Functional Near-Infrared Spectroscopy (fNIRS)

 
Digital holographic imaging system operating in the near-infrared (NIR) at 1064 nm for structural and functional brain signals (John Hopkins Applied Physics Lab and School of Medicine)
 
The advanced optical sensor for brain activity that had been announced by Facebook building 8 (Regina Dugan) (video https://youtu.be/kCDWKdmwhUI?t=588) would be developed by the John Hopkins Applied Physics Lab (chief scientist David Blodgett) based on prior experience of the APL and the John Hopkins Medical School from the Revolutionizing Prosthetics DARPA Program (https://www.jhuapl.edu/PressRelease/170419b).
 
The APL (https://www.jhuapl.edu) is one of the six DARPA grantees for the Next-Generation Nonsurgical Neurotechnology (N3) program (announcement on 2019-05-20 https://www.darpa.mil/news-events/2019-05-20
 
As it had been mentioned by Regina Dugan at her presentation, if we illuminate our finger with a laser pointer we do not get a sharp (increased resolution) dot but instead the whole finger lights up as we get a diffuse signal through the tissue. This is due to the fact that the tissue scatters the photons in different directions. Ideally, from the return signal we would analyse only the non-scattered photons which are those that bounce off in a straight line ("ballistic photons"). However, their number is very small and we would need an extremely sensitive sensor to capture them for analysis. The suggested approach would be to use also those that are scattered with a small angle.
 
An alternative approach suggested by another scientist would be to analyse the scattering from the tissue and to then illuminate in such a way that the photons scatter at the desired angle.
 
 

 

Figure 1: Tweet by the APL announcing the DARPA grant 

https://twitter.com/JHUAPL/status/1130557026784858112

 

 

 

Functional Near-Infrared Spectroscopy (fNIRS) with Ultrasound focusing

 
 
Dr. Kainerstorfer’s near-infrared EEG (detection of vascular and neuronal changes) will be combined with an ultrasonic wave focusing approach to increase resolution and to solve the major problem that prevents optical/electromagnetic waves from reaching the brain, the dispersion caused by overlaying tissues. Following consolidation of the principle a head gear will be designed.
 
 

 

Video 1: https://youtu.be/4gXuOuXZEeo 3min11s: researcher affecting an ultrasonic wave with his hands placed near the sound source, 3min28s: EEG near-infrared sensor

 

 

 

 

Functional Infrared Spectroscopy combined with Holography (Phase-conjugation) 

 

Illumination of brain with infrared light leads to photon scattering resulting in a faint return signal.


By predicting the scattering we can design a holographic pattern for illumination that results in photon focusing in order to obtain a strong signal.

 

Holography-mediated de-scattering of light.


Holographic illumination of the brain compensating for tissue scattering thereby allowing photon focusing.

 

Other applications: detections of tumors, stroke

 

 

Excerpts from https://www.openwater.cc/faq-1 - Question: "What are the key advantages of the holographic method used in Openwater versus diffuse optical tomography?"

 

The approach consists of the use of "a novel kind of LCD and detector combination we are pioneering in concert with infrared light sources."

 

"we make a hologram of the brain or tissue, and invert the hologram with a computational process called phase conjugation to neutralize the effect of the scattering of the brain to make it effectively transparent." 

 

"Then we look at the differential effects of the color change of the blood voxel-by-voxel where oxygen is being consumed (which is exactly what fMRI does, but we do it with an LCD that lines the inside of say a ski-hat)." 

 

"We are also using this system architecture to look at refractive index change of the neuron as its action-potential changes on the millisecond time scale, and the differential scattering of a neuron as its surface roughens in a millisecond as a voltage propagates along it. Neither MRI nor fMRI can look directly at the neurons, we believe we can."  

 

"We are working on using the holographic phase-conjugate approach in reverse as well. As we develop those systems, which will likely ship in subsequent generation products, one can imagine many benefits, such as doing surgery without cutting, ablating tissue, removing plaque from clogged arteries, and the delivery of localized treatments." 

 

"At the extreme we believe we can change neuron states, ideas, and memories with this method."

 

Technology section of website https://www.openwater.cc/technology

TED Talk (including transcript)
https://www.ted.com/talks/mary_lou_jepsen_how_we_can_use_light_to_see_deep_inside_our_bodies_and_brains/

 

 

https://events.technologyreview.com/video/watch/mary-lou-jepsen-openwater-evolution-of-interfaces/

 

 

 

 

Figure 2: Excerpt from interview by Mary Lou Jepsen - https://www.facebook.com/informationbookcom/posts/482327715440748