A gamma knife is a piece of equipment used in noninvasive neurosurgery. Despite the name, a gamma knife isn't a knife at all. Instead, it delivers radiation to a precisely targeted point inside the brain with the goal of disrupting an abnormality such as a tumor or arteriovenous malformation (AVM). Gamma knife surgery has also been used to treat certain pain and seizure conditions by removing areas of the brain which are functioning abnormally.
This equipment is used in a technique known as stereotactic radiosurgery. The gamma knife is capable of delivering over 200 beams of radiation which can be brought to focus on one point. A single beam does not cause radiation damage, but the area in which the beams converge is characterized by very high radiation which can damage cells, such as the cells which make up a tumor. In stereotactic radiosurgery, concentrated radiation is used to target one area while leaving the rest of the brain intact. Noninvasive surgical techniques greatly reduce the risk of complications such as infections.
The gamma knife was developed in the 1960s by Swedish physicians, and is utilized all over the world today. When patients receive treatment with this piece of equipment, they are first fitted with a head frame which is screwed to the skull. Then, the brain is imaged using medical imaging techniques. This data is fed into a computer and used for calculations which determine where the beams of radiation should converge, and how much radiation should be delivered. This can take several hours, during which the patient may rest in another area.
Next, the patient is positioned inside the machine. The head frame is used to hold the head perfectly still, and to create a frame of reference to ensure that the radiation is delivered to precisely the right spot. It may require only a single dose for the treatment with the gamma knife to be complete, and the treatment is painless and silent. Many patients can go home on the same day and begin follow up care for the condition which brought them into the neurosurgery suite.
The biggest risk of gamma knife surgery is swelling of the brain, which can be treated with medications to prevent inflammation. It can take weeks for the radiation to do its work, as the damaged cells will fail to propagate, allowing the area of abnormality to shrink. Patients who receive stereotactic radiosurgery are usually directed to attend a series of follow-up appointments which can be used to determine whether or not the surgery was effective, and which additional steps need to be taken, if any, for treatment to be successful.