A man walking around a room wearing a helmet that records his brain function would have seemed like science fiction five years ago. Now researchers have designed a lightweight helmet with tiny LEGO-size sensors that scan the brain while a person moves.
The helmet is the first of its kind to accurately record magnetic fields generated by brain activity while people are in motion, reports a new research paper published in NeuroImage. This advance could make it easier to conduct brain scans in young children and individuals with neurological disorders who can’t always remain still in conventional scanners.
Researchers can use the wearable brain scanner, which can be adapted to different head sizes and shapes, to learn more about brain development and what happens in the brains of children and adults who develop neurological conditions such as autism, epilepsy, stroke, concussion, and Parkinson’s disease.
“Unconstrained movement during a scan opens a wealth of possibilities for clinical investigation and allows a fundamentally new range of neuroscientific experiments,” said Niall Holmes, Ph.D., a Mansfield Research Fellow in the School of Physics and Astronomy at the University of Nottingham, who led the research.
How magnetic fields are recorded
When your brain cells (neurons) interact, they generate a small electric current. This electric current produces a magnetic field that can be detected, recorded, and analyzed by sensitive magnetic sensors using a technique called magnetoencephalography (MEG). These sensors must be highly sensitive to detect the low signals that magnetic fields produce.
MEG technology can record both normal and abnormal brain signals every millisecond. The neuronal sources of these magnetic fields are overlaid onto an anatomical image of the brain, allowing clinicians to visualize where and when specific brain activities originate.
MEG systems have evolved to where you can sit and place your head inside them, but they’re bulky and rigid, like an old-fashioned hair dryer where you must keep your head still for a while. In addition, conventional MEG systems have sensors that require cooling at or below freezing temperatures so they can’t be placed directly on your scalp.
Researchers at the University of Nottingham used a new generation of magnetic field sensors called optically pumped magnetometers (OPMs) that operate at room temperature and can be placed close to the head, enhancing data quality. Also, the sensors that are placed in the helmet are flexible, allowing children and adults to move during scanning.
But there is a drawback—OPMs must operate without background “noise” (magnetic fields) that can interfere with the quality of the recording. The researchers had to design a magnetic shielding system that would cancel out or compensate for these magnetic fields.
Designing a matrix coil system
The Nottingham research team constructed a system of electromagnetic coils to shield against the background noise and positioned them on two panels around the participant. Prior research published in Nature shows that eight large coils cancelled the background magnetic fields, but at a fixed position that only allowed small head movements.
Holmes and his team designed a new matrix coil system that features 48 smaller coils on two panels positioned around the participant. The coils can be individually controlled and continually recalibrate to compensate for the magnetic field changes experienced by the moving sensors, ensuring high-quality MEG data are recorded.
