Operational quantities and new approach by ICRU.

The protection quantities, equivalent dose in a tissue or organ and effective dose, were developed by the International Commission on Radiological Protection (ICRP) to allow quantification of the extent of exposure of the human body to ionising radiation. These quantities are used for the implementation of limitation and optimisation principles. Body-related protection quantities are not measurable in practice. Therefore, the International Commission on Radiation Units and Measurements (ICRU) developed a set of operational dose quantities for use in radiation measurements for external exposure that can assess the protection quantities. The current ICRU operational quantities were defined more than 30 years ago. ICRU Report Committee 26 examined the rationale for the operational quantities, taking account of changes in the definitions of the protection quantities in ICRP's 2007 Recommendations. The considerations included the range of types and energies of particles contributing to exposure of workers and members of the public. ICRU Report Committee 26 investigated a set of alternative definitions for the operational quantities. The major change to the currently favoured set of quantities is redefinition of the operational quantities, from being based on doses at specific points in the ICRU sphere and soft tissue, to being based on particle fluence and conversion coefficients for effective dose and absorbed dose to the lens of the eye and local skin.