The looming problem of a global medical isotope shortage is one step closer to a solution. A Canadian team has developed an upgrade that allows hospital cyclotrons to make a much-needed diagnostic tracer, and has proven it can pump out enough overnight to fulfil a city’s needs the next day.
Most of today’s medical-imaging procedures, such as those used to trace cancer or monitor heart function, employ a radioactive element called technetium-99m (99mTc). But this isotope is hard to produce and has a half-life of just 6 hours, making it impossible to store long-term. Global supplies come mostly from two nuclear reactor facilities: one in Canada, and one in the Netherlands. Both are reaching the ends of their useful lives, and isotope production is scheduled to stop in 2016 and 2015, respectively.
The demand for 99mTc will eventually dry up as a more advanced form of scanning, called Positron Emission Tomography (PET), takes over. This uses different isotopes that can already be manufactured by advanced hospital cyclotrons, but it is more expensive and today used for only a small fraction of scans. In the meantime, governments and researchers are keen to create an alternate supply chain for 99mTc , perhaps using the same cyclotrons that will be needed for PET scans.
In February 2012, a team based at the TRIUMF particle accelerator near Vancouver demonstrated that they could retrofit hospital cyclotrons, such as the one pictured, to do the job. “It’s basically an after-factory add-on,” says Tim Meyer, spokesperson for TRIUMF. Now they have done further work on the needed metal target, making it strong enough to not melt under the heat of the beam, but porous enough to dissolve rapidly in solution so the 99mTc can be extracted for use. On 9 June they announced that tests at the BC Cancer Agency in Vancouver show they can make 10 Curies-worth of the isotope overnight: enough to treat at least 250 patients and satisfy the needs of a city like Vancouver.
TRIUMF says the upgrade kit and cost of the targets will be price-competitive with the current supply of 99mTc . They hope to get regulatory approval within a year or two; clinical trials have already been done in Edmonton.
Others are also working on the medical isotope problem. There is a similar project for a cyclotron upgrade kit based at the University of Alberta; the Prairie Isotope Production Enterprise is pursuing using electron accelerators that could do the job; Europe is working on a replacement research reactor; and there is an effort to build a new, centralized facility in Wisconsin that could produce enough 99mTc for half of the United States. “If it works, it’ll be pretty cool,” says Meyer of the US effort. “We think we’ll be to market faster.”