I am currently using data from the UKBiobank (https://www.ukbiobank.ac.uk/) which has segmented its brain imaging data using Freesurfer tools (https://biobank.ctsu.ox.ac.uk/crystal/crystal/docs/brain_mri.pdf).  I calculated the sum of the FAST cerebellar grey matter volumes and compared them to the sum of the ASEG cerebellar cortex volumes. I only found a correlation around 75%. 

When I adjust both of these measures for TBV (Total Brain Volume, covariate method) and proceed to testing if there are sex effects in total cerebellar grey matter using linear regression, my results show that cerebellar volume is much larger in females than males when using the sum of the available FAST grey matter cerebellar volumes, and when I use the sum of the cerebellar cortex volumes provided by ASEG it appears that males have a much larger cerebellar cortex than females.