Roentgen equivalent in man

Radiation dose Level of exposure to radiation, expressed in units called Roentgen equivalents in man (rem) a dose of approximately 400 rem is fatal in 50% of cases when medical treatment is not available. No health effects are typically observed at doses below 10 rem. 

Rem (Roentgen equivalent in man) Special unit of any quantity expressed as a dose equivalent the dose equivalent in rems is equal to the absorbed dose in rads multiplied by the quality factor (1 rem = 0.01 Sv). 

The amoimt of radiation to which a person is exposed is measured in RADs or REM. RAD stands for radiation absorbed dose, and it measures the amount of radiation the body has received. One RAD equals 0.01 Joules/kg. REM stands for roentgen equivalent in man. For practical purposes a REM and a RAD are equal. Effects of varying whole-body doses of radiation on humans are listed in Table 5-1. 

The rem is a biological unit devised to account for health differences in various types of radiation. A 1-rad dose of ganuna radiation does not produce the same health effects as a 1-rad dose of alpha radiation. An additive unit was needed so that one unit of alpha had the same health effects as one unit of gamma. The devised unit is the rem, which stands for roentgen equivalent in man. One rem of any type of radiation has the same health effect as 1 roentgen of gamma rays or X-rays. The... 

Because of the differences in the behavior of the particles and rays produced by radioactive decay, both the energy dose of the radiation and its effectiveness in causing biological damage must be taken into account. The rem (which is short for roentgen equivalent for man) is defined as follows ... 

Rem a unit of radiation dosage that accounts for both the energy of the dose and its effectiveness in causing biological damage (from roentgen equivalent for man). 

Rem rem A measure of the energy absorbed in matter as a result of exposure to specific forms of radiation. This unit takes into account the fact that different forms of radiation produce different biological effects. 1 rem is equal to 1 rad times a factor dependent on the type of radiation, rem = roentgen equivalent for man. 

The exact value of the RBE varies with dose rate, total dose, and type of tissue affected. The product of the radiation dose in rads and the RBE of the radiation give the effective dosage in rem (roentgen equivalent for man) ... 

---