> 1) Is it mandatory to manually reorient each image to AC-PC line before VBM
> preprocessing when using VBM2 script by Dr Gaser ? Actually, in my VBM
> study of group analysis, I have examined both (with and without AC-PC
> reorientation) and the result maps were identical.
If the images are approximately aligned with the templates then the initial
affine registration is much more robust. In principle, images need to be
within about 3cm and 15 degrees for things to work - but these figures depend
on your data.
>
> 2) In within-group interaction VBM analysis, (for example, Daniels et al,
> Neurology 2006 Oct 24;67(8):1452-6) ,
>
> (Patient_condition A > control A) > (Patient_condition B > control B)
>
> which analytic model should I choose in spm2 ?
> and how can I set up t-statistics ?
I have no idea which option will give you the appropriate design matrix, but
basically you want the subjects entered as four groups. If the groups are
Patient_condition A, control A, Patient_condition B and control B, then you
would test using a contrast of 1 -1 -1 1.
Best regards,
-John
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