Optimization of the production of [⁶¹Cu]Diacetyl-bis(N⁴-methylthiosemicarbazone) for PET studies

Summary

Copper-61 produced via the ^natZn(p,x)⁶¹Cu nuclear reaction was used for the preparation of [⁶¹Cu]diacetyl-bis(N⁴-methylthiosemicarbazone) ([⁶¹Cu]ATSM) (4) using a house-made ATSM ligand. After a proton irradiation of an electroplated zinc layer by 22 MeV protons at 180 mA for 3.2 hours, ⁶¹Cu was recovered by two-step chromatography using a cation and an anion exchange column. About 222 GBq (6.00 Ci) of ⁶¹Cu²⁺ was obtained with a radiochemical separation yield of more than 95% and a radionuclidic purity of better than 99%. Colorimetric methods showed that traces of chemical impurities in the product were below the accepted limits. The [⁶¹Cu]ATSM production was optimized for reaction conditions (buffer concentration and temperature) with a radiochemical yield of higher than 80%, radiochemical purity of better than 98% and a specific activity of about 246 Ci/mmol. The produced [⁶¹Cu]ATSM is a PET radiotracer for hypoxia imaging with an intermediate half life and a satisfactory quality, suitable for future PET studies.