For decades neurosurgeons have treated diseases of the brain by beaming radiation inside the skull, sidestepping the need to cut through scalp and bone. The arrival of a 30-ton gamma knife at Yale in July enables this intricate form of brain surgery with a previously unmatched precision.

The Swedish-made gamma knife beams up to 201 gamma rays around a single point in the brain, letting the radiation accumulate on that point without disturbing surrounding tissue. Individually, the rays do no harm, but when they converge on their target the concentration of radiation can destroy lesions, tumors and blood vessel malformations. Based at the Temple Medical Center, the $2.9 million instrument is the first of its kind in Connecticut and one of
only 35 in the whole country.

Treatment with the gamma knife requires placing the patient in a fixed frame that keeps the head absolutely steady during the procedure. Once ready, the patient lies inside the gamma knife for between 15 minutes and two hours. The radiation treatment is accurate to within .3 millimeters. After the treatment the radiation can take days or weeks to achieve the desired effect.

Because it is more accurate and easier to use, the gamma knife has largely replaced its precursor, the linear accelerator which beams X-rays into the brain. The linear accelerator was accurate to within plus or minus 1 millimeter and could take hours to do what the gamma knife does in minutes.

“With the gamma knife,” said Alain deLotbinière, M.D., associate clinical professor of neurosurgery and director of radiosurgery at Yale-New Haven Hospital and of the Gamma Knife Surgery Center, “we can destroy abnormal tissue very precisely without damaging adjacent normal brain tissue and without subjecting patients to the trauma of surgery. The gamma knife enables us to destroy tumors in areas of the brain that are inaccessible to the surgeon’s scalpel or so close to vital structures, such as the optic nerve, that surgery could irreparably harm normal brain tissue.”