Surely this is easily solved with time-reversed acoustics. Just stab a transmitter into the brain with an ice pick to the point you want to measure, and pick up the signal at lots of locations around the skull. Now you have both a mapping from an input signal (the reverse of the signal you picked up) that you can send to precisely target that point, and you know it looks like after it comes out from that point (the original signal you picked up).
Now you can tell exactly what is going on and the person is thinking! Specifically it'll be either: (1) "oh my god, I have an ice pick in my brain" or (2) nothing, because they have an ice pick in their brain.
Nah, this only works if you’re willing to leave the ice pick there, because the ice pick will have a wildly different speed of sound than the bone or brain, and it will scatter the ultrasound strongly as a result.
Gosh, you're both making this harder than it needs to be. Just use a drill. Drill all the way to the target point, push the transmitter to the end of the borehole, and fill the rest with tofu. This way you minimize acoustic artifacts not just from the test equipment, but also from shattered skull bone fragments. This would also let you take a continuous linear single-axis scan - just keep the transmitter running as you pull it out slowly, letting tofu flow around it.
> Just stab a transmitter into the brain with an ice pick to the point you want to measure, and pick up the signal at lots of locations around the skull.
It wouldn't be the first time ice picks have been used inside the brain. In answering a question [1] on what the difference is in medicine between an -ectomy, an -ostomy, and an -otomy in The Straight Dope we find this:
> • Finally, there’s “-otomy,” (or “-tomy”), which means to slice it up, i.e., an operation in which cutting is involved. Thus we can distinguish a lobectomy, in which a lobe, typically of the brain, is removed, from a lobotomy, in which they merely jab an ice pick in there and chop things up.
> I’m not kidding, either. You might want to read an engrossing volume entitled Great and Desperate Cures: The Rise and Decline of Psychosurgery and Other Radical Treatments for Mental Illness, by Elliott Valenstein (1986). Valenstein quotes a letter written in the mid-1940s by one prominent lobotomist, Walter Freeman:
>> I have also been trying out a sort of half-way stage between electroshock and prefrontal lobotomy [to treat mental patients]. … This consists of knocking them out with a shock and while they are under the ‘anesthetic’ thrusting an ice pick up between the eyeball and the eyelid through the roof of the orbit [the bony cavity that contains the eye] actually into the frontal lobe of the brain and making the lateral cut by swinging the thing from side to side. I have done two patients on both sides and another on one side without running into any complications, except a very black eye in one case. There may be trouble later on but it seemed fairly easy, although definitely a disagreeable thing to watch. It remains to be seen how these cases hold up, but so far they have shown considerable relief of their symptoms, and only some of the minor behavior difficulties that follow lobotomy. [That is, prefrontal lobotomy, which typically involved boring holes through the front of the skull. The ice pick operation is called a transorbital lobotomy.] They can even get up and go home within an hour or so. If this works out it will be a great advance for people who are too bad for shock but not bad enough for surgery.
> Freeman went around the country in the late 1940s demonstrating this technique in mental hospitals. These exhibitions reportedly went well for the most part, except on those occasions when the patient bled too much or the ice pick broke off within the orbit or inside the skull. To remedy this problem, the ice pick was later replaced with a sturdier instrument and an ordinary carpenter’s hammer was used to drive it into the brain.
> The first lobotomy in the United States took place on September 14, 1936. By August 15, 1949, the procedure had been performed 10,706 times. In the mid-1950s the popularity of the operation waned due to the availability of psychotropic drugs, which offered similar benefits without the trauma. One hopes today the practice is extinct, but you never know.
“The thing that nobody tells you is that you can buy a real human skull online (shoutout to skullsunlimited.com). We did that, and then CT scanned it.”
“People often quote 22 dB/cm/MHz attenuation of ultrasound. Decibels are a logarithmic scale, so with 1.4 cm of roundtrip skull distance, and typical fUSI frequencies of 10 MHz, this would be 14 orders of magnitude of attenuation! In physics, there's a word for 14 orders of magnitude of attenuation. It's called zero, i.e., you will measure nothing.
But where did the 22 dB/cm/MHz attenuation number come from? We were skeptical…”
I just recently donated my body "to science" (actually to a medical school). They specifically asked if keeping skeletal parts was a-ok or not as part of the authorization form signed. They also asked if stabbing, burning, or blunt force trauma was ok. I told them they could do whatever the heck they wanted, just not to waste anything. If that includes selling parts to make money for the school, cool by me. The best part of the deal is zero funeral expenses, and they'll even give your family back the cremated ashes for free. Though as part of the additional 'ok to skeletonize' part I signed, no remains would come back to the family.
The most common ways to remove flesh from the skeleton avoiding bone degradation as much as possible are maceration (bacterial, enzymatic), or flesh-decomposing bacteria (edit: and beetles). There's not much left for cremation. Mechanically defleshing the bones would be a bit more destructive, still not leave clean bones, and at the very least would be gruesome for the cleanup crew.
