Thank you doctor Hearth. Good morning to everybody. Um I really have no disclosures related to this discussion. So when we talk about arterial duplex this can be a long protocol particularly when done for appropriate indications. It's not uncommon that we'll see bilateral lower extremity arterial duplexes ordered. and these can be upwards of 45 50 images and clips being done by the by the technologists. Um The study should include both transverse and longitudinal B. Mode as well as color Doppler as well as spectral Doppler through your areas of interest from the proximal to the distal segments. And then obviously our goal is to identify the abnormalities, areas of velocity shifts etcetera. And I'm gonna talk a lot more about that a little bit later. We use all of the different tools available to us in um in the vascular lab to evaluate um uh these patients. So our goal of testing really is to local lives those an atomic abnormalities. And help us define the nature of the process as well as determined at least from a from a duplex standpoint. The hemo dynamic dynamic impact. Now that doesn't necessarily correlate to a physiologic impact. And that's important to recognize. We're looking at at velocity as well as looking at the arterial structures and we want to identify plaque also branches collaterals things that may be contributing to the underlying path of physiology. This is a very accurate and well accepted method and it compares well to contrast angiography. M. R. A. As well as C. T. A. So it will give you when in the done in the correct hands. Really valuable um an atomic uh information similar to our other uh other imaging. So what are we looking for? We're looking for our hemo dynamic information. We really need to pay attention to wave forms. We're looking for velocities, velocity shifts. But again that doesn't necessarily correlate with physiology. So at the end of the day you have to correlate this clinically what's going on with what's going on in the patient. And it frequently should honestly be correlated with your noninvasive physiologic testing that we just heard about from an an atomic standpoint. We can see and identify classification. We can see and identify plaque. However plaque characterization is not well standardized and we can't see through classification. So you may have areas of signal drop off anatomically early thrombosis. Maybe echo lucent. So you have to be very careful with that. Um we need to make sure that our images are obtained. Well uh there are some technical limitations if we can't see the structure. We can't necessarily provide our best assessment. Now that maybe because we have calcification maybe because it's outside of the field of view or maybe it's covered by an early bandage or dressing or um vac any number of different different things. This is not done as a diagnostic or screening exam for patients with peripheral arterial disease that should be done using our noninvasive testing. This really is done for an evaluation and progression of arterial disease. When we're talking about arterial obstructive disease, aneurysm disease dissection or in the setting of traumatic injury. It can help us evaluate the sub acute limb ischemia, occasionally acute limb ischemia. But I think you have to be very careful there most of those patients. We really shouldn't be delaying our time to intervention. Waiting on a duplex. Um We can follow our stable disease like vasculitis or arterial open these and look for progression of disease. And then in our interventional patients it can actually help us determine interventional strategies, particularly when you have to have some contrast avoidance. Um So in patients with chronic kidney disease and patients in whom may have a contrast allergy etcetera. Um It can also help us with evaluation and surveillance in both the sort of near term as well as long term following endovascular intervention and bypass grafts. So what are benefits? This is a non contrast exam. It's non invasive. It's very well tolerated and there are really no known patient harms. We still adhere to the allora principles that dr Evans talked about and it does allow for serial imaging across time without again, the contrast exposure without the radiation exposure etcetera. On the other side of that already discussed, it can be a very long test if you're looking at an entire lower extremity or or even worse from a technology standpoint of bilateral lower extremity exam, it is somewhat technologist dependent. Again, no physiologic information um can really be obtained from this. You have to, you have to correlate the findings clinically. How do we optimize this exam? I think you have to identify first the indication for the exam. It really is gonna help you obtain your best information. I know that if this is sort of routine, if you will or if it's been done being done because there's a change in clinical characteristics. Are you looking for something new um that may impact the patient? You need to have some knowledge about the underlying process. Is this routine arterial disease or is there a concern about a dissection? Is there concern about some form of trauma etcetera? And then look at your previously available imaging to help you with comparator, make sure that the room is quiet and that you're following your typical optimized protocols. Now, these are some recommendations and we've heard a lot about how to optimize exams and um how to optimize your Doppler imaging from doctor Evans a little bit earlier. This came from a manuscript published by Esther Kim and colleagues from the Society of vascular Medicine. And it actually, if you've not read this manuscript is very thorough, it's very complete and really worth a very long read. But it will it will help you, I think optimize