New equipment improves cancer treatment

  • Published
  • By Sue Campbell
  • 59th Medical Wing Public Affairs
Wilford Hall Medical Center’s radiation oncology department recently purchased a new linear accelerator that is significantly improving patient care.

Wilford Hall officials said they began performing radiation therapy more than 30 years ago, using a cobalt unit with an active radiation source, a physical piece of radioactive material that had to be changed out periodically. A radioactive beam was directed into the patient with limited ability to shape the beam to the tumor’s shape causing normal tissues outside the tumor to be radiated as well. The cobalt unit was removed in the early 1990s and replaced with the hospital’s first linear accelerator.

Linear accelerators use microwave technology similar to radar. High-energy X-rays form a beam that matches the patient’s tumor. The beam comes out of a part of the accelerator called a gantry, which rotates around the patient. The patient lies on a moveable treatment couch and lasers are used to make sure the patient is in the proper position. Radiation can be delivered to the tumor from any angle by rotating the gantry and moving the treatment couch.

“The linear accelerator uses very high-voltage electricity that can be turned on and off,” said Maj. (Dr.) Cameron Pimperl, radiation oncology flight commander. “When it’s turned off, there’s no source of radiation. This greatly reduces radiation protection issues, and linear accelerators produce higher energy-radiation beams to better treat deep-seated tumors.”

The new linear accelerator has additional capabilities, officials said.

“It can be almost completely controlled by computer,” Pimperl said. “Therapists can now set up instructions involving 20 or 30 consecutive segments of radiation beams, where before we could practically treat only four to six with manual control.”

The result is that patients receive more customized dose distribution, and the radiation can be very closely shaped to fit the shape of any tumor, officials said.

“With the previous accelerator, we could produce simple geometric dose distributions,” Pimperl said. “With the new equipment, we can form literally any shape, even complex, convoluted shapes.

There is still plenty of human involvement, as technicians constantly monitor the process and adjusting parameters as needed.

“It can streamline the process for the staff, but the main benefit is to the patient,” Pimperl said. “It is very critical that you radiate the correct areas, covering the cancer but avoiding critical structures that can be permanently damaged by the radiation treatment. This technology allows us to treat complex-tumor shapes in very close proximity to critical structures.”

Another improvement with the new equipment is electronic portal imaging which allows the radiologist to immediately tell if he or she radiated the correct area. It provides instant feedback on the position, officials said.

“Our patients want to hear that only the area that needs the radiation will be affected,” Pimperl said. “Our patients naturally want the most state-of-the-art technology. This definitely gives them the best treatment and will save the government money by not having to refer patients to civilian medical facilities.”