On 05/02/2016 07:39 AM, maaike rive wrote: > Dear freesurfer experts, > > > > > I have a question regarding correction of cortical measures or global > measures (ICV, total surface area). As I understand from literature > and the freesurfer wiki, a model for thickness should not be corrected > for ICV (since thickness does not scale with total brain volume), but > surface area should be corrected since is does scale with total brain > volume. Three questions: > > > > > > 1. should I use ICV or should I use total surface area (TSA) as > covariate in the model to correct surface area (by the way, average > ICV and TSA do not differ between the groups to compare )? > > Not sure. They will be different models. ICV should not change over the lifetime whereas total surface area will. > > 2. does lGI also need correction? does it scale with volume? If so, do > I need to correct for ICV or for TSA? Usually I see no correction but > some do use ICV... > > I don't know, perhaps Marie will weigh in > > 3. even if the average of certain measures (like ICV/TSA, or gender, > or age) does not differ between groups, should they be added to the > model? If I do not correct for gender, for example, my results change > and most papers do use age and gender as covariates if they compare > groups despite a lack of differences between groups... > > They can still reduce intersubject variance. doug > > > > > Thanks, > > > > > > Maaike > > > > > _______________________________________________ > 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 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.
