Stereotactic Radiosurgery: Dr. Michael Brisman
Stereotactic radiosurgery has revolutionized the treatment of many conditions. Stereotactic radiosurgery is highly focused so that surrounding tissue as close as several millimeters away from the target receives hardly any radiation. This is an outpatient procedure done in one to five sessions at high doses to a very small area. This is in contrast to conventional external beam therapy, which takes many sessions, is delivered at low doses, and covers a wide area, including normal tissue. Stereotactic radiosurgery can be used to alter any type of cell, not just malignant tumor cells as in conventional radiation therapy. In stereotactic radiosurgery, the beams are delivered from multiple angles and converge on the target. If necessary, the procedure can usually be repeated, especially if a significant amount of time has passed between treatments.
History of Stereotactic Radiosurgery
The Gamma Knife machine, the original and one of the major machines used in stereotactic radiosurgery, was invented in Sweden in the 1950s. The Gamma Knife uses a cobalt source to deliver gamma rays. Another major type of machine, called a linear accelerator, was adapted from standard radiation therapy.
Whether stereotactic radiosurgery is palliative or curative depends on the disease or condition. It may be palliative for malignant tumors, but it may be curative for functional disorders and other benign, non-cancerous conditions.
Side effects are low, but they may include seizures, swelling or edema, weakness, numbness, or other neurological deficits. Most of the side effects are temporary and can be treated, in the unlikely event that they occur.
Stereotactic radiosurgery treatments are used on many different types of brain and spine tumors, including metastases, gliomas, meningiomas, acoustic neuromas, pituitary adenomas, and schwannomas. Other conditions that can be treated include vascular malformations, such as arteriovenous malformations, and functional disorders, such as trigeminal neuralgia, tremor, and temporal lobe epilepsy. Less commonly, we can use stereotactic radiosurgery for other intractable pain conditions, even obsessive-compulsive disorder, and other forms of epilepsy. In addition, other physicians use stereotactic radiosurgery to treat conditions outside the brain and spine.
CyberKnife treatment, another form of stereotactic radiosurgery, utilizes groundbreaking guidance technology to target and track tumors and lesions anywhere in the body with computerized image-guided precision. These views are provided by several X-ray cameras configured with powerful computer software. This continuously updates the target’s position during treatment. They feed the images to a computer-controlled robotic arm that carries an advanced linear accelerator (radiation source) that delivers hundreds of radiation beams to the designated site.
With the data received from the X-rays, the robot is in constant motion. Computers monitor the anatomy, check and recheck the patient’s position and compensate for the slightest movements by instantly repositioning the linear accelerator so it can deliver the radiation beams quickly and accurately. On its own, each beam is relatively weak. However, when the beams converge on the target, their power is precise; so precise that physicians can destroy even deeply imbedded tumors and lesions with complex shapes without harming adjacent healthy tissue.
Achieving surgical-like outcomes, CyberKnife can be an alternative to open surgery. Treatments are performed as outpatients. Anesthesia is unnecessary. There is no blood loss. The complication risk is lowered.
When to Employ Stereotactic Radiosurgery
We only use stereotactic radiosurgery when we are certain of the diagnosis, and we will take a biopsy if necessary. If we need quick decompression for resolution of symptoms, we would not use stereotactic radiosurgery, because it can take months or years to become fully effective. Very large targets are also not good candidates for stereotactic radiosurgery.
Stereotactic radiosurgery is a low risk, high efficacy procedure that allows us to avoid more risky procedures. It is especially good for functional disorders, such as trigeminal neuralgia, and many types of brain and spine tumors.