from an arterial and venous standpoint. Many of the things we've talked about today. Alright, so again, determine what your need for the exam is. Review your procedures that may have been done where the procedure took place in the vessel. And then was that procedure successful or was it complicated because that's gonna help you also know what you're looking for when you're doing this Following of surgery or a bypass. It's really important to know what the bypass was. What was the conduit? Where's the bypass? Where's your proximal and distal and systematic segments? What's the nature of the anastomosis? And then you have to understand the difference between early potential complications and late complications. So will frequently not infrequently do these exams fairly early after a bypass has been done. You're looking for things different such as flaps, dissections, maybe paragraph fluid. Whereas late you're going to be looking for things like intimate hyperplasia areas of stenosis, retain valve structures, an aneurysm, a degeneration of the graphs, things like that that are going to impact outcome. Now we've talked a little bit about wave forms and the exam itself is going to use all of your different characteristics. So we're gonna pay attention to Doppler waveforms similar to what we heard about. We're gonna pay attention to the spectral characteristics of the wave forms as well as the overall velocity velocity shift and velocity ratio. Your criteria may vary between labs and I'm gonna show you um actually on on this slide and the next slide, different criteria that maybe differently used. So in in our lab, we tend to use that criteria in bold of a 50 greater than 50% stenosis. Um however you can see on the bottom table. These were criteria from a publication in seminars for vascular surgery. And these are the criteria published in in Dr Kim's manuscript. So the criteria do vary. You need to understand what the criteria are for your lab with that being said. None of them are that terribly different from each other. So usually paying attention to Velocity ratios and doubling of the velocity being consistent with more than 50% diameter stenosis. Some of the Some of the criteria also include a quadrupling or a fourfold increase in velocity being characteristic and typical for greater than 70 or greater than 80% stenosis. So it's more severe stenosis. Now, normal wave forms we consider try physic or again, as we're talking about movement towards multiphasic, as far as the terminology goes, that usual, velocity is between 80 and 180 cm/s. And you want to see laminar flow. I always make the point to my trainees, you will see a lot of normal venus duplex, you will see a lot of normal carotid duplex. You should not see as many, in my opinion, normal arterial duplex because it's not done as a diagnostic, it should really be done in patients with underlying pathology or path of physiology. So I'm being able to identify and recognize what's normal. So when you see the abnormal becomes very important. Um Similarly for plaque I've already mentioned, we can't really characterize it. You do need to identify it. You should comment on it. Um You should uh discuss whether or not there were calcifications that limited your examine your ability to fully incinerate the vessel. In many cases your plaque may be suggestive and associated variants of turbulence color. A listing that will direct your further evaluation with your Doppler characteristics etcetera. We do have clues that we may be um facing a stone arctic conditions. So, a change in wave form. So you can see these wave forms are no longer multiphasic. They're more mono physics. So if you see a mono physic external iliac artery, you know that there is likely a more proximal stenosis or occlusion and you need to go back and find that. Or look for that uh delayed upstroke dr kim's manuscript refers to an upstroke delay of greater than 140 milliseconds that can actually be um measured with the calipers in in the lab. If you so choose to do that retrograde flow, you can see on the bottom right there, you have a retrograde profundity or deep femoral artery that's gonna suggest that you need to be looking for again, a more proximal stenosis and then collateral. So it's not uncommon. If you have a proximal stenosis, you're going to see collateral flow and re perfusion distantly through large collateral pathways. So you can gain a lot of additional knowledge without necessarily seeing that stone optics segment per se. So how do we evaluate cyanotic lesions? You can see this as a subclavian artery. You've got relatively what appears to be laminar flow. Although you do see some spectral broadening, you do see not that typical trifle waveform, that's a little broader than normal. Although you do have a reversal of flow Um more distantly, you'll see that the velocity shift is fairly remarkable. So you go up to a velocity of greater than 400 cm per second consistent with a fairly high grade stenosis. You can see the color aliasing the spectral broadening and then post hypnotic. You see the turbulence in the axillary artery. What also you take away from this picture, This is the mid distal and axillary segments, right? That's unlikely to be peripheral arterial disease. So you have to ask yourself, So what is this process? Anybody want to take a guess? Here's your here's your uh Doppler seen through the area. No takers. This is a lady I follow with a large vessel vasculitis and you can see that the wall of the vessel. And if I can go back. Uh Let me see if I can go back here. You can actually see that wall of the vessel that very um sort of thickened if you will um segment, particularly on the on the far left segment. You see the thickened wall of the vessel. I followed her for a long time with