I don't mean to discount the cool imaging-related reconstruction of a point spread function, but rather to say that ultrasound attenuation through the skull an soft tissue has already been well characterized and it's not a surprise that it is viable to pass through.
Correct me if I’m wrong - but the novel thing is not that it’s possible for ultrasound to pass through the skull, but that it’s possible for it to pass through the skull and back in a way that an image can be reconstructed.
A commercial medical ultrasound imaging device in doppler mode can pick up and map onto the image plane some of the vessels in the brain through the skulls. But mostly just through the temporal bones(where the skulls is like 1-2mm thick). (The commercial machines run doppler on lower frequency than imaging signal so you get no s tructural image this way, only the color doppler map(unless you find a place in the skull where an emissary vein passes through the bone table where the image signal can ride through))
Through the temporal bone of most people you can catch some sparse doppler signals with average hospital gear.
The fontanelles enable good ultrasound imaging on an entirely different level. A highres greyscale image vs a few sparse blobs of doppler from major vessels.
> OpenWater's Transcranial Focused Ultrasound Platform. open-LIFU is an ultrasound platform designed to help researchers transmit focused ultrasound beams into subject’s brains, so that those researchers can learn more about how different types of ultrasound beams interact with the neurons in the brain. Unlike other focused ultrasound systems which are aimed only by their placement on the head, open-LIFU uses an array to precisely steer the ultrasound focus to the target location, while its wearable small size allows transmission through the forehead into a precise spot location in the brain even while the patient is moving.
FWIU NIRS is sufficient for most nontherepeautic diagnostics though. (Non-optogenetically, infrared light stimulates neuronal growth, and blue and green lights inhibit neuronal growth)
They are planning to locally change the electrical conductivity of brain tissue by focused ultrasound, modulate that with at few hundred kHz and do a lock-in (EEG) measurement to deduce electrical activity at that spot on the scale of 1mm. Pretty wild if that actually works.
Fascinating — I thought ultrasound was already regularly in use for reading oxygenation levels, I had no idea it was new!! I’ve gotta try this. I don’t love the modulation side, but the measurement side is incredible. Invasive tech is unnecessary and terrifying IMHO
Hmm, I see, I think understand a bit better now -- thanks.
Is it fair to say that their claims about spatial resolution being >>> existing EEG options are jumping the gun? If I understand correctly, you need to be targeting individual 1mm^2 regions with individual acoustic lenses, which means 17,000 channels would required 17,000 separate, uniquely-tuned ultrasound emitters, yes? Even if that's possible without messing up the data (the MHz range is big, but is it that big?) it seems like a trivial impossibility to fit that in one headset -- even the standard 32-64 EEG channels alone seem like a long shot. But maybe I'm overly cynical, or one emitter could be used to usefully excite multiple regions at once?
Another oddity in that paper is that it reads like we're trying to find persistent signals in the brain, like a needle in a haystack, whereas my understanding was that the field is moving decisively towards tracking signal changes over time in a given region. Is my intuition correct that accounting for a moving target would add considerable complexity to this approach?
Either way, thanks for sharing the link. Definitely thought-provoking stuff...
Thanks for your questions! I was one of the people who worked on the project. To answer your questions:
> Is it fair to say that their claims about spatial resolution being >>> existing EEG options are jumping the gun? If I understand correctly, you need to be targeting individual 1mm^2 regions with individual acoustic lenses, which means 17,000 channels would required 17,000 separate, uniquely-tuned ultrasound emitters, yes? Even if that's possible without messing up the data (the MHz range is big, but is it that big?) it seems like a trivial impossibility to fit that in one headset -- even the standard 32-64 EEG channels alone seem like a long shot. But maybe I'm overly cynical, or one emitter could be used to usefully excite multiple regions at once?
Since the system is linear, you could use a single probe to focus at multiple spots. Each focus would be at a slightly different modulation frequency.
> Another oddity in that paper is that it reads like we're trying to find persistent signals in the brain, like a needle in a haystack, whereas my understanding was that the field is moving decisively towards tracking signal changes over time in a given region. Is my intuition correct that accounting for a moving target would add considerable complexity to this approach?
This method would indeed let you track signals that change over time. Lock-in-amplifiers can output time-varying signals.
I still have lots of questions, but I think that's on me haha. Thanks so much for taking the time for this, and for pushing forward the human race in such a groundbreaking manner. Hope y'all are doing well in these dark times.
A modern clinical ultrasound probe have something in the range of 128 to 512 elements only. But despite that you get a real-time video stream at a lot higher resolution than a 512 pixel postage stamp.
Why isn't ultrasound used in orthopedics? Instead of MRI rigamarole, why can't the doc put the wand to my shoulder in the office and tell me if it's a tear?
'Previous work showed that tofu is desirable as a phantom material, both because it is fast to get and because it has similar physical properties (density, speed of sound) as soft tissue.'
Haha wonderful.
Progress in making measurements through the skull useful might be how we finally get to precisely measure side-effects elsewhere: comparing healthy adult skulls to proper control groups. Always seemed odd to me how unspecific the thermal safety limits are, though the peak is expected depend on localized unknowns.
