Hi - SIENAX gives you volume of grey, white, optionally "ventricular CSF", etc. but doesn't directly calculate ICV (ie including all CSF I guess) - are you sure you're comparing like with like?

Cheers.

On 12 Jul 2012, at 17:28, Owen, Julia wrote:

Hi,

I am trying to get ICVs for a group of subjects using sienax. I know that sienax will give a scaling factor between each subject and the MNI152 template, so with the volume of the MNI template, I can back calculate ICV. I found this post: https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=ind1206&L=FSL&P=R62911&1=FSL&9=A&I=-3&J=on&d=No+Match%3BMatch%3BMatches&z=4, which provides a volume of 1847712 mm^3 for the MNI template. When I use this volume and compare to the ICVs obtained from SPM and FreeSurfer, I find that the ICVs from sienax are consistently 15% less than those obtained with SPM and FS. So, I can only conclude that 1847712 mm^3 is not the true volume (or there is some systematic bias, but it's easier to believe that this MNI ICV is off). Does anyone have a more accurate volume? Or any ideas about what I am doing incorrectly?

Thanks in advance, Julia

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