Hi, my name is Terry Case, Professor of Ultrasound at Nova Southeastern University. At the end of this program, the viewer should be able to discuss the extracranial, cerebral vascular anatomy, physiology, and pathophysiology, explain the common signs and symptoms and etiology of cerebrovascular disease, identify normal spectral waveforms of the extracranial cerebrovascular vessels, and recognize the common pitfalls encountered during an extracranial cerebrovascular examination. Also to describe the standard protocol for carotid duplex imaging as defined in the Society for Vascular Ultrasound Professional Performance Guidelines. Stroke, or cerebral vascular accident, also known as CVA, is the third leading cause of mortality in the United States, resulting in over 150,000 deaths each year. Stroke is the clinical designation for a rapidly developing loss of brain function due to ischemia to all or part of the brain. Temporary symptoms of stroke are referred to as trans ischemic attacks, or TIAs. TIAs are forms of cerebral ischemia that last less than 24 hours in which the patient recovers completely. Common clinical manifestations of TIAs include hemiparalysis, is weakness on one side of the body or an inability to move a part of your body such as the face, arm. The primary vascular origins of CVA or TIA phenomena include thrombosis, embolism, stenosis of the internal carotid artery, or hemorrhage of an intracranial vessel. Thrombosis is the formation of a thrombus inside a blood vessel, obstructing the flow of blood through the arteries in the brain. Thromboembolism is a general term describing both thrombosis and arterial stenosis is the narrowing of a lumen of the artery, usually caused by atheroma, resulting in atherosclerosis. Thrombosis can cause both TIAs and CVAs either from developing into a flow-reducing lesion or by the formation of thrombus on the plaque that may embolize. Flow-reducing lesions usually occur when the atheroma occludes more than 50% diameter of the lumen of the internal carotid artery. Natural history studies demonstrate that patients with lesions below a 50% diameter reduction are less likely to have a stroke when compared to patients with a greater than 50% diameter reduction. Hemorrhagic stroke occurs when a blood vessel ruptures inside the brain. Most often hemorrhagic stroke is associated with high blood pressure which stresses the artery walls until they break. Another cause of hemorrhagic stroke is an aneurysm. This is a weak spot in the wall of the artery which balloons out because of the pressure of blood circulating inside the affected artery. Eventually it can rupture and result in a stroke. The larger the aneurysm is, the more likely it is for a rupture to occur. It is unclear why people develop aneurysms but genes may play a role since aneurysms run in families. Brain tissue is very sensitive to bleeding and damage can occur very rapidly either because of the presence of blood itself or because the fluid increases pressure on the brain and harms it by pressing it against the skull. The anatomy of the cerebrovascular circulation consists of both intracranial and extracranial vessels. For the purpose of this course, we will focus on the extracranial vessels. The extracranial cerebrovascular arteries can be further divided into the carotid artery circulation which supplies blood to the anterior part of the brain identical on both sides except for the origins of the common carotid arteries. On the right, the innominate artery bifurcates into the right subclavian and the common carotid artery. On the left, the common carotid arteries originate from the aortic arch. The CCA courses anteriorly to the superior level of the thyroid gland. Here the CCA bifurcates into the right internal carotid artery also known as the ICA and the external carotid artery or the ECA. The origin of the ICA is slightly dilated leading to the term the carotid bulb or carotid sinus. You can see this right here on the anatomic drawing. The bulb may actually extend down to the most distal segment of the CCA. This is an important site as it is here where carotid artery disease is most likely to develop. The ICA continues anterior laterally until it enters the skull through the carotid canal. The primary role of the ICA is to perfuse the ophthalmic artery, anterior portion of the brain, and the circle of Willis. Generally there are no branches of the ICA outside of the skull. The ECA courses superiorly and anteriorly and contains several branches which feed primarily the thyroid, tongue, tonsils, and ears. You can see as I'm pointing this out right through here. Extending up to the ECA. Because the ECA does not directly perfuse the brain, it is not considered a source of TIA or CVA even when disease is present. However, it can become an important source of collateral blood flow in the presence of severe ipsilateral internal carotid artery disease. Here on this slide you can see the occluded ICA and the branches of the ECA that pick up through the ophthalmic artery and back to the siphon and circle of Willis. The vertebral arteries originate directly from the subclavian artery. They course up the posterior portion of the neck and run superiorly through the foramina and the transverse process of the cervical vertebra. There the two vertebral arteries join to form the basilar artery that we can see right here in this illustration. Blood circulates from one portion of a vessel to another because of difference in blood pressure, which is referred to as a pressure gradient. Blood is initially propelled through the circulation by the contraction of the ventricles. However, throughout the course of the arterial circulation, the initial pressure consistently declines as blood flow encounters fat total cross-sectional area as vessels branch and become smaller. This illustration here demonstrates the increased cross-sectional area as the blood vessels get smaller. The reduction of blood velocity and pressure is essential for the exchange of nutrients, oxygen, and waste to occur at the capillary level. Normal blood flow is termed parabolic, indicating