Hello, my name is Billy Zhang. I'm the Clinical Marketing Manager at GE Healthcare and a member of the SVU Products Committee along with Terry Case and George Bordejo. This program is being supported by an unrestricted educational grant provided by the Radiology and Vascular Ultrasound Divisions at GE Healthcare in cooperation with TIP TV. I'll be giving a brief overview of the SVU Professional Performance Guidelines, then Anne-Marie Kopinski will follow with a comprehensive explanation of the lower extremity arterial duplex evaluation. Anne-Marie will then return to demonstrate these techniques on our patient model. These guidelines were prepared by members of the Society of Vascular Ultrasound as a template to aid vascular technologists and other interested parties. The first portion of the guideline is divided up into three sections, the purpose, common indications, and contraindications and limitations. Lower extremity arterial duplex studies are performed to provide an overview of the location, extent, and severity of vascular disease in order to facilitate clinical management decisions. Common indications for these examinations are claudication, ischemic rest pain, and arterial ulcerations. Some contraindications and limitations that you may come across are the presence of ulcers, casts on the patients, and bandages. Next, we go into the guidelines themselves, and that is divided into seven sections. The first section is patient communication and positioning. In this section, you'll note that we talk about introducing yourself to the patient, explaining and educating the patient about the examination itself, and actually positioning the patient on the table for the exam, most likely in a supine position. Next, the patient assessment section, and that's when you perform your history and physical, when you look for any risk factors, you ask the patient if they've had this type of examination before, you look for those findings, and you find out if they have any surgical interventions that you may need to know about prior to starting the exam. The next section is the examination guideline. In that section, you will note the type of frequency you want to use, the type of transducer, the angle of incination that you would like to maintain, which is most likely going to be 60 degrees throughout the examination, and the vessels that you will be interrogating themselves. Following that portion, you will be finishing the examination, and the next section will guide you about the review and the findings themselves. You want to make sure that you have all the clinical and technical data before the patient leaves the room, as well as any exceptions to your protocols. Then you want to make sure that the presentation of the findings is appropriate for the interpreting physician and the referring physician. The next portion of the guidelines is the time recommendation, and that is divided into two sections, an indirect section and a direct section. In the indirect section, that's when you would bring the patient in, you would talk to them, you'd set up the machine, you'd put your information on either a worksheet or into the computer itself, and then the direct portion of the examination, where you would actually do the study themselves. Next, continuing medical education, as the last of the guidelines. Certification is considered the standard of practice. With certification, you must maintain CME and keep current with any advancements in technologies or changes to your laboratory internal protocols. With that, we're going to move to Anne-Marie's lecture, but before we do, I'd like to remind you that the current and complete SVU protocol guidelines are available online at www.svunet.org. Thank you. Hello, my name is Anne-Marie Kopinski, and I'm from Albany, New York, where I am the vice president of the Northeast Vascular Imaging Group, and today I'm going to talk to you about lower extremity arterial duplex ultrasound imaging. When we first see a patient that presents for arterial testing, we need to find out whether or not vascular disease is present, and this can usually be accomplished with a simple test called the ABI, or ankle brachial index. This can rapidly assess whether or not arterial disease is present. Once we find out that we have a patient with arterial disease, then we can go on to more direct imaging involving ultrasound. We can use that ultrasound to define both the severity and the location of the disease. I'll talk to you for the next few minutes about imaging in the lower extremity, both in the native arterial vessels as well as arterial bypass grafts. What can peripheral arterial ultrasound tell us? Well, certainly, we can find the exact level of disease. We can find out exactly which vessel is involved and over what extent, and that information is important to clinicians following these patients. This information can help direct further intervention to patients, whether it's medical management or a surgical intervention, angioplasty or stent, all that needs to be obtained so that we can monitor these patients and decide on the best course of treatment for them. Certainly, ultrasound can be used to follow disease progression, and ultrasound allows us to differentiate a complete vessel occlusion from a high-grade stenosis, which we can't do with other indirect forms of arterial testing. Ultrasound gives us the benefit of giving us anatomic information as well as physiologic information at the same time. Now, patients that come to us have a variety of symptoms. Certainly, many come to us who are claudicants or express claudication. Claudication is pain in large muscle groups like the calf or the thigh upon exercise. This can occur with walking or climbing stairs. Sometimes patients present with rest pain. Rest pain is pain at rest, as the name implies. Some people say that this pain wakes them up from sleep at night and is a burning sensation across their foot or ankle region. Sometimes we see patients with non-healing ulcers. In this diagram here, we can see this small non-healing ulcer on the toe here. Certainly, the most severe case of arterial disease produces gangrene. Sometimes we see patients who may not have arterial disease in the common form of atherosclerosis, but may have arterial trauma, and we have to evaluate those patients. And certainly, we use ultrasound in the follow-up treatment, either following intervention or surgery, to monitor these patients. Now, what can arterial ultrasound detect? Well, certainly, we look for plaque. We look for atherosclerosis. This is probably the biggest type of pathology or the most prevalent type of pathology we see. In this image over here, we can see the superficial femoral artery. Over here, it looks pretty healthy. Over here, we can see the debris in the vessel and the narrow flow lumen consistent with the stenosis. In addition to looking for atherosclerosis, we also look for aneurysmal disease or pseudoaneurysms, various types of vessel wall injuries, such as dissections, intimal tears, things like arterial venous malformations or arterial venous fistula. A little more or a little less common, more infrequent, is looking at arteries for fibromuscular dysplasia, but we can do that, and also looking for thrombi or emboli. When we do our arterial ultrasound, we may need to vary the frequency of the transducer for the examination. This is really going to be based on the body habitus of the patient. Usually, we can use a 5 to 7 megahertz linear array transducer to complete our arterial evaluation. Some technologists or stenographers choose to use a curved linear array when we're examining the vessels behind the knee. When we do this examination, we have the patient externally rotate their leg at the hip and slightly flex their knee, and this provides an adequate visualization of most of the vessels. We're going to use all the modalities we can from the equipment in combining the B-mode imaging or grayscale imaging, along with spectral Doppler and information supplied by ColorFlow imaging to complete our evaluation. In terms of sampling sites, most folks begin at the common femoral artery, obtaining both B-mode grayscale images and spectral Doppler, in addition to ColorFlow images as well. Some departments choose to scan further central to the common femoral artery and include the external iliac artery, common iliac artery, and aorta. The evaluation of these vessels will be discussed in another presentation. Today, we're going to focus on everything below the inguinal ligament. Once we're through the common femoral artery, we'll also include imaging of the profunda femoral artery, the entire length of the superficial femoral artery, the popliteal artery, both above and below the knee space, the posterior tibial, anterior tibial, peroneal, and dorsalis pedis arteries as well. In this figure, we see the arterial anatomy of the lower extremity. We begin here at the aorta, which bifurcates into the common iliac arteries. The common iliac arteries extend through the pelvis and then bifurcate again into the external iliac artery and the internal iliac artery, which used to be called the hypogastric artery. Once we move below the inguinal ligament, which is this green line here, once we get below here, the external iliac artery is now called the common femoral artery. Continuing further down, it bifurcates again. We'll look at the proximal portion of the profunda femoral artery, then scan all the way through the superficial femoral artery. Now, you can see in this diagram, the line becomes dotted, and that just represents the fact that these vessels now are posterior to the bones displayed in the image. So, coming behind the knee, the superficial femoral artery continues on down as the popliteal artery. The first large branch off the popliteal is the anterior tib that comes between the tibia and the fibula and courses over to the anterior lateral compartment of the calf. This extends down the calf and continues all the way down the calf, across the ankle, and then forms the dorsalis pedis artery. The other vessels we look at in the calf include the posterior tib. The posterior tibial artery courses more medial in the calf, around the medial malleolus, crossing onto the foot, and then connecting into the pedal arches. And the peroneal artery, which also used to be called the fibular artery, it's deep, it's next to the fibula, and actually can present some challenge to image properly in some patients. When we begin, we usually use a transverse orientation, again, starting right up in the groin, and we can see this sort of landmark appearance of the blood vessels. We see this large vessel in the center, which is the common femoral vein. To one side is the common femoral artery, and then on the other we see the great saphenous vein. And we're going to use a combination of approaches, both sagittal and transverse, to fully image the arterial vessels. Music Normally, what we expect to find on the B-mode image are vessels that have a nice, thin wall, smooth intima, a smooth intima medial boundary that we can appreciate. When we get disease, obviously we'll see plaque. We'll see this atherosclerosis. We may see varying levels of calcification in the plaque. We can also see wall thickening, or just a generalized irregular surface to the vessel wall. Here we see a nice, normal artery. And we can appreciate, here it is. There's no disease in the vessel. Nice, smooth vessel wall along here. Very clean and clear. And we can actually really appreciate quite well the intima medial complex here where we are at a good angle to the Doppler beam. This is what we want to see in our normal vessels. In this image, we see some color flow added on, and the color filling right out to the vessel walls. And again, no plaque visualized. We've got good color filling. But what's going on in this patient is something a little bit different. Up here we have the superficial femoral artery, and down beneath it we have the profunda femoral