Production of sup(99m)Tc-labelled iron oxide aerosols for human lung deposition and clearance studies

Radiolabeled aerosols used in human lung deposition and clearance studies require nontoxic particles firmly tagged with low dose isotopes. An iron oxide sol was prepared by deionizing a ferric nitrate solution. A rapid and efficient method of labeling with sup(99m)Tc was developed. Initial binding approached 100% and product yields exceeded 90% for iron oxide concentrations greater than 1 mg ml-1. Sup(99m)Tc leakage from both iron oxide aqueous colloids and monodisperse particles was assayed by pressure dialysis. Over 24 h, aqueous colloidal leaching in saline and simulated lung fluid was less than 2%, whereas particle leaching was 15.4% and 6.4% respectively. (author)