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Defining equation SI units Dimension Number of atoms N = Number of atoms remaining at time t. N 0 = Initial number of atoms at time t = 0 N D = Number of atoms decayed at time t = + dimensionless dimensionless Decay rate, activity of a radioisotope: A = Bq = Hz = s −1 [T] −1: Decay constant: λ
Dose and dose rate are used to measure different quantities [1] in the same way that distance and speed are used to measure different quantities. When considering stochastic radiation effects, only the total dose is relevant; each incremental unit of dose increases the probability that the stochastic effect happens. [ 4 ]
The dose values are divided by the maximum dose, referred to as d max, yielding a plot in terms of percentage of the maximum dose. Dose measurements are generally made in water or "water equivalent" plastic with an ionization chamber, since water is very similar to human tissue with regard to radiation scattering and absorption.
"The calculation of the committed effective dose equivalent (CEDE) begins with the determination of the equivalent dose, H T, to a tissue or organ, T. Where D T ,R is the absorbed dose in rads (one gray, an SI unit, equals 100 rads) averaged over the tissue or organ, T, due to radiation type, R, and W R is the radiation weighting factor.
The equivalent dose is calculated by multiplying the absorbed energy, averaged by mass over an organ or tissue of interest, by a radiation weighting factor appropriate to the type and energy of radiation. To obtain the equivalent dose for a mix of radiation types and energies, a sum is taken over all types of radiation energy dose. [1]
Effective dose is a dose quantity in the International Commission on Radiological Protection (ICRP) system of radiological protection. [1]It is the tissue-weighted sum of the equivalent doses in all specified tissues and organs of the human body and represents the stochastic health risk to the whole body, which is the probability of cancer induction and genetic effects, of low levels of ...
where D(f,z) is the dose at a given depth z and distance focus-detector f; and D(f,0) is the dose in air (z=0). TAR increases with increasing beam energy because higher energy radiation is more penetrating; TAR decreases with depth because of attenuation; TAR increases with field size due to increased scatter contribution
The collective effective dose, dose quantity S, is calculated as the sum of all individual effective doses over the time period or during the operation being considered due to ionizing radiation. [ 1 ] : paragraph 159 It can be used to estimate the total health effects of a process or accidental release involving ionizing radiation to an ...