A study of radiogallium aqueous chemistry: in vitro and in vivo characterisation of (67) Ga-hydrolysed-stannous fluoride particles.

Abstract

The objective of this study was to explore the aqueous chemistry of gallium using (67) Ga-chloride starting material, by radiolabelling hydrolysed(h)-stannous fluoride particles and then characterising the optimal formulation for radiochemical purity (RCP) and radioactive particle size distribution in vitro. The pilot reactions determined stannous fluoride was added to (67) Ga-acetate under nitrogen and then heated at 100 °C for 20 min to achieve ≥95% RCP and (67) Ga-particles were >3 µm in diameter. A high radioactive concentration of (67) Ga-h-SnF2 particles could be prepared similarly in ≥97% RCP with 74% as 3-5 µm and 26% >5 µm in diameter. The latter formulation had larger particles than (99m) Tc-h-SnF2 colloid (96% of 1-3 µm), and it resulted in a rat biodistribution of 41% in the lungs, 41% in the liver plus spleen and 18% in the carcass at 20 min after injection. The carcass activity was attributed to bone marrow and some (67) Ga-transferrin formed in blood. Isolated mixed human leucocytes were radiolabelled with (67) Ga-h-SnF2 particles in 100% efficiency, and the (67) Ga-cells did not release soluble (67) Ga(3+) at room temperature over 3 h. The (67) Ga-h-SnF2 particle formulation could find a use in labelling leucocyte cells for in vivo homing studies when delayed animal imaging is required.