Investigation of two new [ 99mTc]Tc-HEDP preparations that can be expected to give a better lesion-to-normal-bone uptake ratio when used as bone scanning agents

Two new potential bone scanning agents have been prepared and characterized. One of the agents, Tc(Sn,pH 12)-HEDP, is prepared at pH 12 (and subsequently neutralized). The other agent, Tc(Fe)-HEDP, is prepared by reducing [ 99mTc]TcO 4 − by a mixture of Fe(II) and Sn(II). From ion exchange chromatography on Aminex A-28 it appeared that the proportion of early eluting components of the two new agents is larger than that of the usual agent, Tc(Sn,pH 7.4)-HEDP. The stabilities on storage, and in serum, of the three agents appeared to be equally good. The adsorption on tri-calciumphosphate of Tc(Fe)-HEDP and Tc(Sn,pH 7.4)-HEDP was determined at several values of concentrations of Sn(II) and HEDP. Further, the influence of the pH (1–12) during reduction of [ 99mTc]TcO 4 − by Sn(II) on the adsorption of the agent on tri-calciumphosphate (at a fixed pH of 7.4) was investigated. It appeared that the adsorption of Tc(Sn,pH 12)-HEDP and Tc(Fe)-HEDP is less than that of Tc(Sn,pH 7.4)-HEDP. It is argued that this result points to a better efficiency in lesion detection of the two new agents, compared to the usual one.