artery in a normal anatomic arrangement. However, we can see that flow is coming up the profunda femoral artery and then filling in the superficial femoral artery because the common femoral in this particular patient is completely occluded. The profunda femoral artery is an important collateral bed. There are a lot of small branches that come off of the profunda, and it really can make a big difference in patients with a lot of pathology. So here we see no evidence of plaque or disease at this level. However, these vessels are being kept open because of this collateral supply. Here's another color image of a normal vessel. And again, we can appreciate where we don't see the color, the thin wall here, nice smooth wall, and good color filling right out to the edges of the wall. We want to take and pay attention to our settings so that we don't see a lot of color spilling out over into the tissue. We want it just filling as it's shown here to the edge of the wall. Now, when we start to see disease, we can see all levels of disease, not just plaque. As I said, we can see here a nice segment of the popliteal artery that looks very normal, but then we see this dilated segment here consistent with a popliteal artery aneurysm. We not only see the dilation, but we also see all this debris in the vessel here, and that debris is laminated thrombus. That can present a potential risk to the patient. When we go into a transverse orientation, again, we can appreciate the thrombus and we can appreciate the residual lumen as displayed with the color filling here. Most of the time, though, we're going to see plaque, and that plaque will show up as we see here in this transverse view. And in this particular example, we see a lot of calcification, and the calcium is so dense it's causing acoustic shadowing. What we have to remember here is that not only to approach this vessel by scanning directly over the top of it, but alter our approach and change our angle so that we may come in from an angle from this side or perhaps from this side, thus avoiding the calcific shadowing and getting a full appreciation of the vessel wall. This particular patient actually has two problems. Not only do they have plaque, but they have some residual thrombus in the companion vein here. Now, spectral Doppler is how we make our diagnosis, so we need to be careful that we're doing this consistently patient-to-patient and examination-to-examination. We want to maintain a constant angle, and we should be somewhere at 60 degrees or less. And in the peripheral arterioles, we can use techniques during the imaging, which I'll show you later, to pretty much maintain 60 degrees all the time. The sample gate should be placed in the center stream of the blood vessel, and we should align our Doppler cursor to be parallel to the vessel walls. If we're measuring volume flow, we need to just adjust our Doppler a little bit and open up our sample gate to encompass most of the vessel. In terms of measurements, it's pretty simple. We pretty much just record the peak systolic velocity, or PSV. Some folks also note the end-diastolic velocity as well. Because there's a lot of variability in velocity, we pay significant attention to the velocity ratio, which is measured as the peak systolic velocity in an area where we suspect a stenosis, divided by the peak systolic velocity just proximal to this segment. And of course, if we suspect a stenosis, we'll also look for post-stenotic turbulence. Now, as I said, there are a wide variation of normal velocities and blood flow rates in individuals. These, due to the fact that flow to the extremity is not auto-regulated, but depends on the muscle mass and the tissue mass and the distal resistance, in addition to the vessel size, and all those factors will vary the absolute velocities that we record. As I said, too, we will see some degrees of changes in the spectral Doppler. We may see spectral broadening, and certainly we'll see post-synodic turbulence. And the telltale sign of a stenosis is a focal elevation and velocity with post-synodic turbulence. The criteria we use for peripheral arterial evaluations is pretty straightforward. There's not as much variability in the published criteria, and many people use the scheme that's displayed here on this slide. Normally, we expect peripheral arteries to display a velocity that is less than 150 centimeters per second. Sometimes in younger individuals, the velocities may be slightly higher due to the fact that we're dealing with very compliant vessels and healthy hearts, but usually the velocity is less than 150. As we start to see disease, we'll start to see elevations in velocities, and we'll start to see elevations in the velocity ratio. By the time the velocity ratio gets to a 2-to-1 level, that is consistent with a greater than 50% stenosis, pretty much in any artery anywhere in the body. So when we see a velocity of, say, 100 in the superficial femoral artery approximately, and then we get a velocity of 220, say, in the mid-portion of the superficial femoral artery, that's greater than a 2-to-1 ratio, and that is consistent with that greater than 50% stenosis. When we see a 4-to-1 ratio, or when we see a velocity that's over 400 centimeters per second, that's now consistent with greater than a 75% stenosis. And of course, if we have a vessel where we don't see any color filling or we don't see any spectral doppler, then that vessel is likely to be occluded. Here we see the classic example of a multiphasic waveform that we expect to observe in a peripheral artery. In the image here, we see this artery. We see nice color filling and no plaque, obviously, in this view. Here we have this multiphasic, what some people refer to as triphasic, based on the fact that there's three different components on either side of the baseline here. The first component here is where we have the systolic flow delivered to the vessel. This is the beginning of systole right here, and then we rapidly rise to peak systole. There's a narrow peak, and then we decelerate and start into our diastolic component. What happens is that bolus of systolic flow is delivered down to the vessel, where at the end of the arterial tree, there are the high-resistance arterioles. Normally, the arterioles are under vasomotor tone, so that there is resistance applied to that circuit. So what happens is this flow goes down, hits those arterioles, and then comes back. It gets kicked back as this wave right here, reflected back. It's called the reflected wave or the reverse wave component. That we see in early diastole. Then in late diastole, we see this third component to the waveform, and that's really the result of elastic recoil in vessels proximal to this segment. That recoil of the vessel propelling a little bit more blood flow down through the end of diastole. So this is what we really want to see pretty much in any vessel. In this example, we see this nice triphasic pattern again, and however, if we take a look at the image, it's showing evidence of early disease. We see this bright white here and along here. That bright white is consistent with calcification. So even though the velocities are normal in this case, this isn't a normal result because we do see calcification in the B mode. Again this multiphasic pattern is going to continue all the way down the arterial tree. Here's the popliteal artery here. Popliteal vein is on top of it. We see the popliteal artery again, a nice sharp upstroke, narrow peak, reflected wave, and then a little bit of antegrade flow in the end of diastole. And our peak velocities here are about 43, which are perfectly normal. Now sometimes we have signals that aren't so normal, and we may see signals that are really reflected of a high resistance bed, higher than normal, where we only see a monophasic pattern, and that's never normal in a peripheral artery. We'll see only flow during systole, only antegrade flow during systole, and no diastolic flow. And this is characteristic of when we're imaging in front of or proximal to a high-grade stenosis or occlusion, and this is an example of that. We're actually pretty much right at a stenosis here, and the velocities are about 400, so we know that that is consistent with a stenosis. But if we ignore the velocities and just look at the shape of that waveform, we can see something is wrong. There's no reflected wave, and that is consistent with a high resistance bed. That blood is working too hard to get down into those arteries, and so that is consistent with listening to either at or just in front of a high-grade stenosis. Well, also, we don't want too low resistance to signal. If we see a monophasic pattern with constant flow through the entire cardiac cycle, that is abnormal as well. And that indicates that something has taken and turned that high resistance bed into a low resistance bed. There's vasodilatation. Those arterioles have opened up now because the leg is hungry for oxygen. Something has changed in that circuit. And what changes is if we have a proximal stenosis or occlusion and not enough flow can get down, not enough oxygen is delivered, that will cause the vasodilatation, and then we'll see patterns like this. And here we have this stenosis. Again, we can see the plaque here. We can see the color aliasing. And if we Doppler just at the edge of this stenosis coming down below this area, now we see this monophasic pattern with constant flow through diastole. This is a low resistance pattern, and unless we have just ran our patient or our subject up a flight of stairs or on a treadmill, they should not display this low resistance pattern. In addition, if we take a closer look at the pattern and look at the slope or that upstroke, remember what I talked about a few minutes ago, the triphasic pattern with a nice sharp upstroke rapidly rising to peak systole? As we go through a stenosis, some of the energy stored in the peak velocity is converted to help speed up the blood flow through the stenosis. So we sort of lose energy through a stenosis because of frictional forces and viscosity changes, and that comes away from our velocity component. So now the blood is a little tired, and it takes a while to get to peak systolic velocity. So we can see this dampening. It's not straight up like we see here. This is shooting pretty much straight up. This is dampened now because we've used up some energy to get through a stenosis, and now our velocities are lower. Okay, well what about color? I talked about it a little bit. We use color imaging. Basically, it's a quick assessment of directional flow. We also use color and power imaging to help identify vessels that are occluded from those that are almost occluded or vessels that may have trickle flow because an occlusion may present only one type or a different type of a clinical outcome to something, a vessel that perhaps, say, has just a high-grade stenosis. They can be treated differently, so the clinicians need to know that. And certainly, color will rapidly identify areas of turbulence as displayed as color aliasing, and here we see an example of that. Over here, we have fairly normal color filling all the way out to the vessel wall, and then all of a sudden, something changes. We go from kind of red, you know, red to yellow color here to seeing this mosaic of color where we cross over from the dark reds to the oranges to the yellows to the white to the blue. That's color aliasing. Something has changed in that vessel, and in order to figure out what, we have to take the color off and look closely at the grayscale or B-mode image, and we can appreciate the stenosis here. Clearly, on the grayscale image, that corresponds with that color aliasing. Occasionally, we're asked to measure the diameter of certain vessels. This is often done in patients, perhaps, who may undergo some sort of an intervention or bypass. And this slide just illustrates the fact that we can measure both with a longitudinal or sagittal view as well as a transverse view. If