that blood flow is faster in the center of the vessel and somewhat slower against the vessel walls. Here we can see an illustration here where friction is taking over, slowing down the blood flow against the walls, and that blood flow is faster in the middle, giving the term to parabolic blood flow. However, parabolic blood flow encountering a stenosis diverts the blood cells in many different vectors. This is referred to as turbulent blood flow. This illustration demonstrates the normal parabolic flow, and here we can see the chaotic flow of blood flow moving in several different directions. The ICA feeds primarily the anterior brain and the eyes. The ICA is a low-resistance system which allows flow to move with minimal pulsatility, providing a relative constant bathing of nutrients and oxygen to the tissues of the brain. Spectral Doppler of the normal ICA reveals relatively low peak systolic values and high diastolic flow. The ECA, on the other hand, demonstrates a relatively high-resistance system. The ECA has numerous terminal branches which feed primarily the face and the scalp. Waveform analysis reveals a Doppler signal with a relatively high systolic peak and low diastolic flow when compared to the internal carotid artery. Because the CCA perfuses both the ICA and the ECA, the spectral waveform will be a reflection of both of those vessels. The vertebral arteries perfuse the posterior part of the brain and therefore demonstrate a low-resistant flow pattern. Vertebral arteries demonstrate flow patterns similar to that of the internal carotid artery. Atherosclerosis is an inflammatory disease that affects the arterial system. It is largely due to the deposition of lipoproteins that result in the formation of plaques within the arteries. Endothelial injury is believed to be a result of the shear effect as blood flow tugs and injures the endothelial lining, particularly in the carotid bifurcation and proxies as the response to injury theory. Here we can see on this slide the injury to the intimal lining of the carotid vessel. Circulating monocytes infiltrate the intima of the vessel wall and these tissue macrophages act as scavenger cells taking up LDL cholesterol and forming characteristic foam cells as can be seen by this illustration here. The function of the cholesterol-laden foam cells is to consume and remove LDL from the vessel wall. However, if this process fails, foam cells die and build up deposits which develop as atheromatous plaque. The concern of the atheromas is the proximal internal artery is two-fold. First that plaque contributes to the attraction and formulation of platelets that progress to thrombosis or that plaque continues to metabolize into flow-reducing lesions that may result in TIA or stroke. 80 to 85% of TIAs and stroke are a result of blockage of the arterial circulation to the brain due to an embolus, an obstructing arterial thrombus, or a stenosis of the proximal internal carotid artery. Only 10 to 15% of strokes are caused by hemorrhage in the brain. The symptoms of TIA are temporary, generally lasting only 8 to 14 minutes, with most clearing within an hour. Permanent damage from a TIA does not occur because the oxygen supply to the brain tissue is restored fairly quickly. If the degree of internal carotid stenosis is severe and in the absence of adequate collateral circulation, the ipsilateral cerebral hemisphere may become underperfused. When this occurs, the arterial circulation decreases and there is an increased risk of thrombosis within the mid-cerebral artery, the anterior cerebral artery, and the branches of the intracranial arterial circulation. The ICA stenosis can proceed to a complete occlusion as is indicated by this slide here. In the ultrasound examination of the extracranial carotid arteries, stenosis is most commonly graded based on the peak systolic Doppler velocity in the region of maximum luminal narrowing. However, the peak systolic velocity is not always reliable in estimation of the degree of carotid stenosis. The diagnostic pitfalls one may encounter include technical difficulties with scanning, anatomic difficulties, variance, and interpretation errors. In order to obtain valid and reliable results, the examiner must perform a complete and thorough examination with meticulous attention to detail. In addition, the interpreter must understand hemodynamic and imaging principles related to the cerebrovascular system and the effects of confounding factors. Specific examples of pitfalls include tandem lesions, differentiation of high-grade stenosis from true occlusion, apparent normalization of distal velocities and waveforms in cases of very severe stenosis proximally, lesions of the carotid origin or the aortic valve, underestimation of severe stenosis due to heavily calcified plaque, and contralateral carotid artery stenosis. Recognition of these common sources of error can improve the accuracy of duplex ultrasound in diagnosis of carotid artery disease. Inconsistency in peak velocity measurements are a common problem when more than a single instrument or probe is used for testing. In the Hallmark article by Daigle published in the Journal of Vascular Technology, inherent spectral broadening was found to occur in all linear array transducers due to wide Doppler apertures that can result in significant overestimation of Doppler-derived velocities. Another author, Kimmy Smith, showed that the average variation in peak velocity measurements taken from multiple manufacturers' instruments was 23%. This has particular relevance in facilities where multiple instruments are used, but only one set of criteria has been validated. Specific criteria should be validated against all types of instruments used within your facility. Although most laboratories recognize the errors that are associated with Doppler angles larger than 60 degrees, fewer laboratories appreciate the variation in Doppler velocities that occur with changing angles between 45 and 60 degrees. Unpublished data have demonstrated large variations in velocity measurements when interrogating stenotic lesions using multiple