Proton irradiation parameters and chemical separation procedure for the bulk production of high-specific-activity ^186gRe using WO₃ targets

Abstract

Rhenium-186g (T_1/2= 89.2 h) is a β⁻ emitter suitable for therapeutic applications. Current production methods rely on reactor production via¹⁸⁵Re(n,γ) which results in low specific activities, thereby limiting its use. Production by p,d activation of enriched ¹⁸⁶W results in a ^186gRe product with a higher specific activity, allowing it to be used for targeted therapy with limited receptors. A test target consisting of pressed, sintered ^natWO₃ was proton irradiated at Los Alamos (LANL-IPF) to evaluate product yield and impurities, irradiation parameters and wet chemical Re recovery for proof-of-concept for bulk production of ^186gRe. We demonstrated isolation of ^186gRe in 97% yield from irradiated ^natWO₃ targets within 12 h of end of bombardment (EOB) via an alkaline dissolution followed by anion exchange. The recovery process has potential for automation, and WO₃ can be easily recycled for recurrent irradiations. A ^186gRe batch yield of 42.7 ± 2.2 μCi/μAh or 439 ± 23 MBq/C was obtained after 24 h in an 18.5 μA proton beam. The target entrance energy was determined to be 15.6 MeV. The specific activity of ^186gRe at EOB was measured to be 1.9 kCi (70.3 TBq) mmol⁻¹, which agrees well with the result of a previous ^185,186mRe co-production EMPIRE and TALYS modeling study assuming similar conditions. Utilizing enriched ¹⁸⁶WO₃, we anticipate that a proton beam of 250 μA for 24 h will provide batch yields of 256 mCi (9.5 GBq) of ^186gRe at EOB with specific activities even higher than 1.9 kCi (70.3 TBq) mmol⁻¹, suitable for therapy applications.