Efficient 169Yb high-dose-rate brachytherapy source production using reactivation

Abstract

Purpose: To present and quantify the effectiveness of a method for the efficient production of 169Yb high-dose-rate brachytherapy sources with 27 Ci activity upon clinical delivery, which have about the same dose rate in water at 1 cm from the source center as 10 Ci 192Ir sources. Materials: A theoretical framework for 169Yb source activation and reactivation using thermal neutrons in a research reactor and 168Yb-Yb2O3 precursor is derived and benchmarked against published data. The model is dependent primarily on precursor 168Yb enrichment percentage, active source volume of the active element, and average thermal neutron flux within the active source. Results: Efficiency gains in 169Yb source production are achievable through reactivation, and the gains increase with active source volume. For an average thermal neutron flux within the active source of 1 × 1014 n cm−2 s−1, increasing the active source volume from 1 to 3 mm3 decreased reactor-days needed to generate one clinic-year of 169Yb from 256 days yr−1 to 59 days yr−1, and 82%-enriched precursor dropped from 80 mg yr−1 to 21 mg yr−1. A resource reduction of 74%–77% is predicted for an active source volume increase from 1 to 3 mm3. Conclusions: Dramatic cost savings are achievable in 169Yb source production costs through reactivation if active sources larger than 1 mm3 are used.