What would a neurologist refer patients for positron emission tomography scans for?

Pet indications: Pet is good to show in vivo abnormal functional areas--it has limitations--it would be nice if cheaper, more available and the pictures come superimposed on MRI pictures---may benefit us in dementia--separate radiation necrosis from active brain tumour--separate infectious from degenerative area.

A couple things: I order these for atypical dementia presentations (brain pet) and cancer (whole body pet).