sievert

(Sv)

   an SI unit used for measuring the effective (or "equivalent") dose of radiation received by a human or some other living organism. Various kinds of radiation have different effects on living tissue, so a simple measurement of dose as energy received, stated in grays or rads, does not give a clear indication of the probable biological effects of the radiation. The equivalent dose, in sieverts, is equal to the actual dose, in grays, multiplied by a "quality factor" which is larger for more dangerous forms of radiation. An effective dose of one sievert requires 1 gray of beta or gamma radiation but only 0.05 gray of alpha radiation or 0.1 gray of neutron radiation. One sievert equals 100 rem. The sievert is a large unit, so radiation doses are often measured in millisieverts (mSv). The unit honors the Swedish physicist Rolf Sievert (1898-1966), who worked over many years to measure and standardize the radiation doses used in cancer treatment.