Gamma Knife broadens scope of patient treatment

By Timothy Maestas
Staff Writer

The installation of the Gamma Unit Facility at USC University Hospital enables doctors to provide a wide range of treatment for arteriovenous malformations and benign and malignant tumors in the brain that would otherwise be inoperable or difficult to remove.
The facility employs the Gamma Knife, a system which focuses 201 cobalt-60 radiation beams on a targeted area of diseased tissue within the brain. The beams damage the diseased tissue without harming healthy tissue immediately surrounding it.
Gamma Unit team members believe treatment with the Gamma Knife is more effective than past treatment procedures because it is highly focused, enabling doctors to deliver a higher dose of radiation to the tumor, or AVM.
Under the direction of Dr. Michael L.J. Apuzzo, the Gamma Unit currently focuses exclusively on the brain, but sees potential in the system's ability to treat such functional disorders as Parkinson's disease and epilepsy.
"We have the most senior and respected clinicians," said USC University Hospital Chief Operating Officer Jeffrey Green. "With the Gamma Knife and all of our other neurological capabilities, that gives us one of the best neurological programs in the state, if not the country."
Treatment involves the patient wearing a specialized helmet that focuses the exact point of intersection of the high-powered beams onto a predetermined target. A computerized system then moves the patient towards an 18-ton sphere containing the radiation sources, which only admits the patient's head. The patient then undergoes a series of "shots," each of which lasts from five to ten minutes.
According to Dana MacPherson, Nurse Coordinator for the Gamma Unit, patients tend to start out rather intimidated by the use of radiation and the unit's size.
"Some are excited, some are nervous, but after the first shot they are usually very relaxed. There is some initial anxiety," MacPherson said.
MRI, CT, PET, and angiography are used to determine if a patient's condition calls for the treatment. This takes an average of three hours to complete.
"Doctors also use biopsies and past histories in the evaluation of a patient, but they usually go by the MRI and the size of the affected area. It has to be 3 1/2 centimeters or less," MacPherson said.
Patients undergo a single session and are admitted into the hospital on the day of the procedure. They are usually released the following morning. While the procedure is costly, it is judged by unit members to be cheaper than open brain surgery because of the short hospital stay and recovery rate.
Development of the unit's advanced software system has expanded the limits of the instrument since its initial Stockholm, Sweden construction in 1968, said Dr. Apuzzo in the USC University Hospital Quarterly. The system boasts a success rate of 85 percent for AVM's and between 50 and 95 percent for tumors.
The opening of the unit at University Hospital in the summer of 1994 made it the fourth such device on the West Coast. Forty-five Gamma Knife units have been installed in hospitals worldwide, and have treated more than 13,000 patients as of June, 1993. USC University Hospital has treated 145 people.
While the hospital does not own the Gamma Knife, a $1.3 million bunker-like building was built to house the unit, Green said. The building has 14-inch thick concrete walls and a 10-inch thick concrete ceiling.