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Gamma Knife

gamma_knife_poster.gif (12077 bytes)

                           GAMMA KNIFE

The Leksell Gamma Knife is an alternative or adjunct to conventional brain surgery.  The principles behind the development of the Gamma Knife were first conceived by a Swedish neurosurgeon, Lars Leksell, during the 1950s. He envisioned a multisource Gamma ray emitter that would be able to focus very accurately on an intracranial target and thus replace open surgery for some conditions. In 1967, the first Gamma Knife unit was put into clinical use in Karolinska and this was a 179 cobalt 60 source.

The steps in treatment: step 1, step 2 and step 3.

leksell_unit.jpg (8065 bytes)

Gamma Knife stereotactic radiosurgery has been in use in the United States for over 10 years and there have been in excess of 300,000 procedures performed worldwide. The most common diseases treatable would be brain mets, AVM's and perhaps trigeminal neuralgia, (see world wide stats.)

see the inside of a gamma knife

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Gamma Knfe Model C is the machine used at Bayfront


The Gamma Knife procedure has been proven highly effective in the treatment of certain malignant and benign brain tumors, arteriovenous malformations and trigeminal neuralgia.  In addition, treatments for Parkinson's disease, epilepsy, and intractable pain are showing promising research results. The Gamma Knife treats the patient with 201 individual gamma rays, targeted with great precision to converge on small, well circumscribed and critically located structures in the brain. 

Stereotactic radiosurgery is defined as the delivery of a single, high dose of radiation through the intact skull to a small and critically located intracranial volume. 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. A collimator helmet focuses the radiation 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. 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 dose to the edge of the target volume is achieved such that each patient receives a "tailored" plan. Unlike the linear accelerator, 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 little radiation thereby minimizing harmful side effects to neighboring critical structures.

Long-term results after radiosurgery for benign intracranial tumors.

Kondziolka D, Nathoo N, Flickinger JC, Niranjan A, Maitz AH, Lunsford LD.   Neurosurgery. 2003 Oct;53(4):815-21;

Departments of Neurological Surgery and Radiation Oncology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.

We evaluated 285 consecutive patients who underwent radiosurgery for benign intracranial tumors between 1987 and 1992. Our series included 157 patients with vestibular schwannomas, 85 patients with meningiomas, 28 patients with pituitary adenomas, 10 patients with other cranial nerve schwannomas, and 5 patients with craniopharyngiomas. Prior surgical resection had been performed in 44% of these patients, and prior radiotherapy had been administered in 5%. The median follow-up period was 10 years. RESULTS: Overall, 95% of the 285 patients in this series had imaging-defined local tumor control (63% had tumor regression, and 32% had no further tumor growth). The actuarial tumor control rate at 15 years was 93.7%. In 5% of the patients, delayed tumor growth was identified. Resection was performed after radiosurgery in 13 patients (5%). No patient developed a radiation-induced tumor. Eighty-one percent of the patients were still alive at the time of this analysis. Normal facial nerve function was maintained in 95% of patients who had normal function before undergoing treatment for acoustic neuromas. CONCLUSION: Stereotactic radiosurgery provided high rates of tumor growth control, often with tumor regression, and low morbidity rates in patients with benign intracranial tumors when evaluated over the long term. This study supports radiosurgery as a reliable alternative to surgical resection for selected patients with benign intracranial tumors.

Oncology (Huntingt) 1998 Aug;12(8):1181-8, 1191; discussion 1191-2

Clinical uses of radiosurgery.

Chang SD, Adler JR Jr, Hancock SL

Department of Neurosurgery, Stanford University School of Medicine, Stanford, California, USA.

Radiosurgery uses stereotactic targeting methods to precisely deliver highly focused, large doses of radiation to small intracranial tumors and arteriovenous malformations (AVMs). This article reviews the most common clinical applications of radiosurgery and the clinical results reported from a number of series using either a cobalt-60 gamma knife or linear accelerator as radiation sources. Radiosurgery is used to treat malignant tumors, such as selected cases of brain metastases and malignant gliomas (for which stereotactic radiosurgical boosts are utilized in conjunction with fractionated radiation therapy), as well as benign tumors, such as meningiomas, acoustic neuromas, and pituitary adenomas. Treatment of small AVMs is also highly effective. Although radiosurgery has the potential to produce complications, the majority of patients experience clinical improvement with less morbidity than occurs with surgical resection.

The Mayo Clinic gamma knife experience: indications and initial results.

Pollock BE, Gorman DA, Schomberg PJ, Kline RW.   Mayo Clin Proc 1999 Jan;74(1):5-13

Department of Neurologic Surgery, Mayo Clinic Rochester, MN 55905, USA.

We conducted a retrospective analysis of 1,033 consecutive patients who underwent gamma knife radiosurgery at Mayo Clinic Rochester between January 1990 and January 1998.

Indications Numbers Effective
AVM 97 74%
benign brain tumors 209 96%
brain metastases ns 90%
trigeminal neuralgia 20 70%

RESULTS: The number of patients undergoing radiosurgery increased from 57 in 1990 to 216 in 1997. Of 97 patients with arteriovenous malformations who underwent follow-up angiography 2 years or more after a single radiosurgical procedure, 72 (74%) had complete obliteration of the vascular malformation. Of 209 patients who underwent radiosurgery for benign tumors (schwannomas, meningiomas, or pituitary adenomas) and had radiologic studies after 2 years or more of follow-up, tumor growth control was noted in 200 (96%). Tumor growth was also controlled in 90% of brain metastatic lesions at a median of 7 months after radiosurgery. Of 20 patients with trigeminal neuralgia and follow-up for more than 2 months, 14 (70%) were free of pain after radiosurgery. CONCLUSION: Radiosurgery is a safe and effective management strategy for a wide variety of intracranial disorders. Use of radiosurgical treatment should continue to increase as more data become available on the long-term results of this procedure.