Presentation A study on remote production of 43Sc from natCaO target via the natCa(,x)-reaction

Nagatsu, Koutarou  ,  Minegishi, Katsuyuki  ,  Ming-Rong, Zhang

Objectives: Metallic radionuclides are widely used in nuclear medicine for both SPECT and PET imaging as well as for internal radiotherapy. Recently, radio-scandium is being focused as a potential radio-metal due to its favorable characteristic; particularly 43Sc has a moderate half-life of 3.9 h with enough emission rate of positron (88%), and 47Sc (–, 3.3 d) is a candidate for internal radiotherapy. These radio-scandiums can be produced from respective Ca target by using accelerated alpha particles, namely 40Ca(,x) or 44Ca(,n)-channel. In this study, we attempted to produce 43Sc remotely from natCaO target as a pilot case. Methods: A commercially available, 200 mg of natCaO (40Ca = 97 atom%) powder without further purification was loaded into a target vessel made of silicon carbide (SiC). The target vessel was covered by a 12.7 m Nb foil with O-ring, and placed at a vertical irradiation station. The non-self-supported target powder was able to keep its thickness by the force of gravity without any solidification process [1]. Irradiations were performed by NIRS AVF-930 cyclotron with 34 MeV alpha particles at 10 A for 2 h. After the irradiation, 0.5N-HCl was directly introduced into the target vessel to dissolve CaO target. Then, 6%-NH3 solution was similarly introduced into the target vessel to adjust pH of mixed solution at around 9, and recovered to the hotcell through a Teflon tubing (~15 m) by means of N2 pressure. The recovered solution was loaded into a chelating resin (InertSep ME2, 120 mg, GL Sciences, Japan) to trap 43Sc. The resin was washed with 0.05N-HCl to remove parasitic Ca2+; then 43Sc was eluted by 0.5N-HCl as the final product.Results: The yield of purified 43Sc was 1.04 GBq (28 mCi) which obtained within 1 h from EOB. Activity balance of the final product was reached to 75% of whole produced, and the radionuclidic purity of 43Sc showed 95% or higher till 17 h from EOB. By-produced nuclides found in the 43Sc product were, for example 44mSc(58.6 h, 0.0051% vs 43Sc), 44Sc(3.93 h, 3.2%), 46Sc(83.8 h, 0.0043%), and 47Sc(3.35 d, 0.034%) at 2 h from EOB. An estimation with a special emphasis on the production of 47Sc by using above result, the expected yield of 47Sc was 0.7 MBq (19 Ci)/Ah from enriched, i.e. 99 atom% 44Ca target. Conclusion: 43Sc was remotely obtained by irradiation of natCaO that showed acceptable yield and purity, and this system can be applied to the production of 47Sc.Acknowledgements: The authors are grateful to the NIRS cyclotron staff for their excellent operation of AVF-930.References: [1] Nagatsu, K. et al. (2012) Nucl. Med. Biol. 39, 1281–1285
21st International Symposium on Radiopharmaceutical Sciences

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