It all comes down to the registration. See https://surfer.nmr.mgh.harvard.edu/fswiki/eTIV The image may have more-or-less neck and that can change the registration and ICV. The contrast may be different. The scanner may have had software updates. You might be comparing dewarped vs not dewarped.

On 9/10/2020 2:16 PM, Gonzalo Rojas Costa wrote:

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Hi:

Why I got a big ICV difference between MPRAGE of the same patient (2019: 1775887.317631, 2020: 1566398.53576 mm3), one-year difference acquisition, and the same MRI Skyra 3T equipment? I used freesurfer 5.1.0 on the same computer, and operating system in both cases...

I reviewed the coregistration to MNI305 and it is reasonably good in both cases...

The case was reviewed by an expert neuroradiologist, and she does not consider that there is a significant visual difference between both sizes.

Sincerely

Gonzalo Rojas Costa

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