My name is Lori Lizanski. I'm the chairperson for the FBU eLearning Educational Committee. And, tonight, I am joined by my co-chair, Dr. Anil Kumar. And, tonight, we are hosting our first eLearning webinar since the national office updated their new learning management system. So we've been testing the system, and, hopefully, we won't have any technical difficulties and everyone has a positive experience. Now, before we begin, here's a couple of notes from the FBU office to share, especially for any first-time attendees. This webinar will be recorded and available online after tonight for attendees through the FBU website at no charge. Please take a moment to familiarize yourself with the GoToWebinar program. So everyone should see a question section along the side menu of your screen. It's near the bottom of the column just above the chat function. So please type in any questions that come to mind during the presentation, and, at the end of tonight's talk, we should have some time for discussion. Now, here's the question everyone's asking. To receive your CMEs from tonight's lecture, you need to wait for an email from the FBU office containing an evaluation. You will get that email in seven to ten days. So, please, don't email Missy tonight two minutes after we hang up asking for your CME. Wait for that email seven to ten days later. And then, once you get that email, you complete the evaluation, and that's when your CME certificate automatically pops up. So I hope that's clear for everyone. Now, tonight, we're honored to have one of the pioneers in vascular testing from the Chicagoland area. Aileen French Sherry is going to be presenting a talk entitled Doppler and Color Optimization Connecting Practice to Theory. Aileen's an expert on this topic, and she's been teaching budding technologists informally since the late 70s. And then, 20 years ago, after earning her master's degree, she started formally training students at Rush University in Chicago. Over those 20 years, Aileen has helped establish the careers of nearly 200 vascular technologists. And now, some of her first students have become teachers at Rush and in many labs across the country. Besides her devotion to teaching, Aileen has held board positions for the Chicago Area Vascular Association, Joint Review Commission for the Diagnostic Medical Sonography Group. She – Aileen is a fellow of the Society of Vascular Ultrasound. She's earned professional achievement and certificates of appreciation from SVU over the years, and she's served on SVU committees dedicated to education, certification, and academics. Aileen is also a book editor and contributor to vascular textbooks. So as we perform our studies every day, it's so important to remember the basics and not just rush through studies because we have to meet productivity numbers. Sure, you use Coloradoppler, but are you really optimizing them? Does your documentation reflect your best work? And what's more important, doing a bunch of studies that are suboptimal technically or doing quality studies that help patients get answers and heal? So to this point, Aileen is going to review for us what is important for quality documentation and interpretation. So now, if you would please join Dr. Kumar and I in welcoming Aileen French Sherry. Thank you, Lori. I appreciate the introduction. Good thing I did that over 40 years or I'd be really, really tired. But in any case, let's move on. I have a lot to go through here tonight. All right, this is what I hope you have read already, the overview and objectives for this presentation. Neither I nor anyone on the planning committee has anything to disclose. And at this time, I'd like to really show appreciation for not only Lori, I mean especially Lori, but also for the rest of the committee for volunteering their time. Without volunteers, there would be no SVU. And this is just statements regarding the credits that we get from the University of Cincinnati for presentations. So basically, I really hope you already know how to optimize images. So if you do, to make this presentation more interesting, you might want to ask yourself, do I do that? Why? Why would I do that? Because that's how you were taught or is there some theory behind it? And so what if I don't do that? Not a big deal. Okay, hopefully this will clear up some things. Hopefully you'll say, yeah, I do all that. I'm pretty good. Okay, so what is optimization in vascular ultrasound? Optimizing the dictionary is defined as the best for vascular images. Optimize is the most effective use, and for vascular ultrasound, I would say the best use of the controls that you have. But why optimize anyway? Basically to deliver clear data defined as easily interpretable images. You don't want the interpreter to be guessing what's on that and have to figure out what's on your image. We want to deliver the most accurate velocities possible and leave no doubts for exam interpretation. The focus on this presentation, since it's only an hour, it's a lot to cover. I would normally cover this in about one semester. I'm going to focus mostly on arteries, on the general equipment controls only. I can't possibly go over all the equipment controls for every vendor that's available. If you need more information, you should go to the vendors and ask questions of the applications person or get a meeting together. And I will cover some exceptions to the rules, but I can't possibly cover all of them. So I know it's about Doppler in color, but first we have to get an optimal B-mode image to get good Doppler in color. So what is an optimal B-mode image? First of all, you have to align your transducer on axis to the vessel. The way you know that you did that is if your vessel goes across the screen and is open at each end on your monitor. Check your depth. Make sure you can see the vessel of interest easily. You don't want the vessel way up here and then have a lot of tissue below. That is not important because you can't get details in the image. So show the least amount of tissue deep to the artery. You need some though. And in details at your gain and your TGC, we want our goal is clear, crisp, bright walls and being on alignment helps that. A black normal areas in the lumen and fairly equal brightness above and below. For instance, if this was very dark under