Nice timing, tomorrow I'll be participating in a study doing transcranial ultrasonic neuro-modulation, meaning using ultrasound not just to map brain activity but to influence it (the point of the study is inhibiting the Default Mode Network).
If anyone's interested I found those two paper really interesting:
- Aubry et al 2023[1], on potential risks and limitions of using focused ultrasound in the brain (tldr we don't know but have conservative estimates. Really interesting for me to see that HN article adding to that)
- Lord et al 2024[2], a first study on using Transcranial Focused Ultrasound to modulate the DMN and subjective experience
I am a physician who has been following tfus for sometime now - Specifically, it’s ability to create persistent alterations in consciousness/Perception/Cognition- Similar to those found in long-term meditators. My understanding is that there are a few people in the world that can safely do this currently. If you feel comfortable sharing, it would be lovely to hear more details :)
For sure, though I'll probably have more info after the study.
It's done by the same people as the second paper I linked, on people attending a 10-day silent meditation retreat. My understanding so far is that the participants will be "zapped" a couple of time over the 10 days, to explore exactly what you describe ie alterations of consciousness similar to what's found in long term meditators on retreat, except induced on people who are already on retreat instead of people who'll have to go back to work afterwards.
I'll have more to report in a couple weeks time!
(If you'd like to share, I'm also curious as to what interests you in that field of study)
By the way Bryan Johnson recently mentioned a novel technique of using ultrasound to de-calcify pineal gland for improving sleep as it gets worse with aging - this sounds really intriguing to me.
You don’t. The bubbles only form once the skull is outside the body. When it gets out of the body, the gaps that used to be filled with water get filled with air.
Awesome! I know of efforts to leverage focused ultrasound to shorten sleep cycles and improve mental health. There’s so much more possible in neuroscience, great to see this work is gaining steam.
I think you are referring to slow-wave enhancement wrt "shorten sleep cycles", which probably isn't the right way to look at it.
We've been developing slow-wave enhancement for the past 4 years using auditory stimulation.
The problem with using focused ultrasound to accomplish this (I believe), is that the focal point creates heat, and I don't believe we want to be consistently creating hot spots of neurons in the brain.
Other methods (acoustic, visual, haptic) have proven efficacy by "tricking" the brain into increasing slow-wave delta power, and tMCS (magnetic) coaxes the neurons into a slow-wave pattern - though this is not realistic outside of a clinical setting atm.
Absolutely there is tons happening in neuroscience (lots here in Sydney, Aus), and focused ultrasound has it's place, but as a daily use, I'm not there with it yet.
For treatment of depression, for diagnosis, etc, absolutely. Though in depression treatment, SAINT protocol tCMS is very impressive.
I don’t know how much is public, the method I’ve seen “bounces” around and aims for a more global effect. Like a sonicare for the brain. No idea if it will work long-term as intended, but seems worth trying.
22 dB/cm/MHz, 1.4cm, 10 MHz gives ~40dB, which happens to be 4-orders of magnitude difference in power. Not sure how they got 14 orders of magnitude for the attenuation.
However I don't see any expression claiming a linear frequency dependence of attenuation up to 10 MHz.
> the number people will tell you in conversation.
Is very vague. Do your own research, find actual measurement data, don't extrapolate a few sub MHz measurements out to 10 Mhz, especially not if the error bars become ludicrously big.
Since I can't find the quoted frequency coefficient for attenuation I look at the possible candidates in that article: there's Figure 11, Table 1 and Table 3.
My gut feeling tells me they used table 3:
frequency in MHz | Longitudinal attenuation in Nepers per meter
0.272 | 14 +/- 17
0.548 | 53 +/- 43
0.840 | 70 +/- 28
I suspect they discarded the middle frequency because of the large error bar, so they are left with
Mhz | Np per m
0.272 | 14 +/- 17
0.840 | 70 +/- 28
the difference in frequency is 0.568 Mhz
so the difference in attenuation is then 56 +/- 45 Np per m. Yes the standard deviation is almost as large as the value. Let's see if we arrive close to their supposedly "quoted assumed linear frequency dependence of 8.3 dB / cm / Mhz "
2 x (56 Np per m) / ( 0.568 MHz x 100 cm per m x log(10) Np per 10 dB)
= 8.56 dB / cm / Mhz
close to their 8.3 "quote" which is really their own deduction, or whomever "derived" it in "conversation".
If you calculate the error bar: 8.56 +/- 6.88 dB / cm / MHz.
What they independently measured (props! actually good science):
11.18 dB / cm / MHz
Thats 2.62 / 6.88 = 0.38 standard deviations away. Thats not new science in the sense of hypothesis rejection, but a valuable extra datapoint refining the literature of values.
The likelihood of measuring a value 0.38 or more standard deviations away from the expected value would be: 70.4 % so not very surprising at all. Basically in conformance with the 8.56 +/- 6.88 dB / cm / MHz value.
