Effects of alternative reconstitution procedures on the labelling efficiency and in vitro stability of 99Tcm-labelled radiopharmaceuticals.

Adding normal saline (NS) separately before 99 Tc m -sodium pertechnetate to MDP cold kits has been shown to reduce substantially the radiation dose to the hand. A similar dose reduction will probably prove to be valid with the preparation of most other 99 Tc m -labelled radiopharmaceuticals. However, it is unknown how this altered reconstitution procedure may affect the labelling efficiency and in vitro stability of the 99 Tc m -labelled radiopharmaceuticals. We have evaluated the effects on the labelling efficiency and in vitro stability of 99 Tc m -labelled MDP, mertiatide and sestamibi reconstituted with three different methods: adding normal saline before 99 Tc m activity (NS/Tc); adding 99 Tc m activity before normal saline (Tc/NS); and the standard reconstitution method of adding both 99 Tc m activity and normal saline together. The labelling efficiency and in vitro stability were evaluated by measuring the radiochemical purity of each radiopharmaceutical tested at 0, 1, 3, 6, 12 (except Tc m -MDP) and 24 h after reconstitution. For 99 Tc m -mertiatide, there was a very slight difference in the labelling efficiency, mostly due to the Tc/NS method being ∼ 0.29% lower across time post-reconstitution than the standard method. For 99 Tc m -labelled MDP and sestamibi, there were no differences between the three methods in terms of labelling efficiency and in vitro stability. In conclusion, both alternative methods (i.e. NS/Tc and Tc/NS) appear not to have any detrimental effect on the labelling efficiency and in vitro stability of the 99 Tc m -labelled radiopharmaceuticals that we tested. However, of the two alternative kit reconstitution methods, we recommend the NS/Tc method, since it may reduce the hand radiation dose.