High doses

WASHINGTON — Emergency room doses of radiation from CT scans and other diagnostic tests may increase patients’ lifetime risk of cancer, a new study suggests.

Timothy Bullard and his colleagues calculated ER patients’ exposure to radiation in four different Orlando, Fla., hospitals over five years. The researchers found that patients were routinely exposed to high levels of radiation, sometimes getting up to 15 radioactive diagnostic tests in one visit. About 10 percent of the study population had already been exposed to more radiation than was considered safe, says Bullard, of the OrlandoRegionalMedicalCenter. The popularity of CT scans may be a culprit, he says, as a single scan delivers the same dose as 200 to 250 chest X-rays.

The findings were presented May 29 at the annual Society for Academic Emergency Medicine meeting.

While the group did not look at cancer rates, past studies, including those at Hiroshima and Nagasaki, established that risk of cancer increases with radiation exposure.

“If you took a thousand people and gave them each one CT scan, you’d find one additional case of cancer,” he says. While the imaging test increases a person’s cancer risk only slightly, over a population that can translate to several thousand extra cases of cancer a year, Bullard says.

What’s more, Bullard’s team believes their calculations underestimate how much radiation people absorb over a lifetime. “We looked at just one hospital in each system,” he says. “If you look over a longer period of time, and include other facilities, I’m sure the exposure would be higher.”

Despite the risk, Bullard says nuclear imaging is often a necessary tool for diagnosis. However, doctors need to be aware of the radiation doses associated with each of these tests. One way to make sure people don’t get unnecessary tests would be to develop standards for when scans are administered, says David Brenner, a radiation biophysicist at ColumbiaUniversity who was not involved in the study. Keeping better track of electronic records may also help, he says.

“The question is whether all those people really needed the CT exams they got,” Brenner says. “Many places where you go into the ER with abdominal trauma, you’ll pretty well automatically get a CT scan, and sometimes that’s needed and sometimes that’s not.”