It’s a good bet that somewhere out there, perhaps on the other side of the globe, a package from MD Anderson will be delivered to a cancer researcher today. Inside, the recipient will find a carefully cushioned plastic body part. Possibly a head, spinal cord or liver.
Following the enclosed instructions, they’ll position the “anthropomorphic phantom” under their radiation therapy machine as they would a patient and run through some tests. Then they’ll send the irradiated phantom back to MD Anderson for analysis.
That analysis is just one of the services performed by a team in Outreach Physics whose job it is to make sure that radiation-therapy facilities wanting to participate in group clinical trials can deliver doses that are comparable and consistent from institution to institution.
The National Cancer Institute (NCI) has relied on MD Anderson to monitor the machines used to deliver radiation therapy in NCI-funded studies for the last 50 years. The part of Outreach Physics that’s funded by a long-term NCI grant is our Imaging and Radiation Oncology Core – Houston Quality Assurance Center, better known as IROC Houston.
“We’re here to minimize uncertainty and maximize accuracy,” says physicist David Followill, Ph.D., chief of Outreach Physics and director of IROC Houston. “We’re kind of the watchdog for radiation therapy.”
Last year, IROC Houston monitored 2,200 radiation facilities across the United States and 60 countries.
This is done in several ways.
Gauging radiation output
Radiation output for every machine in an NCI-funded study must be measured annually to ensure all 5,000 of them are calibrated properly. The enormous task is accomplished mostly by mail.
IROC has about 100 phantoms that can be shipped via FedEx to research facilities for irradiation. After the phantoms are shipped back and analyzed, they’re cleaned and reused.
But with so many machines to monitor, IROC more often sends a simple kit with a small box that contains tiny pellet-shaped detectors that measure the dose of radiation delivered. Placed where the patient would lie, these detectors are exposed to radiation as directed and sent back to Houston for analysis.
This service also is available to institutions that aren’t participating in clinical trials. It’s offered as an independent peer review by Radiation Dosimetry Services, which also is part of MD Anderson’s Outreach Physics section. That team monitors over 1,100 sites. Between them, the two teams monitor 98% of all the radiation treatment facilities in the U.S.
Traveling with sophisticated radiation-measuring equipment, IROC Houston physicists periodically make spot checks at U.S. facilities in person. The researchers’ quality assurance procedures are reviewed, and recommendations are made.
“It’s fun for me because I get to travel around the country, meet physicists all over and get to know this growing community,” she says. “I enjoy collaborating with new centers and having an opportunity to improve the quality of radiation therapy delivered to their patients.”
Review of clinical practices
To make sure that data from the studies don’t become skewed by any deviations from their protocols, physicists also review patient records before, during and after treatments.
Taylor recalls a case in which one institution’s results were off across the board. It took some detective work, but she eventually realized that the hospital’s barometric pressure recordings were wrong. The researchers were using the readings from a nearby airport, which had adjusted its numbers to account for sea level.
“I hate to say it, but we still find mistakes,” Followill says.
Few are serious enough to put a patient’s health at risk, but small mistakes can have a large combined effect and jeopardize valuable, time-consuming research, he says.
“Our job is to find them and figure out how to fix them – no matter where they are.”
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