Focused Ultrasound
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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.
It's like saying "how can a syringe extract the cytoplasm of a cell?" if you take OP's angle.
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.
Flesh is basically water. Water transmits sound extremely well.
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...
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.
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.
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.
If they indeed need a contact with the object, then obviously that wouldn’t work. But I am not sure why the air molecules couldn’t carry it.
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.
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.
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).
[0] https://www.hcii.cmu.edu/news/software-defined-cooking-using...
Dumping kWs of ultrasound into food would be a bit tricky.
... out of curiosity, why not?
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).
https://www.miele.com/brand/en/revolutionary-excellence-3868...
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..
My immediate reaction was I'm sure there have to be challenges and drawbacks. But hopefully we'll see the tech progress.
My data sources: - https://cdn.fusfoundation.org/2023/02/06115144/Focused-Ultra... - https://www.mayoclinic.org/medical-professionals/urology/new...
https://www.podchaser.com/podcasts/starting-strength-radio-9...
This was in the 1980's.
(Also it's turning out not to be nearly as effective in treating symptoms as deep brain stimulation)
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.
Arguably shock wave lithotripsy, a common method for breaking up kidney stones, could be described as focused ultrasound.
https://www.fusfoundation.org/diseases-and-conditions/kidney...
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.
Edit: similar idea
https://agencyenterprise.github.io/neurotechdevkit/
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.”
https://www.beckman.com/liquid-handlers/echo-acoustic-techno...
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.
Get these down to $50 - https://www.aliexpress.com/w/wholesale-ultrasound-transducer...
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 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.