Development of a Ge/Ga Generator System Using Polysaccharide Polymers and Its Application in PET Imaging of Tropical Infectious Diseases.

Gallium-68 (Ga) is a positron emitter for clinical positron emission tomography (PET) applications that can be produced by a Ge/Ga generator without cyclotron. However, commercially available Ge/Ga generator systems require multiple steps for the preparation of Ga radiopharmaceuticals and are sometimes plagued by metallic impurities in the Ga eluent. We developed a Ge/Ga generator system using polysaccharide-based adsorbents and direct application of the generator-eluted Ga-citrate to PET imaging of tropical infectious diseases. -Methylglucamine (MG) as a Ge-adsorbing unit (Sepha-MGs) was introduced to a series of Sephadex G-10, G-15, G-25, G-50, and G-75. In the batch method, over 97% of the Ge in the solution was adsorbed onto the Sepha-MG series within 15 min. In particular, Ge was effectively adsorbed on the Sepha(15)-MG packed columns and 70-80% of the Ga was eluted by 1 mL of 0.1 M trisodium citrate with low Ge contamination (<0.001%). The chemical form of the generator-eluted Ga solution was identified as Ga-citrate. In PET studies, affected regions in mice infected with and severe fever with thrombocytopenia syndrome virus were clearly visualized using the Ga-citrate. Sepha-MGs are useful adsorbents for Ge/Ga generator systems with high Ga elution efficiency and minimal Ge breakthrough. These results indicated that eluted Ga-citrate can be directly used for PET imaging of infectious sites in mice. This novel generator system may be useful for straightforward PET imaging of infection in clinical practice.