Gamma Knife radiosurgery is a type of radiotherapy treatment. It’s also called stereotactic radiosurgery. Even though it’s called surgery, a Gamma Knife procedure does not use surgery. It also isn’t a knife. Gamma Knife uses very precise beams of gamma rays to treat an area of disease (lesion) or growth (tumor). It’s most often used in the brain. The beams of gamma radiation send a very intense dose of radiation to a small area without a need to make an incision. Radiosurgery destroys cells so that they can’t grow. A lesion or tumor will shrink in size over time.
Gamma Knife radiosurgery is called surgery because the end result is similar to removing a lesion with surgery. The beams of radiation are precisely focused to reach the lesion, with little effect on nearby healthy tissue. The Gamma Knife system is just one type of radiosurgery system. Gamma Knife is a brand name.
A Gamma Knife procedure is done by a treatment team. The team is led by a radiation oncologist. This is a specialist in radiation treatment for cancer. The other team members may include:
A radiation therapist
A registered nurse
A medical physicist
Other healthcare providers as needed
Gamma Knife treatment in most cases involves these steps:
Head frame placement. To keep the head from moving during treatment, a box-shaped frame is attached to the head. Pins designed for this purpose fasten the head frame to the skull. The head frame is also a guide to focus the gamma ray beams to the exact location of the lesion.
Tumor or lesion location imaging. Once the head frame is in place, the exact location of the lesion will be found using a CT scan or MRI. A CT scan uses a series of X-rays and a computer to create a detailed image. MRI uses large magnets and a computer to make images. You may need a cerebral angiogram if a blood vessel lesion such as arteriovenous malformation (AVM) is being treated. A cerebral angiogram uses X-rays and a special dye. The dye is injected into a large blood vessel to find problems in the blood vessels.
Radiation dose planning. After the CT or MRI scan, the radiation therapy team will determine the treatment plan. The results of the imaging scan and other information will be used by a medical physicist to determine the best treatment.
Radiation treatment. After the person is positioned for the treatment, a type of helmet with hundreds of holes in its placed over the head frame. These holes help to focus the radiation beams on the target. Treatment will last a few minutes up to a few hours. The length of time depends on the type and location of the area being treated. In most cases, only one treatment session is needed for a lesion.
Gamma Knife radiosurgery is most often used to treat:
Small and medium tumors and lesions in the brain
Trigeminal neuralgia, when pressure on the trigeminal nerve causes spasms of extreme facial pain
Acoustic neuroma, a noncancerous tumor in the brain that affects nerves that control hearing
Blood vessel lesions such as arteriovenous malformation (AVM)
Your healthcare provider may have other reasons to advise Gamma Knife radiosurgery. Gamma Knife radiosurgery may be used when a brain lesion can’t be reached by standard surgery. Or it may be used when a person can’t have standard surgery, such as craniotomy. The effects of a Gamma Knife treatment occur slowly over time. Because of this, it’s not for people who need immediate effects. Talk with your healthcare provider about the reason for your procedure.
All procedures have some risks. The risks of this procedure may include:
Swelling of the brain
Nausea and vomiting
Hair loss near treated area (temporary)
Soreness and swelling in the area being treated
Loss of balance
Pain at the head frame pin insertion sites
If you are pregnant or suspect that you could be, tell your healthcare provider. Radiation exposure in pregnancy may lead to birth defects.
Your risks may vary depending on your general health and other factors. Ask your healthcare provider which risks apply most to you. Talk with him or her about any concerns you have.
Your healthcare provider will explain the procedure to you. Ask him or her any questions you have. You may be asked to sign a consent form that gives permission to do the procedure. Read the form carefully. Ask questions if anything is not clear.
