Carotid artery disease assessed by color Doppler flow imaging: correlation with standard Doppler sonography and angiography

Carotid artery disease was assessed in 180 patients by means of color Doppler flow imaging. Color Doppler findings in 360 carotid arteries were compared with the results of standard Doppler sonography, and color Doppler findings in 60 bifurcations were compared with the results of intraarterial angiography. The sensitivity of color Doppler for the detection of carotid disease was 100% when compared with angiography. The accuracy of color Doppler in classifying minor (40-60%), moderate (61-80%), and severe (81-90%) stenosis ranged from 91.3% to 97.8% vs standard Doppler sonography, and from 91.7% to 95.8% vs angiography. Whereas all occlusions were identified correctly by both color Doppler and angiography, four pseudoocclusions of the carotid artery were misdiagnosed as occluded. Characteristic features providing reliable criteria of the degree of stenosis are (1) intensity, extent, and duration of color fading; (2) postprocessed systolic peak frequency; (3) plaque extent on serial sonograms; and (4) poststenotic flow patterns. Display of hemodynamic disturbances induced by less pronounced plaques showed highly variable patterns that could not be anticipated from the plaque morphology alone. Thus, color Doppler preserves the advantages of standard Doppler and duplex sonography but provides additional information about otherwise anechoic necrotic and thrombotic material that often causes cerebral embolisms. With atherogenesis, repair mechanisms may be sustained or progression be stopped by reducing the risk factors and instituting medical treatment; thus, the application of this noninvasive technique is important.     

Carotid artery disease assessed by color Doppler flow imaging: correlation with standard Doppler sonography and angiography

Carotid artery disease was assessed in 180 patients by means of color Doppler flow imaging. Color Doppler findings in 360 carotid arteries were compared with the results of standard Doppler sonography, and color Doppler findings in 60 bifurcations were compared with the results of intraarterial angiography. The sensitivity of color Doppler for the detection of carotid disease was 100% when compared with angiography. The accuracy of color Doppler in classifying minor (40-60%), moderate (61-80%), and severe (81-90%) stenosis ranged from 91.3% to 97.8% vs standard Doppler sonography, and from 91.7% to 95.8% vs angiography. Whereas all occlusions were identified correctly by both color Doppler and angiography, four pseudoocclusions of the carotid artery were misdiagnosed as occluded. Characteristic features providing reliable criteria of the degree of stenosis are (1) intensity, extent, and duration of color fading; (2) postprocessed systolic peak frequency; (3) plaque extent on serial sonograms; and (4) poststenotic flow patterns. Display of hemodynamic disturbances induced by less pronounced plaques showed highly variable patterns that could not be anticipated from the plaque morphology alone. Thus, color Doppler preserves the advantages of standard Doppler and duplex sonography but provides additional information about otherwise anechoic necrotic and thrombotic material that often causes cerebral embolisms. With atherogenesis, repair mechanisms may be sustained or progression be stopped by reducing the risk factors and instituting medical treatment; thus, the application of this noninvasive technique is important.     

Detection of clinically silent intracranial emboli ipsilateral to internal carotid occlusions during cerebral angiography

OBJECTIVE: Embolic ischemic events have long been suspected to occur in the cerebral arteries distal to an ipsilateral occluded internal carotid artery (ICA). Documentation of microemboli by transcranial Doppler sonography during catheter angiography in patients with ICA occlusions provides objective evidence of such distal emboli. SUBJECTS AND METHODS: Seven patients undergoing carotid angiography were evaluated with transcranial Doppler sonography. Patients were also screened for ICA occlusions using carotid duplex sonography. In the seven patients, we saw five right ICA occlusions and two left ICA occlusions. Real-time visual and auditory confirmations of emboli were obtained by recognizing their specific spectral signatures and harmonic qualities. Routes of collateral flow were determined from angiography. Specific phases of the examination were correlated with embolic occurrences. RESULTS: Overall, emboli were seen during all phases of arteriography. In the individual patients, emboli were identified in one to four of the eight angiographic phases we defined. Most emboli occurred during catheter flushing and contrast injection rather than during wire and catheter manipulation. The emboli were detected in the middle cerebral artery distribution ipsilateral to the occluded ICA in all seven patients. Collateral flow patterns included, in four patients, external carotid artery-to-ICA collateral flow; in all seven patients, patent anterior communicating arteries; and in three patients, patent posterior communicating arteries. CONCLUSION: Emboli seen in middle cerebral arteries ipsilateral to occluded ICAs during cerebral angiography strongly indicate that emboli can occur distal to an occlusion. Our findings support the thought that emboli arising from sources proximal to an occluded ICA may reach the hemisphere distal to the occlusion, resulting in parenchymal ischemia or infarction.     

