excited to have Dr. Chris Visco with us today. Dr. Visco thank you for joining us. Well thank you for having me. This is exciting that we can do this and I appreciate the invite. It's nice to be with you all today. It looks like we've got about 91 participants. That's terrific and it's it's really nice to see everybody here. So I'm gonna go ahead and get started. I'm just pulling up this talk today on ultrasound. Now when is the next time you're going to be able to ultrasound a patient considering where we are right now in the grand scheme of things? Tough to say, right? This is a great opportunity for everyone to take a moment to tune up their ultrasound knowledge, to refresh their memory on physics and how things should look with ultrasound. And if you're so fortunate to be able to go ahead and have access to an ultrasound machine, you could always do a little scanning while you're self-isolating. Just you and that ultrasound machine. Make sure you do a deep clean when you're done. So again my name is Chris Visco. I've been doing ultrasound for a little while now. And I'm the Residency Program Director for Physical Medicine Rehabilitation at New York Presbyterian Hospital, Columbia and Cornell. I'm also the Sports Medicine Fellowship Director at Columbia, Cornell and Queens Sports Medicine Program. And I'm going to dive into a little bit of physics here. As a disclosure, I do a little bit of speaking for a couple other groups as well, so you can see. The objectives here are to go through a couple fundamentals, a little bit of history, a little bit of physics. We'll talk about how to optimize images and how to scan specific body areas and specifically how to scan specific tissue structures and what you might expect. So briefly, by way of history, ultrasound has been around for some time. It's been utilized in war efforts in the most practical aspect in the early 1900s. And at that time it was used for echolocation and described on subs as hydrophone before that. Described in its first clinical application in intestinal use and then ultimately in cardiac use. One of the first musculoskeletal applications actually happened in the 50s when Dusik described its use for looking at the articular and periarticular tissue. The AIUM, as we know it, was based on utilizing therapeutic ultrasound and was originally founded by physiatrists in 1951. The first B-mode scan, so everything before the 70s was A-mode, and A-mode was essentially just a graph. B-mode is what you use now, what you see. It's that grayscale image and that was first described in the 70s, first utilized in obstetrics and radiologists. It's essentially almost unrecognizable to what we have today. If you look at the kinds of machines that they were using back then, there were these sort of little monstrosities relative to what we have in terms of computing power. And the early adopters were those in emergency medicine for clinical educational use, where they really developed the first fellowships in ultrasound. And what we see now is we've got all types of applications in education and a real expansion across. You'll see this if you look back a few years to the British Journal of Sports Medicine and there have been some subsequent publications that you can see on curricular recommendations. This is when it really sort of got kicked off in sports applications. And of course most people think of when they think of ultrasound in the clinical practice, they think about now, they think about ultrasound guided procedures. And really this goes hand-in-hand with some of the understanding of the diagnostic and visualization on ultrasound. So mainly what I'd like to conquer today is what does tissue look like? Because understanding what ultrasound looks like helps you become better at understanding anatomy. And here we are with the anatomy students at Columbia. This is before we got the Sim Center and beautiful new space. This was at the old anatomy lab. And we had a lot of fun. I had probably about a half an inch to an inch more of a hairline. And you know we we killed it because we took an approach, a fundamental basic concept of we want to teach people how to be better anatomists in anatomy. Not how to do ultrasound in anatomy, but how to be better anatomists. How do you take someone and make them a better doctor? How do you take someone and make them a better cardiologist? A better at emergency medicine? And a better physiatrist? And that ultimately is how we introduce ultrasound into our curriculum now in residency and how to be a better sports medicine fellowship fellow in our sports medicine fellowship. So the way ultrasound works, brace yourself for a little physics here, is by the reverse piezoelectric effect. Now some of you may have heard this lecture, but this is a this is ultrasound 101. Because the electrical current comes down in a pulsed fashion through that wire and hits a piezoelectric cell, which is a thin crystal at the tip of the electrode. That reverberates, that crystal reverberates creating a sound wave, an ultrasound wave. And that sound wave is so defined as ultrasound because it's higher than 20,000 Hertz. 20,000 Hertz being the upper limit of human auditory condition. You can't hear anything over 20,000 Hertz. But the realm in which we use diagnostic ultrasound is usually 1 megahertz and greater. And most of your machines now are using anywhere from 3 to 33 megahertz. That's what defines ultrasound, being that high. So that signal, those sound waves, then because of that reverse piezoelectric effect converting electrical to sound, those sound waves are transmitted down to the tissue. They bounce in a pulsed fashion. It's not continuous, it's pulsed. Those sound waves bounce down into the tissue and then off of the tissue structures. Now tissue is not uniform, unlike a glass of water, which is uniform. Tissue has varying degrees of density in it. And accordingly those sound waves will bounce with varying degrees of intensity back to the transducer. Those intensity levels will, based on how long they took to come back and how strong they are when they come back to that crystal, will reverberate the crystal at different times. That will then send an electrical signal in a pulsed fashion back up the cord and that will then convert it into an image after a grayscale is assigned. That is how you get V-mode. So this is what you end up with on the screen. You get something that looks like this. Now what we're looking at is a grayscale image, a B-mode Doppler image. This is a B-mode Doppler image of the front of someone's shoulder. So what we're looking at here, as the transducer comes down, by the way, look at my hand and wrist there. This is a full contact sport, so you're going to get gel on you. You're going to get gel everywhere. Just be prepared for that. It's