Stereotactic Radiosurgery and Gamma Knife®
Gamma Knife® Radiosurgery
Gamma Knife® Radiosurgery is a non-surgical medical procedure recognized as the preferred treatment for brain tumors, arteriovenous malformations and brain dysfunctions such as trigeminal neuralgia. At NewYork-Presbyterian, Gamma Knife® treatments are provided as part of a full spectrum of precision radiation therapy techniques. Our center is one of only 100 sites worldwide to have this 20-ton radiosurgery system.
Gamma Knife® provides an alternative option for many patients for whom traditional brain surgery is not an option. With precise delivery of high doses of radiation, Gamma Knife® is able to kill cancer cells and shrink tumors while avoiding damage to healthy brain tissue. The lesion being treated receives a high dose of radiation with minimum risk to nearby tissue and structures leaving little discomfort if any to the patient. Due to the absence of an incision, there is no risk of hemorrhage or infection and treatment can be effectively administered in a single session. Patients can usually go home the same day and return to work or school immediately.
The Gamma Knife® is not a knife, but rather a highly developed treatment system, capable of directing up to 201 beams of gamma radiation to converge on a targeted abnormality within the brain. When concentrated, the rays provide enough radiation to treat the diseased area effectively; while the low intensity of each individual beam ensures the safety of the surrounding healthy brain tissue.
With the Gamma Knife®, areas of the brain for which other therapies or conventional surgery are ineffective, can be successfully treated. The Gamma Knife®'s precision and safety make it a highly appropriate choice for both pediatric and adult patients.
Linear Accelerator Based Radiosurgery / X-Knife
NewYork-Presbyterian also offers linear accelerator based stereotactic radiosurgery which provides radiation in the form of a highly focused beam applied in multiple sweeps around the lesion. This highly accurate form of treatment is ideal for the treatment of certain types of tumors. This method uses either a single session treatment called stereotactic radiosurgery (SRS) or multiple treatment sessions called fractionated stereotactic radiotherapy (STRT), with each offering advantages for appropriately selected patients. Initially SRS was used primarily for tumors in the brain, but it has since been adapted for radiation therapy treatment to other areas of the body. Both stereotactic radiosurgery and stereotactic radiotherapy are non-invasive treatments that use pencil-thin beams of radiation generated by a special linear accelerator to administer treatment effectively allowing higher doses of radiation to be delivered. Due to the ability to deliver higher doses of radiation to the treatment area, patient motion must be controlled.
For immobilization purposes, a head frame is attached to the patient's skull through the use of specially designed pins until the treatment session is finished. There is little or no discomfort during the actual treatments which can be performed on an outpatient basis without many of the usual risks and side effects associated with surgery. Part of the linear accelerator called a gantry rotates around the patient, delivering radiation beams from different angles. The ability to rotate 360° around the patient enables the very small beams with varying intensity to be aimed at the tumor from multiple angles. The radiation treatment being delivered to the patient can be modulated continuously throughout treatment without interrupting the gantry movement. By shaping and modulating a highly focused treatment beam, the dose to the tumor is more concentrated, in turn sparing surrounding healthy tissue better. SRS differs from existing techniques because it delivers dose to the whole volume, rather than slice by slice. The immobilization is done by a neurosurgeon, who places several pins into the skull. These pins are used to help immobilize the patient on the treatment table for the treatment, assuring the patient's head remains absolutely still for the high dose radiation treatment directed to the target. The plan is created using CT and MRI scans, with the data input into the treatment planning computer.
Stereotactic Body Radiotherapy (SBRT)
Stereotactic Body Radiotherapy, or SBRT, is a treatment procedure similar to brain stereotactic radiosurgery and radiotherapy, except it deals with tumors outside of the brain. SBRT works by delivering high doses of radiation to accurately target the tumor while sparing normal organs. Due to a high radiation dose being delivered, there is an increase in the treatment time for each fraction.
However, treatment is usually complete within 5-10 days as opposed to the standard 40 day course of treatment. Features such as a high precision Multi-Leaf Collimator for IMRT delivery and Cone Beam CT imaging for precise target localization allow for small treatment fields so that there are minimal side effects to the patient. Some procedures will use the combination of an ultra high dose rate and mixed treatment energies which allow for better dose conformity to tumor. The ability to conform the dose to the shape of the tumor allows the clinician to treat a smaller volume which in turn offers an alternate choice of treatment for patients with inoperable tumors or elderly patients who are high risk for surgery. SBRT can be used to treat primary, metastatic and previously irradiated cancer sites.