angles. Equipment, transducer, and Doppler angle that is used also has implications in terms of comparison from one study occasion to the next. Using the same parameters on follow-up studies allows for a valid comparison and assessment of the progression of disease in patients with known carotid stenosis. In addition to the use of the 60-degree angle, it is also important for the examiner to be sure to take care to align the cursor angle so that it is parallel to the vessel wall as incorrect alignment will also result in errors in velocity acquisition. In diagram A, the angled cursor is corrected to 60 degrees and is also properly aligned so that it is parallel to the vessel wall. This assumes that the beam angle intersects the blood flow at a 60-degree angle. In diagram B, however, although the angle is corrected to 60 degrees, the cursor has not been aligned parallel to the vessel wall. In this example, the beam angle is in fact intersecting the flow of blood at a 42-degree angle. This will result in velocity acquisition errors. Using the color or grayscale image for placement of the Doppler cursor for spectral analysis and velocity acquisition without careful interrogation in the region of the flow abnormality will often fail to detect the maximum velocity within that lesion. It is important in the presence of suspected stenosis to profile the lesion. This is accomplished by walking the sample volume through the lesion by starting in the pre-stenotic zone and then identifying the focal increase in velocity that occurs in a hemodynamically significant stenosis. Keep in mind that the highest velocity may not necessarily be in the area that it appears to be in based on the color flow or the grayscale image. Therefore, the sample volume should be moved in and around the lesion to identify the highest velocity within that lesion. The sample volume should then be walked past the lesion to document post-stenotic turbulence. The presence of turbulence supports turbulence may not be elicited. Differentiating the internal from the external carotid artery is the most common pitfall in the evaluation of patients with carotid artery disease. Although it appears to be relatively straightforward, it can be difficult in patients with complicated anatomy and disease. Several parameters should be evaluated. The most useful of these is the waveform shape. Under normal conditions, the internal carotid artery yields a low-resistance waveform shape that consists of continuous forward flow throughout the cardiac cycle and will always yield more diastolic flow than the external carotid artery. In the presence of disease, this can change, however, and other factors must be considered. The presence of branches is useful. The external carotid artery will give off extracranial branches. Be careful not to mistake the lack of branches for the internal carotid artery. Inability to visualize branches does not confirm that you are evaluating the ICA. This may only mean that branches are not seen, although they are present. The internal carotid artery is usually larger in diameter, associated with the carotid bulb, and anatomically is located posterior and lateral to the external carotid artery. However, all these findings can be variable. Tapping on the superficial temporal artery may result in oscillation of the external carotid artery waveform. However, if oscillation is noted in the external carotid artery, make sure to tap the temporal artery while incinating the internal carotid artery as well. If oscillation is seen there, this sign is rendered useless. Temporal tapping is probably the least useful of all the parameters described to differentiate the internal from the external carotid artery. In a difficult diagnostic situation, using a combination of these diagnostic parameters will almost always differentiate between the two vessels. The presence of pulsatile flow within a vessel does not guarantee that you are looking in an artery when the internal carotid artery is occluded. A vein with pulsatile flow may be mistaken for the internal carotid artery. Although most errors can be eliminated by careful attention to the direction of flow, occasionally a venous tributary will cause cephalad before turning caudate, resulting in a pulsatile signal that is flowing toward the head. In these cases, careful attention to the course and termination of these vessels will often elucidate the findings. The presence of pulsatile flow within a vessel does not guarantee that you are looking in an artery when the internal carotid artery is occluded. A vein with pulsatile flow may be mistaken for the internal carotid artery. Although most errors can be eliminated by careful attention to the direction of flow, occasionally a venous tributary will cause cephalad before turning caudate, resulting in a pulsatile signal that is flowing toward the head. In these cases, careful attention to the course and termination of these vessels will often elucidate the findings. Care must be taken in acquiring Doppler velocity measurements in the region of a vessel bend since correct alignment of the cursor with the walls is difficult. Steep flow angles will produce high Doppler frequency shifts. Overestimation of the Doppler angle will produce false positive velocity measurements. A stenosis is assured, however, if an angle of zero is assumed and the Doppler-detected velocities remain elevated. A stenosis, atherosclerotic or not, must be suspected when post-stenotic turbulence is identified, even if using an angle of zero degrees produces velocities within a normal range. Failure to interrogate the common carotid artery at its origin may prevent detection of some proximal stenoses since normal velocities in a laminar flow profile can resume within a few vessel diameters downstream. These lesions may produce only very subtle changes in the waveform that are acquired. This pitfall can be avoided by comparison of the common carotid artery waveform at the same level on the contralateral side. Careful about the cardiac cycle. Although the absence of a flow signal is often the result of occlusion, this may not always be true. A