A new optical approach to brain scanning compares favorably with neuroimaging techniques such as PET and MRI, according to a new study. Using tiny LED lights to track what is happening in the brain, the technology is radiation-free and does not require bulky magnets.
In the journal Nature Photonics, scientists from the School of Medicine at Washington University in St. Louis (WUSTL), MO, report how they benchmarked the new technology – called diffuse optical tomography or DOT – against functional MRI (fMRI).
Scientists have been developing DOT for more than 10 years, but its use has mostly been limited to research, as it has only been able to scan small regions of the brain at a time. But the authors of this new study believe DOT now shows potential as a surrogate for fMRI.
The new DOT system covers two-thirds of the skull and for the first time can scan brain activity in several regions and networks, including those involved in language and self-reflection. Senior author Joseph Culver, associate professor of radiology, explains:
“With the improved image quality of the new DOT system, we are getting much closer to the accuracy of fMRI. We’ve achieved a level of detail that, going forward, could make optical neuroimaging much more useful in research and the clinic.”
The team says DOT is ideal for children as patients can move freely while they are being scanned. It is also ideal for patients with pacemakers, cochlear implants deep brain stimulators (used to treat Parkinson’s diseases), and other implanted devices. MRI uses magnetic fields, which can disrupt such devices or make them unsafe. With DOT, there is no such danger.
Another significant advantage is that DOT can be designed to be portable, allowing the scanner to be brought to the patient’s bedside or into the operating room.
The full unit takes up a space a little bit bigger than an old-fashioned phone booth inside which the patient wears a cap covered in light sources and sensors connected to cables. However, the researchers have also made versions mounted on trolleys and continue working on new ways to make the technology even more portable.
DOT works by tracking rushes of oxygenated blood to feed active areas of the brain – rather like when our cheeks go red when we blush. Light transmitted through the head changes color as it passes through brain tissue with different amounts of blood rush, and DOT picks up the dynamic changes in the colors.
Another scanning method that is commonly used for mapping brain activity is positron emission tomography or PET, which uses radiation. But the number of times patients can undergo PET scans is limited because of the risks posed by radiation exposure.
DOT does not use radiation, so multiple scans over time could be used to monitor patients with brain injury, autism or progressive brain diseases such as Parkinson’s.
In one test, the researchers took DOT and fMRI scans of the same subjects and looked for Broca’s area, a key area of the frontal lobe used in language and speech. There was an approximate 75% overlap between the brain region identified by DOT and that identified by fMRI.
In another test they used DOT and fMRI to detect brain networks that are active during rest or “daydreaming.” These areas are attracting increasing research interest and have been linked to autism, Alzheimer’s disease and schizophrenia. DOT and fMRI picked out the same cluster of three regions in both hemispheres, note the researchers.
Although DOT cannot reveal what is happening deep inside the brain, it is reliable up to around a depth of one centimeter, say the authors. But within that one centimeter lie some of the most important and interesting parts of the brain, including regions that deal with memory, language, and self-awareness.
Funds from the National Institutes of Health, the McDonnell Centre for Systems Neuroscience, and other sources helped finance the study.
Prof. Culver and WUSTL have also declared a financial stake in a company to which the university has licensed related optical imaging technology.
In February 2014, Medical News Today reported promising test results of a new radiation-free imaging method for diagnosing cancer. The researchers said they hope the new technique will solve the conundrum of the need to scan tumors at different stages without raising risk of secondary tumors developing from increased radiation exposure.