a fairly significant degree of clinical stability and she's not otherwise. Uh symptomatic, here's another subclavian. So looking at the left subclavian, you have two images normal or abnormal. So these are abnormal, right? You do not have a normal try physic waveform with a with a nice flow reversal. And if you look much more proximately you'll see that there was a high grade stenosis um that the tech was able to uncover by using the curvilinear probe and getting really very proximal in that vessel. So again just looking at the wave forms if you look at that first if you look the first wave form on the far left, there's not a lot of turbulence, there's not a lot of color aliasing but you do see the little bit of delayed in the upstroke. Um And again a savvy technologist is going to come back and get you that appropriate. Uh stay. Not IQ image very important to know. Now an acute disease. Again we don't do a lot of uh arterial duplex for acute arterial exclusive disease. And I don't think it necessarily behooves the patient to do that. Um But we will get called occasionally this is a again another subclavian on the far right, axillary artery. And then you'll see a breaking occlusion. So on occasion we may get called particularly in the I. C. U. For somebody with a hand and you know a scheme of canned or something like that and what you'll see an inclusive disease as is a typically a higher resistive than usual type of pattern. And as you get closer to that stenosis. Now we're getting that staccato type image or what is essentially a vascular thump up against that inclusive segment. Now bypass grafts come in all different forms and sizes. This is a typical fem fem bypass graft. We don't do many of these. But you can see that the conduit is that typical ringed type conduit that's gonna create a little bit of artifact in your imaging. So you want to know what type of conduit you're working with when you do a bypass graft assessment. You go from the native vessel through the proximal anastomosis serially throughout the bypass graph and then the distal anastomosis and the outflow vessel. Alright so this is a very normal if you will fem fem type uh type bypass graft. Now this was a uh them two anterior tibial artery bypass graft and um a little bit atypical or unusual. This was a P. T. F. E. Graft and you can see the material of the of the P. T. F. E. So you know that this is not a not a vein graft. Um And I will just say suffice to say that while the velocities are a little bit low. Proximately the wave forms are typical wave forms. They are multiphasic. The flow is very laminar there's not a whole lot of concern in this graft until you come to the distal anastomosis. And you see the shift, you see the color aliasing and you see the turbulence. So you do want to again make sure you're assessing this graft uh completely proximal to distal. This would be consistent with uh some concern at the distal anastomosis and needs to be communicated back to the the vascular surgeons um Similar for stents. You want to make sure that you know what segments were stunted. You wanna have a good assessment of the inflow. You want to make sure your Doppler going all the way through the stent. We look at this um in in B. Mode as well as followed by color. Uh Doppler and then go through with your spectral Doppler. And you can see in the The velocity shift that starts in the uh top middle bar there you got. You have a shift that goes from 50 cm/s to 177. Um the tech has marched through that a little bit to get the maximum velocity of 192. So a significant shift. And then following that Doppler shift, you can see the waveform on the bottom left that has that delayed upstroke. It's representative of a post cyanotic type wave form. Um And then as they kept going through the extended segment, you can see that again at the at the distal on the far right bottom segment there's another velocity shift. So this represents basically tandem Stenosis through this extended segment. Um and the velocity shift at the at the far right is actually greater than 407 cm/s. So a very high grade stenosis in that area. So you want to make sure that you've you've documented this. It can be sometimes a little bit difficult to interpret tandem stenosis, particularly if they're very close. These are obviously spaced out. Think you can really reassure your your intervention list that they have, they have multi level um stenosis in this area similar to bypass grafts, stent criteria can be a little bit different between labs and you need to know what your lab is. So this is a manuscript that shows the stent criteria at four different institutions. Now, what you can take away from this is again they're not remarkably different But they are different. So you need to know what your criteria are. I think for the purposes of the exam um you know you can you can reliably uh use um that that roughly 200 cm per second in a doubling or a quadrupling of velocities in most of those stinted segments. So in conclusion, I think that while this is not a diagnostic exam there is a tremendous amount of information that you can get from doing arterial duplex from an assessment standpoint, a planning for intervention standpoint, particularly in patients in whom contrast avoidance is important. And then following up after your interventions and procedures. Um you have to be very systematic and you have to understand your wave forms and you may have to go back uh you know, pre where you're evaluating to understand where your abnormalities are occurring based on your wave forms. Optimizing the exam will help you, um and knowing the underlying processes will help you um uh perform the best exams and will also contribute to your opportunity and ability to provide the best interpretations. Thank you.