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Dear Freesurfer’s experts,
I have read the paper from Marcoux, et al. « An Automated Pipeline for the
Analysis of PET Data on the Cortical Surface ». Frontiers in Neuroinformatics
12 (10 décembre 2018). https://doi.org/10.3389/fninf.2018.00094
<https://doi.org/10.3389/fninf.2018.00094>. In this paper, they propose a
robust PET signal projection based on weighting multiple PET projections at
different fractions of the cortical thickness. They used « mris_expand" instead
of "mri_vol2surf --projfrac" based on the following comments:
"We mainly rely on the mris_expand function of FreeSurfer rather than on
vol2surf. The vol2surf function allows the user to project volume data onto the
cortical surface by sampling along the normal of the white surface, by steps
corresponding to fractions of the cortical thickness. We observed that the main
issue with this approach is its lack of accuracy and robustness, as there is no
constraint to ensure that the last sample will be on the corresponding vertex
of the pial surface. Another solution proposed by FreeSurfer is to use the
normal fromthemid surface, starting on the side of the white surface and going
toward the pial surface, sampling by steps proportional to the thickness. Here
again we observed that, because of different folding patterns, sampling points
could be located outside the cortical ribbon. Our approach, using deformable
surfaces obtained with mris_expand, ensures that the seven surfaces that are
used to project the signal follow the folding patterns and stay within the
cortical ribbon."
Is "mris_expand" more accurate and robust than "mri_vol2surf --projfrac"
according to you ?
Best,
Matthieu
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