you do it carefully, you pretty much get the same number either way. However, most folks prefer to take measurements using a transverse view with an AP orientation as shown here. And here we can see this small tibial vessel and the companion veins on either side of it. The other thing we may be asked to do occasionally is measure volume flow. Now, this is rather unique, but just to explain it to you in case you need to do this at some point in time, what we do is we obtain a Doppler spectrum across a vessel, and here we have the superficial femoral artery. We dial in manually the diameter of that vessel as shown by these calipers here. The machine, over at least four or five cardiac cycles to get a good average, we tell the machine to calculate the mean velocity. So the mean velocity multiplied by the area gives us our volume flow. In this case, the volume flow is 151 mils per minute, which actually is a pretty normal value for the superficial femoral artery here so that we're encompassing the whole vessel because we really want to know the whole cross-sectional flow and not just peak flow. When we're all done with our arterial exam, we can make a sketch like this. Sometimes clinicians like to see exactly what's going on, and again here we have the aorta and the iliacs and the inguinal ligament, and now the lower extremity arteries, and we can block in where things are open, where things aren't, where there's narrowing, and some folks find this kind of a sketch helpful. Now, what else do we look at besides plaque? Well, we look for aneurysmal disease, and I referred to this a little bit earlier. We can see aneurysms such as the one shown here, and again, we want to look at not only the size of the vessel and the residual lumen, but what else is hanging out there because this thrombus, this laminated thrombus, can present a risk for microembolism distally into small vessels. In this image, we have an extended field of view of the popliteal artery where we see, again, normal diameter here, the aneurysm, and then tapering back down to a more normal diameter, and I put this in here to show you that if we Doppler through the vessel, say at this point here where it's dilated, we're going to see some pretty unusual waveforms. We'll see a fair amount of turbulence, some retrograde pattern, because as the flow comes down, it's nice and laminar, and then it enters this dilation, and then we see a lot of reverse flow components and eddy flow and things like that that will disturb what we normally expect to see in a peripheral artery. Popliteal artery aneurysms are going to be the most frequent we encounter. They account for up to 70% of all peripheral artery aneurysms, and most are associated with atherosclerotic disease. Sometimes we can see popliteal artery aneurysms as the result of trauma or infection or vessel entrapment, and it's predominantly a male disease, 30 to 1 ratio. And often this aneurysmal disease is multilevel and bilateral, so we usually extend the exam if we find a popliteal artery on one side, we certainly look at the other side, and many departments will look further up at the common femoral iliacs or aorta to delineate if there is any multilevel disease involved. The symptoms that patients come in with aneurysmal disease are going to vary. Many times they're asymptomatic, sometimes they have focal pain, sometimes they have swelling due to venous congestion where the aneurysm actually compresses the vein and reduces the venous outflow a bit, and then sometimes they have pain associated with a neural compression syndrome where the aneurysm, again, is so large it's actually compressing on the companion nerve next to the vessels involved. It's important, again, to document whether or not that aneurysm is open with flow moving through it, flow that can carry debris further down and cause an embolism, or whether that aneurysm is completely occluded. In that case, again, it is going to vary the outcome or the procedure that might be performed on that patient. Here's another example, again, popliteal artery aneurysm where we've measured the diameter of the popliteal artery. In this case, it's about 1.6 or 1.7 centimeters, and again, this is the example which shows all this thrombus in here that puts the patient at significant risk for microemboli. ♪♪♪ Well, besides atherosclerosis and besides aneurysms, we can find iatrogenic injuries, and they include things like pseudoaneurysms, arteriovenous fistulae, dissections, intimal tears, and thrombi and emboli. Pseudoaneurysms are very common. They can occur following catheterization. We're seeing these more and more because we're doing more interventional techniques which require the use of large-bore catheters, particularly with stents and angioplasty. And what happens is we poke this hole in the artery. It's a pretty good-sized hole, and it doesn't heal, and some of the blood leaks out and extravasates into the tissue, kind of forming an expanding hematoma, and it gets trapped there by the loose connective tissue around the vessels. If we look at pseudoaneurysms on color, we see this very classic presentation of yin-yang appearance here, this swirling of the color flow. We know we're dealing with aneurysmal problem here. Here's illustration showing a pseudoaneurysm. Here we have the feeding artery coming on down, the neck or the track of the pseudoaneurysm leading to the sac of the pseudoaneurysm out here, again, showing all the color swirling. What's important to note really is kind of how big this is. Do we see any thrombus already? How does this track look? How does this neck look? Is it very wide? Is it very long or short? Some of that information, again, is important regarding the treatment of these patients. Over here, we see the classic two-fro appearance, that if we put a Doppler right in this section right here in the neck or track of that aneurysm, we're going to see a two-fro appearance because what happens is blood will come in, hit the dead end, and swirl back out. So we see blood coming in and blood coming back out. And again, this kind of image on color, this kind of image on Doppler affirms that we have a pseudoaneurysm. Now ultrasound has gone beyond just diagnostic modality, and we actually use it in a treatment modality as well in that ultrasound guidance is performed during the treatment of pseudoaneurysms. Years ago, we did these compression techniques where we basically got right over that neck or track and compressed with the head of the transducer to stop blood into the pseudoaneurysm. Now, most often, people prefer to use a thrombin injection where under B-mode visualization, we can see the needle, insert a needle, and enter into that aneurysm sac. We then turn the color on, inject some thrombin, and watch the thrombosis occur. It's really quick, it's very easy, and pretty much everybody tries to do this if they can over compression techniques which last and can take a long time and are a little more uncomfortable for the patients. Now another pathology we can see are arteriovenous fistulas. Again, this can follow a traumatic injury or cannulation or catheterization. Sometimes arteriovenous fistulas can occur that are congenital. In this case, they're usually called arteriovenous malformations. And this is just an abnormal connection between an artery and the companion vein next door. And if we suspect an arteriovenous fistula, we should look at the flow profiles in both the artery and the vein on one side and then on the contralateral side. Because if there's a fistula present, on the contralateral side, we should see normal phasic venous flow and a normal high resistance pattern in the artery. And then on the side that may have the fistula, we'll see increased flow in the artery and increased outflow in the vein. Here we have a loop rolling up here, which is showing this connection between an artery and a vein. Abnormal, and we see it occurring between these two vessels. If we were to Doppler in the artery proximal to this, we'd see a low resistance pattern. If we were to Doppler in the artery distal to this segment, we'd return to the normal high resistance pattern. The vein here, distal or more peripheral to this area, would display normal phasic flow. And the vein more central to this area would have an increase in the output caused by the fistula. Now I'm going to show you a loop of the Doppler pattern. And you can listen to this. And you sure can appreciate the high velocity, high volume flow that's screaming out through that little connection. That vein presents a nice, low resistance pathway. So the blood prefers to go out that low resistance pathway. And we can hear that turbulence and see that elevation in velocities. Now, we've talked about the native arterial system. But what about arterial bypass grafts? Well, this diagram illustrates a number of different types of bypass grafts. In the top half here, we see different arrangements of grafts from the aorta or the axillary arteries to the femoral arteries. And these bypasses around aortoiliac disease, again, will be discussed in another presentation. I'm going to focus on basically what we see when we examine these types of bypasses, which are bypasses with autogenous vein. You can also monitor bypasses that are of synthetic origin, be it Dacron or PTFE. There are a number of different types of grafts out there. Most of the examples in the presentation today will be autogenous vein. You can use vein either in an in situ orientation or a reverse vein orientation. And it's really important, before you begin your evaluation of a bypass graft, to get the op note so we understand what the inflow and outflow vessels are and what orientation that graft has been placed. Here, we see a vein bypass graft that's connected to the common femoral artery up here. And the popliteal artery down here. Over here, it's probably about the same area, maybe a little bit lower, almost kind of across the common femoral and the superficial femoral origin. And this time, it's a little bit distal, maybe into the tibial peroneal trunk, as shown in the diagram. So it's important to save yourself some time and understand where the plumbing is so we can evaluate the exact levels we're supposed to. The goal of bypass graft surveillance is really to detect a problem prior to occlusion of the entire bypass. It's much easier to fix a bypass stenosis than replace the entire bypass itself. About half of the time, bypass grafts will develop a problem. And when that problem occurs, usually it's within the first two years of the life of the bypass graft. The remaining third, give or take, will develop a problem after two years. Most of the time, the problem lies in the conduit itself, in the bypass graft. That's where the stenosis will develop. The remaining stenotic regions occur either in the inflow or outflow vessels, as well as the anastomotic region. Early on, when we see a stenosis in the first month or so, it's probably associated with a technical problem that occurred during the surgery, whether it's a retained valve or something along those lines. That's what we see early on. Within the first two years, we see problems that mainly relate to fibrointimal hyperplasia. It's not plaque. Plaque takes a long time to develop. This is a hyperplastic event that occurs and produces a stenosis. We may also see things such as a stenosis around a valve site or perhaps some sort of stricture within the graft itself. Later on, once we get into those patients that develop a stenosis after two years, we're really seeing progression of disease. We're seeing progression of the atherosclerotic disease in either the inflow or outflow vessels. Because remember, we're not curing the patient of their atherosclerotic disease. We're just bypassing around it. Now, we do need to figure out what type of transducer to use for these patients as well. It's going to, again, depend on body habitus and where the bypass graft was placed. Is it in situ, and therefore that bypass is going to