Researchers Call for Standardizing CT Dose to Lower Risk of Radiation-Induced Cancer

The latest study on radiation exposure from computed tomography procedures found wide variation between the highest and lowest radiation dose a patient receives and a higher assessed risk of cancer.

Researchers at the University of California, San Francisco, discovered a 13-fold variation between the highest and lowest radiation dose from CT scans by estimating effective dose from 11 common CT procedures, according to a study published in the Dec. 14, 2009, issue of Archives of Internal Medicine.

“In day-to-day clinical practice, we found significant variation in the radiation doses for the same type of computed tomography procedures within institutions and across institutions,” said lead investigator Rebecca Smith-Bindman, M.D., a professor of radiology at UCSF, in a UCSF press release. “Our results highlight the need for greater standardization because this is a medical safety issue.”

The authors estimated that the risk for CT radiation-induced cancer was considerably higher than the published rate of one in 1,000 from certain types of scans, with the greatest for patients 20-years-old or younger.

“The risk associated with obtaining a CT is routinely quoted as around 1 in 1,000 patients who undergo CT will get cancer. In our study, the risk of getting cancer in certain groups of patients for certain kinds of scans was as high as 1 in 80,” said Smith-Bindman in the press release.

In a separate editorial, Rita F. Redberg, M.D., MSc., noted that another article in the issue projected 29,000 excess cancers could result from the CT scans performed in 2007 alone, with a corresponding 15,000 deaths within 20 to 30 years following exposure. In that study, Berrington de Gonzalez et al estimated that 72 million CT scans were performed that year and determined the cancer risk by excluding studies performed after a cancer diagnosis.

Smith-Bindman et al combined the radiation dose findings with data from the National Academy of Science National Research Council to determine health risks. The dose varied based on the location and technical parameters of each CT scanner, according to the researchers.

The authors concluded the article with three identified methods to improve safety and reduce radiation exposure that included reducing unnecessary studies; establishing lower-dose standard protocols for every CT scanner; and using federal legislation and FDA oversight to standardize radiation doses. Both articles can be accessed at http://archinte.ama-assn.org/current.dtl.