Hello! Everyone!
I want to compute the volume of gray matter in original images. I found
following codes in previous emails from John, but I don't understand what
'voxvol = det(V(1).mat)/100^3;' calculates. Since tot represents the sum of
voxel intensities in modulated gray matter images, the total volume should
be the sum multiplying by the product of the voxel size. If the modulated
image has a voxel size as 1mmx1mmx1mm, is the product of the voxel size is
equal to 1?
If I'd like to compute the global intracranial volume, shall I do all the
same but only replace the modulated gray matter image to the modulated brain
image?
V = spm_vol(spm_get(1,'*.img'))
tot = 0;
for i=1:V(1).dim(3),
img = spm_slice_vol(V(1),spm_matrix([0 0 i]),V(1).dim(1:2),0);
tot = tot + sum(img(:));
end;
voxvol = det(V(1).mat)/100^3; % volume of a voxel, in litres
tot = tot; % integral of voxel intensities
tot*voxvol
Many thanks!
Dr shan shen
Department of Psychology
University of Surrey
Guildford GU2 7XH
UK