Yeah I did a (mostly failed) PhD on ultrasonic imaging and found many things that worked in simulations but not in practice. The fancier your imaging algorithm gets the most ill posed it becomes and more sensitive to noise and errors.
Even if you add noise to your simulation , when you go to the real world it will have lots of sources of noise and errors that you didn't model. In this case I suspect aligning the CT scan with the ultrasound probe will be extremely difficult.
Also there's a reason ultrasonographers are so highly paid, and it's mostly used for pregnancies. In normal tissue it kind of sucks as an imaging method. (On an absolute scale; obviously it's amazing technology.)
I recently had the idea to start a company that measures specifically properties of the pineal gland, I think people would pay for that. I have no domain expertise whatsoever. If anyone wants to investigate this deeper with me let me know
I don't know how it goes in the US, but AFAIK there needs to be an actual medical reason to expose people to ionizing radiation. That is presuming that you would want to go for the most affordable option of using CT scanner which would set you back for three quarters of a mil approximately in hardware alone. Using an MRI would easily double or triple that, but it would provide better image.
I don't think there's enough rich pineal gland enthusiast to justify the cost, even if the system was truck mounted and mobile and thus hypothetically able to reach wider customer base.
Yeah the focus would be on inventing non-radiation means of scanning, e g further developing Ultrasound Elastography (vibrations) or Diffuse Optical Tomography (near-infrared light). So there's the concept of a thingamajig, a plot device that moves things forward. Focusing on a narrow area gives opportunity for specificity hacks that can then unlock further pivot opportunities. You know start specific and go wider once something works
Thanks for the advice. Potentially, it's not insanely farfetched to assume AI and math (currently doing math) can unlock more precision with less data and invasiveness. While it's at one level physics, stronger algorithms and analysis can maybe reduce the size + cost + danger of the hardware, as well as require less data for more precision. Just a hunch. There are always plenty creative ways to experiment without animal harm as well, just a matter of attention and will to explore. Yeah, safety is super important, and if this sort of scanning can be made better in a fresh way that would unlock a lot. Just like having a 10x cheaper API that does the same job automatically becomes useful in new unforeseen ways.
Money
Oh that sort of why
Because it's a spiritual thing, the yuppies who are also slightly hippies would want to see size and health and calcification %, more data sort of like a feedback loop like if you can do crunches and see more pronounced abs in the mirror, why wouldn't you want to meditate and drink and eat healthy and see if stuff changes in the physical state of the brain
Surely this is easily solved with time-reversed acoustics. Just stab a transmitter into the brain with an ice pick to the point you want to measure, and pick up the signal at lots of locations around the skull. Now you have both a mapping from an input signal (the reverse of the signal you picked up) that you can send to precisely target that point, and you know it looks like after it comes out from that point (the original signal you picked up).
Now you can tell exactly what is going on and the person is thinking! Specifically it'll be either: (1) "oh my god, I have an ice pick in my brain" or (2) nothing, because they have an ice pick in their brain.
Nah, this only works if you’re willing to leave the ice pick there, because the ice pick will have a wildly different speed of sound than the bone or brain, and it will scatter the ultrasound strongly as a result.
What if it's a really skinny ice pick?
Apparently if you're really good, you can actually find the part of the brain that has to do with addiction and zap it.
They use ultrasound after getting it to work with a metal probe.
https://youtu.be/7BGtVJ3lBdE?t=837
Yeah, that's fair. I guess you have to make the ice pick out of tofu.
Gosh, you're both making this harder than it needs to be. Just use a drill. Drill all the way to the target point, push the transmitter to the end of the borehole, and fill the rest with tofu. This way you minimize acoustic artifacts not just from the test equipment, but also from shattered skull bone fragments. This would also let you take a continuous linear single-axis scan - just keep the transmitter running as you pull it out slowly, letting tofu flow around it.
Maybe this is what really happened to Trotsky.
> Just stab a transmitter into the brain with an ice pick to the point you want to measure, and pick up the signal at lots of locations around the skull.
It wouldn't be the first time ice picks have been used inside the brain. In answering a question [1] on what the difference is in medicine between an -ectomy, an -ostomy, and an -otomy in The Straight Dope we find this:
> • Finally, there’s “-otomy,” (or “-tomy”), which means to slice it up, i.e., an operation in which cutting is involved. Thus we can distinguish a lobectomy, in which a lobe, typically of the brain, is removed, from a lobotomy, in which they merely jab an ice pick in there and chop things up.
> I’m not kidding, either. You might want to read an engrossing volume entitled Great and Desperate Cures: The Rise and Decline of Psychosurgery and Other Radical Treatments for Mental Illness, by Elliott Valenstein (1986). Valenstein quotes a letter written in the mid-1940s by one prominent lobotomist, Walter Freeman:
>> I have also been trying out a sort of half-way stage between electroshock and prefrontal lobotomy [to treat mental patients]. … This consists of knocking them out with a shock and while they are under the ‘anesthetic’ thrusting an ice pick up between the eyeball and the eyelid through the roof of the orbit [the bony cavity that contains the eye] actually into the frontal lobe of the brain and making the lateral cut by swinging the thing from side to side. I have done two patients on both sides and another on one side without running into any complications, except a very black eye in one case. There may be trouble later on but it seemed fairly easy, although definitely a disagreeable thing to watch. It remains to be seen how these cases hold up, but so far they have shown considerable relief of their symptoms, and only some of the minor behavior difficulties that follow lobotomy. [That is, prefrontal lobotomy, which typically involved boring holes through the front of the skull. The ice pick operation is called a transorbital lobotomy.] They can even get up and go home within an hour or so. If this works out it will be a great advance for people who are too bad for shock but not bad enough for surgery.
