Considerable patient-to-patient variability occurs in ECA flow velocity in normal individuals because pulsatility varies considerably from one person to another since some individuals have a sharply spiked systolic peak, while others have a more blunted peak. Follow the vessel intially in B-mode and then using colour doppler. 7.2 ). Values up to 150 cm/sec can be seen without a significant lesion being present (Figure 7-8). no, leaving open to variability; the 150 cm/sec addressed later>, likely a reflection of a higher cardiac output. Data from 202 patients showing changes in peak systolic velocity (PSV) sensitivity, specificity, and accuracy for the diagnosis of 70% or greater angiographically proven stenosis using NASCET grading system. In others, magnetic resonance angiography (MRA) or computed tomographic angiography (CTA) may be performed in combination with sonography in cases where significant luminal narrowing is identified on the ultrasound examination or when the sonographic results are equivocal. 1B. You must have JavaScript enabled to use this form. It is routinely examined as part of carotid duplex ultrasound, but criteria for determining ECA stenosis are poorly characterized and typically extrapolated from internal carotid artery data. Look for stenoses highlighted by aliasing in the colour doppler. In a diseased artery, however, the color velocity scale should be shifted up or down according to the mean velocity of blood flow to demonstrate aliasing only in systole. Off-axis view of the carotid wall. However, both blood velocity and vessel diameter are critical components required to accurately determine blood flow, and there is mounting evidence that the MCA is vasoactive. Locate it in transverse and rotate into longitudinal. The ICA and ECA can be distinguished by the low-resistance waveforms (higher diastolic flow) in the ICA as compared with the high-resistance waveforms in the ECA (lower diastolic flow) ( Fig. The mean peak systolic velocity in the ECA is reported as being 77 cm/sec in normal individuals, and the maximum velocity does not normally exceed 115 cm/sec. c. demonstrate a high-resistance Doppler signal. The internal carotid PSV may be falsely elevated in tortuous vessels. Blood clot (deep vein thrombosis) Venous insufficiency. Ultrasound of the Shoulder Case Series: What is the Diagnosis? ADVERTISEMENT: Supporters see fewer/no ads. The distribution of blood flow velocity across the diameter of the artery follows a parabolic pattern (see Chapter 1) with slower velocities near the vessel wall and faster velocities near the center. no, leaving open to variability; the 150 cm/sec addressed later>, likely a reflection of a higher cardiac output. Several studies have identified a peak systolic velocity of 230 cm/s as a reasonable threshold for determining 70% stenosis, and this has been suggested as a suitable screening threshold as well [5,6]. The artery and vein can be differentiated by direction of flow on color Doppler as well as by the tendency of the vein to collapse with external ultrasound probe compression. In a normal carotid US examination, the color velocity scale should be set between 30 and 40 cm/sec (mean velocity). Ultrasound of Normal carotid bifurcation. PSV is by far the most commonly used parameter because it is easily obtained and highly reproducible. Internal carotid artery stenosis. Assess the bifurcation in transverse. As it enters the parotid gland, it gives rise to its terminal branches, the superficial temporal and maxillary arteries. {"url":"/signup-modal-props.json?lang=us"}, Di Muzio B, External carotid artery - normal Doppler waveform. On transverse sections, clear visualization of the lumen-intima interface indicates that the image plane is perpendicular to the vessel axis. Although this is an appropriate method in most vessels, there are several unique features of the proximal ICA that render this measurement technique problematic. 