near occlusion may be mistaken for an occlusion due to a combination of small lumen size, extensive plaque, a minute flow jet, or slow flow, which on their own or in combination may result in the inability to detect color or Doppler evidence of active blood flow. In addition, the echogenicity within the suspected occlusion may vary. When occlusion is suspected, other supporting findings commonly associated with occlusion should be searched for and documented. Comparison of the common carotid artery waveforms should show less diastolic flow on the occluded side. The external carotid artery on the affected side will often yield much higher velocities than its counterpart on the contralateral side. And you may be able to elicit an ICA thumping waveform at the origin of the suspected occlusion. Always be sure to demonstrate a patent external carotid artery with the appropriate waveform and image and Doppler as much of the internal carotid artery as possible. If the internal carotid artery is occluded, no flow will be elicited. The presence of antigrade flow in a distal internal carotid artery that is suspected to be occluded proximally probably means that a patent lumen has been overlooked. Calcification and the shadowing it causes because of reflection of the transmitted echoes presents a major obstacle to thorough B-mode and Doppler interrogation. In these cases, it is critically important to thoroughly evaluate the areas immediately proximal and distal to the area of calcification with careful attention directed to the changes in waveform shape and velocity that may be suggestive of stenosis at the site of calcification. The vertebral artery must be identified as it courses between the spiny processes rather than only at its origin since multiple arteries carrying cephalad flow arise from the subclavian artery. In this image, here we see the subclavian artery and multiple subclavian artery and vein branches near its origin. The vertebral artery is best evaluated in the midneck where it is easily identified by its classic sonographic appearance as it courses between the bony processes of the spine. Once identified at this level, it can then be followed back to its origin to evaluate for atherosclerotic stenosis if necessary as this is the site where stenosis is most likely to occur. ♪♪ Published criteria provide a handy framework for evaluating and estimating the degree of carotid stenosis. However, due to variables in patient population, personnel, protocols, instrumentation, and angiogram interpretation methodology, each vascular laboratory must validate its own laboratory-specific criteria. In addition, these velocity criteria have been developed for the estimation of stenosis at the origin of the internal carotid artery only. Although they may be applied to lesions and aortic insufficiency and or stenosis, have been identified as causes of decreased velocities within the carotid artery. Must be suspected when there is unilateral absence of diastolic flow in the internal carotid artery. When the internal carotid artery is occluded intracranially, the end-diastolic velocity in the extracranial ICA will be depressed. Reliance on absolute velocity measurements in these instances may under-classify or entirely miss the internal carotid artery stenosis. For this reason, it is important not only to look at the velocity data, but also to examine the images for waveform changes that are consistent with these pathologies. A severe stenosis will reduce systolic and diastolic velocities distal to the lesion. Sole reliance on absolute velocities to classify a suspected stenosis in patients with cardiac arrhythmias using the Doppler waveform with the highest peak systolic velocity for measurement will overestimate velocity. Whereas, use of the lowest peak velocity waveform will underestimate absolute velocity. In order to avoid these pitfalls, an intermediate waveform should be used consistently for velocity measurements and estimation of stenosis. At this time, there is no consensus on the diagnostic criteria for the estimation of restenosis in patients with carotid stents. Please refer to the Society for Vascular Ultrasounds website on this and other related topics. Extracranial Cerebral Vascular Evaluations are performed to assess the common internal and external carotid arteries, along with the vertebral arteries, in order to determine the hemodynamic status of these vessels and to detect the presence of pathology. Contraindications for the carotid duplex examination are few. However, some limitations exist and may include patients with short and thick muscular necks, patients with chronic obstructive pulmonary disease, and patients with arthritic necks who may not be able to lie flat during the examination, patients who have had recent surgery, which may result in limited penetration and visualization secondary to the presence of a hematoma, surgical staples and or dressings, patients with dense calcific plaques, patients who may not be able to cooperate during the exam due to mental status changes and involuntary movements, and studies performed at the bedside, which may be limited due to space constraints caused by the presence of large medical equipment and the room's dimensions. We are now going to walk through the performance of a typical carotid examination. The first thing the sonographer should do is introduce him or herself to the patient and explain why the examination is being performed, always taking into consideration the age and mental status of the patient while ensuring the necessity for each portion of the evaluation is clearly understood. The sonographers will need to respond to questions and concerns about any aspect of the evaluation, educating patients about risk factors for and symptoms of stroke and TIA, referring specific diagnostic treatments or prognosis questions to the patient's physician. For this exam, the patient will be lying in the supine position with their head and neck placed in a manner that allows the sonographer maximum access to the vessels being examined. In some instances, due to the immobility of the patient, the