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In diagnostic radiology, the F-factor is the conversion factor between exposure to ionizing radiation and the absorbed dose from that radiation. In other words, it converts between the amount of ionization in air ( roentgens or, in SI units , coulombs per kilogram of absorber material) and the absorbed dose in air ( rads or grays ).
The roentgen or röntgen (/ ˈ r ɛ n t ɡ ə n,-dʒ ə n, ˈ r ʌ n t-/; [2] symbol R) is a legacy unit of measurement for the exposure of X-rays and gamma rays, and is defined as the electric charge freed by such radiation in a specified volume of air divided by the mass of that air (statcoulomb per kilogram).
See Weight for detail of mass/weight distinction and conversion. Avoirdupois is a system of mass based on a pound of 16 ounces, while Troy weight is the system of mass where 12 troy ounces equals one troy pound. The symbol g 0 is used to denote standard gravity in order to avoid confusion with the (upright) g symbol for gram.
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).
[19] Using data available at the time, the rem was variously evaluated as 83, 93, or 95 erg/gram. [20] Along with the introduction of the rad in 1953, the ICRP decided to continue the use of the rem. The US National Committee on Radiation Protection and Measurements noted in 1954 that this effectively implied an increase in the magnitude of the ...
The NRC's definition of dose equivalent is "the product of the absorbed dose in tissue, quality factor, and all other necessary modifying factors at the location of interest." However, it is apparent from their definition of effective dose equivalent that "all other necessary modifying factors" excludes the tissue weighting factor. [ 17 ]
The rep has variously been defined as 83 or 93 ergs per gram of tissue (8.3/9.3 mGy) [13] or per cc of tissue. [ 14 ] In 1953 the ICRU recommended the rad, equal to 100 erg/g as a new unit of absorbed radiation, [ 15 ] but then promoted a switch to the gray in the 1970s.
The NPL operates a graphite-calorimeter for absolute photon dosimetry. Graphite is used instead of water as its specific heat capacity is one-sixth that of water and therefore the temperature increase in graphite is 6 times higher than the equivalent in water and measurements are more accurate. Significant problems exist in insulating the ...