Posted on 06/16/2025 6:15:37 AM PDT by Red Badger
In a nutshell
* Scientists successfully transmitted light through an entire adult human head for the first time, overcoming extreme attenuation of 10^18 to detect individual photons
* The technique can potentially monitor deep brain regions like the midbrain and cerebellum that are currently unreachable with existing optical brain imaging methods
* While limited to participants with fair skin and no hair, the breakthrough opens doors for future portable brain imaging devices to detect strokes and tumors without expensive MRI machines
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GLASGOW — Doctors may be a step closer to peering deep into your brain to spot strokes or tumors without expensive MRI machines or invasive procedures. That’s because researchers at the University of Glasgow just achieved what many thought impossible: transmitting light completely through an adult human head from one temple to the other.
For decades, brain imaging has been limited to either cheap but basic tools like EEG or expensive machines like fMRI that cost millions. Meanwhile, optical methods, which use light to measure brain activity, can only penetrate about 4 centimeters below the scalp. This leaves vast regions of the brain invisible to doctors.
The Glasgow team fired laser pulses through a volunteer’s head and detected individual photons emerging on the opposite side. Only one photon made it through for every billion billion photons they started with, yet they still managed to capture it. The attenuation was so extreme that it took 30 minutes to collect enough data for analysis.
The technique, described in the journal Neurophotonics, reveals previously unreachable brain regions like the midbrain, areas tucked into brain folds, and deep parts of the cerebellum — all places where strokes, tumors, and other serious conditions often develop undetected until symptoms become severe.
What is attenuation?
Attenuation is how much light gets weakened as it travels through material. Think of it like a flashlight beam getting dimmer as it shines through fog; the thicker the fog, the dimmer the light becomes. In this study, an attenuation of 10^18 means only 1 photon made it through for every 1,000,000,000,000,000,000 photons that started the journey.
Breaking Through the “Impossible” Barrier
For years, scientists believed transmitting light through an adult human head was essentially impossible. Human tissue scatters light so intensely that most experts assumed photons entering one side would never make it to the other side intact.
Previous studies only succeeded with newborns and infants, whose skulls are thinner and more transparent. Some researchers flat-out declared detection of light across an adult head “impossible.”
Lead researcher Jack Radford and his team tested this assumption using computer simulations that track individual photon behavior as they bounce through different tissue types. Their models revealed something surprising: while most photons get scattered and absorbed, some could theoretically make the complete journey by following specific pathways through the brain.
Rough estimates seemed to prove the skeptics right. Just looking at the brain’s white matter — a 10-centimeter-thick layer — scientists calculated that light would be weakened by a factor of 10 to the power of 53. That’s a number so massive it means virtually no light should make it through.
Detecting photons through an entire adult head explores the limits of photon transport in the brain, for access to regions of the brain currently inaccessible with noninvasive optical brain imaging. (Credit: J. Radford et al) Following the Brain’s Natural Light Highways The key breakthrough came from understanding how light travels through brain anatomy. Rather than scattering randomly, photons tend to follow “highways” of cerebrospinal fluid, which is the clear liquid that surrounds and protects the brain.
This fluid has much lower scattering properties than skull bone or brain tissue, essentially creating channels that guide light through the head. Computer simulations showed light preferentially persisting in regions with low absorption and scattering, particularly in cerebrospinal fluid above and below the cortex.
The team used ultrafast laser pulses — delivering more than a trillion bursts of light per second — and directed them into the side of a volunteer’s head. On the opposite side, they set up an ultra-sensitive photon detector designed to catch even the faintest flicker. They optimized the setup to overcome extreme attenuation, using high power spread across a large area and a detector designed to maximize light collection.
Different source positions could direct photons along various routes. Positioning the source high above the ear caused light to travel around the top of the brain, while lower positions guided light underneath the brain tissue.
Researchers say the light followed fluid-filled pathways in the brain, specifically the cerebrospinal fluid that cushions and circulates around the brain. These “light highways” scatter less than bone or tissue, helping guide the photons on their long journey from temple to temple.