the vessel, it makes it more difficult to see what's going on within the vessel without that contrast. This is just describing a little bit of how you get aligned or on axis to the vessel. This is the vessel in black here and your transducer is the green one. If you are laying the transducer right on top of the vessel, you'll get this image on the right where it's open at each end. If you're coming across the vessel, your transducer is picking up tissue, vessel, tissue, just like here. Tissue, a little bit of the vessel and tissue. You are not aligned, so you have to pivot your transducer to align with the vessel. Takes a little practice, but even vessels that are tortuous and come in and out, sometimes a new window will allow you to do it easier. Optimal Doppler waveforms. Goal, easily interpretable waveforms. So what is a Doppler waveform? Here's a newsflash for some of you, I'm thinking, that the waveform is a display of frequency shifts. These are not actually velocities on this waveform. Each dot on this waveform actually represents frequency shifts. So to explain that a little more, we'll go over it. So you know the Doppler effect. When a sound wave hits a moving structure, the reflected sound wave returns with a different frequency than that that came in. So following a single echo here, it comes in at 3.6 megahertz, which is different than your your beam mode frequency. The Doppler frequency you'll see on your screen on the side usually, and it'll be lower. But nonetheless, there it is, 3.6 for this example of a single echo. Comes in at 3.6 and then it's reflected at a frequency that is different than what came in. In this case, it's 3.6014. What the machine does is it collects everything from the sample volume that comes in, distinguishes what the frequency is, subtracts the initial frequency from the, if it's a higher returning frequency, it'll make that subtraction. In this case, it's 0.0014 megahertz difference between incoming and reflected, which translates into 1.40 kilohertz, which is how we explain or describe frequency shifts, and puts a dot, for instance, right here, right at the 1.40 kilohertz line, at this point in time, there's this echo. That's basically what's happening. So each frequency shift, first, each echo that comes back from the sample volume is calculated for its frequency, subtracted from the initial, and then a dot is placed on this wave at the point in time where it was collected. So all these dots here are actually frequency shifts. So let's just talk a little bit about what affects the frequency shift waveform when you're scanning. Don't worry about, I won't make you do this on quiz, but in any case, here's the Doppler equation. And if you look at this, we're trying to measure the frequency shift for the waveform. So this is constant, this is average speed of sound in tissue, which is constant. If you change your Doppler beam frequency by changing transducers, that can affect the frequency shift. And the way you steer your Doppler beam affects this angle here, and then the velocity of the red blood cells is most important. But when they're on top here, anything, any of these that goes up makes the frequency shift go up directly proportionally. This doubles, this doubles. If this goes down by half, that goes down by half. So basically, the frequency shift changes as the velocity changes. So when we look at the Doppler frequency shift waveform, it represents velocity changes over time, because they are directly proportional. So how does this, the beam steer affect the waveform? This is really a diagram meant for a pencil probe, for a CW Doppler probe. But flow is going this way in this vessel. If you steer at 40 degrees, you'll get a waveform approximately like this. These are frequency shifts. At 60 degrees, it will be smaller. At 90 degrees, it's uninterpretable. If you go the other direction, you get negative 60 degrees at that height, and at negative 40, it's also reversed, but a higher, a higher one. So I'm just saying, steering makes a difference with your waveform. More on frequency shifts. So not all red blood cells move at exactly the same velocity. That's why you're getting different ranges. Like at this point in time, those are frequency shifts or velocities there to there. It's a smaller range compared to here. At this point in time, it's a larger range. And if there's more disturbed, chaotic, turbulent flow, there's a greater range of dots or frequency shifts, and that's what we call spectral broadening. Sometimes you even get some reversal flow under the peak at a spectral broadening. And multiple echoes with the same frequency shift, if they're moving the same, the exact same velocity, it will form a brighter dot, and then if there's fewer red blood cells moving at a different frequency, they will be a darker dot. It's hard to tell on this one, but if you look here, it's brighter, and over to the side there, it's not as bright. So if you have very high velocities, like 300 centimeters per second, and it goes actually below the baseline, each of those dots is likely to be dimmer because there's fewer. It's the same number of red blood cells, but they have a larger range of velocities. You might have to turn up that gain a little extra to see them. So what is velocity? Velocity is speed and direction. It's both. So Doppler waveforms also indicate flow direction toward or away from the Doppler beam. Blood moving toward the Doppler beam, when you're looking at the waveform here, it comes from each echo toward the Doppler beam is higher than the incoming, like in that sample. That creates a positive frequency shift and a positive number on the Doppler scale where the dots are placed. Reflector motion away from the Doppler beam, the echo frequency is lower than the incoming. It's a negative frequency shift, and you will see here, I hope you can see the negative, negative 10, negative 20, negative 30. They form negative numbers on the Doppler scale if the reflector motion is away from the beam. That will become important a little later. Okay, optimal Doppler waveforms, these are the controls we'll go over. So first of all though, why do we need to be aligned anyway? Because the Doppler angle that you know is coming up is going to be important for velocity measurement is the angle between the Doppler