On 1/10/2023 2:26 PM, Xiao Da wrote:
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Dear FreeSurfer team,
I am currently using Gray to White Matter Signal Ratio (GWR) to analyze our longitudinal AD/MCI MRI data.
I feel a little confused about the interpretation after reading some recent papers like Putcha et al, 2022 or Jefferson et al, 2015 and some early papers like Salat et al, 2011 and I hope Freesurfer team could help me confirm if my understanding is correct.
1, Freesurfer “recon-all” generates the GWR map by default using “pctsurfcon” and the T1 image. The formula is
100*(W-G)
GWR = ---------
0.5*(W+G)
The white matter is sampled 1mm below the white surface. The gray matter is sampled 30% the thickness into the cortex.
This is correct. Is there a question?
2, Gray to White Matter Signal Ratio (GWR) generated by “recon-all” is the same as Gray and White Matter tissue contrast. So
Gray to white matter signal intensity ratio (GWR) declines across the lifespan?
AD patients have smaller GWR than cognitively normal elders?
Decrease of GWR is observed with increasing AD disease severity?
Aren't those questions addressed in the papers you mention above?
Thank you so much and best regards,
*Xiao Da*
Senior Data Scientist
Cognito Therapeutics, Inc.
1218 Massachusetts Ave, Cambridge, MA 02138
xda@cognitotx.com
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