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FIGURE 90.10 Types of radiation Alpha particles have a 2+ electrical charge and a large mass (two protons and two neutrons) Beta particles have a single negative charge and a small mass (one electron) Charged particles not penetrate the body very well Because of their larger mass and charge, alpha rays cannot penetrate even the dead layers of skin 239Pu (plutonium), an alpha emitter, is a biologic hazard only when it is inhaled, ingested, or otherwise introduced into the body Beta particles (“beta rays”) are more penetrating and in high doses can severely damage the skin Beta rays cannot damage the deep radiation-sensitive organs in the body unless the radioactive source is incorporated into the body At the Chernobyl nuclear plant accident in Ukraine, some of the firefighters had severe skin damage due to intense beta particle exposure, which contributed to their deaths The words “radiation” and “radioactive” are often confused An atom that is unstable spontaneously gives off energy as radiation and is therefore radioactive In contrast, an x-ray machine cannot spontaneously give off radiation: an external power source is needed Therefore, an x-ray machine is not radioactive A patient who has been exposed to radiation does not become radioactive Patients emit radiation only if they have radioactive atoms on them (external contamination) or within them (internal contamination) Amounts of Radiation Geiger counters can measure amounts of radiation far below levels that have a measurable biologic effect They are inexpensive and readily available in the nuclear medicine department at most hospitals Because a Geiger counter can detect and quantify the radiation exposure rate immediately, detecting and managing a radiation hazard may be easier than detecting and managing biologic or chemical hazards Radiation exposure is commonly measured in three different units in the United States: roentgen, rad, and rem However, new international units are being used by regulatory and professional organizations ( Table 90.10 ) The roentgen (R) is a measure of radiation exposure in air Absorbed dose in an organ is measured in grays (Gy); Gy is equal to 100 rads Effective dose, in sieverts (Sv), is a measure of overall risk to an individual when the irradiation is weighted for the sensitivity of each organ to late effects of radiation One sievert is equal to 100 rems Quantity of radioactivity is measured by becquerels (Bq), defined as atomic disintegration per second The former unit, the curie (Ci), is equal to 3.7 × 1010 Bq, and mCi is equal to 37 MBq TABLE 90.10 INTERNATIONAL RADIATION UNITS Metric Definition Exposure Roentgen, R R = 2.58 × 10− C/kg air Absorbed dose Gray, Gy Gy = J/kg Effective dose Gy = 100 rads Sievert, Sv Sv = J/kg, weighted for tissue sensitivity Quantity of radioactivity Sv = 100 rems Becquerel, Bq Curie, Ci Bq = disintegration/s Ci = 3.7 × 1010 Bq mCi = 37 MBq Note: C = coulomb TABLE 90.11 COMMON RADIATION DOSES Sources Effective dose Roundtrip intercontinental air flight 20–30 μSv Chest radiograph Living in brick house 50–100 μSv 0.20 μSv/yr Natural radiation Angiography mSv/yr 10 mSv Abdominal computed tomographic scan 10–30 mSv We are exposed to about mSv of radiation each year from natural sources During a 70-year lifetime, a person’s total radiation exposure from natural sources will be more than 200 mSv, with no known measurable biologic effect Typical radiation exposures encountered during life and in medicine are listed in Table 90.11 Children generally have a higher relative risk of cancers (leukemia and thyroid, skin, breast, and brain cancer) following radiation exposure compared to adults, likely due to the increased radiosensitivity of their developing organs Also, since children are shorter than adults, they may be exposed to radioactive material deposited on the ground In addition, their shorter body diameters can lead to higher-dose exposures to their internal organs The hazard posed by a radionuclide depends on its quantity, decay scheme, the energies of its emissions, its half-life, and length of exposure For example, a radionuclide that decays by emitting only alpha particles is not a hazard if kept outside the body, since alpha particles cannot penetrate even the dead layers of the skin However, some radionuclides (e.g., 131Iodine) that are readily absorbed by the body and/or are concentrated by an organ can be a hazard in small amounts Although the radiation doses to personnel involved in the care of a victim contaminated by radioactive material are likely to be very small, simple protective measures should be employed to minimize the doses There are three methods of protection from radiation exposure: minimizing time of exposure, maximizing distance from the material to the extent practical, and using shielding as appropriate The amount of exposure received is directly proportional to the time spent near the source of radiation Distance is the most practical and effective method of reducing radiation exposure because the dose decreases by the square of the distance ( Fig 90.11 ) This is known as the inverse square law The lead aprons used in radiology departments, where the radiation comes from low-energy, scattered, nonparticulate radiation, are not generally useful in radiation event management Lead aprons not provide effective protection against the higher-energy radionuclide emissions likely to be encountered with radioactive contamination  ... that have a measurable biologic effect They are inexpensive and readily available in the nuclear medicine department at most hospitals Because a Geiger counter can detect and quantify the radiation... no known measurable biologic effect Typical radiation exposures encountered during life and in medicine are listed in Table 90.11 Children generally have a higher relative risk of cancers (leukemia