The technology is really cool, as are some of the physics if you're into that kinda stuff. I'd ask about which machines or treatment modalities they use and why they use it. Mets in the brain stem? Do they use whole brain RT or are they small enough they can use sterotactic surgery. What is their relation with the medical oncologists and surgeons? Do they run clinical trials or have active research projects going on, etc.
It's Rad Onc btw.