Rerun: How Ultrasound Works

it a listen. I talked to chief technology officers, chief information officers, chief data officers, these really super smart folks who are shaping the way technology affects business, which means, in turn, it affects us. That show has been fantastic and a lot of work. It's also meant that I've been traveling a ton, so unfortunately, because of that, I didn't really have the time to fully research and write

and prepare an episode ready to go today. So we're going to listen to a classic episode of tech Stuff instead, because I would rather do that than present a rushed, jerky kind of episode where you listen to it and think he didn't even put forth any effort. I always want to give you the best I can, so don't worry. New episodes of tech Stuff are right around the corner. I just didn't have it in me to get one out for today. So we're going to look back on

a classic. This classic episode originally published on January two thousand fourteen, and it's called How Ultrasound Works, And I sat down with Lauren Vogelbaum, who was my co host at the time, to really talk about ultrasonic technology and what it's used for. I hope you guys enjoy it. Take a listen. As it turns out, humans have a certain range of sounds that a typical human can hear. Keeping in mind that different people can hear different ranges.

Some may be able to hear a larger range, some people like me are starting to lose some of that range, and some people are better at lower higher ranges. Sure, um that the average is about twenty to twenty thousand hurts at the low and high end, right, So beyond twenty thousand hurts, like usually significantly beyond twenty thousand hurts at those higher frequencies. We call that ultrasonic. Well, you don't quite get into ultrasonicum right away. I mean, I mean,

you know you've still got a good audible range. I mean, like Bluga whales, for example, can hear up to some like a hundred and twenty thousand hurts, but that is still not ultrasonic. Well, the true ultrasonic that we're looking at, for at least the the technology we'll be talking about today is in the one to one point five million

hurts or mega hurts range. So that's where we're getting to a point where you know, animals are not detecting this kind of sounded a pitch that's much higher than a frequency that's much higher frequency and pitch I'm using almost interchangeably, which is little dis misleading, but you get what I'm saying. So this is a technology it's very much based in some part on something that actual animals

are using. Some animals are using, right yep. And so that's something you probably heard about whenever you've you heard about things like bats or dolphins or whales. They all use echolocation as either a primary way of figuring out what their environments like in the case of bats, or you know, one of the many senses that they rely

upon to explore their environments. Right. Humans also use this in the form of sonar or I mean really technically radar because we're talking about electromagnetic waves and waves, so yeah, but some are specifically is so that is like a

sonic wave. So uh. In fact, sonar was a very important development in our history because radar, as it turns out, was not the best thing to use for underwater because you have a tinuation of those waves and you could never be really sure that the signals you were getting back were really accurate. Sonar is a much more accurate means of determining where something is underwater and whether it's

moving towards you or moving away. We'll talk about more of that as we get further into this podcast, because some of those basic principles really determine some pretty cool uses of ultrasonic technology. Yeah, all of all of that history really builds upon the terrific baby viewing devices that we know and love today. Um, although that is certainly not the only use for ultrasound, as we will also get into. Yeah, I have a favorite one that I'll mention at the end. So, and it's one that I've

talked about before on tech stuff. But that's okay, I don't mind repeating myself. All of you listeners out there who've been around for a while, you know this, so I appreciate that you humor me. I'm glad that you know this about yourself. John. Well, you know it's you reach a certain age, you come to some truths. So first, before I even dive into the history of ultrasonic technology, I have to give a shout out to Dr Jim Sung.

He has a presentation online called the History of Ultrasound and Technological Advances that gave me a lot of insight into the the the discoveries that led to ultrasonic technology. And that's where I drew a lot of this information. So big up to him, really really good, clear, yes, very very simple kind of presentation. I did, you know, augment that with extra research, but it was a great

starting point. So in sevento that's where we have a fellow by the name of Lazaro Spaladzani who was observing the behavior of bats, and as he was observing their behavior, he began to hypothesize what it was that allowed bats to navigate through really dark terrain, being able to avoid things, being able to zero in on prey. And as he thought about it, he came up with this hypothesis that perhaps they were making these very high pitched noises that

were not necessarily within the range of human hearing. You might be able to hear a few squeaks now and then, but that's about it. But that they were also uh, reacting to the echoes of those noises to owne in on things or to avoid obstacles, a right to find out how far away or possibly even how big an obstacle or a predator or a piece of prey would

be away from them. Yeah, because if if you're if you're hearing an echo come back, but it's not nearly as powerful as the sound you put out your your The result might be, oh, that thing is close, but it's also small. If you get a lot of signal back, you're like, Okay, there's something with a lot of surface area that's not too far away, and perhaps I don't want to go in that direction anymore. So he kind of, you know, was the one to propose this hypothesis of echolocation.