> Freeman went around the country in the late 1940s demonstrating this technique in mental hospitals. These exhibitions reportedly went well for the most part, except on those occasions when the patient bled too much or the ice pick broke off within the orbit or inside the skull. To remedy this problem, the ice pick was later replaced with a sturdier instrument and an ordinary carpenter’s hammer was used to drive it into the brain.
> The first lobotomy in the United States took place on September 14, 1936. By August 15, 1949, the procedure had been performed 10,706 times. In the mid-1950s the popularity of the operation waned due to the availability of psychotropic drugs, which offered similar benefits without the trauma. One hopes today the practice is extinct, but you never know.
[1] https://www.straightdope.com/21341781/in-medicine-what-s-the...
JFK's sister Rosemary was lobotomized. Because her dad was an asshole, basically.
Either way they’re not scared of spiders any more! (p < 0.01)
“The thing that nobody tells you is that you can buy a real human skull online (shoutout to skullsunlimited.com). We did that, and then CT scanned it.”
This is an A+
“People often quote 22 dB/cm/MHz attenuation of ultrasound. Decibels are a logarithmic scale, so with 1.4 cm of roundtrip skull distance, and typical fUSI frequencies of 10 MHz, this would be 14 orders of magnitude of attenuation! In physics, there's a word for 14 orders of magnitude of attenuation. It's called zero, i.e., you will measure nothing.
But where did the 22 dB/cm/MHz attenuation number come from? We were skeptical…”
Skulls Unlimited really has their branding on point. I might just have to get one for the holidays.
Reddit claims they do background checks.
But others on reddit claim this is not the case. And their faq, policies, product description, and checkout page make no note of this at all.
Not just no note of background checks, but no note of restrictions of any kind.
There are many words about international shipping and related restrictions. But no “you need to be a doctor” as far as I see anywhere.
This is either a “reddit being reddit” situation, or skulls unlimited had a change in their policies in the past.
Just a cool $1800 for a Halloween prop.
For that price, it's gonna somehow have to be included in _every_ holiday.
Skulloween, Skullmas, Skullsgiving...
I think there's a Tim Burton movie about that.
All Skulls' Day, Skullster, Kwanzkull...
There’s a recent two part podcast about selling bones online, https://www.iheart.com/podcast/1119-sixteenth-minute-of-fame....
Part 2 has an interview with a law professor that specializes in death and what happens after people die. Fascinating!
When people "donate their body to science", they don't usually expect their parts getting sold to the public. But that's the reality of it.
I just recently donated my body "to science" (actually to a medical school). They specifically asked if keeping skeletal parts was a-ok or not as part of the authorization form signed. They also asked if stabbing, burning, or blunt force trauma was ok. I told them they could do whatever the heck they wanted, just not to waste anything. If that includes selling parts to make money for the school, cool by me. The best part of the deal is zero funeral expenses, and they'll even give your family back the cremated ashes for free. Though as part of the additional 'ok to skeletonize' part I signed, no remains would come back to the family.
I’d expect the fleshy parts to leave at least some ashes.
The most common ways to remove flesh from the skeleton avoiding bone degradation as much as possible are maceration (bacterial, enzymatic), or flesh-decomposing bacteria (edit: and beetles). There's not much left for cremation. Mechanically defleshing the bones would be a bit more destructive, still not leave clean bones, and at the very least would be gruesome for the cleanup crew.
The paperwork said they use beetles, though I suppose that they could end up removing the flesh however they liked.
Well, at least it goes to the user who values it most.
s/the public/citizen scientists/ and all is OK now!
This is fun, and the modeling is cool for sure, but it's well known that ultrasound can be used with surgical precision in the human brain.
Focused ultrasound is already used for non-invasive neuromodulation. Raag Airan's lab at Stanford does this for example using ultrasound uncaging.
https://www.frontiersin.org/journals/neuroscience/articles/1...
https://www.sciencedirect.com/science/article/pii/S089662731...
Also see the work by Urvi Vyas, eg
https://pubmed.ncbi.nlm.nih.gov/27587047/
I don't mean to discount the cool imaging-related reconstruction of a point spread function, but rather to say that ultrasound attenuation through the skull an soft tissue has already been well characterized and it's not a surprise that it is viable to pass through.
Correct me if I’m wrong - but the novel thing is not that it’s possible for ultrasound to pass through the skull, but that it’s possible for it to pass through the skull and back in a way that an image can be reconstructed.
