The Principle
Stereotactic radiosurgery is the delivery of a single, high dose of radiation through the intact skull to a small and critically located intracranial area. At Yale, this treatment is delivered using a unit call The Gamma Knife. The Gamma Knife contains 201 cobalt-60 sources of approximately 30 curies each at the time of loading, placed in a hemispherical array in a heavily shielded unit. Using this unit and collimator helmets, radiation can be focused to a specific target point within the head with sub-millimeter positioning accuracy in such a fashion that a high dose of radiation is delivered to the target while sparing the surrounding tissue the same high dose of radiation. Complex-shaped lesions are treated by combining collimators of different sizes with selected beam blocking and weighting using a sophisticated computer planning system. This ensures that tight conformation of the doses to the edge of the target volume is achieved such that each patient receives a "tailored" plan.

Safety and Efficacy
Unlike the linear accelerator based systems such as the LINAC or cyberkife, the Gamma Knife has few moving parts thereby eliminating many sources of inaccuracy and unreliability. Because the radiation fall off is very steep outside the target area, the surrounding brain receives minimal radiation thereby sparing harmful delayed side effects to neighboring critical structures. Many of the risks of open surgery are eliminated with Gamma Knife radiosurgery, making the procedure particularly useful in patients with advanced age or in those patients with other illnesses where conventional surgery would pose an unacceptably high risk. Finally, the efficacy and cost effectiveness of the Gamma Knife treatment have been proven in numerous studies when comparing it to the alternative, namely open surgery.

Who can benefit from this treatment? Indications at present include:

• Benign tumors such as meningiomas, acoustic neuromas, pituitary adenomas and craniopharyngiomas

• Primary or recurrent malignant brain tumors such as astrocytomas or oligodendrogliomas

• Solitary and multiple brain metastases Head and neck tumors such as nasopharyngeal carcinomas and ocular melanomas

• Arteriovenous malformations (AVMs)

• Trigeminal neuralgia

• Intractable pain secondary to cancer

• Movement disorders such as Parkinson's disease and essential tumor

The Yale facility is also capable of treating pediatric patients with any of the above conditions. Patients referred to the Yale-New Haven Gamma Knife Center will be evaluated by a team of specialists with extensive experience, including neurosurgeons, radiation oncologists and neuroradiologists. Candidates for the procedure are selected for treatment only after a thorough review of all prior medical records and imaging studies.

Benefits of Gamma Knife Treatment
Since Gamma Knife radiosurgery requires no incisions and is performed under local anesthesia, the risks of infections and adverse reactions to general anesthesia are eliminated. Patients experience minimal pain and are therefore usually able to return to their former activities without discomfort or restrictions within 24 hours of the procedure. Hospitalization is only required in exceptional circumstances.. This results in a significant cost savings over conventional surgery. Because only the target tissue is irradiated, sparing the surrounding brain, hair loss is eliminated and secondary reactions such as nausea and epileptic seizures are minimized. Finally, the accumulated experience of over 30 years of treatment using the Gamma Knife allows for predictable outcomes with a high degree of accuracy.

Director
Veronica L.S. Chiang, M.D.

Contact Information
The Yale Gamma Knife Center can be reached at:
203-785-2808
203-688-4040
or by direct email to Veronica.chiang@yale.edu

Copyright © 2000 Yale University School of Medicine.
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