New Campaign to Curb Radiation From CT Scans
Experts Hope to Reduce Use of Excessive Imaging Tests
Annual Radiation Doses
At the meeting, University of California, San Francisco researchers reported that the average annual radiation dose we receive nearly tripled over 15 years, from 0.80 mSv in 1994 to 2.3 mSv in 2008.
"A small but increasing proportion of patients received high doses," says researcher Ingrid Burger, MD, PhD.
In 1994, 0.49% and 0.04% of those studied received doses of more than 50 and 100 mSv, respectively. In 2008, 2.4% and 0.47% received doses exceeding these thresholds, she says.
The researchers reviewed nearly 24 million radiation exams of people enrolled in seven HMOs across the country.
CTs and the Elderly
In the other study, Basu and colleagues used Medicare claims data on over 10 million patients to estimate cancer risks related to CT scans.
They found a risk of between 0.02% and 0.04%, "surprisingly lower than we expected," Basu tells WebMD.
The researchers also found that the proportion of patients who had imaging studies increased over time. From 1998 to 2001, for example 42% of patients had scans, compared with 50% of those in 2002 to 2005.
Although only elderly people were studied, the findings could apply to middle-age people whose biological sensitivity to radiation is similar, Basu says.
Max Wintermark, MD, of the University of Virginia in Charlottesville, agrees. He notes that elderly people account for the greatest use of CT imaging.
"In younger patients we are always trying to do something that doesn’t involve radiation," Wintermark says. "We try to use MRI or ultrasound instead, if we can."
A limitation of the study was that cancer risk was estimated using the National Academy of Sciences data. Patients were only followed for up to four years, a short period during which radiation-associated cancers might not develop.
Also, "you would expect cancer risk to be lower in the elderly, who may die due to other reasons before a secondary cancer has time to manifest," Hendee says.
Basu says a study in which people's radiation exposures and subsequent cancers are tracked over time is needed.
The new studies were presented at a medical conference. The findings should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.