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CIPM, 2002: Recommendation 2
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Dose equivalent*

The International Committee for Weights and Mesures

considering that

  • the current definition of the SI unit of dose equivalent (sievert) includes a factor "N" (product of any other multiplying factors) stipulated by the International Commission on Radiological Protection (ICRP), and

  • both the ICRP and the International Commission on Radiation Units and Measurements (ICRU) have decided to delete this factor N as it is no longer deemed to be necessary, and

  • the current SI definition of H including the factor N is causing some confusion,
  • decides to change the explanation in the brochure "Le Système International d'Unités (SI)" to the following:

    The quantity dose equivalent H is the product of the absorbed dose D of ionizing radiation and the dimensionless factor Q (quality factor) defined as a function of linear energy transfer by the ICRU:

    H = Q · D

    Thus, for a given radiation, the numerical value of H in joules per kilogram may differ from that of D in joules per kilogram depending on the value of Q.

    The Committee further decides to maintain the final sentence in the explanation as follows:

    In order to avoid any risk of confusion between the absorbed dose D and the dose equivalent H, the special names for the respective units should be used, that is, the name gray should be used instead of joules per kilogram for the unit of absorbed dose D and the name sievert instead of joules per kilogram for the unit of dose equivalent H.

    Procès-Verbaux des Séances du CIPM (2002), p. 205


    See also J. Radiol. Prot., 2005, 25 97-100.