[HN Gopher] Wearable device for noninvasive optical brain imaging
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Wearable device for noninvasive optical brain imaging
Author : geox
Score : 49 points
Date : 2022-01-21 17:06 UTC (5 hours ago)
(HTM) web link (spie.org)
(TXT) w3m dump (spie.org)
| ajb wrote:
| That's really amazing. 2kg still seems pretty heavy though, more
| than a typical motorcycle helmet
| errcorrectcode wrote:
| I guess that's more practical than what another BCI company wants
| to do, e.g., implant 10k's of nanoscale sensors directly in the
| brain and eventually establish a read-write interface.
| DoingIsLearning wrote:
| I don't understand the breakthrough here, they miniaturized
| fNIRS?
| cknizek wrote:
| Not a breakthrough. This technique has been known about for at
| least two decades.
|
| Most fNIRS uses the amplitude-based, continuous-wave modality
| to compare chromophore concentrations resulting from
| thermovascular coupling.
|
| This uses time-domain based. What this means more formally is
| that it uses the impulse response created from a fast optical
| imaging source to then detect scattering changes in the cortex
| that ideally correspond to neuronal activation (or lack
| thereof).
|
| I was actually working on a very similar device a few months
| ago. I had to give up as the chip shortage made the specialty
| ICs required to pull this off damn near impossible to buy.
|
| There are a couple of things that make TD-NIRS a bit trickier.
| First off, it relies upon counting photons. This makes it
| susceptible to all sorts of noise, coupled with the fact that
| you need a photodetector with a very fast rise time and at
| least 10-20% detection of incident photons upon the detector.
|
| Benefits - Extremely fast (millisecond-range) neuronal activity
| detection - Less susceptible to motion artifacts - Very
| localized detection, scattering is well-modeled
|
| Drawbacks - Requires extremely fast sampling rate - Above
| sampling rate makes multiplexing difficult - Still susceptible
| to all kinds of noise
| anonymouse008 wrote:
| Mary Lou Jepsen's Open Water was looking at something similar
| -
|
| I'm going to say something stupid simple: Any technique
| imaging the brain outside the skull is hard. Much of these IR
| technologies are noble in terms of their general science and
| engineering learnings, but in terms of practicality, sub-
| optimal.
|
| Curious to know if you've experimented with other modalities?
| My base is fNIR and EEG device manufacturing, while just
| being exposed to (f)MRIs, MEGs and the like.
| cknizek wrote:
| I currently do research in MRI.
|
| I'm not entirely sure what you mean about IR technologies.
| Almost all medical imaging done today is done outside the
| skull. The only exception is ECoG, which is only medically
| used for patients with severe epilepsy. This is because
| open-brain surgery is an extraordinarily risky and
| expensive proposition.
|
| Every single imaging modality has strengths and weaknesses.
| It is the goal of the physician, and of the radiologist, to
| choose the appropriate imaging modality for the patient.
|
| NIRS is not always the best choice, especially not for
| medical imaging. But it's a good choice if you are looking
| for a portable modality that can image neuronal activation
| in the cortex.
|
| EEG is already difficult because you can't just add probes
| to increase spatial resolution. There is a fundamental
| limit the information that can be reliably gathered solely
| based upon the sodium-ion voltage potentials of neurons.
| anonymouse008 wrote:
| 'Tis also my read on the technology. They originally intended
| to miniaturize MEGs, which would have been remarkable, but
| diverted to the more immediately feasible. With $100m in
| personal funding, I felt MEG was absolutely the right route.
|
| I'm let down a bit by the recent marketing as well - when
| thinking optical sensing for neurology, you really think
| optogenetics like applications.
| anodyne33 wrote:
| Isn't that a bit apples v oranges? I've had a MEG and I'm
| floored by the technology but would a better analog be a PET?
| We're looking for two different things, metabolism v
| saturation but it seems like they're both in the physical or
| structural realm than the electrical.
| cknizek wrote:
| One of the main advantages of TD-NIRS is that the signal
| it's imaging is "electrical".
|
| Modalities like PET, BOLD fMRI, and CW-NIRS do depend upon
| saturation changes. For BOLD and CW-NIRS, it's the change
| in blood oxygen saturation.
|
| TD-NIRS images the fast optical signal that is correlated
| with electrical activity in the cortex. MEG images the
| magnetic fields correlated with electrical activity in the
| cortex. IMO, they're pretty similar.
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