St. Charles Medical Physicist Phoebe Shulman-Edelson points out where the radiation is emitted from one of the hospital's existing linear accelerators.

Amid the dust and shuffling metal of St. Charles Bend’s ongoing cancer center expansion, a box-shaped room is slowly materializing.

Once this so-called vault is finished next summer — along with the rest of the $13 million project — it will sit empty for a few years.

The room will eventually hold a linear accelerator, the device used to deliver radiation treatments to cancer patients. St. Charles won’t actually buy the accelerator for several years, but officials there say they’re saving a whole lot of money by building the vault ahead of time.

“We’re building for the future,” said Linyee Chang, St. Charles Cancer Center’s medical director, “and part of building for the future means anticipating the needs for our population and being aware and responsible. Knowing the lifespan of the existing equipment we have, we anticipate what we’re going to need.”

If purchased today, a linear accelerator would cost roughly $4 million, but that could fluctuate by the time St. Charles buys one, said Kayley Mendenhall, a spokesperson for the hospital.

Hospitals across the country commonly build vaults ahead of purchasing linear accelerators, said Per Halvorsen, chair the American Association of Physicists in Medicine’s Professional Council and chief of radiation therapy physics at Lahey Health in Burlington, Mass.

In addition to saving money, building the vault ahead of time allows hospitals to spread the cost of the accelerator across several budget cycles, he said. Vaults typically cost roughly $1 million to build, while accelerators run between $2 million and $6 million, Halvorsen said.

As the forerunning method of delivering radiation treatments, linear accelerator machines are a pivotal component of any cancer center. St. Charles currently has two linear accelerators, and the forthcoming machine will put one of the existing machines into retirement.

St. Charles first began treating patients using a linear accelerator when the cancer center opened in 1982, marking the first time radiation therapy was available to cancer patients in Central Oregon, Chang said.

“Before that, there were medical oncologists, but patients that needed therapy needed to travel to Portland or Eugene,” she said.

That machine eventually was replaced with a newer model in 2002. In 1995, the hospital added a second accelerator, which was replaced in 2010.

Accelerators work similarly to diagnostic X-rays, except they deliver roughly 1,000 times more energy to the subject, said Klaudia Meyer, a medical physicist at St. Charles Bend.

Vaults are crucial in ensuring the safety of the areas surrounding linear accelerators. The walls of St. Charles’ vaults, for example, are 8 feet thick and made of concrete, Meyer said.

Designed improperly, vaults can quietly and invisibly leak radiation, Halvorsen said. Fortunately, he said, there aren’t many examples of that in practice.

“The problem, of course, is that you don’t know just inherently that you’re getting a dose of radiation,” Halvorsen said. “You’d have to go there with a detector and measure in order to know that. If someone designed it poorly and also didn’t monitor things carefully, you might just not know.”

When they’re undergoing radiation treatment, patients sit alone in the vault for between 10 and 20 minutes, Meyer said. Medical personnel stay outside of the room. Once the accelerator is turned off, residual radiation is not a threat to people inside or outside the hospital, she said.

Between 40 and 50 patients use St. Charles’ two linear accelerators each day, Chang said.

Work on the St. Charles Cancer Center, which will be connected to the hospital in Bend, began in June. The two-story, 18,000-square-foot facility is designed to bring the system’s cancer services under one roof. Currently, cancer treatment is spread between the current cancer center adjacent to the hospital and a leased building near Northeast Courtney Drive and Northeast 27th Street.