aa 56 To be rewritten. For the nonprofessional reader, the following is an expl ation of Of the swallowed medicine, three-quarters are eliminated ut one-quarter passes from the intestine into the circulation expressed. per gram of heart tissue. . >& r _ - the specific radiological meaning of the terms, exposure an dose. Very simply, the medical analogy would be this. A patient akes a spoonful of heart medicine -- radiologically considered, t t is his exposure. | _ ii N-6 absorbed by the heart -- that one-quarter is the dose. It For exposure to radiation per se, the unit is the roentge measured in air. For radionuclides (atoms which spontaneo and emit radiation), the units are the bequerel (Bq), equa atomic disintegration per second, or the curie (Ci), 3.7 x disintegrations per second. The microcurie (uCi) and the (pCi) are respectively 1 millionth of a curie, and 1 nilli microcurie (27 pCi equal 1 Bq). The units of dose are the rad (for any type of ionizi radiation: 100 ergs absorbed per gram of tissue); the re nd is ould be (R), ly decay to 1 QO 10 icocurie th of a (dose oO a '4 at Za equivalent in biological effect to 1 rad of standard radia ion). The particular point to remember about radiation dose is t t it is per gram of tissue. A whole-body dose of 100 rad means th t every gram (on average) received 100 rad; it does not mean that the entire body received 100 rad to be distributed throughout tissues. ron rnal dose g--. rom a source inside of the body, e.g., radioactive iodine due to the use of fallout-contaminated drinking water. Both exposure and dose are referred to as resulting external or internal sources. An external exposure or ext is the result of a radiation source outside of the body, e fallout contaminated soil. An internal dose would result In the case of radionuclides, we shall use the term w ole-body dose in the technical sense of committed effective dose eq ivalent. For a particular tissue, the tissue dose would be the comn tted dose equivalent. Such doses can be calculated for 1 year or 30 years, etc. Dose: in rads Dose equivalent: in rem Effective dose equivalent refers to the whole-body dose Committed effective dose equivalent: whole-body dose for nuclides in the body over a period of time fradio-