Gamma Knife

Gamma knife is the name for a machine in which high energy gamma-rays are used to irradiate intracranial tumor cells difficult to treat with other methods. Acoustic neuroma, a tumor lodged in the vestibular nerve, is an example. In the Boston Gamma Knife Center of Jen-San Tsai, Ph.D., at Tufts New England Medical Center of Boston an array of 201 gamma-emitting cobalt-60 sources is laid out in such a way that the rays converge on the target tumor, whose coordinates are carefully determined by CT and MRI scans. The resultant noninvasive procedure, called stereotactic radiosurgery, is in use at 66 facilities in North America, and 154 facilities installed worldwide. At the meeting of the American Association of Physicists in Medicine (AAPM) in Montreal this week, Tsai (jtsai@lifespan.org, 617-636-1681) reports on new methods for coordinating MRI and CT scans to obtain the best possible tumor location to insure proper dosages. (See AAPM meeting site.)