(December 14, 2009 - Insidermedicine)

The radiation dose and cancer risk associated with computed tomography (CT) scanning has been estimated in two studies published in the Archives of Internal Medicine.

According to the World Health Organization diagnostic imaging should be:

•    Developed as an integral part of national health care systems, according to the needs and social and economic structure of the country, region and area

•    Regulated by governments in accordance with international standards

•    Appropriate to the level of the health care system at which they are provided and to the therapeutic capabilities that are available.

Researchers out of the University of California at San Francisco conducted a retrospective, cross-sectional study of the radiation doses associated with 11 of the most common type of diagnostic CT scans performed on 1,119 consecutive adult patients. They found that radiation doses varied substantially among the different types of scans, from a median of 2-31 mSv. Even within a particular type of scan, doses varied by as much as 13-fold within and across institutions. The risk of cancer following a CT scan varied widely by type of scan, age, and sex.

In the second study, researchers out of the National Cancer Institute in Bethesda used risk models based on research performed by the National Research Council and organ-specific radiation doses obtained from a national survey to estimate the age-specific cancer risk of different types of CT scans. They used their results to estimate how many future cancers would likely be caused by all the CT scans delivered in 2007 in the U.S. Based on their calculations, about 29,000 future cancers could be related to CT scans performed that year. The largest contributors to future cancers would likely be from scans of the pelvis, abdomen, chest, and head. One-third of these future cancers would be due to scans performed on those aged 35 to 54.

We spoke with Dr. Rebecca Smith-Bindman, MD,  Department of Radiology, University of California, San Francisco  one of the principal investigators, who offered some further insight.

Today's research demonstrates that radiation exposure related to CT scanning is much higher than anticipated and highlights the need to explore measures to help reduce this exposure.