Over the years radiation targeting has become more precise. It is now possible to manipulate (or modulate) the radiation beam so that the high dose region conforms to the shape of the tumor (called conformal therapy.) With three dimensional imaging (CAT and MRI scans) it became possible to target the tumor in a 3 dimensional coordinate system (called stereotactic system) allowing the delivery of a high dose of radiation very precisely to a small a target.
If stereotactic targeting is used to deliver radiation over several weeks it is referred to as stereotactic radiotherapy. If a stereotactic system is used to deliver the radiation in a single high dose (up to 3 to 5 treatments) it is called radiosurgery because this technique will destroy or ablate the tumor as effectively as surgically removing the tumor.
The best techniques include a static framed based system (see Gamma Knife) which is restricted to the brain or even better Dynamic Real Time Body Radiosurgery (see Cyberknife) which does not require attaching a frame to the head and can treat anywhere in the body