Technetium-99m DTPA does not break down during ultrasound nebulization

For several years aerosolized 99Tcm-DTPA has been used for studies of pulmonary permeability. Comparable results have been obtained regardless of the 99Tcm-DTPA having been nebulized in an ultrasound nebulizer or a jet nebulizer. It was therefore surprising when in a recent study it was observed that more than 90% of a commercially available 99Tcm-DTPA (Squibb) was dissociated into 99TcmO4- and DTPA during ultrasound nebulization. To verify this observation we performed chromatography of seven commercially available DTPA-labelling kits (including that of Squibb). Four different test preparations of each of the kits were analysed: (1) stock solution of 99Tcm-DTPA; (2) heated (80 degrees C) 99Tcm-DTPA; (3) 99Tcm-DTPA nebulized by a DeVilbiss ultrasound nebulizer; (4) 99Tcm-DTPA nebulized by a Varic ultrasound nebulizer. In no case were we able to demonstrate more than 1.0% reduced pertechnetate (99TcmO2) or more than 0.9% free 99TcmO4- after either heating or ultrasound nebulization. A maximum of 5.6% 99TcmO2 could be demonstrated in the stock solution if chromatography was done immediately after the preparation, but only 15 min later no more than 0.9% 99TcmO2 was present. We conclude that there is no essential chemical breakdown of 99Tcm-DTPA during ultrasound nebulization. Caution should be taken not to use the 99Tcm-DTPA until 15 min after its preparation.