What is the problem with small values? You can multiply them by 100 to give you percent of brain. Or multiply them by 1000 to give you tenths of percents
doug On 10/24/2013 12:58 PM, 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 > <mailto: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 > <mailto: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 <mailto:gr...@nmr.mgh.harvard.edu> > Phone Number: 617-724-2358 <tel:617-724-2358> > Fax: 617-726-7422 <tel:617-726-7422> > > Bugs: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting > <http://surfer.nmr.mgh.harvard.edu/fswiki/BugReporting> > FileDrop: https://gate.nmr.mgh.harvard.edu/filedrop2 > www.nmr.mgh.harvard.edu/facility/filedrop/index.html > <http://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 <mailto: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. > > -- 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
