deletions | additions       diff --git a/Freesurfer_uses_an_atlas_scaling__.tex b/Freesurfer_uses_an_atlas_scaling__.tex  index a71e30d..2f1e78c 100644  --- a/Freesurfer_uses_an_atlas_scaling__.tex  +++ b/Freesurfer_uses_an_atlas_scaling__.tex 
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Freesurfer uses an atlas scaling factor (ASF) to calculate the eTIV, so even though the ROI encompasses all others, it is not calculated in the same way as other ROIs (i.e. by counting the voxels inside the skull). Rather, it estimates a linear transformation to an atlas space (Talairach) and calculates the determinant of the transformation matrix, which correlates to ICV \cite{buckner2004unified}. So actually the mechanism behind the biases in eTIV are different than those behind other regional volumes (i.e. regional varaition variation  in CNR and gradient distortions affect the boundary). Because of this, the eTIV results were removed. However, as stated in the previous response, the eTIV registration of scans were QC'd, particularly in sites 4,6 and 11 and 1 scan from each site that had a bad registration were removed. Test retest reliability of eTIV was included, butit  was excluded from the scaling factor calculations and validations.