7.1 ). Along its course, it rapidly diminishes in size and as it does so, gives off various branches (see below). Reference article, Radiopaedia.org (Accessed on 02 Mar 2023) https://doi.org/10.53347/rID-4641, {"containerId":"expandableQuestionsContainer","displayRelatedArticles":true,"displayNextQuestion":true,"displaySkipQuestion":true,"articleId":4641,"questionManager":null,"mcqUrl":"https://radiopaedia.org/articles/external-carotid-artery-1/questions/1384?lang=us"}, Figure 3: external carotid artery (Gray's illustration), Figure 4: external carotid artery main branches, Figure 6: development from the aortic arches (Gray's illustration), Figure 7: carotid artery development (Gray's illustration), Case 2: digital subtraction angiography (DSA), superior longitudinal muscle of the tongue, inferior longitudinal muscle of the tongue, levator labii superioris alaeque nasalis muscle, superficial layer of the deep cervical fascia, ostiomeatal narrowing due to variant anatomy, Some Anatomists Like Freaking Out Poor Medical Students, Some American Ladies Found Our Pyramids Most Satisfactory, anteriorly (i.e. Tortuous segments, kinks, or areas of branching disrupt the normal laminar flow pattern. This chapter emphasizes the Doppler evaluation of ICA stenosis because it has been extensively studied and is strongly associated with TIA and stroke. Fig. FIGURE 7-6 Normal carotid artery Doppler waveforms. The angle between ultrasound beam and the walls of the common carotid artery are not perpendicular. The carotid bulb itself tends to have turbulent flow rather than laminar, causing pockets of retrograde flow on color Doppler. This blends into the also echogenic periadventitial region. In normal common carotid arteries that are relatively straight, blood flow is, velocities near the vessel wall and faster velocities near the center. J Vasc Surg. However, the standard deviations around each of these average velocity values are quite large, suggesting that Doppler velocity measurements cannot predict the exact degree of vessel narrowing ( Fig. Use a linear, mid frequency range probe (5-8MHZ). The collecting system could be identified in all kidneys and its wall thickness varied between 0 (not visible) and 0.8 mm. 8.6 What is the temporal tap and how can it be used to differentiate between the internal and the external carotid artery? Ability to use duplex US to quantify internal carotid stenoses: fact or fiction? Hemodynamically significant stenosis of the internal carotid artery (ICA) is usually diagnosed by elevated velocities in a region of luminal narrowing. ICA: The ICA waveforms have broad systolic peaks and a large amount of flow throughout diastole. 3.5B) (14,15). A study by Lee etal. A Carotid ultrasound series should include the following images; To examine the extra-cranial cerebrovascular supply for signs of arterial abnormalities that may be responsible for cerebral or vascular symptoms. The intimal reflection should be straight, thin, and parallel to the adventitial layer. What is normal ICA? Check for errors and try again. Lovelace TD, Moneta GL, Abou-Zamzam a M, et al. ANS: B. With modern equipment, accurate angle correction is acheivable. Locate it in transverse and rotate into longitudinal. A PSV of 35 cm/s is unequivocally normal, whilst a PSV of <25 cm/s following adequate stimulation indicates definite arterial insufficiency. Patient positioned supine on the bed, with head slightly extended over pillow. This leads to a loss of the key lumen-intima interface. d. demonstrate an alternating blood flow pattern. Typically, a 9-MHz linear transducer (or transducer range of 5 to 12MHz) is used. In such situations try imaging the more distal segments of the arteries. 24. 8.2 Which morphologic clues help to distinguish the internal- from the external carotid artery? This will occur at the bifurcation, outside the vessels, possibly exerting extrinsic compression on the carotid artery. normal ICA PSV is <125 cm/sec and no plaque or intimal thickening is visible sonographically additional criteria include ICA/CCA PSV ratio <2.0 and ICA EDV <40 cm/sec <50% ICA stenosis ICA PSV is <125 cm/sec and plaque or intimal thickening is visible sonographically additional criteria include ICA/CCA PSV ratio <2.0 and ICA EDV <40 cm/sec The ICA (located inferiorly and to the right) is typically larger than the ECA (located to the left and upward). Be sure that you are really tapping the temporal artery! Longitudinal brightness-mode view of carotid artery. The modern era of cerebrovascular diagnostics instead utilizes duplex ultrasonography as a minimally invasive tool, capable of assessing not only anatomy but vessel hemodynamics with the use of spectral Doppler imaging. Utilization of multiple criteria may prevent errors in interpretation based on a single measurement. Transversely, the CCA is imaged from its proximal to distal aspects with gray-scale and color Doppler imaging. The former study used the traditional method of grading stenosis, whereas the latter used the