What does the cyberknife do and how precise is it?

Robotic Radiosurgery: Cyberknife is designed to kill tumors anywhere in the body with high-dose, highly-focused radiation in a procedure called radiosurgery. A robot arm aims many radiation beams at the tumor. Using special image tracking it can stay focused on a tumor even if the tumor moves with breathing or other patient motion. Cyberknife can sometimes target tumors with sub-millimeter precision.