yes, that is correct. However, understand that there might only be a difference of 1mm between those two locations, so it could easily be a partial volume effect
On 01/11/2017 08:50 AM, John Anderson wrote: > Thank you Doug, > Exactly! I meant GM near the CC. > When I used "projfrac=0.5 " there was no differnce between the groups > at "cwp 0.05", and when I changed the "projfrac to 0" I got > significant differnce between the groups in specific areas at "cwp > 0.01". Kindly, how can this be explained? I highly appreciate if you > help me to understand this point: > For "projfrac =0" I expect the surface based analysis to > be running close to white matter. Right? and when I used > "projfrac=0.5" the analysis is running in the middle area between pial > and white. When the analysis is not showing any differne between the > groups for "projfrac 0.5" and showing differnce for "projfrac 0" that > means the differnce between the groups is deeper and closer to white > matter. Is this correct? > Thank you for any input and clarification! > Bests, > John > *Sent:* Tuesday, January 10, 2017 at 10:51 AM > *From:* "Douglas Greve" <gr...@nmr.mgh.harvard.edu> > *To:* freesurfer@nmr.mgh.harvard.edu > *Subject:* Re: [Freesurfer] surface based analysis (projfrac) > > When you say in the corpus callosum, do you mean in WM? The > surface-based analysis is only for cortical GM. If you mean in GM near > the CC, then the analysis is appropriate. The projfrac parameter sets > the sampling location between the white and pial surfaces where 0.5 > means half way. > > On 1/10/17 8:07 AM, John Anderson wrote: > > Dear FS experts, > I am working on surface based analysis using freesurfer. I want to > inquire about the flag "projfrac" in the command "mris_preproc" > I ran voxel wise analysis including the same subjects. I found > differnce between the groups in areas close to the corpus > callosum. I want to get the same results using surface based > analysis. If I use the projfrac=0.5 is this able to show the same > results that I got in voxel wise analysis at the level of the > corpus callosum. Do I need to use differnt number for projfrac ? > Thank you for any advice. > > Best, > John > > _______________________________________________ > 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 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. > > > _______________________________________________ > Freesurfer mailing list > Freesurfer@nmr.mgh.harvard.edu > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer -- Douglas N. Greve, Ph.D. MGH-NMR Center gr...@nmr.mgh.harvard.edu Phone Number: 617-724-2358 Fax: 617-726-7422 Bugs: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting FileDrop: https://gate.nmr.mgh.harvard.edu/filedrop2 www.nmr.mgh.harvard.edu/facility/filedrop/index.html Outgoing: ftp://surfer.nmr.mgh.harvard.edu/transfer/outgoing/flat/greve/ _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
