Abstract
The phenomena of adsorption of several 99mTc-radiopharmaceuticals on disposable syringes is common knowledge and can reach a level of up to 50%, with the result of inadequate dosage. The resulting underdosage 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 99mTc-radiopharmaceuticals on various brands of syringes. Methods: The 99mTc-radiopharmaceuticals were prepared according to manufacturer instruction. For the assessment, the disposable syringes (n = 3) were filled to one-third of the capacity with the 99mTc preparation and incubated for 30 min at room temperature. The syringes were withdrawn into evacuated vials. The radioactivity of the syringes was measured before and after withdrawal. Furthermore, the dilution effect of 99mTc-preparations was studied. We used two different brands of syringes and examined systematically 99mTc-pertechnetate, 99mTc-DPD, 99mTc-HDP, 99mTc-MDP, 99mTc-tetrofosmin, 99mTc-sestamibi, 99mTc-DMSA(V) and 99mTc-succimer. Additional, 99mTc-succimer was retested with five brands of syringes. Results: 99mTc-pertechnetate, 99mTc-phosphonates, and 99mTc-DMSA(V) showed no significant adsorption. The measured radioactive retention of 2-5% was equivalent to the determined death volume. Using 99mTc-tetrofosmin, we found a slight but significant adsorption of 4-7%. The 99mTc-sestamibi preparation showed a non-significant retention of 3-5%. However, when diluting the 99mTc-sestamibi 1:10 with saline, the adsorption rate increased to a value of 9-13%. 99mTc-succimer displayed different adsorption levels depending on the brand of the syringe and the preparation technique. The adsorption of 99mTc-succimer, prepared from kits according to the instructions, did not exceed 15%. The saline dilution 1:10 of a 99mTc-succimer kit preparation, as well as an in-house preparation, demonstrated a manifested radioactive syringe adsorption rate of more than 30%. Conclusion: The results revealed the significance of syringe adsorption of radiopharmaceuticals in the prevention of an under-dosing. Therefore, an assessment is recommended as a quality assurance before the introduction of new brands of plastic syringes or routine application of diluted or in-house radiopharmaceuticals.