RESUMO
OBJECTIVE: The purpose of this study was to determine the adsorption behavior of some widely used, commercially available 99mTc radiopharmaceuticals onto different types of plastic syringes. METHODS: Kits were reconstituted with 99mTc-pertechnetate diluted with 0.9% saline to produce maximum radioactive concentrations, as stated by the manufacturers. Aliquots of the solutions were transferred to four different brands of 2-ml syringes. The activity in the syringes was measured before and after injections or simulated injections. The amount adsorbed to the plastic syringe barrel and plunger before and after washout also was measured at different time intervals. Comparisons between products from different manufacturers were made for 99mTc succimer (DMSA) and 99mTc macroaggregated albumin (MAA). RESULTS: Some 99mTC preparations undergo significant adsorption to plastic syringes. Adsorption differs considerably between products from different manufacturers. There was significantly higher residual activity in some types of syringes. In some cases the residual was as high as 40%-50% of the initial activity, and most of the adsorption occurred within 15 min of filling the syringe. CONCLUSION: The data suggest that the extent of adsorption depends on pharmaceutical excipients in the kits and/or the type of syringe used. When inappropriate syringes are used, the reduction in the administered activity may result in poor-quality images. Therefore, the compatibility between radiopharmaceutical and syringe should be investigated under normal conditions of preparation and use every time a new brand of syringe or a new radiopharmaceutical comes into use in diagnostic nuclear medicine.