A physiological skeletal model for radionuclide and stable element biokinetics in children and adults.

A physiological skeletal model (PSM) is described that represents the skeletal uptake, retention, and clearance of both bone-surface-seeking and bone-volume-seeking radionuclides and stable elements. A key objective of the PSM is to model the higher skeletal growth and bone turnover in infants and children (compared to adults) in order to account for their greater uptake and cancer risk from bone-seeking contaminants such as lead and plutonium. The PSM is a compartmental model that allows for the incorporation of organic and inorganic material in the bone volume via quiescent bone surfaces, forming bone surfaces and the lacuno-canaliculi system. The model uniquely incorporates a tertiary phase of mineralization via bone fluids. The PSM's structural concepts and biokinetic parameters--such as realistic mass transfers, organ and tissue masses, and bone remodeling half-times--are selected mainly on the basis of physiological and anatomical criteria. For brevity, model parameter values are evaluated for adults only. The PSM is an improvement on existing skeletal models that are based more on compartment structures and pathways that rendered good fits to biokinetic data rather than on being anatomically and physiologically accurate.