sonographer may elect to examine the patient sitting in a chair. The patient assessment must be completed before the examination is performed. It should include any contraindications to the procedure along with an assessment of the patient's ability to tolerate the exam. The sonographer will attain a complete pertinent history by interviewing the patient or the patient's representative and or by reviewing the patient's medical records. A pertinent history includes the patient's current medical status, any previous vascular, cardiovascular surgeries, any current medications or therapy the patient is on, the presence of any risk factors for cerebral vascular disease such as the patient's age and smoking history, the presence of diabetes, hypertension, peripheral vascular disease or coronary artery disease, any relevant family history of cerebral vascular, coronary artery or peripheral vascular disease, as well as any family history of diabetes and hypertension. The presence of any symptoms for cerebral vascular disease should be evaluated, such as aphasia, dysphasia, visual disturbances, cervical carotid bruise, numbness, weakness, and or paralysis of the extremities. Results of other relevant diagnostic procedures should also be included. After the previous information is collected, bilateral brachial artery blood pressures would now be performed. When indicated, the technologist should perform adjunctive procedures such as auscultation of bruise in the region of the carotid bulb and subclavian arteries. You should also verify that the requested procedure correlates with the patient's clinical presentation. Throughout the examination, sonographic characteristics of normal and abnormal tissue structures and blood flow are observed so that scanning techniques can be adjusted as necessary to optimize image quality and spectral waveform characteristics. The patient's physical and mental status is assessed and monitored throughout the exam, and modifications are made to the procedure plan according to changes in the patient's clinical status during the exam. Sonographic findings are analyzed throughout the course of the examination to ensure that sufficient data is provided to the physician in order to direct patient management and render a final diagnosis. This study should always be performed with the appropriate duplex instrumentation that allows display of both two-dimensional structure and motion in real-time and Doppler ultrasonic signal documentation with spectral analysis and color Doppler imaging. The sonographer performing the extracranial cerebral vascular duplex examination should use an image carrying frequency of at least 5 megahertz, a Doppler carrying frequency of at least 3 megahertz, and the appropriate videotape, film, static images, or digital storage devices. The sonographers should follow a standard examination protocol for each study. Bilateral examinations are essential for a complete evaluation. However, postoperative studies can be unilateral based on internal laboratory algorithms. The standard exam includes B-mode imaging of all accessible portions of the entire common carotid artery, carotid bifurcation, internal carotid artery, and external carotid artery. Because of anatomical variance, it may not be possible to use standard sagittal and transverse scan planes. Therefore, we will refer to the short and long axis of the vessel. The exam starts with a short axis view of the right common carotid artery at or near its origin. The scan continues to precede cephalad, visualizing the entire length of the common carotid artery to the level of the carotid bifurcation. At this point, the internal and external carotid arteries are identified in cross section. This short axis sweep provides a preview of the anatomy of the carotid arteries by allowing the sonographers to identify the level of the carotid bifurcation, the relationship between the internal and external carotid artery, and the severity and location of any disease present. In the long axis, all accessible portions of the common and internal carotid arterial system are evaluated. The origin of the external carotid artery and the mid portion of the vertebral artery is also evaluated. This is accomplished using a combination of grayscale, color, and pulse wave spectral Doppler. Disease processes and internal laboratory protocols will determine where hard copy images are obtained. However, we recommend the minimal number of images include two within the common carotid artery, two within the internal carotid artery, one within the external carotid artery, and one within the vertebral artery. It is recommended that the subclavian artery be evaluated in the presence of brachial artery pressure asymmetry, 20 millimeters of mercury and or flow reversal in the vertebral artery. All views are obtained in multiple anterior, lateral, and posterior lateral long axis and short axis imaging planes as needed to penetrate the area of interest. Grayscale data interpretation should attempt to classify echo characteristics of plaque as homogeneous uniform echo patterns or heterogeneous complex patterns with mixed echo densities and or sonolucent areas. And to describe surface characteristics, example smooth or irregular. If pathology is present, plaque appearance, location, extent of the disease should be documented whenever possible. Doppler spectral analysis is then performed in the long axis plane. In an effort to promote consistency, velocity measurements should be taken at an angle of 60 degrees whenever possible and should never exceed 60 degrees. The Doppler cursor should be aligned parallel to the vessel walls. In order to ensure complete interrogation, precisely track the spectral Doppler cursor throughout the entire common and internal carotid arteries. At least one representative spectral waveform is recorded proximally and distally in the common and internal carotid artery. Doppler information is used to identify the presence, absence, and direction of flow and the severity of stenosis. In the presence of pathology, spectral waveforms should be recorded proximally within and