The Paul Scherrer Institute (PSI) is Switzerland’s largest research insitute for natural and engineering sciences, conducting cutting-edge research in three main fields: matter and materials, energy and the environment and human health. PSI develops, builds and operates complex large research facilities. Every year, more than 2400 scientists from around the world come to PSI to use its unique facilities to perform experiments that are not possible anywhere else.

PSI runs a High Intensity Proton Accelerator (HIPA) amenity as part of its Large Facilities, where three accelerators are connected in series to increase proton beam energy. A Cockcroft-Walton accelerator accelerates protons at 870 keV to the Injector II separated sector cyclotron, where the protons are accelerated to 72 MeV at an intensity of ~2.5 mA to the Ring cyclotron. The Ring cyclotron accelerates the protons further to 590 MeV, which is then sent down the beam line to various experimental vaults, before the remainder of the beam is collected in a Pb beam dump, which serves as a neutron spallation source for the Swiss Neutron Source (SINQ).

Along the beam line between Injector II and the Ring cyclotron, the Radionuclide Development/production irradiation station (known as IP2) gleans ~50 μA protons from Injector II, by means of a beam splitter, into the IP2 target station. These protons irradiate various targets towards the production of exotic radionuclides intended for medical purposes.

Many radiometals currently used in nuclear medicine are for the diagnosis of disease, with the most popular means of detection being Positron Emission Tomography (PET). These positron emitters are easily produced at low proton energies using medical cyclotrons, however, development using such facilities are rare. The irradiation station at IP2 is used for ~8 months of the year and, as a result, is not considered for use in a commercial setting. The system is still put to good use, however, towards the development of novel, non-standard radiometals.

SINQ houses a ‘rabbit’ system for neutron irradiation of materials inserted into a beam tube. Two pairs of rabbit system tubes reach into the volume of the moderator vessel. The pair of tubes closest to the target (PNA) is utilized for radionuclide production and development, which includes the production of radioactive tracers towards developing chemical separation methods (thermal neutron flux: 2x1013 n cm–2s–1mA–1). Over the last decade, PNA has been predominantly used for the development and upscale of 161Tb production.

The Center for Radiopharmaceutical Sciences (CRS) is one of the few research organizations in Europe that is able to produce radiopharmaceuticals not only for research purposes but also for clinical trials. The Radionuclide Development group is a joint group between CRS and the Laboratory of Radiochemistry (LRC). The research focus of the group is on the production and chemical separation of novel radionuclides for innovative radiopharmaceuticals from targetry to preclinical applications. Radionuclide Development collaborates closely with other CRS research groups specializing in preclinical studies using novel radionuclides.

PSI is a partner of the PRISMAP consortium and avails its facilities for projects involving radionuclides such as 44/43Sc, 44Sc, 64Cu and 161Tb. PSI is also a Work Package leader in the development of novel radiolanthanides towards potential medical/preclinical research.

Recently, a large-facility grant proposal was submitted to the ETH Rat and Swiss National Science Foundation (entitled IMPACT -Isotope and Muon Production using Advanced Cyclotron and Target technologies; see https://www.psi.ch/impact). The concept involves the installation of a spallation and mass separation facility (ISOL) to allow production of high activities of radionuclides that are currently difficult to obtain (TATTOOS –TArgeted Tumour Therapy and Other Oncological Solutions). Should this proposal be granted, PSI will be preparing towards its construction and preparation, with the facility expected to be operational in mid-2028. It is aimed to produce desired alpha emitters towards radiopharmaceutical application and Targeted Alpha Therapy (149Tb initially, to be followed by 225Ra/225Ac).