Realising the potential of magnetoencephalography (MEG) using Optically Pumped Magnetometers (OPMs)

In the UK around 600,000 people are living with epilepsy; over 220,000 people are being treated for schizophrenia; 700,000 people have autistic spectrum disorder (ASD), and every 90 seconds one person is admitted to hospital with a head injury. For many of these individuals, conventional brain scanning (e.g. MRI) will be of limited value. For example, in children with epilepsy, MRI often fails to spot an abnormality, and when it does it is frequently unclear whether that abnormality is driving seizures. In traumatic brain injury (TBI), most injuries (~70%) are classified as "mild" (mTBI - more often called concussion). Of these, around 30% go on to produce debilitating symptoms, yet structural imaging shows no abnormality. Likewise in schizophrenia and ASD, individuals are unlikely to show anomalies in conventional imaging. These examples (and many others) highlight the critical need to develop new forms of imaging which can provide objective diagnosis, prognosis, and treatment planning for a range of neurological and psychiatric disorders.

Magnetoencephalography (MEG) is an imaging technology which measures brain function (i.e. what our brain cells do). Using sensors placed close to the head, MEG measures the small currents that flow through assemblies of neurons as we carry out mental tasks. It can track healthy brain activity, and how such activity breaks down in disease. It has proven capability in epilepsy, and it can classify patients with concussion with >95% accuracy. It can also see how brain activity differs in people with schizophrenia, and autism. However, it has drawbacks: In conventional scanners, the sensing technology is bulky, complicated and extremely expensive; patients have to stay still for long periods; it cannot adapt to people with different head size and is difficult to use in children. Even in adults, both sensitivity (how well it picks up signals from the brain) and spatial resolution (how well we can pinpoint a specific area of the brain) is limited.

We have designed a new type of MEG scanner using sensors that are small and lightweight (like Lego bricks). The sensors can be mounted into lightweight helmets (similar to bike helmets). Because the sensors move with the head, good scans can be generated even if patients move around. Helmets can come in different sizes, so we can adapt the scanner to scan people of any age. This "wearable" system can also measure brain activity with greater spatial resolution and sensitivity. It is much cheaper to buy, and easier to maintain.

This device - called an OPM-MEG scanner - is very new. We have proven its capability with a prototype which has 192 sensors, but this isn't enough to offer the high sensitivity and precision that OPM-MEG allows. Also, the current version has cumbersome electronics which make it hard to use. Here, we seek to buy the equipment to allow construction of a greatly enhanced system, which can be used for cutting-edge medical research

The system will have 384 sensors; it will be more sensitive and have higher spatial resolution than any other MEG scanner in the world. It will have compact electronics which will sit in a small backpack worn by the subject. This will allow us to scan people as they walk. The scanner will be operated as a national facility meaning researchers from across the UK will use it for lots of different research projects. Some example projects include scanning infants with epilepsy, understanding concussion, measuring brain activity in schizophrenia, scanning elderly people who are prone to falling as they walk, and scanning a mother and baby at the same time to understand how infants learn from their parents, and how that goes wrong in disorders like autism. These are just a few examples of projects we will support.

Because OPM-MEG is simple, practical, and lower cost, it is highly suited to clinical practice. This equipment is the first step along a path to using this new technology in hospitals.

OPM-MEG has revolutionised neuroimaging, providing an alternative to SQUID-based MEG systems. The result is a new type of scanner which is motion-robust, adaptable to head shape and size, provides a higher signal-to-noise-ratio and spatial resolution, and is simpler, and hence cheaper to buy and run. OPM-MEG offers significant potential, however, to date, a system which realises this potential has not been built because sensor counts are too low, and electronics too cumbersome.

Here, we seek funding for the equipment needed to build a unique, 384-channel OPM-MEG device. The system will be constructed from 128 triaxial sensors (with 3 orthogonal measurement channels per sensor). This triaxial design offers multiple (proven) advantages including unprecedented sensitivity and resolution, rejection of magnetic interference, uniform coverage of the cortex, elimination of cross-talk, and accurate calibration. The sensors come with newly devised electronics, which is housed in a backpack that the subject wears. This (coupled with advanced magnetic shielding that we have already demonstrated) means, for the first time, it becomes viable to scan people as they stand and walk around.

We will open this system for use as a national centre for electrophysiological imaging. It will therefore be used across the widest possible range of applications in medical research; for example, adaptability to infants will be exploited in epilepsy; the ability to undertake new experimental paradigms will be exploited when measuring patients with concussion; we will scan elderly people prone to falling, whilst they walk; and we will capitalise on new opportunities for hyperscanning and understanding disorders which effect social engagement.

In summary, OPM-MEG represents an opportunity to exploit all the technical advantages of MEG, but with the practicalities of EEG. We believe this could produce the step change required to see MEG deployed in the clinic.