Efficient Yb-169 High-Dose-Rate Brachytherapy Source Production Using Reactivation

Purpose To present and quantify the effectiveness of a method for the efficient production of Yb-169 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 Ir-192 sources. Materials A theoretical framework for Yb-169 source activation and reactivation using thermal neutrons in a research reactor and Yb-168-Yb2O3 precursor is derived and benchmarked against published data. The model is dependent primarily on precursor Yb-168 enrichment percentage, active source volume of the active element, and average thermal neutron flux within the active source. Results Efficiency gains in Yb-169 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 x 10(14) n cm(-2) s(-1), increasing the active source volume from 1 to 3 mm(3) decreased reactor-days needed to generate one clinic-year of Yb-169 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 mm(3). Conclusions Dramatic cost savings are achievable in Yb-169 source production costs through reactivation if active sources larger than 1 mm(3) are used.