Units, of exposure

Several additional terms related to the absorption of x-radiation require definition energy of a x-ray photon is properly represented in joules but more conveniently reported in eV fluence is the sum of the energy in a unit area intensity or flux is the fluence per unit time and the exposure is a measure of the number of ions produced in a mass of gas. The unit of exposure in medicine is the Rn ntgen, R, defined as the quantity of radiation required to produce 2.58 x C/kg of air. The absorbed dose for a tissue is a measure of energy dissipated per unit mass. The measure of absorbed dose most... 

Qi — The upper-bound estimate of the low-dose slope of the dose-response curve as determined by the multistage procedure. The q, can be used to calculate an estimate of carcinogenic potency, the incremental excess cancer risk per unit of exposure (usually pg/L for water, mg/kg/day for food, and pg/m for air). 

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. 

Working Level Month (WLM)—A unit of exposure to radon daughters corresponding to the product of the radon daughter concentration in Working Level (WL) and the exposure time in nominal months (1 nominal month =170 hours). Inhalation of air with a concentration of 1 WL of radon daughters for 170 working hours results in an exposure of 1 WLM. 

Symbolized by R, the roentgen is the international unit of exposure dose. It is equal to that quantity of radiation that will produce a charge of 2.58 x 10 coulombs on all the ions of one sign, when all the electrons released in a volume of air (at STP) of a mass of one kilogram are completely stopped. 

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