CERN Accelerating science

CERN is better known as the birthplace of the World Wide Web than for the role it plays in researching new cancer treatments, but that’s exactly what a new facility at ISOLDE will do.

The dedicated facility being built, called CERN-MEDICIS (Medical Isotopes Collected from ISOLDE), will use radioactive isotopes produced at ISOLDE, CERN’s nuclear physics facility, solely for the purpose of researching non-conventional radioisotopes for medical research.

Radioactive isotopes are already widely used by the medical community, for imaging, diagnostics and radiation therapy. But many of the isotopes currently used are not perfect; they don’t target tumours closely enough, or a different type of radiation might be better suited for the imaging process. MEDICIS hopes to be able to produce isotopes that more accurately meet the needs of medical professionals.

“If you just talk about pure nuclear physics, it could get boring fairly fast,” jokes Karl Johnston, physics coordinator at ISOLDE, CERN’s nuclear physics facility, “but this, MEDICIS, it’s genuinely exciting.”

“The real advantage for MEDICIS is that you can speak to a medical doctor, and ask them what they would like from an isotope, a shorter physical half-life let’s say, so it stays in the subject for less time, and then we can produce them all: isotopes that emit positrons and gamma rays for imaging, isotopes that emit beta electrons or alpha particles that can be used for attacking cancer itself, anything,” he continues.

Currently, ISOLDE already produces two types of isotope for medicine that can’t be produced anywhere else. Terbium-152 is used for imaging and terbium-149 produces alpha radiation, which is used in radiotherapy to kill resistant cancerous cells.

“When we use alpha-emitting isotopes, it is a much more concentrated form of radiation that kills cells only in its immediate surroundings, so the doctors target it into a really specific location. The DNA has no chance to survive. But because it’s specific it means fewer radiation side effects too,” says Thierry Stora, the CERN engineer who leads the CERN MEDICIS project.

A parasitic experiment

“This is why ISOLDE is so fantastic: we’re pushing the boundaries of pure physics research and it has a tangible effect, it can touch elements of society”
 Karl Johnston, physics coordinator at ISOLDE

MEDICIS works by placing a second target behind the ISOLDE one. A beam of protons from CERN’s Proton Synchrotron Booster is fired into the ISOLDE target, where it only loses roughly ten per cent of its intensity, so the particles that pass through can still be used. MEDICIS takes advantage of this left-over beam.

Once the isotopes have been produced in the MEDICIS target by irradiation of the left-over beam, an automated conveyor belt carries them to the MEDICIS facility, where the radioisotopes of interest will be extracted through mass separation and implanted in a metallic foil. Gold foils are used because the metal is very unreactive, and any coating can be dissolved easily once the isotope reaches its destination. It is then shipped, in weekly batches, to medical research facilities, such as PSI, CHUV or HUG, to study and test.

Once at a hospital or research centre, technicians will dissolve the isotope and attach it to a sugar or something similar. This makes the isotope injectable, and the sugar means it can adhere to the tumour or organ that needs imaging or treating.

Although ISOLDE already produces isotopes for medical research, since so many experiments are vying for beam time it’s hard to give these isotopes enough resources, and so they are only produced for a few days per year.

“One of the best and most positive things about MEDICIS is that it’s a parasitic experiment. It uses the same proton beam that goes through the ISOLDE target, but then the MEDICIS target is irradiated behind the ISOLDE one. Whenever ISOLDE is running you can get radioisotopes. You don’t need extra beam time,” explains Yisel Martinez, one of the first PhD students to work on the MEDICIS facility.

New facility, new challenge

While the benefits of a dedicated facility to steadily produce these medical isotopes is clear, the researchers at ISOLDE have struggled at times to explain why it’s so important.

“We have had to be evangelists for this. When doctors hear about the process – a short proposal to CERN, more paperwork, the length of time before it’s possible to get the isotope ready for them to use in their medicine – often it’s really hard to get them interested,” Karl shrugs. “But despite these worries, we have lots of people signed up who can see the benefits, and many doctors are convinced. Although even then, sometimes you don’t get an isotope to the research facility fast enough, and it just decays away. It can be heartbreaking.”

The infrastructure too has faced its own share of challenges. At one point, after six weeks of paperwork and many days of transport, the mass separator magnet from KU Leuven, a university in Belgium, was turned away at the Swiss border, around fifty metres from the MEDICIS building, and sent back to Belgium.

But now the facility is about to start running. And, as of next year, a huge range of innovative isotopes, capable of changing medicine, will be produced weekly.

“This is why ISOLDE is so fantastic: we’re pushing the boundaries of pure physics research and it has a tangible effect, it can touch elements of society,” concludes Karl.

This week, ISOLDE, CERN’s nuclear facility, is celebrating 50 years of physics with a series of articles and a short documentary series that takes a closer look at the facility and the people that work there. See the rest of the series here.

For more information on how CERN has contributed to medical technologies, see the Knowledge Transfer website.