Very high specific activity 66/68Ga from zinc targets for PET

This work describes the production of very high specific activity 66/68Ga from natZn(p,n) and 66Zn(p,n) using proton irradiations between 7 and 16 MeV, with emphasis on 66Ga for use with common bifunctional chelates. Principal radiometallic impurities are 65Zn from (p,x) and 67Ga from (p,n). Separation of radiogallium from target material is accomplished with cation exchange chromatography in hydrochloric acid solution. Efficient recycling of Zn target material is possible using electrodeposition of Zn from its chloride form, but these measures are not necessary to achieve high specific activity or near-quantitative radiolabeling yields from natural targets. Inductively coupled plasma mass spectroscopy (ICP-MS) measures less than 2 ppb non-radioactive gallium in the final product, and the reactivity of 66Ga with common bifunctional chelates, decay corrected to the end of irradiation, is 740 GBq/μmol (20 Ci/μmol) using natural zinc as a target material. Recycling enriched 66Zn targets increased the reactivity of 66Ga with common bifunctional chelates.

► Cyclotron-produced 66/68Ga with AG50W separation has high S.A. (<2 ppb cold Ga).
► Product 66/68Ga has a reactivity for NOTA of >700 GBq/μmol (20 Ci/μmol).
► natZn and 66Zn targets are economical and produce similar radiochemical purities.