Röntgen equivalent man
Encyclopedia
Named after Wilhelm Röntgen (German scientist, 1845-1923), the roentgen equivalent in man (or mammal) or rem (symbol rem) is a unit of radiation
dose equivalent. It is the product of the absorbed dose
in rad
s and a weighting factor, WR, which accounts for the effectiveness of the radiation to cause biological damage.
An acute whole-body dose of under 50 rem is typically subclinical and will produce nothing other than blood changes. 50 to 200 rem may cause illness but will rarely be fatal. Doses of 200 to 1,000 rem will probably cause serious illness with poor outlook at the upper end of the range. Doses of more than 1,000 rems are almost invariably fatal. See radiation poisoning for a more complete analysis of effects of various dosage levels.
A rem is a large dose 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.
However, SI
units are increasingly encountered beyond academic, scientific, and engineering environments. The SI
unit of dose equivalent is the sievert
(Sv); conversion is straightforward, as 1 Sv = 100 rem:
The style guide of the U.S.
National Institute of Standards and Technology
strongly discourages the authors of NIST publications from expressing doses in rem, in favor of recommending the SI unit. For industries and firms that do not require the sole use of SI, however, the unit rem is often preferred.
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
dose equivalent. It is the product of the absorbed dose
Absorbed dose
Absorbed dose is a measure of the energy deposited in a medium by ionizing radiation per unit mass...
in rad
Rad (unit)
The rad is a unit of absorbed radiation dose. The rad was first proposed in 1918 as "that quantity of X rays which when absorbed will cause the destruction of the malignant mammalian cells in question..." It was defined in CGS units in 1953 as the dose causing 100 ergs of energy to be absorbed by...
s and a weighting factor, WR, which accounts for the effectiveness of the radiation to cause biological damage.
An acute whole-body dose of under 50 rem is typically subclinical and will produce nothing other than blood changes. 50 to 200 rem may cause illness but will rarely be fatal. Doses of 200 to 1,000 rem will probably cause serious illness with poor outlook at the upper end of the range. Doses of more than 1,000 rems are almost invariably fatal. See radiation poisoning for a more complete analysis of effects of various dosage levels.
A rem is a large dose 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
Background radiation
Background radiation is the ionizing radiation constantly present in the natural environment of the Earth, which is emitted by natural and artificial sources.-Overview:Both Natural and human-made background radiation varies by location....
sources.
Unit conversion
The rem and millirem are variant metric units in widest use among the American public, industry, and government.However, SI
International System of Units
The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...
units are increasingly encountered beyond academic, scientific, and engineering environments. The SI
International System of Units
The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...
unit of dose equivalent is the sievert
Sievert
The sievert is the International System of Units SI derived unit of dose equivalent radiation. It attempts to quantitatively evaluate the biological effects of ionizing radiation as opposed to just the absorbed dose of radiation energy, which is measured in gray...
(Sv); conversion is straightforward, as 1 Sv = 100 rem:
| 1.0000 rem | = | 1000.0 mrem | = | 1 rem | = | 0.010000 Sv | = | 10.000 mSv | = | 10000 µSv |
|---|---|---|---|---|---|---|---|---|---|---|
| 0.0010 rem | = | 1.0 mrem | = | 1 mrem | = | 0.000010 Sv | = | 0.010 mSv | = | 10 µSv |
| 100.0000 rem | = | 100000.0 mrem | = | 1 Sv | = | 1.000000 Sv | = | 1000.000 mSv | = | 1000000 µSv |
| 0.1000 rem | = | 100.0 mrem | = | 1 mSv | = | 0.001000 Sv | = | 1.000 mSv | = | 1000 µSv |
| 0.0001 rem | = | 0.1 mrem | = | 1 µSv | = | 0.000001 Sv | = | 0.001 mSv | = | 1 µSv |
The style guide of the U.S.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
National Institute of Standards and Technology
National Institute of Standards and Technology
The National Institute of Standards and Technology , known between 1901 and 1988 as the National Bureau of Standards , is a measurement standards laboratory, otherwise known as a National Metrological Institute , which is a non-regulatory agency of the United States Department of Commerce...
strongly discourages the authors of NIST publications from expressing doses in rem, in favor of recommending the SI unit. For industries and firms that do not require the sole use of SI, however, the unit rem is often preferred.
See also
- Gray (unit)Gray (unit)The gray is the SI unit of absorbed radiation dose of ionizing radiation , and is defined as the absorption of one joule of ionizing radiation by one kilogram of matter ....
- Banana equivalent doseBanana equivalent doseA banana equivalent dose is a whimsical unit of radiation exposure, informally defined as the additional dose a person will absorb from eating one banana...
- Health threat from cosmic raysHealth threat from cosmic raysThe health threat from cosmic rays is the danger posed by galactic cosmic rays and solar energetic particles to astronauts on interplanetary missions.Galactic cosmic rays consist of high energy protons and other nuclei with extrasolar origin...
- Orders of magnitude (radiation)Orders of magnitude (radiation)Recognized effects of higher acute radiation doses are described in more detail in the article on radiation poisoning. Although the International System of Units defines the sievert as the unit of radiation dose equivalent, chronic radiation levels and standards are still often given in unts of...