A BRAIN scanner that’s small enough to be worn as a cap will allow patients to move around while wearing it. The cap, which scans just the top two centimetres of the brain, could soon be helping stroke patients in their recovery or telling astronauts whether they’re too tired to fly the shuttle.
The cap makes use of an emerging imaging technique called diffuse optical tomography. The idea behind it is to shine near-infrared light through the skull and into the brain. Because the infrared is quickly scattered in the first couple of centimetres of the brain, you might think that the only image you’d “see” would be hopelessly scrambled. “It’s a messy, noisy signal,” says Jeffrey Sutton, director of the National Space Biomedical Research Institute in Houston. But new software techniques are allowing scientists to turn the signal into useful images.
In one version, the cap is fitted with 32 bundles of fibre-optic cables that shine infrared laser light into a palm-sized patch of the brain (see Graphic). The low-powered light scatters around the outer layer of the brain and is picked up by 32 detectors on the other side.
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The degree of absorption and reflection of the light depends on tissue density, blood flow and oxygenation. This lets the software work out which parts of the cortex—the outermost part of the brain—are active, and highlight any bleeding or tumours.
Sutton’s lab plans to send it into orbit to study what happens to astronauts’ brain fluids in microgravity. “In space, there may be slow, subtle changes that happen over a long time,” Sutton says. And optical imagers are the only technology light enough to take into space to study those changes.
The team is now working with NASA flight surgeons to see how brains behave while volunteers perform computer simulations of docking the shuttle with the space station. This will give them a control to compare with tests of astronauts in orbit.
But optical imaging will have more Earth-bound applications too. Sutton says a rush of blood to the frontal cortex reveals that someone is concentrating too hard on trying to finish a task, which indicates that they’re tired or stressed. The cap could help alert pilots or doctors to fatigue if they’ve been on the go for too long.
Other labs, such as a group led by David Delpy at University College London, are developing similar devices to map premature babies’ brains and measure whether infants are getting enough oxygen. Others are using the cap to study what goes on in the brains of people who are trying to walk again after a stroke, something that’s impossible with a bulky MRI scanner.