I obtained cortical thickness and volumetric results before and after correcting them for defects.

I just did some wm edits and mostly controls points in the top of the head (some subjects had less signal so I put control points in order to allow for a good surface reconstructions).

When comparing the values: 

EXPECTED

- Same volume values for subcortical structures, i.e.: same thalamic volume before and after

- Different CT values in the edited areas and only for the edited subjects, i.e.: lh_paracentral_thickness

- Different volumetric values only for the edited subjects in, for example: lhCortexVol, CortexVol, CorticalWhiteMatterVol

NOT EXPECTED

- Same values for EstimatedTotalIntraCranialVol. 

I was controlling thalamic values with the eTIV, (using Raz 2005's formula)*, but before and after correcting almost half of the subjects, obviously, I obtain the same results. 

- Should I use a different value other than the eTIV?

- Is normal that the eTIV doesn't change but the rest of the values are changing? The brain is definitely different after the control points, it grows a little bit upwards. 

any information on this will be appreciated!

thanks,

Gari 

PS:

* Volume (adj) = Vol(rawi)-b*(ICV(i)-mean ICV), where b is the slope of regression of an ROI volume on ICV