Abstract
44Sc has favorable properties for cancer diagnosis using Positron Emission Tomography (PET) making it a promising candidate for application in nuclear medicine. The implementation of its production with existing compact medical cyclotrons would mean the next essential milestone in the development of this radionuclide. While the production and application of 44Sc has been comprehensively investigated, the development of specific targetry and irradiation methods is of paramount importance. As a result, the target was optimized for the 44Ca(p,n)44Sc nuclear reaction using CaO instead of CaCO3, ensuring decrease in target radioactive degassing during irradiation and increased radionuclidic yield. Irradiations were performed at the research cyclotron at the Paul Scherrer Institute (~11 MeV, 50 µA, 90 min) and the medical cyclotron at the University of Bern (~13 MeV, 10 µA, 240 min), with yields varying from 200 MBq to 16 GBq. The development of targetry, chemical separation as well as the practical issues and implications of irradiations, are analyzed and discussed. As a proof-of-concept study, the 44Sc produced at the medical cyclotron was used for a preclinical study using a previously developed albumin-binding prostate-specific membrane antigen (PSMA) ligand. This work demonstrates the feasibility to produce 44Sc with high yields and radionuclidic purity using a medical cyclotron, equipped with a commercial solid target station.
Highlights
The concept of theragnostics [1] in nuclear medicine is based on the use of radionuclides of preferably the same element to enable the application of chemically identical radiopharmaceuticals for both diagnosis and therapy [2]
The physical half-life of 44 Sc makes it attractive to be produced from a commercial perspective, as it is easier to distribute than the likes of 68 Ga radiopharmaceuticals [8]
prostate-specific membrane antigen (PSMA)-ALB-02 was readily achieved with was used for test targets.ofTargets for 44 Sc production were prepared with enriched Ca calcium carbonate
Summary
The concept of theragnostics [1] in nuclear medicine is based on the use of radionuclides of preferably the same element (radioisotopes) to enable the application of chemically identical radiopharmaceuticals for both diagnosis and therapy [2]. Scandium-44 could be used as an alternative to the currently used 68 Ga (T1/2 = 68.3 min), with a longer half-life which would improve image. Molecules 2020, 25, 4706 quality [7,8], when images are recorded at later time points (when tumor-to-background ratios are enhanced) [9]. This is desirable for imaging with radiopharmaceuticals with a longer biological half-life [6]. The physical half-life of 44 Sc makes it attractive to be produced from a commercial perspective, as it is easier to distribute than the likes of 68 Ga radiopharmaceuticals [8]
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