Anisotropy, gosh, oh my gosh, how, I'm actually tired of saying the word, but it's important, especially for, to teach for people in the beginning stage, I think nothing is more important than understanding that concept at that stage, because it's after the first 50 to 100 scans, like intentional scans, not just dabbling, that you start to understand it, and then in some cases like in our cases and many others who are like at the advanced class masters level they actually use it to their advantage okay so it could be it could be a double-edged sword An Advanced MSK Ultrasound Center podcast, From Probe to Practice. Hosted by Ryan Martin and Colin Rigney Produced by Jason Kitza at NGG needgreaters.com hey welcome to From Probe to Practice This is episode three. I'm Colin Rigney, and I'm here with Ryan Martin. How's it going, man? Hey, everybody.
How's it going? Yep. Awesome. Now, we're coming with today's episode. Well, first of all, how are you doing, man?
I'm good. As you can see, I'm in one of the clinics here. I was seeing some patients. Not one of the teaching days, but nope, just seeing some patients today. I'm doing good.
How about you? Doing great, doing great. My wife's mother is having surgery today, so kind of on standby with a few things. Everything will be okay, but it's kind of a routine surgery, but at her age with anesthesia, there's always, you know, the post-recovery process, you know, we're kind of anticipating that the next couple days, but it's all good. I got the kids today.
I braided my my daughter's hair you know and it was it wasn't unsuccessful so I'm I think I'm winning so far I've been in that boat before and I'll tell you right now it turns out I do not know how to braid so uh it turns out I'm better at painting her nails than I am braiding hair so we all have our specialties we all have our specialties I might even post a picture of it later I she was happy with it so oh that's awesome yeah um so what are we what are we talking about today We got a couple of good ones, but what's one you want to start with, man? So we got a couple of things that we want to talk about. Obviously, we like talking about, well, I like talking about physics and how to optimize images. Today, we have a couple of topics like anisotropy. It's kind of like the artifact that fools people.
It's like the only imaging modality that you can create your own pathology with the flick of a wrist, right? Right. And so I want to kind of cover anisotropy because it's so pronounced in MSK ultrasound and it can make or break a good scan. So that's one thing that I kind of wanted to delve into. And then in a little bit, I want to talk a little bit about some terminologies of hypoechoic, hyperechoic, heterogeneous, homogenous, anechoic, you know, some some certain terminologies that people may or may not be getting right or wrong.
And so maybe we can sum up like, hey, this is the correct way to use it. And this is why. So I really wanted to start with anisotropy, which is considered an artifact. So when we're talking about physics and optimization, and these are the kind of things. I thought it was a cuss word.
No, it is. It is a cuss word in sonography. Okay. But it's one of those things where you will see these types of questions on the RMSK exam. And it's just something that you need to know because you can make something look torn or not torn and submit that and be right or wrong.
So I'm going to throw it at you a little bit. If we want to talk about anisotropy first, I think that's probably a good starting point. I mean, anisotropy, gosh, oh, my gosh. I'm actually tired of saying the word, but it's important, especially for to teach for people in the beginning stage. I think nothing is more important than understanding that concept at that stage, because it's after the first 50 to 100 scans, like intentional scans, not just dabbling, that you start to understand it.
And then in some cases, like in our cases and many others who are like at the advanced class master's level, they actually use it to their advantage. OK, so it could be it could be a double edged sword. Sure. I'll let you talk to physics part, but I'll talk to like the philosophical side of using it because in the beginning stage, it's really going to fool you. You know, I think everything, you know, everything was tendinosis.
Every something was gone. You know, I never knew what I was. I never knew an incidental finding versus a false positive or in some cases a false negative. Right. But like that's that's where my brain goes with it.
And then, you know, now using that with your motor skills of, you know, how you're how you're actually moving the probe on the skin and what makes it makes it occur and what doesn't. So I'll kick it to you on that. What's what's some tips for people to to first understand it and mitigate it? Yeah, I think it should probably be defined a little bit better for most people. so anisotropy it's it's an angle dependent artifact meaning depending on how you're holding your probe is going to change what you see on the screen so what happens is the beam is not completely perpendicular so if you're looking at a plane of motion and you have a beam coming down that's going to be perpendicular right that 90 degree angle if you're at a skewed angle that's no longer 90 and what tends to happen is sound scatters away from the probe and you get less signal returning to the device.
So if you have less signal returning to the device, you're not going to get as crisp of an image, and you're also going to have less return of echogenicity. And we'll talk more about those terms here in a little bit, but it won't be as bright. The tissue will artificially look darker or hypoechoic, and now normal tissue just suddenly only appears pathologic. So that's, that's the biggest way to explain it is it's an angle dependent artifact. And when I tell my residents or we tell our students or the way we teach is this is user error, right?