kind of hard to avoid that with ultrasound. But what we're looking at in this particular image, this ultrasound is oriented, creating a plane of ultrasound waves that's coming out from the transducer into the tissue and creating a anatomic axial cut through the body, if you could imagine that. That anatomic axial cut is penetrating through that tissue in the front of the shoulder and coming back and giving us this. So what are we looking at? Well, at the very top of the screen, that's where the skin and the dermis is, and that's where the subcutaneous tissue is. You can see the very top of the screen. I'm going to darken it up a little bit here. As I darken it up, you can see just underneath that is a brighter line. So if you take away that darker area altogether, you really see that bright line near the top. That's the deep fascia. The deep fascia is adherent to the muscle underneath it. The deep fascia is bright because it's dense. The deep fascia is holding that and enveloping that musculature and flowing from the deltoid, in this case the anterior deltoid, through the remainder of the upper arm and is in continuity with the deep fascia elsewhere in the body. So for a moment, let's darken up that deltoid. We see what that deltoid looks like on the other side of that deep fascia, on the deeper side. And then if we go just deeper to that yet, we start seeing an arc, which is a bright arc, traversing the screen here. That's the bursa. This bright area is the deltoid portion of the sub-deltoid bursa. This bright line is the deeper portion of the bursa. And in between is the bursal fluid or the potential space in the bursa. So what you have is you have this very interesting arrangement of bright, dark, bright. Now if you were to dissect this out, what you'd find is you would see very minimal difference between this layer and the deltoid. You'd be able to peel it off, and that's what happens in a bursectomy. But it's very easy to cut right through this in a cadaver and never realize that this fascial layer, this bursal lining is here. Why is it bright? Why is this a different echogenic texture than the deltoid? Because that surface of the deltoid is impregnated with fat, with synovial tissue, and is much smoother in almost sort of an epidermal type of aligning on that surface of the bursa as it lines up against the adjacent surface. What is the dark stuff in the middle? What is that made of? It's made of hyaluronic acid and other introversal constituents, but mainly hyaluronic acid. So then we take that away. We take the deltoid away, and we just appreciate the bursa for a moment. So we have deep fascia up here, we have the deltoid, we have the bursa. What else do we have left? Bone. This bright line down here is the surface of the bone. What bone is this? It's the humerus. What surface is this? It's anterior on the shoulder. It's the anterior portion of the humeral head. It is the lesser tuberosity. So think for a moment now. The ultrasound waves are hitting this bright, bright area, but we see these echoes down here. Isn't this something? Aren't I seeing something underneath that? No. All of that is artifact. Everything deep to bone cannot be seen on ultrasound. Accordingly, when you see these kinds of things, you need to put it out of your mind. What you're seeing there is a reflection in part of the surface. You're seeing reverberation, and you're also seeing a reflection of the tissue that's just superficial to it. It almost acts like a little mirror because of its density. So what's left? We've got a bright line, deep fascia. We've got a bright arc here, bursa. We've got a bright line here, which is the bone. What's left is the tendon. And this is the tendon of the rotator cuff. A lot of times we want to jump right to the rotator cuff to look at the rotator cuff and the shoulder when we're examining it, but it's important to go through this methodologically because that will allow you to take a moment to make sure you've counted down all of the different tissue structures that lead you to the rotator cuff. If you don't, you may miss a full thickness, complete, retracted rotator cuff tear, which will then be out of the visual field. If it's out of the visual field in totality, it's not that you see a hole here. It's that you see nothing. You just see bursal tissue, sometimes bursal fluid, and that bursal tissue may be thickened. Accordingly, it's very easy to miss a rotator cuff tear when the rotator cuff is completely out of the field. So take a moment to count these things down and observe that tissue. Right. So here we are. What do we have here? It's the anterior anatomic axial plane across the shoulder. This is the subscapularis. Okay. This is the muscle of the subscapularis down over here. Here's the tendinous portion. You can see the intercalated nature of the tendon as these bright lines don't go from the surface of the bone all the way to the muscle or the myotendon. They sort of weave in and out of each other. And then on the deepest portion where that tendon is attached, you see this dark area as well. That is a fibrocartilaginous interface between the tendon and the periosteum because the tendon doesn't just go straight into periosteum. It has an interface. It has a little bit of a cartilaginous interface where you see progenitor cells living. And so appreciate all of these things as you're looking at that. Understanding the anatomy makes you a better physiatrist and understanding ultrasound and what you see makes you a better physiatrist. Let's take that away. Let's take that tendon away. Now, what do we see? Bright line, bright line, bright line, deep fascia, bursal surface, bone. You're going to see this anytime you're looking at the tendon. It looks similar over the hip. You're going to see this anytime you need to count down to identify where these tissue planes may be in the body. So take a moment to look through that. Take a moment to bring into your mind's eye the cartoon picture of what you may be seeing and take a moment to really identify subcutaneous tissue, fascia, muscle, bursa, tendon, periosteum, and bone. When you do that, then you start to really see. It becomes clear. What needs to become clear in ultrasound is the signal. And the signal is the thing that you're after. This is the image. Everything else is noise. Now, high signal to noise ratio gets you better. It's better when the machine is tweaked to optimize. The structures are contrasting. There's minimal absorption of the overlying tissue. You have a lot of signal and low noise, but you get a lot of noise when you have scattering or absorption of waves. And I'm going to talk about that now. The physics of ultrasound are such that as the piezoelectric cell is reverberating and so those ultrasound waves are traveling down to the tissue, they're