What is a Cyclotron?

The process begins when charged particles like positive or negative ions are injected into the centre of the cyclotron, where they start to move outward in a spiral path.

Inside the cyclotron, are two hollow, D-shaped metal electrodes called ‘dees’, placed between the poles of a large magnet. The magnetic field forces the particles into a circular path, while an alternating electric field boosts the particle’s energy every time it crosses the gap between two dees. As the particles gain speed and energy, they continue to spiral outward.

Once the particles reach the outer edge of the cyclotron, they are directed toward a target. When the accelerated particles collide with the target, they can cause nuclear reactions, producing radioactive isotopes.

Nearly a century after their invention, cyclotrons remain in high demand because of their reliability, efficiency, and versatility.

While all particle accelerators share a common goal - boosting the energy of particles - they achieve this in different ways.

Cyclotrons accelerate particles in a spiral path using a constant magnetic field and an alternating electric field. The spiral design is one of the cyclotron’s main advantages. It allows for continuous acceleration in a relatively small space. As a result, cyclotrons are typically smaller, often room-sized, and more affordable than other accelerators. They can be installed in hospitals or university labs without needing massive facilities. Cyclotrons are also well-suited for producing specific types of radioactive isotopes needed in medical imaging and cancer treatment, and for other localized applications in research or industry.

In contrast, linear accelerators, or linacs, propel particles in a straight line using a series of electric fields. While linacs can be simpler in design, they often require much more space to achieve the same energy levels as a cyclotron. They are commonly used in radiotherapy, where precise targeted beams of radiation are used to treat tumours.

Another type of accelerator is the synchrotron - a much larger and more complex machine found in national research centres. Like cyclotrons, they guide particles in a circular path, but with variable magnetic fields and radiofrequency acceleration. These machines can reach extremely high energies, making them suitable for research in particle physics, materials science, and even drug development. However, due to their size and cost, they are typically used by national or international research centres, not hospitals or small labs.

Each plays an important role, but cyclotrons remain the most widely deployed and user-friendly accelerators for routine medical applications.

Cyclotrons power many of the tools, treatments, and discoveries that improve our daily lives . They are compact, efficient, and relatively easy to operate, making them ideal for producing medical radioisotopes; unstable atoms that emit radiation and are used to diagnose and treat cancer.

One important consideration in radioisotope production is the effective lifespan of the isotopes - how long they remain radioactive and suitable for medical use after production.

Radioisotopes used in treatment generally have half-lives lasting a few days, which allows them to effectively kill cancer cells. They can also be transported from production sites to hospitals and treatment centres over this short time span.

In contrast, other diagnostic isotopes have extremely short half-lives, meaning they decay rapidly lose effectiveness within hours, and cannot travel long distances.

Cyclotrons are valued as they can produce isotopes onsite or nearby, ensuring patients receive fast, accurate diagnoses and timely treatment.

These scans help doctors detect diseases such as cancer, Alzheimer’s, and cardiovascular conditions such as heart disease at early stages with high accuracy. Early detection improves diagnosis and supports better treatment planning.

Cyclotrons also help in treating cancer by producing special radioactive drugs used in targeted radionuclide therapy. In this type of treatment, radiation is delivered directly to cancer cells, which helps destroy them while minimizing damage to healthy tissue.

Cyclotrons play a vital role in modern infrastructure, healthcare and research.

Today, thousands of cyclotrons are in operation around the world, especially in hospitals, cancer centres and research facilities. As demand for non-invasive diagnostic tools like PET and SPECT scans grows, so does the need for cyclotrons and research facilities seeking to produce radioisotopes without uranium.

Before, many medical radioisotopes were produced in nuclear reactors using uranium, a process that can generate long-lived radioactive waste and raises safety and security concerns. To find cleaner and safer ways to produce these important materials, countries are turning to cyclotrons that can make radioisotopes without using uranium.

Newer generations of compact, low-energy cyclotrons make it possible for smaller hospitals and institutions to access the technology. Researchers continue to explore new uses of radioisotopes in environmental science, materials engineering and homeland security.

While the core principle behind the cyclotron has remained unchanged since the 1930s, this vital technology continues to evolve and adapt to the needs of the 21st century.

• The IAEA supports countries around the world, especially those with limited resources to access, operate and benefit from cyclotron technology.
• It guides the infrastructure development of cyclotron facilities, advising on equipment specifications and ensuring safety standards are met.
• ?The IAEA trains medical physicists, engineers and nuclear medicine professionals to ensure that countries have skilled personnel to operate cyclotrons safely and effectively.
• The agency also coordinates Coordinated Research Projects, bringing together experts from around the world to develop new isotopes, improve cyclotron performance, and explore new medical and industrial applications.
• The IAEA Database of Cyclotrons for Radionuclide Production and Radiopharmacy Database offers policy makers, researchers, technical experts and students an overview of the radionuclides produced using cyclotrons and their use for different radiopharmaceutical preparations for patient care and treatment.??