Scandium-47 is a promising particle emitter that has been suggested as a candidate for radiotheranostics. Thus, better understanding of optimum irradiation parameters, radioactivity yields and possible impurities during its production is of paramount importance. The theoretical calculation of the end-of-bombardment (EOB) results is performed using Microsoft Excel following the calculation of the excitation function obtained from the TALYS software and the stopping power obtained from the SRIM software can be accessed for free. According to the TALYS code calculations, the threshold energy for 47Sc production was 8.39 MeV, whereas the maximum cross-section (879 mbarn) occurred at proton incident energy of 17 MeV. The calculated EOB yield for 48Ca(p,2n)47Sc nuclear reaction at 60 MeV proton energy was found to be 449 MBq/μAh, which was suitable quality for typical radionuclide production. Besides, three radionuclides, i.e. 48Sc, 46Sc and 47Ca were predicted to be the main impurities in the 47Sc production. However, in order to minimize the production of 48Sc, 46Sc and 47Ca impurities radionuclide the safest and optimum proton energy should be between 23 and 30 MeV, which can be achieved using the available 26 MeV cyclotron. This study can be used as a reference for future 47Sc production when proton beams of up to 60 MeV are employed.
Since Zirconium-89 (89Zr or Zr-89) decays by emitting positron with a half-life of 78.4 hours, it has been suggested as a diagnostic radioisotope for cancer. Normally, Zirconium-89 is generated by irradiating an enriched yttrium-89 (89Y or Y-89) target with protons via 89Y(p,n)89Zr nuclear reaction. Optimum proton energy employed to produce high Zr-89 yield and low radioactive impurities is required to be determined so that it meets the requirements for clinical use. In this work, a Y-89 target was bombarded with variable proton energies ranging from 11 to 30 MeV. The Zr-89 radioactivity yields dan radioactive impurity yields were calculated using the CalcuYield code, in which the proton beam current was set to be 1 μA while the target was bombarded for 1 hour. Based on the CalcuYield calculations, the radioactivity yield of Zr-89 produced by 11 MeV protons was 41.18 MBq/μAh, whereas the yield increased significantly to 166.76 MBq/μAh when the Y-89 target was bombarded with 30-MeV protons. The higher Zr-89 radioactivity yields also resulted in higher radioactive impurities, which could be of concern when applied to patients. By assuming that the radioactive impurities came from proton interactions with the Y-89 target, it was found that the 11 and 13 MeV proton-bombarded Y-89 target resulted in no radioactivity impurities. The radioactive impurities became significantly high when greater than 18 MeV protons were employed. These estimated results can be employed as a benchmark for the coming Zr-89 radionuclide generation applicable for radioimmuno-PET imaging.
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