Precisely
Not to mention transcranial doppler ultrasound for measuring blood flow.
To my knowledge, transcranial doppler doesn’t form images. It just gives you a single channel measurement that is very low resolution.
The method we’re proposing would have mm resolution.
A commercial medical ultrasound imaging device in doppler mode can pick up and map onto the image plane some of the vessels in the brain through the skulls. But mostly just through the temporal bones(where the skulls is like 1-2mm thick). (The commercial machines run doppler on lower frequency than imaging signal so you get no s tructural image this way, only the color doppler map(unless you find a place in the skull where an emissary vein passes through the bone table where the image signal can ride through))
Does viable transcranial doppler for poeple without fontanelles actually exist?
Through the temporal bone of most people you can catch some sparse doppler signals with average hospital gear.
The fontanelles enable good ultrasound imaging on an entirely different level. A highres greyscale image vs a few sparse blobs of doppler from major vessels.
OpenWater wiki > Neuromodulation: https://wiki.openwater.health/index.php/Neuromodulation
OpenwaterHealth/opw_neuromod_sw: https://github.com/OpenwaterHealth/opw_neuromod_sw :
> OpenWater's Transcranial Focused Ultrasound Platform. open-LIFU is an ultrasound platform designed to help researchers transmit focused ultrasound beams into subject’s brains, so that those researchers can learn more about how different types of ultrasound beams interact with the neurons in the brain. Unlike other focused ultrasound systems which are aimed only by their placement on the head, open-LIFU uses an array to precisely steer the ultrasound focus to the target location, while its wearable small size allows transmission through the forehead into a precise spot location in the brain even while the patient is moving.
FWIU NIRS is sufficient for most nontherepeautic diagnostics though. (Non-optogenetically, infrared light stimulates neuronal growth, and blue and green lights inhibit neuronal growth)
Also check out their other post: https://brainhack.vercel.app/ae
They are planning to locally change the electrical conductivity of brain tissue by focused ultrasound, modulate that with at few hundred kHz and do a lock-in (EEG) measurement to deduce electrical activity at that spot on the scale of 1mm. Pretty wild if that actually works.
Fascinating — I thought ultrasound was already regularly in use for reading oxygenation levels, I had no idea it was new!! I’ve gotta try this. I don’t love the modulation side, but the measurement side is incredible. Invasive tech is unnecessary and terrifying IMHO
Modulation is part of the measurement process in that case.
https://en.wikipedia.org/wiki/Lock-in_amplifier
Hmm, I see, I think understand a bit better now -- thanks.
Is it fair to say that their claims about spatial resolution being >>> existing EEG options are jumping the gun? If I understand correctly, you need to be targeting individual 1mm^2 regions with individual acoustic lenses, which means 17,000 channels would required 17,000 separate, uniquely-tuned ultrasound emitters, yes? Even if that's possible without messing up the data (the MHz range is big, but is it that big?) it seems like a trivial impossibility to fit that in one headset -- even the standard 32-64 EEG channels alone seem like a long shot. But maybe I'm overly cynical, or one emitter could be used to usefully excite multiple regions at once?
Another oddity in that paper is that it reads like we're trying to find persistent signals in the brain, like a needle in a haystack, whereas my understanding was that the field is moving decisively towards tracking signal changes over time in a given region. Is my intuition correct that accounting for a moving target would add considerable complexity to this approach?
Either way, thanks for sharing the link. Definitely thought-provoking stuff...
Thanks for your questions! I was one of the people who worked on the project. To answer your questions:
> Is it fair to say that their claims about spatial resolution being >>> existing EEG options are jumping the gun? If I understand correctly, you need to be targeting individual 1mm^2 regions with individual acoustic lenses, which means 17,000 channels would required 17,000 separate, uniquely-tuned ultrasound emitters, yes? Even if that's possible without messing up the data (the MHz range is big, but is it that big?) it seems like a trivial impossibility to fit that in one headset -- even the standard 32-64 EEG channels alone seem like a long shot. But maybe I'm overly cynical, or one emitter could be used to usefully excite multiple regions at once?
Since the system is linear, you could use a single probe to focus at multiple spots. Each focus would be at a slightly different modulation frequency.
> Another oddity in that paper is that it reads like we're trying to find persistent signals in the brain, like a needle in a haystack, whereas my understanding was that the field is moving decisively towards tracking signal changes over time in a given region. Is my intuition correct that accounting for a moving target would add considerable complexity to this approach?
This method would indeed let you track signals that change over time. Lock-in-amplifiers can output time-varying signals.
I still have lots of questions, but I think that's on me haha. Thanks so much for taking the time for this, and for pushing forward the human race in such a groundbreaking manner. Hope y'all are doing well in these dark times.
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A modern clinical ultrasound probe have something in the range of 128 to 512 elements only. But despite that you get a real-time video stream at a lot higher resolution than a 512 pixel postage stamp.
Why isn't ultrasound used in orthopedics? Instead of MRI rigamarole, why can't the doc put the wand to my shoulder in the office and tell me if it's a tear?
