A method for labeling a prostate-specific membrane antigen (PSMA) ligand with a radioactive isotope, such as 68Ga, 177Lu, or 90Y, includes providing a reaction vial containing a sodium-based buffering agent and the PSMA ligand, both in dried form； adding a solution of the radioactive isotope in HCl to the reaction vial, thus obtaining a solution of the PSMA ligand and the radioactive isotope in the HCl； and mixing the solution and then incubating it for a sufficient period of time, thus reacting the PSMA ligand with the radioactive isotope to thereby obtain the PSMA ligand labeled with the radioactive isotope, At least 90% of the radioactive isotope in the solution is bound to the PSMA ligand. A kit can be used for carrying out the method. Radiolabeled PSMA ligands prepared by this method can be used for both imaging and therapy.
