Computational evaluation of 161Tb production pathways for theranostic applications using 159Tb and gadolinium targets

Terbium-161 is a promising theranostic radionuclide that, through the emission of medium-energy β - particles, Auger electrons, and low-energy photons, enables both effective therapy and simultaneous imaging. In this study, three neutron-based production routes—direct irradiation of 159 Tb, indirect irradiation using natural gadolinium, and indirect irradiation using enriched 160 Gd—were quantitatively investigated using Bateman chain calculations in MATLAB for a 1 g sample under a thermal neutron flux of 1.98 × 10 14 n·cm -2 ·s -1 , with 7 days of irradiation followed by 2 days of cooling. The results demonstrated that direct irradiation of 159 Tb is limited by low yield and dominant production of 160 Tb, indirect irradiation of natural gadolinium allows stable 161 Tb production but delays in post-irradiation separation reduce specific activity, and irradiation of enriched 160 Gd provides a controlled pathway ensuring high yield, minimal long-lived impurities, and excellent specific activity of 161 Tb. This study indicates that neutron irradiation of enriched 160 Gd represents the most favorable of the investigated routes in terms of calculated 161 Tb production performance, providing high radionuclidic purity, favorable yield, and high specific activity.