distal to the lesion. Measurements include peak systolic velocities, PSV, and end diastolic velocities, EDV, in the ICA and stenotic regions of the CCA. An unobstructed segment two to three centimeters proximal to the carotid bifurcation within the common carotid artery is recommended reference point for the calculation of the ICA to CCA velocity ratios. A representative spectral waveform with velocity measurements and determination of flow direction are recorded in the proximal external carotid artery and the vertebral artery. Color Doppler imaging should be performed as per the ICAVL standards. To determine any change in follow-up studies, review previous examinations so that the current evaluation duplicates prior imaging and Doppler parameters. The examination protocol may need to be modified to address current needs of the patient. After completing the scanning portion of the exam, the sonographer will review the data acquired to ensure that a complete and comprehensive evaluation has been performed and documented. Explain and document any exceptions to the routine examinations, i.e., study limitations, omissions, or revisions. Record all technical findings required to complete the final diagnosis on a worksheet, logbook, or other appropriate forms so that the measurements can be classified according to the laboratory's diagnostic criteria based on published or internally validated data. Documentation of this exam should be consistent with the current ICAVL standards. It is recommended that published or internal generated diagnostic criteria should be validated for each ultrasound system used. When validating ultrasound diagnostic criteria, it is important to realize that equipment, operator, and interpretation variability is inherent to this process. To view this or any of the SVU guidelines, please visit our website at www.svunet.org. When doing a carotid duplex examination, the first thing we want to do is choose the appropriate transducer. We're going to want to use a linear high frequency transducer, such as this 9L. We will then select that on the machine. Once that's selected, we will then select the appropriate preset, which in this instance is a carotid. We will then go to the patient and place, typically, a tau down around the region that we will be scanning. I also want to position the patient's neck in an appropriate way to give me a nice window to use as I place my transducer here and look for the carotid artery. Once that's like that, I will then place gel along the course of the carotid artery. I then will take my transducer and place it so a short axis view of the area that I'm looking at will be on the screen. And you can see how I'm doing that just like this. Kind of move the gel around in the locations that I'll be moving this transducer up, cephalad, and caudad. And once I do that, I'm going to look for a short axis view of the carotid artery and the internal jugular vein. And I can see that really nicely in the middle of my screen here. With that carotid artery in a short axis, I'm going to move caudad towards its origin. And you can see that I am now on the left side of our model's neck. And I will note that the common carotid artery will be coming off of the aortic arch, unlike on the right side where the common carotid artery comes off the anomina or brachiocephalic artery. The left side's common carotid artery will come off much deeper off that aortic arch. And sometimes it will be a little bit more difficult to see that origin, if not impossible in a lot of the cases when you're scanning. So we can see that I'm following that carotid artery as far down as I can near its origin off of the aortic arch. Once I find that, I am then going to move cephalad towards the region of the bifurcation. And I can see that bifurcation very nicely. You can see the internal and external carotid arteries splitting right there. And move as cephalad as I can, seeing as much of that internal carotid artery as possible. Once I do that, I like to move back down to the bifurcation. I will then turn my transducer so I get a nice long axis of the internal carotid artery at the level of the bifurcation. If I move medially, I will then go into the external carotid artery. You can see that right there. Moving back laterally puts me back into the internal carotid artery. During this B-mode evaluation, I'm really looking for any types of plaque or stenosis that I may see. After I feel comfortable that I've taken the images that are necessary based on my lab's protocol, I will then move back down caudad to the origin or the level of the origin of the common carotid artery and start to assess the Doppler spectra waveforms. To do that, I'm going to turn color on, and I'm going to have to place the artery in such a way that I will be able to obtain a 60-degree angle in relationship to the walls of the vessel. To do that, I'm going to really need to manipulate this transducer. You can see this transducer. I'm going to place this on our model's neck. If I heel-toe it, it's going to allow the vessel to move in such a way that will allow me to obtain appropriate 60-degree angles based on the location of the vessel walls. And you'll see me moving that throughout this examination. I have several approaches that I can use, an anterior approach, a medial approach, and a posterior approach. I prefer the posterior approach because it gives me a little bit more room to heel-toe. A lot of people start scanning anteriorly, but I find that if I move up, I kind of run into the mandible. So I really like to use this posterior or medial approach when I'm examining the carotid arteries. So here, I'm going to first get back a nice, long-axis view of this left common carotid artery. I'm going to then place color in it. And you can see that my color Doppler box is steered to the right of the screen. I'm going to actually steer that straight up and down so that the vessel is really diving down towards the origin. And this will give me a much better angle to use when I'm obtaining my spectral Doppler waveform. Once I see that, I can invert the color here. And I'm going to