be superficial? We may want a high frequency transducer, like a 10 or 12 megahertz. If it was tunneled deeper, we may want a 5 or 7 megahertz transducer. And whenever we're interested in scanning a portion of a blood vessel, we should start before the area of interest, through the whole area of interest, and then below the area of interest. And with an artery or an arterial graft, we're going to start in the inflow artery, scan through the proximal anastomosis, through the whole length of the graft. We can't cheat and just spot check. We have to scan through the whole thing. Out through the distal anastomosis and outflow artery. What do we see? We see the same kind of pathology we would in a native vessel. We'll see plaque. We'll see that hyperplasia. We may see thrombus. We may see dissections and aneurysms and pseudoaneurysms. But one thing that we'll see in addition are valve remnants or valve leaflets. This is a common problem that is observed in bypass grafts. Here is a normal vein bypass graft. And we can see it looks pretty healthy. There's nothing going on here. The walls look thin. There's no sort of debris built up as compared to this one. This vein bypass graft definitely has a stenosis. Whether this was a piece of leftover valve, whether this is platelet, whether this is hyperplasia, it doesn't really matter. We just have to find it and locate it and let the clinicians know. And then they can fix this. Whether it's something primary, where they just go in and cut the segment out, or whether they put another short segment in place of it, that's for them to determine. We just need to locate where the stenosis is. And I mentioned valves. And here's a few images, various images, of valves and valve leaflets that have been left over in an in situ bypass. So here we see a valve here. Almost looks like the whole thing. Here in transverse, we can appreciate another valve. And in this patient, we see another valve leaflet that really looks pretty much like they missed the whole thing. It looks pretty intact. And behind this leaflet, we've seen some thrombus laid down. So again, we need to find these and follow these. Not every one of these may create a hematoma. Use it in the native vessels. Can be used as an adjunct when we're scanning bypass grafts. We want to see the color filling out to the vessel walls. Look for uniform, smooth color. Obviously, if we see signs of aliasing, that may indicate turbulence or stenosis. And as I said earlier, here we see normal color appearance in a bypass graft. This is the distal portion of a bypass coming on down and connecting into a small distal artery. This is the distal anastomosis. It illustrates normal color filling right out to the edges of the wall. But it also illustrates something else in that most of the time, the bypasses are performed with the end of the bypass here sewed to the side of the artery. So it's end-to-side anastomosis. And that's done because sometimes we see a little bit of retrograde filling back up the native vessel, which may go out small secondary branches and collateral. So usually that's the appearance of a bypass anastomosis. As I said, color can be our clue that something's going on. In this example, we see good color filling here, nice red coming along. And all of a sudden, it changes. Well, it doesn't just change. Something has to make it change. And it's probably a stenosis. We can see the classic aliasing, again, going on in this vessel, where we have the dark red coming up to the orange, to the yellows, to the white, basically, crossing over that color spectrum into the blue range. That's consistent color aliasing. We need to take it off and look at the grayscale image and appreciate what's going on. The measurements that we do in bypass grafts are pretty much the same thing we do in native arteries. We're going to look at peak systolic velocity, again, end-diastolic velocity, maybe. We're going to measure the velocity ratio and look for areas of turbulence. The criteria are the same. There's really no additional criteria for bypass grafts. We're going to hope to see velocities less than 150 centimeters per second. And we're going to hope to see any small changes in the velocity ratio, producing ratios less than 2.1. Here's some examples of flow patterns through bypass grafts. This is the proximal portion of a bypass here, where we see the velocity of around 86 and a nice, normal biphasic pattern. Sometimes, in some of these patients, we don't see that third triphasic component because these are older patients, and their arteries have gone through normal changes to lose some of that elasticity. So we see a biphasic pattern versus triphasic, but it is normal. Continuing on down distally, our velocities are now around 59. So they've changed a little bit, but it will change along the course of a bypass, depending upon the size of the conduit used. If we use a piece of vein, the vein's going to change size as we move down the leg. So the velocities will change as well. Scanning out through the distal anastomosis, oftentimes, we may see a little bit of a step up across the anastomosis, but this should be relatively minor. And in this case, it only increased to 61 centimeters per second. And out into the outflow artery, we usually expect an increase in the velocity because usually, the vein is so much larger in diameter as compared to that target outflow artery that the velocities have to increase because we're putting more flow into a smaller tube. So the velocities have to go up. But we don't want to see a focal elevation. We'll see a sustained increase in the velocities. And in this case, the velocity increased to 93. So how do we tell when we have a stenosis? We can't just rely on one factor. We have to pay attention to the B mode or grayscale. We have to pay attention to what the color is telling us and also what the spectral Doppler is telling us. Here's an example of a bypass stenosis. Now certainly, we look up here and we see, wow, this color is in tough shape. There's a lot of aliasing going on. We see a lot of debris here on the grayscale. And as we listen to the flow coming towards us, we have velocities of about 300 centimeters per second. And what else? What about this waveform? We see all this diastolic flow. That leg down here is vasodilated because it's not getting enough oxygen. So we have a low resistance pattern that's consistent with a stenosis or imaging just distal to the stenosis as we see here in this example. And then if we continue just a little bit further beyond a stenosis, we see this kind of pattern. This post-stenotic turbulence, this is, again, the telltale sign that we truly have a flow-limiting stenosis where now the flow is completely disturbed. It's lost so much energy trying to work hard to get through the narrowed area that now we have this turbulent pattern. Same thing that we saw in the native vessels apply to bypass graphs. We never, ever want to see this kind of monophasic high-resistance pattern. Again, when we see this monophasic pattern with no flow and diastole, no reflected wave, we're in front of or proximal to a high-grade stenosis or occlusion. Now, sometimes in bypass graphs, we may see a low-resistance signal with lots of flow and diastole. This is very common to occur in the early post-operative period, and it could possibly due to a reactive hyperemia. Remember, these patients have critical ischemia. They've been without oxygen, so there may be a pronounced hyperemic effect that continues for actually a long time. You may not see a new steady state in these bypass graphs for about six months. Also, sometimes we may have residual arteriovenous fistula that would produce this low-resistance pattern. However, if we see a low-resistance pattern with this delayed kind of rounded upstroke, that's not due to hyperemia, and it's not due to an AV fistula. It's due to the fact that we are below a stenosis. Again, we want to see that sharp upstroke. We don't have it in this example at all. And if we look further north, we see certainly this signal in the common femoral artery with velocities of 610 centimeters per second. So that's a high-grade stenosis in the inflow artery, impacting the flow rates that we see through that bypass graft. So as I said, it may take about six months before these bypasses normalize, but they'll get there, and they will resume a biphasic or triphasic flow pattern. Now, we all look for a magic number to kind of clue us in as to when that bypass may be in trouble. Certainly one value that people pay attention to is the peak systolic velocity. And as we continue to see these patients serially through their life, if we notice a decrease of greater than 30 centimeters per second in the peak systolic velocity compared to a previous examination, something has changed in that bypass, and there's probably a stenosis likely, and we have to go find it. When we're looking at arterial bypasses, a lot of times we need to know when we should intervene or when that bypass should be revised. Most of the time, if we see a slight change in velocities where the velocity ratio may increase to about 1.5 and the peak systolic velocity may get up above 150, those types of bypasses we can monitor with more frequent surveillance. However, once the velocities get up to over 300 centimeters per second or the velocity ratio is now greater than 3.5, those bypasses will likely need intervention in order to maintain their patency. So to conclude, we talked a lot about lower extremity arterial ultrasound, and we know now that ultrasound can provide exact information on the location and severity of disease. In addition to looking for plaque and atherosclerosis, we can also identify traumatic injuries, and iatrogenic injuries. And the nice thing about ultrasound is we get all that anatomy and anatomic information as well as physiologic information in the blood flow rates that we measure. It really is an essential tool to properly caring for these patients in the post-operative period, so we do a lot of arterial imaging in our post-op patients. And when we're concerned about a segment of an artery or an arterial graft, we really need to scan through the entire area of interest to make sure we don't miss any levels of small disease or subcritical stenoses that we might want to follow more closely. And certainly the goal with looking at arterial bypass grafts is to identify a failing bypass before it completely occludes, and in many patients, we'll want to observe trends in their data to look for signs of trouble. Thank you very much. ♪♪ Hello, now I'm going to demonstrate an arterial duplex ultrasound exam of the lower extremity native vessels. We're going to start here at the inguinal ligament, or actually just below the inguinal ligament, the groin crease here, where we can see the common femoral artery. We have the leg externally rotated so we can open up the medial aspect of the thigh here. We'll follow down along the superficial femoral artery, continuing on down to the lower thigh. At this point, we know the vessels dive deep and come up behind the leg to form the popliteal artery. So we're going to move our transducer to a more posterior approach, coming up behind the knee, as I'm showing here, and we'll evaluate the popliteal artery in through here. When we get down to the tibial level vessels, we can pretty much see the posterior tibial artery from this approach. We may be able to evaluate the perineal artery, but more likely we'll come along where the lateral aspect of the leg and look at the anterior tib and the perineal vessels that way. We begin the ultrasound exam using a transverse approach. We want to make sure we have everything appropriately oriented. We have the transducers so that the patient's left side of the body is over here on this side of the screen to the right side of the screen and the patient's right side of the body is to the left side of the screen. In this view here, we see the common femoral vein in the center. We see a