Designing a new brain scanner (MEG). Credit: Wellcome Trust. YouTube
Whole head magnetoencephalography (MEG) systems have been in use since the 1990’s. These bulky and expensive scanners measure the tiny changes in the magnetic fields caused by activity in clusters of cells in different brain regions.
Electric currents in brain cells are caused by the movement of charged ions across their membranes. This movement of positive and negative charges can be measured by the sensitive magnetic sensors of the MEG machine.
As Dr. Matthew Brookes, Associate Professor in the department of Physics at the University of Nottingham, UK, explains: “These sensors can detect changes in magnetic fields that are a few ten’s of femtoTesla.”
MEG provides much more spatially detailed and therefore deeper insight into brain function than electroencephalography (EEG), which uses electrodes to measure electrical activity and is hindered by interference from the electrical activity of muscle movement.
However, unlike the cheaper and wearable electrode caps of EEG machines, MEG machines have a cumbersome one-size-fits-all static machine approach to imaging the brain.
As Matthew describes: “The patient sits upright in a chair with their head inside the scanner”
Akin to images of people in hair salons with their heads in large hair-dryers.
“Patients must sit very still for long periods of time to enable accurate and repeatable measurements of brain activity. This makes it extremely challenging to use MEG to measure brain activity in children or in patients with movement disorders, like Parkinson’s patients, for example.”
New MEG system is a better fit
Matthew was part of the team that has developed a new ‘wearable’ MEG system incorporated into a helmet. Thus, making it possible for children and those previously unsuitable for MEG to have their brain imaged.
“We’ve developed a system that can achieve the same sensitivity in measurements from a 1 year-old up to an 85 year-old.”
“Because the new system is wearable, it enables us to undertake new kinds of experiments, with patients doing things that they can’t do in traditional brain scanners. For example, like bouncing a ping pong ball on a bat. Even this simple example would allow a new way for neuroscientists to investigate coordination between the brains visual and movement centres. Also, the spatial resolution is better as the sensors are closer to the head.”
The new system that the team have developed is also cheaper than current scanners, because it doesn’t require cooling of superconducting sensors to -269 degrees centigrade, like the traditional machines which can cost upwards of £2million.
A game changer in the research field
One of the major challenges with a wearable MEG system is that the Earth’s magnetic field, around the subject’s head, must be removed to stop it interfering with sensitive measurements. The group achieved this by creating a magnetic field dead-space in the middle of the room, where the patient sits. This was achieved by developing Magnetic field coils that surrounded the room and which cancel out the earth’s magnetic field.
The scientists say, the only limitation to the size of this dead-space is the size of the room they can implement these coils in.
This means it will be possible for more than one person to be imaged by MEG at the same time, making it possible to do more ‘real-life’ research and understand more about brain activity in different environments, such as when people are interacting.
The Future of Brain Research and Treatment
This new wearable technology is a big leap forward in brain imaging.
Professor Gareth Barnes, who leads the project at the Wellcome Trust Centre for Human Neuroimaging at UCL, said: “This has the potential to revolutionise the brain imaging field, and transform the scientific and clinical questions that can be addressed with human brain imaging.”
It will enable: real-time measurements of Parkinson’s patients; observation of seizure activity in epileptic patients; functional investigations of brain development and degeneration.
And Matthew envisages a time in the not-too-distant future when researchers can incorporate their MEG helmet with a virtual reality system to immerse patients in controlled virtual environments that could help understand their responses to stressful situations, in the treatment of post-traumatic stress disorder, or phobia therapy, for example.
Boto, E., Holmes, N., Leggett, J., Roberts, G., Shah, V., Meyer, S. S., . . . Brookes, M. J. (2018). Moving magnetoencephalography towards real-world applications with a wearable system. Nature. doi:10.1038/nature26147