An improved tungsten-178/tantalum-178 generator system for high volume clinical applications

Clinical utilization of the multiwire gamma camera (MWGC) requires low-energy radionuclides. The short-lived (9.3 min) tantalum-178 (¹⁷⁸Ta) is ideally suited for the MWGC and can be produced from long-lived (21.7 day) tungsten-178 (¹⁷⁸W) by a previously reported ¹⁷⁸W/¹⁷⁸Ta generator. This generator, however, is limited by sharp increase in breakthrough after elution of only 30-60 column-volumes. To optimize the ¹⁷⁸W/¹⁷⁸Ta generator for clinical use, varying eluant acid concentrations were evaluated. A reduced (from 0.1 to 0.03N) HCl concentration in the eluant, coupled with low operating temperatures (3 to 5°C) allowed high (40 to 60%) ¹⁷⁸Ta yield. Minimal ¹⁷⁸W breakthrough (<.01%) resulted, even after elution of more than 200 column-volumes. Each of six tested generators provided sterile, high activity (up to 100 mCi) ¹⁷⁸Ta elutions for more than 30 days. Radiation dosimetry was estimated utilizing both human and animal biodistribution data. The whole body (critical organ) dose in adults and neonates were 1/20 (1/21) and 1/19 (1/50) respectively relative to that of technetium-99m (^99mTc) as sodium pertechnetate. The optimized ¹⁷⁸W/¹⁷⁸Ta generator provides a commercially practical, safe source of low-energy radioisotope for the MWGC with substantial dosimetry advantages over ^99mTc.