticed that for a large proportion of subjects (30%), voxels
> belonging to the skull were misclassified into the CSF class (see example
> below).
I believe that the CSF segmentation has never been the focus of much
attention ;) leading to the fact that the differentiation between
external CSF spaces and skull tissue may not be otpimal.
> Has anyone else noticed that and are there any ways to improve this result?
I think what you could to is to focus on the ventricles by masking the
CSF segmentation with a "center of brain mask", for example by eroding
the default brain mask a couple of times. Alternatively, you could use a
more aggressive cleaning/skull stripping routine, perhaps even before
segmentation, which has been suggested to improve segmentation accuracy
in the first place (a recent NeuroImage paper). Another thing perhaps
worth looking into is the prior-less segmentation as implemented in
Christian's toolbox, which may (or may not) improve results, again
combined with a more aggressive cleaning approach. Other than that, no
ideas.
Best,
Marko
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Marko Wilke (Dr.med./M.D.)
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Universitäts-Kinderklinik University Children's Hospital
Abt. III (Neuropädiatrie) Dept. III (Pediatric neurology)
Hoppe-Seyler-Str. 1, D - 72076 Tübingen
Tel.: (+49) 07071 29-83416 Fax: (+49) 07071 29-5473
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