Ionizing radiation risks of cardiac imaging: estimates of the immeasurable.

For many decades, the search for a non-invasive visualization of the coronary arteries seemed to remain an unfulfilled promise to clinical cardiologists. Owing to the rapid refinements successfully implemented in computed tomography (CT) technology over the past few years, non-invasive imaging of coronary arteries is now not only feasible but also has become a reality in daily routine. This may—at least in part—have contributed to the fact that the number of CT scans performed in the USA has quadrupled since 1993.1 Although in a recent US survey CT and nuclear imaging accounted for just 21% of the total number of procedures, they resulted in >75% of the total cumulative effective radiation dose. We have witnessed an impressive six-fold increase in the radiation dose from medical imaging delivered per patient over the last 3 decades.1-2 Interestingly, half of all nuclear medicine procedures worldwide and 25% of all X-ray studies are performed in the USA (constituting 5% of the world's population), doubling and tripling that of other developed countries.