The röntgen (roentgen) equivalent in man (or mammal^[1]) 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 factor rW=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 (Sv); 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"^[2] by the style guide of the U.S. National Institute of Standards and Technology for authors of its publications.^[3] See radiation poisoning for a more complete analysis of effects of various dosage levels.

A dose of under 100 rems is subclinical and will produce nothing other than blood changes. 100 to 200 rems will cause illness but will rarely be fatal. Doses of 200 to 1000 rems will likely cause serious illness with poor outlook at the upper end of the range. Doses of more than 1000 rems are almost invariably fatal.^[4]

[edit] See also

• Radiation poisoning
• Rad (unit)
• Gray (unit)
• Space radiation

[edit] References

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