Dose equivalent (HT) means the product of the absorbed dose in tissue, quality factor, and all other necessary modifying factors at the location of interest. The units of dose equivalent are the rem and sievert (Sv). At the present time, rem is used in the U.S. while sieverts are used internationally. Eventually, the U.S. will adopt these international terms. The term “rem” (Roentgen equivalent man) is a special unit used for expressing dose equivalent. Some types of radiation produce greater biological effects for the same amount of energy imparted than other types. The rem is a unit that relates the dose of absorbed radiation to the biological effect of that dose. Therefore, to relate the absorbed dose of specific types of radiation, a “quality factor” must be multiplied by the dose in rad. To indicate the dose an individual receives in the unit rem, the word “rem” follows immediately after the magnitude, for example “50 rem”. One thousandth of a rem (millirem) is abbreviated “mrem”, and one millionth of a rem (microrem) is abbreviated “µrem”. The quality factor allows for the effect of higher energy deposition along particle tracks produced by various radiation types such as neutrons or alpha particles. For the xrays such as those currently utilized in the High Energy Mobile X-Ray Inspection Systems the quality factor is 1, meaning that 1 rad of absorbed dose results in 1 rem of dose equivalent. [1][2]


  1. US Customs & Border.
  2. "The 2007 Recommendations of the International Commission on Radiological Protection". Annals of the ICRP. ICRP publication 103 37 (2-4). 2007. ISBN 978-0-7020-3048-2. Retrieved 17 May 2012.