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Absorbed dose is a dose quantity which is the measure of the energy deposited in matter by ionizing radiation per unit mass.Absorbed dose is used in the calculation of dose uptake in living tissue in both radiation protection (reduction of harmful effects), and radiology (potential beneficial effects, for example in cancer treatment).
The rad is a unit of absorbed radiation dose, defined as 1 rad = 0.01 Gy = 0.01 J/kg. [1] It was originally defined in CGS units in 1953 as the dose causing 100 ergs of energy to be absorbed by one gram of matter. The material absorbing the radiation can be human tissue, air, water, or any other substance.
The absorbed dose, measured in rad, is a better indicator of ARS. [3]: 592–593 A rem is a large dose of radiation, so the millirem (mrem), which is one thousandth of a rem, is often used for the dosages commonly encountered, such as the amount of radiation received from medical x-rays and background sources.
Radiation dosimetry in the fields of health physics and radiation protection is the measurement, calculation and assessment of the ionizing radiation dose absorbed by an object, usually the human body. This applies both internally, due to ingested or inhaled radioactive substances, or externally due to irradiation by sources of radiation.
In 1953 the International Commission on Radiation Units and Measurements (ICRU) recommended the rad, equal to 100 erg/g, as the unit of measure of the new radiation quantity absorbed dose. The rad was expressed in coherent cgs units. [5] In 1975 the unit gray was named as the SI unit of absorbed dose. One gray is equal to 1 J/kg (i.e. 100 rad).
The absorbed dose will depend on the type of matter which absorbs the radiation. [4] For an exposure of 1 roentgen by gamma rays with an energy of 1 MeV , the dose in air will be 0.877 rad , the dose in water will be 0.975 rad, the dose in silicon will be 0.877 rad, and the dose in averaged human tissue will be 1 rad. [ 10 ] "rad" stands for ...
The absorbed dose also plays an important role in radiation protection, as it is the starting point for calculating the stochastic health risk of low levels of radiation, which is defined as the probability of cancer induction and genetic damage. [8]
"The quantity dose equivalent H is the product of the absorbed dose D of ionizing radiation and the dimensionless factor Q (quality factor) defined as a function of linear energy transfer by the ICRU" H = Q × D [4] The value of Q is not defined further by CIPM, but it requires the use of the relevant ICRU recommendations to provide this value.