Now that's again one of those basic principles that we would build upon to get to ultrasonic technology. In eighteen twenty six, you have Jean Daniel Calladon who was performing a series of experiments using a bell like a church bell. It was actually a church bell that he put underwater. He had a another little lever that had a striker on the end of it to strike the bell. So if you I like to imagine as one of those you remember then the cartoons, the boxing glove that's on

the like accordion type thing stretches out. That's essentially what I imagined this to be. I'm sure that's exactly what it was, not according to the illustration I saw, but those things are never accurate. So anyway, there's this bell that's underneath the water, and he has a striker under

the water as well. And then about ten miles away, according to the illustration, there was a second person in a boat who had a tube that went down into the water and they would essentially put their ear to the tube to listen in like an ear earpiece and earphone, yes, so that they could you would amplify any sounds they could maybe you know, their and their job was to listen for the tone of the bell, and so uh

he would call it on strikes the bell. The person in the other boat writes down exactly when they heard the tone, and the idea here was actually for call it on to show that the sound would travel at a different speed through water that it did through the air. This was just to demonstrate hypothesis that sound traveled at different speeds through different media, something that we know to be true now, right, And and in fact, it travels

faster in water than it does the air. Yeah, So depending upon how tightly packed the molecules are and whatever it is that you're looking at, sound can travel much more quickly through some media than others. And it's because it's a very it's a physical media. It's not an electromagnetic it's actual physical molecules banging into each other. So if they're more tightly packed, they banging into each other

much more quickly. So in that case he was able to show that it indeed does travel at different speeds. Knowing that it travels at different speeds is also very important for the very basics of ultrasonic technology, which is why we're talking about in the first place. So the eighty six, our next date is eighteen eighty. We're just

just scorching through history along. This is where Pierre and Jacques Curi discover the piece of electric effect, which we have talked about quite a few times on tech stuff. All right, this is this winds up being useful in

many applications. But so what is it? Okay, So certain types of material, like for example, quartz crystals have this this particular this particular feature where if you were to apply an electric charge to this material, it would vibrate, or if you apply a mechanical stress to this object, it will then create an electrical charge. It's this weird reaction of electricity and actual kinetic movement energy that you're gonna see between the two things. And in the case

of quartz crystals, it's really really regular. You know, if you know the properties of the quartz crystal, you are good to go. You know that at a certain charge, it's always going to give off the same kind of vibration. So that's why quartz crystals are used in a lot of watches. It's actually the thing that helps keep time right right. It creates the movement in courts watch because

it is so regular or so um, so predictable. Um. It also can it's used to create a spark in the kind of gas lighters that are used for for candles or cigarettes, and also um, you know, it's being talked about for energy harvesting kind of materials that are

being that are in research today right and now. In the case of ultrasonic technology, this is important because the quartz crystals are the things in most ultrasonic transducers that are creating the vibrations that themselves are these high frequency sound waves. And with something as simple as electricity or relatively simple or you know, relatively technologically um possible to put into an instrument. So also they're very important for

picking the signals back up as its out. Well, we'll talk more about that when we get into the actual how it works stuff, but all of this, you know, again plays into it. So nineteen fift you have Paul Langevin who invents the hydrophone, which again very important this in this case, it's essentially a microphone that can go into the water, uh and it relies on the piece of electric effect in order to pick up signals in

the water. What's doing is it's detecting changes in pressure, which are you know, that's what you know, the sound that's moving through the water is changing the actual pressure that the this hydrophone detects. The pressure changes affect the quartz crystals inside the hydrophone, which then generates the electricity, which then goes to another device that again in turns and figure out yeah, or even converted back over into sound so that you can listen to what's going on underneath.

