Activity standardization and determination of nuclear decay data of 212Pb at LNE-LNHB and first measurements in the SIR at BIPM

Lead-212/Bismuth-212 is a promising radiopharmaceutical with high therapeutic potential for Targeted Alpha Therapy. In this paper, the activity standardization of 212 Pb in equilibrium with its progeny was addressed by means of several measurement techniques at LNE-LNHB using a radioactive solution of 212 Pb-DOTAMTATE supplied by Orano Med (France). The primary standard was established by liquid scintillation counting using the Triple-to-Double Coincidence Ratio (TDCR) method and transferred to the Vinten 671 ionization chamber. The experimental calibration coefficients were compared to Monte Carlo simulations using the Penelope and Geant4 codes. An ampoule filled with a standardized solution of 212 Pb was sent to the BIPM for a submission to the International Reference System (SIR). The resulting equivalent activity was compared to the value calculated from the SIRIC software. A new measurement of the half-life of 212 Pb using a Centronic IG11 IC is presented. New γ-photon intensities based on γ-spectrometry were also measured. The present study on the metrological traceability of the radiopharmaceutical 212 Pb is an important outcome in the framework of the European project EPM AlphaMet (Metrology for Emerging Targeted Alpha Therapies).