Hi Kristine
the aseg.stats volume uses partial volume correction to get subvoxel
accuracy.
cheers
Bruce
On Fri, 23 Mar 2018, Lee Subin Kristine wrote:
Hi,
I have a question about volume info from freesurfer vs matlab.
I am looking at, say, the left hippocampus volume from asegstats, which was
3778.2 mm^3.
When I try to get the same volume by loading aseg.nii on matlab, however, I get
a different number,
3945.
For matlab, I used the following command, which counts the number of voxels
equal to the left
hippocampus segment id:
length(find(aseg.img==17))
This was done after I converted the original aseg.mgz file into native space,
using 2 different
methods:
(1) mri_convert -rl rawavg.mgz -rt nearest -i aseg.mgz -o bert_aseg.nii
(2) mri_label2vol --seg aseg.mgz --temp rawavg.mgz --o bert_aseg.nii
--regheader aseg.mgz
In both cases, the output was 3945.
The rawavg.mgz used here is also 1mm isovoxel, so I don't think it is due to
the difference in voxel
dimensions.
What could be the cause of the difference in volume?
Thanks,
Kristine
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