He got the the inspiration to really work on this after something that happened in nineteen twelve, which was when Leonardo DiCaprio sank to the bombo of the ocean and froze to death, or more historically speaking, is when the Titanic sank. I thought, that's what I just said. Well, um, but yeah, yeah. The hydrophone was originally created in order to help detect icebergs and submarines in other large World War One and World War Two. It was really important.

World War two is also really when Sonar I came to play. But before sonar it was really just listening for stuff that you think that should not be there and we need to get out of here. So ninety seven or right thereabouts, a man named Carl Dissick, who was a doctor with the University of Vienna, begins to work on using ultrasound as a means of diagnosing brain tumors. Now, at this time, ultrasonic technology was mostly being used in

those those non applications exactly. But he thought, you know, this could probably tell you more about what's going on inside a person. The human brain is filled with water. Yeah I can, I mean essentially, yeah, I can totally figure out what's going on. Maybe if there's a tumor or something, I can detect it. Now, his approach is very different from what is used today. What we use today is a reflective technique where you send a signal

through a person. It reflects off of various various stuff, will go into more detail in the second half and bounces back and then read out by a receiver in the instrument right exactly, and then a computer kind of puts all that data together to make it meaningful to you. He was actually thinking about setting up two different ultrasonic transducers, one on either side of your noggat and zapping straight

through the brain. So he had a receiver on both sides and a transceiver on both sides, so you're sending signals simultaneously. And the idea was that he thought that the reflection would never be reliable enough for you to be able to have any sort of precise idea what's

going on. Other people said that his particular techniques were um muddy, like it was creating too much noise because you had these two different sources going at it, and so signals right and right, some of it's reflected back, some of it keeps going through, and so there are people who said that the information you would get back from this particular method, uh was you know, not terribly reliable.

Dust because it turns out would go on to be drafted into the Luftwaffe during World War Two and actually would become a doctor treating head wounds for German soldiers. Um. He would continue after the war to really be a proponent of ultrasonic technology being used in the medical field. However, he continued to say that he wanted the transmission effect

was more important than the reflective effect. Uh. And ultimately some researchers at M I I T determined that the method that Dosik was using was creating all this noise I was talking about before, and it really wasn't reliable. So history would end up switching gears, going the different direction and still using ultrasonic technology, but in a different implementation than he did. Yeah, and and absolutely that pioneering kind of going like hey, human bodies are fill of liquid

we can use this technology to look at them too. Yeah, it's pretty it's sound. It's not like it's ionizing radiation. It's not something that's gonna cause you some form of harm. It's it's a physical that. There are a couple of concerns that I've heard here and there about the ultrasonic waves interfering or or creating small bubbles or or various things like right, right, But it's not an ionizing radiation, which is the main difference between that and other imaging.

Definitely better than X rays. Yes, uh so that's when Dr George Ludwig writes a paper describing the use of an ultrasonic device to diagnose skull stones, and in nineteen fifty one, doctors Wild and Neil began publishing studies on ultrasonic characteristics of benign versus malignant breast tumors, not intended as a detection tool actually, but rather as a diagnostic tool once a tumor had been found, so, in other words, to determine whether or not this tumor in fact is

benign or malignant. Right. So, yeah, so this is after we've already established it there is a presence of a tumor nifty eight we got Dr Ian Donald, who I love his technical title, which was Professor of Midwifery at the University of Glasgow. Yeah, he pioneered O B G Y and ultrasound, which is what most of us think about when we think of ultrasound devices in medical fields. I think it's it's for the common lay person. That is the application in which we have seen and heard

it used. Yeah, and it's it's certainly one that oh no, that was kind of sorry, didn't do it this time. So it's it's certainly the thing that we see all the time in movies and television. And you know, it's the sty it's that's the typical was in the hospital. This is the picture of the baby. It's also I mean I just recently saw one because my sisters have a lot of people are born it turns out, Yeah, and it's a very popular way of of imaging before.

