There isn’t really anything available for the latter approach. I would suggest
the former and potentially including site as a nuisance variable. You very much
want to balance across site in terms of whatever effect you are looking for
(e.g. don’t scan all your patients on one and all your controls on the other)
Cheers
Bruce
From: freesurfer-boun...@nmr.mgh.harvard.edu
<freesurfer-boun...@nmr.mgh.harvard.edu> On Behalf Of AJ
Sent: Wednesday, July 21, 2021 1:15 PM
To: Freesurfer support list <freesurfer@nmr.mgh.harvard.edu>
Subject: Re: [Freesurfer] Intensity equalization
External Email - Use Caution
Thank you so much for your reply.
I have subjects who got MRIs on either GE or PH. There are mild image
intensity differences between the two scanners. To combine volumetric data
from both scanners, an easier way would be to express volumes as percentage of
sbTIV (a less variable measure than eTIV) from respective scanners using
SAMSEG. Or more involved process would be intensity normalization of scans to
each other and then subsequent SAMSEG analysis. I think the former approach is
easier and still valid? The later approach would require an additional
program, if you would suggest one?
Many thanks
AJ
On Wed, Jul 21, 2021, 09:40 Fischl, Bruce
<bfis...@mgh.harvard.edu<mailto:bfis...@mgh.harvard.edu>> wrote:
Hi AJ
No, not easily. Maybe you can tell us your overall goal to see if we can help?
Cheers
Bruce
From:
freesurfer-boun...@nmr.mgh.harvard.edu<mailto:freesurfer-boun...@nmr.mgh.harvard.edu>
<freesurfer-boun...@nmr.mgh.harvard.edu<mailto:freesurfer-boun...@nmr.mgh.harvard.edu>>
On Behalf Of AJ
Sent: Wednesday, July 21, 2021 1:27 AM
To: Freesurfer support list
<freesurfer@nmr.mgh.harvard.edu<mailto:freesurfer@nmr.mgh.harvard.edu>>
Subject: [Freesurfer] Intensity equalization
External Email - Use Caution
Hi,
I have 2 MRIs on different scanners. The tissue contrasts are slightly off and
there is slight differences in the volumes of ROIs. Is there a way to make both
MRIs have the same intensity? I.e., Im2's intensity follows Im1's intensity?
Many thanks
AJ
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