Hello,

I am measuring the changes of subcortical volumes in a longitudinal study, so I took the volumes from longitudinal subjects (name.long.base). Now we need to perform the correction using the eTIV parameter, but the eTIV for longitudinal subjects for all time points is the same (i.e. eTIV for subject-time1.long.base = eTIV for subject-time2.long.base)

Is it correct to perform the correction using the eTIV values from the longitudinal subjects, or we should use these measures from the cross-sectional corresponding subjects ?

Thanks,

Alex.