What are the measurements of radiation and radiation dose?
Traditionally in the United States, rads and rems are used to measure absorbed dose and dose equivalent. Rads measure energy deposition per unit mass (100 ergs/g) and are independent of the material in which the radiation deposits its energy. Rems modify a dose to reflect its affect on a person. In fact rem originally stood for Radiation Equivalent in Man. The factor that multiplies a dose in rads to get the dose equivalent in rems is called the quality factor or Q. For gamma and beta radiation the Q is 1, for neutrons of unknown energy the Q is 10, and for alpha particles the Q is 20. Although, it should be noted that alpha particles emitted from outside the body are stopped by the dead layer of skin and essentially give no radiation dose, and it is only when alpha materials are inhaled or are otherwise taken into the body that alpha radiation is a problem. In other countries, units of Sieverts and Grays are used. A Sievert is 100 rems and one Gray is 100 rads.