now turn on my pulse wave. Now, I'm just going to keep the pulse wave here because our model is kind of breathing up and down. You can see how that vessel is moving around my sample volume. Sometimes you'll note that that sample volume will move outside of the vessel. In those cases, you really want to have the patient hold their breath. You don't want them to take a deep breath in because that's going to actually move the vessel itself. Just have them hold their breath. Try to kind of feel when he's breathing in or breathing out. Have him, after he's breathed in, have him hold his breath there. And then take that Doppler signal. So that's exactly what I'm going to do here. Joe, if I could just hold your breath. I'm going to adjust my scale so that's a nice, appropriate waveform. And take that. Very nice. I am now going to label this proximal CCA on the left side here and print that. Print that. And then move cephalad into the region of the mid-common carotid artery. You notice I can have triplex on or triplex off. I just showed you with triplex on. I'm now turning triplex off. And I'm just going to then take my Doppler waveform by itself when I feel that I have the appropriate angle and in the appropriate position to take a spectral waveform. So let's do that right now. In this location, you can see I'm probably going to want to steer my box to get a better angle in this mid-portion of the common carotid artery. And here we go. We're going to steer that one more time appropriately. There you go. That's very nice. Going to invert. There we go. And you can see now the artery in this position is not moving that much. So I'm feeling pretty comfortable. I don't have to have the patient hold his or her breath. Going to make sure that my Doppler angle is appropriate. And then I'm going to engage the spectral Doppler waveform. Hit freeze. And you can see that I really want to have my Doppler waveform take up about 3 quarters of that Doppler spectral screen. And I can adjust that up and down by moving my baseline or moving my PRF in any fashion. You can see my calipers are located at a peak systolic level and an end diastolic level. And those velocities are recorded up here on the top part of the screen at 147 and 36 approximately. I will then label that appropriately, the mid-left CCA, take that picture, and once again move cephalad into the distal portion of the common carotid artery. And here we are. Once again, I want to maintain my Doppler cursor right in the middle of this vessel. Going to increase my color a little bit to have nice filling within that vessel. You can see that my angle is at 60 degrees parallel to the vessel walls. I'm going to take that Doppler signal, adjust my spectral waveform. And after a few beats, I'm going to freeze that. My calipers come up. I have my peak and end diastolic values. And I'm going to label that and print it. Now moving into the area of the bifurcation. We've seen this on the grayscale view. Now I can see it with color and with my Doppler sight line. We can see this area right here going into internal carotid artery where the area actually increases in size or dilates a little bit. And you can see a little bit of a swirling in there because of that increase in size. I'm going to come to this area right here called the carotid bifurcation. And we're going to take that signal. And you can see that it's a little bit more disturbed because of that swirling pattern that we see in that dilated area. We don't see any plaque on grayscale. We don't see any problems with color. We're going to consider that to be a normal portion of the vessel. We're going to select the appropriate numbers here based on the peak and end diastolic value. We're going to label that the left carotid bifurcation and take that picture. And now we're going to move into the proximal portion of the internal carotid artery. Now this area that I'm looking at right now is the area that we're going to find most of our disease when we're doing the carotid duplex examination. You want to be very meticulous about moving your Doppler waveform back and forth. If you see any areas where you think there's stenosis, walk that through the stenosis and pay particular attention to getting the highest velocity possible in that area with appropriate angle correction. Those numbers in this area will be used to base the percent stenosis for this duplex examination. So we are going to now go back, and you can see that the vessel now is going to turn and move cephalad moving down on the screen here. So I'm going to actually steer my angle, my color box, to the left of the screen. You can see that that makes a very nice angle for me to incinate the walls. And the Doppler cursor are at 60 degrees. I'm going to now take this waveform. And you can see how that waveform is recovered from that dilated area where we saw a little bit of disturbed flow. Now we're coming back to nice laminar flow here. We have a peak and end diastolic values that are appropriate. We now will label this the proximal left internal carotid artery. Take that picture, and we'll move a little bit more cephalad now to take the mid portion. You can see now I'm really running in trouble with this mandible. I really have to go a little bit more posterior to get around that area, and the vessel is going to start diving down on me. So once again, I'm probably going to have to steer. When you see that vessel dive, you're really going to have to steer this box up and down, because that'll give you the best angle of incination. We can see that here. This is a really nice angle, 60 degrees here. I'm going to take this. I want to be right in the middle of the vessel. You can see nice laminar flow here. Take a couple of nice beats, spectral waveforms, and I'm going to hit freeze. Once again, taking the peak and end diastolic values, I'm going to label that the mid internal carotid artery. Take that picture, and we're going to go to the last portion of the internal carotid artery, the distal internal carotid artery, which is somewhat difficult to get because of the various anatomical problems that are associated