More than one way to better care: the indispensable role of reactors and particle accelerators
When you are being diagnosed or treated in the hospital with medical isotopes, these radioactive elements have already travelled a long distance. They originate from a particle accelerator (for example a cyclotron), which is often located near or within hospitals, or from a reactor. A small number are produced using new experimental technologies. Why are there various ways of producing medical isotopes? And do we need all of them? The answer is yes. And the reason lies in physics.
Medical isotopes are artificially produced radioactive elements: they do not occur in nature (or not in significant quantities). They can only be produced in advanced facilities. Medical isotopes are created by modifying the atoms of a chosen element: we add particles or remove particles. We do this to make the substance unstable. Specific elements emit radiation when becoming unstable. This radiation is then used in nuclear medicine to detect or treat diseases.
Today, forty medical isotopes are known and used in nuclear medicine: 16 of them are produced most efficiently, or exclusively, in a reactor, 16 medical isotopes are produced most efficiently, or exclusively, in a cyclotron, and the remaining 8 isotopes can be generated either in a cyclotron or in a reactor.
This deviation is governed by the laws of physics. As mentioned, the essence of the production process is adding or removing a particle from an atom, causing it to become unstable. Adding or removing a particle is done by making small particles collide with the atom. These small particles are neutrons, protons or, in rare cases, photons. Each of these particles has a specific effect on the target material: the material either captures a particle or repels it.
The addition of neutrons can, in principle, only happen in a reactor, while the removal of a neutron can, in principle, only happen in a particle accelerator such as a cyclotron. There is also a gray area: due to the natural properties of certain elements, some isotopes (around 20 percent) can be produced in either a reactor or a cyclotron. A tie, then?
Both production methods have important differences. A particle accelerator efficiently produces short-lived isotopes such as fluorine-18, which is widely used in PET scans for cancer diagnosis, because it decays quickly, and its radiation can be measured easily. Because a short-lived isotope has a limited shelf life, they have to be produced close to the patient. In addition, a cyclotron is limited to producing only one type of product at a time. In a reactor you can produce much larger volumes and often generate multiple isotopes simultaneously, because many reactions take place in parallel.
Being able to expose elements to both particle accelerators and reactors, offers nuclear medicine enormous possibilities for diagnosing and treating patients – now and in the future. It enables the continuous development of new therapies that can lead to improved treatments for life-threatening diseases.
The arrival of the PALLAS-reactor is a key driver of innovation in healthcare. By ensuring a stable and reliable supply of medical isotopes, the reactor opens the door to even more powerful cancer treatments in the years ahead.
Picture: PALLAS construction site november 2025