Colour doppler flow imaging of the carotid arteries

Summary 53 patients with carotid artery atherosclerosis were examined by colour Doppler flow imaging. These results were compared with real time duplex sonography and continuous wave Doppler sonography. In 48 low degree stenoses (<50%) the B-mode showed 36 smooth and 12 ulcerated plaque surfaces. In 24 high degree stenoses (>50%) 10 plaques were smooth and 14 ulcerated. In the low degree stenoses, which exhibited smooth surfaces in B-mode examination, colour flow Doppler showed nine additional cases with turbulences in the area of the stenotic site. This indicates that plaque ulcerations in low degree stenoses are underestimated. In contrast, in nearly all cases with high degree stenoses marked turbulences could be demonstrated by colour Doppler flow imaging independent of the B-mode showing regular or ulcerated plaque surfaces. Additionally, the duplex ultrasound diagnosed a carotid artery occlusion in 11 cases, but the colour coded Doppler was able to assess a remaining blood flow in two out of these 11 cases. Our results suggest that the colour Doppler flow imaging as a noninvasive technique is an advantage in diagnosing plaque ulcerations and it is more precise in diagnosing carotid occlusions than duplex-sonography is.     

Extracranial internal carotid artery Salmonella mycotic aneurysm complicated by occlusion of the internal carotid artery: depiction by Color Doppler sonography,CT and DSA

Mycotic aneurysms of the extracranial carotid artery are rare. Seventy-four cases have been described in the medical literature and only eight secondary to Salmonella infection. To our knowledge, color Doppler sonography, computed tomography (CT), and digital subtraction angiography (DSA) findings relating to the diagnosis and follow-up of extracranial internal carotid artery mycotic aneurysm complicated by occlusion have not previously been described in the literature. We present a report of color Doppler sonography, CT, and DSA findings of a mycotic aneurysm of the right extracranial internal carotid artery due to Salmonella associated with occlusion of the internal carotid artery, promptly diagnosed and followed up using these imaging modalities.     

Duplex Doppler ultrasound for the detection of vascular occlusion following liver transplantation in children.

Sixty-three children and adolescent patients who received 78 consecutive orthotopic liver transplants and had serial duplex ultrasound monitoring were retrospectively reviewed for episodes of occlusion of the hepatic artery or portal vein. There were 13 documented episodes of complete occlusion of the main hepatic artery or a major branch, of which nine were diagnosed by the absence of flow during duplex ultrasound examination. Four occlusions were not detected, two affected hepatic artery branches, one an accessory hepatic artery, and one the main hepatic artery. The overall sensitivity of the method was 69% and specificity 100%. Six portal vein occlusions were documented in five patients and all six were successfully diagnosed on ultrasound examination, giving a sensitivity and specificity of 100%. Three of the patients had simultaneous occlusions of both vessels. In the early post-operative period duplex Doppler ultrasound examination has proved an effective non-invasive method for the detection of vascular occlusion, but is not yet sensitive enough to replace angiography fully for the detection of hepatic artery occlusion, particularly when this occurs distal to the main hepatic artery.     

