关于用统计分析模块分析VMHC结果的疑问

dear marc.

i encountered the same question a few days ago. 

- if you would like to compare the volume of gray or white matter in total
between two or more groups, you have to extract the data with help of an vbm
tool (maybe dartel or vbm 5.1 in spm5) from the normalized and modulated
tissue images (either gray or white matter). in vbm 5.1 there is a simple
tool under the options which extracts the volumes for each subject
separately. maybe you should look in the manual.

- if you would like to compare the volumes of gray matter between two groups
for a specified ROI, john ashburner provided me with a very helpful script
to extract those. For this you should habe a binary (o,1) mask for your Roi
which is used to extract the data from the modulated and normalized gray
matter images. the script is as follows. just copy this into matlab and
follow the instructions. the output is in litre.

good luck

markus

Vmask  = spm_vol(spm_select(1,'image','Select the binary mask')); Vdata  =
spm_vol(spm_select(Inf,'image','Select modulated warped GM')); volume =
zeros(numel(Vdata),1);

for j=1:numel(Vdata),
    tot = 0;
    for i=1:Vdata(j).dim(3),
        M    = spm_matrix([0 0 i]);
        img  = spm_slice_vol(Vdata(j),M,Vdata(j).dim(1:2),0);
        Mmsk = Vmask.mat\Vdata(j).mat*M;
        mask = spm_slice_vol(Vmask,Mmsk,Vdata(j).dim(1:2),0);
        img  = img.*mask;
        img(~isfinite(img)) = 0;
        tot = tot + sum(img(:));
    end
    voxvol    = abs(det(Vdata(j).mat))/100^3;
    volume(j) = tot*voxvol;
end

disp(volume)