A radioconjugate containing a synthetic bombesin receptor antagonist targeting the gastrin-releasing peptide receptor (GRPR), that is linked by the macrocyclic chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) to the radionuclide gallium (Ga) 68, with potential use in diagnostic imaging using positron emission tomography/computed tomography (PET/CT). Upon administration of gallium Ga 68 GRPR antagonist BAY86-7548, the peptide moiety targets and binds to GRPR. Upon PET/CT, GRPR-expressing tumor cells can then be visualized. GRPR, also called bombesin receptor 2 (BB2), is a G protein-coupled seven-transmembrane receptor belonging to the bombesin receptor family. It is overexpressed in certain types of cancers.