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Risks of Radiation in Medical Imaging
Introduction
 Overview of Imaging Tests that use radiation, usually x-rays, are a valuable tool in diagnosis, but exposure to radiation has some risks (see also ), but most of them use low doses that are generally considered safe. For example, the radiation dose from one chest x-ray is comparable to 10 days of exposure to naturally occurring Sources of Radiation Exposure . However, exposure to radiation is cumulative, regardless of the interval between tests. This means that if people have many diagnostic tests that use low doses or several tests that use high doses, they may be exposed to a relatively large amount of radiation. The greater the cumulative dose, the greater the risk of cancer and sometimes tissue damage. Exposure to radiation is cumulative, regardless of the interval between tests. Imaging tests are only one source of exposure to radiation. Exposure to radiation in the environment (from cosmic radiation and natural isotopes—see Radiation Injury ) can be relatively high, particularly at high altitudes. When traveling by airplane, exposure to environmental radiation is increased. When planning diagnostic tests, doctors consider a person’s total (lifetime) exposure to radiation—the person’s total radiation dose. However, the potential benefit of a diagnostic test often outweighs the potential harms. In the United States, about 15% of all imaging tests are computed tomography (CT), but up to 70% of radiation exposure from all imaging tests comes from CT. The radiation dose for CT can be hundreds of times the dose for most x-rays. However, with newer techniques, doses for most CT scans can be much lower than with older techniques. Still, even when CT is done using older techniques, the risk is low for adults, and health is unlikely to be affected. However, the risk due to radiation exposure is higher in certain situations: During infancy During early childhood During pregnancy (particularly early) For certain tissues, such as lymphoid tissues (part of the Lines of Defense ), bone marrow, blood, the testes, the ovaries, and the intestines To minimize risks, doctors do the following: Use tests that do not require radiation, such as ultrasonography or magnetic resonance imaging (MRI), when possible Recommend diagnostic tests that use radiation, particularly high doses (as in CT) and particularly in young children, only when such tests are necessary Take precautions to limit radiation exposure during tests (for example, shielding vulnerable parts of the body, such as the thyroid gland or a pregnant woman’s abdomen) when possible Modern techniques and equipment have significantly lowered the radiation doses used in imaging tests. 