The risk of exposure to ionizing radiation is also an imaging cost. The expanded use of computed tomography, with its associated increase in radiation exposure compared to plain radiography, has led to renewed concerns about the total dose of ionizing radiation and the potential for increased rates of cancer, which can occur soon after exposure or up to decades later. This concern is especially high for the pediatric population because their post-exposure life span is greater and they have a higher number of dividing cells  than adults.⁵³CT scanning is estimated to account for about 10% of diagnostic radiology examinations, but is responsible for up to two-thirds of the total radiation dose delivered to the population.⁵⁴ There is no current consensus on whether there is such a thing as a "safe dose" or what constitutes a reasonable exposure threshold.⁵³ While specific guidelines have not been published, the International Commission on Radiological Protection is expected to publish guidelines in 2007 which are anticipated to include recommendations for limiting exposure via medical x-ray sources.⁵⁵The awareness level concerning radiation dose and possible risks associated with CT scans is low among radiologists (47%), emergency physicians (9%), and patients (3%), based on results of a survey by Lee et al published in 2004.⁵⁶

Another concern when considering imaging techniques is the risk for development of contrast-induced nephropathy, which is defined as the elevation of serum creatinine more than 0.5 mg/dL within three days of contrast media administration. Numerous risk-reduction strategies have been investigated. Adequate intravenous volume expansion with isotonic crystalloid, beginning 3 to 12 hours before the procedure and continuing for 6 to 24 hours afterward, can lessen the probability in high risk patients. It is not known whether oral hydration is effective. According to the Contrast-Induced Nephropathy Working Panel, of the pharmacologic agents that have been suggested, theophylline, statins, ascorbic acid, and prostaglandin E1 deserve further investigation. N-acetylcysteine has not been shown to be consistently effective. Diuretics are considered to be potentially detrimental. Nephrotoxic drugs, such as non-steroidal antiinflammatory agents and aminoglycosides, should be withdrawn before contrast administration.⁵⁷

Another approach to the reduction of the risk for development of contrast-induced nephropathy is through the use of an isosmolar contrast medium, such as iodixanol (Visipaque). A recently published metaanalysis of 16 double-blind studies including 2727 patients found that iodixanol was associated with smaller rises in serum creatinine and lower rates of contrast-induced nephropathy than low-osmolar contrast media.⁵⁸