Liquid-nitrogen-cooled sensors could improve brain research

Swedish researchers have used liquid-nitrogen-cooled sensors to improve the cost and performance of magnetoencephalography (MEG) systems used to study the brain.

MEG is used as a diagnostic system in highly specialised hospitals, and applications include pre-operative planning for brain surgery and the diagnosis of epilepsy and dementia.

A single MEG system costs roughly €3m (£2.4m) to buy and €200,000 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.

Researchers at Chalmers University of Technology and Gothenburg University are now working on technology that can make MEG far more accessible.

The research group aims to develop a MEG system that is simple and cheap enough to be available at every hospital, while providing totally new possibilities for fundamental investigations in brain research.

According to a statement, a new class of sensors is at the heart of the system. Unlike today’s MEG sensors, which require cooling to -269ºC, the new sensors work at -196ºC — a capability that provides a number of advantages.

‘One of them is the reduction of insulation between the sensors and the subject’s head,’ said Dag Winkler, a 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, it is possible to 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, recording from a patch of the brain that is a fraction of that size.

‘Another important advantage with Focal MEG is that the coolant the hardware requires is just liquid nitrogen’, said Winkler. ‘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 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) provides an 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,’ said Justin Schneiderman, assistant professor in biomedical engineering at Gothenburg University 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.’