And when I say user error, it can also be used to your advantage because you were saying that before. And I'll let you kind of talk about some of that stuff. So I think we use this in clinic all the time to help us locate things. For example, if I'm down at the peroneus or the fibularis group, and I can't discern between the longus and the brevis, if I just toggle my probe, you know, and tip that tail back and forth, I can see them winking back and forth and say, okay, there's longus, there's brevis, there's longus, there's brevis. And so we can use it to our advantage or if we have like just uh an amalgam like this tissue that looks cruddy and degenerative and maybe there's you know microvascular disease or whatever and you're looking for the tendon if you toggle that and that tendon flashes in and out around some scar tissue that's helpful as well but the downside is is if you don't have that angle right and the human body rarely gives you a nice 90 degree angle for every image if you don't have have that angle right you might miscall things so um some of the biggest ones that we find anisotropy is going to be supraspinatus patellar tendon achilles common extensor the distal bicep like if you can't get those right they're going to show you some shadowing or some false positives and sometimes even false negatives yeah quad tended to um oh yeah for sure can i ask you a couple questions yeah so for that angle you talked about being perpendicular 90 degrees um is there a margin for error like can you be slightly off and still be like within um acceptable bounds yeah and and this is mainly because of the transducers themselves do not just have sound beams that go straight out so they have multi-array type of lines i can go go into further detail if i had a whiteboard here but the reason that they have sound waves that kind of travel in multiple angles is so you can pick up on some of that anisotropy and have a little bit more room for error but over 15 20 30 degrees you're going to get more and more anisotropy even starting at as low as five degrees you might start getting changes so that's why we we have to really practice heel to toe and toggling to make sure that we're not getting those, uh, anisotropic, uh, changes.
So yes, there is a margin of error and it starts around five degrees, but you're really going to start noticing it past 10, 15 and 20. Yeah. That's important because I think, you know, we, we don't want to, we don't want to create too much of a perfection. I mean, uh, you know, we want, we all want to be as good as possible and great. Um, but especially when you're just beginning, understanding understand that there is a margin for error with slight you know with a slight angle variability now you did a whole course on this and introduction in our introduction to musculoskeletal ultrasound i think we should put a link for that in in today's uh description um but another question on really now i want to blend this a little bit so go a little bit beyond anisotropy um but anechoic hyperechoic hypoechoic so tell tell the audience a little bit about how um let's go with like absence of sound versus hypoechoic how do you know if something is a true truly absent of sound or is sound waves versus is just being um high uh uh anisotropic like Like, can you give us like a couple examples that maybe in a lot of those, I don't want to put the word in your mouth, but tissue examples, pathology examples, like if you can just walk us through a couple of those.
Yeah. So I think the foundations need to be explained first, right? And so echo texture is how tissue reflects sound. That is just a general term, right? And you're interpreting everything from brightness, the pattern, uniformity, and architecture.
And then from those terms, we can decide, is it dark? Is it light? Is it somewhere in between? And that's where we get the terms hyper, hypo, and echoic. And we have to be specific to its relative to the surrounding tissue, meaning something could be hyperechoic in one environment, but hypoechoic in another, same tissue, different different echogenicity.
So let's talk a little bit about what hyper is, what hypo is, and what anechoic is. And then let's give some tissue examples, right? So hyperechoic is brighter on the screen, right? So more sound waves return for that specific tissue. So it will turn lighter, whiter, brighter on the screen, whereas hypoechoic is darker in relationship to other tissue.
Now, Now, when you're talking anechoic, that is void of return, right? And so when do we see that? Well, if we see it in air, we see it in fluid, we have it with things that do not have resistance, aka impedance. So if the impedance is higher and you can't go through a structure, it's going to be brighter. The less dense that tissue gets, the darker it becomes.
So you think about fluid versus a bone, right? Well, which one's going to be more dense, right? right? The bone in relationship, right? And so that's going to look hyper or brighter in relationship to other tissue.
Other examples are going to be lung fields. So you have more air, you have fluid spaces, you have anything from like ganglion cysts that have a synovial proliferation pocket. These are the things that are going to look hypoechoic and sometimes even anechoic. And it's tough to sometimes discern because I mean, in reality, most machines have have 256 shades of gray. And so it's like, all right, what shade am I looking at?