turned into heat. And that conversion of ultrasound into heat creates absorption of the ultrasound and attenuation ultimately of the image. It attenuates the signal because it decreases the intensity, power, and amplitude as you get some conversion of those sound waves into heat. So for instance, what we're looking at here is plantar fascia. What do we see? Well, okay. Start from the top. We see the skin, subcutaneous tissue. In this case, the fat pad of the heels is the predominant thing that we're seeing. There's no overlying muscle on the bottom of the foot. But what we do see is plantar fascia sitting here. We see a calcaneus and we see the bone, which is bright. But everything looks gray. It's kind of like grayed out, sort of fuzzy. Why? Because of attenuation. Because of the attenuation of the fat pad and attenuation of the callus on the bottom of the foot. Refraction also messes you up a little bit because waves bend as they pass through different tissue densities. In this case, we're looking at two different tissue densities, air and water. And the interface here creates some refraction. So what it looks like in this image is that the straw is broken or that the straw isn't continuous. And that's only because waves angulate through the water at a different angle than through the air, creating this refraction. We see this on ultrasound very similarly. In this case, we're scanning the front of the hip. This is the front of the femoral head. We're looking at the femoral artery. Well, the psoas tendon is sitting just deep to it over the capsule. At the edge of the femoral artery, which has a low tissue density inside of it, the blood, relative to the higher tissue density, the surrounding tissue, that creates a refractile line. This refractile shadowing, as it's called in this case, is traversing down right through the center of that psoas tendon. So if you were just looking at the psoas tendon without paying mind to the fact that there may be other tissue densities creating refractile artifacts in the image, you may miss the fact that there's a hypoechoic line in the center of that psoas from the artifact. You may inadvertently call that tendinopathy of the psoas tendon. So don't make that rookie mistake. Pay attention to the physics and pay attention to what's there. Reflection is very similar. Because you have two different tissue densities, in this case, reflection is causing a bouncing of the waves off of the surface of that plane of tissue, just like light bounces off of the surface of a body of water, like a lake. For instance, the ultrasound waves are coming down from the surface here. As they do, we're looking at the front of the hip now. We're passing through the iliacus and in the front of the... I'm sorry. So we're looking at the shoulder here. I've changed up my images. We're looking at the front of the shoulder. So this is the anterior deltoid. We're looking at the bursa anteriorly, and we're scanning the anterior humeral head. What do we see? Well, we see a bright line on the surface of the cartilage. Why is that bright? That's bright in this case because we're looking at a small tear on the undersurface of the tendon. In that tear is a bit of fluid, and that fluid, which is a low tissue density relative to the higher tissue density of the hyaline cartilage, creates this cartilage interface sign, which is reflection of the ultrasound waves off of this interface back to the transducer. It creates a very bright area because of that interface of two different fluid densities. So everything is relative on ultrasound, and depending on what happens to the sound, you'll describe it differently. It will be hypoechoic if it's dark. It will be hyperechoic if it's bright, and everything in between gives us shades of gray, but it's important to recognize that you're describing it based on the field of view. So if things are bright in the field of view, for instance, in this case, we would describe the tendon as being relatively hyperechoic to the deltoid. We would describe the bone, the bony surface on the facets of the greater tuberosity here we would describe them as being relatively hyperechoic to the tendon. We would describe the muscle as being hypoechoic to the tendon. And so you can describe things within the field of view. What you can't do is describe that biceps tendon as being relatively hyper or hypoechoic to the psoas tendon elsewhere in the body. It's not within the field of view. So describe and use your hyper and hypoechogenic tissue structures within your field of view and do so responsibly. All of these things contribute to different things you may see on the screen. So absorption is when you have less signal coming back because you have conversion to heat. Reflection is a bouncing of the signal away from the transducer in a way, or a bouncing of the signal back to the transducer and sometimes away depending on the angle. And refraction is that angulation depending on the tissue density. Scatter is what you use to term anything that's bouncing in a direction away from the transducer. These terms are important, particularly if you decide to sit for an ultrasound test with the air DMS. And the process of identifying that a structure has different, appears differently at different angles is described as anisotropy. So this, for instance, can be demonstrated when you're describing a very dense tissue structure nicely. So this was one of the first ultrasound machines that I learned on. You can see everything in the screen looks sort of pixelated and granular, but in there buried somewhere is the patellar tendon in transverse. You can see the transducer is oriented in a perpendicular arrangement to the patellar tendon. And as I toggle that transducer down, all of a sudden the patellar tendon becomes very hypoechoic. It's not hypoechoic because there's something pathologic about the tendon. It's hypoechoic because the angle of the beam is such that as the beam is hitting the very densely packed tendon, it's now bouncing away from the transducer and it's not bouncing back to the transducer. So the machine thinks that there's nothing there or there's little tissue there. And accordingly, it looks dark. That process of something looking different at different angles is described as anisotropy. Tendon has a high propensity to anisotropy because of its tight packed regular nature, similar to ligaments. Nerve lets so because it's more interspersed in terms of tissue density and muscle much less so, which you may see some. Let's talk about how to optimize your machine. There's a two-step process here. First, you want to pick your transducer. Second, you want to set up your, so first you want to pick your ergonomics. Second, you want to pick your transducer. The real key here is, and this image came from the