Gamma Knife Radiosurgery.

The concept of radiosurgery and its requirements are presented. Dedicated radiosurgical tools include the modified linear accelerators working with a single rotating beam and the Gamma Knife with multiple stationary radiation sources. The 201 gamma beams from the cobalt 60 sources of the Gamma Knife intersect within 0.3 mm and it is possible to align the selected target point with the focal point within a mechanical accuracy of 0.5 mm. The technical specifications of the Gamma Knife make it possible to safely produce sharply circumscribed lesions in a single session with superior accuracy and precision. Gamma Knife surgery is a four-step neurosurgical procedure including application of a stereotactic frame to the patient's head, stereotactic image acquisition, treatment planning, and the radiation. The system allows stereotactic acquisition of images from computed tomography, magnetic resonance tomography, cerebral angiography, and positron-emission tomography. Applications for Gamma Knife surgery include the treatment of cerebral vascular malformations, well-delineated benign and malignant tumors of the head, the treatment of certain pain conditions such as trigeminal neuralgia, as well as the treatment of some movement and psychiatric disorders. The results of treating arteriovenous malformations, acoustic neurinomas, and cerebral metastases are particularly outstanding.