Technetium-99m (^99mTc) is the most used radionuclide worldwide in nuclear medicine for diagnostic imaging procedures. ^99mTc is typically extracted from portable generators containing ⁹⁹Mo, which is produced normally in nuclear reactors as a fission product of highly enriched Uranium material. Due to unexpected outages or planned and unplanned reactor shutdown, significant ^99mTc shortages appeared as a problem since 2008 The alternative cyclotron-based approach through the ¹⁰⁰Mo(p,2n)^99mTc reaction is considered one of the most promising routes for direct ^99mTc production in order to mitigate potential ⁹⁹Mo shortages. The design and manufacturing of appropriate cyclotron targets for the production of significant amounts of a radiopharmaceutical for medical use is a technological challenge. In this work, a novel solid target preparation method was developed, including sputter deposition of a dense, adherent, and non-oxidized Mo target material onto a complex backing plate. The latter included either chemically resistant sapphire or synthetic diamond brazed in vacuum conditions to copper. The target thermo-mechanical stability tests were performed under 15.6 MeV proton energy and different beam intensities, up to the maximum provided by the available GE Healthcare (Chicago, IL, USA) PET trace medical cyclotron. The targets resisted proton beam currents up to 60 µA (corresponding to a heat power density of about 1 kW/cm²) without damage or Mo deposited layer delamination. The chemical stability of the proposed backing materials was proven by gamma-spectroscopy analysis of the solution obtained after the standard dissolution procedure of irradiated targets in H₂O₂.

Magnetron sputtering is proposed here as an innovative method for the deposition of a material layer onto an appropriate backing plate for cyclotron solid targets aimed at medical radioisotopes production. In this study, a method to deposit thick, high-density, high-thickness-uniformity, and stress-free films of high adherence to the backing was developed by optimizing the fundamental deposition parameters: sputtering gas pressure, substrate temperature, and using a multilayer deposition mode, as well. This method was proposed to realize Mo-100 and Y-nat solid targets for biomedical cyclotron production of Tc-99m and Zr-89 radionuclides, respectively. The combination of all three optimized sputtering parameters (i.e., 1.63 × 10⁻² mbar Ar pressure, 500 °C substrate temperature, and the multilayer mode) allowed us to achieve deposition thickness as high as 100 µm for Mo targets. The 50/70-µm-thick Y targets were instead realized by optimizing the sputtering pressure only (1.36 × 10⁻² mbar Ar pressure), without making use of additional substrate heating. These optimized deposition parameters allowed for the production of targets by using different backing materials (e.g., Mo onto copper, sapphire, and synthetic diamond; and Y onto a niobium backing). All target types tested were able to sustain a power density as high as 1 kW/cm² provided by the proton beam of medical cyclotrons (15.6 MeV for Mo targets and 12.7 MeV for Y targets at up to a 70-µA proton beam current). Both short- and long-time irradiation tests, closer to the real production, have been realized.

Nuclear medicine (NM) procedures for diagnosis and treatment of disease are performed routinely in hospitals throughout the world. These involve preparation and administration to patients of pharmaceuticals labelled with radioactive material. There is potential for incidents to occur, involving unintended exposures of patients or staff members, throughout all stages of a procedure. The International Atomic Energy Agency (IAEA) and the World Health Organisation highlighted the need for improvement in prevention of medical radiation incidents and accidents in the Bonn Call-for-Action in 2012. An IAEA Technical Meeting was held on prevention of unintended exposures and accidents in NM in 2018 to address the issue. Exposures can take place at any time when radioactive material is being produced and used, and the risk continues after procedures have been completed. Thus there is potential for staff or members of the general public to be exposed, as well as patients. This paper sets out guidelines for incident prevention based on presentations and discussions at the meeting, and review of reports from the literature. It deals with potential incidents in in-house radionuclide production, radiopharmaceutical preparation, administration to patients, and following a procedure, as well as aspects in management of radioactive materials. Special attention has been paid to therapeutic procedures, as these have the potential to cause more harm to patients from erroneous administrations, including tissue reactions from extravasation of radiopharmaceutical, and could lead to significant contamination events. Administration of NM therapy is generally contraindicated in pregnancy. Identification of any patient who may be pregnant is crucial and it might be necessary to verify this with a pregnancy test for patients within the age band considered to be fertile. Inclusion of NM therapy incidents in the IAEA automated reporting system SAFRON is recommended. In summary, the paper aims to highlight errors that could occur during different phases of NM procedures in order to aid prevention of incidents. The value of periodic audit in evaluating systems in place on a regular basis is emphasized. Approaches to incident investigation and follow-up are described, and the need to ensure corrective action is taken to address any deficiencies stressed.