Dear SPM users
I have done optimised VBM on AD brains and determined the volumes of
GM/WM/CSF. The mean volumes are:
GM = 0.701 l
WM = 0.459 l
CSF = 0.745 l
Total = 1,906 l
I do not trust in these volumes because they are too large.
But in the literature there are also papers that report large
GM/WM/CSF volumes (e.g. Good et al., 2001, NeuroImage 14, 21-36)
GM = 0.829 l
WM = 0.454 l
CSF = 0.397 l
Total = 1,68 l
Therefore my questions are:
1. any ideas what was going wrong or what happens with these volumes?
2. is it possible that the percentages of GM/WM/CSF are always related to
the default
bounding box and therefore independent from the customised bounding box
dimensions
(I have worked with a customised bounding box because parts of the
cerebellum and
the apex were cut with the default bounding box --> i.e. I have only
enlarged the
Z-coordinates)?
3. can the large volumes explained by the larger bounding box that caused
additional structures
like brain stem and cerebellum also to be segmented and therefore enlarge
the segmental volumes?
4. is it also possible that the volume enlargements came from the nonlinear
normalisation?
5. In order to control the large volumes I have also tried the following
function 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);
for GM: 838197 voxels, -0.838197 litres
for WM: 553626 voxels, -0.553626 litres
for CSF: 1.01618e+006 voxels, -1.01618 litres
why there is a negative foresign?
whole brain volume (GM/WM/CSF) is about 2.397 liters!!!
Solutions, tips and comments are highly appreciated
Thanks a lot in advance
Best regards
Juergen
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Juergen Haenggi, Ph.D. student
Division of Psychiatry Research
Psychiatric University Hospital
University of Zurich, Switzerland
P.O. Box 1931
Lenggstrasse 31, 8032 Zurich
0041 44 384 26 10 (office phone)
0041 76 445 86 84 (mobile phone)
0041 44 384 26 86 (fax)
H 115 (office room number)
[log in to unmask] (division email)
http://www.dpr.unizh.ch/ (division website)
http://www.juergenhaenggi.ch (private website)
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