As part of the revision of the Reference Man model of the International Commission on Radiological Protection (ICRP), we have reviewed and reanalyzed available data on blood flow and in previous publications have proposed reference values for total and regional blood volumes, total cardiac output, and the distribution of cardiac output. In this paper we unify these proposed features of the revised Reference Man within the framework of a dynamic blood circulation model and show how the model can be used to predict the distribution of decays of short-lived radionuclides after injection or absorption into blood. The total blood volume is partitioned into the blood contents of 24 separate organs or tissues, right heart chambers, left heart chambers, pulmonary circulation, arterial outflow to the systemic tissues (aorta and large arteries), and venous return from the systemic tissues (large veins). As a compromise between physical reality and computational simplicity, the circulation of blood is viewed as a system of first-order transfers between blood pools, but outflow from any given pool is delayed during the first pass of material through the circulation with the delay time depending on the mean transit time across the pool. The model can be used to predict the movement and gradual dispersal of a bolus of material in the circulation after intravascular injection. In contrast to the treatment of the circulation in ICRP Publication 53, Radiation Dose to Patients from Radiopharmaceuticals, the present model allows consideration of incomplete, tissue-dependent extraction of material during passage through the circulation and return of material from tissues to plasma.

Estimates of regional blood volumes (BVs) in man are needed for the dosimetry of radionuclides that decay in the circulation to a significant extent. The tabulation of regional BVs in Publication No. 23 of the International Commission on Radiological Protection (ICRP Reference Man document) may be the best available for dosimetric applications but is not consistent with current information for some organs and does not address some important blood pools. The purpose of this paper is to suggest an improved set of reference values for regional BVs in adult humans. The total blood volume (TBV) is viewed as comprising 22 separate pools, including several pools not addressed in the ICRP Reference Man document. Values suggested here for brain, liver, skin, active marrow, inactive marrow, and bone differ by at least a factor of two from those given for ICRP Reference Man.

During the decade following the Chernobyl accident, the International Commission on Radiological Protection (ICRP) developed dose coefficients (doses per unit intake) for ingestion or inhalation of radionuclides by members of the public. The level of uncertainty in those coefficients varies considerably from one radionuclide to another, due largely to differences in the level of understanding of the biological behaviour of different elements in the human body. This paper is the first in a series that examines the sources and extent of uncertainties in the ICRP's biokinetic and dosimetric models for members of the public and the dose coefficients derived from those models. The present paper describes the different types of information generally used to develop biokinetic models for radionuclides, the main sources of uncertainty associated with each type of information, and the approach used in subsequent papers in this series to quantify the uncertainties in biokinetic and dosimetric estimates.

Although whole-body retention of Rb in humans has been characterized reasonably well, current biokinetic models for Rb do not provide detailed or accurate descriptions of the time-dependent distribution of this element within the body. In this paper we construct a physiologically descriptive biokinetic model that closely tracks the movement of Rb from the time of intake until virtually all of the ingested or injected quantity has been removed from the body. The selection process for model parameter values is described for a reference adult male, but we demonstrate how the model may be applied to non-reference humans, including young children. It is shown that the model accurately predicts long-term retention of Rb in both sexes and in different age groups and depicts changes with time in the internal distribution of Rb with sufficient accuracy to be suitable for dosimetric estimates even for the short-lived isotope 82Rb (T 1/2 = 75 s).

Recent efforts to incorporate greater anatomical and physiological realism into biokinetic models have resulted in many cases in mathematically complex formulations that limit routine application of the models. This paper describes an elementary, computer-efficient technique for implementing complex compartmental models, with attention focused primarily on biokinetic models involving time-dependent transfer rates and recycling. The technique applies, in particular, to the physiologically based, age-specific biokinetic models recommended in Publication No. 56 of the International Commission on Radiological Protection, Age-Dependent Doses to Members of the Public from Intake of Radionuclides.