Gamma knife is a stereotactic radiosurgery technique, a form of radiation therapy, in which low-dose radiation beams are focused directly and precisely at the brain tumor. This makes it possible to deliver a high dose of radiation, converging from a different direction to the center of the tumor. It is a non-invasive radiation treatment that does not involve scalpel or incision – it does not actually involve a knife. Gamma Knife radiosurgery method uses 192 beams of gamma radiation that are precisely focused on the abnormal tissue in the brain. It is an alternative to conventional open brain surgery for the treatment of brain tumors and other conditions of the brain.
Gamma Knife involves the use of three-dimensional imaging software to accurately locate and target the tumor in the brain before delivering the radiation. The MRIs (magnetic resonance imaging scans) and CT (computed tomography) scans are analyzed by a team of radiation oncologists and neurosurgeons prior to the treatment to plan radiation therapy.
It is a common myth amongst patients that Gamma Knife is an expensive procedure. When in reality, the overall Gamma Knife surgery cost sums up to be lower than that for traditional surgery. This is because, with Gamma Knife surgery, general anesthesia and hospitalization are not required, as it is with open surgery. This helps save the cost associated with these and most patients only need a single session.
What can be treated with Gamma Knife?
Gamma knife radiation therapy can be used to treat various kinds of abnormalities in the brain. This includes certain malignant tumors primary brain tumors or metastatic tumors (that arise in or spread to the brain), benign brain tumors such as meningiomas, pituitary adenomas, acoustic neuromas, and vascular defects such as arteriovenous malformations and functional problems such as trigeminal neuralgia. The technique is being studied for use in the treatment of other brain conditions such as epilepsy.
This radiosurgery technique is particularly effective for patients whose brain tumors are:
- The diameter of three centimeters or less
- Benign or malignant (cancerous)
What is the procedure?
- Gamma Knife treatment is typically given in a single session on an outpatient basis. This means patients arrive in the morning and can return home later on the same day. Sometimes, the doctor may deliver radiation treatment over a few days.
- The patient is given local anesthesia on the head. A special rigid head frame is put on the patient’s skull with four screws. This frame helps hold the patient’s head in a particular manner for imaging and treatment.
- Imaging tests, such as magnetic resonance imaging (MRI) and computed tomography (CT) are taken by the team of doctors to locate and assess the tumor.
- Using these images, the Gamma Knife planning computer system designs the treatment plan for the patient.
- A team of doctor including radiation oncologists and neurosurgeons along with other medical professionals analyses the report to determine the exact spatial relationship between the target and normal structures. The planning system is also used to calculate Gamma Knife treatment parameters such as radiation dosage.
- After the three-dimensional coordinates from the planning system are determined, the head frame is precisely attached to the Gamma Knife unit. This is to ensure that when the unit gets activated for treatment, the target is exactly in the center of the precisely aimed and converging beams of gamma radiation (generated by Cobalt-60).
- During the treatment session, patients are treated with combinations of many successive highly focused radiations, known as shots.
- Depending on the complexity (shape and size), the dose required and a number of lesions/tumors to be targeted, the treatment session takes several minutes to a few hours to complete.
- The patient will not feel the radiation treatment or pain during radiation delivery. However, some patients have reported seeing flashes of light during the treatment when radiation is delivered.
- After the treatment, the head frame is removed and the patient is kept in a post-anesthesia observation unit for some time.
- Most patients are able to return to normal activity after this.
Advantages of Gamma Knife Surgery
It is a non-invaisve method and does not require an incision. Gamma knife surgery is actually not a surgical procedure but a type of radiation therapy. The patient does not need general anesthesia and therefore does not pose the risks associated with surgical incisions and general anesthesia.
Highly accurate method – As a gamma knife precisely targets the brain tumor, it prevents the areas surrounding the tumor from getting exposed to radiation.
The risk of side effects and damage to nerves as well as a blood vessel in the brain is less.
Administered in one treatment session. It takes 15 to 60 minutes on an average to deliver radiation with the gamma knife method.
It is an effective treatment for certain malignant brain tumors and has been reported to improve quality of life and increase a patients’ lifespan.
Risks of Gamma Knife Surgery
As with every medical procedure, there are some risks and side effects associated with gamma knife surgery, such as :
- Nausea, vomiting or dizziness
- Hair loss in the radiation is directed
- The area where screws or pins were placed remains tender
- Damage to nearby brain tissues caused due to swelling. These may be a delayed effect and may cause symptoms similar to a stroke or a recurrence of the tumor