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.

¹⁵⁵Tb [t_1/2 = 5.32 d, E_γ = 87 keV (32%); 105 keV (25%) (IAEA, 2021)] is a novel promising radionuclide for theranostic applications in nuclear medicine. Its physical properties make it suitable for single photon emission computed tomography (SPECT) imaging, while its chemistry allows it to be used as a diagnostic partner for therapeutic radiolanthanides or pseudo-radiolanthanides, such as ¹⁷⁷Lu and ⁹⁰Y. Moreover, ¹⁵⁵Tb could be used as a precise diagnostic match for the β^--emitter ¹⁶¹Tb, opening doors for the true theranostics concept. The availability of ¹⁵⁵Tb in quantity and quality suitable for medical applications is an open issue and its production with medical cyclotrons via the ¹⁵⁵Gd(p,n)¹⁵⁵Tb and ¹⁵⁶Gd(p,2n)¹⁵⁵Tb nuclear reactions represents a possible but challenging solution. For this purpose, an accurate knowledge of the production cross sections is mandatory. In this paper, we report on the measurement of the production cross sections of ¹⁵⁵Tb and other terbium radionuclides formed by proton irradiation of ^natGd₂O₃, ¹⁵⁵Gd₂O₃ and ¹⁵⁶Gd₂O₃ enriched targets, performed at the Bern University Hospital cyclotron laboratory. On the basis of the obtained results, the production yield and purity were calculated to assess the optimal irradiation conditions. The results of several production tests are also presented.

The availability of novel radionuclides plays a fundamental role in the development of personalized nuclear medicine. In particular, there is growing interest in pairs formed by two radioisotopes of the same element, the so-called true theranostic pairs, such as ^61,64Cu/⁶⁷Cu, ^43,44Sc/⁴⁷Sc and ¹⁵⁵Tb/^149,161Tb. In this case, the two radionuclides have identical kinetics and chemical reactivity, allowing to predict whether the patient will benefit from a therapeutic treatment on the basis of nuclear imaging data. ⁴⁷Sc [t_1/2 = 3.349 d, E [Formula: see text] = 440.9 keV (68.4%); 600.3 keV (31.6%), E_γ = 159.4 keV (68.3%)] is a promising radionuclide for theranostic applications in nuclear medicine. Its physical characteristics make it suitable for radionuclide therapy and allow SPECT imaging during treatment. Moreover, ⁴⁷Sc is foreseen as the therapeutic partner of the β⁺-emitters ⁴³Sc and ⁴⁴Sc, both under study for PET imaging, opening new avenues towards the true theranostics concept. ⁴⁷Sc can be produced by proton irradiation of an enriched ⁵⁰Ti oxide target with a medical cyclotron equipped with a solid target station. To optimize the production yield and the radionuclidic purity, an accurate knowledge of the production cross sections is necessary. In this paper, we report on measurements of the production cross section of ⁴⁷Sc and ⁴⁶Sc using enriched ⁵⁰Ti titanium oxide targets, performed at the Bern University Hospital cyclotron laboratory. On the basis of the obtained results, a study of the production yield and purity was performed to assess the optimal irradiation conditions. A production test was also carried out to confirm these findings.

The availability of novel medical radionuclides is a key point in the development of personalised nuclear medicine. In particular, copper radioisotopes are attracting considerable interest as they can be used to label various molecules of medical interest, such as proteins and peptides, and offer two of the most promising true theranostic pairs, namely ⁶¹Cu/⁶⁷Cu and ⁶⁴Cu/⁶⁷Cu. Although ⁶⁴Cu (t_1/2 = 12.7006 h, β⁺: 17.6%, β^-: 38.5%) is nowadays the most commonly used as a diagnostic radionuclide, ⁶¹Cu (t_1/2 = 3.339 h, β⁺: 61%) features more favourable nuclear properties, such as a higher positron decay fraction and the absence of β^- emissions. To date, the production of ⁶¹Cu has been carried out irradiating highly enriched ⁶¹Ni targets with a low energy proton beam. However, the use of the very expensive ⁶¹Ni targets requires an efficient recovery of the target material and makes this method quite inconvenient. Another promising production route is the proton irradiation of natural Zn or enriched ⁶⁴Zn targets, exploiting the (p,α) nuclear reaction. Along this line, a research program is ongoing at the Bern medical cyclotron, equipped with an external beam transfer line and a solid target station. In this paper, we report on cross-section measurements of the ⁶⁴Zn(p,α)⁶¹Cu nuclear reaction using natural Zn and enriched ⁶⁴Zn material, which served as the basis to perform optimized ⁶¹Cu production tests with solid targets.

RadioNuclide Therapy (RNT) in nuclear medicine is a cancer treatment based on the administration of radioactive substances that specifically target cancer cells in the patient. These radiopharmaceuticals consist of tumor-targeting vectors labeled with β^-, α, or Auger electron-emitting radionuclides. In this framework, ⁶⁷Cu is receiving increasing interest as it provides β^--particles accompanied by low-energy γ radiation. The latter allows to perform Single Photon Emission Tomography (SPECT) imaging for detecting the radiotracer distribution for an optimized treatment plan and follow-up. Furthermore, ⁶⁷Cu could be used as therapeutic partner of the β⁺-emitters ⁶¹Cu and ⁶⁴Cu, both currently under study for Positron Emission Tomography (PET) imaging, paving the way to the concept of theranostics. The major barrier to a wider use of ⁶⁷Cu-based radiopharmaceutical is its lack of availability in quantities and qualities suitable for clinical applications. A possible but challenging solution is the proton irradiation of enriched ⁷⁰Zn targets, using medical cyclotrons equipped with a solid target station. This route was investigated at the Bern medical cyclotron, where an 18 MeV cyclotron is in operation together with a solid target station and a 6-m-long beam transfer line. The cross section of the involved nuclear reactions were accurately measured to optimize the production yield and the radionuclidic purity. Several production tests were performed to confirm the obtained results.