Scientists Shine a near-infrared Laser Through a Human Head

Amazing stuff!

"The first step toward an inexpensive new medical imager was proving that near-infrared photons can fly all the way through your head. It was a comically difficult experiment. ..."

"... Optical brain imaging primarily uses near-infrared light, to which human tissue is relatively transparent. But human heads are so good at blocking even those wavelengths that ... only a billionth of a billionth of all near-infrared photons make it through an entire adult human head from one side to the other. ...

the difficult trade-off of expensive, deeper-penetrating imaging equipment versus cheaper but shallower sensors is starting to break down. ..."

From the abstract:

"Significance

The highly scattering nature of near-infrared light in human tissue makes it challenging to collect photons using source-detector separations larger than several centimeters. The limits of detectability of light transmitted through the head remain unknown. Detecting photons in the extreme case through an entire adult head explores the limits of photon transport in the brain.

Aim

We explore the physical limits of photon transport in the head in the extreme case wherein the source and detector are diametrically opposite.

Approach

Simulations uncover possible migration pathways of photons from source to detector. We compare simulations with time-resolved photon counting experiments that measure pulsed light transmitted through the head.

Results

We observe good agreement between the peak delay time and width of the time-correlated histograms in experiments and simulations. Analysis of the photon migration pathways indicates sensitivity to regions of the brain well beyond accepted limits. Source repositioning can isolate sensitivity to targeted regions of the brain, including under the cerebrum.

Conclusions

We overcome attenuation of ∼1018 and detect photons transmitted through an entire adult human head for a subject with fair skin and no hair. Photons measured in this regime explore regions of the brain currently inaccessible with noninvasive optical brain imaging."

Affordable Optical Brain Imaging Advances - IEEE Spectrum "It’s the first step toward an inexpensive new medical imager"

Photon transport through the entire adult human head (open access)

Fig. 2

Experimental results.

(a) The experimental configuration used in laboratory experiments—an ultrafast pulsed laser (1.2 W power, 800 nm wavelength, 140 fs pulse duration, 80 MHz repetition rate) is expanded to a uniformly distributed 1 in. diameter circle and projected against the side of the head. Diametrically opposite the source, a PMT is synchronized to the laser trigger such that a histogram of photon ToF can be measured using TCSPC.

(b) The normalized simulated ToF (black dashed) and the mean of 15 experimental trials (2 min exposure) on day 1 (blue) and day 2 (red). The uncertainty bands indicate the standard error of the mean at each time stamp. The IRF (black) with the peak centered at time = 0 ns is shown for comparison. The start time of all time traces are aligned to the peak of the IRF.

(c) The mean of the background-subtracted counts (black) of day 1 data in each timebin for 15 2-min exposures. The filtered mean counts for each timebin using a Savitzky–Golay filter (window = 251, order = 3). The normalized IRF is shown in red for comparison.

The first brain reference charts from aggregating 120,000 brain scans

Amazing stuff!

Unfortunately, phony concerns e.g. skin color ideology or stereotyping, are already intruding to make use of this unique resource. Always these out of proportion worry warts!

"Scientists have created the first reference charts for the human brain, mapping its growth from infancy to 100 years old. ...

The reference charts are visualizations created from aggregating analyses of over 120,000 brain scans to show ranges in brain size, or gray matter volume, for each age. They also track the human brain’s rapid expansion early in life and its gradual shrinking over time. ..."

From the abstract:

"Over the past few decades, neuroimaging has become a ubiquitous tool in basic research and clinical studies of the human brain. However, no reference standards currently exist to quantify individual differences in neuroimaging metrics over time, in contrast to growth charts for anthropometric traits such as height and weight. Here we assemble an interactive open resource to benchmark brain morphology derived from any current or future sample of MRI data (http://www.brainchart.io/). With the goal of basing these reference charts on the largest and most inclusive dataset available, acknowledging limitations due to known biases of MRI studies relative to the diversity of the global population, we aggregated 123,984 MRI scans, across more than 100 primary studies, from 101,457 human participants between 115 days post-conception to 100 years of age. MRI metrics were quantified by centile scores, relative to non-linear trajectories2 of brain structural changes, and rates of change, over the lifespan. Brain charts identified previously unreported neurodevelopmental milestones, showed high stability of individuals across longitudinal assessments, and demonstrated robustness to technical and methodological differences between primary studies. Centile scores showed increased heritability compared with non-centiled MRI phenotypes, and provided a standardized measure of atypical brain structure that revealed patterns of neuroanatomical variation across neurological and psychiatric disorders. In summary, brain charts are an essential step towards robust quantification of individual variation benchmarked to normative trajectories in multiple, commonly used neuroimaging phenotypes."

Three burning questions about the first brain reference charts - STAT

Brain charts for the human lifespan (open access)

Your brain expands and shrinks over time — these charts show how

Amazing stuff!

Once more typical overblown concerns are expressed in accordance with prevailing ideology:

"Even so, the authors caution that their database isn’t completely inclusive — they struggled to gather brain scans from all regions of the globe. ...
Despite the size of the data set, [scientists] acknowledge that their study suffers from a problem endemic to neuroimaging studies — a remarkable lack of diversity. ..."

Scientists are human, all too human!

"... [scientists have] amassed more than 120,000 brain scans — the largest collection of its kind — to create the first comprehensive growth charts for brain development. The charts show visually how human brains expand quickly early in life and then shrink slowly with age. ...
Because brain structure varies significantly from person to person, the researchers had to aggregate a huge number of scans to create an authoritative set of growth charts with statistical significance. ..."

From the abstract:

"Over the past few decades, neuroimaging has become a ubiquitous tool in basic research and clinical studies of the human brain. However, no reference standards currently exist to quantify individual differences in neuroimaging metrics over time, in contrast to growth charts for anthropometric traits such as height and weight. Here we assemble an interactive open resource to benchmark brain morphology derived from any current or future sample of MRI data (http://www.brainchart.io/). With the goal of basing these reference charts on the largest and most inclusive dataset available, acknowledging limitations due to known biases of MRI studies relative to the diversity of the global population, we aggregated 123,984 MRI scans, across more than 100 primary studies, from 101,457 human participants between 115 days post-conception to 100 years of age. MRI metrics were quantified by centile scores, relative to non-linear trajectories of brain structural changes, and rates of change, over the lifespan. Brain charts identified previously unreported neurodevelopmental milestones, showed high stability of individuals across longitudinal assessments, and demonstrated robustness to technical and methodological differences between primary studies. Centile scores showed increased heritability compared with non-centiled MRI phenotypes, and provided a standardized measure of atypical brain structure that revealed patterns of neuroanatomical variation across neurological and psychiatric disorders. In summary, brain charts are an essential step towards robust quantification of individual variation benchmarked to normative trajectories in multiple, commonly used neuroimaging phenotypes."

Your brain expands and shrinks over time — these charts show how Based on more than 120,000 brain scans, the charts are still preliminary. But researchers hope they could one day be used as a routine clinical tool by physicians.

Brain charts for the human lifespan (open access)

Brain Exams Instead Of Multiple Choice Tests

Posted: 7/20/2019

“Here, we investigated whether patterns of brain activity collected during a concept knowledge task could be used to compute a neural ‘score’ to complement traditional scores of an individual’s conceptual understanding” (S2)

Are we entering a new age of measuring human cognition? Mind reading ante portas!

I thank the author of S1, Sibylle Anderl, for giving me the idea for this blog post!

Sources (S):

1. NEUROIMAGING : Hirnscan statt Klausur? (7/11/19)
2. Decoding individual differences in STEM learning from functional MRI data (5/2/19)