NASCET/ACAS approach. The degree of carotid stenosis was characterized by measuring the size of the residual lumen and comparing it with the size of the original vessel lumen ( Fig. Previous studies have shown the importance of internal carotid plaque characterization (see Chapter 6 ). For this reason, peak systolic velocity measurements of the common carotid artery should be obtained approximately 2cm proximal to the carotid bulb [1]. Blood flow signals are not as strong as at peak systole. They are automatically transferred to the ARDMS/APCA CME Bank and RSNA's CME Gateway (when you include your credentials). The carotid bulb and bifurcation should be imaged with gray scale and color Doppler. (Reprinted with permission from the Radiological Society of North America: Grant EG, Duerinckx AJ, El Saden S, etal. Cerebral blood flow (CBF) is commonly inferred from blood velocity measurements in the middle cerebral artery (MCA), using nonimaging, transcranial Doppler ultrasound (TCD). The vascular diagnostic community is divided into two groups: 1) those that perform duplex Doppler examinations using a 60 degree Doppler angle between the ultrasound beam and the vessel axis, and 2) those that use a convenient angle less than or equal to 60 degrees [ 28 ]. In normal common carotid arteries that are relatively straight, blood flow is laminar, meaning that blood cells move in parallel lines with the central blood cells moving faster than the more peripheral blood cells. Elevated velocities can be seen in normal carotid arteries that diverge from a straight line and become curved. The younger patient has higher blood flow velocities 100 cm/sec? It is advisable to place the Doppler sample volume as far distal in the artery as possible. This longitudinal image of the common carotid artery demonstrates a sharp line (specular reflection) that emanates from the intimal surface (arrow). A stenosis of greater than 70% diameter reduction demonstrates a peak-systolic velocity greater than 230 cm/sec. Peak systolic ICA velocities as high as 120 cm/sec have been reported in some normal adults, but these values are exceptional, and an ICA velocity exceeding 100 cm/sec should be viewed as potentially abnormal in older individuals. The test may also be used to: Look at injury to the arteries. Schnke M, Schulte E, Ph.D. LM et-al. Color Doppler also allows you to identify the internal carotid artery by detecting the area of recirculation of the internal carotid bulb. 4A, 4B). ultrasound Ultrasound Longitudinal The external carotid artery has systolic velocities higher than the internal carotid artery, and its waveform is characterized by a sharp rise in flow velocity during systole with a rapid decline toward the baseline and finally return to diminished diastolic flow. Repeated compression (tapping) of the superficial temporal artery (which is located in front of the ear) causes small deflection on the spectral Doppler tracing. Take Doppler samples in the proximal and distal segments and anywhere else that pathology or an altered waveform is detected. Unable to process the form. Other positions of the probe either in more anterior or posterior positions can help with visualization in patients with very distal disease or with large or thick necks. The carotid bulb spans the junction of the internal and external carotid arteries and blends into the dilatation of the sinus along the lateral aspect (opposite the flow divider) of the proximal ICA. ), have velocities that fall outside the expected norm for either PSV or EDV. HTN, young people) 3. Here are two examples. What is normal ECA velocity? The diagnosis of stenotic disease affecting other parts of the carotid system may be clinically important and will also be discussed. To decrease interobserver error, the NASCET and ACAS investigators adopted a different method: comparing the smallest residual luminal diameter with the luminal diameter of the normal ICA distal to the stenosis ( Fig. There is wide variability in the peak systolic velocities seen in normal patients, with a range of 20 to 60 cm/s, with an even wider range noted at the vertebral artery origin (also called segment V0). External carotid artery. 