For the most part, anyone who wants to see what is going on in someone else’s brain must make a compromise regarding the tools to be used. The electroencephalographer (EEG) is inexpensive and portable, but cannot read a lot beyond the external layers of the brain, while alternative magnetic resonance imaging (IRM) is expensive and the size of a room, but can go further. Now, a research group in Glasgow has created a mechanism that could one day provide the depth of the IRM using the equipment as affordable and portable as an EEG. Technology will rely on something that previously seemed impossible – shedding light through a person’s head.
Obviously, the human head does not leave much light through. For years, brain imaging techniques using light, called optical cerebral imaging, have struggled against this obstacle to become widely used in research and clinical practice. Optical cerebral imaging mainly uses close infrared light, to which the human fabric is relatively transparent. But the human heads are so good at blocking even these wavelengths that the Glasgow research group found that only a billionth of a billionth of all the near infrared photons cross an entire adult human head from one side to the other. Statistics like these have prompted many things on the ground to conclude that the transport of light through the deep brain was impossible, until the group of Daniele Faccio at the University of Glasgow recently done it.
“Sometimes we went through phases of thought, okay, maybe it’s just impossible because we just haven’t seen a signal for so many years.” —Jack Radford, University of Glasgow
“There are many optical techniques for monitoring brain activity that have laser detectors that may be placed three centimeters apart, perhaps five centimeters apart. But no one had really tried to cross his head,” said Jack Radford, the main author of the study describing the work in Neurophotonicexplain. The team started with a thick and diffused material slab, and found that light could pass through the width of a human head of the material to reach a photodetector. Then they designed an experience to test the limits of the transmission of close infrared light through the head of a volunteer.
The group measured the moments when millions of photons took to travel from a laser of 1.2 watt emitting a wavelength of 800 nanometers in one side of the head towards a detector on the other side. Each time, he represented possible paths that individual photons could take the head of the subject. They also simulated the travel paths of the photons and built distributions of experimental and simulated times. Because the distributions were so similar, they were able to conclude that they not only detect random photons passing through the room. But it was not only a gentle navigation.
It took many iterations of experimental configurations to permanently find that in a billion photons passing through the head.Extreme light group / Glasgow University
“What is not in the newspaper are the five years of experience that did not really work,” said Radford. A major improvement made by the team to experience was to reduce background noise. Because so few photons pass throughout, it is more likely that the photons rebound in the room to hit the detector than for the photons that really crossed the head. They made adjustments like the drape of black fabric on the subject’s head, performing the whole experience in a black box, putting the subject in a sleeping bag arrangement and going up another black cover on all this, before seeing good results. They also spent time trying different lasers, adjusting the size and wavelength of the beam, and inventing new configurations to improve their signal, some of which involved bicycle helmets and disorders.
“Sometimes we went through phases of thought, okay, maybe it’s just impossible because we just haven’t seen a signal for so many years,” said Radford. “But there was always a kind of inclination that we could do something. This is what kept the momentum in the research project.”
Now, the possibility of measuring the photons that have crossed the deep brain are opening a multitude of new possibilities for cheaper, more accessible and deeper penetrating imaging technology, he suggests.
Towards a deeper optical cerebral imaging
“Applications to date are roughly focused on the surface of the brain – this is what current technology can do,” explains Roarke Horstmeyer, professor in the Department of Biomedical Engineering at Duke University, which was not involved in the search for Glasgow. Research “helps to assess and establish whether this optical technology can start or not to reach these deeper regions.”
Radford explores the means to apply to deep penetrating optical optical imaging in clinical and medical environments, in particular to help quantify brain health. For a set of large conditions that are difficult to quantify such as cognitive decline, neurodegenerative diseases, brain fog and concussions, hospitals generally use questionnaires to determine brain function. But “[there are] No real biomarker for brain health and how it evolves over time, ”explains Radford. Optical imaging tools that can reach the deeper brain could provide a more widely accessible and deterministic method to identify these conditions that are difficult to quantify.
Another application that Rarsford is interested is the rapid diagnosis of strokes. Identifying and processing stars correctly before serious neurological lesions is currently occurring on the ability to obtain a computed tomography and MRI in a few hours to determine the exact cause of the stroke. But these analyzes are expensive, which makes this treatment less accessible. The prescription for the processing of stroke without knowing the cause could, however, cause deadly consequences. A brain brain scan using optical brain imaging methods could quickly and lower the cause of stroke, leading to rapid diagnosis and treatment.
Radford is delighted that the difficult compromise of costly and deeper penetrating imaging equipment compared to cheaper but less deep sensors begins to decompose. Doctors and researchers “do not realize that they could use [brain imaging] because they have always thought that the use of an MRI is out of the question … now that [MRI] Is not the question, it is exciting to speak to clinicians and … explore different potential uses to help them in their diagnoses and their treatment, “he said.
However, there are obstacles that technology still has to overcome to succeed in a clinical framework. On the one hand, the study itself did not imagine any of the deep brain; He has just sent photons. “Technology still has a long way to go, it is still in its infancy,” explains Horstmeyer. Another obstacle will be the variations in the anatomy of the heads of the subjects – on the eight volunteers on which the experience carried out tests on, the Radford group was unable to detect a signal for a light skin participant and no hair.
“When you cross your head, you are at light levels so low that the color of your skin or your thickness of your skull or the hairstyle you have can make this difference of being able to detect it or not,” explains Horstmeyer.
Radford thinks that there could be a way to overcome the variations in human anatomy by modifying the power and size of the laser beam, but he admits that these changes could cause spatial resolution problems. It is “always an unresolved problem, in my mind,” he says.
Despite these challenges, Radford stresses that the goal of the study was simply to show that it is physically possible to transport photons throughout the human head. “The point of measurement is to show that what was considered impossible, we have revealed possible. And hopefully … It could inspire the next generation of these devices,” he said.
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