External Email - Use Caution
Dear Petsurfer experts,
I used partsurfer in FS6 and had applied partial volume correction (PVC) on PET
data. I followed the same steps as in wiki which was very well explained! Thank
you!.
The analyses went fine... I would like to inquire about some issues, and I
highly appreciate any clarification:
1. The flag --psf in "mri_gtmpvc": Is the value of "psf" means the amount of
smoothing (fwhm in mm) that will be applied on the corrected maps? If I give
"psf" a value of "zero", does this means that the corrected maps are no longer
going to be smoothed? The motivation of the question is that I would like to
smooth the images at the end of the analysis, so I can apply the amount of
smoothing on the PVC images vs analysis involve non-pvc images.
2. For some of my group analyses, I don't see any difference between the
groups. When I apply PVC using "mri_gtmpvc", I see difference in pathologically
relevant regions, and vice versa for some other analyses where I see difference
between the groups without PVC then the difference disappear following PVC. I
highly appreciate if you please clarify why PVC can find results or eliminate
findings. What is the idea of partial volume effect PVE in this case?
3. Group analysis: following PVC, I used "mri_concat" to combine the images
"?.mgx.gm.nii.gz", then I smoothed the final combined images using the flag
"fwhm" in "mri_surf2surf". I used fwhm=3mm and then fwhm=6mm. For all analyses
I can see clusters of difference between the groups at fwhm=3mm. For some
analyses the difference disappears when I use fwhm=6mm . Is this till a partial
volume effect even after applying pvc or this is relevant to an extra
smoothing effect which obscure the PET signal? is there any recommended fwhm
value for PET images?
Thank you for your guidance,
John
_______________________________________________
Freesurfer mailing list
Freesurfer@nmr.mgh.harvard.edu
https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
The information in this e-mail is intended only for the person to whom it is
addressed. If you believe this e-mail was sent to you in error and the e-mail
contains patient information, please contact the Partners Compliance HelpLine at
http://www.partners.org/complianceline . If the e-mail was sent to you in error
but does not contain patient information, please contact the sender and properly
dispose of the e-mail.