8.3 How can color Doppler help to distinguish the internal from the external artery. The carotid bulb is a functional definition describing the widened portion of the distal CCA extending to the junction of the external and internal carotid arteries (the flow divider; Figure 7-3). Barnett HJ, Taylor DW, Eliasziw M, et al. The external carotid artery (ECA) displays many of the characteristics of a high resistance vessel, including a high pulsatility waveform. An important technical point to be made when calculating the ICA/CCA PSV ratio is that the denominator must be obtained from the distal CCA approximately 2 to 4cm proximal to the bifurcation. Singapore Med J. Background. If you like the way we teach, please leave a message! Criteria for duplex diagnosis of internal carotid stenosis [6]. The Carotid Revascularization Endarterectomy versus Stenting Trial (CREST) comparing CAS with CEA demonstrated a similar reduction in stroke between the two procedures in symptomatic and asymptomatic patients. CCA = common carotid artery. Be aware of the possibility of a Carotid bulb tumour which whilst relatively rare, is a clinically significant finding. Ultrasound of Normal Common Carotid artery (CCA). Variations of the origin and branches of the external carotid artery in a human cadaver. elevators, retractors and evertors of the upper lip, depressors, retractors and evertors of the lower lip, embryological development of the head and neck. The position, size and shape are suggestive of either the internal or external carotid artery. J Vasc Surg. Ku DN, Giddens DP, Zarins CK, Glagov S. Pulsatile flow and atherosclerosis in the human carotid bifurcation. FIGURE 7-4 Long-axis view of the carotid bifurcation. (you can feel the pulse of the temporal artery anterior to the ear). 1995; 273(18):1421-1428. The blue area in the carotid bulb and proximal internal carotid artery represents the normal flow reversal zone. In addition, any benefit of a cerebrovascular screening study depends on the expected risk reduction of any intervention based on screening results. Given that the two velocity values are taken from the same vessel involved by the stenosis, Hathout etal. This is probably related to both a true increase in velocity as blood accelerates around a curve and difficulty in assigning a correct Doppler angle. Likewise, in a situation where a tandem common carotid lesion (in addition to the internal carotid lesion) increases the PSV in the common carotid and lowers the ratio, the use of ICA PSV and/or EDV may continue to provide accurate inference about the lesion severity. 8.1 Why is it important to differentiate the internal- from the external carotid artery with ultrasound? The lumen-intima interface is best seen on longitudinal images when the image plane passes through the center of the artery and the ultrasound beam forms a 90-degree incident angle with the wall interfaces (Figure 7-2; see Video 7-1). The transition between media and adventitia also corresponds to the external elastic lamina as seen on pathologic studies. Velocities vary widely between patients but peak systolic velocities around 77 cm/s have generally been accepted as Stenoses of the external carotid artery (ECA) are not considered clinically important but should be reported because they may explain the presence of a bruit on clinical examination and need to be considered by the surgeon at the time of carotid endarterectomy (CEA). The normal spectral Doppler waveforms differ between the different components of the carotid system. Tortuous segments, kinks, or areas of branching disrupt the normal laminar flow pattern. All three layers can be visualized on ultrasound images (Figure 7-1). All three layers can be visualized on ultrasound images (Figure 7-1). Blood flow is not always laminar in nondiseased vessels since the artery segment has to be straight in order for the conditions of laminar flow to apply. Pellerito J, Polak JF. Several different methods have been utilized in the past to measure carotid stenosis. A normal ICA will have no branches and usually a lower resistance waveform. With the advent of statin (HMG-CoA reductase inhibitors) therapy, studies demonstrated a decreased risk of major vascular events such as stroke and that more aggressive statin treatment further decreased that risk by an additional 16%. Peak systolic velocities (PSV) were assessed with duplex ultrasound (DUS) at baseline, at 30 days, and at 12 and 24 months after . Our data on 707 normal or stenotic ECA nevertheless showed that the systolic peak velocity of the normal ECA (vpECA) and its ratio to the systolic velocity of the CCA (vpECA/vpCCA) are higher than vpICA and vpICA/vpCCA. In the coronal plane, a heel-toe maneuver is used to image the CCA from the supraclavicular