Seismic technology to probe the Earth adapted to probe the brain

Technology used to determine the structure of the Earth’s interior using seismic waves has been adapted into a prototype brain scanner that could give results in real time. It could also be cheaper and simpler to use than technologies like MRI or CT scans.

For decades, geologists have used sound waves travelling through the Earth, either from earthquakes or artificial sources, to search for oil, image fault lines and attempt to predict earthquakes. Reading reflections and refraction of the waves as they pass through different kinds of rocks and deposits can help geologists essentially do an ultrasound to build up a picture of the Earth. 

But in recent years seismology has been supercharged by a computational technique called full waveform inversion (FWI), which uses complex computer algorithms to scavenge ever more information from seismic data, and make much more detailed and accurate 3D maps of the Earth’s crust.

If it can probe the Earth, why not the brain? 

Now scientists at Imperial College London have adapted the same technology into a prototype head-mounted scanner that produced imaging information they say could be used in the future to produce high-resolution 3D images of the brain. 

The wavefield is shown as it propagates across the head. (Dr Lluís Guasch / Imperial College London / University College London / Nature Digital Medicine)

The device uses a helmet fitted with an array of acoustic transducers that act as both sound transmitters and receivers. The system uses low frequency sound waves that are able to penetrate the skull and pass through the brain without harming brain tissue. The sound waves are altered as they pass through different brain structures, then the signals are read and run through the FWI algorithm. In simulations the team got results that make them confident they can produce high-resolution 3D images that may be as good, if not better, than more traditional approaches. 

Such a device, because of its simplicity and presumably lower cost, could make brain imaging much more widely available. 

How the prototype helmet could image the brain (Dr Lluís Guasch / Imperial College London / University College London / Nature Digital Medicine)

If developed into a small, portable version, it could have a powerful impact on the diagnosis of brain injury. For example, doctors in emergency rooms or paramedics would be able to do instant brain scans of accident victims with head injuries, or stroke victims. 

Current brain scanning technology is very expensive so its use is effectively rationed, with long wait times for non-emergency appointments. It’s also cumbersome, not very well suited to some emergency situations, and can’t be used on some patients. MRI, for example, can’t be used on patients with metallic medical implants or victims of accidents who might have metallic foreign bodies in them. They’re also huge, loud and confining, which can be a big issue for some patients. 

Making a real difference in people’s lives

One personal example of someone who has had difficulty getting brain scans is a young man and close friend Jacob Hartley, who suffered a stroke at birth. Now aged 17, he is brilliant in some areas, but developmentally challenged in many others. 

He gave me a personal tour of all the World War II tanks at the Canadian War Museum in Ottawa, describing the cannon calibre, engine type and the battle each one fought in. We have great conversations about aviation, including Russian technology. He can speak endlessly about reptiles, yet he can’t tie his shoes, has no short-term memory and often darts outside in frigid weather in the winter without socks or a coat. The damage to his brain produces autistic behaviours that have made it difficult for him in school and social situations. 

Jacob has had three MRI scans in his life, which have shown extensive brain damage, which affects his executive function and decision making. But getting those scans have been difficult experiences both for him and his mother. 

MRI Scan of Jacob Hartley’s brain. Dark areas at top left and right are from childhood stroke. (Jacob Hartley)

The most recent, taken last August, required a wait time of 2½ months with another month after the scan waiting for an appointment with a neurologist to discuss the results. During the scans, Jacob’s head had to be held down, which is a traumatic experience for him because he will not allow himself to be touched by anyone other than his mother, and more recently, by me. 

If all he needed to do was put on a helmet by himself, and get instant results, the effort would be easier for everyone involved.

Portable brain scanner opens new research possibilities

MRI scanners have had a profound effect on brain research but they have their limitations. A low cost, portable device that allows freedom of movement, that could be used in a variety of environments would provide researchers with a flexible tool that could examine healthy brains as well. 

What happens when a musician plays an instrument, an elite athlete works out, or an ordinary person just walks down the street daydreaming? Knowing how healthy brains work is an important part of understanding those that are damaged. Such a device would provide a new window into the incredible activities taking place in the most complex computer in the known universe… the human brain.

And who would have thought the technology would come from the study of earthquakes?

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