 Welcome to Sonobas. I am Dr. Mohit Shah and I am going to take you to the technique of Karotid Doppler today. So for the basic positioning of a furrow patient you have to remember that the patient should lie with his shoulder on a pillow so the head is hanging down. In this way you actually stretch the neck. You want the neck in hyperextension because sometimes the Karotid atleast can have a high bifurcation. So you need an extended neck to proceed with the first step of Doppler and that is a good b-mode evaluation. For a good b-mode evaluation you keep your probe transverse in the suprasternal region so that you identify the brachycephalic atleast. The brachycephalic atleast is going to bifurcate into the common Karotid and the subclavian. So the subclavian origin is a point that I will need to stress upon because at times you can have plaques which can potentially cause occlusion or stenosis of the subclavian and can cause an ipsilateral stain. So your b-mode evaluation should begin with the brachycephalic making sure that you have seen the subclavian origin well and then you proceed to look at the common Karotid artery in transverse. Now that's the common Karotid in transverse nice and pulsating. If you notice my probe pressure is too much so that the jugular vein is compressed. If I loosen the pressure you can see the jugular vein lateral to the common Karotid as I go up and up and up till it bifurcates. Now normally the bifurcation is side by side the two branches the two branches of the common Karotid lie side to side. Normally you have the ICA which is more lateral and ECA which is more medial. In this case however it is anteroposterior. So if you notice the ECA is more anterior the ICA is more posterior. Now there are ways to know which artery is the ICA and which is the ECA and it is important for us to know as well because at times when the one of the arteries is blocked it becomes a dilemma as to which artery are we exactly seeing at this point in time. So you have differences between the ICA and the ECA. Normally the ICA is larger increased against and the ECA is relatively smaller in caliber. The ICA is more lateral, ECA is more medial but in this case the ICA is more posterior. Also if you trace the ECA you will realize that the ECA has branches in the neck whereas the ICA does not branch in the neck and when you switch on color the ECA is actually pulsating whereas the ICA reveals more or less steer the beam straight, steer it straight. The ICA is fairly more continuous flow. Now you have got to realize that in this section I had to keep the beam straight to visualize the ICA. That is because the axis of the ICA here is coming perpendicular to the beam at this point in time. So if I am seeing an artery which is making an angle to the probe and if I give an angle correction I am actually compounding the angle. So when you compound an angle you lose information. I just want to show it to you again. If I steer the beam I may lose the information but if I am keeping it straight I am fairly seeing the artery in a much better way except at a point where you will have the beam which is perpendicular and wherever the beam is perpendicular by the Doppler equation you will have no flow. But fairly you will see that the ICA is larger and has a more continuous flow than the ECA which is pulsatile. And lastly the difference would be on Doppler but I will come back to it later on. So on the beam mode once I have seen the carotid artery and its bifurcation I am supposed to watch for the plaque lesions all the atherosclerotic changes in the carotid arteries which starts from the common carotid artery and you see in this patient too a very nice smooth intimal layer and we are supposed to look at this intimal layer more so in the carotid artery in the internal carotid arteries because that's the common site of occlusion which can give rise to slope. So we are looking at the intimal layer there and we are supposed to look for plaques and grade plaques. For anyone doing carotid Doppler it's a must that you follow the carotid Doppler consensus statement where you are supposed to grade plaques on beam mode into type 1, type 2, type 3 and type 4. Type 1 and 2 being hypoequate type 3 and 4 being more calcified. Type 1 is more potential for causing plaque ulcerations and hem and therefore emboli and therefore they are unstable plaques whereas type 3 and type 4 are more stable plaques that eventually that potentially cause less of thrombotic occlusions. So once you have graded those plaques you are supposed to look for diameter reductions. Now in this patient because the carotid lies more posteriorly I will have to go from a lateral aspect to get the internal carotid artery in a transverse position. Once I have gotten that I am going to freeze the image and ask my machine to help me calculate the diameter reduction. So for the diameter reduction you place a set of calipers on the outer margins of the wall and another set of calipers on the inner margins of the wall. If you have a plaque on the inner margin of the plaque and the machine will tell you that give you the diameter reduction there which is approximately a 24%. Now when you take diameter reduction ensure that you are in the true transverse view. If you try to take it in a longitudinal view you can foreshorten the values and therefore make sure that you are in a good B more. If you try to take it in color there is a potential that the color may mask the plaque and you can actually underestimate a stenosis. So therefore diameter reduction is strictly taken in a transverse section in B mode, inner to inner and outer to outer and the machine does the calculations for you. So grading of stenosis by this method is sort of useful only if the diameter reduction is 50% or lesser. If you have a larger plaque then you should rely on the spectral trace and the actual velocities to grade the stenosis. But if it is less than 50% the diameter reduction is a much more accurate way of assessing the stenosis. Then I have switched on the color and begin my tracing again from the common carotids. Now the machine has preset normally when you choose a carotid preset the machine shows the common carotid to be in the red color. Ensure that your box is just covering the vessel and you see good wall to wall flow