Duplex sonography in the evaluation of carotid artery disease

High-resolution duplex sonography was compared with biplane magnified carotid angiography in a prospective evaluation of 161 carotid arteries in 86 patients. The duplex scanner combined real-time B-mode imaging (7.5 MHz) with simultaneous range-gated pulsed Doppler frequency analysis (3 MHz). The degree of stenosis was usually determined by the true and residual lumen of the carotid artery at the atherosclerotic plaque on the transverse image. The Doppler frequency signals were automatically converted to velocity data by a minicomputer. The accuracy of the duplex system in detecting and assessing stenoses graded in 20% increments is demonstrated according to specificity, sensitivity, and positive and negative predictive value by both cumulative and subgroup analyses. A 93.7% sensitivity was shown for minimal (0-20%) stenosis and 100% sensitivity for severe (greater than 60%) stenosis. An apparent limitation of duplex sonography is the differentiation of a high-grade stenosis from occlusion (sensitivity, 82.6%; positive predictive value, 90.4%).     

Common carotid artery occlusion: evaluation with duplex sonography.

PURPOSETo demonstrate the efficacy of carotid duplex ultrasound to diagnose common carotid artery occlusion (CCAO) and to define the clinical features of CCAO.METHODSWe reviewed 5400 carotid duplex ultrasonograms obtained over a 7-year period for suspected carotid artery disease. In cases of CCAO, medical records were reviewed.RESULTSThirteen cases (0.24%) of CCAO were diagnosed by carotid duplex ultrasonography, including five cases of isolated CCAO. Seven cases were proved by cerebral angiography. Cerebral angiography failed to demonstrate patent internal carotid arteries in two cases of isolated CCAO. Mean age of onset was 67 +/- 9 years. The main clinical presentation was stroke in nine cases (69%). The most common vascular risk factors were hypertension (62%) and heart diseases (54%). Three patients had a history of radiation therapy to the neck. Two of five patients with isolated CCAO had major stroke, with good recovery in one, whereas five of eight patients with CCAO had major stroke; among them, only one had good recovery.CONCLUSIONPatients with isolated CCAO may have a better outcome than patients with CCAO. Duplex sonography, particularly with color-coded flow imaging, provides an accurate examination to define the patency of the arteries distal to the carotid bifurcation. The clinical features of CCAO are similar to those of internal carotid artery occlusion except for the low prevalence of CCAO.     

Transcranial Doppler ultrasound in the evaluation of collateral blood flow in patients with internal carotid artery occlusion: correlation with cerebral angiography.

PURPOSETo determine the accuracy of transcranial Doppler (TCD) ultrasound for evaluation of collateral supply through the circle of Willis in patients with internal carotid artery (ICA) occlusion.METHODSThe evaluation of the collateral pathways through the circle of Willis with TCD ultrasound and with cerebral angiography was compared in 40 patients (30 men, 10 women; mean age, 55 +/- 9 years) in a total of 44 ICA occlusions of which 43 had a suitable ipsilateral temporal bone window for TCD examination.RESULTSBy TCD, a patent anterior communicating artery is indicated by a reversal blood flow in the A1-segment of the anterior cerebral artery or by a prompt fall of blood velocity in the middle cerebral artery after compression of the nonoccluded contralateral carotid artery. In 42 of 43 instances of ICA occlusion, TCD and angiography agreed in the evaluation of a present or absent anterior communicating artery collateral supply. TCD''s sensitivity was 95%, its specificity 100%. A collateral supply through the basilar artery was assumed with TCD when there was: (a) a basilar artery blood velocity of more than 70 cm/s; (b) a marked increase of basilar artery blood velocity after compression of the nonoccluded carotid artery; (c) an evident side-to-side asymmetry of the blood velocity of the posterior cerebral arteries with high blood velocity ipsilateral to the ICA occlusion. For evaluating the collateralization via the basilar artery, TCD and angiography agreed in 37 of 40 ICA occlusions. TCD''s sensitivity was 87%, its specificity 95%.CONCLUSIONSTCD is a reliable tool for the evaluation of the collateral supply in patients with ICA occlusions.     

