Physics and dosimetry of the gamma knife.

Since 1968, the gamma knife has been one of the major radiosurgical devices. Although approximately 4300 patients worldwide had been treated with the gamma knife units through June 1990, gamma knife installments in the United States are still rather scarce compared to linear accelerators adapted for radiosurgery. This article describes the basic physical characteristics of the gamma knife, patient set-up procedures, the existing treatment-planning system, the measurements of dosimetry and physical parameters, dose delivery accuracy, and quality assurance procedures. It also includes a vision of future developments and improvements in these areas.