Use as a Quantity for Dose Limits

When the entire body or parts of the body are irradiated externally, individual tissues and organs receive different absorbed doses. In order to relate the absorbed doses in tissue from non uniform irradiation to radiation detriment in humans, a quantity is required which reflects the relative effects of different types of radiation and the relative radiosensitivity of the irradiated organs and tissues. 

Contemporary radiation protection systems (ICRP, 1977a 1991 NCRP, 1987 1993) include dose limits expressed in such a quantity. To obtain the quantity, absorbed doses are first multiplied by a quality factor (ICRP, 1977a) or a radiation weighting factor (ICRP, 1991), selected for the type and energy of the radiation incident upon the body, yielding, respectively, the dose equivalent in the tissue (ICRP, 1977a) or equivalent dose in the tissue (ICRP, 1991). Therefore  

For low-LET radiation, the quality factor and radiation weighting factor have the value of one. Therefore, dose equivalent and equivalent dose have the same numerical value. 

---