Roentgen absorbed-dose

Radiation, roentgen absorbed doses (RADs), and roentgen-equivalent man (REM) ... 

Ra.dia.tlon Units. Units in use for activity of a radionucHde, ie, the curie, the roentgen (exposure to x and gamma rays), the rad (absorbed dose), and the rem (dose equivalent), should eventually be replaced by the becquerel (Bq), coulomb per kilogram (C/kg), gray (Gy), and the sievert (Sv), respectively. 

The former (non-SI) unit of dose equivalent was the roentgen equivalent man (rem), which was defined in the same way as the sievert but with the absorbed dose in rad thus, 1 rem = 10 2 Sv. 

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). 

Rem (acronym for roentgen-equivalent man) The unit of dose of ionizing radiation that produces the same biological effect as a unit of absorbed dose of ordinary x-rays. 

The Roentgen—A Unit of Radiation Exposure 378 Units of Absorbed Dose 379 Units of Dose Equivalent 379... 

The units for an absorbed dose are discussed in refs. 167 and 168. The fundamental unit, in terms of the energy absorbed per gram, is the rad, which is 100 erg. g and is equivalent to 6.24. eV g or 6.24x 10 xp eV. cm , where p is the density of the material. This unit is required when making dosimetric measurements. For X- or y-radiation, the exposure dose is used. The unit is one roentgen... 

Dose normally ev/gm. Usually calculated from quoted dose to air in same source assuming catalyst absorbs y as does H2O (55.2 x IQi ev/gm H2O, roentgen). Reactor doses frequently given only as integrated flux of neutrons, nvt (density x velocity x time) or cm-2. Charged particle doses sometimes given as flux and time or current and time. 

Conversion factor. A common conversion factor between exposure, absorbed dose, and dose equivalent is 1 R = 1 rad = 1 rem. This is an estimate that for radiation protection purposes is close enough (it actually over estimates the dose and therefore is a conservative estimate). The actual conversion is 1 R = 0.96 rem in tissue. Note that this method works only where the roentgen is defined - for photons of energy less that 3 MeV. When dealing with particulate radiation other methods must be used. 

Radiation exposure is called a Roentgen. This exposure is a measure of the ability of photons to produce ionization in air. Most commonly available instruments give the exposure rate in Roentgen per hour (R/hr). Absorbed dose (rad) is a measure of energy imparted per unit mass. One rad is the dose delivered to any material that receives 100 ergs of energy per gram. 

The third correction factor, which is the ratio of the adsorbed dose buildup factors in the sample and the dosimeter, is usually ignored, but is shown in this paper to be very important. The absorbed dose buildup factor is defined in this paper analogous to the dose buildup factor, a notation used when the unit roentgen was still the unit of radiation dose. This paper shows the magnitude of this third correction factor, which is caused by differences in gamma-ray attenuation coefficients and softening of the gamma-ray spectrum. As an illustrative example, the dose in different dosimeters is calculated as a function of the distance from a point isotropic cobalt-60 source in water. 

Roent- gen Relative biological effectiveness Radiation absorbed dose Roentgen equivalent man... 

Curie = A physical amount of radioactive material 1 Megacurie (MCI) = 1,000,000 Curies 1 Kilocurie (kCi) = 1,000 Curies 1 Millicurie (mCi) = 0.0001 Curies 1 Microcurie (uCi) = 0.000001 Curies Roentgen = Ionization per cm of dry air RAD = Radiation absorbed dose — Dosage REM = Biological effects... 

While a curie is a measure of the physical amount, the roentgen is a measure of the amount of ionization produced by a specific material. It is the amount of x-ray or gamma radiation that produces 2 billion ionizations in 1 cm of dry air. A RAD is the radiation-absorbed dose (roughly equal to a roentgen). The radiation equivalent man (REM), also roughly equal to a roentgen, is a term for how much radiation has been absorbed, or the biological effect of the dose. 

Mrad means a radiation-absorbed dose of 20 million Roentgens. 

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. 

Roentgen equivalent man— A unit of eqnivalent dose that relates the absorbed dose in human tissue to the effective biological damage of the radiation. 

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