with this vessel being so high up in the neck. And commonly, you will see a lot of tortuosity in this region, the mid and the distal region. So it makes it a little bit difficult to maintain that 60 degree angle. Here we have a nice angle. We're going to take this picture for the distal. Really nice laminar flow here, nice spectral waveform. You can see our peak and end diastolic values. I will label this left distal internal carotid artery, and then take that. So the internal carotid artery is now complete. Our Doppler assessment, we looked at the B mode imaging, making sure there was no plaque there. And if it was, we identified the plaque morphology. We have color on, and we took spectral Doppler waveforms. And we will take that now. And based on our internal protocols, we will place a percent stenosis in that bifurcation proximal internal carotid artery area where the disease was located if we, in fact, found it there. We are now going to move to the external carotid artery. I'm sorry. At that level, the bifurcation again. Let's just go back to a grayscale image. And if I ever fall off, I always want to go back to the grayscale image and go into a cross-sectional view, find out where my bifurcation is again, and then reposition myself by placing the vessel back in a long axis. And you can see I just did that right there. And then immediately, I'll find that ECA. That does not happen all the time. There's some other things that we need to look for when we're determining between the ICA and the ECA. One is anatomical location, lateral versus medial. Other is branches. If we turn the color on, we may be able to see a branch in his external carotid artery. And you can see that one branch coming off right here. There's one coming off right there. So that really helps me to identify and become more confident that's the external carotid artery. I'm sorry. And also, what I really like to use besides those is the Doppler waveform morphology, which typically will be much more resistant in the external carotid artery, but not all the time. You will see some external carotid arteries with some increased diastolic flow. So let's put our color Doppler in and see what this waveform looks like. Our spectral Doppler, I'm sorry. We'll get a nice angle again. I think I'm going to steer my box here. It would be more appropriate to assess this vessel. There we go. I'm going to increase my color just to fill it a little bit more. And then we'll take this Doppler waveform. I'm going to reposition, get a little better waveform. I like to have a little better waveform there. See that branch coming off right there. There we go. And now you can really see the difference in resistance when compared to the internal carotid artery waveforms that we had just previously taken. Much less diastolic flow here, typical of an external carotid artery. We'll label that. Take that picture. And then we're going to move to the final location that we're going to show you today. The vertebral arteries. The vertebral arteries is going to be in a different position for us. It's not going to be in the same scan plane, typically, that we are looking at the common external and internal carotid arteries. I'm actually going to reposition the patient's head by taking the chin and just lifting it up straight. You can see now that his head is straight up and down. It's not tilted to the side anymore. I'm going to open this little window up here where I'm going to take my transducer, instead of coming from a lateral approach, and we're going to come from a straight up and down medial approach here and look with B mode for the vertebral artery and the vertebral bodies. And I had a nice image right there of what I'm looking for. And you can see the shadow caused by the vertebral bodies and the dark area in between each vertebral body, which represents the vertebral artery and or vein. Let's put our color on to confirm that. And you can see that very nicely, the vertebral artery. We're assuming that. We're going to put a Doppler signal in there to confirm that. And that most definitely is an arterial waveform. And you can see the high diastolic flow that we would expect in the vertebral arteries, also. What we really want to note in the vertebral arteries is the direction of flow. We want to make sure that flow in the vertebrals is moving towards the brain, which we call antegrade flow, as opposed to retrograde flow, which would be flowing away. That retrograde flow is usually caused by proximal stenosis, typically in the subclavian artery, proximal to the origin of the vertebral artery. If that, in fact, is the case, and we probably already noted that it may be by taking bilateral brachial pressures prior to doing the examination, if they were off by 20 millimeters or more, more likely that you're going to find some type of retrograde flow in the vertebral arteries. However, that is not always the case. You will find examinations where those pressures were normal, or you thought they were normal, and then went to the vertebral arteries and found that the vertebral artery was, in fact, retrograde. If you do find that, what I suggest you do is kind of search out that stenosis within the subclavian or innominate artery, depending on what side of the body that you are on. So let's take this waveform and label it. We have this nice vertebral waveform. I think that's nice and appropriate. We're going to call that the mid-vertebral artery. That's probably the location that you're typically going to be in. If this waveform was monophasic, there may be a stenosis at the origin of the vertebral arteries. If that's the case, you would then want to move down towards the origin of the vertebral arteries off the subclavian, obviously on this left side here and the right side, and see if you can pull out that vertebral artery stenosis in that case. With that, we're going to end the examination, and thank you very much. Thank you.

Terry Case

Ultrasound

extracranial cerebrovascular system

cerebrovascular disease

carotid duplex imaging

stroke

thrombosis

embolism

atherosclerosis

Doppler waveforms analysis