Dear Dr Doug,
Thank you very much for the detailed answer! I like very much the idea to adjust surface area by eTIV. Kindly I have the following follow-up questions and I highly appreciate your input: 1. Can this adjustment be done in Qdec by including eTIV a covariate or nauisance factor? 2. The individual ROIs for an external statistical software (e.g. SPSS): Can the adjustment be done by measuring the percent volume or surface relative to eTIV then make the comparison between the groups ( i.e. adjusted ROI volume = ROI volume*100 / eTIV) 3. Which approach is recommended: Adjust volume or surface area by adding eTIV as a confounding factor in surface based analysis (e.g. in Qdec) or by comparing the adjusted volume and surface area for the ROIs in SPSS
Regards, John
-----Original Message----- From: freesurfer-bounces@nmr.mgh.harvard.edu [mailto:freesurfer-bounces@nmr.mgh.harvard.edu] On Behalf Of Douglas N Greve Sent: Monday, May 8, 2017 5:55 PM To: freesurfer@nmr.mgh.harvard.edu Subject: Re: [Freesurfer] Surface area
Yes, I would recommend making some kind of adjustment. As with all such adjustments, the adjustment you choose will dictate how you interpret the results (eg, a eTIV adjustment means something different that an adjustment for whole brain volume). For surface area, I usually adjust the eTIV. It might seem strange to adjust surface area by a volume, but for a highly folded surface, the surface area actually goes up linearly with the volume. But adjusting by total surface area is ok too.
On 05/08/2017 02:29 PM, John Anderson wrote:
Dear Freesurfer experts,
I know that the grey or white matter volume measures for the ROIs
reported in "wmparc.mgz" can be adjusted for the total intracranial
volume.... Is is correct to do the same for surfaces? I mean can the
surface of an ROI (e.g. precentral) be adjusted to total surface area?
If yes, this must be done for total white right or total left
depending on the ROI if it is left or right, correct?
Thank you
John
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Douglas N. Greve, Ph.D.
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