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 169 Yb 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 192 Ir sources. Materials: A theoretical framework for 169 Yb source activation and reactivation using thermal neutrons in a research reactor and 168 Yb-Yb 2 O 3 precursor is derived and benchmarked against published data. The model is dependent primarily on precursor 168 Yb enrichment percentage, active source volume of the active element, and average thermal neutron flux within the active source. Results: Efficiency gains in 169 Yb 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 9 10 14 n cm À2 s À1 , increasing the active source volume from 1 to 3 mm 3 decreased reactor-days needed to generate one clinic-year of 169 Yb from 256 days yr À1 to 59 days yr À1 , and 82%-enriched precursor dropped from 80 mg yr À1 to 21 mg yr À1 . 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 169 Yb source production costs through reactivation if active sources larger than 1 mm 3 are used.

A novel 169Yb‐based dynamic‐shield intensity modulated brachytherapy delivery system for prostate cancer

“…The source can be adapted to handle more activity to lower treatment times, if needed, by increasing the length of the active core. For a highly enriched precursor, the 175 Yb impurities levels are sufficiently low after activation and additional cooling is not required . To modulate the intensity profile of the source, thin platinum shields are inserted within the catheters, using a similar approach as Adams et al Platinum was selected due to its high density (21.45 g cm −3 ), high atomic number (Z = 78), and ferromagnetic properties.…”

“…For a highly enriched precursor, the 175 Yb impurities levels are sufficiently low after activation and additional cooling is not required. 35,37 To modulate the intensity profile of the source, thin platinum shields are inserted within the catheters, using a similar approach as Adams et al 18 Platinum was selected due to its high density (21.45 g cm À3 ), high atomic number (Z = 78), and ferromagnetic properties. The shield partially fills the hollow portion of a six French (2 mm) plastic catheter with a wall thickness of 0.25 mm [Figs.…”

“…169 Yb has been investigated as a source for brachytherapy applications . 169 Yb has a half‐life of 32.0 days and primarily emits photons with energies in the 50–308 keV range with an average energy of 93 keV.…”

“…The lower energy also reduces the shielding requirements for treatment rooms. The availability of Yb 2 O 3 powder highly enriched in 168 Yb (82–88%) enables manufacturing of 169 Yb sources with high activities (~30 Ci), fitted inside capsules appropriate for HDR BT …”

“…The availability of Yb 2 O 3 powder highly enriched in 168 Yb (82-88%) enables manufacturing of 169 Yb sources with high activities (~30 Ci), fitted inside capsules appropriate for HDR BT. 35 The purpose of this work is to present the concept and design of the anisotropic intensity modulated brachytherapy (AIM-Brachy) device, a novel delivery system that can enable 169 Yb-based dynamic-shield IMBT for prostate cancer, and to evaluate the potential urethra-sparing advantages of IMBT delivered with AIM-Brachy relative to HDR BT. The AIM-Brachy system was designed to be compatible with commercial afterloaders by incorporating an 169 Yb HDR source and a compact rotating mechanism that can be directly connected to the afterloader through the transfer tubes.…”