EANM’15

Aim: 99mTc-hexamethylpropyleneamine oxime (99mTc- HMPAO) is one of the most commonly used radiopharmaceu- tical to label autologous leukocytes for evaluation of inflam- mation and infection. The European Guidelines (Eur J Nucl Med Mol Imaging (2010) 37:842-848) and some scientific papers suggest to label a single kit of HMPAO with an higher technetium-99m activity than the one reported in the radio- pharmaceutical package insert. We aimed at validating a multidose procedure using a single vial of HMPAO for leuko- cytes labelling.Materials and methods: Our procedures are based on papers dealing with high technetium-99m activity for labelling a HMPAO kit (Eur J Nucl Med (1998) 25:797-799; Nucl Med and Biol 34 (2007) 933-938) and was validated according to the European Guidelines, performing mediafill tests. For each vial we checked the radiochemical purity (%RCP) of 99mTc-HMPAO as quality control; three consec- utive RCP tests were performed for each preparation immedi- ately after the labelling and at 15, 30 and 45 minutes after labelling. We subsequently evaluated the labelling efficiency (LE) and cells viability by the Trypan blue exclusion test. In addition, we measured technetium-99m cell efflux after 1 hour; three tests were performed for each preparation and ar- ithmetic mean was calculated for every sample. Finally we checked the sterility and the apyrogenicity of our labelling product on three consecutive samples.Results: The results of mediafill tests demonstrated complete sterility of labelling pro- cedure. We tested 6 vials of 99mTc-HMPAO with twelve blood samples from healthy volunteers. The radiochemical purity of 99mTc-HMPAO always resulted higher than the min- imum limit reported in the radiopharmaceutical package insert (>80%). In the 91,7% of cases, the labelling efficiency was within guidelines limits (40% < LE < 80%). Also cell viability, assed by Trypan blue exclusion test, was within the regulatory limits (<4% of dead cells). In the 83,3% of cases the measure- ment 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: We obtained accept- able results by labelling two blood samples using a single HMPAO vial, in accord to European Guidelines “Guidelines for the labelling of leucocytes with 99mTc-HMPAO”; this experimental protocol, allows to optimize the working time of the operator and the costs, without reducing the efficiency of labelling procedure.