Gamma knife

Published by Bupa's Health Information Team, September 2011.

This factsheet is for people who are having gamma knife treatment, or who would like information about it.

Gamma knife uses highly focused beams of radiation to treat many conditions including brain tumours and trigeminal neuralgia. It's a non-surgical treatment and is usually given as a single dose.

You will meet the doctor carrying out your procedure to discuss your care. It may differ from what is described here as it will be designed to meet your individual needs.

About gamma knife

Gamma knife is a non-invasive procedure. The aim of the treatment is to deliver a high dose of radiation to a very small area of the brain, which prevents damage to the surrounding healthy brain tissue, nerves and blood vessels. It can be used as an alternative to open surgery.

Gamma knife can treat a number of different conditions including:

  • benign, malignant or metastatic brain tumours
  • vascular malformations – this is when some of your arteries and veins in your brain are connected in ways they would not usually be
  • other disorders such as trigeminal neuralgia and Parkinson’s disease

The procedure isn't suitable for tumours larger than 4 to 5cm.

What are the alternatives to gamma knife?

Depending on your condition, it may be possible to have open surgery, radiotherapy or another form of radiosurgery such as Cyberknife. Your doctor will explain your options to you.

Preparing for gamma knife

You may need to stay overnight in hospital if you have gamma knife treatment. However, some gamma knife treatments are carried out as a day-case or as a two-night stay in hospital. Your doctor will let you know how long you will need to stay. You will stay awake during the whole gamma knife procedure but you will be given a local anaesthetic to completely block any pain from the areas where the head frame is attached. This head frame is called a stereotactic frame and it's used to pinpoint the area to be treated by the gamma knife.

You may be asked to follow fasting instructions. This means not eating or drinking, typically for about four hours beforehand. However, it’s important to follow your doctor’s advice.

You will be asked to remove all make-up (including nail polish), hairpieces, contact lenses, glasses and dentures.

At the hospital, your nurse may check your heart rate, blood pressure, temperature and weight.

Your doctor will discuss with you what will happen before, during and after your procedure, and any pain you might have. This is your opportunity to understand what will happen, and you can help yourself by preparing questions to ask about the risks, benefits and any alternatives to the procedure. This will help you to be informed, so you can give your consent for the procedure to go ahead, which you may be asked to do by signing a consent form.

There are a number of different steps involved in preparing for gamma knife treatment. These are explained here. 

Frame fitting

You will be taken down to the gamma knife unit. You will need to have a light-weight frame fitted to your head. Your doctor will inject local anaesthetic at four sites on your head where the frame will be fixed with pins. This process can be slightly painful but the pain shouldn't last long. The fitting can take between 15 and 20 minutes. The frame will stay attached to your head for the whole treatment.


You will have an MRI (magnetic resonance imaging) scan to find the exact position of the area that needs to be treated. An MRI scan uses magnets and radiowaves to produce images of the inside of the body. You may also have a cerebral angiogram (an X-ray image of the blood vessels in your head and neck) if the treatment is for a vascular malformation. Occasionally, your doctor will recommend a CT (computerised tomography) scan. A CT scan uses X-rays to make a three-dimensional image of part of the body. The images will be transferred to a computer that will work out what dose of radiation you need.

Dose planning

Once the imaging stage is finished, you will either be taken back to your room (wearing the head frame) or stay in the gamma knife department. The images taken by CT, MRI or angiography will be fed into a computer that calculates the exact treatment time. A team of people including a neuroradiologist (a doctor who specialises in using imaging methods to diagnose medical conditions of the nervous system) will map out the area to be treated and prescribe the exact dose. It may take several hours to plan your treatment.

What happens during gamma knife

You will lie on the treatment couch and the radiographers will position the frame attached to your head either into a docking device on the couch or a helmet, depending on the type of gamma knife unit. This is important because it will keep your head still during the procedure. Once your head has been positioned and the relevant checks have been completed, the radiographers will leave the treatment room. You can speak to the radiographers at any time during the procedure via a microphone. They are able to see you at all times from the control room by cameras positioned in the treatment room.

A radiographer preparing a man for gamma knife treatment, with the man lying on the treatment table.

                                                         Gamma knife

A radiographer operating the gamma knife machine from the control room.

                                                    Gamma knife control room

When the treatment begins, the door of the gamma knife unit will open and the couch will move you into the gamma knife unit as far as your waist. The radiation is made up of hundreds of different beams from different angles that cross at the targeted area. The radiation treatment will be made up of a series of exposures (shots) and you will be moved from one to the next shot position. You may be moved manually by the radiographers or automatically by the gamma knife unit, depending on the unit being used. The exposure of each shot may only take a few minutes but the entire procedure can last several hours. You won't feel any pain during the treatment. 

Once the treatment has finished your doctor will remove the head frame. You may notice slight bleeding around the area where the frame was placed and it may feel sensitive for several days.

What to expect afterwards

After your treatment you will be taken back to your room where you can rest. If you have a headache or feel sick, the nurse can give you medication.

You may need to arrange for someone to drive you home depending on how you are feeling. Try to have a friend or relative stay with you for the first 24 hours.

After your treatment, your doctor will arrange a follow-up appointment to check how you're recovering and what your response has been to the treatment. You may also have an MRI scan in the follow-up appointment. 

Recovering from gamma knife

If your head is painful where the head frame was attached, you can take painkillers. Always read the patient information leaflet that comes with your medicine and if you have any questions, ask your pharmacist for advice.

If you notice pain, swelling or redness, or have any concerns following your treatment, contact your doctor.

The successful outcome of your treatment will depend on why you needed to have gamma knife carried out. You may not see immediate results and some medical conditions require monitoring over many years.

What are the risks?

As with every procedure, there are some risks associated with gamma knife. We have not included the chance of these happening as they are specific to you and differ for every person. Ask your doctor to explain how these risks apply to you.


These are the unwanted but mostly temporary effects you may get after having the treatment.

Gamma knife treatment usually has few side-effects because it only targets the affected area.

When your doctor takes the head frame off, you may have slight bleeding from the points where it was held in place. Rarely, you may feel sick or have a headache but this shouldn't last for more than four hours. 


This is when problems occur during or after the procedure. Any complications that may arise are specific to you and your condition. Your doctor will have discussed these with you prior to the gamma knife treatment. 

If the target area is large, or requires a high dose of radiation, you may have temporary swelling of the surrounding areas. This can cause a small number of people to have side-effects that could include having a fit. This is very rare and can be treated with steroids or surgery.


For answers to frequently asked questions on this topic, see FAQs.

For sources and links to further information, see Resources.

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  • This information was published by Bupa's Health Information Team and is based on reputable sources of medical evidence. It has been reviewed by appropriate medical or clinical professionals. Photos are only for illustrative purposes and do not reflect every presentation of a condition. The content is intended only for general information and does not replace the need for personal advice from a qualified health professional. For more details on how we produce our content and its sources, visit the about our health information page.

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  • Publication date: September 2011