[Freesurfer] FLAIR to improve pial segmentation? What are the surfaces used for stat estimation?

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Hi FS community,

I started using FS 7.1.0 for cortical and subcortical parcellation/segmentation.

As I found information that FLAIR data could improve pial surfaces creation, I decided to try it on since I have FLAIR images besides MPRAGE, by using the command line form FSwiki:

RECON-ALL -SUBJECT NAME -I INPUT_VOLUME.NII -FLAIR FLAIR_VOLUME.NII -FLAIRPIAL -ALL

However when I opened Freeview, I overlaid RH.PIAL, and RH.PIAL.FLAIR, RH.PIAL.T1.

The first two are quite similar (overlap) and the segmentation is worse than rh.pial.T1.

So, my question is, what is really the final surface of recon-all that must be checked for errors and that is used for stats estimation?

Thank you in advance.

Best regards,

Otília