I've looked into this a little bit. I looked at the area of the original manual labels for entorhinal as found in the aparc. They do show a lh>rh asym of 3%, but it is not significant (p=.45). I looked at the automatic labels in two other large data sets. I found significant lh>rh asym of ento area in both of about 8-10%. I don't consider 10% asym in area to be a symptom of something problematic. This would represent an expansion or contraction of the entorhinal border of about 0.5mm. I'm guessing that this is beyond the accuracy that we can expect. I was looking at surface area, but now I see that you are looking at volume. The manual labels were defined on an areal basis, and I assume that that was the basis of the volume asym, but it could be due to differences in thickness. How big a difference are you seeing in volume? Can you look at area and thickness to see if you see differences there? Also, the surfaces are really hard to place in this area. Oftentimes, the ento will have a big bite in it that has to be fixed manually. I don't think there is asym in the bites, but it could make a particular case look extreme. In general, we don't recommend doing laterality studies with the aparc as none of the steps involved have been developed to make sure that laterality artifacts are removed. In this case, it sounds like you are checking laterality for QA purposes?

On 3/13/2024 9:30 PM, Katie Vandeloo wrote:

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Hi Dr. Greve,

I hope you are doing well. I am hoping to get in touch with someone from MGH about some issues with Freesurfer 7. Our group hasn’t yet been successful in finding the right person to talk to about this!

We noticed that there are large discrepancies between left and right hemisphere volumes of the perirhinal cortex (exceptionally small volumes in the right hemisphere) in the outputs of recon-all for Freesurfer 7 but NOT Freesurfer 6. I have reached out to other labs who observed the same pattern. I think there is something systemic about Freesurfer 7 that should be looked into. Just wanted to make someone aware - please let me know if there is someone else I should contact about this.

Thank you for your time!

Kind Regards, Katie Vandeloo