treatment but require any derived radiopharmaceutical to be essentially free of impurities. Terbium-155
prepared by proton irradiation and on-line mass separation at the CERN-ISOLDE and CERN-MEDICIS
facilities contains radioactive 139Ce16O and also zinc or gold, depending on the catcher foil used. A
method using ion-exchange and extraction chromatography resins in two column separation steps
has been developed to isolate 155Tb with a chemical yield of e95% and radionuclidic purity e99.9%.
Conversion of terbium into a form suitable for chelation to targeting molecules in diagnostic nuclear
medicine is presented. The resulting 155Tb preparations are suitable for the determination of absolute
activity, SPECT phantom imaging studies and pre-clinical trials.