Tell your healthcare provider if you:
Are pregnant or think you may be pregnant
Are allergic to contrast dye or iodine
Are sensitive to or allergic to any medicines, latex, tape, or anesthetic medicines (local and general)
Take any medicines, including prescriptions, over-the-counter medicines, vitamins, and herbal supplements
Have had a bleeding disorder
Take blood-thinning medicine (anticoagulant), aspirin, or other medicines that affect blood clotting
Have any type of implant, such as a pacemaker, implantable defibrillator, artificial heart valve, surgical clips for a brain aneurysm, implanted medicines pump, chemotherapy port, nerve stimulators, eye or ear implants, stents, coils, or filters
Make sure to:
Stop taking certain medicines before the procedure, if instructed by your healthcare provider
Not eat or drink for 8 hours before the procedure, or as instructed by your healthcare provider
Wash your hair with special shampoo the night before or morning of the procedure, if instructed
Plan to have someone drive you home after the procedure
Follow any other instructions your healthcare provider gives you
You may have blood tests, urine tests, or other tests or exams before the procedure. Your healthcare provider will tell you more.
You may have your procedure as an outpatient. This means you go home the same day. Or it may be done as part of a longer stay in the hospital. The way the procedure is done may vary. It depends on your condition and your healthcare provider's methods. In most cases, the procedure will follow this process:
You may be asked to remove your clothes. If so, you will be given a hospital gown to wear. You may be asked to remove jewelry or other objects.
An intravenous (IV) line may be put into your arm or hand.
Hair in the area around the head frame insertion sites may be trimmed. The skin on your head will be cleaned where the pins for the head frame will be placed.
A numbing medicine (local anesthetic) will be injected at the head frame pin insertion sites. The head frame will be attached to your head with pins that are inserted into your skull. You may feel some pressure during the placement of the head frame. This feeling should go away in a few minutes.
After the head frame is attached, you will undergo brain imaging. This is done so that the location of the brain tumor or lesion can be precisely found for the treatment. The brain imaging may be done with a CT scan. Or it may be done with an MRI. After the brain imaging, the team will use the images to create your treatment plan. In some cases, the imaging may be done before the day of your radiosurgery.
You will be taken into the room where the Gamma Knife equipment is located. You will lie down on a sliding table. A special helmet called a collimator helmet may be fitted over the head frame. The collimator helmet has 201 holes in it. These holes allow radiation beams to pass through it into your brain in a precise pattern that is determined by a computer.
Once the helmet is in place, the table will slide into the Gamma Knife unit. You may hear a clicking sound as the helmet moves into place in the machine.
The treatment team will go into another room. You can talk with the team through an intercom. They can hear you at all times. You will be watched on a video monitor.
You will not feel or hear anything from the Gamma Knife unit during the treatment session.
The treatment session may last from 2 to 4 hours. The length of the session will depend on the treatment plan created for you.
After the session is over, the table will slide out of the Gamma Knife machine. You will be able to get up, unless you had an angiogram before the Gamma Knife procedure.
The head frame will be removed. The pin insertion sites will be cleaned. Sterile dressings will be put on the sites.
After the procedure, you will be watched for a period of time.
Once you are able to drink, the IV line will be removed. You may eat and drink as you are able. You may feel some discomfort after the procedure, such as a headache or nausea. Tell your healthcare provider so you can be treated for these effects.
You will most likely go home at the end of the day. You will need to have someone drive you home. If needed, you may stay in the hospital overnight. Once you’re home, you may go back to your normal diet, medicines, and activities, unless your healthcare provider tells you differently. You may be told to avoid strenuous activity for a period of time.
You will most likely be allowed to gently shampoo your hair the day after the procedure. But, don't scrub the pin sites on your head until they have completed healed. Healing usually takes about a week.
Call your healthcare provider if you have any of the below:
Severe headache that’s not relieved by pain medicine
Any weakness, numbness, or vision problems that are new or worse
Bleeding or other fluid leaking from the pin sites that doesn’t stop
Your healthcare provider may give you other instructions after the procedure.
Before you agree to the test or the procedure make sure you know:
The name of the test or procedure
The reason you are having the test or procedure
What results to expect and what they mean
The risks and benefits of the test or procedure
What the possible side effects or complications are
When and where you are to have the test or procedure
Who will do the test or procedure and what that person’s qualifications are
What would happen if you did not have the test or procedure
Any alternative tests or procedures to think about
When and how you will get the results
Who to call after the test or procedure if you have questions or problems
How much you will have to pay for the test or procedure