Effect of reaction conditions on preparations of Rhenium-188 hydroxyethylidene diphosphonate complexes

Rhenium-186 (Re-186) hydroxyethylidene diphosphonate (HEDP) has been shown to localize in metastatic foci within bone in a manner similar to Tc-99m bo ne seeking agents. Usually, in the preparation of diagnostic Tc-99m radioph armaceuticals, the concentration of Tc is at trace level (10(-8) M). Howeve r, large amounts of carrier are included in the preparation of Re-186 radio pharmaceuticals (10(-4) M), which may significantly affect the preparation of Re-HEDP. In this study, Re-188 was used as an Re tracer. The effects of pH and concentrations of Re carrier on the preparation of Re-HEDP were inve stigated. Re-188-Sn-HEDP was prepared by reconstitution of a kit of lyophil ized HEDP mixture, and tin chloride with a radioactive solution of perrhena te in saline. The total concentration of Re present in this work ranged fro m 10(-8) to 10(-3) M. The results showed that high labeling efficiency was obtained for each preparation, Although the chemical behaviors of the Re-18 8 HEDP complexes, with and without carrier, were similar, the biodistributi on patterns of carrier free Re-188 HEDP in rats were found to differ from t he biodistribution patterns of carrier-added Re-188 HEDP. NUCL MED BIOL 26; 4:455-459, 1999. (C) 1999 Elsevier Science Inc. All rights reserved.