Fig. 6. In vitro and in vivo evaluation of [²²³Ra][Ra(macropa-β-alanine)]. (a) Stability of [²²³Ra][Ra(macropa-β-alanine)] over the course of 12 days in human serum at 37 °C. (b) Organ distribution of [²²³Ra][Ra(macropa-β-alanine)] at 24 h p.i. Significant differences in osseous (*p < 0.005), splenic, and renal uptake were observed in comparison to the control [²²³Ra]RaCl₂.