What is a Gamma Knife?

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  • Written By: Mary McMahon
  • Edited By: O. Wallace
  • Last Modified Date: 16 October 2019
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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.


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Post 2

People may scream about "allopathic medicine," but good grief, modern medicine can do wonderful things! It's amazing what doctors and surgeons can do now, as opposed to just 20 years ago! It's truly amazing how far technology has progressed. This is stuff Jules Verne never dreamed of.

The whole process of mapping and imaging the brain is so detailed. I know there are many people who cringe at the thought of zapping the brain with a radiation beam, but if I were in that position and I knew it could eradicate a brain tumor, I'd be yelling, "Zap me! Zap me now!"

Post 1

I had kind of a hazy knowledge of how the gamma knife worked, but this makes it much clearer. For some reason, I thought it was actual surgery, not noninvasive. But even having a frame screwed to your head is better than having brain surgery.

Seems like I first remember hearing about the gamma knife in the mid-80s, but it sounded like something out of a science fiction movie. It's almost routine nowadays, inasmuch as anything like that could be routine. I know it has helped many, many people who had tumors previously thought inoperable live longer, better lives.

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