Which units are used to express occupational dose equivalents in radiologic protection?

• A. Rem and Sievert
• B. Rad and Gray
• C. Curies and Becquerels
• D. Rutherford and rem

Answer: (A)

Occupational dose equivalents are expressed in units that reflect the potential biological effect of radiation in a person. Those units are rem and sievert. The dose equivalent combines the absorbed dose with a quality factor that accounts for the type of radiation, giving a measure of the potential for harm. Historically, the unit used was the rem, but the modern SI unit is the sievert. Since 1 sievert equals 100 rem, the same exposure can be described in either unit depending on the system used. For example, an exposure of 0.01 sievert corresponds to 1 rem.

Other units mentioned in radiology relate to different quantities: absorbed dose is measured in grays (or rads, with 1 Gy = 100 rad), which does not account for biological effect on its own. Activity is measured in curies or becquerels, which describe the rate of radioactive decay, not dose. Therefore rem and sievert are the appropriate units for expressing occupational dose equivalents.