Quantities and Units in Radiation Protection

In its Publication No. 60, the International Commission on Radiological Protection (ICRP) introduced a new quantity, the equivalent dose in tissue, HT= (RWR.DT.R, where DT.R is the absorbed dose averaged over the tissue or organ, T, and WR is the radiation weighting factor. The latter depends on the incident radiation, i.e., the type and energy, but is independent of the tissue. On the other hand, a customarily defined quantity, the 'dose equivalent' is maintained (in particular the operational dose-equivalent quantities introduced in ICRU Report 39), but the relationship between the quality factor Q(L) and the linear energy transfer, L, has been redefined. In the case of neutrons, this procedure gives rise to an increase of the corresponding fluence to dose-equivalent conversion factors. The reasons for introducing these and the new tissue-weighting factor changes are discussed.