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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).
Fluorine-18 (18 F, also called radiofluorine) is a fluorine radioisotope which is an important source of positrons. It has a mass of 18.0009380(6) u and its half-life is 109.771(20) minutes. It decays by positron emission 96.7% of the time and electron capture 3.3% of the time.
Intensity of thermal radiation from the sun depends on view factor. In radiative heat transfer, a view factor, , is the proportion of the radiation which leaves surface that strikes surface . In a complex 'scene' there can be any number of different objects, which can be divided in turn into even more surfaces and surface segments.
The [18 F]FDG-6-phosphate formed when [18 F]FDG enters the cell cannot exit the cell before radioactive decay. As a result, the distribution of [18 F]FDG is a good reflection of the distribution of glucose uptake and phosphorylation by cells in the body. The fluorine in [18 F]FDG decays radioactively via beta-decay to 18 O −.
In most power plant scenarios, where the radiation environment is dominated by X-or gamma rays applied uniformly to the whole body, 1 rad of absorbed dose gives 1 rem of effective dose. [5] In other situations, the effective dose in rem might be thirty times higher or thousands of times lower than the absorbed dose in rad.
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).
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The ICRP 2007 standard values for relative effectiveness are given below. The higher radiation weighting factor for a type of radiation, the more damaging it is, and this is incorporated into the calculation to convert from gray to sievert units. The radiation weighting factor for neutrons has been revised over time and remains controversial.