Radiosurgery with Gamma Knife or CyberKnife is a special form of radiation therapy. Since it is a high-precision radiation method, it is technically very complex. Many beams from different directions cross each other exactly within the target area, i.e. the previously precisely localized tumor. For this purpose, corresponding high-resolution MRI and CCT images are mandatory. By this means, a very high radiation dose can be achieved in the tumor area, while the still unfocused individual beams protect the surrounding healthy tissue. Since the high radiation dose is generated only where the beams cross, the tumor can be irradiated with submillimeter precision. Therefore, general anesthesia is not required for radiosurgical treatments.