Overview of the study protocol. Overview of the study protocol is presented. The study has two phases with phase I implemented two months leading to phase II. Input to both phases of the study is the MRI T1-weighted image volume of the subject. In phase I, Reference manual segmentation of ICV is measured by Operator 1 and the corresponding error of the ICV estimated through automatic software is determined, for Freesurfer, for FSL and for SPM. Inter-operator variability, , is also calculated in this phase as the error between estimated ICV by Operator 1 and estimated ICV by Operator 2. For the phase II of the study, Intra-operator variability, , is calculated as the error between estimated ICV by Operator 1 in phase I and estimated ICV by the same operator in phase II. The automatic measurements of ICV using Freesurfer, FSL and SPM are repeated and the corresponding errors are calculated as for Freesurfer, for FSL and for SPM.