The two methods are totally different. See MailScanner has detected a possible fraud attempt from "secure-web.cisco.com" claiming to be https://surfer.nmr.mgh.harvard.edu/fswiki/sbTIV
the sb version actually performs a skull segmentation  and counts voxels within skull. The eTIV is computed from the talairach registration, which is going to be inherently more variable (eg, more or less neck will affect it).

On 7/20/2021 3:24 PM, AJ wrote:

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Hi,

I am looking at interscanner differences between Philip and GE.  I get significantly less variation between the scanners when looking at sbTIV (coefficient of variation < 1.5 %)  than  eTIV (12%) within subjects.   Any thought as to why?  Normalizing ROIs with sbTIV improves these differences even more.

Thanks for your help.

AJ

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