Radiochemical Quality Control Methods for Radium-223 and Thorium-227 Radiotherapies

The majority of radiopharmaceuticals for use in disease detection and targeted treatment undergo a single radioactive transition (decay) to reach a stable ground state. Complex emitters, which produce a series of daughter radionuclides, are emerging as novel radiopharmaceuticals. The need for validation of chemical and radiopurity with such agents using common quality control instrumentation is an area of active investigation. Here, we demonstrate novel methods to characterize ²²⁷Th and ²²³Ra. A radio-TLC scanner and a γ-counter, two common and widely accessible technologies, as well as a solid-state α-particle spectral imaging camera were evaluated for their ability to characterize and distinguish ²²⁷Th and ²²³Ra. We verified these results through purity evaluation of a novel ²²⁷Th-labeled protein construct. The γ-counter and α-camera distinguished ²²⁷Th from ²²³Ra, enabling rapid and quantitative determination of radionuclidic purity. The radio-TLC showed limited ability to describe purity, although use under α-particle-specific settings enhanced resolution. All three methods were able to distinguish a pure from impure ²²⁷Th-labeled protein. The presented quality control evaluation for ²²⁷Th and ²²³Ra on three different instruments can be applied to both research and clinical settings as new alpha particle therapies are developed.