Duplex Doppler sonography of the carotid artery: false-positive results in an artery contralateral to an artery with marked stenosis

Anecdotal reports have described a false-positive "jet effect" or velocity increase in the carotid artery contralateral to an artery with significant stenosis or occlusion when using duplex Doppler sonography. In this study, the frequency, significance, and possible reasons for this finding were evaluated by a retrospective comparison of duplex sonography and angiography. Twenty-three patients with unilateral 81-100% carotid artery stenosis who underwent both duplex sonography (16 Acuson, seven Quantum) and angiography were evaluated. In 14 patients, there was an accurate or slight underestimate (less than 20%) of stenosis present in the internal carotid artery contralateral to an artery with tight stenosis/occlusion. In nine, a velocity increase in the internal carotid artery resulted in overestimation (10-80%) of the actual degree of stenosis. In one of these nine patients, real-time images were sufficient to explain the velocity increase on the basis of vessel tortuosity. In one, falsely elevated velocity resulted from inaccurate assignment of the Doppler angle of incidence in a patient in whom real-time visualization of a distal internal carotid lesion was poor. In four of the nine patients, cross filling via the circle of Willis toward the side of greater stenosis occurred. However, seven of 14 patients in whom there was duplex sonography/angiography agreement or slight duplex sonography underestimation also had cross filling. Vertebral artery patency did not correlate well with the presence of a "jet effect." These findings suggest that an increase in blood flow velocity with duplex Doppler sonography in the internal carotid artery on the side opposite an artery with a tight stenosis is a common source of error and is not readily explained by angiographic evidence of collateral flow.     

Transorbital color Doppler flow imaging of the carotid siphon and major arteries at the base of the brain.

PURPOSETo describe and evaluate an application of sonography, transorbital color Doppler flow imaging of the carotid siphon and major intracranial arteries, and to compare it with transtemporal color Doppler flow imaging.METHODSThe carotid siphon and major arteries at the base of the brain of 50 healthy volunteers were screened using the transorbital color Doppler flow sonography. These arteries were also studied by a transtemporal approach for comparison. In 5 volunteers, MR images in special inclination planes were obtained and compared with the transorbital color-coded Doppler flow images.RESULTSThe B-mode image of the orbit and intracranial anatomic structures, in addition to the color-coded flow images, provided an unambiguous identification of the carotid siphon and major intracranial arteries. The failure rate was lower when using the transorbital approach than when using the transtemporal approach in identifying the anterior cerebral artery (17% versus 32%). Color Doppler flow imaging using the transtemporal approach was better for the middle cerebral artery, whereas color Doppler flow imaging using the transorbital approach was better for the anterior cerebral artery (contralateral). The Doppler incident angles using the transorbital approach were better for the carotid siphon and anterior cerebral artery (contralateral).CONCLUSIONTransorbital color Doppler flow imaging, when used in conjunction with the transtemporal examination, can add information concerning the major arteries at the base of the brain.     

Angioplasty of the occluded internal carotid artery.

PURPOSETo review patients who have presented with acute strokes from a middle cerebral artery occlusion in whom in addition to the middle cerebral artery thromboembolus, an internal carotid artery occlusion has been present, and in whom angioplasty of these totally occluded internal carotid arteries has bee n successful.METHODSWe reviewed retrospectively our experience in treating a cute stroke patients with intracranial, intraarterial urokinase. Six of 27 patients had internal carotid artery occlusions in addition to middle cerebral artery occlusions. Two patients presented with spontaneous carotid dissections for wh ich no further intervention from the ipsilateral internal carotid artery was attempted. In the remaining four internal carotid artery occlusions secondary to atherosclerotic disease, standard guide wires and catheters were negotiated across the level of the internal carotid artery occlusion, which expedited intracranial catheterization for thrombolysis. Subsequently, angioplasty of the internal carotid artery was performed.RESULTSAll four occluded internal carotid arteries could be traversed. No new neurologic deficits occurred. No vascular injuries occurred. No deaths occurred. Four- to 6-month follow-up showed all four internal carotid arteries remained patent.CONCLUSIONIn acute occlusions of the internal carotid artery from atherosclerosis, the occluded vessel can sometimes be recanalized with low morbidity. In addition, endovascular access to the intracranial circulation can be expedited by using the recanalized internal carotid artery.     

Diagnosis of middle cerebral artery occlusion with transcranial color-coded real-time sonography.

