Production of Ga-68 with a General Electric PETtrace cyclotron by liquid target

Abstract

Purpose: In recent years the use of ⁶⁸Ga (t_1/2 = 67.84 min, β⁺: 88.88%) for the labelling of different PET radiopharmaceuticals has significantly increased. This work aims to evaluate the feasibility of the production of ⁶⁸Ga via the ⁶⁸Zn(p,n)⁶⁸Ga reaction by proton irradiation of an enriched zinc solution, using a biomedical cyclotron, in order to satisfy its increasing demand.

Methods: Irradiations of 1.7 Msolution of ⁶⁸Zn(NO₃)₂ in 0.2 N HNO₃ were conducted with a GE PETtrace cyclotron using a slightly modified version of the liquid target used for the production of fluorine-18. The proton beam energy was degraded to 12 MeV, in order to minimize the production of ⁶⁷Ga through the⁶⁸Zn(p,2n)⁶⁷Ga reaction. The product's activity was measured using a calibrated activity meter and a High Purity Germanium gamma-ray detector.

Results: The saturation yield of⁶⁸Ga amounts to (330 ± 20) MBq/µA, corresponding to a produced activity of⁶⁸Ga at the EOB of (4.3 ± 0.3) GBq in a typical production run at 46 µA for 32 min. The radionuclidic purity of the⁶⁸Ga in the final product, after the separation, is within the limits of the European Pharmacopoeia (>99.9%) up to 3 h after the EOB. Radiochemical separation up to a yield not lower than 75% was obtained using an automated purification module. The enriched material recovery efficiency resulted higher than 80-90%.

Conclusions: In summary, this approach provides clinically relevant amounts of⁶⁸Ga by cyclotron irradiation of a liquid target, as a competitive alternative to the current production through the⁶⁸Ge/⁶⁸Ga generators.

Keywords: Gallium-68; Liquid target; Medical cyclotron; Radionuclide production.