New Research on CT Radiation Exposures, Risks, Fuels Growing Concern

By Jeffrey Norris, UCSF Science Cafe | December 18, 2009

The use of computed tomography (CT) scans in medicine to diagnose disease, and in many cases save lives, has exploded in recent decades. The down side, a new study concludes, is that the radiation US patients receive from these medical exams will eventually result in 29,000 new cancer cases and 15,000 new cancer deaths each year at current levels of CT usage and cancer cure rates.

Furthermore, the dose of radiation delivered during CT exams is wildly variable, the researchers found, even within the same type of exam. In general, the radiation dosages delivered to patients were substantially higher than expected. The research findings are published in the current issue of the Archives of Internal Medicine.

UCSF's Rebecca Smith-Bindman, MD, a radiologist and epidemiologist, led the study. Smith-Bindman and her collaborators investigated radiation exposure to 1,119 patients resulting from 11 of the most commonly used types of diagnostic CT exams. The study was conducted using archived images and data from four San Francisco Bay Area hospitals.

The degree of variation in radiation delivered to patients sent to imaging for similar clinical indications was dramatic. On average, for the 11 study types the amount of radiation received during the highest-dose exam was 13 times greater than for the lowest-dose exam.

Smith-Bindman and colleagues examined the images, recorded all scanner settings used for the exams, and fed parameters into computer programs to gauge actual radiation exposure to patients. For each exam reviewed -- including different types of chest (including coronary), head and neck, and abdomen and pelvis exams -- at least 100 patients were included in the study.

Read more at Jeffrey Norris, UCSF Science Cafe