beam and flow direction. So we use our angle cursor or angle correct to tell the machine what direction the flow is. Flow basically also is a volume of fluid moving past a point per time. In blood flow, it's milliliters per minute. You can think of it as gallons of water in a flood going past your house in a minute. It's a volume. It's not one red blood cell going one way. Flow direction therefore is assumed to be parallel to the vessel balls, true or not in cases, but we do assume that. And if the probe is not aligned, the angle, the angle cursor might not set the flow direction correctly. So in this example, the transducer is directly on the vessel. The flow is going the same way. Here is a diagram of the vessel flow. You put your angle cursor parallel to the walls. You will be indicating flow direction. However, on the other example where we have the transducer just crossing the vessel, we do not see it open on each end. And you might think these are the two walls and set your angle cursor parallel to those walls, but you see in actuality the flow is going across this way. It's very important to align your vessel or align your probe to the vessel. So Doppler beam steer for the best Doppler angles 60 degrees or less is what we're going for. To set up your steer, the most efficient way is to steer the Doppler beam to the lowest point of the vessel going across your screen. So here the vessel's going down to the right and the Doppler beam is set down to the right. In this case, the vessel is going down to the left right here, beam down to the left. However, if you're scrolling through this you're going to have to change your steer because now it's going down to the right for this part. And it's okay to use a vertical as a beam steer as long as your vessel has an angle to it. You frequently will get a better waveform if you can get 60 degrees with vertical. It's okay to do that. So what happens to the waveform if you don't steer to the low end? You get bad Doppler angles here. This should be going down to the right. It's not. It's going down to the left and look at the resulting waveform. It's almost 90 degrees there. So anyway, I'm just giving you a tip to get the best way, best steer at best the first time around. Okay, Doppler baseline settings. Traditionally, you set the baseline low for arteries and normal direction of flow or waveform is above the baseline. That's for normal direction. But you want to leave a little bit of room below the baseline to show reverse arterial flow direction. For instance, if you have a multiphasic or triphasic arterial waveform, you want to leave a little space below this baseline to show that. For veins, we set the baseline higher. Normal flow direction is displayed below the baseline for veins, but we'll leave a little bit of room above it to show reflux reverse venous flow. And these are obvious examples. The baseline is too high, so we get aliasing. There's nowhere to put these higher frequency shifts, so it comes from the bottom. Appropriate baseline leaves a little room for reverse and plenty of room to get the peak there. And this baseline is too low, so actually the reverse flow segment is aliasing to the top. What this does, it makes it harder to interpret with these two. It makes it harder to interpret, and that's what we want to avoid. So, sample volume size. We use the smallest sample volume when we want to measure velocities. You can use a little bigger if you're just scrolling through, but for velocities, we want it the smallest possible. You can make it larger if you're searching for flow, any kind of flow. If a vessel looks occluded and you want to see if there's any kind of flow, it's okay to open it up. But every time you open it up or you're not aligned correctly, you know there's a third dimension. This is called sample volume. It's not just up and down and back and forth. It actually comes out towards us from the screen, and it goes behind the screen. If you have a very large sample volume, it might be catching flow in another vessel. And what about the size of the sample volume? Here's an example of a small sample volume. You get to see the spectra window, and the red blood cells are moving in similar velocities here, creating similar frequency shifts. Here, it's same place, same vessel, large sample volume. It fills in the window, and it's just a little bit harder to interpret. What about where should you put the sample volume? I think it's very important to keep the sample volume center stream. If you have a wide open vessel, it will be in the center of the vessel. If you have plaque that pushes the flow channel up a little, then you're going to have to move up a little. It's center stream. Try to avoid putting your sample volume at the walls. If you are trying to find the highest velocity in a stenosis, and you go up and down by the walls, if this is your Doppler beam, you might be catching flow trying to fill in this open area. See, it was very narrow here. Blood has to come in here to fill, but now you're at a different angle if you put your sample volume up there or down here. Keep it center stream. If you are in a wide open vessel, you'll catch lower velocities along the walls. Lower extremity collaterals often come off perpendicularly outside your alignment, so you don't even see that they're there, but flow currents by the walls might be going into these collateral branches and create another angle, so it's just important to stay in the middle. In addition, flow around a normal curve typically has higher velocities along the outer wall with no stenosis. Now, you don't want to report those velocities by the wall, because it will just make everybody look two and three times. Is there a stenosis? Isn't there? Not really. Just stay center stream on a curve, if you have to measure on a curve. Anyway, stay center stream. I think it just makes sense unless you see a stenosis there, and then you have to go center stream anyway, but the stream might be on the outer wall, but that's rare if ever. All right, here's your exception to keeping your sample volume midstream. You're familiar with the carotid bulb. There's a sudden widening, so the flow comes over here, then has to fill this space, and it goes backwards for a short period right there. That's called flow separation. It separates