LEDs may replace magnetism and radiation for neuroimaging
By Ben Coxworth
May 26, 2014
When doctors want to monitor someone's brain activity, they generally use either functional magnetic resonance imaging (fMRI) or positron emission tomography (PET). One subjects the patient to strong magnetic fields, while the other involves radiation exposure. Scientists at Washington University in St. Louis, however, have recently had success using diffuse optical tomography (DOT). Although it may look kind of extreme, it basically just involves shining LEDs into the subject's head.
DOT itself isn't brand new, having already been used to study small regions of the brain. This latest system, however, is able to monitor up to two-thirds of the head at once. This means that it can image multiple regions and networks of the brain simultaneously.
The technology requires patients to wear a cap festooned with dozens of LEDs and light sensors. Light is emitted by the bulbs, through the subject's skull and into their brain. By analyzing how the brain tissue absorbs and scatters the light, it's possible to determine where and when highly oxygenated blood flows in. The increased blood flow is in turn an indicator of neuronal activity.
In lab tests, the new DOT system was shown to perform almost as well as fMRI on the same areas, yet without the accompanying magnetic fields. Although not harmful in all cases, these fields can cause problems in patients with electronic implants such as pacemakers, cochlear implants and deep brain stimulators. Because it doesn't involve harmful radiation, it could also be used as an alternative to PET for performing multiple scans over time.
Despite the looks of the system, it's additionally more portable than fMRI or PET setups, so it can be brought to the patient's location as needed.
One limitation of the technology is the fact that it can only reliably image the brain down to a depth of about one centimeter – it can't be used for deep brain scans. According to the university, however, "That centimeter contains some of the brain’s most important and interesting areas with many higher brain functions, such as memory, language and self-awareness, represented."
A paper on the research was recently published in the journal Nature Photonics.