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Hi Carly,


plus, if I may answer in addition, make sure that the ICV differences are checked with sex as covariate,

so that statement of yours is only valid, if analyzed also per sex separately, or with sex as covariate.


Next, you should also (once) test for ICV-by-Dgx effects, as you cannot know in advance, if the relationship

between ICV and local measures is the same.


Best,

Philipp Sämann



Von: freesurfer-bounces@nmr.mgh.harvard.edu <freesurfer-bounces@nmr.mgh.harvard.edu> im Auftrag von Iglesias Gonzalez, Juan E. <JIGLESIASGONZALEZ@MGH.HARVARD.EDU>
Gesendet: Montag, 8. Juli 2024 19:39
An: Freesurfer support list
Betreff: Re: [Freesurfer] Is ICV needed as a covariate if matched between groups
 

It’s always a good idea to divide the volumes by ICV (or add ICV as a regressor). This is very unlikely, but what if your controls happened to have smaller heads than your patients? For peace of mind, I’d correct by ICV.

Cheers,

/Eugenio

 

--

Juan Eugenio Iglesias

http://www.jeiglesias.com

 

From: freesurfer-bounces@nmr.mgh.harvard.edu <freesurfer-bounces@nmr.mgh.harvard.edu> on behalf of Carly McIntyre-Wood <mcintc10@mcmaster.ca>
Date: Monday, July 8, 2024 at 12:06 PM
To: freesurfer@nmr.mgh.harvard.edu <freesurfer@nmr.mgh.harvard.edu>
Subject: [Freesurfer] Is ICV needed as a covariate if matched between groups

        External Email - Use Caution        

Hi there,

 

I am investigating differences in hipp/amyg volume between a patient and HC sample and am wondering if there is any reason I would still need to include ICV as a covariate if the groups do not differ on ICV (p=.793).

 

Thanks so much,

Carly