AIUM is they're giving a nice little lecture on how to set up an ergonomic evaluation. You know, this is a great way to go ahead and give yourself a rotator cuff tear in the cervical or dick while you're evaluating somebody's foot. Don't do this. You want to optimize your position so you decrease your risk of injury. And you want to set up your environment so that as different sized patients come in, different bodies come in, you can adjust and you can be ready for that. Here's a couple of tips. Number one, bring it in close. Bring the patient in close. Bring the transducer close to you so that you're not holding the transducer all the way at arm's length. Bring the machine in close so you can operate the interface on the machine without having to reach repeatedly. You want the screen about two feet from your eyes. Now, if you haven't figured that one out, that's the case when you're working on a computer no matter where you are using ergonomics. So it should be about at eye level, wherever your seat is. And that screen should be about two feet away. Dim the lighting. If you don't, you're going to be straining your eyes to see those tissue structures that are on the lower end of the pixel distribution on your screen. So dim that lighting, just like you would in a radiology reading room. And don't use gloves. Now, when I say that, I mean don't use gloves in areas where you would not normally use gloves. And I think the idea of not using gloves in a post-COVID era is kind of out the window because we're probably going to be using gloves a lot more. But suffice it to say this, if you would not use gloves for any other reason, routine reason, don't use them. If you would use gloves because of whatever regulatory environment, maybe you're examining a patient in an area where you would normally routinely use gloves to examine that patient, for instance, around the genitals and so forth, you want to be able to use gloves for that. But otherwise, if you cannot use gloves, that will help you because you'll decrease the amount of grip that you'll have to use on the transducer. With gloves, it decreases the coefficient of friction a bit and you go ahead and you have to grip a little bit harder to maintain control of that transducer. Manager cord, that doesn't necessarily mean looping it around the back of your neck. There's mixed messages about that. Most people recommend not doing that because it does pull you forward a little bit. If you're going to put it around your neck, just put it around once, not twice. If you're going to use it, you can also wrap it around your wrist. Another option is to go ahead and pin a little bit of the cord between your knee and the table. That will make sure that the cord that's near the floor is not pulling the transducer down out of your hand. At the very least, make sure you're not running over the cord, as you can see in this image here. And most machines have little hooks and doodads on them to help you stabilize the cord and use those, look for them and use them. So there you are. All of a sudden, now you're sitting in front of the machine. You've got your patient nearby. You can reach everything. And what do you reach for? Do you reach for which transducer to reach for? Now, for all intents and purposes, for nearly every physiatric approach that you will take, regardless of the size of the patient, regardless of the tissue structure that you'll be examining, you should almost invariably pick up your linear transducer first. Here's why. Pick up your linear transducer because it gets you the best resolution. The linear transducer has the higher end of the frequency range. You can see on the image that I have here that this linear transducer is L12 to three. So it tops out at 12 megahertz. Linear transducers now are commonly available up to 18 megahertz. Uncommonly, you can also get some up to 20 in the 20s. I've worked with transducers in the mid 30s now. But what happens as you go higher and higher on your frequency range? You get less penetration. Because those high frequencies mean that you need to use smaller waves. You know why? Because hertz, don't feel bad about it. It's been a while since you've had to think about hertz. It's been a while since you've had physics. Hertz means per second. So if you have one hertz, that's happening one per second. If you have 10 hertz, it's something that's happening 10 times per second. So 20,000 hertz are 20,000 sound waves per second. Anything above that is ultrasound. One megahertz is one million per second. Now the difference between three megahertz and 30 megahertz is a tenfold difference, which means that you'll have to put 10 times the number of waves in every second in order to get that frequency of the transducer. Those waves then need to be smaller. The benefit of having small waves is that those teeny tiny waves can get in between teeny tiny structures. It helps you resolve things that are small. The problem with teeny tiny waves is they're obliterated by tissue. They convert into heat, they bounce into each other, they bounce into everything else, and it's difficult to achieve any real penetration with those higher frequencies. That's why it's just physics that's limiting you with those sound waves. On the lower end of the frequency, which this linear transducer still has, down to five megahertz, three megahertz, you can lower your frequency on that transducer and still get an ability to see deeper structures with the linear transducer. But you always wanna stay at the highest end of the frequency to get the best resolution to start. If you start at the lower end of the frequency, you may never make your way back up to the higher end to know what you may have missed in that higher resolution area. Start there. Curve linears are particularly helpful when you're scanning shoulders and hips. They're particularly helpful when you're doing procedures because you can use the angle of the curve. Curve linear transducers appear on the screen like a fan of sound waves. Now, both linear and curve linear fan out, but linear just appears like a column of sound waves. Now, how should you hold the transducer, right? Things open up, you're back from COVID. You get to sit with your outpatient doc again. Get into the ultrasound. They say, well, go ahead, get in there, start and start scanning and I'll be in in a minute. What do you do? Well, what you wanna do is look at that transducer and you want to grab that transducer by the neck. If you look, there's a tail on that thing. That's at the end. The neck is at the front. That's where you wanna do it. It's like walking a dog. You wanna hold it. You wanna keep around the collar, harness it, put a harness on it, grab it by the head, neck, top of the body. Don't hold it by the tail. You'd never walk a dog by the tail. That