vessel here, which is the common femoral artery. And we see another vessel over here, which is the great saphenous vein. And if I compress a little bit, you can see the veins are compliant and compressible. And we have our artery over here. As I continue slowly down the leg, we can see the artery change from a rather circular appearance right here to a little bit oval to a little bit more. And now we have two vessels. And I think you really need to be able to appreciate this on the grayscale image first, get oriented to the surrounding tissue and what landmarks or other objects you may see. And then if you want to quicken your exam or you need a little bit of assistance, then you can throw the color in as a guide. So we're gonna come back up to the common femoral artery. And at this point, I'm going to rotate the transducer into a longitudinal or sagittal view. And we are right at the bifurcation here. This is the common femoral artery up here. This is the superficial femoral on top. And this is the profunda femoris on the bottom. And let's throw some color in so we can see exactly what we're looking at. I'm gonna make the scan area just a little bit bigger for purposes of this demonstration. So we can see a little bit. Now, things to note, our color PRF is probably pretty low. So I'm going to increase this a little bit so I can get a little bit more smooth filling in the color and not have any aliasing. Now we're gonna see that we don't see much flow over here at the origin of the profunda. And that's due to the fact that it's coming off at an inappropriate angle to get a good Doppler shift. So we'll move this box in a little bit. But while we're up here in the common femoral artery, let's take a look at the common fem. And we'd wanna save this picture and store this because this is telling our interpreting physicians there's no plaque here. There's nothing at the bifurcation. There's normal vessel diameter. There's nothing along the origin of the SFA and there's nothing along the origin of the profunda. So we have nice, healthy, normal vessels. We can even see a small branch vessel right here. If we put in our pulse Doppler, we're gonna align that in. Now, ideally we'd like to keep at 60 degrees or pretty close. So I'm adjusting the angle to 60. And then what I'm gonna do is take my hand and change my approach to the vessel so that I'm at 60 degrees and I'm parallel to the wall. And this maneuver is called toe healing the transducer where basically I would push in one side or the other on the patient's limb to achieve a good angle. And I think this is pretty good. We're here again at the common femoral. And I'll freeze that for a second so we can take a look at what we're seeing again. On the image, we see nice, clean image up here with no evidence of plaque. Down here in the spectral Doppler, we see a nice triphasic waveform. And our peak velocity in this example is about 100 centimeters per second. That's absolutely normal. In the peripheral arteries, we again would like to see something less than 150 centimeters per second. But what we really want to do is pay attention to the waveform here. And the waveform is showing a very sharp upstroke and a narrow systolic peak, dropping down with a reflected wave here that we expect to see in a high resistance bed and a little bit of antegrade flow towards the end of diastole. So that's our textbook example of a peripheral arterial flow pattern that we would expect to see. So now we'll come back. And again, to get oriented, I have an easier time myself was in terms of finding the vessels by approaching them transversely at first, finding them transversely and then rotating and bringing them out in longitudinal. So now we didn't really get a good view of the profound ephemeral. So let's see what we have to do with this color. And basically what we have to do is just play with the steering a little bit and play with the angle. My angle of my hand approaching this vessel. And actually I'm gonna try to see if we can center steer perhaps and see if that helps. But I think maybe we'll try steering a little bit more and seeing if we can get a little bit more filling into this profunda. And we're starting to see a little bit better at the origin across the origin here. So let's take a Doppler sample across the origin. Now at this point, I'm gonna change my angle a little bit. I'm gonna be a little bit less than 60. Less than 60 is okay. 60 is the best, greater than 60 is not acceptable. So you need to find a different approach. In here we see again, a nice high resistance pattern and our peak velocity in this example is 71. Again, well within normal limits. Really the only thing you need to do is really look at the beginning of the profunda and make sure that there's no plaque there. We're gonna come back and look at the superficial femoral. Now this is a long part of the scan because it's a long vessel. It tracks down quite a bit. I like to look at the vessels in grayscale and follow them in spectral Doppler because I like to really be able to see if there's any plaque. Now you can do this with color on and we'll go back later and show color throughout the whole area. But here we have the very proximal portion of the SFA. This is going to be another place where we're gonna stop and take a Doppler spectral analysis here showing the peak systolic velocity of 84. And again, very classic textbook, triphasic pattern with a nice sharp upstroke. This is a very nice, normal, healthy vessel. We'll get a little bit more gel here as we continue down the leg. You can use a lot of gel or a little gel, whatever your pleasure is. It does tend to make the patients cold so I don't like to use a lot of gel. We're gonna resume the exam now at the superficial femoral artery. At this point, we've looked at the common fem and we've looked at the profunda and we're gonna scan our way through the superficial femoral artery. What I'd like to do is just point out a few things regarding optimizing our image here. We certainly wanna make sure our focal zones, which on this system are represented by these little markers over here, we wanna make sure that they're at about the level we're interested in. Here's our superficial femoral artery. The femoral vein is beneath it. You can see a valve within the femoral vein here. But we're really concerned with optimizing the image of the artery. We don't wanna have our gain increase too much and I'm gonna increase the grayscale or B-mode gain. And you can see now that the vessel fills in with a lot of echoes, that's really not too helpful. We really wanna be able to back this down really so our vessel lumen is nice and black and clear. We'll do this with an overall gain. We can do this with the DGCs. We wanna make sure that, again, the focal zones are appropriate so that we are optimizing that image. If there were plaque here so we could bring out that plaque. So at this point, I'm gonna put in our spectral Doppler and we got a proximal SFA signal already. And we're still seeing this very nice, very healthy, triphasic superficial femoral artery signal. And we're just gonna scan down the leg. Now, a lot of times you do this, you don't even look at the patient, you're looking at the system and you're moving your hand to adjust the image so you see what you want. And basically what I wanna see is this type of an image where I've got the vessel right across the screen, okay? And I'm doing a little toe heel again so I keep a decent angle. Now, I think you can appreciate the Doppler signals change slightly, the sound that we're hearing has changed slightly, and that's because I'm at a bad angle right here, okay? The vessel is actually kind of curving a little bit the other way. So I'm gonna change my steering. And sure enough, we come back and we're getting a little bit better signal. We can hear it and we can see it. We can see how it's improved. And again, we're gonna keep it kind of lined up. We're just about at the middle of the thigh now. So I'm gonna take time and adjust the angle that I'm oriented to here with our Doppler beam. And I'm gonna catch a mid-thigh SFA signal. All right, we usually take a proximal, mid, and distal. And here we are at the mid-SFA with a peak systolic velocity of almost 88 centimeters per second. Again, well within our normal limits. Now, as we move distal in the thigh, just a little bit above the knee joint is where that artery is gonna start diving deep. So it depends person to person how much we're gonna see from this approach. And we may have to change our approach and come up from behind the knee. So I'm gonna come back again because I can find it nice and easy, transverse right where I was. And transverse right where I was. Here's my artery, here's my vein underneath. I'll press and I know that's the vein. Here's my artery. So I'll come back to a longitudinal view. Now, I'm really close to the edge of my image. So here's where I wanna optimize things again. First, I'm gonna increase my depth so I can see deeper in the leg. And as I did that, my focal zones dropped down a little bit but I can even drop them down a little bit more because I know I'm gonna go deeper. So we'll get a good shot here and we'll continue to scan down the superficial femoral artery. Now, one thing we can do is because we are getting deep and color is our tool to use to help guide us when we are trying to follow vessels. So let's put our color on. This is a perfect place to start. I'm gonna come back up here and we can see what's with this color. Well, we've got a little bit too much gain so I'm gonna drop it back a little bit because I don't want color where I know there's not blood flow. So we can see the superficial femoral artery. At this point too, we can see actually a nice branch vessel coming off the top right here. I don't know what vessel that is. Don't know if it has a name, but we can see it. And obviously, if there was a stenosis or occlusion, it would probably dilate and have some compensatory flow increases through it. But we're gonna continue to follow the superficial femoral artery. And now it really is getting deep here. And we can see as we move down the leg, how it's trying to get through that adductor canal to come up behind the knee. And I think you can see where my hand is in relation to his knee joint, where the transducer is. And this is probably as far south as we can go from this approach. So what I'll do before I leave here is actually get another Doppler signal and make sure it's nice and normal. And we're a little deeper. So that sound's gotta travel just that much further. And I'm going to up the gain just a little bit. Make sure I'm at a good angle. And actually, I'm gonna take the color off just for a second. And again, make sure my angle's good. Now, sometimes again, I'm not at 60 here, I'm only at 51, but we wanna be lined up to the vessel wall. I'm gonna take and move my caliper to where I think it needs to be. And our peak velocity now here in the distal portion of the superficial femoral artery is just about 71. So again, triphasic, sharp upstroke, no plaque, good color filling, everything corresponds. The grayscale, the color, and the Doppler are all telling us that we have a nice, normal vessel. Okay, so now we've finished exactly what we have to scan through the thigh. Again, we've covered the common femoral, profunda, and the superficial femoral artery all the way down to the level of the adductor canal. Now, with the patient's limb in this position with the knee slightly flexed, we can get in behind the popliteal space and approach the popliteal artery. And you can see my hand just sort of coming in here, and we should be able to see the popliteal artery pretty well. If I want to, I'm gonna pitch back and angle back towards, let me try to move my hand out of the way, angle back towards the lower thigh. And this is the approach we'll use to try to evaluate perhaps the distal SFA if we had any question, because this is where it's going to come through the adductor