Dosimetric Optimization of Postproduction Neutron-Activated Erbium-170-Oxide-Enriched Pancreatin

The feasibility of postproduction neutron activation of an enteric-coated pancreatic enzyme preparation for in vivo gastric emptying studies has been investigated. During production of this multicomponent preparation, small amounts of 170Er-enriched erbium oxide, suitable for neutron activation, were added. Postproduction neutron irradiation of the labeled preparation resulted in short-lived (7.5 hr) gamma-emitting 171Er. Various radiocontaminants, however, are produced also. Because of variations in activation yields, half-lives, decay schemes and radiotoxicities, both major and trace constituents were considered for optimization of both dosimetry and the diagnostic measurement. Conditions were optimized for the best ratio of the committed dose equivalent due to 171Er to the total committed dose equivalent. The results show that postproduction neutron activation of a 170Er-enriched multicomponent preparation can be performed safely within the guidelines set by the WHO for experiments in humans involving radioactive materials.