Speaker
Summary
Introduction
The terbium radioisotope quadruplet or “sisters” have gained international attention, as they have attributes suited for diagnostics and therapy in nuclear medicine [1]. Paul Scherrer Institute (PSI) has been at the centre of Tb-radioisotope research for over a decade. Through the PSI-ISOLDE collaboration, researchers collected and purified 149Tb (α- and β+-emitter, T1/2 = 4.1 h), used for preclinical therapy studies and PET imaging, 152Tb (β+-emitter, T1/2 = 17.5 h), for preclinical and clinical PET imaging and 155Tb for preclinical SPECT imaging, respectively. The research facility has also been at the forefront of development of scandium radioisotopes, with accelerator development towards production of PET nuclides 44Sc (T1/2 = 4.04 h) and 43Sc (T1/2 = 3.89 h), respectively [2].
Description of the Work
Using high-energy protons to generate spallation reactions from tantalum targets, mass-separated beams of 149Tb and 152Tb, respectively, were implanted at ISOLDE-CERN into Zn-coated Au/Al/Ta foils. Significant activities were transported to PSI for processing.
PSI’s IP2 irradiation station, which receives 72 MeV protons from the Injector II cyclotron, was utilized to produce 155Tb using enriched 155/156Gd target material, as well as 43/44Sc by irradiating enriched 44Ca target material [2].
At PSI, the chemical separation in question was performed using a separation system, specifically designed and built for the nuclide in question, and manipulators in a hot cell [3]. The target material containing the desired nuclide was dissolved in acid media and the dissolved nuclides loaded on to a resin column. Impurities were rinsed from the column and the desired nuclide eluted using dilute media. As an addition, the product eluent was passed through a second resin column to ensure concentration of the final product.
High production yields were achieved, and extensive preclinical data produced using 43/44Sc and 149/152/155Tb, respectively. As a result, first-in-human applications were achieved using 152Tb and 44Sc, respectively [1,2].
Conclusions
Due to interest in the Tb sisters and encouraging preclinical results, facilities such as TATTOOS (as part of the Swiss Large Facilities project IMPACT, to be constructed at PSI) are being built in Europe to address the means of producing 149/152/155Tb. Following the recent successful clinical application of reactor-produced 161Tb radiopharmaceuticals in Swiss clinics, focus turns to the clinical translation of 44Sc, as part of the EU IHI Thera4Care project.
References
[1] C. Müller & N. P. van der Meulen. In Beyond Becquerel and Biology to Precision Radiomolecular Oncology: Festschrift in Honor of Richard P. Baum, 2024, Springer Books. DOI: 10.1007/978-3-031-33533-4_23.
[2] N. P. van der Meulen & Z. Talip. In Encyclopedia of Nuclear Medicine and Molecular Imaging (Reference Module in Biomedical Sciences), 2021, Elsevier. DOI: 10.1016/B978-0-12-822960-6.00052-1.
[3] P. V. Grundler, R. Eichler, Z. Talip, et al. CHIMIA (2020), 74 (12), 968. DOI: 10.2533/chimia.2020.968
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