¹³¹Ba as a promising SPECT-diagnostic match for ^223/224Radium

We recognize ¹³¹Ba as a SPECT radionuclide, which provides a diagnostic match for the therapeutic alpha-emitting radionuclides ²²³Ra and ²²⁴Ra. The gamma-emitter barium-131 (t_½ = 11.5 d) decays with an energy of 123.8 keV (30% intensity) of the first decay via cesium-131 (t_½ = 9.7 d) to stable xenon-131, each by electron capture. Our aim was to develop of a straightforward resin-based radiochemical separation to yield ¹³¹Ba with high radionuclide purity. Furthermore, the radiolabeling of the complexing agent macropa with [¹³¹Ba]Ba²⁺ using mild labeling conditions was intended. For this purpose, different TLC systems as reaction control were utilized. The radiopharma-cological characterization of ¹³¹Ba-labeled macropa in comparison to uncomplexed [¹³¹Ba]Ba²⁺ was carried out in healthy mice, including biodistribution and small animal SPECT/CT experiments.