Have a google for Cyber Knife. One has been installed at Mount Vernon Hospital, was a gift from a grateful patient ( £10,000,000). Destroys tumors that are inoperable. Hope for those who had none.
The CNC bit allows the beam to be rotated around and converge on the target without the operators being anywhere near. It is a step up from the linear accelerator technology that has been used for mostly one axis rotation.
Billy.