Rads, rems, grays, sieverts, effective dose equivalents, roentgens — how can we cope with such terms?
The rad is the most “solid” unit of biological dose, because it contains no assumptions. A rad is defined as a certain amount of energy deposited by high-speed particles per gram of biological tissue (Introduction). Rads and roentgens are almost equivalent. The gray is the name for 100 rads. The rem is a unit which incorporates some evidence and some assumptions about the relative harmfulness of various high-speed particles, even when they deliver the same amount of energy per gram of biological tissue. In general, the rad and the rem are equivalent only when discussing gamma rays (or certain xrays). The sievert is the name for 100 rems. The effective dose equivalent, which is always expressed in rems or sieverts, incorporates many additional assumptions about biological consequences (details in Gofman 1995/96, pp.358-359). “Effective doses” and rad-doses are not directly comparable.
