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 via 185Re(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.

Nuclear data for medical radionuclides

“…Based on nuclear model calculations the specific activity of 186 Re was also predicted [60]. More recent experimental work in this direction [61,62] appears to support the theoretical considerations. Presently, some practical yield measurements [cf.…”

Uses of alpha particles, especially in nuclear reaction studies and medical radionuclide production

“…[212][213][214][215][216][217]), and the -production route has so far not been investigated. As regards the (n, ) process, many of the reactor radionuclides are produced via this route.…”

Production and separation of 186gRe from proton bombardment of 186WC

“…One of the methods being pursued to make non-carrier added 186g Re is the charged particle reaction 186 W(p,n) 186g Re [14][15][16][17][18]. For this reaction both 186 W metal and 186 WO 3 have been used as target materials, with the utilization of various processing methods to purify the radioactivity.…”

“…When 186 W metal was used as the target material, post-bombardment processing have been accomplished via wet chemical technique [17] and by the dry processing method, thermo-chromatography [18]. The use of elemental 186 W for the large scale production of 186 Re has as a main disadvantage: the high reductive pathway to convert WO 3 , the processing byproduct, back to elemental W. Use of WO 3 as the target in the charged particle reaction, has also been reported, with the application of wet chemical processes being applied for post-bombardment processing [14][15][16]. In a wet chemical process using organic anion exchangers, Fassbender et al [16] reported an activity yield of 42.7 μCi/μAh after 24 h of bombardment of 25 g of natural WO 3 at 18.5 μA, with a proton entrance energy of 15.6 MeV.…”

“…The use of elemental 186 W for the large scale production of 186 Re has as a main disadvantage: the high reductive pathway to convert WO 3 , the processing byproduct, back to elemental W. Use of WO 3 as the target in the charged particle reaction, has also been reported, with the application of wet chemical processes being applied for post-bombardment processing [14][15][16]. In a wet chemical process using organic anion exchangers, Fassbender et al [16] reported an activity yield of 42.7 μCi/μAh after 24 h of bombardment of 25 g of natural WO 3 at 18.5 μA, with a proton entrance energy of 15.6 MeV. Using a methyl ethyl ketone extraction to process their target, Moustapha et al [14] reported a yield of 1.085 mCi after bombarding 200 mg of 186 WO 3 for 12 h at 20-25 μA using 13.8 MeV protons.…”