Not a secret to the research community... Let me balance the hype with some of the remaining challenges.
Depth is a problem; the deeper you go, the less effective it is. Heat is another issue; you can inadvertently damage nearby tissue. Targeting accuracy is vital, especially near critical structures (think nerves), and we're not at sub-millimeter precision yet. Also, real-time monitoring like MRI-guided FUS is expensive and complicated, and without it you have to guess that you're affecting the right tissue. Great promise, but multiple engineering hurdles to clear before FUS lives up to the hype.
How do you get sub-millimeter precision with ultrasound? At 300KHz, the sound has a wavelength of 1mm. My understanding is that sound with a frequency greater than about 150Khz dissipates after passing through 5cms of air; it must dissipate faster in flesh.
Also, a wavelength of 1mm should give you a resolution of about 4mm, right?
I wish I knew more about the propagation of ultrasound; I'm getting interested in the bats that live around here.
And that’s in air. In water (which is more like what most bodily tissues are made of) the speed of sound is almost five times higher so the wavelength is five times longer.
> My understanding is that sound with a frequency greater than about 150Khz dissipates after passing through 5cms of air; it must dissipate faster in flesh.
Flesh is basically water. Water transmits sound extremely well.
Ultrasonic imaging typically uses frequencies in the low MHz. Like 1-10 MHz.
> Ultrasonic imaging typically uses frequencies in the low MHz. Like 1-10 MHz.
Oh, thank you! So the dissipation is low (because it's water), and the theoretical resolution is 500x greater than my ignorant estimate. I now consider myself better-informed.
[Edit] Now I guess I'm off to see if I can find out what a MHz-grade ultrasound transducer looks like...
You can actually get quite cheap ones now. They make integrated scanners that work with a phone app. Easily under £1k second hand. Maybe close to that new if you shop around.
I wouldn't recommend it though. The only reason we use ultrasound imaging is because it's cheap, easy and completely harmless. As an actual imaging method it's terrible. There's so much speckle you can barely see anything, except in some situations like pregnancy where you have a convenient bag of water around the thing you're looking it.
There's a reason ultrasonographers are well paid - it's really really hard to read an ultrasound.
Yes, I think it is like saying that, but I also think that OP was considering targets less than 4mm in size. The focus of the FUS wave being no smaller than 4mm, very small targets would be larger than the smallest focus.
It's like saying "how can a syringe extract the cytoplasm of a cell?" if you take OP's angle.
Ah I guess in the case of ultrasound, the thing you're trying to do is not nudge or move something, you're literally trying to "ablate" or hit it and only it. That's more like pressing a tiny button with your finger and trying not to touch the outside of the button.
More like saying “how can we draw a 1mm dot with a pencil bigger than 1mm”.
Though not a perfect analogy as you can do stuff with interference patterns to get sub-single wavelength resolution IIUC, I think this is used in silicon wafer photolithography.
I know this is maybe completely out there, but could focused ultrasound be used to heat up food? The current issue with microwaves is that they heat up food very unevenly. I am sure the current cost is quite prohibitive and all. I'm more interested in the science part itself.
I've got a cyclonic inverter microwave, and maybe it's all just hype, but I'm pretty sure it cooks more evenly. I also usually choose a lower power level, which helps a lot. The power level button is highly underrated.
I am not expert, but my understanding of cyclonic inverters is that they are able to lower power output and thus achieving more even cooking. That also implies slower time. I am more interested in precision while retaining the speed. But it's something I looked into myself too.
Seems like the challenge would be heating the right places. How would you know what food to heat more or less?
Also, ultrasonic transducers today, as far as I know, require essentially direct contact to impart energy. You probably don't want to dip something into your leftovers just to heat it.
Impedance mismatch and attenuation. The impedance difference between air and the piezoelectric elements of the transducer is too great - this will cause soundwaves to reflect on contact (and thus never leave the element). If some transducer innovation changed that variable, then attenuation would be the next hurdle.
In general a form of couplant (water, oil, some form of gel, etc) is necessary to eliminate air between the transducer and a material in order for soundwaves to pass.
it feels like (as an uneducated outsider) that a microwave could use some kind of spatial awareness (lidar/sonar/whatever) along with beam-forming and array style transmitters to evenly cook something while sampling temperatures remotely.
the size/shape/cost/performance of such a device is left as an exercise to those better suited to execute that kind of artistry than I am.
I keep thinking about this topic for a couple of years now (hence my question). I wonder if combination of new technology could be made into much more useful microwave, even if the cost was not suitable for personal use (at least initially).
The dream is a microwave with "single button" (start/stop) and a temperature scale (lukewarm, warm, hot, boiling) that consistently heats up food correctly and doing so within very short period of time (below 3 min).
I'll speculate this is phase-controlled microwave cooking.
Microwave power transistors are now cheap at high power levels. If you have an array of such emitters, you can synthesize beams that can deposit energy in small, local volumes. This has been done in actively-scanned military radar for several decades. No moving parts, and beam steering in microseconds.
As a bonus, you could also run a pre-cooking process where you scan the food and map its microwave reflection/absorption properties. This would let you calculate the cooking algorithm based on the particular food item..
Also, do you need MRI-guided or can one just use a much higher frequency ultrasound to see where it's targeting? Regardless, seems like a classic RL problem (presumably some sort of ~ms level cycle of low-power targeting then short burst of power).
