Editing Sievert (section)

===Protection quantities===
Protection quantities are calculated models, and are used as "limiting quantities" to specify exposure limits to ensure, in the words of ICRP, "that the occurrence of stochastic health effects is kept below unacceptable levels and that tissue reactions are avoided".<ref>ICRP publication 103, paragraph 112</ref><ref>ICRP publication 103, paragraph B50</ref><ref name="IAEACalibration">{{citation |title=Calibration of Radiation Protection Monitoring Instruments |series=Safety Reports Series 16 |quote=In 1991, the International Commission on Radiological Protection (ICRP) [7] recommended a revised system of dose limitation, including specification of primary ''limiting quantities'' for radiation protection purposes. These protection quantities are essentially unmeasurable |url=http://www-pub.iaea.org/MTCD/Publications/PDF/P074_scr.pdf |year=2000 |publisher=IAEA |isbn=978-92-0-100100-9}}</ref> These quantities cannot be measured in practice but their values are derived using models of external dose to internal organs of the human body, using [[Computational human phantom|anthropomorphic phantom]]s. These are 3D computational models of the body which take into account a number of complex effects such as body self-shielding and internal scattering of radiation. The calculation starts with organ absorbed dose, and then applies radiation and tissue weighting factors.<ref>ICRP publication 103, paragraph B64</ref>

As protection quantities cannot practically be measured, operational quantities must be used to relate them to practical radiation instrument and dosimeter responses.<ref>ICRP publication 103, paragraph B146</ref>