and goes a different direction. Now, if you put your sample volume here where the red dot is, you're going to be getting forward flow, reverse flow, and no flow areas, so that's not going to be helpful for someone who doesn't understand flow separation or flow in the carotid bulb, and you don't want to confuse anyone, so this is okay to put it a little closer to the external carotid artery where flow is all forward. I wouldn't put it by the wall, just out of range of this black and blue area, just to make it clear. This is a one good exception. All right, now gain. Optimal waveform gain shows a bright clear waveform with only a few specks outside it. If you don't have an optimal waveform, even though you know you've steered appropriately and your scale is good and you still don't like it, what you might do, like the example I gave you where velocities are very high but it's not looking good, turn the gain up until specks appear outside the waveform to make sure that you're picking up all the flow. This avoids missing flow from under gain. You can make a blood vessel look occluded if your gain is just not set correctly. Then turn the gain down until all but a few outside specks are gone. I like to see a couple outside specks that proves that the gain was high enough. Not a lot, just a few. Okay, here's some gain examples. The first one is fine, appropriate gain. There's not a significant number of speckles outside. Under gain we already talked about. It could make something look occluded that isn't, it's just you didn't turn your gain up. But over gain creates this artifact called crosstalk. This is actually a mirror image of the waveform on the other side. In this case, the reverse flow is aliasing and now it's hard to see where the actual peak is and what's going on there. So you have to make sure that is caused by over gain. So that's called crosstalk. You can overestimate peak velocities if your gain is too high. And the exception here is sometimes a little over gain is necessary just to see a waveform that has a lot, a wide range of dim dots. Optimal scale, basic rule of thumb, the waveform should cover at least half the total scale here. This is not a rule. It's just a suggestion. In this case, the full scale is 160. The PSV measured here is 81. It's just barely over half. That's fine. Whereas this one, the scale adds up to 360 if you add the top and the bottom. But the PSV is only 77. So now you can barely read the configuration or shape of this wave. And you might not be measuring velocities accurately either. So make sure you have appropriate scale. If you have too low of a scale, then of course you get aliasing, which is unacceptable for waveforms. It just occurs when the scale is too low. And like I've been saying, it takes what it had to cut off at the top and put it from the bottom. This one would actually be this high. We have to decrease the baseline and increase the scale here. Or you could change to a lower Doppler beam frequency. And what about this invert? We need to use invert. And sometimes we have these great presets, and the machines can do it often. But we use invert as needed to demonstrate flow direction in the traditional manner. Traditionally, normal or integrated flow direction for arteries is above the baseline and veins is below. Abnormal or retrograde flow direction, like if the vessel is acting as a collateral, the flow may go the wrong way for an artery. So we display retrograde arterial flow below the baseline, and venous reflux or retrograde venous flow above the baseline. So the interpreter is going through all the pictures and all of a sudden, whoa, why is that pulse below the baseline? Well, if you did that, you made it obvious, which is correct to say that it's retrograde flow. But also note any retrograde flow in the report. Don't just depend on the person interpreting it can read it that well. So you must know how to determine flow direction to use the invert properly. That's coming up later. Here's some samples. This is the same artery with antigrade flow. These are positive values, all right, on the right. And the wave is above. This is the same one. The wave is above, but the values are negative because it was inverted. In order to show this is all normal, there's just this curve in the vessel that made it negative and positive. All right, so your optimal waveform vessel on axis, steer to the lowest end for arteries, make the baseline low and leave room for reverse flow, sample volume small and center stream, Doppler gain set for clear bright waveforms with few or no outside echoes to make sure they made it high enough. And the scale is set so the waveform fills at least half the full scale without aliasing. An invert is needed to show normal arterial flow direction above the baseline and normal veins below. We love presets, but you still need to make sure the waveform is easily interpretable. So now you have an optimal waveform. That was a lot of work. It really isn't that hard, especially once you get used to it. But optimal velocity measurements. All right, so you want to make sure you measure velocities with the Doppler angle 60 degrees or below. And it is because of this cosine of the angle which we'll get into in a bit. This is the same equation just solving for velocity. So we have waveforms. So we have the frequency shift, speed of sound, that's the same, I mean in tissue, speed of sound in the tissue, the two is constant. You already have a waveform, so you already have your incoming frequency. So what is going to make the difference with this velocity is this angle. The cosine of the angle is what's used in this equation, but you have to start out with the angle to get the cosine. So what is the Doppler angle? Doppler angle is angle of Doppler beam to flow direction. You set the angle cursor parallel to the walls, or some labs have a protocol that you set it parallel to flow to indicate flow direction to the machine so the equipment knows the Doppler angle. When the angle cursor is parallel to the walls, it should also be 60 degrees or less. We do not take angle measurements at 70 or 80 like that. Okay, so what does cosine have to do with that anyway? Cosine is basically a value that corrects for taking measurements at an angle. Each angle has a cosine value assigned to it, like we see in