A clinician may have a strong hunch about a patient’s disease, but imaging is often essential to turn that suspicion into a confident diagnosis. Accordingly, technologies such as positron-emission tomography (PET) have become invaluable for assessing heart disease, cancer, neurological disease and other life-threatening conditions. Useful as it is, PET imaging is not readily available in small cities, due to the size and cost of devices that produce radioisotopes, which is key for the process. But a team of Saudi and American researchers is working towards alternative technologies to produce radioisotope using smaller and cheaper devices.
PET imaging requires easy access to radioisotopes such as fluorine-18 (18F) and nitrogen-13 (13N), which are used to label tissues affected by disease. This can be problematic in rural communities and smaller cities, which often lack the means to support the pricy cyclotron particle accelerators that produce such isotopes. “Here in Riyadh, we have these huge cyclotrons available and running,” explains Ayash Alrashdi, director of the National Center for Accelerator Technology at KACST. “But all of the small cities around the kingdom do not have this technology, and the big issue is size and cost.”
An ongoing initiative by KACST and international collaborators aims to solve this problem with an innovative compact cyclotron design. This smaller-scale accelerator should give smaller hospitals ready access to on-site radioisotope production, and could pave the way for broader availability of cutting-edge radiation-based therapies in the future.
Small but powerful
Cyclotrons direct beams of particles along a circular track, with their movement directed and accelerated by powerful magnets. These magnets can be bulky and expensive—the entire apparatus can weigh many tons and imposes serious design and resource demands on a facility. “You will need reinforced concrete to hold this weight, and you will need shielding, and you will need huge cables and huge electricity to make this huge machine work,” says Alrashdi. This is simply not practical for medical centres with limited space, resources and engineering expertise—and as a consequence, many patients in Saudi Arabia must travel across the country to Riyadh or Jiddah to receive the PET imaging they require.
The challenge for the KACST team was therefore to identify innovative ways to shrink these powerful systems down to a size and cost that would make them a practical investment for more institutions. “We are minimizing the size of a cyclotron from a current weight of 30 to 40 tons to 3 or 4 tons maximum,” says Alrashdi. To achieve this downsizing, his team of engineers replaced conventional magnets with coil-shaped superconducting magnets composed of ultra-thin filaments of niobium and titanium. This design provides the large surface area needed to generate a powerful magnetic field. The resulting field is twice as powerful as that generated in a conventional cyclotron, enabling the production of an accelerated beam with an energy of 12 megaelectron-volts (MeV) in a system with a far smaller footprint.
Despite these design innovations, Alrashdi notes that his team had to overcome some considerable hurdles to get all of these components working in a compact package. For example, superconductor systems tend to run hot, but need to be maintained at an extremely low temperature—just a few degrees above absolute zero—for the particle accelerator to operate properly. This required the design of an innovative cryogenic cooling system, alongside the sophisticated beam-generator and superconductor elements. “Combining everything in this design was the biggest challenge,” says Alrashdi.
Accelerators for all
His team has made excellent progress in overcoming these difficulties and should unveil a fully assembled first-generation system by July 2019. “This will allow us to have medical radioisotopes available on demand,” says Alrashdi.
Upon demonstrating the successful performance of their prototype, his center will be working in conjunction with the Saudi Ministry of Health to scale up manufacturing to deploy their compact cyclotrons to cities around the kingdom. Alrashdi anticipates that they should be able to accommodate the national demand for radioisotopes within the next five years.
This program has been an international effort from the beginning, with a team that equally comprises Saudi and US engineers and researchers. Other countries have also taken notice of the KACST compact cyclotron program: Both China and Germany have reached out to the Ministry of Health. Alrashdi says his center is now preparing to sign a memorandum of understanding with an organization that intends to purchase as many as 10 compact accelerators in the coming year. “This is going to be a big revolution in the cyclotron area,” says Alrashdi.
But this may just be the beginning. Alrashdi and his colleagues ultimately hope to push the limits of this compact design to produce small-scale cyclotrons that can generate far more powerful particle beams—as much as 200 MeV, in contrast to the 12 MeV produced in the current system. Such systems could be extremely valuable for therapeutic applications such as proton therapy, in which powerful particle beams are precisely targeted to eradicate tumor cells with minimal damage to the surrounding healthy tissue.
“Right now, there only a few proton therapy facilities around the world,” says Alrashdi. Cost is again the main obstacle here, as this treatment approach requires far more powerful accelerators than are required for the manufacture of radioisotopes for imaging. The concept of a miniaturized system that can achieve this kind of power output is therefore deeply appealing. “With a low cost, I think we will have a lot of these proton therapy facilities around the world to treat sick people,” says Alrashdi. “This, I think, is the future.”