would be super embarrassing. You wanna do all these things, rotate, toggle, wag, heel, toe. Here's what I mean. When you grab that transducer and you're holding it, there's different ways. So there's different grips. You know this, you're physiatrists. There's pincer grips, right? Here's a little small footprint, curve linear transducer. Here's another pincer grip, wide base pincer grip, right? Look at that, it's palmar grip. Difference between this and this. This gives you more flexibility in terms of quickly manipulating the transducer in real time. This gives you better ergonomics, less fatigue, but there's a compromise. You get less quick manipulations of the transducer. If you know you're gonna be someplace for a long time, go ahead and drop that transducer into your palm, into a palmar grip. It lasts a lot longer, you won't fatigue. This one, you're more likely to develop an occupational injury, but you'll get a better picture. So there's your compromise. Here's what I mean. Rotate, left image here. Rotate is turning that transducer on its long axis in such a way that you can go from a transverse to long view in this case of that median nerve. Looking at the wrist. Tilt, it's like also called toggling. Tilting and toggling are like turning a light switch. You're taking the tail of that transducer and you're bringing it up or down. This helps to resolve anisotropy, especially around areas that are turning or curving, like in this case, the median nerve. Heel-toe, the long axis of the transducer can be similarly brought deeper or more superficial, and that's called heel-toeing. Like that long axis is a foot and you're driving the heel down or you're driving the toe down a little bit further. And then once you start to do that and you start to identify your tissue structures, that's when you want to start identifying what you need to change on your instrument, on the actual machine itself. And the three things that are the most important for you to change are the depth, frequency, and focus. You'll see them in different spots. On every machine, it's in a slightly different area, but what I can tell you is this. The gain, none of which I just mentioned, is usually the thing that's closest to you. The gain is usually the thing that's the big dial right in front of you. That's what is nice when you brighten, when the room is not dim enough, you can brighten the gain, but you want to play with the depth, the focal zone, and the frequency first before you touch that big knob of the gain, before you touch the gain, play with the depth. Not every, some machines don't have a focal zone because that's adjusted with the depth, but if you do have a focal zone, you'll recognize it because it's off on the side. On the right side of the screen here, you see two arrows up and down. That's where the focal zone is. You also may see the depth labeled on the right side of the screen by hash marks, or you may see it on the left side of the screen labeled in the upper left corner, which is highlighted here as two centimeters. Now, you want to just write, not too deep, not too shallow, Goldilocks style. You want to make that center of the screen work for you. So put whatever tissue structure that you're looking at. I like the little honeycomb here, it makes me think of nerves. And make that, put that in the center of the screen, not too high, not too low. The frequency we talked about is transducer dependent, but is adjustable by software. So utilize your adjustments on the actual ultrasound machine itself to turn the frequency up and down on that transducer that you're using. Each transducer will have a different, will have different frequency settings and a different amount of penetration or resolution that you can get from it. You don't know who is last at the machine or what the presets are on each individual machine. So I'd recommend you go ahead and adjust the frequency regardless of what you, what appears good or not. It might look like a great image on the screen, go ahead and change it, adjust the frequency up and down and give yourself something even better potentially. If you want more penetration, go to a lower frequency. And if you really need to, go ahead and swap your transducer. Focal zone. Focal zone is so interesting. The focal zone is where the ultrasound beam narrows even further. So a beam of ultrasound is very thin. It's about, it's less than a millimeter. It's about 0.9 to 0.5 millimeters that each manufacturer has a proprietary, knows this, but it's proprietary for whatever reason. But the focal zone is where it narrows that even a bit further. And as we discussed, little tiny things can penetrate between little tiny structures very nicely. So it gives you a better resolution in that one particular area where the ultrasound beam is narrowed even a bit further. So what we can see on an image like this, if we're scanning at 10 megahertz and we've got some tissue planes, forget where we are in the body here, but you can see the, on the right side of the screen, those focal zones indicated by the arrows. And if we wanted to see the bottom most part of the picture, but we're sort of maxed out on our depth here because we're at bone at the bottom part of our picture. What we may wish to do is identify that area that we want to see and drop the focal zones down to it. Look what happens when you drop the focal zones down to that area, it becomes more obvious. The lines become crisper and cleaner down at the deepest portion of that image. Only thing that was changed here is dropping the focal zone deeper on the image. Here's what you want to avoid. Focal zone in no man's land. Depth is too deep. We're looking at something very superficial. Frequency is at some sort of general setting and should be at a resolution setting, which is R, which would be the higher end of the frequency range. Use higher frequencies for superficial structures. Adjust focal zones and depths so that you're maximizing what's in the middle of the screen and utilizing your focal zones to the best of their ability. Use your machine and your settings. Gain and time gain compensation. So you can touch the gain. Don't be afraid to make it brighter or darker, but don't make that the first thing that you change on a machine. Adjust the depth, focus and frequency first. Then if it still looks dark, adjust the gain up. If you max out the gain, what it does is it takes all the top level pixels and it makes them all bright. And you lose your ability to discern in the top 20, 10, 20% of pixels. Time gain compensation. People get really freaked out in this because they're like, oh, I don't know what this is. It's a whole bunch of lines. Well, just imagine that each one of these horizontal lines corresponds to a different horizontal line on your screen. The top line