Why is a small # a problem? It simply represents the fraction of the total intracranial volume occupied by that structure.
cheers Bruce On Thu, 24 Oct 2013, Dorian P. wrote: > Thank you Douglas. > The eTIV has values like 1543825. Dividing ROIs by this value would create > very small values. > > Is there a standard TIV (i.e. from the talairach brain) to use as > denominator for creating a ratio value? Or what is the best way to create a > reasonable factor (i.e. 0.7-1.3) to correct/normalize roi volumes? > > Dorian > > > > 2013/10/24 Douglas N Greve <gr...@nmr.mgh.harvard.edu> > > On 10/24/2013 10:37 AM, Dorian P. wrote: > > Dear all, > > > > Excuse if these are simple questions but I am a bit confused > on the > > significance of the volume measures. > > > > 1. Are the volumes of ROIs calculated after normalization? > No, everything is done in native space. > > > > 2. If volumes are calculated post-normalization, why is correction > for > > eTIV needed? > > > > 3. What is the quickest way to correct for eTIV? > Not sure what you mean by the "quickest". Usually the ROI volumes are > divided by the eTIV or the eTIV is used as a regressor > doug > > > > Thank you. > > Dorian > > TJU > > > > > > _______________________________________________ > > 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. > > > > _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