this chart. On the left side here are the angles, and on the right column are the cosine values connected to it. The cosine value, this is the number that goes into that equation. It's not the number over here of the angle. It's the cosine value that makes a difference in that equation. Note that a cosine of 90 degrees is zero, which is, if you are 90 degrees, why you get a lousy waveform and no measurable velocity? It's because of this. Once you put zero in an equation, the whole thing is zeroed out. It's only you have a couple red blood cells moving not quite at 90. So, note the cosine of zero is one. Well, that would be a perfect world if we could send the Doppler beam right in the same direction as the flow, we wouldn't have to make any corrections. But it's rare that we get to do this, you know, the blood vessels are parallel to the skin. So we have a hard time getting zero degrees unless there's a vertical course to the vessel. Note the difference in the cosine values for a 10 degree difference in angle. So 80 degrees to 70 degrees, if you set it at 80, but it was really 70, there's a 17.17 difference between these two. So you have an error, 0.17, right there an error because you didn't set it correctly. If you set it at 60, but it was really 50, there's a 0.14 amount of error 14% error there. 0.77 to 0.87 from 40 to 30. Well, we're down to 0.10. It's getting better. And if you are off by 10 degrees down here, 20 to 10, I hate to say only but it's only a 4% difference. You see these are not linear. This is why we do not measure above 60 degrees because the difference from here to here is too big to be acceptable. Some labs choose to use a standard angle to reduce intra and inter observer variability and velocity measurements. Standard is often 60 degrees, but some labs are seriously considering to use 50 or 55 degrees because that cosine value is lower and the difference between, you know, one angle and the next is less, but it's really difficult to obtain 40 or less on most arteries. I used to ask my students to try to get that in student lab. It's really hard. So what's the best way to get a standard angle if your lab uses that? First of all, you can put in your Doppler beam towards the low end of the vessel and set your angle cursor to say 60 degrees. Now you are not done. Then you use this fine steer control, which I love, to move the steering here to here where the it's there. Both of these are 60 degrees, but this one is parallel to the walls and now you have it. Just a tip. So if you change the beam steer, it'll change the waveform. If you change the angle cursor or angle correct up here, there is no change in the waveform. But you know what changes, just interestingly, is the scale, the velocity scale, because now you're telling the machine what angle to use for the velocity measurements and it knows what, I mean, it's magic, right? So it knows what scale to use here. So at 80 degrees, the scale is 300. At 70, it's 150. At 60 degrees, the scale is already down to 100. And at 50 degrees, the scale is down to 80. If you, as you turn your angle cursor, you are changing the scale right here. Now, if you change the angle cursor, then what happens to the velocity measurement? Let's take a look. At 80, this is the same vessel. This is a frozen image. You've got a beautiful Doppler waveform. And the only thing we're changing here is this angle cursor. At 80 degrees, it measures the peak systolic velocity right there. It's 259. At 70 degrees, it's already down to 131. That is a big difference in velocity measurement for a 10 degree difference in angle. This is the only one here that's parallel to the wall. Here, the angle cursor is parallel to the walls at 60 degrees and the velocity is 90. And here, the angle is 50, but the angle cursor is not parallel to the wall anymore, and it's 70. So here, we have a difference of 20, which is still not great, especially when the percentage change for higher velocities is a higher number. But in any case, once again, it's a demonstration of why we do not measure any velocities over 60 degrees, and it has to be parallel to the wall. It can say 60 degrees right here, but if this isn't parallel to the walls, it's not true. This one's actually 40 degrees. You make it real by making it parallel to the walls and 60 or under. How do we measure peak and end diastolic velocity? Peak is usually pretty easy for people. End diastolic velocity is at the end of diastole. This is the diastole portion of the wave. It's end diastole right before the next peak. You don't measure it there, and you don't measure it there. If you have arrhythmias, you do not want to measure, I mean, usually we want the highest peak, right? But not after a long break in the pulse, because the next one, the velocities are flying, and this is fairly false. I like to have two or three consistent, fairly consistent waves like these and pick one of those. All right, here's the tip for setting the angle cursor on a curve to measure velocities. If possible, I avoid measuring velocities on a curve. I haven't seen a stenosis except maybe once on a curve. But if you're there, set the angle cursor right here. You set it parallel to the walls right at the location of the sample volume. Why? Because we're only taking echoes from the sample volume. We don't care what's going on up here at the other end of the cursor. We don't care what's going on here. We only care that as the angle cursor goes through the sample volume, it is parallel to the wall. I made these thicker. Parallel to the walls, right where the sample volume is. So don't worry about this. Don't worry about this on a curve. Make the center parallel to the walls. All right, so optimal Doppler velocity measurements, consistent waveform, center stream, angle cursor parallel to the walls, or flow extremely important at 60 degree or less, PSB is the highest peak, and end-diastolic at end-diastole. All right, we're going to go into a little direction so you know how to use that invert. All right, there's many, many ways to determine direction of flow. If you have your favorite way, you don't have to listen to mine because I'm only presenting one here. Use what works best for you. Just make sure you're doing it right. One way to make sure is compare with other staff so you can talk about it and