You might be able to run both through longitudinal samseg as samseg will
create a "base" image from both and try to bias correct both with
respect to this image.
On 7/21/2021 1:31 PM, Fischl, Bruce wrote:
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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