QC of 99Mo/99mTc generator between 2003 and 2005 in two nuclear medicine laboratories in Brazil

Technetium-99m is the most used radionuclide in nuclear medicine diagnostic procedures due to, among other characteristics, the uncomplicated and flexible way of obtaining it from 99Mo/99mTc generators. Despite the appropriate characteristics of the product and attainment process, occasionally the eluate can be contaminated with undesirable proportions of 99Mo or Al3+, and control of this was the object of study by several authors. In this work are presented the results of a quality control programme of a 99Mo/99mTc generator in two Brazilian nuclear medicine laboratories during the years 2003 and 2005. A total of 488 99Mo/99mTc generators were evaluated, with calibrated activities of 37 GBq (37 units), 55.5 GBq (355 units) and 74 GBq (74 units). All of them were produced by the same manufacturer (IPEN-CNEN/SP, Brazil). The radioisotopic purity was performed using 6 mm of lead shield, the chemical purity was done with an aluminum spot test kit produced at CMN-FMUSP, the radiochemical purity was accomplished by chromatographic analysis using a W1 paper/methanol 85% system, and the pH, using a pH indicator paper. Systematic analyses were performed just in the first elution, except for the radioisotopic purity that was evaluated in the first and in the subsequent elutions, and the chemical purity that was also evaluated in the second elution. The thresholds established in United States Pharmacopoeia (USP-XXIII) were used as standard values. The number of tests performed in each group of generators is shown. All elutions assessed showed an average pH = 5 and radiochemical purity over 95%, which are in agreement with USP-XXIII limits. However, eluates from some generators presented radionuclide and chemical purities that are below the values established in USP-XXIII, as shown. Although Morengo did not find any value in disagreement with USP, our results proved the importance of performing quality control in generators, especially for radioisotopic and chemical purities. Moreover, generators with higher activities are more prone to show QC problems