I mean, you know, especially and we'll we'll go into this a little bit more later, but you know, it's it's really terrific for figuring out what's going on with a baby without doing any kind of harm to the mother or the baby, right, right, You don't want anything that could potentially disrupt development or cause other complications. Uh. So skipping way ahead because obviously ultrasound by this time had been an established medical technology. It's also was used

in other applications. Will talk a little bit about that later. Uh skipping way ahead, we get to a point where Daniel Liechtenstein pioneers a point of care long ultrasound in the ice see you and says that ultrasound is the real stethoscope. At this stage, we're talking about precision where uh, it was much greater than anything that desn't ever managed.

It was something where you could actually get a really accurate look and in some cases a three dimensional look at what's going on inside a person without it being invasive or terribly invasive, because there are some there are some exceptions we'll talk about, yes, But but this is mostly thanks to advancements in computers in the digitization of ultrasound exactly. So we're gonna talk a lot more about how this actually works, what's really going on with this stuff.

But before we get into that, let's take a quick break to thank our sponsor. Alright, so we're back. Let's talk about how ultrasonic technology actually works. You have to be able to have something that creates an ultrasonic signal, and it has to be able to pick up that ultrasonic signal, and then it has to be able to interpret the signal. So these are these are some important elements that again would only have been possible due to the work of the people we talked about in the

first half. So, uh, your basic, your basic approach here. This is before I get into any of the actual Here's the technical stuff that's going on. Is you've got a device that sends the signal out which then encounters the various tissue barriers in a person's body for ultrasonic medical imaging anyway. So, UH, as it encounters these barriers,

some of those ultrasonic waves are gonna bounce back. So the machine starts to collect the data of the material of the waves that bounce back, the intensity of those waves, and the length of time it took for them to go out and bounce back, give the idea of things like the depth and the nature of the tissue itself. The uh, some of the waves will continue to penetrate into the patient's body and then bounce off other boundaries.

So these boundaries are things like boundaries between liquids and soft tissue, or soft tissue and hard tissue, so and

oregon and bones, that kind of thing. And as the waves go and bounce back, we start to be able to look at that data and determine what kind of tissue it was going through, because because we know that that these sound waves travel at different speeds through different types of Yeah, exactly, So by knowing you know, if you know that sound travels at such and such a speed as it goes through bone, which we know, we do know, I mean, I don't know, if I don't,

we don't personally know. But human kind knows people smarter than you know. You have that thing where you just trust that people smarter than you are working on the problem. In this case, it's true, so not so much working as much as have already completely figured out there charts

that you can look at. So the computer, which we'll talk about in the second, takes all this data in and is able to analyze it and determine which waves were the ones that passed through liquid, which ones were the ones that passed through soft tissue, which ones passed through hard tissue, and then adding all that information together is able to create a picture that's been displayed on

a display. It sends the information to a display so that you get essentially a virtual representation of whatever it is that's there. Typically it's two dimensional, so we'll talk a bit about three D. Uh ultra relatively new development, but it is certainly possible. But your traditional ultrasonic images are two dimensional. So it's kind of like a a side view or top down view, depending upon the angle that's being used and what you are specifically trying to image, right, So, uh,

it's a really cool approach. Now. The parts that are on an ultrasonic machine include the transducer probra, which we've talked a little bit about. Right. This is the device that is sending and receiving the signals. That's got at

least one quartz crystal in it. It may have multiple quartz crystals in it, and in fact, if it does have multiple quarts crystals, you can time the different crystals to file air at you send charges to them at different times because each one has its own independent circuit, and that allows you to quote unquote steer the ultrasonic beam and be able to get a lot more precision about what's going on. UM. But even if it only has one crystal, I can still send and then receive.

So what's happening is you send an electrical charge to the crystal. The crystal vibrates at this incredibly high frequency, which creates this ultrasonic sound like one to one point five mega hurts. And you're talking about possibly millions of these and a millions of pulses in a single second. They go into the body and start to bounce off

of stuff. When the sounds bounce back to the transducer probe, they hit the quartz crystal, which causes the quartz crystal to vibrate, which then causes the electric charge to emanate. So because of that piece of electric effect, it works both ways. The device picks up the electric charges and that's what it's able to use to interpret the actual data that is gathered and sent onto the computer. So the computer, it's a CPU is you know, it's a computer.

