Hi Jürgen,
>Dear SPM5b users
>
>I have done optimised VBM with SPM5b and trying to compute
>the volumes of GM/WM/CSF segments.
>
>
Well, did you notice that SPM5 already do a sort of optimized VBM .. and
probably do even better that the usual optimized method. Have a look at
Ashburner & Friston 2005 Unified segmentation NeuroImage 26, 839-851
>But, in SPM2 the Nvox value can be capture in the graphic window
>after segmentation. In SPM5b the Nvox do not appear neither in the
>graphic window nor in .mat or .ps file.
>Therefore I used the following script from John Ashburner:
>
>V = spm_vol(spm_get(1,'*_seg*.img'));
> vol = 0;
> for i=1:V.dim(3),
> img = spm_slice_vol(V,spm_matrix([0 0 i]),V.dim(1:2),0);
> vol = vol + sum(img(:));
> end;
> fprintf('%g voxels, %g litres\n', vol, vol*det(V.mat(1:3,1:3))*1e-6);
>
>but it does work well with all segmented images except the modulated ones in
>SPM5b.
>With the modulated segments it does not work and there is no error message.
>The result is:
>NaN voxels, NaN litres
>
>Where is the problem? What does it mean?
>
>
To get the volume of modulated images in spm5 i use
spm_global(spm_vol('*.img'))
it gives you a value for the modulation (if you * by the number of
voxels then you have the volume)
Hope it's right (maybe if I'm wrong John will correct me)
Best
- cyril
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