Activity measurements and calibrations for 225Ac in radioactive equilibrium with its progeny

Denis E Bergeron; Gulakhshan Hamad; Brittany A Broder; Jeffrey T Cessna; Adam J Pearce; Jerome LaRosa; Leticia Pibida; Rhys Salter; Neha S Saxena; Brian E Zimmerman

doi:10.1016/j.apradiso.2024.111630

Activity measurements and calibrations for ²²⁵Ac in radioactive equilibrium with its progeny

Appl Radiat Isot. 2024 Dec 9:217:111630. doi: 10.1016/j.apradiso.2024.111630. Online ahead of print.

Authors

Affiliations

¹ Radiation Physics Division, National Institute of Standards and Technology, 100 Bureau Dr., Gaithersburg, MD, 20899-8462, USA. Electronic address: [email protected].
² Radiation Physics Division, National Institute of Standards and Technology, 100 Bureau Dr., Gaithersburg, MD, 20899-8462, USA; Janssen Pharmaceuticals, 335 Phoenixville Pike, Malvern, PA, 19355, USA.
³ Radiation Physics Division, National Institute of Standards and Technology, 100 Bureau Dr., Gaithersburg, MD, 20899-8462, USA.
⁴ Janssen Pharmaceuticals, 1400 Mckean Road, Spring House, PA, 19477, USA.
⁵ Janssen Pharmaceuticals, 335 Phoenixville Pike, Malvern, PA, 19355, USA.

PMID: 39681031
DOI: 10.1016/j.apradiso.2024.111630

Abstract

The massic activity of ²²⁵Ac in 0.1 mol/L HCl was measured by multiple primary methods over four consistent measurement campaigns. Results from the triple-to-double coincidence ratio (TDCR) method of liquid scintillation (LS) counting were in accord with other LS-based primary methods. The calibration of commercial radionuclide calibrators ("dose calibrators") is described, with discussion of current literature values. Comparisons between experimental ionization chamber and NaI(Tl) well counter responses and benchmarked Monte Carlo models are addressed.

Keywords: Actinium-225; Activity standard; Breakthrough; Gamma-ray spectrometry; Liquid scintillation counting; Long-lived impurities; Radionuclide calibrator; Radiopharmaceutical therapy; TDCR; Targeted alpha therapy.

Published by Elsevier Ltd.