Production of ¹⁶¹Tb Radionuclide

Targeted radionuclide therapy (TRT), the use of radiopharmaceuticals to target and irradiate tumour cells, has become an important method for cancer treatment. The radiolanthanide Lutetium-177 (¹⁷⁷Lu) is a medium-energy beta radionuclide with a suitable electron energy range for treatment of small tumors, and has been widely used in clinical targeted radionuclide therapy. The radiolanthanide terbium-161 (¹⁶¹Tb) isotope has similar decay properties, biochemical properties, and in vivo characteristics to ¹⁷⁷Lu, and it releases more Auger electrons and internal conversion electrons than ¹⁷⁷Lu. It has been proposed, and preclinically demonstrated, that ¹⁶¹Tb is a better alternative to ¹⁷⁷Lu for the treatment of small prostate cancer lesions. According to the conferences and published articles on nuclear medicine in recent years, more and more attention has been paid to the preparation of ¹⁶¹Tb nuclides and the development of its labeled drugs in the field of radiopharmaceuticals. However, there is no mature production process for ¹⁶¹Tb internationally, which has seriously hindered the clinical research of ¹⁶¹Tb-labeled drugs. Currently, there are two main methods for the preparation research of ¹⁶¹Tb. One is to produce ¹⁶¹Tb through an accelerator, and the other is to produce carrier-free ¹⁶¹Tb using a high-throughput reactor or a fission neutron source via the reaction ¹⁶⁰Gd(n, γ)¹⁶¹Gd→¹⁶¹Tb. Commercial production of ¹⁶¹Tb using an accelerator is very difficult. The most common method internationally is to irradiate enriched ¹⁶⁰Gd₂O₃ target material with a reactor or a fission neutron source to produce carrier-free ¹⁶¹Tb. According to the investigation, there are several research institutes or companies at home and abroad are carrying out relevant research on the preparation of ¹⁶¹Tb. Chengdu Gaotong Isotope Co., Ltd. (CNNC) used enriched ¹⁶⁰Gd₂O₃ target material irradiated by a reactor with neutron flux of about 1-2×10¹⁴ n·cm⁻²·s⁻¹ to separate a large amount of irradiated ¹⁶⁰Gd by a two-column method to prepare no carrier-added ¹⁶¹TbCl₃ nuclide solutions. Chengdu Gaotong Isotope Co., Ltd. has carried out many experiments on the preparation of ¹⁶¹Tb from ¹⁶⁰Gd target material enriched. After separation and purification, the radionuclide purity, radiochemical purity and activity of ¹⁶¹TbCl₃ nuclide solution were detected by high purity germanium gamma spectrometer, activity meter and other instruments and equipment. The results showed that the radionuclide solution of ¹⁶¹TbCl₃ with radionuclide purity greater than or equal to 99.9%, radiochemical purity greater than 99% and chemical purity was obtained after the separation and purification of ¹⁶¹Gd target material enriched by irradiation in the reactor.