In an age when technology is advancing faster than man is capable of adapting to it, it is refreshing to come across a relatively old technology, by today's standards, that is gaining momentum in the never-ending fight against cancer: the gamma knife. The gamma knife was the first radiosurgical instrument, operated in Sweden in 1968. Lars Leksell, a Swedish neurosurgeon, developed the concept in 1951. Today it is one of the most precise radiosurgical devices physicians are using to battle cancer tumors in the brain once thought to be inoperable.

Figure 1. Gamma knife unit

With fewer than 50 gamma knife centers located throughout the United States, the gamma knife still represents an attractive addition to many nuclear medicine programs. With new facilities being planned, the following paper will attempt to address some of the architectural and planning issues that must be resolved in the development of these facilities and give a recent gamma knife center project as a successful case study.

The Process
The gamma knife is a stereotactic radiosurgical device used in the treatment of brain tumors and arteriovenous malformations, as well as to relieve pain associated with trigeminal neuralgia. It enables very precise surgical changes to be made within the brain without the risks of conventional surgery or radiation therapy. It works by delivering, in a single treatment session, 201 beams of cobalt-60 radiation to a single, focused point on the targeted brain lesion. This causes distortion of the DNA mapping of the cells, destroying their ability to replicate. Each individual beam of the gamma radiation is relatively harmless to the surrounding tissue it passes through. It is only where the beams focus that a high dose of radiation is achieved to destroy targeted cells. Gamma knife treatment takes effect immediately and is believed to be as effective as conventional neurosurgery for some cases, and more effective in others, making gamma knife radiosurgery a very attractive alternative to conventional neurosurgical treatments.

Treatment is planned and administered by a staff specially trained in the use and limitations of the gamma knife unit. The treatment team typically includes a neurosurgeon, a radiation oncologist, a medical physicist, a registered nurse, and a radiation therapist.

A typical patient day consists of the patient arriving and having the frame applied to his or her head. Once the frame is attached, the patient is sent to imaging, where an MRI, CT scan, or angiography may be administered depending on the illness. The target is localized and its x, y, and z coordinates determined relative to the frame. The IMAGES are transferred directly to dosimetry, where the patient's treatment is planned. Once the treatment is planned, the patient is laid on the couch of the gamma knife unit. Treatment lasts from 15 minutes to several hours depending on the complexity of the treatment plan and the number of doses required. When the treatment is complete, the frame is removed and the patient discharged. The whole process may take as little as five or six hours.