Well, we're going to determine that in relationship to the other tissue. So for example, if I'm looking at the median nerve between the superficialis and the profundus of the forearm here, it's going to look pretty hyperechoic because it's more dense compared to the muscular tissue. However, as it travels distal, what's going to happen? Well, now it's going to be surrounded by ligamentous tendonous spaces and those have density to them so now in relationship to the rest of the tissue it turns hypoechoic in relationship to the so it's all relative to where you're looking and what you're looking at it against the rest of that environment um and it gets complex and this probably why i like teaching this is because the complexity can be broken down so simply and and i and i think you're right a link for the physics and optimization course should be kind of listed in here somewhere um but yeah that's that's hyper hypo anechoic and a few tissue relative tissues that we could talk about okay now with let's talk about patient positioning in a couple maybe case examples um common errors in evaluating you know we we named a few tissues um but let's start with some easy ones um like distal quad and patellar tendon what What are some common pitfalls in evaluating patellar tendinosis and patient position? What are some common mistakes that you see made and easy ways to correct them?
Yeah, okay. So patient positioning is key. It's imperative. Let's, I don't know, let's start with the Achilles. So if you have your patient seated and they're in a favor position and their foot has a little bit of plantar flexion, that's not key.
That's not ideal, right? because the Achilles is going to have some slack to it. What I recommend in those type of scenarios is you have them prone, hanging their foot over the table, and you can put a little stress into neutral or to dorsiflexion, which will put that Achilles into a little bit more stretch. Now, if that Achilles bows because it's relaxed, that might give you the contour that might change your anisotropy. So it might change your angle and it might change what it looks like.
And so so I recommend putting things on tension if you can help those fibers get taught and help them get a little bit more aligned. So they're more parallel with each other and perpendicular to the sound wave. So that's how I would do it and say something like an Achilles. Um, same thing with the quad tendon is if you have too much extension, it'll go slack. If you get too much flexion, um, it's going to compress the joint capsule.
So you may not get the fibers that you one as well. Yeah, those are kind of like the examples. The Achilles is the big one that I see people misinterpret because they don't understand how to put that biomechanically or anatomically put that tissue on tension. And it's just a simple matter of, hey, are you comfortable laying on your stomach? Can you hang your foot off the edge?
I'm going to put a little pressure on the ball of your foot, create a little bit of dorsiflexion, and that's going to help that probe sit a little little better and perpendicular beams to that tissue is that helpful yeah yeah yeah yeah so i mean a little bit of thought has to go into you know as as clinicians how we um position the patient right and the concept of the concept of putting something on a stretch stretch. It's just, I always tell people this, like it's, you're going to see whatever you want to see generally with a few exceptions. Okay. There's outliers, uh, better if you put the tissue on a stretch, you know what I mean? So what you just described there were is, was kind of classic to that.
So, um, for anybody who's beginning and you're evaluating like an insertional tendon, any kind of insertional tendon, um, you're always going to see it better with that structure on a a bit of a stretch. So that's my piece of input after what you just described there. So you went through the density of tissues, and it's the same density when you're talking about any imaging modality. Really, x-rays and fluoroscopy and even CT, these laws still apply. fly um so from most dance to least dance you know we have bone to air essentially right um what's what type of can you go through and you kind of did this um but let's let's put a little froze hard to determine what uh what type you you cut off a little bit what what now what were you're saying what type of something okay yeah what type of um like pathology conditions clinical thinking with when when you're seeing you know anechoic to hypoechoic to hyperechoic if you see something that's um you know let's talk about you know you gave some joint examples but let's talk about like um like a rotator cuff or a or or a mid-belly muscle tear um how does that how how How do those tissue characteristics help you define and get into a work, maybe not define, but have a working diagnosis from your study?
Right. Well, I think, and when we go over sonoanatomy and how things should naturally appear on the screen, we know that muscle tends to have like this sinuated feathery architecture and it has mixed echogenicity. So it does have, you know, it has striations in there. it has fascial planes in there. So you're going to have a mix of hypo, hyper, right?
But if you have a significant, you know, change in homogeny, so when we talk homogenous versus heterogeneous, it doesn't mean that there's a texture to it. It means there's a change in texture. And the clinical or the pearl that I used to get from Dr. Joel Sellers, one of our great mentors and colleagues is he would look at a wall that had a pattern on it. So like, you know, you just look at a normal wall that has a little texture to it.
And he says, all right, now you look at that wall and it has texture, but the texture is continuous throughout the entire wall. That's still homogenous, right? Whereas if you go and scuff it, put holes in it, now that's heterogeneous, or it's a deviation of that normal architecture. Same thing with muscles. So you brought up muscle as all right how do we define that and how do we look at that as a pathology so if that feathery architecture or that mixed echogenicity that is consistent through the muscle has now changed or been disrupted typically it's going to be a tear if it's a tear it's going to be hypoechoic well luckily i just wrote an entire lecture on acute versus chronic is one of the things with um an acute injury is going to be the formation of a hematoma in this area so a hematoma is going to have blood which is going to be more fluid based right which means it's going to be more hypoechoic within the mixture of that feathery architecture now if it's a little bit more chronic from a tear now you might be seeing things like myositis ossificans whereas that tissue is now coagulated and starting to ossify and now that tissue actually has a hyperechoic space within that feathery architecture so again your clinical brain has to be discerning all right this makes sense to their muscles denervated how how does that look right and colin i'll let you answer that how does a denervated muscle tend to look yeah well the the tissue archetype of a muscle is on ultrasound is in terms of appearance is generally hypoechoic.
