In vitro stability of 99Tcm bone scan preparations from different manufacturers measured by various radiopharmaceutical parameters.

We have investigated the stability of 99Tcm-labelled kit preparations of the bone seeking agents methylene diphosphonate (MDP), hydroxymethylene diphosphonate (HDP) and dicarboxypropane diphosphonate (DPD). This was done by determining amounts of free 99Tcm pertechnetate under various experimental parameters. The radiopharmaceuticals were made with 100 and 300 mCi 99Tcm eluents and kept under the moderate condition of occasional inverting (1) or continuous rolling (2). Analysis took place 5 min, 2 h, 4 h and 6 h after preparation. In general free 99Tcm pertechnetate concentrations were less when 100 mCi 99Tcm eluent was used than with 300 mCi amounts. The level of impurity was also lower in vials kept under condition (1) than in vials kept under condition (2). Unexpected concentrations of free 99Tcm pertechnetate (maximum about 30%) were found in some commercial preparations. Only in one MDP and one HDP preparation did the average free 99Tcm pertechnetate concentration stay within tolerable limits under all experimental parameters. This study demonstrates that careful quality control is needed and that only freshly prepared bone-seeking radiopharmaceuticals should be applied, especially when 99Tcm eluents of about 300 mCi are used for kit preparation.