Cancer risks associated with external radiation from diagnostic imaging procedures

Abstract

The 600% increase in medical radiation exposure to the US population since 1980 has provided immense benefit, but increased potential future cancer risks to patients. Most of the increase is from diagnostic radiologic procedures. The objectives of this review are to summarize epidemiologic data on cancer risks associated with diagnostic procedures, describe how exposures from recent diagnostic procedures relate to radiation levels linked with cancer occurrence, and propose a framework of strategies to reduce radiation from diagnostic imaging in patients. We briefly review radiation dose definitions, mechanisms of radiation carcinogenesis, key epidemiologic studies of medical and other radiation sources and cancer risks, and dose trends from diagnostic procedures. We describe cancer risks from experimental studies, future projected risks from current imaging procedures, and the potential for higher risks in genetically susceptible populations. To reduce future projected cancers from diagnostic procedures, we advocate the widespread use of evidence-based appropriateness criteria for decisions about imaging procedures; oversight of equipment to deliver reliably the minimum radiation required to attain clinical objectives; development of electronic lifetime records of imaging procedures for patients and their physicians; and commitment by medical training programs, professional societies, and radiation protection organizations to educate all stakeholders in reducing radiation from diagnostic procedures.

FIGURE 1

US Annual Per Capita Effective Radiation Dose in Millisieverts (mSv) From Various Sources for 1980 and 2006. The source for estimated annual per capita natural background exposure of 2.4 mSv in both time periods is the 1988 United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) report. The source for estimated annual per capita total radiation exposure of 3.0 mSv for 1980 is National Council on Radiation Protection and Measurements (NCRP) Report No. 93, published in 1987. The estimated annual per capita total radiation exposure of 5.6 mSv for 2006 is the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 2008 report. CT indicates computed tomography; F&IF, fluoroscopy and interventional fluoroscopy. Reprinted with permission from Mettler FA Jr, Bhargavan M, Faulkner K, et al. Radiologic and nuclear medicine studies in the United States and worldwide: frequency, radiation dose, and comparison with other radiation sources-1950-2007. Radiology. 2009;253:520-531.

FIGURE 2

Variation in Estimated Effective Radiation Dose in Millisieverts (mSv) Associated With 11 Common Types Of Diagnostic Computed Tomography Studies Performed on 1119 Adult Patients in 4 San Francisco Bay Area Hospitals. Shown are the median values, interquartile ranges, and minimum and maximum values. Reprinted with permission from Smith-Bindman R, Lipson J, Marcus R, et al. Radiation dose associated with common computed tomography examinations and the associated lifetime attributable risk of cancer. Arch Intern Med. 2009;169:2078-2086. ©2009 American Medical Association. All rights reserved.