Radiation and Radiation Risk

Context and Perspective

Although the risk per single CT scan is small, given the enormous numbers of CT scans performed, this risk is neither small nor dismissible. Approximately 60 to 65 million CT scans of all types were performed in the United States in 2006 —one per five citizens. The rate is increasing at 10% to 25% per year. Approximately two thirds of a billion CT scans have been performed in the United States alone since 1980. It has been established that over the last several decades, the amount of radiation exposure per person per year has increased conspicuously (600% in 3 decades), due mainly to the proliferation of CT scanning. Medical imaging procedures, especially tomographic imaging and nuclear medicine, are important sources of exposure to ionizing radiation.

Thus, even if the risks of CT scanning are small per scan, given the sheer volume of scans, the risk does translate into events. It is estimated, although not yet proved, that approximately 0.4% of all cancer in the United States may be attributed to CT scanning. Radiation risk should be responsibly and knowledgeably addressed whenever cardiac CT (CCT), coronary computed tomographic angiography (CTA), electron beam CT (EBCT), or other type of CT scanning is being considered or when nuclear testing or any form of imaging that entails radiation exposure to patients is an option.

The actual risks of medical radiation are neither tabulated nor known; currently, they have been estimated only by models that understandably engender some controversy. The models are based on data from nuclear blasts over Hiroshima and Nagasaki, from the Chernobyl nuclear reactor leak, and from exposure of individuals engaged in nuclear testing for medical purposes, as well as from patients exposed to radiation. Unfortunately, more real data pertaining to emerged cancer risks in patients undergoing CT scanning for reasons other than cancer have never been gathered. It is a sobering fact that much medical diagnostic testing entails radiation exposure equivalent to what occurred at the periphery of Hiroshima and Nagasaki, whose populations, followed for half a century, did exhibit excessive rates of cancer.

Tubiana has understandably stated that overestimation of risk “may deprive patients of beneficial examinations.” Some of the controversy itself is controversial, such as objection to the linear no-threshold risk of radiation.

Few data have been tabulated to substantiate so many statements about CT scanning and the manner and the matter of its use. The net effect of CT scanning is simply the summation of the reduction of morbidity and mortality of lives by useful clinical diagnosis guiding successful therapy, and the incurred morbidity and mortality from radiation, contrast media, and other complications attributable to its use.

Radiation and Risk Overview