notch to the angle of the mandible. Lessthan 60 degrees ( beyond 60degrees, error is exponentially increased). The thickness of the intima cannot be directly imaged from the ultrasound image since it typically measures 0.2 mm or less and is below the resolution of transcutaneous ultrasound. Peak systolic velocities in the CCA tend to parallel the values in the ICAs. What does ICA CCA mean? B, This diagram shows a more typical anatomic definition of the carotid bifurcation. You may also have this test to see if you're a good candidate for angioplasty or to check blood . Endarterectomy for Asymptomatic Carotid Artery Stenosis. {"url":"/signup-modal-props.json?lang=us"}, Gaillard F, Yap J, MacManus D, et al. This should not be mistaken for spectral broadening secondary to pathology. 7.7 ). The NASCET (North American Symptomatic Carotid Endarterectomy Trial) demonstrated that CEA resulted in an absolute reduction of 17% in stroke at 2 years when compared with medical therapy in symptomatic patients with 70% or greater stenosis. 7.5 and 7.6 ). In addition, when statins were started on asymptomatic patients prior to CEA, the incidence of perioperative stroke and early cognitive decline also decreased. Error bars show one standard deviation about mean. Screening has been advocated as a tool for early detection of carotid stenosis and identification of patients who may be at high risk, with potential benefit from carotid intervention. These features are illustrated in Figure 7-6. The bulb is defined as being the zone of dilatation of the common carotid artery (CCA) to the level of the flow divider (the junction of internal carotid artery [ICA] and external carotid artery [ECA]). The Doppler spectrum sampled at this site is shown at the bottom of the image and demonstrates the complex flow pattern with some red cells moving forward and others backward. As the temporal artery is a branch of the ECA, velocity deflections caused by the tapping should be seen on the ECA waveform (Fig. Large, multicenter trials both in North America and Europe confirmed the effectiveness of CEA in preventing stroke in patients with ICA stenoses compared with optimized medical therapy. The outermost echogenic (white) area is the adventitia of the artery. Moderate (50% to 69%) internal carotid artery (, Receiver Operating Characteristic (ROC) curves for three Doppler velocity measurements to detect 70% or greater internal carotid artery (ICA) stenosis: peak systolic velocity (PSV =, Click to share on Twitter (Opens in new window), Click to share on Facebook (Opens in new window), Click to share on Google+ (Opens in new window), on Ultrasound Assessment of Carotid Stenosis, Ultrasound Assessment of Carotid Stenosis, Carotid Sonography: Protocol and Technical Considerations, Normal Findings and Technical Aspects of Carotid Sonography, Ultrasound Assessment of Lower Extremity Arteries, Ultrasound Assessment of the Vertebral Arteries. Long-axis view of the carotid bifurcation. Check for errors and try again. A carotid artery duplex scan is an imaging test to look at how blood flows through the carotid arteries in your neck. The external carotid artery (ECA) is one of the two terminal branches of the common carotid arterythat has many branches that supplies the structures of the neck, face and head. Though controversial, IVC measurement by ultrasound can estimate volume status, fluid responsiveness, and fluid tolerance There is evidence to support that IVC diameter is consistently low in hypovolemia versus euvolemia; IVC change can estimate fluid responsiveness with sensitivity of 0.78 and specificity of 0.86; Can use as a dynamic assessment after intervention such as giving . Also for preoperative screening of patients with known cardio-vascular risk factors. The ratios of of blood flow velocities in the internal carotid artery (ICA) to those in the common carotid artery (CCA) (V ICA /V CCA) are used to identify patients with critical ICA narrowing, but their normal reference values have not been established.We provide reference data for the V ICA /V CCA ratios for the peak systolic velocity (PSV), mean velocity (MV), and end-diastolic . ICA velocities decrease with age, reaching typical values between 60 and 90 cm/sec for ages 60 years and above. Doppler blood flow velocity measurements should be obtained from the proximal and distal CCA and the proximal, mid, and distal ICA. Measurement of degree of stenosis by duplex is assessed using a set of three criteria: