Adsorption of 99mTc-Sestamibi onto Plastic Syringes: Evaluation of Factors Affecting the Degree of Adsorption and Their Impact on Clinical Studies

The purpose of this study was to document the extent of adhesion of Tc-99m-sestamibi to syringes in patient procedures, determine factors that influence the degree of adhesion, and evaluate alternatives to our current practice that would either result in a more reproducible degree of adhesion or, ideally, eliminate adhesion. Methods: The extent of adhesion was documented in 216 patient procedures and evaluated in detail in an additional 73 patient procedures. We evaluated the nature of the adhesion and its possible causes, including the location of adhesion in injection sets, the effect of syringe type, and the effect of prerinsing of syringes with various solutions of non-radiolabeled sestamibi and Tc-99m-sestamibi. The extent of adhesion was reevaluated in 50 procedures performed using the syringe type that demonstrated the lowest adhesion rate. Results: The degree of adhesion of Tc-99m-sestamibi to the injection set was found to be 20.1% +/- 8.0%, with a range (10th-90th percentiles) of 9%-31%. The primary cause of adhesion appeared to be the lubricant used inside the syringe barrel. Evaluation of 6 different syringe types identified a brand with a lower adhesion rate. Reevaluation in patient procedures using this brand showed a 5.2% +/- 2.5% degree of adhesion, with a range (10th-90th percentiles) of 2.5%-7.7%. Conclusion: Selection of the appropriate type of syringe can significantly reduce the magnitude and variability of residual Tc-99m-sestamibi activity. With more reproducible residual activities, we have been able to achieve an approximately 20% reduction in the dispensed dose of Tc-99m-sestamibi used in clinical procedures and a more consistent injected dose with less interpatient variation. The frequent changes in syringe design by manufacturers require that a quality control program for monitoring of residual activity be incorporated into clinical practice. This program has allowed us to maintain image quality and achieve more consistent injected patient doses in clinical procedures that use Tc-99m-sestamibi.