Stereotactic radiation is used in the treatment of acoustic neuromas and skull base tumors. This procedure may also be called radiosurgery. It involves radiating a tumor from several different directions in such a way that the tumor receives the concentrated dose of radiation while the rest of the brain is somewhat protected.
Stereotactic radiation is particularly indicated for patients over age 65 who have tumors that are less than 3 cm. It is also appropriate for patients who have underlying medical conditions, like heart disease, that make traditional surgery riskier. The procedure can also be used for younger patients if their condition warrants.
There are three techniques that can be used to deliver radiation to a tumor in radiosurgery: the linear accelerator, the GammaKnife and the CyberKnife. The linear accelerator is an older method that is not commonly used today.
Radiosurgery Using the CyberKnife
The CyberKnife system is used to treat acoustic neuromas. The robotic arm of this device is able to deliver very precisely focused radiation directly to the tumor. Not only does this increase the effectiveness of the radiation, but the narrow focus keeps adjacent areas of the brain from also being irradiated.
CyberKnife treatments are usually performed as outpatient procedures. They require no anesthesia, as the robotic arm will never touch the patient, and the radiation does not cause pain. Patients will lie on the treatment table while the arm moves around them. The patient may need from one to five treatments to achieve the desired results, with each treatment lasting from 60 to 90 minutes.
People who receive stereotactic radiation using the CyberKnife system often experience a very rapid relief from pain. There are rarely complications, and patients typically recover quickly from the procedure.
Radiosurgery Using the GammaKnife
The GammaKnife differs from the CyberKnife in that the device comes in contact with the patient’s body. This requires that the patient receive local anesthesia. A headframe through which radiation is delivered is placed on the patient’s head and secured with four screws. The headframe is able to administer radiation through 201 sources.
Once the patient is attached to the GammaKnife device, an MRI scan tells it exactly where the tumor is located. The radiation is directed by computer as the device delivers targeted radiation in three dimensions. Like the CyberKnife, the GammaKnife allows for very precise targeting of the tumor and little bleeding over of radiation to other areas of the brain.
Fractionated Stereotactic Radiotherapy
Fractionated stereotactic radiotherapy is particularly suited for tumors at the base of the skull. It can be performed with either a CyberKnife or a GammaKnife device. “Fractionated” refers to the fact that this technique uses multiple small doses of radiation rather than one larger dose.
The fractionated procedure has the advantage of being less likely to damage the facial and the trigeminal nerves, both of which enervate the face. It is also more likely to preserve the hearing of patients than single-dose radiosurgery. Fractionated stereotactic radiotherapy is most suited for tumors that are smaller than 3 cm, and it may require three to five doses.