Systematic Assessment of the Adsorption of ^99mTc-Radiopharmaceuticals onto Plastic Syringes

Abstract

The phenomenon of adsorption of several 99m Tc-radiopharmaceuticals onto disposable syringes is common knowledge and can reach a level of up to 50%, with the result being inadequate dosing. The resulting underdosing has a substantial influence on the quality of imaging, especially in pediatric patients. Therefore, we aimed to establish a standardized in vitro assessment to investigate the adsorption of several 99m Tc-radiopharmaceuticals on various brands of syringes. Methods: The 99m Tc-radiopharmaceuticals were prepared according to manufacturer instructions. For the assessment, the disposable syringes (n 5 3) were filled to one third of capacity with the 99m Tc preparation and incubated for 30 min at room temperature. The syringes were emptied into evacuated vials, and the radioactivity of the syringes was measured before and after they were emptied. Furthermore, the dilution effect of 99m Tc preparations was studied. We used 2 different brands of syringes and systematically examined 99m Tc-pertechnetate, 99m Tc-butedronate, 99m Tc-oxidronate, 99m Tc-medronate, 99m Tc-tetrofosmin, 99m Tc-sestamibi, 99m Tc(V)dimercaptosuccinic acid, and 99m Tc-succimer. Additionally, 99m Tc-succimer was retested with 5 brands of syringes. Results: 99m Tc-pertechnetate, 99m Tc-phosphonates, and 99m Tc(V)dimercaptosuccinic acid showed no significant adsorption. The measured radioactive retention of 2%-5% was equivalent to the determined dead volume. Using 99m Tc-tetrofosmin, we found a slight but significant adsorption of 4%-7%. The 99m Tc-sestamibi preparation showed a nonsignificant retention of 3%-5%. However, when the 99m Tc-sestamibi was diluted 1:10 with saline, the adsorption rate increased to 9%-13%. 99m Tc-succimer displayed different adsorption levels depending on the brand of syringe and the preparation technique. The adsorption of 99m Tc-succimer, prepared from kits according to the instructions, did not exceed 15%. The 1:10 saline dilution of a 99m Tc-succimer kit preparation, as well as an in-house preparation, demonstrated a radioactive syringe adsorption rate of more than 30%. Conclusion: The results revealed the significance of syringe adsorption of radiopharmaceuticals in the prevention of underdosing. Therefore, a quality assurance assessment is recommended before the introduction of new brands of plastic syringes or routine application of diluted or in-house radiopharmaceuticals.

Unusual Focal Lung Uptake without CT Abnormality on a Bone Scan: What Might It Mean?

“…The conformity of the radiopharmaceutical preparation was not questionable (radiochemical purity > 97% and pH = 6, as recommended by the summary of products characteristics of the HDP cold kit). Although the patient dose was prepared 30 min before injection, neither instability nor significant interaction with the syringe were reported in the literature [16]. Furthermore, seven other patient syringes were prepared this day from the same multidose vial of 99m Tc-HDP and provided bone scans without such abnormality.…”