Ionizing radiation Roentgen

Rep—Roentgen equivalent, physical A former unit of ionizing radiation equivalent to the dosage of 93 ergs absorbed per gram of tissue (93 erg/gm=0.93 rad). 

Roentgen (R)—A unit of exposure (in air) to ionizing radiation. It is the amount of x or gamma rays required to produce ions carrying 1 electrostatic unit of electrical charge in 1 cubic centimeter of dry air under standard conditions. Named after William Roentgen, a German scientist who discovered x rays in 1895. 

Lind (1961) defines radiation chemistry as the science of the chemical effects brought about by the absorption of ionizing radiation in matter. It can be said that in 1895, along with X-rays, Roentgen also discovered the chemical action of ionizing radiation. He drew attention to the similarity of the chemical effects induced by visible light and X-rays on the silver salt of the photographic plate. This was quickly followed by the discovery of radioactivity of uranium by Becquerel in 1896. In 1898, the Curies discovered two more radioactive elements—polonium and radium. 

Roentgen equivalent man (rem) The amount of ionizing radiation of any type that produces the same damage to humans as 1 roentgen of radiation. One rem = 1 roentgen equivalent physical (rep)/relative biological effectiveness (RBE). In the latest nomenclature, 100 rem = 1 Sievert (Sv). 

Roentgen equivalent physical (rep) One rep is equivalent to the amount of ionizing radiation of any type that results in the absorption of energy of 93 ergs/g, and is approximately equal to 1 roentgen of X-radiation in soft tissue. 

It is clear that, along with the discovery of x-rays in 1895, Roentgen also found the chemical action of ionizing radiation. He drew attention to the similarity of the photographic effect induced by light and x-rays. Application to medicine appeared very quickly, followed by industrial applications. However, this field of investigation remained nameless until Milton Burton, in 1942, christened it radiation chemistry to separate it from radiochemistry which is the study of radioactive nuclei. Historical and classical work in radiation chemistry has been reviewed by Mozumder elsewhere [1]. Here we will only make a few brief remarks. 

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. 

Lethal Concentration Amount of toxic substance in air which will likely cause death if inhaled. Lethal Dosage (1) Amount of a toxic substance which is likely to cause death when ingested. (2) Dose of ionizing radiation sufficient to cause death media lethal dose (MLD or LD50) is amount required to kill within a specified period of time (usually 30 days) half of the organisms exposed die LD50/30 for people is about 400-450 roentgens. 

REM (rem). A unit of dose equivalent in the field of radiation dosimetry. One rem equals the amount of ionizing radiation of any type which produces the same damage to humans as 1 roentgen of approximately 200 kilovolts x-radiation. (The unit is abbreviation of Roentgen Equivalent Man.)... 

Amounts of radioactivity are designated in terms of rads, roentgens, curies, disintegrations per unit time (minute), or counts per unit time (minute). The relationships between these various unit designations are summarized in Table 3-3. The first two units are rarely used except for measuring human exposure to ionizing radiation. It is worthy of emphasis... 

In SI units, exposure to ionizing radiation is expressed in coulombs per kilogram, the quantity of X- or gamma-radiation that produces ion pairs carrying 1 coulomb of charge in 1 kilogram of pure dry air. The former unit, the roentgen (R), is equal to 2.58 x KH Ckg-i. 

The standard unit for measuring the quantity of ionizing radiation is the roentgen (R). The roentgen is defined as a radiation flux that will produce 2.08 x 10 ion pairs per 0.001293 g (i.e., 1 cm ) of dry air at standard temperature and pressure. This number of ion pairs is equivalent to an energy of 84 erg. 

For evaluation of the risk of exposure to ionizing radiation in humans, the dose equivalent in rem (roentgen equivalent man) is defined as... 

REM is the dosage of any ionizing radiation that will cause biological injury to human tissue equal to the injury caused by one roentgen of x-ray or gamma ray dosage with 1 rem is equivalent to 0.01 Sievert (Sv). 

Rem—Roentgen equivalent man, the nnit of dose of any ionizing radiation that produces the same biological effect on human tissne as one roentgen of x-rays. 

REM (Roentgen Equivalent Man) - Is defined as the amount of any type of ionizing radiation that produces the same damage to man as 1 roentgen of about 200kV radiation. The quantity of such biological units is named dose equivalent. 

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