Someone skilled in musculoskeletal ultrasound can do it.
But that's a hard skill to develop.
'Previous work showed that tofu is desirable as a phantom material, both because it is fast to get and because it has similar physical properties (density, speed of sound) as soft tissue.' Haha wonderful.
Some say it tastes the same.
To get the same experience, you have to suck it through your teeth a bit too.
...if you close your eyes...
Progress in making measurements through the skull useful might be how we finally get to precisely measure side-effects elsewhere: comparing healthy adult skulls to proper control groups. Always seemed odd to me how unspecific the thermal safety limits are, though the peak is expected depend on localized unknowns.
love the writing in this
"In physics, there's a word for 14 orders of magnitude of attenuation. It's called zero, i.e., you will measure nothing."
Lots of great sentences in here as noted in the other comments.
As a point of comparison, GNSS works down to about 16 orders of magnitude attenuation (dbw).
Nice timing, tomorrow I'll be participating in a study doing transcranial ultrasonic neuro-modulation, meaning using ultrasound not just to map brain activity but to influence it (the point of the study is inhibiting the Default Mode Network).
If anyone's interested I found those two paper really interesting:
- Aubry et al 2023[1], on potential risks and limitions of using focused ultrasound in the brain (tldr we don't know but have conservative estimates. Really interesting for me to see that HN article adding to that)
- Lord et al 2024[2], a first study on using Transcranial Focused Ultrasound to modulate the DMN and subjective experience
[1] https://arxiv.org/pdf/2311.05359
[2] https://www.researchgate.net/publication/381488518_Transcran...
I am a physician who has been following tfus for sometime now - Specifically, it’s ability to create persistent alterations in consciousness/Perception/Cognition- Similar to those found in long-term meditators. My understanding is that there are a few people in the world that can safely do this currently. If you feel comfortable sharing, it would be lovely to hear more details :)
For sure, though I'll probably have more info after the study.
It's done by the same people as the second paper I linked, on people attending a 10-day silent meditation retreat. My understanding so far is that the participants will be "zapped" a couple of time over the 10 days, to explore exactly what you describe ie alterations of consciousness similar to what's found in long term meditators on retreat, except induced on people who are already on retreat instead of people who'll have to go back to work afterwards.
I'll have more to report in a couple weeks time!
(If you'd like to share, I'm also curious as to what interests you in that field of study)
It mentions using this as a computer interface but wouldnt prolonged use eventually open up the blood brain barrier?
By the way Bryan Johnson recently mentioned a novel technique of using ultrasound to de-calcify pineal gland for improving sleep as it gets worse with aging - this sounds really intriguing to me.
Shockwave lithotripsy for the brain.
Sounds like a perfect way to find yourself dead with massive brain hemorrhage and someone jailed for unlicensed meme-medtech.
Is there any evidence that calcifications of pineal gland influence sleep?
breaking up crystalline structures by force usually severely damages the tissue. but interesting it is.
How do you degas a skull in a living mammal and have an unharmed animal after?
You don’t. The bubbles only form once the skull is outside the body. When it gets out of the body, the gaps that used to be filled with water get filled with air.
Awesome! I know of efforts to leverage focused ultrasound to shorten sleep cycles and improve mental health. There’s so much more possible in neuroscience, great to see this work is gaining steam.
I think you are referring to slow-wave enhancement wrt "shorten sleep cycles", which probably isn't the right way to look at it.
We've been developing slow-wave enhancement for the past 4 years using auditory stimulation.
The problem with using focused ultrasound to accomplish this (I believe), is that the focal point creates heat, and I don't believe we want to be consistently creating hot spots of neurons in the brain.
Other methods (acoustic, visual, haptic) have proven efficacy by "tricking" the brain into increasing slow-wave delta power, and tMCS (magnetic) coaxes the neurons into a slow-wave pattern - though this is not realistic outside of a clinical setting atm.
Absolutely there is tons happening in neuroscience (lots here in Sydney, Aus), and focused ultrasound has it's place, but as a daily use, I'm not there with it yet.
For treatment of depression, for diagnosis, etc, absolutely. Though in depression treatment, SAINT protocol tCMS is very impressive.
I don’t know how much is public, the method I’ve seen “bounces” around and aims for a more global effect. Like a sonicare for the brain. No idea if it will work long-term as intended, but seems worth trying.
In case you didn't scroll to the end, they open sourced their code:
https://github.com/brain-hack-2024/transcranial-ultrasound/
Very neat.
The big question for me is - how will it feel on a live person. Is it going to be painful? Could it alter/damage the brain tissue?
So basically - how safe is this tech?
Ultrasound is safe at normal acoustic levels.
Infant babies frequently have their brain scanned through the open fontanels.
If you turn the volume up to 11 you'll boil water with or can use it to machine steel but the energy levels in clinical practice is safe
22 dB/cm/MHz, 1.4cm, 10 MHz gives ~40dB, which happens to be 4-orders of magnitude difference in power. Not sure how they got 14 orders of magnitude for the attenuation.
22 * 1.4 * 10 is not 40.