PURPOSETo determine the usefulness of transcranial color-coded real-time sonography in detecting occlusion of the horizontal portion of the middle cerebral artery.METHODSUsing transcranial color-coded real-time sonography, we measured the end-diastolic flow velocity with incident angle correction and the side-to-side ratio of the end-diastolic flow velocity (the end-diastolic ratio) in both middle cerebral arteries in 44 patients with or without occlusive disease. Cerebral angiography was carried out in all patients before or within 1 week after sonography. The subjects included 4 patients with unilateral stenosis of the extracranial internal carotid artery > or = 75%; ICS group), 6 with unilateral occlusion of the extracranial internal carotid (ICO group), 6 with occlusion of the horizontal portion of the middle cerebral artery (M1 group), and 28 without stenotic (< 75%) lesions in the internal carotid artery (control group).RESULTSIn the control group, the end-diastolic flow velocity was 40.4 +/- 16.8 cm/s (mean +/- SD) and the end-diastolic ratio was 1.28 +/- 0.27. In the ICS and ICO groups, the end-diastolic flow velocities on the affected side and the end-diastolic ratios were 33.4 +/- 9.0 cm/s and 1.35 +/- 0.24, and 29.6 +/- 10.2 cm/s and 1.67 +/- 0.58, respectively. In the M1 group, the end-diastolic flow velocity (16.7 +/- 4.29 cm/s) on the occluded side was significantly lower than that in the other groups. The end-diastolic ratio (3.53 +/- 1.47) in the M1 group was significantly higher than that in the other groups.CONCLUSIONThe M1 group could be easily distinguished from the other groups on the basis of the end-diastolic ratio. Measurement of the end-diastolic flow velocity and the end-diastolic ratios in the middle cerebral artery by means of transcranial color-coded real-time sonography may help to identify an occlusion in the horizontal portion of the middle cerebral artery.     

A prospective comparison of duplex sonography vs angiography of the vertebral arteries

A prospective blind comparison was completed between duplex sonography and angiography of the vertebral arteries. Thirty-two vertebral arteries were studied for direction of flow, degree of origin plaque or stenosis, Doppler characteristics, and vessel size. The vertebral arteries were reliably identified by imaging their course from the subclavian artery into the transverse foramina and by identifying a Doppler signal similar in waveform to the internal carotid artery. With Doppler, a 90% accuracy was obtained for direction of blood flow. Nonvisualization of origins was primarily due to vessel depth and/or tortuosity. In 12 vessel origins that were well seen with both techniques, angiography and sonography agreed in two-thirds of the cases. In four cases, origin plaque was underestimated with duplex imaging. Interestingly, no Doppler frequency or velocity elevation was identified distal to significant stenoses. One false-positive diagnosis of occlusion occurred with sonography, in which a 99% origin stenosis resulted in no detectable Doppler signal. By comparing sonography with angiography, sonography was shown to be 80% accurate in determining vertebral artery size. Our preliminary results indicate that duplex scanning is a reasonably accurate screening technique for size, patency, and direction of blood flow in the vertebral arteries. Duplex evaluation of the vertebral artery origin was limited by vessel depth, tortuosity, and calcifications.     

Balloon test occlusion of the internal carotid artery with hypotensive challenge.

PURPOSETo evaluate the usefulness of provocative testing with hypotensive challenge during balloon test occlusion of the internal carotid artery before carotid sacrifice and to correlate tolerance of balloon test occlusion with clinical outcome after carotid artery sacrifice.METHODSForty-seven consecutive cases of balloon test occlusions performed at our institution during the past 4 years were retrospectively reviewed. Occlusion was performed under normotensive conditions with distal perfusion of heparinized saline for 20 minutes, or until a deficit was perceived. If 20 minutes of normotension was tolerated, hypotension was induced to two thirds of mean arterial pressure for 20 minutes, or until a deficit was perceived.RESULTSOf 47 patients, 4 (9%) had deficits at normotension. Of the remaining 43 patients, 9 (21%) had deficits at hypotension. One patient with a positive hypotensive test occlusion underwent carotid artery sacrifice after extracranial-intracranial bypass without sequelae. In one of the 19 patients who clinically tolerated test occlusion with hypotension and had carotid sacrifice (surgical ligation of the intracranial carotid artery), a mild embolic stroke developed, probably from the giant carotid wall aneurysm. This patient fully recovered; MR imaging showed mild changes consistent with emboli distal to the aneurysm. Symptomatic complications were noted in 2 (4%) patients, and asymptomatic arterial dissections were noted in 3 (6%) patients.CONCLUSIONBalloon test occlusion with hypotensive challenge is safe, economical, and greatly increases the sensitivity of balloon test occlusion. The predictive value of a negative test is high. However, to determine the test''s specificity compared with quantitative imaging, controlled trials will be necessary.     

