ATSM) was prepared using in house-made diacetyl-bis (N4--methylthiosemicarbazone)(ATSM) ligand and [61Cu] CuCl2 produced via the natZn (p, x) 61Cu (180 mA proton irradiation, 22 MeV, 3.2 h) and purified by a ion chromatography method.[61Cu] ATSM radiochemical purity was> 98%, as shown by HPLC and RTLC methods.[61Cu] ATSM was administered into normal and tumor bearing rodents for up to 210 minutes, followed by biodistribution and co-incidence imaging studies. Significant tumor/non-tumor accumulation was observed either by animal sacrification or imaging.[61Cu] ATSM is a positron emission tomography (PET) radiotracer for tumor hypoxia imaging.