I'm interested in measuring cerebellar volumes using freesurfer. However, the automatic segmentation (aseg) seems to be doing a poor job of capturing the whole structure for many subjects. Specifically, it is chopping off the bottom of the cerebellum. Here is an example:

The issue seems to be when the cerebellum is very close to the bottom of the image, as is the case in many of our scans. Has anyone encountered similar issues with cerebellum segmentation, and if so, have any advice about how to improve it?

Many thanks,