You are correct. 22*1.4 + 10 is, my bad.
I don't understand why they believed in such high attenuation numbers.
They quote a book that the public at large (including me) can not check for the 22dB/cm/Mhz number.
The next best quote is the 8.3 dB/cm/Mhz quote. That article is available to the public:
https://pmc.ncbi.nlm.nih.gov/articles/PMC1560344/pdf/nihms94...
However I don't see any expression claiming a linear frequency dependence of attenuation up to 10 MHz.
> the number people will tell you in conversation.
Is very vague. Do your own research, find actual measurement data, don't extrapolate a few sub MHz measurements out to 10 Mhz, especially not if the error bars become ludicrously big.
Since I can't find the quoted frequency coefficient for attenuation I look at the possible candidates in that article: there's Figure 11, Table 1 and Table 3.
My gut feeling tells me they used table 3:
frequency in MHz | Longitudinal attenuation in Nepers per meter
0.272 | 14 +/- 17
0.548 | 53 +/- 43
0.840 | 70 +/- 28
I suspect they discarded the middle frequency because of the large error bar, so they are left with
Mhz | Np per m
0.272 | 14 +/- 17
0.840 | 70 +/- 28
the difference in frequency is 0.568 Mhz
so the difference in attenuation is then 56 +/- 45 Np per m. Yes the standard deviation is almost as large as the value. Let's see if we arrive close to their supposedly "quoted assumed linear frequency dependence of 8.3 dB / cm / Mhz "
2 x (56 Np per m) / ( 0.568 MHz x 100 cm per m x log(10) Np per 10 dB)
= 8.56 dB / cm / Mhz
close to their 8.3 "quote" which is really their own deduction, or whomever "derived" it in "conversation".
If you calculate the error bar: 8.56 +/- 6.88 dB / cm / MHz.
What they independently measured (props! actually good science):
11.18 dB / cm / MHz
Thats 2.62 / 6.88 = 0.38 standard deviations away. Thats not new science in the sense of hypothesis rejection, but a valuable extra datapoint refining the literature of values.
The likelihood of measuring a value 0.38 or more standard deviations away from the expected value would be: 70.4 % so not very surprising at all. Basically in conformance with the 8.56 +/- 6.88 dB / cm / MHz value.
https://www.mathportal.org/calculators/statistics-calculator...
Yeah I did a (mostly failed) PhD on ultrasonic imaging and found many things that worked in simulations but not in practice. The fancier your imaging algorithm gets the most ill posed it becomes and more sensitive to noise and errors.
Even if you add noise to your simulation , when you go to the real world it will have lots of sources of noise and errors that you didn't model. In this case I suspect aligning the CT scan with the ultrasound probe will be extremely difficult.
Also there's a reason ultrasonographers are so highly paid, and it's mostly used for pregnancies. In normal tissue it kind of sucks as an imaging method. (On an absolute scale; obviously it's amazing technology.)
Eh maybe it will work though. You never know.
It's used for a vast amount of other tissue examinations.
Pregnancies are a minority of ultrasound examinations.
I recently had the idea to start a company that measures specifically properties of the pineal gland, I think people would pay for that. I have no domain expertise whatsoever. If anyone wants to investigate this deeper with me let me know
I don't know how it goes in the US, but AFAIK there needs to be an actual medical reason to expose people to ionizing radiation. That is presuming that you would want to go for the most affordable option of using CT scanner which would set you back for three quarters of a mil approximately in hardware alone. Using an MRI would easily double or triple that, but it would provide better image.
I don't think there's enough rich pineal gland enthusiast to justify the cost, even if the system was truck mounted and mobile and thus hypothetically able to reach wider customer base.
Yeah the focus would be on inventing non-radiation means of scanning, e g further developing Ultrasound Elastography (vibrations) or Diffuse Optical Tomography (near-infrared light). So there's the concept of a thingamajig, a plot device that moves things forward. Focusing on a narrow area gives opportunity for specificity hacks that can then unlock further pivot opportunities. You know start specific and go wider once something works
You want an ultra-low field MRI.
But that'll still be expensive to develop, slow and still potentially lethal if done sufficiently wrong
Thanks for the advice. Potentially, it's not insanely farfetched to assume AI and math (currently doing math) can unlock more precision with less data and invasiveness. While it's at one level physics, stronger algorithms and analysis can maybe reduce the size + cost + danger of the hardware, as well as require less data for more precision. Just a hunch. There are always plenty creative ways to experiment without animal harm as well, just a matter of attention and will to explore. Yeah, safety is super important, and if this sort of scanning can be made better in a fresh way that would unlock a lot. Just like having a 10x cheaper API that does the same job automatically becomes useful in new unforeseen ways.
Why?
Money Oh that sort of why Because it's a spiritual thing, the yuppies who are also slightly hippies would want to see size and health and calcification %, more data sort of like a feedback loop like if you can do crunches and see more pronounced abs in the mirror, why wouldn't you want to meditate and drink and eat healthy and see if stuff changes in the physical state of the brain