Real-World Testing Reveals Key Limitations
The experiment involved a male volunteer with fair skin and no hair, characteristics that proved crucial for success. Over 30 minutes, researchers detected about one photon per second that had successfully traveled through his head.
When they tested seven other volunteers with different characteristics, including those with darker skin tones and thicker hair, they couldn’t detect any meaningful signals above background noise. This limitation represents one of the current challenges with the technique.
Computer analysis revealed successful photons traveled an average path length of over one meter, more than six times the straight-line distance from source to detector. About 17% of their journey went through scalp, 35% through skull, 22% through cerebrospinal fluid, 19% through gray matter, 6% through white matter, and 1% through air cavities.
And because of how they moved, they provided more interaction with brain tissue than traditional reflection-based methods.
Targeting Deep Brain Regions
The researchers created sensitivity maps showing which brain regions their technique could potentially monitor. Unlike conventional brain imaging that creates zones near the skull surface, this transmission approach produced complex, three-dimensional patterns reaching deep into the brain.
By repositioning the light source just 40 millimeters lower on the head, researchers could shift sensitivity almost exclusively to regions under the main brain tissue, areas currently impossible to reach with non-invasive optical methods.
Strategic placement of multiple sources and detectors could create detailed maps of deep brain activity. The technique showed sensitivity to the midbrain, areas within brain folds, and regions of the cerebellum..
The large volumes covered by these sensitivity maps extend far beyond typical “banana-shaped” profiles found in conventional systems, evolving into complex shapes that could potentially reconstruct three-dimensional information about brain activity.
Future Applications and Current Challenges
Eventually, this kind of technology could lead to portable, non-invasive tools for spotting brain injuries or signs of disease in hard-to-reach regions. While the 30-minute data collection time makes this approach impractical for real-time brain monitoring, researchers believe the technique could work for applications that don’t require split-second timing. Doctors wouldn’t need MRI machines or surgeries to see what’s going on inside your head. Just a burst of light and a sensor might be enough.
As one of the researchers put it, these results could extend light-based brain imaging into parts of the brain that, until now, have remained completely off-limits. Potential uses include detecting brain bleeding, monitoring tumor growth, or diagnosing traumatic brain injuries.
The specificity to one participant type — fair skin and no hair — currently limits broad applicability. However, intermediate distances between the 4-centimeter limit of current methods and the extreme 15.5-centimeter diameter tested here could provide exponentially better signals while still reaching deeper than conventional techniques.
While practical applications may require further development, the foundation has been set for potentially revolutionary advances in how we study and treat the human brain.
Of course his head shrunk.
Sure, shoot a laser at my brain. Please.🙄
Was Scotty involved ? LOL
I’m not sure this is groundbreaking science in England.
I can do the same thing shining a flashlight into the ear of any given Labour Party member. Comes right out the other ear.
You can do that to some people with nothing more than a flashlight.......taterhead biden comes to mind
C’mon man. They’ve done that to Biden for years...with a flashlight.
Was it you that posted the article about the “high” powered hand held laser a couple of days ago?
Does the patient survive?
I get this result by shining a light in one ear of a democrat.
In unrelated news, it was found recently that the speed of lies in the ears, through the heads, and out of the mouths of all surveyed democrat politicians and newscasters exceeded that of the speed of light in a vacuum.
Yep!...................😏
Dems brains have lotsa hot air...
“For years, scientists believed transmitting light through an adult human head was essentially impossible. Human tissue scatters light so intensely that most experts assumed photons entering one side would never make it to the other side intact. “
Besides the fact all the sources available for years would fry you with heat.
They turned Joe sideways and directed the beam into one ear...
In one ear and out the other....
Seems like there’s an AOC joke here somewhere...
Let’s test this on Congress.
All they had to do was put a flashlight up to a liberal’s left ear. The light comes out the right ear.
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