It it processes data, crunches numbers, It follows specific rules that have been programmed in that take into account all the basic information that we understand about how sound travels. So that's how it's able to build the actual useful information and generates this image on the screen. Right. Then you also have controls, big surprise there, right, So the controls allow you to do things like you have a

medical practitioner who's called an ultrasonographer. Um. So the ultrasonographer can adjust things like the amplitude of the ultrasonic waves, their frequency, the duration of the pulses that the transducer probe is creating. All right. That the precise frequency of the waves greatly affects the resolution of the resulting image. So this is really important, yes, it really is. It Also it will determine how far the pulses can penetrate.

And on top of all those other things, you also have a storage medium of some sort you want to save this data. Obviously that might be on a disk, or it might be on a you know, just a hard drive or whatever. But it has to have some source storage medium and also probably straight to the cloud to the cloud, which is possible now, uh. And also a printer so that you can print out an image,

especially in the case of babies. I think that it's it's used more often in that case than um, yeah, than than necessary, Like here's how your heart isn't working that I mean, maybe if you want to collect that sort of thing. Maybe you do, I'm not judging, but no, that's exactly. My sister showed me a picture from her ultrasound, so I got to see my niece or nephew early. So that's kind of cool. Um, And now you know the that's that's your basic parts of the ultrasonic device.

Keeping in mind that other you know, more advanced ones may have other elements to them. But that's that's what is kind of the bare requirements for you to have

an ultrasonic medical device. So the only other thing I need to mention is that those those transducer probes also tend to have some sort of absorbent material that will allow it to absorb any echoes that would come from the probe itself, because otherwise you would get right so, because you don't want the crystal to just start vibrating as soon as something bounces off the interior of the probe and comes right back at the crystal. So that's

what the absorbent materials for. It's designed so that it'll try and direct there's actually an acoustic lens that directs the sound towards the patient's body. So that's the basics. But you know that we mentioned already there's a little bit more than just the basic display and imaging. There's this whole three dimensional approach. UM. So first of all, to get the unpleasant parts out. Not all ultrasound is noninvasive, right, UM, it's not always external that there is recent controversy about

this UM in in abortion law. Oh I did not know this, right, Well, it's it's the trans transmational ultrasound in contests. So yeah, because because sometimes UM, for for for many applications, you're looking at something in the body that is not the most easily accessed from the outside. So by by inserting a probe with an ultrasound uh bit on the end into an orifice of one kind or another, UM, you can determine many things about many

important internal organs. Yep. So this is uh you know, it's probably a little less glamorous and comfortable than your typical ultrasound, but it's very important and it's still in the grand scheme of things. Like you know, it's hard to say it's non invasive because you're talking about inserting something into an orifice, but surgery, exploratory surgery way more invasive.

So it's you know, it's either way. There's some approaches now where you can actually create three dimensional images of stuff using ultrasound, and it's pretty much what you would expect. You're you're you're moving the uh, the device, the transducer probe, whether it's internal or external, and you're trying to get multiple different views of whatever it is you're imaging. So in the case of a baby, it would be the baby and you might have to have the patient shift

around or in order to get angles. But yeah, the computer takes in all that data and then creates a three dimensional model of whatever it is it's that it's encountered, and then you can look at that on the screen. So this can be used in all sorts of medical approaches. And uh. One of the things that relies upon is another basic physical property that or universe sound waves, and that we talked about before. Actually it's of any real waves, the Doppler effect, right, the and that's the thing that

that describes how waves change shape when they encounter moving objects. Yeah, so whether you whether the observer is moving or something is moving toward an observer, this affects the way sound sounds to us. That's the way we perceive sound. It also affects the waves themselves. So let's say to that Lauren is uh is screaming at a a single, constant, constant pitch, perfect pitch. But she is just screaming, and I'm running toward her, which is probably what's causing the screaming.