canal. And we'll pick up the popliteal artery, and we'll take some shots of that as well. So here we are behind the knee. We're gonna need a fair amount of goop, fair amount of gel, a little more gel. And I'm just going to increase the gain just a little bit so I can orient where I am and the vessels that I'm seeing here. All right, let's put our color on to help us a little bit as well. Okay, now behind the knee, what goes on? The popliteal artery, just increase the gain a little bit so you can see what I'm looking at. The popliteal artery is underneath the popliteal vein at this point. Here's the popliteal artery. We can see the flash. We don't see any color filling because he's just resting quietly here. But this gives me an idea of where I need to be looking. So I'm turning the transducer, rotating it into a longitudinal view. The blood vessel is steering back. So I'm gonna steer back my color box so that I can see that popliteal artery well. And now that I can see it a little better, I realize that I've got a little too much gain, so I'm dropping that back. And here we see the popliteal artery. What we'll do again is we wanna get a couple of Doppler signals. There's a lot of little branches that come off. This is a prominent place to have some pathology form. So we wanna make sure if we ask the machine to do too much, we can turn the color off and just grab our spectral Doppler. And what we're seeing is the same thing we saw before. Just change our angle just a little bit. We're listening and looking a little bit deeper. So we see our triphasic waveform. Let me move the cursor over to where it should be at the peak of this popliteal artery. And the peak velocity in this case is 48 centimeters per second. Again, very normal. And you'll notice as we go down the arterial tree, the velocities tend to get lower. And that's supposed to happen. Because we're trying to change the pulsatile flow coming out of the heart into a more continuous flow by the time we get to the capillary bed so we can have proper nutrient exchange. So we've shown you the popliteal artery and how we approach that from a scanning point. Now we're going to get into the calf vessels, which can be a little more challenging. As I mentioned earlier, we try to evaluate as much as we can of the posterior tibial artery, the perineal artery, and the anterior tibial artery. While I have the patient in this position, I'm going to start with the posterior tibial artery. And I like to approach it down low in the leg where it's pretty much all by itself, relatively small but superficial. And I can find it easily and then track it back up the calf. So I'm going to start down here by the ankle, again, using a transverse approach so I can sort of see what's going on. And obviously now we're dealing with something a lot more superficial, so I can drop my depth way back. And what else do I want to change? I certainly want to change my focal zones, because this is right up near the top of the image. And what I'm looking at is right over here. We see these three vessels, vein, artery, vein. And if I compress, the veins wink away at me. I know exactly where I am. We also see something else in this view. This is the great saphenous vein distally in the calf. But we're looking at the posterior tibial artery now right here. So there's really not much else in the way, and it's very easy to identify. So now once I've found it, again, we're going to look at it and appreciate the grayscale morphology using a longitudinal approach. Now remember, we've got two veins right next to each side of the artery, so we want to make sure we stay on the artery. So we'll put on some Color Flow and make sure we stay on the artery and that we're not really drifting off one way or another and including the veins. So if I just take that off again for a second, we can see beautiful thin-walled vessel, no evidence of calcification or plaque. We'll put our color on. We get nice color filling. It's not spilling out. We're at a pretty decent angle here. And lastly, we'll put in our spectral doppler. Now we had turned the gain up a bit because we were deep for the popliteal, and I guess that would probably be the best approach. Sorry. Let's get this. We're going to adjust the cursor. Again, 60 is great. We definitely don't go over 60. And we're at 59, which I think is pretty decent. Now, one other thing, our PRF is way too high for this vessel. We just slide over a little bit. If we lose it, we just slide back until we find it again. The reading physicians want a nice big waveform that they can see easily. So we're going to drop that PRF or that doppler scale way down. And sure enough, what do we see? That same triphasic pattern that we expect and we talked about so far. And our peak velocity at this level, which is relatively low distal posterior tibial artery, is about 74. And again, all the characteristics being the multiphasic pattern, high resistance, sharp upstroke, narrow peak, and so forth. So what we would do is continue on up as much as we could. And this is where, again, we may need to do multiple approaches. We won't spend too much time for the purposes of this demonstration, but I'll just follow it up in color so you can kind of see what we're dealing with. Again, the veins are going to be alongside, so we'll be rocking back and forth to stay on target. And we'll just have to make sure we stay within the artery. We're getting a little bit deeper, so I'm going to increase our depth again, make sure my focal zones stay pretty decent, and we'll just keep following it up, following it up. As we get a little bit higher with the vessels, we're going to have to, again, make sure we adjust everything so that we can see good color filling and angle the transducer so we can stay on these vessels because they're going to change their orientation a little bit. Let me come back down here where I had it a little bit better. This vessel is pretty small. It's probably only a couple, two, three millimeters in diameter, so it doesn't take much to slide off. So if you slide off the vein or artery, sorry, you slide off the posterior tibial artery, what you want to do is just come back where you found it, where it was easy, orient yourself, and then continue on up. We usually can follow this pretty far up in the calf, but again, in different patients, this vein can get, or this artery can get very deep very quickly, but we would normally continue the scan pretty much all the way up the calf, probably into about this level. The vessel will start to get deep, and then we'll have to change our approach and maybe come and use a more posterior approach. We'll try to get velocity measurements high up in the calf, mid-calf, and distally. If we want, we can also follow that posterior tibial artery distally behind the ankle down here where it goes down and feeds into the petal vessels of the foot. Now that we've done this, I'm going to change the position of the patient and approach the more posterior lateral aspect of the calf so I can see the peroneal arteries and the anterior tibial artery. As you can see, I've changed the position of the patient. I've had them flex their knee more and bring their leg up so I can evaluate the peroneal artery. The peroneal artery sits deep in the calf. Here is the fibula over here, and here is the peroneal veins and companion artery right here. Again, I'm showing you this just on grayscale so we can appreciate the vessels. If I compress the calf, I can wink the peroneal veins closed and see just the artery. Let's put in some color here to help us out and see. Now again, we're not really at the best angle, so I'm going to come in and actually come up and rotate in to a sagittal field of view. Here we see this beautiful little peroneal artery lighting up now. One thing I'm going to do is remember, as we get down into the tibial level veins and arteries, our flow rates drop as we get into the calf, so I'm going to drop our PRF, our color PRF, so I can make that fill up better. What I see I want to be able to translate to the reading physician so that they realize how nice and healthy this vessel is. If we look at the grayscale in between the color filling, we can see, again, no calcification, no plaque, and good color filling throughout this peroneal artery. I'm going to bring in our pulse doppler. I'm going to drop my pulse doppler scale, again, to make a nice, large spectrum for the reading physician to evaluate. We can see still yet, even in this very small, relatively distal calf artery, we still see that triphasic waveform, and we can appreciate here, again, the various phases, the vessel up here, nice and healthy, companion veins over here, and typically the approach that I use coming around pretty much lateral yet posterior is what we want to be able to evaluate these peroneal vessels. We'll follow this up to where it comes in to the posterior tibial artery, and that will really complete the assessment of the peroneal arteries and the posterior tibial arteries. Okay, now we're going to bring the patient's leg back down, the last vessel we have to look at, and we'll have them sort of roll their knee a little bit here. The last artery, we looked at the peroneal artery, we looked at the posterior tib, we're going to look at the anterior tibial artery. The anterior tibial artery actually courses through the interosseous membrane somewhere in this level and then comes along the outer edge of the tibia, coming down the calf, all the way down, slowly continuing down and coming across the ankle somewhere in this region, and it forms the dorsalis pedis artery. So now, where we can find it? Well, again, some patients we may find it easier higher up in the calf. Some patients we may find it easier lower down. We don't know. We're just going to take a look. We're going to come transversely again because I think that's an easy way to find a vessel, and we're going to have to remember what depth we're looking at, all right, where we are and how deep we need to be looking and where our focal zones are. And we can see some vessels here already. I just threw the color on, and we can see some things lighting up, and sure enough, that's the anterior tibial artery. We are done with the posterior tib already, and we can see that this artery is significantly larger than that peroneal. However, it is in great shape as well, and we can see good color filling. While we're here, let me take the color off for a second, and we're going to line this up and make sure we see everything we need to see with the vessel wall, make sure we can see the vessel wall, make sure that there's no plaque in through here. We want to make sure that there's no calcification. We use the color. It's very helpful in the calf as our guide. Put in our spectral doppler, and just like we did, we're going to rock back and forth. If we get lost, and I'm going to just angle a little bit better, toe heel with the transducer. Now our scale for our doppler is a little bit too low, so we'll increase it and obtain our doppler signal. This I would report as, well, actually this is pretty far proximal in the calf, but this gives you a good idea of what the waveform looks like. Our peak velocity, again, is about 54, and what I'd like to show you is as we follow the anterior tib up the calf, not too much further, it's going to take and dive away from us. So I'm just going to follow it up, and we can see how well the color helps us out here throughout all the tissue. And sure enough, what's happening now, it's dipping down away from us, going away, going away. We can try to increase our depth a little bit, and see if we can follow it, move our color box down, or maybe make our color box bigger. We don't want to slow things down too much, but we can see exactly what's going on here. And let me just stop that and scroll back just a little bit. Now, what's the problem with this image? Well, I wouldn't want to record this image and show my reading physician because my color PRF is too