Hello,

A paper by Randy Buckner et al (NeuroImage, Vol 23, 2004, pp724-738) indicates that it is possible to quickly estimate total intracranial volume (eTIV) based on the "Atlas Scaling Factor" required to perform the transformation of a subject's scan to match a specific atlas.

In the blog entry "Storage of Talairach Transformation"
RW Cox writes:
"You could extract the 360 numbers from the WARP_DATA field using the command
3dAttribute WARP_DATA anat+tlrc
for example -- this writes to stdout, which I suppose you could pipe into another program to calculate the determinants you want. "

Question: would calculating the determinant of this afni talairach transform matrix provide an equivalent "atlas scaling factor" with which I could calculate eTIV for our subjects? The Freesurfer program estimates total intracranial volume (eTIV) in the Buckner et al (2004) manner. Essentially, I'm interested in comparing the "atlas scaling factor" from the AFNI talairach transform to the scaling factor generated in the equivalent Freesurfer atlas transform. I appreciate any suggestions you have.

Thanks much,
Paul