corresponds to the top of your screen, the bottom to the bottom part of your screen. This changes the gain based on that part of the screen. So why does it have such a fancy name, time gain compensation? Well, think for a moment. Back in the day before software could compensate for temporal reasons why things look brighter, you would have a really bright area near the top of the screen because the ultrasound waves would get there more quickly. It takes a lot longer for an ultrasound wave to go all the way to the bottom of the screen and come all the way back. And that needed some level of compensation. And that was called the time gain compensation. So you would compensate for time by adjusting the gain near the bottom of the screen and making it brighter. Typically, we don't really need to use this anymore. We don't really need to even touch these because the only time you need to touch these is when somebody has been using the machine before you and throws their backpack on it and makes them all go cockeyed. And then you just need to put them back in the center of the screen again. So here's a couple more points on optimization. I'm keeping my eye on the time. I have lots to talk about. So you can go through this at another point, but consider harmonics. Tissue harmonics are very helpful. They allow you to use smaller frequencies to ride on larger frequencies at harmonic resonance to then visualize deeper structures with better resolution. Zoom allows you to look at a selected area on the screen, but it often will stretch the pixel so you don't have the truest possible image. And beam steering or trapezoidal imaging can be helpful, especially when you're using a linear transducer and you want to use the edges of the screen to visualize either a needle coming in or to maximize your diagnostic imaging on the outer margins of the image. Let's talk a little bit about motions. Power Doppler, color Doppler, right? So we've got all this Doppler and we know Doppler effect, right? So the Doppler effect is such that an observer, depending on where the observer is, will observe different frequencies based on the stretching or the compression of sound waves, even if that sound wave is given off at the same frequency from its source. So for in this case, it's a car engine is giving off a sound wave. And as that car is moving forward, there's some compression of that sound wave making it sound at a higher pitch. And then as the car passes, that sound wave sounds at a lower pitch. We've all experienced this. If you've stood on a sidewalk as an ambulance was passing by you really can appreciate it. We get that a lot in New York. Doppler shift, you can adjust based on the angle of your transducer. So the way it's defined in ultrasound, flow toward the transducer is called redshift. Flow away from the transducer is called blueshift. This is different than the astrophysics, right? We're not talking about astrophysics. As stars shift away, they are redshifted. In ultrasound, it's the opposite. As something is moving toward the transducer, it's redshifted. So this, we're looking at a radial artery and veins. Let's take a look at that for example here. So here we've got radial artery and veins. How do we figure out what's what? Well, I can know it by anatomic reference, or we can just put a little compression down on the transducer. Veins collapse. Veins collapse, and the artery stays patent. But what if I turn on color doppler here? Color doppler allows for imaging with a nod to the volume and speed underneath, as well as the direction. If I just turn on color doppler, then I'm going to get a mishmash because I have my transducer oriented perpendicularly to the artery and veins. But if I take my transducer, look at the left side of the screen where my transducer is. If I take that and I angle it, and I angle it such that the face of the transducer is now facing the direction a little bit more. The face of the transducer is now facing the direction of blood flow from that radial artery. That radial artery has blood flow that's going toward the transducer, and that looks red. The veins are moving away from the transducer, and so they look blue. That's how color doppler is indicated. In the center portions, I just flip the transducer the other way, then it looks blue in the middle. It's not oxygenation. It has nothing to do with that. It's just the direction of the flow. In this case, it's blue. It's brighter in the middle because that's where most of the blood flow is occurring, in contrast to the more laminar blood flow on the edges. We can talk about this a lot with vessels and with resistance, depending. You will increase your resistance based on with narrower vessels, with longer vessels, and with more viscous blood. A small decrease in radius equals a huge increase in resistance. That's why for smaller vessels, it becomes sometimes very difficult to see that doppler flow. Accordingly, that's one of the reasons we use for small and medium vessels. We use power doppler. Power doppler gives more sensitivity. Now, do you need to know Ohm's law? Heck yeah, you do. If you're going to be a physiatrist, you need to know Ohm's law equals IR. Do you have to know how Ohm's law relates back in a physics equation to ultrasound? No, but I have it here because it's fun. The bottom line is that increasing the resistance will decrease flow for any given pressure gradient. This can be very helpful when you're considering power doppler. For those thinking about tendons, and especially those new vessels, those neo-vessels, which are small to medium-sized neo-vessels, the power doppler is helpful for this because it's less reliant on the angle of incidence. Here we are, same spot, radial artery and veins. We see this glom of red orange here, which is just the amount of flow that's going underneath the transducer. The angulation of the transducer is not important here. What other kinds of doppler are there? There are other kinds. You'll see them on your machine. I'll just mention them here. I'm not going to go into them. You have spectral doppler, continuous wave doppler, which is good for cardiovascular, and then pulsed doppler, which can help with location. Everything you do in ultrasound, moving past doppler, thinking about just doing diagnostic ultrasound, or even evaluating anything, everything you do needs to be imaged in orthogonal planes, two orthogonal planes. Here's what I mean. Longitudinal and transverse are the way that we describe it here. In this case, we're looking at the deltoid in longitudinal and the infraspinatus underneath it in transverse. With the ultrasound oriented in an anatomic sagittal plane, you have an appearance of the deltoid longitudinal and infraspinatus in transverse. This is one orthogonal plane of the deltoid and one orthogonal plane