figure out if you're all doing it right for consistency. This is the acute obtuse angle technique. I found it to be the fastest for myself. Using Doppler waveform, this is what you need to know. Flow direction, positive value on the Doppler scale means flow towards a beam and negative is away. Know how to identify acute and obtuse angles, which I'm going to go over. And in the long image, the patient's head's always to the left of the screen and the feet to the right. But when you're doing arms, you have to find out what the protocol is for your lab, and it'll be heart versus fingers. All right, obtuse versus acute angle. Here's a 90-degree angle. Flow toward the beam forms an acute Doppler angle. So here's 90 degrees. An acute angle is the smallest angle, less than 90 degrees. So this is less than this. Whereas flow away from the beam forms an obtuse Doppler angle. Remember, Doppler angle is beam to flow direction. So anyway, this would be 90. Well, this is a lot larger angle than 90 degrees. Okay, so put it more in real life. Here's a Doppler beam coming down. If you look at this, the flow either has to go that way or that way in the vessel. This is a smaller angle than this. So this is an acute angle. That's obtuse. An acute angle here would say flow would be going this way. If there's an obtuse angle, flow would be going that way. So three steps to determine flow direction with Doppler waveforms. Okay, is it flow towards or away from the beam? You look at the scale. The waveforms are up here, positive, positive flow towards. Flow towards a beam forms an acute angle. So we follow the beam down and we say, which one's acute? This or this? This looks like the acute angle. So I think the flow is going this way. And what's over here on the left? The head. So flow is towards the head. Two more samples. This waveform here has negative values. Flow is away. Negative value means flow is away. And there's an obtuse angle here. So we come down here. That's acute and that's obtuse. So the flow must be going this way towards the feet. And you can, if you have a vertical beam, it remains the same. Positive values towards. In this case, positive value are towards. Oh, I should say this. Using a vertical beam, you still have the acute angle for towards, but it also shows flow going in upwards direction, whereas away is obtuse and downward. No reason why you can't use acute and obtuse. So here, flow is positive. Positive is towards. Towards is acute. Here, I think we have an acute and there we have an obtuse. It's flow up towards the head. Now color. Color is Doppler. It follows many of the same theories as Doppler. The thing you need to know is that in the color box, the Doppler beams making this image are parallel to the sidewalls. So the Doppler beams are coming in this way, not this way. They are parallel that way. The color box steer is just like steering. Your Doppler beam steer to the low end of the vessel or you could use vertical for tortuous vessels. Just use what looks best. Oops, sorry. The color box size. I like to use a large box when I do color if possible because of like lighten up the room instead of using a flashlight and just getting a little color here. However, for deep vessels, you usually need to make your box smaller because of the frame rate. Color, scale, and gain. We start the scale at 0.3 for arteries, 0.10 for veins, but you have to adjust both the scale and the gain as needed to get your best color image. The color bar here can be inverted just like the scale. We make arteries red, veins blue, unless it's retrograde. Then arteries will be blue and retrograde venous flow will be red. Here, box steer. Steer to the lowest side of the vessel. This vessel going down to the left. The box is down to the left. Here, the vessel goes down to the right. The box is down to the right. Here, we have a vessel going down and up. So vertical works for this. But if the vessel is horizontal to the box, and not horizontal, if it's horizontal on the screen and perpendicular to the box, you get a lousy wave. We don't know. It's red and blue and all kinds of colors. All right. Color gain. Once again, just like Doppler gain. If you turn your color on and it fills the wall to wall here, and it's beautiful, and you didn't see any pathology in B-mode, it's great. You don't have to mess with your gain. But if you get this, this is over gain. Color will bleed into the tissue and you have to decrease your gain. If your color is patchy like this, you may just have to turn up your gain, but you might have to also work your scale. So you have to be careful with patchy color. Here's your color bar. Can't read direction without the color bar. The top color is what the color assigned to what is towards the Doppler beam. The color on the bottom is a way. The number on the top and the number on the bottom are a mean velocity, not a peak. That will be associated with the color on top. So at 34 centimeters per second, there will be an aqua color. It's the mean velocity. The black in the middle is the baseline. It is assigned to anything that's 90 degrees to flow, or if there is no flow, because there's a thrombus there or an anechoic plaque, it will be black. All right, and the color bar can be inverted. So let's look at color scale. Look at the scale. 1.1, that's way higher than 0.3. What are we missing? We are missing sensitivity to low flows that happen to be along the wall here. This, the scale is 0.06. Basically, we have aliasing through the whole vessel, which is not helpful to anybody. That scale is just too low. Color aliasing versus change in direction. So let's take a look at this. So here, we're going to look at this part. We say, oh, this and this has different colors. Which one's aliasing and which one is change in direction? Okay, this has aqua, yellow, and red. Let's look at our bar here. Here we have aqua, but wait a minute, we have yellow and red. Let's look at yellow, red, aqua. Red, I'm sorry. Red, yellow, aliasing will then associate the top of this, the bottom of that bar to the top of this bar. Yellow is next to aqua, that is aliasing. If you see dark blue with black next to dark red, that is a change in direction. Those are two different directions. In this particular image, when I first turned this on, this was black, and I was thinking, is