MEG is used today as a diagnostic system in many highly-specialized hospitals. Applications include pre-operative planning for brain surgery and diagnosis of epilepsy and dementia. A single MEG system costs roughly 3M€ to buy and 200k€ in annual running costs. Because of the high price tag, there is currently not a single MEG system in many countries with high-tech medical care, including Sweden.
A group of researchers at Chalmers University of Technology and the University of Gothenburg are now working on technology that can make MEG far more accessible. The vision is an MEG system that is simple and cheap enough to be available at every hospital, while furthermore providing totally new possibilities for fundamental investigations in brain research.
At the heart of the system is a new class of sensors that, unlike today’s MEG sensors, don’t require cooling to -269 Celsius. Instead, these work at -196 Celsius. This capability provides many advantages:
“One of them is the reduction of insulation between the sensors and the subject’s head,” says Dag Winkler, professor of physics at Chalmers. “The sensors can therefore get much closer to the brain so that one can take a more high-resolution picture of brain activity.”
With today’s technology, you can record activity from a patch of the brain that is roughly the size of a 1€ coin. With “Focal MEG” – MEG with liquid-nitrogen cooled sensors – the precision can be improved such that you’re recording from a patch of the brain that is a fraction of that size.
One example of what that can lead to is diagnosis of autism in children at a younger age – something that would be very meaningful considering how critical it is for these children to get the right help as early as possible.
“Another important advantage with Focal MEG is that the coolant the hardware requires is just liquid nitrogen”, Dag Winkler adds. “Today’s MEG requires liquid helium, which is extremely expensive. Furthermore, one can build the hardware with far more flexibility and less complication when using nitrogen instead of helium.”
The Gothenburg researchers have shown that Focal MEG works for advanced brain investigations. Using two sensors they developed, they have successfully recorded spontaneous brain activity –something that had never been done before with liquid-nitrogen cooled sensors. The ability to record spontaneous brain activity (as opposed to averaged activity from repetitive stimulation) is a solid indication that they can record more complicated brain activity.
“The prevailing assumption among MEG researchers has been that MEG with liquid-nitrogen cooled sensors isn’t feasible,” says Justin Schneiderman, assistant professor in biomedical engineering at the University of Gothenburg and MedTech West. “But now we’ve begun to expose holes in that assumption by demonstrating good sensitivity to two well-known brain waves from well-understood parts of the brain.”
The researchers have furthermore made an unexpected finding. They have recorded an uncharacteristically strong brain wave – the so-called theta rhythm – from the back of the brain. Today’s methods tend to find theta waves only in other parts of the brain.
“This is quite exciting,” says Mikael Elam, professor in clinical neurophysiology at the University of Gothenburg. “It may be an as-yet undetected type of brain signal that can only be found when one measures as close to the head as we do.”
Communication between brain cells generates magnetic fields that can be measured with SQUID sensors. Focal MEG puts the sensors closer to the head, thereby improving signal levels and enhancing focus on brain activity
Illustration: Philip Krantz, Krantz Nanoart
Portrait of Dag Winkler:
Photo: Jan-Olof Yxell
Image to the right:
Chalmers researcher Fredrik Öisjöen serves as a subject, while Justin Schneiderman from the Sahlgrenska Academy adjusts the measurement hardware.
Photo: Henrik Mindedal, MedTech West
Read the scientific article here:
More on brain investigations
Three complementary techniques are the “tools of choice” for neuroscientists:
- MEG, magnetoencephalography: Measurement of the weak magnetic fields generated by electrical activity in the brain.
- EEG, electroencephalography: Measurement of the electrical currents in the brain.
- fMRI, functional magnetic resonance imaging: Provides a 3D picture of local changes in the brain’s blood flow.
fMRI is the technique that provides the best spatial resolution, but has limited time resolution because of the delay between brain activity and changes in blood flow. MEG and EEG can, however, detect events lasting just a few thousandths of a second.
MEG has better spatial resolution than EEG, but requires much more expensive and complicated hardware. MEG is most sensitive to activity in the folds of the brain, while EEG is more sensitive to activity on the ridges of the brain. The two are thus complementary and, perhaps more importantly, mutually compatible.
More information on (Standard) low-Tc MEG
The sensors used in MEG systems are called SQUIDs (Superconducting Quantum Interference Devices). They are some of the most sensitive magnetic field sensors available. The quantum physics phenomenon that is the basis for SQUID function requires cooling to a few hundred minus Celsius.
Today’s MEG systems employ so-called low-Tc SQUIDs, that must be cooled to -269 Celsius. MEG with high-Tc SQUIDs – that suffice with -196 Celsius – is performed today only in research labs. At present, high-Tc SQUIDs are not commercially available because they are difficult to make and have high noise levels. But the Chalmers researchers compensate for the noise with higher signal levels. The SQUIDs reach a sufficiently high signal-to-noise ratio to warrant development of a full Focal MEG system based entirely on liquid-nitrogen cooled sensors.
For more information, please contact:
Dag Winkler, Chalmers University of Technology, firstname.lastname@example.org, +46 31-772 34 74
Mikael Elam, The Sahlgrenska Academy at the University of Gothenburg, email@example.com, +46 31-342 15 84
Justin Schneiderman, The University of Gothenburg and MedTech West, firstname.lastname@example.org, +46 31-342 63 03
More about the research
The group consists of researchers both from Chalmers University of Technology and the University of Gothenburg. The research team includes: Maxim Chukharkin, Mikael Elam, Gerard Figueras, Anders Hedström, Alexei Kalabukhov, Justin Schneiderman, Dag Winkler, Minshu Xie and Fredrik Öisjöen.
The collaboration also includes MedTech West, which plays an important role in the success of this project by facilitating interconnections between the necessary clinical and technical expertise of the group. MedTech West is a western Swedish network for cross-border collaborative research, development, and education in medical technology where academia, healthcare, and industry work closely together. For more information, visit www.medtechwest.se.
The researchers acknowledge financial support from the European Commission Framework Program 7: project MEGMRI, the European Union via Tillväxtverket and Regionala Utvecklingsfonden for MedTech West, the Knut and Alice Wallenberg foundation, and Kristina Stenborgs stiftelse.