internal carotid artery peak systolic velocity, end diastolic velocity (EDV), or the ratio of the ICA PSV to the CCA PSV as measured 2cm below the carotid bulb. ECA vs ICA > BACK TO OVERVIEW Our data on 707 normal or stenotic ECA nevertheless showed that the systolic peak velocity of the normal ECA (vpECA) and its ratio to the systolic velocity of the CCA (vpECA/vpCCA) are higher than vpICA and vpICA/vpCCA. The innermost layer abutting the lumen is the intima, or endothelial lining of the artery. Considerable patient-to-patient variability occurs in ECA flow velocity in normal individuals because pulsatility varies considerably from one person to another since some individuals have a sharply spiked systolic peak, while others have a more blunted peak. In general, for a given diameter of a residual lumen, the calculation of percent stenosis tends to be significantly higher using the pre-NASCET measurement method when compared with the NASCET method ( Fig. There is a moderate amount of blood flow throughout diastole. Especially, since the location of the vessels (and their relationship to each other) vary greatly. Note the smooth echogenic intimal surface. The patient is supine and the neck is slightly extended with the head turned slightly to the opposite side. 7.3 ). The sharp kinks (30 degrees or less) are likely to cause marked, and therefore pathologic, pressure drops (see Video 7-3). The difficulty in estimating the exact location of the plaque-free lumen of the proximal ICA introduced a great degree of interobserver error in estimating the degree of ICA stenosis. ECA lies on these structures), variations in origin arise from the anomalous bifurcation of the, common occipito-auricular trunk (incidence ~12.5%):common origin occipital and posterior auricular arteries. Elevated velocities can also be found with entities other than significant stenosis such as in young athletes, in high cardiac output states, in vessels supplying arteriovenous fistulas or arterial venous malformations, and in patients with carotid stenting. Quantitative evaluation of external carotid artery stenoses is likewise difficult, due to lack of published data and low clinical significance of disease in this vascular distribution. Since the ultrasound transducer typically measures 4 cm, it can be used to help locate this point by placing one end at the level of the bulb and sampling at the mid transducer, or approximately 2 cm below the beginning of the bulb. Providers use this test to diagnose blood clots and peripheral artery disease. The CCA shares the appearance of both waveforms. ECA is crossed by these structures), posteriorly (i.e. revisited an interesting approach to ICA ratio measurements where the ratio of the highest PSV at the site of the stenosis was compared with the normalized velocity in the distal ICA. The average PSV in normal volunteers is between 30 and 40 cm/s. ECA: External carotid artery (ECA) waveforms have sharp systolic peaks, pulsatility due to reflected waves from its branches, and relatively little flow in diastole as compared to the internal carotid artery (ICA). For this reason, the carotid examination should be conducted after the patient has been at rest for 5 to 10 minutes. Calcification can be seen with both homogeneous and heterogeneous plaques. Duplex ultrasonography is able to provide both anatomic and hemodynamic information about the state of a vessel, allowing health care providers to make informed decisions regarding intervention for stroke prevention. The original studies validating intervention in asymptomatic patients showed absolute risk reductions at 5 years of 5-6%, but this number remains in question with continuing improvements in medical management of asymptomatic patients and the lack of recent data [5,6]. In addition, ulcerated plaque that demonstrates a focal depression or break within the plaque is also more prone to plaque rupture and subsequent embolic event ( Fig. The external carotid arteryhas systolic velocities higher than the internal carotid artery, and its waveform is characterized by a sharp rise in flow velocity during systole with a rapid decline toward the baseline and finally return to diminished diastolic flow. A temporal-tap (TT) was employed here to confirm it was the ECA. vpECA/vpCCA is about 2 in > 0-49% ECA stenosis. Significant undulation and thickening of the intima indicate more advanced changes due to atherosclerosis (see Chapter 8) or, rarely, fibromuscular hyperplasia.