Eighty-three years after the cyclotron was first patented, science is taking a fresh look at the atom smasher as a potential producer of the radioactive isotope that helps doctors diagnose millions of patients across the world every year.
The cyclotron was patented on this day in 1934 by Ernest Lawrence, a professor at the University of California at Berkeley. The physicist took home a 1939 Nobel Prize for his invention, whose greatest significance in the words of the Nobel committee was in the “production of artificially radioactive substances.”
“Lawrence’s first cyclotron, all of 4 inches in diameter, was small enough to hold in one hand,” writes the Science & Technology Review. “This tiny apparatus of brass and sealing wax, which cost about $25 to build, successfully accelerated hydrogen molecular ions to 80,000 volts.”
The Review is run out of the Lawrence Livermore National Laboratory. The lab was named in honor of Lawrence’s prestigious career, which mostly unfolded in the “Golden Age of Particle Physics” that Lawrence’s work helped to usher in.
In this climate, experiments with the cyclotron quickly helped scientists to discover many of the radioisotopes used in nuclear medicine today, including technetium-99, commonly called the “workhorse of nuclear medicine” because of how many places it’s used. A doctor injects a small amount of radioactive isotope into a patient's body. The isotope is absorbed by the patient's body and then picked up by scanners that detect radiation. In this way, technetium-99 can be used to see inside people's bodies in procedures from heart stress tests to bone scans. Its short half-life (only six hours) means that it disappears from the body quickly.
But for the rest of the twentieth century, the isotopes first produced using the simple cyclotron were made at uranium-powered nuclear reactors. This all started to change in the late 2000s, when the aging reactors that produced technetium-99 experienced technical problems, and the global medical supply of an essential diagnostic tool was threatened. The manager of one of those reactors told Richard Van Noorden for Nature that it was “the isotope equivalent of an electricity blackout.”
Many hospitals were out of technetium-99 for weeks, Van Noorden wrote. And it was only the first time. “The crash made it painfully clear that the world’s medical-isotope supply chain was dangerously fragile, relying heavily on about four government-subsidized reactors built in the 1950s and 1960s,” he wrote. And now that North America’s only isotope-producing reactor has halted production, the supply is more under threat than ever.
During this ongoing crisis, some proposed a solution that involved going back to the beginning: the cyclotron. One solution emerged in Canada, whose Chalk River reactor is one of the main global producers of technetium-99. Researchers across the country have collaborated on pilot projects using local cyclotrons to produce the medical isotopes that used to be produced centrally at the reactor, but the technology to produce the isotopes in large enough quantities for the medical community is not fully ready yet.
Some hospitals around the world currently have medical cyclotrons, but they perform other tasks in nuclear medicine and can’t produce technetium-99.
TRIUMF, the University of British Columbia-based laboratory leading the charge, argues on its website that the innovation is actually an improvement on the current system because it cuts down on waste. Technetium-99 only has a six-hour half-life, so much of it “ends up being wasted as it decays during shipment from far-flung reactors to pharmaceutical companies to hospitals,” the website reads. Installing local cyclotrons to produce technetium-99 decreases the waste and will make medical isotope procedures less expensive, according to the website.
Think of their proposal as the 100-Mile Diet, just for medical isotopes.