low. I had been adjusting it back and forth to get good color filling, and here we see a lot of aliasing, and nothing's going on in that very normal vessel. So let me come back and show you a more appropriate color image that we would want to record. All right, so here we are, and let's up our scale back up to a more appropriate setting for an artery. All right, see that difference? Just those few clicks made. We now see much more in the way of normal, nice, red color filling. I'm going to come back up, and I'm going to scan up, and we're seeing it come right down and go deep through behind the tibia to get back behind the knee. I'll just scroll back just a little bit, and we should see a little bit of speed up again around a turn. Blood will speed up as we take any turns in a blood vessel, and we see that represented in the color picture here, but this is a much better display of blood flow through this anterior tibial artery. We can see over here nice, normal artery. Again, thin wall, no evidence of plaque, good color filling, and now it's diving down to go back into the popliteal artery. So we've taken you through the tibial-level vessels, the perineal artery, anterior tibial artery, and the posterior tibial artery. We've also covered the popliteal and superficial femoral artery, profundofemoral artery, and common femoral artery, and that concludes our evaluation of the lower extremity arterial system. [♪ music playing ♪ Now we're going to take you through a demonstration of an arterial ultrasound on a lower extremity arterial bypass graft. Before we begin the ultrasound, we should talk to our patient and find out what type of bypass they had and get as much information as possible. I know from discussing things with this patient earlier that this is a vein bypass graft that was actually placed in the reverse vein position, and this is about four years old, and we should take a look at the patient's limb and the information that we can obtain for where the incisions are placed will help us out. We see that in this case the incision really starts quite high right at the groin crease, so probably the anastomosis is to the common femoral artery or very proximal superficial femoral artery. Then the incision courses along the medial aspect of the thigh, right along where the saphenous vein would have been naturally, coming down behind the knee, continuing on to the calf, and going all the way down here and ending just above the ankle. Now, in this region, the anastomotic options would be either the perineal artery or the posterior tibial artery, so we'll see where this goes as we scan. Now, usually we just apply some gel and we'll start transversely up in the groin, high up, so we can identify what vessels we have. And remember, we want to keep this oriented appropriately so that the patient's right side of their body is to the left side of the image, just as we would display any kind of medical image. And we see here up in the groin one vessel here, one vessel here, and if I hold still we can see that this one's beating, so we know that this is the artery, and obviously the artery should be lateral to the vein. If I go into a longitudinal view, we can appreciate the anastomosis of the bypass. Here's the bypass up here, coming in, coming down, and into the native artery. Let me just show you again in transverse, okay, vein here, and I'm slightly compressing the vein. You can see that here. Here's the artery. This is the common femoral artery at this point, and I'm going to move down really slowly. You can see that things start to change shape, so I know I've got something going on, and sure enough, here's the bypass coming off. If I continue just a little bit further, I can see now the artery has split into one vessel here and one vessel here. Let's put a little color on and see what that tells us. Okay. Now, I'm just doing this for orienting myself. Obviously, we know we want to scan color with a sagittal approach, but we can get an idea of what's going on. Vein here, artery here, coming through the anastomosis, all right, and this is now the profunda femoral artery right here, and this is the occluded superficial femoral artery. That was probably the reason why the patient needed the bypass in the first place. So, let's just go back to grayscale for a second and orient ourselves. We're going to follow this bypass using a sagittal or longitudinal approach, and I'm going to come up as high as I can, and we're going to take a look at the inflow vessel. Looks pretty decent, not any major degree of plaque. And we are going to want to keep our angle pretty close to 60 degrees, which I am right here, and I'm just changing the scale or PRF so we can fit the whole portion of the Doppler spectrum on the ultrasound image. And when we get a spot where we think we've got a good collection of cardiac cycles, we'll freeze that and record the inflow artery peaks of solid velocity, which is, in this case, is 148 centimeters per second. So, that's fine. Now we're going to head a little south, and we can either move our hand or move the cursor, whichever you like to do. Initially, I like to evaluate a bypass just using grayscale imaging and Doppler so I can see and look for any remnants or any type of problem with the bypass itself. We'll also evaluate it with color flow imaging as well. Here I'm kind of crossing over the inflow anastomosis, and I think you can appreciate both the change in the Doppler spectrum that we see here on the image. It's become a lot more turbulent, and we can hear that turbulence, and that's to be expected because we're making the blood change direction. It was happy and content going one direction down the common femoral artery, and now we've made it change. And it's going to take several vessel diameters before we get back into and resume a laminar flow. And we see that now down here. Now when I'm doing the live scan and following things, I may or may not have the angle exactly at 60 degrees. I'm looking and I'm listening, but before I go and take and capture the velocity, I definitely will make sure that I can get a 60-degree angle. And one of the ways we can do that usually is by toe-heeling the transducer, and that's something that a lot of folks don't know about. So I'm just going to show a little bit sort of towards the leg here. I'm going to show it in this direction for purposes of the demonstration, but by toe-heeling I mean pushing in on one end of the transducer or the other to kind of create an artificial angle to the vessel. So this bypass obviously runs along the leg in this fashion, so I'm going to maybe have to push in one way or the other to maintain a 60-degree angle, and I think that's important to learn how to do because you'll want to keep, again, close to 60 or certainly no more than 60, and by properly adjusting the transducer you'll be able to do that. Okay, so let's come back up here and let's just take a look for a second at the grayscale. What's it telling us? Well, there's really nothing going on, but one thing I want to point out right at the top here at the anastomosis, we see a little bit right here against the wall, and actually a little bit over here. Now this could be the exact level of the anastomosis. Perhaps this is something related to the suture line. It could also be related to the presence of a valve. This could be a valve sinus. Now this bypass is pretty old, so we may not be able to really differentiate the valve sinuses, but okay, let's take a look at it with color because I said we'd want to see what it looks like in color too. I'm going to come up, high up now, and let's see. I'm going to just increase my color scale just a little bit so I don't get so much aliasing. All right, and what are we seeing? We're seeing certainly red to blue because that's what our Doppler is. We see forward flow in systole, reverse flow in diastole. If we throw all three things in at the same time here, that's exactly what we see in the spectral Doppler as well as the color Doppler. Nice, normal color filling right out to the edge. Remember this. You want nice, normal color filling out to the vessel wall. You want to play with your color PRF or scale and the color gain to get appropriate filling of the vessel. You don't want to see this where we have the image over gained and we're seeing a lot of color speckle outside the vessel wall. We're going to drop the gain back so we really limit where we have the color filling within the vessel. All right, now we're just going to scan a little bit distally and you'll see that the color smooths out and we have a much more laminar pattern. Even here, a little bit, I'm going to drop the gain back just a little more and we can see how we have some nice, normal filling. All right, so I'm going to take the color off at this point and we've already looked at the proximal anastomosis and we've looked at the inflow artery and we're going to scan down through the length of the bypass graft. Again, I'm going to use some toe-heel maneuver to keep myself at about 60 degrees. Now, I like doing it live in a duplex mode where I can see the grayscale image and listen and look at the spectral doppler. So I'm just going to move real slow down the leg, keeping the bypass lined up. What I really want to see is the bypass from one edge of the screen to the other. If I see that, then I know I'm basically right over that graft and I'm not oblique to it. So continuing on down, we see nothing on the grayscale. It looks beautiful. It's nice and healthy. And we're just moving along. And you can appreciate, you can hear the doppler. You know that that's good flow. I'm just getting a little bit low here on gel, so we'll put a little more gel. I don't like to use a lot of gel because it tends to really cool off the patients a lot, so I just kind of use it a little more sparingly than some folks maybe. So again, I've used that toe-heel. If I start off with just putting the transducer on the skin, you'll see here that the vein, that bypass graft, is pretty flat. And my transducer is pretty flat to his skin. But if I just push just a little bit on one end of the transducer, now I've created an angle which will give me a better doppler shift. So we'll come back here. And we're going to scan all the way down, looking and listening. And right now I'm about at the middle of his thigh. So let's take another doppler velocity at this point. One thing to caution, particularly if the vein or the bypass is very superficial. And again, this is reverse vein but placed very superficial. So this reverse vein bypass, if I push a little bit too much, I'm actually going to compress it a little bit. Maybe you can appreciate how I've changed that diameter just a little bit. So we don't want to press too hard. Now it's kind of angling a little bit better in the opposite direction. So I'm going to put my doppler in and I'm going to change the steering to come back because I'm going to let his anatomy work with me. I'm not going to try to fight it and come in from a different approach. We're kind of mid-thigh, but let's see what's wrong. I need to adjust the doppler scale or PRF so I can fit the whole waveform on. And we'll take and we'll capture this as a mid-bypass velocity or mid-graft flow, and in this case it's 86 centimeters per second. So that looks fine. We'll continue on down. For the most part, it's peak systolic velocity or velocity ratio. If we saw an area with a transient elevation in velocity, we would take a more closer look at it. Now again, as I'm doing this sort of sweep, you'll see that I'm not aligned to the vessel wall right here, but if I were to take the velocity measurement at this point, I'd work a little bit better and get a little bit better angle, but I'm doing the survey. I'm doing the sweep down the leg to make sure that I can see everything I need to see. A little more gel. We're coming down to the knee. Sometimes, depending upon the position of the bypass graft, in his case it doesn't run too posterior, so I can