Tc 99m Generator Development: Up-to-Date Tc99m Recovery Technologies for Increasing the Effectiveness of 99 Mo Utilisation

A review on the super(99) Mo sources available today and on the Tc99m generators developed up to date for increasing the effectiveness of super(99) Mo utilisation is performed in the format of detailed description of the features and technical performance of the technological groups of the super(99) Mo production and Tc99m recovery. The latest results of the endeavour in this field are also surveyed in regard of the technical solution for overcoming the shortage of super(99) Mo supply. The technological topics are grouped and discussed in a way to reflect the similarity in the technological process of each group. The following groups are included in this review which are high specific activity super(99) Mo: the current issues of production, the efforts of more effective utilisation, and the high specific activity super(99) Mo-based Tc99m generator and Tc99m concentration units; low specific activity super(99) Mo: the super(99) Mo production based on neutron capture and accelerators and the direct production of Tc99m and the methods of increasing the specific activity of super(99) Mo using Szilard-Chalmers reaction and high electric power isotopic separator; up-to-date technologies of Tc99m recovery from low specific activity super(99) Mo: the solvent extraction-based Tc99m generator, the sublimation methods for super(99) Mo/Tc99m separation, the electrochemical method for Tc99m recovery, and the column chromatographic methods for Tc99m recovery. Besides the traditional Tc99m-generator systems, the integrated Tc99m generator systems ( super(99m) Tc generator column combined with postelution purification/concentration unit) are discussed with the format of process diagram and picture of real generator systems. These systems are the technetium selective sorbent column-based generators, the high Mo-loading capacity column-based integrated Tc99m generator systems which include the saline-eluted generator systems, and the nonsaline aqueous and organic solvent eluent-eluted generator systems using high Mo-loading capacity molybdategel and recently developed sorbent columns. Tc99m concentration methods used in the Tc99m recovery from low specific activity super(99) Mo are also discussed with detailed process diagrams which are surveyed in two groups for Tc99m concentration from the saline and nonsaline Tc99m-eluates. The evaluation methods for the performance of Tc99m-recovery/concentration process and for the Tc99m-elution capability versus Mo-loading capacity of