It's mixed, right? So it's hypoechoic, it's high in water content. So it's going to be darker. And then it's going to have patches of fascia interposed, right? And that's where the term starry night pattern in healthy muscle tissue comes from.
Now, let's reverse engineer that from when something's denervated right if a muscle is being denied conductivity in the form of how it gets input to contract it's going to atrophy and when a tissue atrophies specifically muscle it's going to lose its hydration it's going to lose its hypoechoic appearance over time time and it starts slow and then it kind of goes rapidly and it turns very hyperechoic at that point and when a muscle is in a period of disuse or a state of disuse fatty deposition starts to set in and not only does it become more hyperechoic in general it's going to start becoming becoming um homogenously um heterogeneous if that is homogenously heterogeneous that's that's that's great dr weinstein weinstein yeah that's a dr weinstein term but let's say for example if you suspected the right leg to have you know like some sort of denervation or uh atrophic type of changes what could you do to to cross-reference that check the other side right yeah right and so uh if you checked it from left to right say that i don't know let's just say an infraspinatus and you have a cuff pathology and you look at the right side and it looks like a cloud rolled through in san francisco over the golden gate right over that muscle belly and then you look at the left contralateral side and it looks like that that feathery architecture well there you you have it yeah you can always too ryan you can also um track its diameter over time as long as you're taking the measurement in the same place um and so for our pts out there you know that's one means to objectively track progress of of what you're working on right um you know in your acl your acl populations if you do these post-operatively right you can measure the pick a muscle right usually rectus fem or you could take um avastus medialis wherever whatever you decide to do i guess that's that's up to you but um you know don't forget that we have these tools on the machine that can help us um be more precise with its state of health or disease right and that's that's just one example i love that because and again now you're skating around or skating towards a topic that needs to be discussed down the road, which is RUSI, right? Rehabilitative ultrasound, which I think is a good biomarker for advancement, progression, and checking how things work and how they progress and utilizing it to show patients how they're contracting or not contracting muscles or how it's atrophic and how it's changing. I think that's a topic that we we should explore later as well is RUSI um but let's let's kind of wrap up here and just kind of ask um is there anything that you want to discuss about anisotropy as an artifact hyper hypo ana anechoic or anything else that you want to wrap up here no i think people if you're really looking to get started in your interest you need to buy ryan's course introduction to msk ultrasound ultrasound, I think that there is a lot of depth to it. And certainly what we talked about today, right, is very broad-based and hopefully provided some value in terms of where you're at, no matter, you know, stage of learning you're in. But with today, right, the final concept I'll just go over again.
Again, it would be a little more philosophical, but at the end of the day, you have to understand these things in order to get to the next stage. And if you don't fully understand it, you're going to suboptimally start, you know, if you're not getting the feedback, right, how do you know where you're at? You shouldn't compare yourself to people who are, you know, on the same stage as you or below, right? You're not going to get better that way. You have to continuously learn and apply these things in order to get to the next stage.
So understanding the fundamentals, I go back to blocking and tackling for football, skating backwards in hockey. You have to know and you have to know the terminologies and how they can be used for and against you. Right. Right. And so I'll just end with that as a philosophical from a philosophical perspective.
Well, then I'll put my two cents in as well, then. ultrasound isn't just imaging. It's real-time interrogation, right? And if you don't understand artifacts and echo texture, the machine will lie to you all day long. And I would say to you, don't be that sonographer.
Don't be that clinician. Don't be that professional that misses out on things because they didn't understand simple artifacts. That's the last thing I'll say on that. Right. Exactly.
Well, I think people say, don't have time you have time everybody has time it's just how do you prioritize it don't forget what got you here like this is just a tool it's not replacing it's not replacing like your clinical your clinical skills and background i know the grass is greener over there but i just don't want to make the effort to climb over the fence and diagnostic musculoskeletal ultrasound really is the next generation and if you are not embracing it you are going to be left behind, period. And it's an extension of your physical exam. An Advanced MSK Ultrasound Center podcast, From Probe to Practice. Hosted by Ryan Martin and Colin Rigney. Produced by Jason Kitza at NGG.
needgreaters.com. If you have any questions about today's episode or are curious to know more about AMSKU, visit amsku.com or check the links in the show notes.
