Dear Anna,
I am not an expert of Tc99m HMPAO SPECT. However I do not think
that white matter activation can pass any critical review process.
First I would check the anatomical neighborhood of any grey matter
areas also in adjacent slides. Second I would check the amount of
blurriness in your data (possibly due to additional smoothing). Thirdly I
would check for adjacent vascularity leading to or draining a grey matter
area. Fourth I would check for problems with global scaling of your
different scans.
The problem with your observation is also the lack of physiological basis
such an activation could be linked to.
Just meine 2 Pfennige,
Peter
On Thu, 21 Oct 1999, Anna Barnes wrote:
> Dear All
>
> On some of our analyses of Tc99m HMPAO SPECT images using a simple
> subtraction paradigm in SPM we some times get significant changes in white
> matter areas. Our explanation (to ourselves) in the past for this happening
> is that the spatial normalization of the SPECT scans is not entirely correct
> when compared to the online Talairach atlas, collated by MNI. However, in
> some cases the mismatch between the Talairach and our images would have to
> be quite large and the same across a group of subjects in order to explain
> some of our results. So another explanation would be that the grey matter
> threshold set at 0.8 is not excluding white matter from our SPECT scans. My
> question to you all then is how valid would it be to comment on these white
> matter changes that SPM is detecting? Are they real?
>
> Regards
>
> Anna Barnes PhD
> Dept of Clinical Physics
> Institute of Neurological Sciences
> Southern General Hospital - NHS Trust
> Glasgow, Scotland, UK
>
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-----------------------------------------
Peter Erhard, Ph.D.
Nuklearmedizinische Klinik und Poliklinik
Klinikum rechts der Isar
Technische Universitaet Muenchen
Ismaninger Strasse 22
81675 Muenchen
Germany
Tel: 49-89-4140 4570
Fax: 49-89-4140 4938
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