To me, the pitch is going to sound higher in nature than someone who's standing right next to Lauren wondering why she's screaming, And for the person who's running away from Lauren, because that person knows when Lauren screams that's bad news. It sounds like it's a lower pitch. Now. That's because as I'm running towards Lauren, those waves of sun waves coming towards me are actually compressed, right, uh huh and uh. And as you would run away from

a noise, the sound waves lengthen and therefore deepen in pitch. Yeah, So this Doppler effect, if you know what the Doppler effect is, and you're able to measure it properly, you can actually use that to your advantage to determine the location of a moving object, whether it's moving towards you or away. In this case, it's being used to help create that three dimensional model. Hey there, it's Jonathan from here to mention that we're going to take another quick

break about ultrasonic technology and we'll be right back. The Doppler effect method is mainly used for very specific types of imaging. Not all three D imaging is using this. Mostly stuff where you want to measure something really subtle, like blood flow through veins right in in in early experiments with this and intravenous contrast agent would be introduced UM. But then as the method was honed, we've we've become able to detect movement of the blood cells themselves via

change in pitch. That's pretty amazing and it's really useful. I mean it's for diseases that are largely invisible to us, right, oh right, right, anything vascular, you know, finding clots or monitoring flow and risky patients you know, like like after a stroke or a transplanter surgery, um, as well as finding cancerous tumors based on on the way that the blood flow is being affected by the tumor. It's pretty phenomenal.

I mean, I really find the stuff truly amazing. So it really became possible only with the digital revolution of the nineteen eighties, like we were saying earlier. Um, because you know, computers made it possible to to a more precisely shape that ultrasonic beam as we as we mentioned, and and be two to use multiple beams from multiple angles simultaneously, which is that that multi courts action that

we were talking about. And you're talking about an enormous amount of data, so it has to be a powerful computer just to crunch all the numbers properly. So as as those technologies have improved, so have the techniques. So let's talk a little bit about what would be like to go in and have to have an ultrasound procedure done. Because a lot of people I think I've only seen this on television shows or movies. Yeah, I if this isn't complete, t M I UM, I have actually had

an ultrasound done. Um I. I go in for a mammogram every year, and in addition to the mammogram, they also do an ultrasound. All right, So so so tell me if I got any of this wrong, because I have not got in for an ultrasound. So, but I based it off a great article called how Ultrasound Works from how stuff Works dot com. Lug so typically what you have as a patient comes in and removes his or her clothing or whatever clothing would be in the

way specifically of the ultrasound equipment. Sure, because you don't want to pick up the cloth. That wouldn't be useful, right, That would that would be that would corrupt the signal, So you would be that would make things more difficult. Also, it could end up just even if it didn't directly interrupt the signal, it could cause the probe to not be flu flush against the skin, which could cause problems right along those lines. Yeah, so we're getting into the jelly,

aren't we, the mineral oil based jelly. You might wonder if you've ever seen essentially, but but if you've ever seen any other movies where they they're spreading the jelly over a patient's skin before using the ultrasound, you're wondering why it's so that they can seal up any air pockets that would have formed between the transducer probe and the skin of the patient. Right Because, like we've said before, since sound waves move differently through different media, when you've

got air in the way, that's going to cause some problems. Right, So you don't want any air in the way. That's why the jellies used, so in case you were ever wondering,

that's the purpose. Now at that point you have the machine sending through those ultrasonic signals through the patient and picking up the result through the probe through the patient exactly, and then those sounds are reflecting off of the various tissues within the patient coming back through the probe, sending those signals back to the CPU, which then interprets them and sends the signals to display which may or may not be in view of the patient, depending upon what

the procedure is. Uh, and depending on you know, whether the patient is is conscious or whether they want to be looking at it UM and that the tech could at that point mark areas for further investigation UM if needed. Yep. And then that's information is usually recorded onto the storage media so that it could be part of the patient's record. And uh. Then that's the patient is pretty much allowed

to well, they're they're cleaned up the jelly. Yes, yes, they give you a towel, so you clean yourself up and then you put your clothes on and that part of the examination is done. So it's pretty simple. In the grand scheme of things. It's like it's like we said, your basic ultrasonic uh investigation there is non invasive, so that's a good thing. UM. Now, beyond the diagnoses, they're actually looking at using ultrasonic technology to do some treatments.

