Controlling radiation exposure in interventional cardiology.

T he idiom " double-edged sword " describes the use of ionizing radiation in the field of medicine. Medical radiation from x-rays and nuclear medicine is the largest man-made source of radiation in Western countries and although it has benefited patients there is an associated liability or health risk that is unavoidable. A 2009 report by the National Council on Radiation Protection and Measurements found the total exposure to ionizing radiation in the United States has almost doubled during the past 2 decades. 1,2 This finding is to a large part attributable to the rise in cardiovascular diagnostic and therapeutic interventions, which are responsible for ≈40% of the cumulative effective dose of radiation to the population exclusive of radiation oncology. 3,4 As a field, interventional cardiology has flourished with the advent of technology to allow the treatment of more complex coronary artery disease and expansion in the arenas of endovascular and structural heart disease. With our success comes a heavy burden, that of awareness of the hazards of radiation, appropriate use and documentation of exposure, and constant effort to achieve the lowest achievable exposure necessary to care for an individual patient. There are various measurements of radiation exposure; therefore , familiarity with the nomenclature is required to understand the risks. The effective dose, measured in millisieverts (mSv), is a whole-body dose independent of where the radiation is delivered and permits comparisons among exposed individuals. For reference, background exposure to an individual in the United States is ≈3 mSv/y. Cardiac radionuclide studies have an exposure range of 15 to 35 mSv and invasive diagnostic cardiac procedures generally 1 to 10 mSv, whereas interventions can have substantially higher exposure. Most modern catheterization laboratory equipment measures air kerma, which is the energy delivered at a certain point in space (unit of measure is gray [Gy]) to assess hazard at a particular location, and kerma air product or dose area product, which takes into account the area of the x-ray beam (Gy×cm 2). The effective dose can be roughly estimated by multiplying the dose area product by 0.26. Deterministic risks of radiation are well described. There are known exposure thresholds for tissue injury that are relevant to patients, such as skin erythema (≈2 Gy) and permanent skin injury (≈5 Gy). For operators, the eye lens is susceptible and cataracts risk increases with acute exposure as low as 0.1 Gy and chronic exposure of 5 …