A carrier compound of CaCO3 microparticles radiolabeled with the α-emitting Ra-224 nuclide is a promising treatment of metastatic cancers in body cavities. To secure a safe and internationally consistent dosing to patients, radioactivity standards are developed and established by national metrology institutes.
This thesis presents the work of primary and secondary standardization of radium-224, performed at the National Institute of Standards and Technology (NIST) in the USA. The standardization of radium-224 was based on liquid scintillation (LS) counting, triple-to-double coincidence ratio (TDCR), CIEMAT-NIST efficiency tracing and the live-timed anticoincidence counting (LTAC) techniques. It is also presented herein the use of calibrated counters to study properties of multi-step decaying radium-224 labeled microparticles, and the fate of radioactive progenies, including radon-220 and lead-212. It was found that the re-adsorption of lead-212 onto the microparticles can contribute the retention of activity in the targeted area, while the diffusion of radon can extend the effective range of the alpha particles causing a “dose-smoothening effect”.