Stability of 99Tcm-DTPA injection: effect of delay after preparation, dilution, generator oxidant, air and oxygen

99Tcm-DTPA injection is widely used in different activity concentrations and the parent solution may require dilution to achieve the correct activity and dose volume. We have studied the stability after dilution of six makes of commercially available DTPA kits and have demonstrated that levels of free pertechnetate may reach as high as 95%. We have also demonstrated that levels are increased by subdivision of the parent solution into vials containing air or high quantities of oxygen, by reconstitution with generator eluate containing oxidant, and by delay between preparation and injection into patients. Out of six makes tested only two were stable over a wide variety of conditions.