Development and Use of Biokinetic Models for Incorporated Radionuclides

Biokinetic models play a central role in the dosimetry of internally deposited radionuclides. The modelling approach presented in ICRP Publication 2 used single exponential retention curves to calculate doses to possible target or critical organs. In ICRP Publication 30, major advances were made in the amount of detail and the accuracy of the models used to quantify the distribution, retention, and dosimetry of radionuclides in groups of tissues and organs containing the highest concentrations and receiving the highest radiation dose rates. A key advantage of the ICRP 30 approach was the ability to calculate and account for the dose received by all the highest exposed organs and tissues, not just a critical organ. A number of models published by the ICRP since the ICRP 30 series have striven for additional physiological realism. The structures of these models make it possible to incorporate a broad range of physiological information and to adjust specific parameters as a function of age. In this way, the use of these models has been extended from occupational exposures to environmental exposures of people of different ages. This move to increased physiological realism mirrors the changes that have occurred or will soon occur in other ICRP dosimetry models.