The röntgen (roentgen) equivalent in man or rem (symbol rem) is a unit of radiation dose. It is the product of the absorbed dose in röntgens (R) and the biological efficiency of the radiation. More precisely, assuming a radiation weighting factorrW=1, 1 rem equals 1.07185 röntgen. The conversion factor has been readjusted from 1 to 1.07185 so that 100 rem equal 1 sievert; the sievert is the recommended SI derived unit, and in many cases is the legally prescribed unit. A rem is a large amount of radiation, so the millirem (mrem), which is one thousandth of a rem, is often used for the dosages commonly encountered, such as the amount of radiation received from medical x-rays and background sources. Continued use of the rem is "strongly discouraged" [1] by the American National Institute of Standards and Technology. See radiation poisoning for a more complete analysis of effects of various dosage levels.
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