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-boun...@nmr.mgh.harvard.edu
[mailto:freesurfer-boun...@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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MGH-NMR Center
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