[HN Gopher] Functional ultrasound through the skull
___________________________________________________________________
Functional ultrasound through the skull
Author : lawrenceyan
Score : 243 points
Date : 2024-11-01 20:52 UTC (7 days ago)
(HTM) web link (brainhack.vercel.app)
(TXT) w3m dump (brainhack.vercel.app)
| _Microft wrote:
| 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.
| bbor wrote:
| 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
| _Microft wrote:
| Modulation is part of the measurement process in that case.
|
| https://en.wikipedia.org/wiki/Lock-in_amplifier
| bbor wrote:
| 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...
| raffihotter wrote:
| 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.
| bbor wrote:
| 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.
| haccount wrote:
| 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.
| tiahura wrote:
| 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?
| haccount wrote:
| Someone skilled in musculoskeletal ultrasound can do it.
|
| But that's a hard skill to develop.
| dr_dshiv wrote:
| "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+
| dr_dshiv wrote:
| "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..."
| levocardia wrote:
| Skulls Unlimited really has their branding on point. I might
| just have to get one for the holidays.
| stavros wrote:
| Just a cool $1800 for a Halloween prop.
| NotMichaelBay wrote:
| For that price, it's gonna somehow have to be included in
| _every_ holiday.
| stavros wrote:
| Skulloween, Skullmas, Skullsgiving...
| klipt wrote:
| I think there's a Tim Burton movie about that.
| KingMob wrote:
| All Skulls' Day, Skullster, Kwanzkull...
| tptacek wrote:
| Reddit claims they do background checks.
| krisoft wrote:
| 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.
| heftig wrote:
| 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.
| eru wrote:
| Well, at least it goes to the user who values it most.
| TeMPOraL wrote:
| s/the public/citizen scientists/ and all is OK now!
| technothrasher wrote:
| 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.
| Ma8ee wrote:
| I'd expect the fleshy parts to leave at least some ashes.
| buran77 wrote:
| 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.
| technothrasher wrote:
| The paperwork said they use beetles, though I suppose
| that they could end up removing the flesh however they
| liked.
| NoNotTheDuo wrote:
| 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!
| trebligdivad wrote:
| '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.
| mkagenius wrote:
| Some say it tastes the same.
| gcanyon wrote:
| ...if you close your eyes...
| lazide wrote:
| To get the same experience, you have to suck it through your
| teeth a bit too.
| robg wrote:
| 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.
| pedalpete wrote:
| 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.
| robg wrote:
| 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.
| finnh wrote:
| 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.
| AlotOfReading wrote:
| As a point of comparison, GNSS works down to about 16 orders of
| magnitude attenuation (dbw).
| edelbitter wrote:
| 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.
| IshKebab wrote:
| 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.
| haccount wrote:
| It's used for a vast amount of other tissue examinations.
|
| Pregnancies are a minority of ultrasound examinations.
| IshKebab wrote:
| Pregnancies are the most common ultrasound examination.
|
| https://www.researchgate.net/figure/Ultrasound-scan-types-
| Th...
| haccount wrote:
| In rural Rwanda, in 2008, for the duration of the study you
| linked after jumping at the first cherry picked example
| that your Google search found, they were the most
| frequently made examination.
|
| But even according to that article, out of the 345
| examinations only 102 were pregnancy scans, making them a
| minority of all scans made.
| IshKebab wrote:
| > after jumping at the first cherry picked example that
| your Google search found
|
| This was not cherry picked. It was the only one I could
| find. Feel free to provide better data since you were so
| sure...
|
| > out of the 345 examinations only 102 were pregnancy
| scans, making them a minority of all scans made.
|
| I knew you would say that. While this is mathematically
| that's clearly not what you were implying by saying it is
| a minority of scans.
|
| I said "it's mostly used for pregnancies". The data
| supports that, not you.
| sfink wrote:
| 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.
| amluto wrote:
| 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.
| sfink wrote:
| Yeah, that's fair. I guess you have to make the ice pick out
| of tofu.
| TeMPOraL wrote:
| 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.
| fragmede wrote:
| 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
| taneq wrote:
| Either way they're not scared of spiders any more! (p < 0.01)
| shermantanktop wrote:
| Maybe this is what _really_ happened to Trotsky.
| tzs wrote:
| > 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...
| finnh wrote:
| JFK's sister Rosemary was lobotomized. Because her dad was an
| asshole, basically.
| Frummy wrote:
| 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
| hn72774 wrote:
| Why?
| Frummy wrote:
| 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
| Caius-Cosades wrote:
| 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.
| Frummy wrote:
| 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
| haccount wrote:
| You want an ultra-low field MRI.
|
| But that'll still be expensive to develop, slow and still
| potentially lethal if done sufficiently wrong
| Frummy wrote:
| 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.
| IndrekR wrote:
| 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.
| thfuran wrote:
| 22 * 1.4 * 10 is not 40.
| IndrekR wrote:
| You are correct. 22*1.4 + 10 is, my bad.
| yoble wrote:
| 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...
| womack wrote:
| 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 :)
| yoble wrote:
| 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)
| tbenst wrote:
| 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.
| neumann wrote:
| Not to mention transcranial doppler ultrasound for measuring
| blood flow.
| raffihotter wrote:
| 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.
| haccount wrote:
| 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))
| azan_ wrote:
| Does viable transcranial doppler for poeple without
| fontanelles actually exist?
| haccount wrote:
| 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.
| kamranjon wrote:
| 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.
| raffihotter wrote:
| Precisely
| westurner wrote:
| 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)
| DoctorOetker wrote:
| 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...
| fuzzythinker wrote:
| In case you didn't scroll to the end, they open sourced their
| code:
|
| https://github.com/brain-hack-2024/transcranial-ultrasound/
| sheepscreek wrote:
| 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?
| haccount wrote:
| 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
| qwerty456127 wrote:
| 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.
| tessierashpool9 wrote:
| breaking up crystalline structures by force usually severely
| damages the tissue. but interesting it is.
| azan_ wrote:
| Is there any evidence that calcifications of pineal gland
| influence sleep?
| haccount wrote:
| 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.
| mrbigbob wrote:
| It mentions using this as a computer interface but wouldnt
| prolonged use eventually open up the blood brain barrier?
| mzs wrote:
| How do you degas a skull in a living mammal and have an unharmed
| animal after?
| raffihotter wrote:
| 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.
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