that an anechoic plaque or what? Oh, I better just increase my gain, decrease my scale. Oh, decreasing the scale helped, but then I got this aliasing, but it's acceptable. Otherwise, the interpreting physician may say, wow, that looks like a big anechoic plaque. Better to put up with a little bit of aliasing to show there's flow in an area. So, optimally for your color image in a stenosis, it's best to show just basic color that changes to aliasing in the narrowed area, and then it might just go back to the main color or it might show turbulence there. But the important thing is to switch between B-mode and color, B-mode and color to make sure your color is not overlying any plaque or thrombus. Color aliasing also is not diagnostic. I've heard doctors say, oh, but look, it's aliasing, must be a stenosis. No, it just means that the scale is not set for the conditions at hand. That's all. When can that happen? If there's high velocities in the stenosis, you'll get aliasing. If there's a low Doppler angle like zero or 10, that yields higher cosine values and higher frequency shifts, and therefore higher on your color scale. It just means the scale is not high enough for conditions and you cannot make a diagnosis based on color. You need to set the scale to show the appropriate conditions, and color alone is not diagnostic. If you see a brewery, you know how breweries are, they make vibrations in the tissue and you're like, wow, is that over gain? Not this time. Breweries are seen in the tissue and sometimes they cover over exactly where a niatrogenic fistula is, for instance. What I would do is I'd take one picture to demonstrate the color brewery, make sure that you have your best scale, of course, and then take another picture during diastole. Many breweries only occur during systole. If you turn your gain up and look for diastole, then it's easier to identify the exact location of the hole in the vessel. Optimal color image, filling wall to wall or to the edge of disease without overlapping it, a couple color specs outside just to prove the gain is not too low. Focal areas of aliasing may be present and useful, but aliasing with the entire vessel is not acceptable due to scale. But sometimes with, if you're looking at a dialysis fistula, it's a very high velocity and that's what happens. Use invert to show antigrade flow. Antigrade flow in arteries is red and veins in blue. Retrograde is the opposite. Last thing on our topics here, determine flow direction with color. You already learned this, or at least I already taught it, with waveforms. So for color, note the color in here. You have the big color box. Pick one spot. In this case, I picked this spot right here where it's yellow surrounded by basically red, orange, kind of orange. So we're just going to pick one spot. If you try to figure out the whole thing and make yourself crazy, pick one spot. You could even pick that one. But I think most of this is red. We'll pick here. Note that that is yellow. Yellow here is on the bottom. The color on the bottom means flow away and will produce an obtuse angle. So the Doppler beams are parallel to the sides of the color box. So I know the beam's coming in here and I'm looking for an obtuse angle. Here's the obtuse angle. It's a big angle. So flow is going to the head. Here are two quick samples. Blue. Blue is on the bottom. The bottom is away. The Doppler beam is coming this way. That would be an acute angle. That would be obtuse. Flow is going to the head. Here is red. Red's on the top. That means flow towards and it forms an acute angle. So Doppler beam's coming here. That would be acute. That would be obtuse. This one's also going to the head. And you need to remember a frozen color image is only a snapshot in time. This is the same vessel. One is red. One is blue. It's exactly the same place in the same vessel. What the heck? Which way is color going? Well, here's where it came from. It came from a normal peripheral artery with multiphasic flow, including a segment of reversed flow. Flow below the line. So this, of course, was frozen during systole. This was frozen during the reversed flow segment. And that explains why we never use a snapshot in time of color to make a diagnosis. You have to follow up anything you see in color that looks interesting with a PW Doppler, which will show you a long period of time to see what's going on. So this is the last image. Not the best images here. This is what we're trying to avoid. Each of these requires more work to interpret. This one I'm not sure where the walls are. And I don't even think there's an angle correct in here. And if this is the waveform, not really sure what that means, except there's a pulse. So this cannot be interpreted well for velocities in the direction, things like that. And here we have a nice blue vein, except the flow is above the line. So this takes a lot of interpretation. Need help. Okay, thanks for your... The velocity with the lower angle, was it the same vessel or different vessels? No, it was the same vessel. I think it's the one where you showed like taking right there, like taking velocity. So why do smaller angles give like lower velocities? Oh, maybe because, oh, let's see, lower angle. I have to find my equation for velocity. Here it is. So if you have, this is angle. So if this is low, the cosine is the opposite, it's high. Okay. But when you're in the denominator, this will be lower. It will be the opposite. So the angle is low. The cosine is high, right? If that's zero, that's one, that's a high cosine, isn't it? That's low, that's high. But when you're in the denominator, it has the opposite effect on the other side of the equal sign. So that's low, that's high. So that will be low. I hope that helps you. You have to understand cosines in algebra. Okay. Do you have an opinion on the, what's the best degree for beam steering? And maybe that means, you know, like maybe some machines still have 20 or 30, you know, you could, you're limited like the Sequoias versus the- I don't really pay attention to if it's a 20 degree steer or a 30 degree steer. I just steer it, whatever works to get the best angle. Okay. How about when you're measuring volume flow, like in a dialysis graft? Yeah. Include the graft double lining, or you want to measure like within the flow