see things pretty well here and I can fit in the transducer just fine. You can see where my hand is. If it were a little more posterior, I would have him bend his knee a little bit and rotate his leg out a little bit, but it's pretty good so far. And again, maybe through here I'll switch back and angle the other way. Again, working with the natural curves of that bypass in his leg. Wonderful. Nice, clean. The vessel wall is absolutely clean. There is nothing going on there. No residual valve pieces left out. A nice, thin intima. We're getting pretty superficial now. So one thing I'm going to see if I can just move up. I guess I'm up as high as I can get the focal zone because we want to make sure that we keep our focus to the level where our area of interest is. So let's come back here. And now we're coming down below the knee. And of course at this point the bypass is going to curve a little bit anterior, kind of coursing a little bit along near the tibia. And one thing is some folks find it hard to start out in a longitudinal scan and find the bypass because here I am by his knee and I'm going to go back and I'm going to go forward and up. There it is. But it's also very quick to just put the probe down in a transverse fashion and wow, there's bypass right there. No looking around because we can kind of see a broad range. So when we get it in view, then we can go long on it again and then continue to follow. And again, that vessel wall is very healthy. So we would continue to drive right on down, looking and listening. If you do this live like this in a duplex mode, you won't miss anything. If you're going to spot check, have it live and then stop the image and take a Doppler and move and do this down the leg, you're going to run into trouble. You will miss stuff. So I like doing this live. Now we're getting down near the end here. Let me take the Doppler off. We can clearly see that the bypass is curving away. Here we are pretty flat and straight. Here it's starting to curve away. So we're coming down to the distal anastomosis at this point. Now what's going to happen at this curve? Things are going to change again, right? We know when we go around a curve in our car how we can feel the force when we swing around that curve. That same force is acting on the blood cells in this blood vessel around this curve. So we're not going to want to listen right at this bend or even right here. So I'm going to come back up here just a little bit maybe, and let's take another signal of our velocity, just making sure we can record something here. I'm just lining up, seeing what we can get for an angle, trying to keep it somewhere around close to 60. And then our velocity here in the very distal bypass, pretty much mid-calf, is approximately 68 centimeters per second. Okay, so we're almost to the end of our scan. And again, I'll go back and we'll look at it in color as well because many people choose to evaluate the bypass in color as well as Doppler. And I think there are adjunctive procedures, and they can each give you information that's important. So we just put a little more gel, and here we see our bypass curving away. Now here I'm going to show you some color at this point because I think this is helpful following it down. And one thing we can see right off the bat is this beautiful anastomosis. And let me just freeze that for a second and scroll back and talk about this just for a second before we get too much farther. Here we have the vein bypass. This was the saphenous vein. It's now an arterial bypass. And the end of this vein is sewn into the side of this vessel. And from the depth and the position, I know that this is the posterior tibial artery. This is the distal posterior tibial artery here. Right through here is the anastomosis. And this up here is the native, more proximal posterior tibial artery. They leave this just like this so we can get a little bit of retrograde flow up into the vessel to perfuse any branches or collaterals that may be present. So that is really what we'd like to see, and we know that that's functioning well. On the color image, we see no real signs of any aliasing. Again, good color filling all the way out. Let's go back and let's take a look at it in B mode or grayscale and see what the grayscale tells us. Okay, I'm just going to freeze that and again come up here and let's talk through it. Here's the vein, big, beautiful, healthy. Here's the more proximal posterior tib. We'll come down a little bit and get a different view here of the distal posterior tib. It's a little bit out of plane, but what I wanted to show you here is we can see a little bit of stuff right here against the back wall of the artery. And that's not uncommon to see a little bit of, this is probably a little bit of hyperplasia at the anastomosis. That's why we make the anastomosis as wide as we do so that we can get a little bit of hyperplasia and it still doesn't become flow limiting. That's exactly why we angle it like that so we see that normal anatomy and can expect a little bit of change here. If we come down just a little bit further, we can see the pretty small but patent posterior tibial artery right here. The important part is we're going to back up a little bit. We're going to put our Doppler in because we already did the color. We saw that the color looked good. My angle is off, so I'm going to adjust it a little bit. Sometimes you'll know, I guess it's better the way I had it, sorry. And we'll see our Doppler. And we're going to gradually, I'm not going to move at this time because I've got a pretty good view, so I'm going to move my cursor. Right on through the anastomosis, we'll listen to the Doppler. No real shift here. And now we're getting out into the distal posterior tib. I'm going to just reposition myself so I can get a good angle and get a really good Doppler signal. We saw no shift in velocities right on through the outflow anastomosis, and that's fantastic. That's exactly what we want to see in a normal bypass. So again, coming back up and getting oriented. There's my bypass looking humongous and great. And coming on down. And now sometimes you can have just enough calcification, et cetera, that somewhat limits your view in the distal tibial vessel. So I'm going to use my color to help me out here. And I'm going to try to get a decent angle. Again, toe heel just a little bit. And I didn't touch any of the equipment settings. And you can see just by moving my transducer just a little bit how I got better color filling. And here we are in the distal vessel. Of course, we want to get a little better angle that's more aligned to the vessel wall. We're at 56 degrees, so we can even play a little bit better because believe me, when you go back and look at these things, you'll be amazed at how close you thought you were and how far off you really were. But I think this is pretty good. Let me just see if I can get a really good shot here. Okay. And we see now obviously when I froze the image, I'm frozen at a different point, so we're not seeing the color. We would probably before we capture this to send to our packs or to give to our reading physician, we would scroll back and we'd try to match up a decent color image with our Doppler. But for the demonstration today, I just want to show you our velocities. And here in the outflow vessel, which is the posterior tibial artery, the distal posterior tibial artery, we have a velocity of 108 centimeters per second. So it is really perfect. There's no focal elevation. We scanned through there both in color and spectral Doppler. And really, that is a complete exam. We started in the inflow vessel, which was the common femoral, went through the anastomosis, went through the entire length of the bypass graft, out the distal anastomosis, and out into the distal artery. We evaluated segments of it in color. We looked at the whole thing in spectral Doppler. And as I said, some people will scan the whole thing in color as well. We can show you that. We've got a little time. We'll just show you how we would follow it in color. And again, we're going to use toe heel to make sure we can see a good angle. Now, we looked at the beginning already, so I'm not going to start all the way up at the proximal anastomosis. But we'll come up here and we see beautiful color filling, not spilling out, maybe just a touch. We could maybe drop the gain back a little bit. I usually try to adjust the scale so that I see just what I'm seeing here. I don't want the scale too low because if I drop the scale too low, what am I going to do? I'm going to artificially induce some aliasing maybe at some point, and that's what I'm doing here just to show you for demonstration purposes. I've dropped the scale back way too low. This is way too low for an arterial setting, and we are seeing color aliasing at peak systole. So we'll come up and we'll make it so that we see nice laminar filling of this vessel. And we can scan down in color, as I said, as well. But if we see any areas of turbulence or aliasing, we'll want to turn the color off and take a good look at the gray scale. And you can see you can actually do this pretty quickly, scanning down the bypass because we're just not as worried about our angle. We can angle it, and now again a little back because the vessel is turning. And we're just continuing on down, down, down, down, down by his knee again. I'm just going to reposition my hand and get my gel bottle out of your way so we can take a look so you can see how I am here. And again, this is a very healthy-looking conduit. Now we don't want to scan like this routinely. Why? Because the vessel is angled in one way and my color box is the opposite. We want to work with that angle again. So when we're doing bypasses, this is another point to consider. We're constantly adjusting what angle we're steering, both our color and spectral Doppler. It's not a straight tube, as you can see today. It's curving in various directions. Now, what is this? I've got the gain too high. I've got some bright tissue back in here, and I'm getting a little artifact. So we'll want to take and drop the gain maybe a little bit and get rid of it. And there it goes. It's gone. But I'm moving, so obviously the motion is impacting the color a little bit, and we're coming down, scanning all the way down, down his calf. And you'll notice that when you get doing this, you won't really even be looking at your hand. You're going to move your hand to see the image you want to see on the screen. Here we are back at that anastomosis now, and we can see that beautiful anastomosis. And remember now, I dropped my scale from what it was previously, so I'm seeing a little bit different color this time, and that's because my PRF is different. But here we see pretty decent color filling, and we're right on out into that posterior tibial artery. And depending on your protocol, we usually only follow just a few centimeters down into that outflow vessel. So that is how to scan through an arterial bypass graft. We're going to take our velocity measurements, probably no fewer than five or six measurements at least. Inflow, outflow, anastomosis, and mid-graft, but some folks would like inflow, outflow, proximal, mid, distal. That's probably more appropriate, so that would be seven measurements of peak systolic velocity. Color images, grayscale images, spectral Doppler, all three things need to be documented so we can make sure that there's no particular variation or artifact that we're misidentifying when we do this exam. And that is how you complete an arterial ultrasound of a lower extremity arterial bypass. Thank you very much. ♪

Billy Zhang

Clinical Marketing Manager

GE Healthcare

SVU Professional Performance Guidelines

lower extremity arterial duplex studies

vascular technologists

patient communication

examination guidelines

Anne-Marie Kopinski

lower extremity arterial duplex ultrasound imaging

ankle brachial index

ultrasound

plaque

stenosis

Doppler measurements