Optical Scanner Shines New Light on Brain

A new generation of optical neuroimaging touts effectiveness comparable to MRI and PET technologies, but has the ability to see and study areas of the brain that the others cannot.

Diffuse optical tomography (DOT) is a new brain scanning technology developed by a team at the Washington University School of Medicine. It tracks a person’s brain activity using dozens of tiny LEDs on their head.

Unlike MRI and PET methods, DOT avoids radiation exposure, allowing for multiple scans to be performed over time to monitor patients’ progress during treatment of brain injuries, developmental disorders and neurodegenerative disorders.

A research participant wears the DOT device, used to image the brain. Courtesy of Tim Parker, Washington University School of Medicine.

The method has been in the works for more than a decade, the researchers said, but until recently it was limited to small regions of the brain. Now, DOT can cover two-thirds of the head, imaging brain processes in multiple regions and networks, including those involved with language processing and daydreaming.

The technique works by detecting light transmitted through the head and capturing dynamic color changes of the brain tissue.

“When the neuronal activity of a region in the brain increases, highly oxygenated blood flows to the parts of the brain doing more work, and we can detect that,” said Dr. Joseph Culver, lead researcher and an associate professor of radiology at the university. He compared it to being able to spot “the rush of blood to someone’s cheeks when they blush.”

DOT technology does not penetrate very deeply into brain tissue — only about 1 cm. However, the researchers said that centimeter contains some of the brain’s most important areas and higher functions, including memory, language and self-awareness.

In their study, DOT performance was compared to functional MRI (fMRI) scans, which are also used to diagnose and monitor brain disease and therapies by tracking neuronal activity through changes in blood flow.

The same subject was used in both the DOT and fMRI assessments of the brain’s Broca area in the frontal lobe where language and speech are produced. This testing showed major similarities between DOT and fMRI data.

Additional testing using both of these methods was conducted to detect brain networks that are active when the subject is resting or daydreaming. “Remarkable similarity” was demonstrated here, too, the researchers said.

“With the new improvements in image quality, DOT is moving significantly closer to the resolution and positional accuracy of fMRI,” said Dr. Adam T. Eggebrecht, a postdoctoral research fellow at the university and lead author of the study. “That means DOT can be used as a stronger surrogate in situations where fMRI cannot be used.”

DOT technology could potentially be used in deep-brain stimulation studies of patients with Parkinson’s disease, according to the researchers, as well as imaging and studying the brain during social interactions or when a patient is under general anesthesia during cardiac or other surgeries.

“We’ve achieved a level of detail that, going forward, could make optical neuroimaging much more useful in research and the clinic,” Culver said.

The work was funded by National Institutes of Health grants, an Autism Speaks postdoctoral translational research fellowship, a Fulbright Science and Technology Ph.D. Award and a McDonnell Centre for Systems Neuroscience grant. The research is published in Nature Photonics (doi: 10.1038/nphoton.2014.107).

For more information, visit www.medschool.wustl.edu.