channel? What should you- What? If you- Say it again, sorry. No, if when you're measuring volume flow, like in an AV graft or dialysis graft, should you include the graft double lining or measure within the lining? Sorry, I don't feel comfortable answering that because that's not what the presentation was about. So I would have to study it further to know the answer to that question. I think I know what they're asking. And I'll just give my opinion. I think don't include, don't include the graft lining. Just try to get the, as much of the flow channel as you can. That's what I try to do. So I hope that- And the question is regarding where you put the size of the sample volume. Is that what the question was? Oh, yeah. Like, Eileen, sorry, but you- No, I'm good. By the time some of these, you know, new studies has come online. But you, when you do dialysis- I know how to do it. Yeah, and you have to, how, like, you don't want to have your sample gate too wide because you don't want to, like, get the walls of the graft or tissue. So the question was, do you want to have a little bit of the graft lining or not? Or just have the- I want to know, I want to see somebody do that and see what difference it makes. Oh, I'm waiting for you to come over tomorrow. Come over tomorrow and we'll try it out. Yeah, we'll try it out. It seems that it wouldn't be very large and these flow numbers are, have a wide range for normal and abnormal, right? It's not a perfect, it's not a perfect thing because that, the vessel's getting larger and smaller too, you know, so. Yeah. You know, while you have your sample volume in it too. So I'm not sure that it's going to make a huge difference, but I'd love to see a study. All right. So on the, on the same topic of AVF. So if you have, like, an aneurysmal segment of the vein in the outflow tract that AVF with thrombus, maybe within the lumen, should we measure sample volume for, to include the entire vessel lumen with thrombus or just patent lumen of veins? Oh, what are you measuring? You mean you're measuring flow or what are you, are you just trying to get a. Yeah, maybe volume flow again. Like if you have an aneurysmal segment. Sorry, I can't help you. You can answer it, Marie. I think, I don't know, I might just do the flow channel. I don't know why I would think, my inclination is to think why, why measure the thrombus. Yeah, and that might skew your, I don't know if that would skew your velocity measurement. But you just want to know what volume is getting. I mean, usually, usually you're just putting your sample volume where there's flow. Correct. Yeah. Yeah. Should you put an angle in a vein pulse doppler? I think we talked, we just, we, we said we were talking about that a few questions ago, right? I think so. Yeah, when, when we just said that there might be some situations where you would need to measure the venous flow, but usually not. Yeah, usually not. I mean, it's interesting. I have measured a venous velocity, but the problem is there's no criteria. Now, if you have criteria, that would help a lot. Somebody maybe wrote a study on it, but when I don't have criteria, I try to measure some equivalent location, like on the other side, like here, it's screaming at 300 in the vein because there's extrinsic compression. And over here, it's only 40, you know? Right. And, and here's, here's an opinion from one of our attendees concerning venous doppler angle, that you need an angle when measuring the velocities to assess for a stenosis. But there's, there's diagnostic criteria published for renal vein and iliac vein. So it is out there. And if you're in that situation, then you should probably set your angle and reference what diagnostic criteria is, let's say for renal veins or iliac veins. Good to know. I didn't know that was out there. Good to know. Some texts indicate that 45 to 60 degrees sample volume to be optimal. Do you think less than 45 is also okay? 45 to 60 degree. Yeah, for an angle is optimal. So what do you think about? What's optimal? 45 to 60 degrees is optimal for getting a good waveform. That's how I've heard it. I, quite frankly, I, I like the idea of having a standard angle in the lab, you know, whether you pick 60, 55 or 50, because it's hard to get anything under, you know, like 50 really consistently. I like it because it takes some variability out of it. Right. But I, but if you look at, you know, accreditation standards for labs, it just has to be 60 or under, but the angle cursor parallel to the walls. Okay. And also, I was going to go back to measuring the venous velocities. So renal veins, iliad veins, and portal veins would be three kind of exams where it would be, you know, more likely where you would be measuring venous velocity. Because there's criteria for those. Correct. Yes. Yes. Okay. Well, I think we're gonna, we're gonna call it. So I want to thank everybody for joining us tonight. Before we sign off, I just want to remind everyone one more time that this webinar was recorded, and it's going to be available online through the SVU website at no charge for attendees, but in about seven days. So wait a week, and then you'll be able to see it. And again, watch your inbox in seven to 10 days for the email from SVU to be able to get your CME. So don't, don't email the office, wait seven to 10 days. Then if you don't hear, if you don't get that email, you can reach out. And then please mark your calendars and join us for our next webinar, which is going to be on Tuesday, July 11th, where the topic will be fibromuscular dysplasia, FMD, what the vascular technologist should know. And our speakers on that date will be Dr. Heather Gornick and Melinda Bender out of Cleveland, Ohio. And then after the July talk, we'll probably take a break to prepare for the annual conference in August, the SVU conference in New Orleans. And then starting back in September, we're going to be hosting additional webinars, and they're going to be worth each like one or two CMEs. So please keep a lookout for communication from the SVU office on upcoming events. And thanks everyone for joining us tonight. Until next time, take care, stay well. Thank you, everyone.

eLearning

webinar

learning management system

Doppler

color

vascular ultrasound

Aileen French Sherry

B-mode images

Doppler waveforms

Q&A session