13th National Congress of the Italian Association of Nuclear Medicine and Molecular Imaging (AIMN), Rimini (Italy), 2–5 March 2017

Background-aim: The scintigraphy with autologous leukocytes labelled with 99mTc-HMPAO is generally used for evaluation of inflammation and infection; 99mTc-HMPAO allows to obtain a good quality of images with a low dosimetry for the patient. Some scientific papers suggest to label a single kit of HMPAO with a higher technetium- 99m activity than the one reported in the radiopharmaceutical package insert. The purpose of this study is to validate a multidose procedure of leukocytes labelling, using a single vial of HMPAO. Methods: Our procedures are based on papers dealing with high technetium-99m activity for labelling a single HMPAO kit (120 mCi/ 4 ml) and were validated performing mediafill tests, according to the European Guidelines. We tested 6 vials of 99 mTc-HMPAO, using 12 blood samples from healthy volunteers (2 samples/vial). For each vial, we performed the radiochemical purity (%RCP) of 99 mTc- HMPAO immediately after the labelling, and evaluated at 15, 30 and 45 min after labelling. We checked the labelling efficiency (LE), cell viability with Trypan Blue test and cell efflux after 1 h from leukocytes labelling. Finally, we tested the sterility and the apirogenicity of our products. Three tests were performed to exclude the presence of bacteria and endotoxins within the preparations. Results: The results of mediafill tests showed sterility of the entire labelling procedure. The radiochemical purity of 99mTc-HMPAO resulted higher than the minimum limit reported in the radiopharmaceutical package insert (C 80%) and were constant over time. In the 91.7% of cases, the labelling efficiency was within guidelines limits (40% B LE B 80%); cell viability was within the regulatory limits (\4% of dead cells). In the 83.3% of cases the measurement of cell efflux of Tc-99m was within the accepted limits (release of Tc- 99m\10%). Finally, the sterility test showed no contamination from aerobic bacteria and mycetes; pyrogen levels were lower than the limits allowed by current Italian Pharmacopoeia (the endotoxin concentration limit is 175 EU/ml, per injected ml per kg). Conclusions: The proposed labelling protocol obtained acceptable results and complied with European Guidelines ‘‘Guidelines for the labelling of leucocytes with 99mTc-HMPAO’’ (Eur J Nucl Med Mol Imaging (2010) 37:842–848); advantages of this protocol were the optimization of the working time for the operator and the reduction of the costs, without affecting the efficiency of labelling procedure.