
Gamma knife radiosurgery involves the application of high single doses of radiation to targets in the brain or nearby structures, using 201 cobalt sources arrayed in a roughly hemispherical fashion and focused on a small central point. Because of highly skilled engineering and manufacturing, the treatment accuracy of the machine is about 1/2 millimeter, about the width of a human hair. This sort of accuracy, unavailable with other types of treatment, allows delivery of high doses of radiation to tumors and other targets despite the presence of nearby sensitive structures, such as optic nerves, brainstem etc.