of the infraspinatus. Then you flip it and look at it the other way. The other way to think about this is with pathology. If you are looking at, let's say, the medial gastroc here, we're looking at the medial gastroc and we see, okay, overlying tissue, deep fascia, here's the muscle, here's the aponeurosis of that Achilles tendon. Here's the Achilles tendon starting to form here in the soleus underneath it, but look at this dark area. This is a tear in the medial gastroc at the myotendon, but how wide is it? I can see how long it is. I can see how deep it is, but how wide is it? The only way that I could know that is by adding one orthogonal plane and turning the transducer into transverse. Then I can appreciate how wide that tear is on that medial gastroc. You need to image in both planes always in a radiologic adventure. Also consider your echo texture. This is how things appear in black and white on ultrasound. Is it smooth? Is it bumpy? Echo texture of, on the left, a tendon can look similar, but does have a discrete difference between a tendon and a nerve on the right here. This is at the antecubital fossa. Here's the biceps tendon on the left and the median nerve on the right. Subcutaneous tissue is relatively hypoechoic. It goes down deep into the structures. We saw that with the deep fascia. It can have little small vessels in it and nerves. Transverse muscle has this like starry night appearance because each of those bright little dots that you're looking at and transverse are the ethymesium and the paramecium in their bright dense areas as they're investing through the muscle. The endomysium, the sarcomeres, all of the fluid of the muscle is everything that's dark and tears up dark. If you see this, take a little time to go ahead and get a couple measurements. I don't do a lot of measurements, but again, we're looking at two orthogonal planes here. We talked about that. Here's the gastroc tendon. We looked at this just a moment ago. In this case, we've got a tearing of the aponeurosis of the gastroc and the soleus. A lot of things can cause thickening of this area. You get plantarus tears that cause this. In this case, you can see the fibers of the gastroc are disrupted as they're coming down onto this aponeurotic area. Here we go, imaging in both planes. Once again, we're looking at that deltoid and transverse now. This is a different orientation. This is an anatomic axial plane. The deltoid is now transverse. Infraspinatus is now longitudinal. These two different tissue planes give you a complete picture. In the first image, we were looking at the deltoid longitudinal and infraspinatus and transverse. Appreciate the bursa. They can look different. Chronic bursal changes, which you're starting to see here, have some thickening of the bursa and can result in some persistent fluid line. If the fluid line looks very obvious, then sometimes there's some chronic bursal inflammation there or bursal thickening. Take your eye when you're looking at the bursa and follow this hypoechoic line all the way down, all the way down, all the way down until it reaches the bone. If you can follow the bursa down to the bone, it is the bursa. If you see a hypoechoic line in between two hypoechoic lines, like over here, and it doesn't, a little more superficial here, and it doesn't follow down to the bone, it's not the bursa. This is the rule for the shoulder and the hip. Follow the bursal line to the bone. Tendon, looks like a bunched up broom because of the secondary and tertiary structure of a tendon, you see all these fascicles, very, really tightly bound and bunched up together. Unless you have a multi-penate muscle leading to a multi-penate tendon where you see hypoechoic areas, which invest down through those tendon slips, and those will then appear to the novice, to the rookie, which you guys are not, those will then appear like tears or like tendonopathic areas, but they're not. They're just interspersed, vertically aligned fascial planes between the larger areas of multi-penate tendon. And in longitudinal, the tendon is described as fibular, just like in the very beginning of this lecture, as I described, if you follow these lines out, they don't go all the way down. They intercalate. The intercalated tertiary structure of a tendon is part of what gives it the strength that it has. And pathologic tendon, here's a patellar tendon on the deeper surface, is tendonopathic. It has all three hallmarks of tendinopathy. It looks hypoechoic, number one. Number two, it looks irregular, and it looks thick, number three. One, hypoechoic, two, irregular, and three, thick. So that is the deeper surface of the patellar tendon on the proximal pole, it appears hypoechoic. What can we do? We can use a doppler. If you turn it on, that power doppler, and go ahead and ingest the doppler gain, you can go ahead and find out where those neo-vessels are growing in from the adjoining HOFAs fat pad, in this case. And they will often grow into the most pathologic area of the tendon. These vessels carry nociceptors, which is one of the reasons that I like to do tendon scraping so much, because it can help a great deal. But look up here, too. Even the paratenon, which is adjacent to the tendon on the superficial most aspect, has some signal. And oftentimes, the paratenon contributes nociceptors as well. So that's a little bit on tendinosis. This is not meant to be a comprehensive lecture on all the pathologies, but just to give you a little flavor here of what you may see. Here we see irregular, thick, and dark, the three hallmarks of tendinosis. We also see enthesopathic changes here. But you can differentiate these. And not every tendinopathic area has enthesopathies, and not every enthesopathy has more prox or more distal tendinopathic areas. So look for that. Ligament looks similar to a tendon, except it's more compact, as we discussed. It's susceptible to anisotropy. And bone, remember, the bony acoustic shadow, which some may call a posterior acoustic shadow, although it is not always posterior, it is always deep, though. So I like to call it the deep acoustic shadow or the bony acoustic shadow. Look for it, because it's there in deep calcifications as well. You'll see a deeper shadowing, which can be described as a comet tail as well. This is an Achilles tendon with a superficial calcification. Similarly, you can denote osteophytes sometimes by that shadowing. Cartilage depends on the density of the cartilage. So less dense hyaline cartilage appears hypoechoic. More dense fibro cartilage appears more hypoechoic. And again, you can use your terms for ultrasound to differentiate those in the field of view. Look for things like Baker's cysts. How do you know that something's a Baker's cyst? Well, there's two things that you can do. One is you can