Dear SPMers,
today, I have two questions on VBM using SPM5b:
1.a)
Is it still possible/advisable to use the following function:
function gl = get_integrals(P)
% Integrate the values in an image.
if nargin<1,
P = spm_get(Inf,'*.img');
end;
V = spm_vol(P);
gl = zeros(length(V),1);
for i=1:length(gl),
for z=1:V(i).dim(3),
img = spm_slice_vol(V(i),spm_matrix([0 0 z]),V(i).dim(1:2),0);
gl(i) = gl(i) + sum(img(:));
fprintf('.');
end;
fprintf('\n');
end;
1.b)
If so, can I use this function separately for modulated and unmodulated normalised GM- and WM-images produced by the SPM5b segmentation step, i.e. smwc1*.img, smwc2*.img, swc1*.img, swc2*.img ?
Then, I would use the four different sets of integrals/globals that will be produced by this function as covariates of no interest during the four respective analyses, i.e. GM-/WM-vol and GM-/WM-"density".
2.) I realised that, unlike in SPM2, the segmented images (smwc1*.img etc, see above) in SPM5b have a resoluation of 2x2x2 mm since the new SPM5b-templates and prior probability maps have this resolution.
The images I start with in native space, though, are 1x1x1 mm. Therefore I wonder whether it might be preferable to use templates and prior maps with the same, 1x1x1 mm, resolution? Or doesn't it make any difference?
I simply do not know at what stage during the new integrated segmentation step the resolution is decreased to 2x2x2 mm and whether partial volume effects could be diminished by keeping it up at 1x1x1 mm.
Many thanks for your help!
Nicolas
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