Hi Ziad,

Thanks for your help. I've come across the following references that may be helpful? The first describes an automatic algorithm for segmentation of the brain and total intracranial CSF (called Exbrain v.2), whereas the second and third compare various methods of estimating ICV. The third article article also describes a method for estimating ICV with reverse MNI brain masking.

1. Louis Lemieux, Alexander Hammers, Toby Mackinnon, and Rebecca S.N. Liu. (2003). Automatic segmentation of the brain and intracranial cerebrospinal fluid in T1-weighted volume MRI scans of the head, and its application to serial cerebral and intracranial volumetry, Magnetic Resonance in Medicine, 49: 872-884.

2. Pengas, George; Pereira, Joao; Williams, Guy B; Nestor, Peter J. (2009). Comparative Reliability of Total Intracranial Volume Estimation Methods and the Influence of Atrophy in a Longitudinal Semantic Dementia Cohort. Journal of Neuroimaging. 19(1):37-46.

3. Keihaninejad, Heckemann, Fagiolo, Symms, Hajnal, & Hammers. (2010). A robust method to estimate the intracranial volume across MRI field strengths (1.5T and 3T). NeuroImage. 50:1427-1437.