identify the area of the Baker's cyst that is in continuity with the intra-articular space. So you want to see the neck of the Baker's cyst coming down into the joint. And the second thing you can do, which apparently I didn't put the image on here, but second thing you can do is to put Doppler on this to find out if there is any blood flow in that. Because you would not want to mistake a popliteal artery aneurysm for Baker's cyst or for that matter, a tumor. Nerve looks like a honeycomb. The interior of the fascicles are dark and hypoechoic and all of that tissue around it, that epineurium and the perineurium looks bright. That epineurium and the perineurium is where most of the fibrous tissue are, tissue is, and that looks bright. But the myelin, the axons, they're mostly fluid filled. The endoneurium is barely visible. So you're going to go ahead and see this honeycomb appearance. And in longitudinal, that honeycomb appearance gives way because of course, you're going to look at that second orthogonal view. It gives way to this thing that almost looks like Penn Station from the top before it had all that construction where you see like train tracks. It looks like train tracks, wider hypoechoic areas than tendon. And so for that, you have a good overview now of what normal tissue structures look like around the body, of how to approach the ultrasound. Should you be able to get to one anytime soon? And what are the very first few things you should be thinking about from a physics standpoint? With that, I'm going to leave you with a couple additional points here. Ultrasound is a means to an end, and not an end within itself. So ultrasound allows you to get a more accurate diagnosis, to allow you to more accurately place your injections, and to improve patient care. It allows you to direct precise and personalized treatments. You should use that accordingly. And I'm happy to entertain any additional questions at this point. We covered a lot of ground. Thank you so much. This has been a fantastic guided tour through some of the intricacies of ultrasound. We really appreciate your time. A couple of questions. One is balancing depth, frequency, and focal zone. If you're not getting a good view of a deep structure, which one do you adjust first? So the very first thing that I'm going to adjust is the depth. Almost invariably, because the depth is, if it's off, if you adjust the focal and the frequency, and then you adjust the depth, you're going to have to go back and adjust the first two. So adjust the depth first. And then whether or not you should do a focal zone or frequency first is probably of small consequence. Okay, that's helpful. Another question. When you're using PowerDoppler, is there a specific configuration you should start with? So the PowerDoppler is going to vary by machine. For most machines, you have a set configuration where you've got a mid-range power, essentially, and that's usually sufficient for most people. What you may want to do, because every time you have a new machine, you have some assistance from a clinical rep, you may want to sit down with either a clinical rep before you get a machine or when you have it to go through all the different settings. Because usually the PowerDoppler settings are buried in about two or three layers of menus, and it's difficult at times to actually get to it, unless you really know your machine. Okay, so they're going to be fairly standard then. Yep. With a tendon tear, is there a way to differentiate an effusion versus fluid versus versus hematoma? So the difference between different fluid structures are going to vary based on timing. If you have a hematoma that you see in a very acute circumstance, I showed you that quadriceps tear. That was a very acute quadriceps tear, and that was a hematoma. Typically, hematomas don't accumulate so much in tendon as they do in myotendons or in muscle. But if you tear or have a hematoma acutely, it's going to look hypocholic, very similar to serous fluid or other fluid that could be there. Over time, as that hematoma starts to coagulate a little bit and starts to congeal, it starts to develop some echos within it. And every hematoma is a little bit different in terms of its time course. And usually, the end result of a hematoma is a portion of it being more stable clot and then the rest being serous. So the answer to your question is it depends on how long it's been. Now, one thing you can do to discern a tendinopathic area that's severely tendinopathic from a tear is to use a little bit of dynamic motion to move the joint or to have the person contract that particular area to see if it separates. If it does separate, then you can be a bit more confident that there is a tear there. I see a question here that came up about direct manual pressure applied against tissues. Does that affect the penetration of ultrasound waves? It does. It is related. So one of the things that happens in my clinic a great deal is the trainees, residents, or fellows will come in the trainees, residents, or fellows will come in and say, wow, I was scanning. And then when you took the transducer, it looked so different. It just looked so clearer. Why does it look different? And then the very next thing I do is I ask the patient, what's the difference between when I'm scanning and when they're scanning? And the patient says, you're putting a lot more pressure, doc. That pressure can often help to displace subcutaneous tissue, particularly when there's a bit more subcutaneous tissue. And that can help you mitigate some of the challenges that you have with penetration, the depth, and with some of the dispersion and conversion to heat of some of that ultrasound. So you have less attenuation because of that. Okay, that's really helpful. Thank you so much. We went over time a little bit, and I know not everyone has been able to stick around for all the Q&A, but this has been fantastic. I really appreciate you taking the time to teach us all about this modality. Thank you so much. Well, you're very welcome. It was a pleasure, and it's nice to see everybody on here, and a great way to do this with the AAP. So I appreciate being able to help out. Thank you. And again, thank you everybody for joining us today. Again, you can reach out. Dr. Visco's email is there on the screen. You can reach out to AAP or myself via Twitter as well with any questions, concerns, or suggestions. And again, look at this website here physiatry.org slash webinars for the daily schedule and recordings of this and other past lectures. Again, thank you so much for joining us. Great. Thank you. Bye now.

ultrasound

medical imaging

COVID-19 pandemic

physics of ultrasound

ultrasound technology

ultrasound imaging

orthogonal planes

transducer holding techniques

color Doppler

tissue structures