Ultrasound imaging of the brain

Even low-dose ultrasound (what they use on pregnant woman) results in ultrastructural changes in brains [0], specifically at the nodes of Ranvier (the gaps between myelin along axons). See also [1] for a review.

[0] Ellisman MH, Palmer DE, André MP (1987), "Diagnostic levels of ultrasound may disrupt myelination," Experimental Neurology 98:78–92 https://pubmed.ncbi.nlm.nih.gov/3308504/

[1] Quarato, C.M.I., Lacedonia, D., Salvemini, M., Tuccari, G., Mastrodonato, G., Villani, R., Fiore, L.A., Scioscia, G., Mirijello, A., Saponara, A. and Sperandeo, M., 2023. A review on biological effects of ultrasounds: key messages for clinicians. Diagnostics, 13(5), p.855. https://pmc.ncbi.nlm.nih.gov/articles/PMC10001275/

Cool work and proof of concept, and very excited to see where this goes. However, I do think there is enough exaggeration and missing information here that it warrants some critical appraisal. What's really missing is a comparison and validation with any existing medical imaging tech. Whole brain, contrast-free neurovascular imaging is essentially solved with MRI, why not run a scan and compare? Ultrasound is of course portable and less expensive, but MRIs are actually widely available in most cities at reasonable cost for medical workflows, and low-field brain MRI is addressing the portability and cost issues to some extent. I guess they are pitching this as a wearable "telepathy" device, which I think appropriately differentiates their product, but of course, this wording also invokes a framing that "you won't / don't need to know how it works," which invites skepticism and a higher bar for validation in my view.

> The bubbles themselves are pockets of sulfur hexafluoride encapsulated in lipid shells.

The high resolution images were generated by injecting sparse bubbles of this contrast agent. How sparse are they? Is the image we see a stacked set of many bubbles over time composited together?

Their aspirations at the end of doing this without the bubbles are great, but there’s a big “now draw the rest of the owl” energy around that leap. The first technique relies entirely on the bubbles, but they provide no explanation for how they think this could be achievable without the bubbles other than vaguely saying that technology is advancing.

re: imaging red blood cells

The super-resolution trick as they’ve done it is highly reliant on the sparseness of the bubbles. If you imagine a point or a very sparse set of points at low resolution, you can fit for the locations of those points even though you don’t see them clearly. This is a common technique in radio astronomy and (I assume although I don’t have personal knowledge) astrometry, and compressed sensing was an extremely hot field a while back.

But RBCs are weird squishy things, and they fill the bloodstream quite densely, and ChatGPT estimates that they’re spaced about 20µm apart and that, when confined to a capillary, they’re about 7µm long. (And that sounds at least plausibly correct to me.)

So, even ignoring the much worse scattering properties of RBCs, they not nearly as sparse. You mostly lose a whole dimension of sparseness and up trying to resolve the entire capillary. Which seems possible but much harder. Unfortunately, brain capillaries are about 40µm apart, so the result might be a mess.

The article did not say what wavelength they’re using or what their native (wavelength/2) resolution is.

This is complete nonsense. Ultrasound can’t effectively penetrate the skull. The entire thing (and Midjourney’s) is vibed-up nonsense.

The only reason this even exists as a brainfart and hasn’t been immediately laughed out of VC funding is because other imaging modalities require either ionising radiation (illegal to produce without source licences) or an enormous magnet (would be wildly unsafe in the hands of what appear to be circus clowns).

Geoffrey Hinton was hilariously wrong 10 years ago about replacing radiologists, and this is just embarrassing. Maybe try fixing US healthcare funding instead if you want cheaper scans.

Can anyone explain how this ultrasound can see through the skull?

I've worked on ultrasound devices and data, the shadows from bone, and distortions caused by tissue types were very difficult. If this device can deal with those distortions it would already be useful for lung imaging.

Looking at the animations, it’s not hard to imagine this being a fast, low cost test for strokes that can be deployed basically anywhere in the world. Life saving technology.

Not trying to sound alarmist at all but I am wondering if ultrasounds are safe to be used like this? My understanding is it's basically a high-frequency sound wave which is probably fine for most tissue usage, however here it says it's scattering off of red blood cells. I don't know why that feels so unsettling to me.

Amazing spacial precision but the article doesn’t mention the time domain. I assume a brain interface needs to have a pretty high sampling rate in order to meaningfully decode human thought.

Meta is also going at it [0], which inevitably makes me ponder some orwellian questions for the near future:

If I bring my pet mouse to the cinema and my friend scans the movie back using his apple ifmri does the DRM still holds or will the mouses be DRM locked? Will my iris suffice for booting my computer or would I need to press accept all brainwave cookies? Can I email my local Flock representative to install a new Brain Pole in my neighborhood? I saw a bunch of dark thoughted young males around and my amazon think camera says the probability of missing packages increased.

[0]https://ai.meta.com/blog/tribe-v2-brain-predictive-foundatio...

Who could've thought that injecting SF6 into blood vessels is actually safe enough to be FDA-approved... interesting.

It feels like ultrasound is solving everything for the last week.

I thought the whole "we can guess what you're thinking from an MRI" thing was BS, along the lines: take a small set of photos, image people's brains as they are looking at these pictures, to map to some low-dimensional vector of "brain activity". Then show them some of these (in sample!) pictures, measure the vector of activity and predict back what they were looking at.

Happy to be corrected. But if that's right then this... does the BS thing in a potentially less intrusive way?

Every few years one of these ultrasound companies comes around and promising to revolutionize medical imaging and nothing ever comes of it. Anyone remember https://www.openwater.health? The same ideas are in a perpetual state of being reinvented and part of me thinks its just a hustle for the MIT Media Lab/Stanford Imaging grads to give them something to do.

The tell is "super resolution", "brain computer interface" and "mixed modality" -- adding some contrast agent here, or maybe an IR light source.

It turns out the nyquist limit, diffraction and physics are real things.

Is this the same tech the Midjourney scanner device is using?

We could have standing/lean back MRI. But it would require taller rooms which are non standard.

How about just getting it more established in orthopedic practices so patients aren't required to 1. See ortho for MRI referral 2. schedule mri at imaging facility 3. PAY $750 - $3000 for an MRI 4. Wait to get back into ortho.

I really don't understand why a fetus' heart can be examined for defects, but you can't use it in the office to tell me if my labrum is torn?

This is ridiculously cool, but I have a ton of questions.

> The bubbles themselves are pockets of sulfur hexafluoride encapsulated in lipid shells. They're an FDA-approved contrast agent,

Combined with ultrasound, could these be causing damage of any kind to the vasculature?

> A few years ago, a paper came out that blew our minds. The idea was that you can decode what someone is looking at just from their brain activity.

How realistically close can this get to reading thoughts, visuals, etc.?

Do we have a path to imaging people's visual cortex? Their inner lives, dialogues, memories? (Scary thought - this could be used as an interrogation tool without consent. "Did you kill Bob?" could be a simple brain scan.)

Can it be done in real time in a feedback loop and perhaps be used as an advanced reinforcement learning system?

Most retarded shit I've ever heard, and I'm glad someone is losing their investment money on this company.

Sulfur hexafluoride escaping is exceptionally damaging as a greenhouse gas, is there nothing else they can use?

Edit: wow, serves me right for asking / not understanding that contrast means SF6...