A new germanium-63/gallium-68 generator

Abstract

A germanium-gallium generator producing EDTA-free Ga-68 would permit the synthesis of a broad range of Ga-68 radiopharmaceuticals and thus facilitate the widespread application of positron tomography. We have investigated a solvent-extraction generator system producing the weak complex of Ga-68 with 8-hydroxyquinoline (Ga-68 oxine), free of EDTA. The conditions for optimum Ga-68 yield and minimum Ge-68 breakthrough involve extraction with chloroform from pH 5 buffer containing Ge4+ carrier, followed by evaporation to dryness. This produces Ga-68 yields of 70--80%, with Ge-68 breakthrough of less than 0.003%. The Ga-68 oxine is readily converted to other radiopharmaceuticals such as Ga-68 EDTA, Ga-68 EDTMP, or Ga-68 colloid, and is conveniently delivered dry. The extraction system is simple and amenable to automation, and the low loss rate and 280-day half-life of Ge-68 provide a generator with a long useful lifetime.