Gamma knife is a neurosurgical tool intended absolutely for the treatment of brain disorders. The gamma knife together with its associated computerized treatment planning software is being used primarily for locating the tumors. It permits physicians to locate and irradiate relatively small targets in the head, oftentimes the brain, with extremely high precision. The targeted areas can be given intense doses of radiation while the surrounding tissues are largely being spared. The gamma knife can be used for a wide variety of problems. It is use to treat selected malignant tumors that develop in the brain, such as primary brain tumors, or has spread to the brain, metastatic tumors. It is also being used to remedy benign brain tumors, such as meningiomas, pituitary adenomas, and acoustic neuromas, blood vessel defects such as arteriovenous malformations, and functional problems, such as trigeminal neuralgia. It is being further evaluated for possible future uses to cure or treat epilepsy and Parkinson’s disease. The gamma knife allows the patients to undergo a non-invasive form of brain surgery without surgical risks, a long hospital stay or subsequent rehabilitation.

The gamma knife surgery is one of a kind in that no surgical incision is made to expose the inside of the brain, thus reducing the risk of surgical complications and eliminating the side effects and dangers of general anesthesia. The gamma knife is not suitable for large targets, larger than three to four centimeters in sizes, and is not used for targets outside of the head. It loses its ability to spare surrounding normal tissues as the number of targets increases. Stereotactic radiosurgery is the process being used to make the gamma knife works. It uses multiple beams of radiation, known as the “blades”, programmed to target the lesion at their intersection point and converging in three dimensions to focus precisely on a small volume, such as a tumor, permitting intense doses of radiation to be delivered to that volume safely. In a single treatment session, 201 beams of gamma radiation focus precisely on the lesion. Most lesions, over time, slowly decrease in size and dissolve. The exposure is short and only the tissue being treated receives a significant radiation dose, while the surrounding tissue remains unharmed

A special head-frame that has three-dimensional coordinates with four screws built into it is attached to the skull while the patient is placed under local anesthesia. Then, computed tomography (CT) scan and/or a catheter angiogram and/or magnetic resonance imaging (MRI) are obtained and the results are sent to the gamma knife’s planning computer system. Physicians such as radiation oncologists, neurosurgeons and/or neuroradiologists, and medical radiation physicists use the planning computer to determine the exact relationship between the target lesions, and the frame. Then they calculate how to set the controls of the gamma knife to treat the targets optimally. Targets most of the time are best treated by combinations of several aims, also known as “shots.” The physicians and physicists regularly consider numerous modifications until an optimal plan is created. Concurrently, an optimal dose is selected. Determined in the planning process by using the three-dimensional coordinates the frame is then precisely attached to the gamma knife unit to guarantee that when the unit is activated, the target is placed exactly in the center of approximately 200 precision-aimed, converging beams of (Cobalt-60 generated) gamma radiation. Treatment takes from several minutes to a few hours to complete depending on the dose required and the shape of the target. The patients usually do not sense the radiation. After the treatment, the head-frame is removed. One treatment session is normally being required for each target. The gamma knife surgery represents a major development in brain surgery and has altered the field of neurosurgery. Its progressed has improved neurosurgical treatments offered to patients with brain tumors and vascular malformations by providing an accurate, reliable and safe treatment option.