Interesting - have a friend going through Prostate Cancer and all docs here in Singapore have suggested surgery + chemo. I noticed in Steve's shared PDF that Prostate Cancer has already crossed the FDA Approval and Reimbursement stage. Anyone had any personal experiences in using HIFU (high intensity focussed ultrasound)? Specifically the stage up to which it is effective over surgery+chemo
You might find this podcast of interest. The guy talks about his experience of the TULSA procedure. They're kind of cynical about the state of prostate treatment in general but seem keen on this procedure.
When I was a kid, I fell on my wrist. It healed up badly and formed a lot of calcium deposits around the bones. I couldn't bend my wrist backwards more than a couple degrees and it was painful. Went to a PT who used ultrasound treatments and stretching to break down the deposits, which freed my wrist up.
Dealing acoustically with something different from the surrounding material (calcium deposits) is a lot easier than focusing on tissues with roughly the acoustic properties of water among other tissues with the acoustic properties of water - in the former case the stuff can distinguish itself w.r.t. application of the waves, the latter requires focusing to come "from the outside."
I remember randomly visiting a lecture of one of my professors that specializes in high performance computing, he was showing off the research they do and it was regarding computing the necessary "parameters" for this. Apparently calculating the parameters for a single patient to focus just the right spot and not damage anything is a task that takes several hours on a supercomputer. This might've been like 5 years ago.
From the brain side, those of us who remember the pallidotomy and thalamotomy days, the "noninvasive" part is a marketing misnomer. It's invasive (it's a lesioning/ablation therapy); it just doesn't require a pallidotomy. But it's a shockingly effective tactic; there's a steady stream of patients rolling in the office with mild symptoms who are willingly requesting to have a hole burned in their head.
(Also it's turning out not to be nearly as effective in treating symptoms as deep brain stimulation)
Meh? It’s been on the French health market for at least two decades (Ablatherm).
It’s effective for people that wouldn’t bear anesthesia but it comes with some limitations.
It can’t be used when there are bones, lungs or non-uniform propagation medium in front of the target. And while the tissues are burnt their mechanical properties are evolving and deflecting the beam. The cavitation due to negative alternance of pressure waves puts a limit on the power. Perfusion can take the heat away, etc…
It’s probably not widely used because conventional surgery is often more practical.
Lithotripsy is pretty limited, I think the preference in most cases is to use ureteroscopy (using holmium laser ablation to break up stones).. but as someone who's had this, I can tell you it's no fun- any progress would be welcome.
If you are interested in learning more about focused ultrasound there is a great python toolbox that allows you generate simulations, change parameters, visualize results, etc.
From the repo “The Neurotech Development Kit (NDK) is an open-source, community-driven software library designed to lower the barrier of entry to the next generation of neurotechnology for current researchers and companies. It also enables software developers without access to hardware and human subjects to solve open problems in the field. The initial release of NDK provides support for transcranial focused ultrasound stimulation, along with comprehensive documentation, API flexibility, and 2D/3D visualizations. Future areas of interest may include photoacoustic and optical whole-brain imaging.”
I’ve always wondered what happened to Steve Jurvetson. He laid low for a while after resigning from the Tesla Board of Directors. I see he is active on Twitter/X now.
The Tricorder moonshot was a stupid waste of time with their impossible stupid rules.
A cheap conventual ultrasound in a stick would be a tricorder moment. Hook in a mobile phone and 3D analyzing humans or pets or livestock or many inanimate things becomes software.
This is cool and all, but unless you get the tech out of their hands it'll go nowhere for decades. Just like we've stagnated with conventual ultra sound.
The cost needs to be smashed down. It shouldn't take a moonshot. This is old tech that's not hugely complicated.
Not completely objecting to this idea, but even in ideal scenarios with high-tech hardware and specialized setup, getting useful US image quality can be non-trivial and requires training and expertise. I can conceivably see that these are to some extent technical limitations that can be overcome for some level of mass-adoption. However, I don't see what use cases you have in mind that don't require a doctor for interpretation anyway (in which case having a professional device and the required expertise present in the facility is much simpler and cheaper than putting it in the hands of every patient).
But also, particularly for pets I believe anything with a non-negligible amount of fur or similar (i.e. anything that is not just bare skin) will be fundamentally impossible to achieve good enough acoustic coupling for. Unless you also sell shaving equipment with it. Anything with bone in the way (e.g. a ribcage with gaps smaller than a human one) is also more or less out.
For inanimate objects I really wonder what use cases you have in mind. Acoustic properties (and coupling) are even more of a variable there...
> The cost needs to be smashed down. It shouldn't take a moonshot. This is old tech that's not hugely complicated.
The tech is not the problem, the certifications are. It's incredibly expensive and onerous to bring new medical device designs to market, and for good reasons - if it were easier, you'd get even more quackery than you already have now (e.g. homeopathy, penis enhancement pills, "nutritional" supplements).
The same is true for airplanes. Your run-off-the-mill Cessna? Its design dates back to the 50s. Almost all of GA still runs with fucking lead in the fuel because it took the FAA over 12 years to get it certified, and even in the US it is estimated to take until 2026 (!) until G100UL is widely available. Europe doesn't even have a timeframe.
Depth is a problem; the deeper you go, the less effective it is. Heat is another issue; you can inadvertently damage nearby tissue. Targeting accuracy is vital, especially near critical structures (think nerves), and we're not at sub-millimeter precision yet. Also, real-time monitoring like MRI-guided FUS is expensive and complicated, and without it you have to guess that you're affecting the right tissue. Great promise, but multiple engineering hurdles to clear before FUS lives up to the hype.