Temporary balloon test occlusion of the internal carotid artery: experience in 500 cases.

PURPOSETo describe experience with 500 temporary balloon occlusions of the internal carotid artery, with particular emphasis on the techniques and complications.METHODSTemporary occlusion of the internal carotid artery was accomplished endovascularly using various balloon-catheter combinations. These temporary balloon occlusions were combined, when possible, with cerebral blood flow analysis with stable xenon-enhanced CT.RESULTSComplications related to this procedure occurred in 16 (3.2%) patients. Eight (1.6%) patients had asymptomatic complications. There were 8 who experienced neurologic changes. Six (1.2%) of these were transient; two (0.4%) were permanent. There were no deaths.CONCLUSIONSTemporary balloon occlusion of the internal carotid artery, believed helpful in identifying patients at risk of stroke during abrupt carotid artery sacrifice, can be performed with an acceptably low complication rate.     

Accuracy of three-dimensional gadolinium-enhanced MR angiography in the assessment of extracranial carotid artery disease

OBJECTIVE: The purpose of this study was to assess three-dimensional (3D) gadolinium-enhanced MR angiography, used alone or in association with duplex Doppler sonography, with a fast acquisition time (8 sec) for evaluating the extracranial carotid arteries. SUBJECTS AND METHODS: In this prospective study, 48 successive patients with carotid artery stenoses were examined with 3D gadolinium-enhanced MR angiography and 3D time-of-flight MR angiography. Of the 44 eligible patients, conventional angiography was available in 33 and duplex sonography in 27. We used the North American Symptomatic Carotid Endarterectomy Trial technique to quantify stenosis on all angiograms, and a 250 cm/sec threshold at duplex sonography to diagnose stenoses greater than 70%. Image quality of 3D gadolinium-enhanced MR angiography and 3D time-of-flight MR angiography was assessed, as well as sensitivity and specificity for each technique alone and in combination with duplex sonography. Conventional angiography was the gold standard. RESULTS: Three-dimensional gadolinium-enhanced MR angiography yielded good image quality in 90% of cases. When used alone, it yielded a sensitivity and a specificity of 94% and 85%, respectively, in screening stenoses greater than 70% (70-99%). When combined with duplex Doppler sonography, it provided a 100% sensitivity and specificity for detection of stenoses between 70% and 99% and would have obviated 61% of conventional angiography. In comparison, 3D time-of-flight MR angiography used alone yielded a sensitivity of 88% and a specificity of 94%. In combination with duplex Doppler sonography, its use would have obviated conventional angiography in 74% of cases. Three-dimensional gadolinium-enhanced MR angiography provided accurate results in the diagnosis of occlusions and ulcers and can visualize distant stenoses. CONCLUSION: Used alone, 3D gadolinium-enhanced MR angiography is not accurate enough to replace conventional angiography in the evaluation of extracranial carotid arteries. In association with duplex Doppler sonography, however, it is accurate and may obviate a significant number of conventional angiographic examinations.     

Endovascular occlusion of the carotid or vertebral artery with temporary proximal flow arrest and microcoils: clinical results.

