Exposure of the human body to radiation carries certain risks. The biologic effects of ionizing radiation change the chemical makeup of cells, causing cell damage and mutation and promoting carcinogenesis. However, not all forms of radiation are equal in the potential for causing damage, and often no perceptible or long-lasting damage occurs. As a general rule, the higher the dose, as determined by the “strength” of the radiation and the duration of the exposure, the greater the risk.
Deterministic effects, such as erythema, nausea, fatigue, depressed sperm count, and temporary sterility, occur due to significant cell damage or death that occurs after a threshold amount of radiation has been exceeded. The severity of deterministic effects increases as the exposure dose increases. Stochastic effects, such as cancer, are associated with long-term low-level exposure to radiation. Low doses of radiation received over a period of time can lead to radiation-induced malignancy and genetic effects and are of most concern in diagnostic radiology. Because the embryo is most radiosensitive during the first trimester of pregnancy, special precautions must be taken to prevent or minimize radiation exposure to the pregnant uterus (Tables 10.2–10.5).
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