Re: [Freesurfer] Combination of multiple PET projection: "mri_vol2surf --projfrac" vs. "mris_expand"

[Greve, Douglas N.,Ph.D.]

It might be a little more accurate, but my guess is that it will not 
make much of a difference.

On 1/30/19 2:01 PM, Matthieu Vanhoutte wrote:
>
> External Email - Use Caution
>
> 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. 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
>
> ___
> Freesurfer mailing list
> Freesurfer@nmr.mgh.harvard.edu
> https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer


___
Freesurfer mailing list
Freesurfer@nmr.mgh.harvard.edu
https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer

[Freesurfer] Combination of multiple PET projection: "mri_vol2surf --projfrac" vs. "mris_expand"

[Matthieu Vanhoutte]

External Email - Use Caution

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 
. 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___
Freesurfer mailing list
Freesurfer@nmr.mgh.harvard.edu
https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer