Search results
Results from the WOW.Com Content Network
The roentgen equivalent man (rem) [1] [2] is a CGS unit of equivalent dose, effective dose, and committed dose, which are dose measures used to estimate potential health effects of low levels of ionizing radiation on the human body.
The roentgen or röntgen (/ ˈ r ɛ n t ɡ ə n,-dʒ ə n, ˈ r ʌ n t-/; [2] symbol R) is a legacy unit of measurement for the exposure of X-rays and gamma rays, and is defined as the electric charge freed by such radiation in a specified volume of air divided by the mass of that air (statcoulomb per kilogram).
W R is the radiation weighting factor defined by regulation. Thus for example, an absorbed dose of 1 Gy by alpha particles will lead to an equivalent dose of 20 Sv, and an equivalent dose of radiation is estimated to have the same biological effect as an equal amount of absorbed dose of gamma rays, which is given a weighting factor of 1.
The Röntgen equivalent physical (rep), introduced by Herbert Parker in 1945, [12] was the absorbed energetic dose to tissue before factoring in relative biological effectiveness. The rep has variously been defined as 83 or 93 ergs per gram of tissue (8.3/9.3 mGy ) [ 13 ] or per cc of tissue.
The equivalent dose is calculated by multiplying the absorbed energy, averaged by mass over an organ or tissue of interest, by a radiation weighting factor appropriate to the type and energy of radiation. To obtain the equivalent dose for a mix of radiation types and energies, a sum is taken over all types of radiation energy dose. [1]
Recognized effects of higher acute radiation doses are described in more detail in the article on radiation poisoning.Although the International System of Units (SI) defines the sievert (Sv) as the unit of radiation dose equivalent, chronic radiation levels and standards are still often given in units of millirems (mrem), where 1 mrem equals 1/1,000 of a rem and 1 rem equals 0.01 Sv.
The Röntgen equivalent physical or rep (symbol rep) is a legacy unit of absorbed dose first introduced by Herbert Parker in 1945 to replace an improper application of the roentgen unit to biological tissue. [1] It is the absorbed energetic dose before the biological efficiency of the radiation is factored in.
These measurements, ALI and DAC, are calculated values based on the dose an average employee working 2,000 hours a year may be exposed to. The current legal limit exposure in the United States is 1 ALI, or 5 rems. A rem, or roentgen equivalent man, is a measurement of absorption of radiation on parts of the body over an extended period of time ...