Biokinetic model of americium in the beagle dog

A biokinetic model of the systemic distribution of americium in the beagle dog is presented. The model is based on a previous biokinetic model of plutonium. The data sets used for the development of the model are the measurements of excreted activity (urine and feces) and organ burdens (skeleton, liver and other soft tissues). In developing the model, the part of the plutonium model representing the skeleton, which was based on histomorphometric and autoradiographic investigations, has not been modified with regard to both its structure (compartments for the trabecular/cortical volume, surface and marrow) and the remodelling rates. Other skeletal parameters such as the transfer rate from marrow to blood and the partitioning of transferred activity from the blood to trabecular/cortical surface and volume were optimized to describe the element-specific biokinetics in the skeleton. The model well describes the fractions of americium in the skeleton, liver and soft tissues and the total fraction excreted in urine and feces. Particularly it demonstrates the possibility of describing the behavior of americium in the skeleton with a model substantially analogous to the model of plutonium in humans. However it differs from the ICRP model of the skeleton with regard to the fundamental structure and the predictive power. This study will be the starting point for a future improvement of the currently used americium model for humans, particularly for the skeleton.