PURPOSETo determine the clinical effectiveness of parent artery occlusion of the carotid or vertebral artery by means of temporary proximal flow arrest and microcoils.METHODSNineteen parent artery occlusions (15 carotid, four vertebral) were performed in 19 patients who successfully passed a balloon test occlusion. In these patients, endovascular occlusion of the carotid or vertebral artery was accomplished with the use of temporary proximal flow arrest and microcoils.RESULTSAll 19 parent arteries were occluded. Eighteen patients (95%) had good outcomes and one (5%) had a poor outcome. Fourteen patients (74%) had no complications and five (26%) had complications, of whom only one was left with a permanent neurologic deficit. Three (60%) of the complications were the result of delayed ischemic events after parent artery occlusion and were not predicted by balloon test occlusion.CONCLUSIONEndovascular occlusion with temporary proximal flow arrest and microcoils can be done effectively and successfully. The predictive value of the balloon test occlusion is the major complicating factor, as it is with balloon occlusion. This technique offers an additional tool that can be used for endovascular occlusion of the carotid or vertebral artery and seems to be less difficult technically. It is our primary technique for parent artery occlusion.     

The detection of intracranial carotid artery disease by continuous-wave Doppler sonography

Summary We have investigated 6,587 patients with directional continuous-wave (c-w) Doppler sonography of the carotid arteries during the last 33 months, and have developed criteria for the diagnosis of a significant increase in peripheral resistance of the internal carotid artery in conjunction with 1,671 retrograde brachial and direct carotid angiograms. We distinguished stenoses proximal (15 cases) and distal (4) to the origin of the ophthalmic artery, supraclinoid internal carotid artery occlusions (8), stenoses (2) and acute occlusions (10) of the middle cerebral artery. Stenoses in the carotid siphon (proximal or distal to the origin of the ophthalmic artery) of at least 60% reduction in lumen diameter showed a reduction of the relative end-diastolic flow velocity (modified Pourcelot's index) of more than 40%; additionally, stenoses proximal to the origin of the ophthalmic artery exhibited a variable alternating flow, or flow reversal, in the supratrochlear artery. Stenoses distal to the origin of the ophthalmic artery rarely revealed the theoretically expected increase in orthograde flow velocity in the supratrochlear artery. Stenoses of the middle cerebral artery consisting of more than atherosclerotic irregularities proved to be an exception. Supraclinoid occlusions of the internal carotid artery were reliably demonstrated by Doppler sonography. However, the majority of acute occlusions of the middle cerebral artery could not be detected by this means, probably due to anastomoses between the anterior and the middle cerebral arteries, which were detected by angiography. Thus, we believe that c-w Doppler sonography is a reliable tool to detect stenoses of the carotid siphon of more than 60% reduction in lumen diameter and supraclinoid carotid artery occlusions. Barriers to the cerebral blood flow located more peripherally cannot be diagnosed reliably with this technique.     

Duplex Doppler sonography of the carotid artery: false-positive results in an artery contralateral to an artery with marked stenosis

Anecdotal reports have described a false-positive "jet effect" or velocity increase in the carotid artery contralateral to an artery with significant stenosis or occlusion when using duplex Doppler sonography. In this study, the frequency, significance, and possible reasons for this finding were evaluated by a retrospective comparison of duplex sonography and angiography. Twenty-three patients with unilateral 81-100% carotid artery stenosis who underwent both duplex sonography (16 Acuson, seven Quantum) and angiography were evaluated. In 14 patients, there was an accurate or slight underestimate (less than 20%) of stenosis present in the internal carotid artery contralateral to an artery with tight stenosis/occlusion. In nine, a velocity increase in the internal carotid artery resulted in overestimation (10-80%) of the actual degree of stenosis. In one of these nine patients, real-time images were sufficient to explain the velocity increase on the basis of vessel tortuosity. In one, falsely elevated velocity resulted from inaccurate assignment of the Doppler angle of incidence in a patient in whom real-time visualization of a distal internal carotid lesion was poor. In four of the nine patients, cross filling via the circle of Willis toward the side of greater stenosis occurred. However, seven of 14 patients in whom there was duplex sonography/angiography agreement or slight duplex sonography underestimation also had cross filling. Vertebral artery patency did not correlate well with the presence of a "jet effect."(ABSTRACT TRUNCATED AT 250 WORDS)