Hi - you will need to look at the details in the FSLVBM scripts to see
how these standard space images are generated - then you'll be able to
reproduce the same measures with your own (e.g.) ROI definitions. For
example, whether the modulation includes the affine part of the
transformation or not will affect these calculations.
Cheers, Steve.
On 2 Sep 2009, at 21:57, Ryan Shimotsu wrote:
> Hi Everyone,
>
> I'm trying to validate my FSLVBM results with a different region of
> interest
> method. What I'm looking for are individual subjects' modulated gray
> matter
> PVEs in standard template space. The most likely image I found so
> far is
> <ID>struc_GM_to_template_GM_mod.nii.gz, but when I sum up the voxel
> intensities across the entire image and multiply it by the voxel
> dimensions
> (2x2x2=8), I don't get nearly the same result that I get when
> summing up the
> intensities from the original PVE and multiplying the result by the
> voxel
> dimensions of that image. Rather, the GM_mod volume is about 25%
> higher than
> the PVE in native space. I also tested the "GM_to_T" and
> "GM_to_Template_GM"
> images with similar results. Shouldn't the modulated image preserve
> volumes?
>
> Thanks in advance,
> Ryan
>
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Stephen M. Smith, Professor of Biomedical Engineering
Associate Director, Oxford University FMRIB Centre
FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
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