Dear Gelareh,
The units of volume and both voxels (first number) and mm^3 (second number).
The best way to calculate the volume is to multiple the mean value by the
volume (get the output of -M and multiply by the second output of -V) which
will then give you the most accurate estimate of GM volume in mm^3, as it
takes into account all of the partial volume contributions. The result from
just the -V output is an overestimate as it counts the entirety of any voxel
that contains any non-zero amount of GM partial volume.
All the best,
Mark
On 19 Apr 2012, at 07:21, Gelareh Ahmadi wrote:
> Dear FSL experts,
>
> I ran VBM for my images. During its process all brain-extracted images are segmented into GM, WM and CSF. So the image *_struc_GM.nii.gz is the GM images. How can I calculate the volume of the gray matter by this image?
>
> Is it correct to use fslstats? is it correct to write below script:
> fslstats -t *_struc_GM.nii.gz -V >> gary_matter_volume.txt
>
> And what is the unit of this volume??
>
> If I use -M, instead of -V then it will give me the mean of the gray matter not the whole volume, is it correct?
>
> I would highly appreciate if you could help me with this regard,
>
> Thank you in advance for your kind assistance,
>
> Best Regards,
>
> Gelareh
>
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