Kinetic analysis of Fe-52-labelled iron(III) hydroxide-sucrose complex following bolus administration using positron emission tomography

Kinetic analysis of a single intravenous injection of 100 mg iron(III) hydr oxide-sucrose complex (Venofer(R)) mixed with Fe-52(III) hydroxide-sucrose as a tracer was followed for 3-6 h in four generally anaesthetized, artific ially ventilated minipigs using positron emission tomography (PET), The amo unt of injected radioactivity ranged From 30 to 200 MBq. Blood radioactivity, measured by PET in the left ventricle of the heart. di splayed a fast clearance phase followed by a slow one. In the liver and bon e marrow a fast radioactivity uptake occurred during the first 30 min. foll owed by a slower steady increase. In the liver a slight decrease in radioac tivity uptake was noted by the end of the study. A kinetic analysis using a three-compartment (namely blood pool, reversible and irreversible tissue p ools) model showed a fairly high distribution volume in the liver as compar ed with the bone marrow. In conclusion, the pharmacokinetics of the injected complex was clearly vis ualized with the PET technique, The organs of particular interest, namely t he heart (for blood kinetics), liver and bone marrow could all be viewed by a single setting of a PET tomograph with an axial field of view of 10 cm. The half-life (T-1/2) of Fe-52 (8.3 h) enables a detailed kinetic study up to 24 h. A novel method was introduced to verify the actual Fe-52 contribut ion to the PET images by removing the interfering radioactive daughter Mn-5 2m positron emissions. The kinetic data fitted the three-compartment model, from which rate constants could be obtained for iron transfer from the blo od La a pool of iron in bone marrow or liver to which it was bound during t he study period. In addition, there was a reversible tissue pool of iran. w hich in the liver slowly equilibrated with the blood. to give a net efflux from the liver some hours after i.v. administration. The liver uptake showe d a relatively long distribution phase, whereas the injected iron was immed iately incorporated into the bone marrow. Various transport mechanisms seem to be involved in the handling of the injected iron complex.