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Evaluation of $$^{99}$$Mo/$$^{99m}$$Tc production with irradiated MoO $$_{3}$$ pellets

照射済みMoO $$_{3}$$ペレットによる$$^{99}$$Mo/$$^{99m}$$Tc製造に関する評価

石田 卓也; 椎名 孝行*; 太田 朗生*; 鈴木 善貴; 柴田 晃; 西方 香緒里; 木村 明博; 棚瀬 正和*; 小林 正明*; 佐野 忠史*; 藤原 靖幸*; 土谷 邦彦

Ishida, Takuya; Shiina, Takayuki*; Ota, Akio*; Suzuki, Yoshitaka; Shibata, Akira; Nishikata, Kaori; Kimura, Akihiro; Tanase, Masakazu*; Kobayashi, Masaaki*; Sano, Tadafumi*; Fujihara, Yasuyuki*; Tsuchiya, Kunihiko

$$^{99m}$$Tcは放射性医薬品として最も使われる放射性同位元素の一つであり、親核種である$$^{99}$$Moから生成される。(n, $$gamma$$)方法による$$^{99}$$Mo/$$^{99m}$$Tc製造技術開発を行っているが、本法で得られる$$^{99}$$Moの比放射能は、核分裂方法((n, f)方法)に比べると低く、抽出された$$^{99m}$$Tc溶液の放射能濃度も低いことが欠点である。本研究では、$$^{99m}$$Tc溶液の高い放射能濃度を得るため、$$^{99}$$Mo/$$^{99m}$$Tc分離/抽出/濃縮試験を行った。試験手順として、(1)京都大学原子炉(KUR)で高密度MoO$$_{3}$$ペレットの照射、(2) MEKを用いた溶媒抽出による回収、(3)$$^{99m}$$Tc溶液の精製・濃縮、及び(4)$$^{99m}$$Tc溶液の品質検査を行った。その結果、照射済みMoO$$_{3}$$ペレットを6M-NaOH溶液で溶解し、$$^{99}$$Mo/$$^{99m}$$Tc溶液からの$$^{99m}$$Tc回収率は目標値である80$$pm$$5%を達成した。さらに、得られた$$^{99m}$$Tc溶液の放射性核種純度、放射化学的異物等の検査は、基準値を満足した。

Technetium-99m ($$^{99m}$$Tc) is one of the radioisotopes which are used most as radiopharmaceuticals, and it is obtained from the parent nuclide of Molybdenum-99 ($$^{99}$$Mo). However, the specific radioactivity of $$^{99}$$Mo by (n, $$gamma$$) method is extremely low compared with that by fission method ((n,f) method), and as a result, the radioactive concentration of the extracted $$^{99m}$$Tc solution is also low. Thus, it is necessary for the high radioactive concentration of the $$^{99m}$$Tc solution to develop the $$^{99}$$Mo/$$^{99m}$$Tc separation/extraction/concentration method. In this study, the experiments of $$^{99}$$Mo/$$^{99m}$$Tc production were performed to enhance recovery yields of $$^{99m}$$Tc and to get a high quality of $$^{99m}$$Tc product. The procedures are described as follows. (1) High-density MoO$$_{3}$$ pellets were irradiated in the Kyoto University Research Reactor (KUR). (2) $$^{99m}$$Tc was extracted with MEK. (3) $$^{99m}$$Tc extracted in MEK was purified and concentrated with acidic alumina column. (4) Product of $$^{99m}$$Tc solution was checked in several factors such as radionuclidic and radiochemical purities. The irradiated MoO$$_{3}$$ pellets were dissolved in 6M-NaOH and the $$^{99}$$Mo/$$^{99m}$$Tc solution was treated with the devices. From the results, the $$^{99m}$$Tc recovery yields achieved 80$$pm$$5% of our goal. Finally, the extracted $$^{99m}$$Tc solution passed the quality inspection of six items.

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