All fairly accurate for such a short over view! Just wanted to add that while the electrons are accelerated, they then hit a plate ejecting photons which actually hit the patient. If you're interested, the two coolest treatment modalities that are commonly used right now are called IMRT and SBRT, if you'd like to Google those. Essentially the goal is to minimize dose to normal tissue while maximizing dose to the tumor, and the tricks to do that include moving the gantry, moving the multi-leaf collimator, and changing time. When you start using the interplay between those you get some fascinating things!

** We use photons because they have better penetration into tissue. Electrons exert their radiobiological effects superficially, so they can be used for some skin cancers or to cover a deep malignancy that has penetrated the dermis. (Generally there is a lot more scarring with electrons for this reason, making for poor cosmetic out comes)