[Freesurfer] surface and cortical thickness normalization

[yunus soleymani]

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 Hello,

I hope you are doing well. Yesterday, I had some questions regarding 
normalization in Freesurfer. Thanks to Dr. Douglas N. Greve, I received answers 
for all of them. However, I still have one more question. 

When I normalize brain surfaces to eTIV, they appear to be in two different 
units (mm2 and mm3). Will this be a problem? Additionally, I would like to know 
your thoughts on normalizing cortical thicknesses. Do you think they should be 
normalized to eTIV, or would it be better to normalize them to the mean 
cortical thickness of each subject? 

I would greatly appreciate your response.

Thank you,
Yunus

Yunus
 Soleymani
Ph.D. Candidate of Neuroimaging Tehran University of Medical Sciences
soleymani.yu...@yahoo.com+98 914 526 
9298
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Re: [Freesurfer] surface and cortical thickness normalization

[Fischl, Bruce R.,PHD]

Hi Yunus

I think typically you would normalize by eTIV^(2/3), which would result in a 
dimensionless scaling

Cheers
Bruce

From: freesurfer-boun...@nmr.mgh.harvard.edu 
 On Behalf Of yunus soleymani
Sent: Friday, May 3, 2024 3:31 AM
To: freesurfer@nmr.mgh.harvard.edu
Subject: [Freesurfer] surface and cortical thickness normalization


External Email - Use Caution
Hello,

I hope you are doing well. Yesterday, I had some questions regarding 
normalization in Freesurfer. Thanks to Dr. Douglas N. Greve, I received answers 
for all of them. However, I still have one more question.

When I normalize brain surfaces to eTIV, they appear to be in two different 
units (mm2 and mm3). Will this be a problem? Additionally, I would like to know 
your thoughts on normalizing cortical thicknesses. Do you think they should be 
normalized to eTIV, or would it be better to normalize them to the mean 
cortical thickness of each subject?

I would greatly appreciate your response.

Thank you,
Yunus





Yunus Soleymani



Ph.D. Candidate of Neuroimaging

Tehran University of Medical Sciences



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Re: [Freesurfer] surface and cortical thickness normalization

[Douglas N. Greve]

The reason I suggested scaling by eTIV is an analogy with a box of 
paper. The surface area of the paper in the box scales linearly with the 
volume in the box (twice the volume, twice the paper, twice the area). I 
vaguely remember doing a test of this, but, if I did, it has been a 
while. probably using eTIV^(2/3) works well too. I don't think it is so 
important that it be unitless (though maybe it is easier at review time).


On 5/3/2024 10:56 AM, Fischl, Bruce R.,PHD wrote:


Hi Yunus

I think typically you would normalize by eTIV^(2/3), which would 
result in a dimensionless scaling


Cheers

Bruce

*From:*freesurfer-boun...@nmr.mgh.harvard.edu 
 *On Behalf Of *yunus soleymani

*Sent:* Friday, May 3, 2024 3:31 AM
*To:* freesurfer@nmr.mgh.harvard.edu
*Subject:* [Freesurfer] surface and cortical thickness normalization

*External Email - Use Caution *

Hello,

I hope you are doing well. Yesterday, I had some questions regarding 
normalization in Freesurfer. Thanks to Dr. Douglas N. Greve, I 
received answers for all of them. However, I still have one more 
question.


When I normalize brain surfaces to eTIV, they appear to be in two 
different units (mm2 and mm3). Will this be a problem? Additionally, I 
would like to know your thoughts on normalizing cortical thicknesses. 
Do you think they should be normalized to eTIV, or would it be better 
to normalize them to the mean cortical thickness of each subject?


I would greatly appreciate your response.

Thank you,
Yunus


*Yunus Soleymani*
**
*Ph.D. Candidate of Neuroimaging *
*/Tehran University of Medical Sciences/*
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+98 914 526 9298


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