So it's not just a a tool that's used to check up on someone or get another look at something that may or may not be a problem. In some cases, they're talking about using it to to treat medical conditions, often with nanotechnology. Although one of the coolest ones I read about recently is another diagnostic tool, not a medical treatment tool. It's a nano device that's an a nano sized ultrasonic transducer that can actually image the interior of

a cell, individual living cell. That's awesome. Yeah, it's pretty neat when you get that precise. That's pretty phenomenal. Uh. Yeah. We we talked in a previous episode are are one about gene therapy from December a little bit about one of the other applications UM, which is using using ultrasound waves to UM to push a little kind of nano bubbles of of either medication or genes or whatever you want to get inside a cell over to to where you want them and then also using that ultrasound wave

to burst them appropriate. So that becomes a method of delivery where you're actually maneuvering medication to some specific location. Which that that's seems to be the big approach right now, using ultrasonic or other technologies that are externally applied to get nano based medicines to the right location, because we haven't reached a point yet where we have little like nano sized spaceships that can go straight to where they

need to go and then deliver the medical payload. So a lot of the actual controls are not because we've talked about nano robots before, this idea of a autonomous or even semi just semi autonomous machine that can move through the body. We are not there yet. But what we can do is create nano sized particles that can be manipulated externally through things like ultrasonic frequencies, which is

kind of cool. And you know, speaking of using ultrasonic technology in fun ways, here's a fun way that ultrasonic technology used to be used. So back in the seventies, Lauren, there used to be an era called the nineteen seventies. I do not remember that era because I was not born yet, I was alive during this era. So in the early nineteen seventies, a lot of televisions that were

coming out that had remote controls. Often not always, but often would use ultrasonic frequencies to be the signals that would send it to the television so that you could turn it on or off, or the volume or changing channel or whatever. So you would push a button and often it was just on or off like that was sometimes the only control that you had. Oh sure, I mean we we didn't have channels in those days anyways, as is usually about you know, between you'd have the

channels two through thirteen in the new UHF channel. Anyway, you could turn the set on or off using this device. It would send us ultrasonic frequency that you could not hear, but it would be picked up by the television and

it would do whatever it was supposed to do. The fun thing was that you could actually trigger this accidentally if you were messing around with something else, like I had uh an uncle who talked about how um he thought it was amazing when he accidentally turned off the television because he was carrying um a a like a

container of nuts. And bolts. He was going to do a project, and he tripped and dropped them and they hit the tiled floor and the and some of them must have created this ultrasonic frequency that was the exact same frequency that teld the TV to turn off. And so he was wondering what was wrong with this television And it wasn't until you know, some further experimentation that he figured out, Oh so sound, Chris Pallette, the he used to change the channel or turn this television off

by playing with a slinky. So um, yeah, fun times. Now these days, kids, uh, they're using either infrared or WiFi signals or some crazy thing like that. So you can play with a slinky all day along in front of your television and nothing's going to happen unless you happen to have a infrared slinking or a mischievous sibling with a remote control who is like, wow, look at what you're doing, which could either be really funny or you know, build you up for a terrible letdown later.

Ultrasound can also be used to keep your car windshield clean. Say what seriously, the vibrations bounce, rain, debreathe like bugs, whatever, right off of your of your windshield. Um. There's a high end British car company called McLaren that is looking to bring this tech to consumer cars. UM, assuming that your consumer with you know, over two hundred thousand dollars. That wraps up this classic episode of tech Stuff about

how ultrasound works. It's a fascinating technology, something that it The more I looked into it, the more I was surprised. This idea of using actual frequencies of sound in order to learn more about stuff like what's going on inside us, for example, beyond all the other applications. So it's a phenomenal use of technology and physics, something that I truly find fascinating. I hope you guys enjoyed this retrospective look back at a historic tech Stuff episode. We'll be back

with new episodes next week. Can't wait to talk to you then. If you guys have suggestions for future episodes of tech Stuff, reach out on social media. You can find us on both Facebook and Twitter. We have the handle text stuff h s W and I'll talk to you again really soon. Text Stuff is a production of I Heeart Radio's How Stuff Works. For more podcasts from I Heart Radio, visit the i Heart Radio app, Apple podcasts, or ever you listen to your favorite shows.