RADIOLOGICAL UNITS

The unit of exposure, the amount of energy deposited in tissue from being irradiated by a source, and the biological effects from being irradiated are described by three different units of measure. Both conventional and SI units of measure are regularly used. The unit of exposure is the Roentgen or Coulomb per kilogram. Deterministic clinical effects from absorbed dose are described in RAD or Gray. Equivalent dose from different types of radiation is described in REM or Sievert.9,10 Determining equivalent dose applies to stochastic effects and is dependent on type of ionizing radiation.

In the immediate aftermath of an incident, healthcare providers will see radiation exposure measured in Roentgen (R) when using detectors and discussion of Acute Radiation Syndrome (ARS) and Cutaneous Radiation Syndrome (CRS), based on dose received in RAD and Gray. This information is summarized in Table 3. It is extremely important to confirm the unit the detector utilizes, particularly the prefix as milli (m) and micro (µ) are often confused or even omitted when relaying dose and/or dose rate.