What is Gamma Knife?
Gamma Knife radiosurgery is an established stereotactic radiosurgery (SRS) technique for tumours, vascular malformations, and other abnormalities of the brain. The Gamma Knife is a radiation therapy machine which can deliver large doses of precisely targeted radiation, minimising radiation to the surrounding healthy brain reducing the risk of damage.1
How does Gamma Knife work?
Gamma Knife radiosurgery delivers multiple converging beams of gamma radiation toward a central point to deliver high dose radiation to a specific target within the brain and, avoid delivering significant doses to normal brain tissue.1
Who is eligible for Gamma Knife radiosurgery?
Gamma Knife radiosurgery is used to treat a variety of brain disorders. Your treatment team are neurosurgeons and radiation oncologists, radiation therapists, physicists and nurses with specialised training in the treatment of neurological conditions, as well as other healthcare professionals.
The team will work together to decide if this is an appropriate treatment option for you after careful evaluation of your condition, ensuring you are eligible based on all clinical circumstances.
Eligible conditions may include (but are not limited to):
- Brain metastases
- Pituitary adenomas
- Acoustic neuromas
- Arterial venous malformations
- Trigeminal neuralgias
Gamma Knife may not be suitable if:
- The treatment area is too large
- The lesion that needs treatment is too close to important critical structures in the brain .
Benefits and risks of Gamma Knife
- Gamma Knife enables the treatment of hard-to-reach brain tumours that may not be easily treated with conventional surgery.
- SRS may have benefits over conventional whole-brain radiation therapy. By limiting radiation to the surrounding healthy brain tissue, SRS aims to reduce immediate and late side-effects, and thereby offer a better quality-of-life.2
- You should be aware that radiosurgery is a serious medical treatment and comes with risks and side effects which should be discussed with your doctor. Studies have shown that Gamma Knife treatment may result in fewer side effects than conventional radiotherapy.
Possible side effects
Side effects may vary between patients and your doctors will advise of which side effects to expect.
Not everyone experiences side effects, but your risk may be affected by your general health, other treatments you’ve had and the targets to be treated.
These usually disappear within two to four weeks of treatment:3
- Pin site tenderness or minor bleeding
- Nausea and/or vomiting
- Seizures (fits)*
- Temporary worsening of your symptoms
Around 10% of people notice side effects months, or even years, after SRS. These are related to the treatment area within the brain and may include:3
- Local hair loss
- Neurological damage
- Memory loss, or cognitive changes
- Radiation damage to the normal brain
- Secondary cancer years later, though this is rare
It’s important that you attend your follow-up visits and scans so any issues can be identified and treated as soon as possible.
What happens during Gamma Knife radiosurgery?
If you choose to have Gamma Knife radiosurgery after consultation with your doctor, the following process is likely to apply with respect to Gamma Knife radiosurgery, planning and treatment.
On arrival at the centre you will meet your treatment team, go through an orientation of the clinic floor and complete your health and nursing assessment.
Fitting your head frame
You’ll be fitted with a head frame to improve the accuracy of your radiosurgery and keep your head still during treatment. The frame will be fitted on the same day as your treatment.
Head frame fitting
Your consultant will inject local anaesthetic into four places on your head. Once the areas are numb, they’ll attach the frame to your head with four screws. It takes around 15 minutes to fit, and you’ll keep it on until your treatment has finished. You may feel pressure, but once the frame is fitted this will disappear within 15-20 minutes. You may also feel some discomfort where the frame was attached to your head after your treatment has finished and the local anaesthetic has worn off, which usually only requires mild analgesia.
Ahead of Gamma Knife radiosurgery, you’ll need an MRI scan – this helps your treatment team accurately direct the radiation beam during treatment and set the optimum dose according to your tumour’s position, size, and shape.
Before your MRI, you’ll be injected with a special dye called a contrast agent, which helps show certain structures on the more clearly on the scan.
Most patients will have an MRI on the day after the frame fitting, however some may have the MRI ahead of the frame fitting.
You will also need a CT scan, with the head frame on.
Your treatment team will then use the information from the scans to plan your treatment. This can take from 30 minutes to a few hours. While you’re waiting, you’ll be given something light to eat and drink, and you can watch TV, read, or chat with a friend or relative. You will keep your head frame on during this time.
After planning, a member of your treatment team will take you to the Gamma Knife treatment room. You’ll be helped into position on the treatment couch and your head will be held in place with your head frame.
When you’re ready, your treatment team will leave the room, but you’ll still be able to talk to them throughout the treatment via an intercom. The bed will move inside the Gamma Knife machine through an open door and treatment will begin. The bed will move position throughout treatment depending on how many shots have been used in the plan. You will probably not even notice as the movements are so slight.
You won’t be able to feel the treatment and the treatment time will vary according to the size, location and number of target areas to be treated.
When the treatment has finished, your treatment team will come back into the room and help you off the couch. The head frame will be removed and you will return to your room for a short period of observation before you will be ready to go home.
You may experience some mild scalp tenderness in the days following the procedure which can be managed with simple analgesia and guidance from your treatment team.
Depending on the indication for which you are being treated, our doctors will determine your follow up schedule which may include a follow-up MRI. A member of your treatment team will call to check on you within a week following your treatment.
- Desai R and Rich K. Mo Med 2020; 117(1):33-38.
- Brown P, et al. JAMA 2016; 316(4):401-409.
- Yamamoto M, et al. Lancet Onc 2014; 15(4):387-395.
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