I thought I answered this question last week. See my rsponse below
I don't think it is correct conceptually. By including SNR as a
covariate, you are saying that you expect the thickness to increase
with higher SNR and decrease with lower SNR. This does not make
sense to me. It sounds like you are trying to do a mixed effects
analysis where you weight by the SNR. Still, mathematically, this is
not a true mixed effect analysis (which requires estimates of the
within and between subject noise). `
On 8/3/18 10:57 AM, John Anderson
wrote:
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Daer FS experts,
I would like to inquire about including SNR as a covariate for
the between groups cpmparison in cortical thickness. Is this
procedure correct mathematically? Do I need to demean the SNA
values before including it covariates? Finally, do you recommend
any quality parameters other than SNR to be included covariate?
I look forward to learn from your expertise,
Thanks,
John
On 8/5/18 1:04 PM, John Anderson wrote:
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Dear FS experts,
I would like to inquire about including SNR as a covariate
for the between groups comparison in cortical thickness. Is
this procedure valid? I have some T1 images of low quality and
the majority are high in quality. I reviewed the segmentation
and the cortical surfaces and fixed manually as possible. I
don't want to exclude images from the data sets, so I am
thinking of regressing out SNR.
It seems that the command "mri_segstats" can report SNR for
every ROI in the brain. Is it correct to include whole brain
SNR covariate for between group comparisons (cortical
thickness and volumetric analyses).
If yes, do I need to include actual SNR values in the FSGD
file or the demeaned values ?
We appreciate your guidance!
John
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