with normal use. The moment you decrease your gain settings you will start seeing aliasing which is absolutely not desirable. So now I am going to ask Shivangi to increase the gain so that yes that's good. I can see good wall to wall flow in a uniform color you. This is what I need the most a wall to wall flow because sometimes type 1 plaques which are entirely hypoechoic may be missed on B mode because they are so absolutely of the same equigenicity as that of the lumen. But a color will actually identify the plaque and color helps you to identify the length of the plaque. So when you're looking at the actual length color helps you create that negative contrast with the plaque therefore allowing it to be seen very well as an hypoechoic filling defect within the color filled lumen of the vessel. When you look at the color you look for points of aliasing. Flow channel narrowing and aliasing are against signs that we may probably deal with a stenosis. So looking for that is a important finding and then we switch on the spectrum here. So the spectrum imperative that we have a good angle correction. This is an un-diseased carotid artery so my angle is going to be parallel to the vessel wall because this is a laminar flow pattern. I know that the flow is going to be parallel to the vessel wall and therefore my angle is set in that way that it is parallel to the vessel wall. But in the point of stenosis you have to actually look at the aliasing jet and keep your sample parallel to the aliasing jet to calculate accurate velocities. This is extremely important in carotid because your grading of stenosis is based on velocity criteria and the grading of stenosis depends which patient goes for medical management and which in which patient a surgical indication is suggested. So therefore everything depends upon a good technique and it is a good angle correction spectrum. So this is a good normal waveform of a common carotid artery. Common carotid will have features of both the external as well as the internal carotid and therefore you have a good forward systolic flow and a deep pre-diastolic notch. And the progress to the bifurcation, steer the beam, try and get the external carotid. External carotid does not supply the brain entirely. There is only one branch, the middle meningeal which supplies the brain and therefore you expect a medium resistance waveform there where you have a good forward diastolic flow and a deep pre-diastolic notch again. So this is a sign of a medium resistance artery and ECA is a typical example of a medium size artery and if you want to confirm it is an ECA, all you need to do is do the spectrum and give pressure on the, just keep pressuring the triggers there and you will see the reflections of changes in peripheral resistance of the superficial temporal artery being reflected in the diastolic flow component of the ECA. This is a confirmatory test that it is indeed an ECA and this is important when your the ICA gets occluded and you see only one vessel and you have to determine which is the external or the internal carotid artery. So if having seen the medium resistance waveform of the ECA, I am now going to show you the normal waveform of the ICA. Can I just take the spectrum there? Yeah, invert, scale down. So if you look at the ICA, it has got a good forward diastolic flow. Now this is a signature of an internal carotid artery that it is supplying the brain which has inherently a low resistance circulation and therefore the diastolic flow is high and if you see there's a clear gap between the waveform and the baseline saying that the wave the velocities are never zero in the internal carotid artery and the flow is always forward even when the heart is dilating the diastolic flow is still forward towards the brain. This is a signature of an internal carotid artery and whenever you have stenosis you have to ensure that your angle correction is right so that you measure the velocities and then grade the stenosis according to the consensus report. It is graded into less than 50, 50 to 69 and 70 and above. So this is important that your angle correction is extremely relevant in this case. Vertebral has a similar waveform as that of the ICA and has to have the same flow direction as that of the common carotid artery. So invert please, invert. So here I am seeing the vertebral in between the transverse processes. If you look at the transverse processes I see the vertebral artery in red and the vertebral vein in blue and if I take my probe further to the common carotid artery I see the common carotid in red and the vertebral in red. That means it is confirming that both these vessels are going towards the brain. You can pick up a complete subtly even still by looking at the color changes here. Once you have done and confirmed that the vertebral is seen it is of normal caliber and it is the same flow as that of the common carotid, I proceed to put a spectrum there. Again you are ensuring that a good angle correction is done there and if you see it it reveals a good forward diastolic flow almost similar to what we have been seeing in the internal carotid artery. So make sure that the vertebrals are seen very well decreased and they need to be searched for in between the transverse processes. On B mode alone you can see that very well. If the vertebrals are not seen then probably it could be hypoplastic which is a normal variant or they could have a stenosis at the origin of the vertebral artery or a occlusion at the vertebral artery but it is easy to look at the vertebrals just between the transverse processes and similarly you're going to trace the left side as well. Thank you so much for your kind attention. We have learned to adjust all the technical parameters manually but with advancement in technology everything is now automated. So in this Resonance 7 by Mindray it has a one stop button called the smart track. If you press that the machine automatically adjusts the parameters for you. Now if I see if I just move the probe there the machine automatically adjusts the box it will automatically adjust the steer and it will automatically adjust the gains even if I steer it manually if I want to go back it will automatically adjust the steer for you. So you just have to track the artery and the machine will do the rest for you.