Nijmegen’s super scanner will soon take the sharpest brain photos: what can science do with them?

The Donders Institute will build the world’s most powerful MRI scanner in Nijmegen, together with six other Dutch partners. The super scanner makes brain images of unprecedented precision possible, but can test subjects handle such a strong magnetic field?

It was great news that even made the news at 8 p.m.: Nijmegen is getting the most powerful MRI scanner in the world. Grant provider NWO is making 19 million available for this, of the “National Roadmap” grant program. This jar is for large and expensive research equipment, including space telescope parts, for example. ‘This scanner places Nijmegen in the domain of neuroimaging soon to be at the center of the world”, proudly declares David Norris (Donders Institute), director of research. “This will make Nijmegen even more attractive to top international scientists.”

“We will soon be able to identify very small brain nuclei as well”

The device will have a force of no less than 14 Tesla – unheard of for human research. Tesla is the physical unit of magnet strength (it has nothing to do with car brand). By way of comparison: the earth’s magnetic field, to which a compass needle reacts, is less than one ten thousandth of a tesla.

Nijmegen’s new scanner will be nearly five times more powerful than modern 3 Tesla MRIs currently installed in many hospitals, and more powerful than any existing scanner in the world used for brain research. The current record holders are Paris and Baltimore, which currently have two 11.7 Tesla MRIs.

Impressive performance

What exactly can we expect from this scanner, which will be turned on for the first time in three years, if all goes well? Norris doesn’t have to think long about that, he says in his office in the Trigon building. MRI physics teacher shows one after another artist impression on the screen, as well as all the impressive performances expected by the DYNAMIC consortium (see box). “We will soon be able to make much better scans capable of distinguishing 0.3 millimeter detail. Current scanners in Nijmegen can barely reach 0.8 millimetres,” he explains. “We will soon be able to identify very small brain nuclei as well.”

It will also be possible to distinguish the different layers of gray matter (the neurons of the outer layer of the brain), specifies the professor, and how information is exchanged within them. Previously, laboratory animals were mainly used for this purpose. “Distinguishing these layers is also possible with today’s powerful 7 Tesla scanners, but with less precision.” Also, the sweep time required is much shorter with 14 Tesla. This makes possible studies that would currently take too long for the test subjects.

But there are also completely new research possibilities, such as measuring the amount of neurotransmitters, the messenger substances in our brain. Norris: “We will soon be able to determine some of them with eighteen times more detail than with 7 Tesla.” This offers opportunities to better understand what exactly is wrong with diseases in which these substances are implicated, such as depression and Parkinson’s disease.

All of this may sound promising, but such magnetic force brings with it all sorts of practical challenges. Today’s super scanners of 10 Tesla or more have all sorts of problems, despite sometimes tinkering for ten years. Very little real research has been done on human subjects.

For example, researchers in Baltimore have been working for years to fix their 11.7 Tesla super scanner after it accidentally got hot during early testing. MRI scanners are cooled with liquid helium to a fraction above absolute zero (273 degrees below zero), because only then do the wires have superconducting properties. This is necessary to create the magnetic field. Paris’ equally powerful scanner has been under construction for a decade and only has test images of it so far inside a pumpkin book.

Maximum limit raised

Do you really want an even more powerful MRI machine, if today’s best scanners already have so many problems? It’s true, Norris said. The Nijmegen scanner will be technically very different from current devices. “With the superconducting material that we traditionally use, we can theoretically go up to 12 Tesla. The flow high field scanners (with a high magnetic field strength, editor’s note) are close to that, which is why they have so many technical problems.

“I predict that the first person who comes in will come out vomiting”

In the Nijmegen variant, the theoretical maximum limit is much further, at 28 Tesla, and the scanner is not pushed to the limit. Materials also need less extreme cooling. This is why no helium (sometimes difficult to obtain) is necessary, but the cooling is done using a vacuum. An added benefit is that the scanner will be much more compact than current super scanners, with a wide opening for test subjects – nice for those who are a bit claustrophobic.

fairground attraction

There are also concerns about what such a scanner does to test subjects. “I predict that the first person who enters will come out vomiting,” says John van Opstal, for example, in a firm tone, in his office in the Huygens building. That is to say, explains the professor of biophysics (also Donders Institute), because strong magnetic fields stimulate the vestibular system, in the same way as a fairground attraction. “You feel like you’re spinning all the time.” Van Opstal has been conducting research for decades on, among other things, the functioning of the organ of balance located in our inner ear.

At relatively low field strengths such as 3 Tesla the stimulating effect is still weak, but at 7 it is already quite noticeable. Van Opstal includes a video in which a close view of the eye can be seen of a subject in a 7 Tesla MRI. The eye comes and goes all the time. Such a so-called nystagmus is an automatic eye reflex that occurs when you turn around.

float

Van Opstal: “With 14 Teslas it will be even worse. The effects may even be harmful – no one knows. For example, auditory stones can be released in the otoliths (part of the balance organ), he says. This causes a form of vertigo that can last for weeks. The question is also whether so-called paramagnetic effects can already occur – a phenomenon that makes things levitate. This happens at extreme magnetic powers, such as that of the HFML-FELIX 37.5 Tesla scanner (not suitable for humans), which the Nijmegen physicists used in 1997. float a frog. A test subject in the new scanner won’t float, but small things in the body might, Van Opstal speculates.

“We take security very seriously”

Norris points out that he and his colleagues really don’t happen overnight. “We take security very seriously,” he says. “We know from other powerful scanners that short-term effects can occur, including dizziness.” We will only investigate test subjects after all of these aspects have been carefully considered. In addition, there will be an independent security committee that will test everything. And we are working closely with Paris and other labs to learn from their experiences with super scanners. He also doesn’t expect floating effects. And if it’s really necessary, he says, the magnet’s strength can be reduced. The investment of millions will therefore not be wasted money anyway, he means.

Dizziness

Radiology professor Thijs van Osch (University Medical Center Leiden) does not expect insurmountable problems either. Van Osch, who is himself involved in the DYNAMIC consortium, has repeatedly studied the risks of scanning at high field strengths. Like that he analyzed in 2013 the experiences of over a hundred test subjects with the powerful Leiden 7-Tesla scanner. ‘They weren’t too bad. A third of the people suffered from vertigo, but especially when they entered the scanner,” he explains by telephone. “You can counter that a bit if you move people very slowly.”

Additionally, an equally large group found the loud scanner sound uncomfortable (despite hearing protection). Only 3% found the scanning session really boring overall. Van Osch: “In practice, most people get used to it after about ten minutes. So I don’t expect 14 Tesla to suddenly be problematic.

We will probably not know exactly how the new acquisition of the Donders Institute will happen in ten years. Then the scanner will be fully tested and it will have to run at full speed in the brain and medical research is the plan. Norris, laughing: “That’ll keep me busy until I retire.”