Direct B-mode NASCET-style stenosis measurement and Doppler ultrasound as parameters for assessment of internal carotid artery stenosis

Doppler ultrasound grading of internal carotid artery (ICA) stenosis using the two parameters of spectral analysis and internal carotid to common carotid artery peak systolic velocity (ICA/CCA PSV) ratio is well established. The improvements in B-Mode ultrasound image quality now make direct ultrasound NASCET-style stenosis measurement possible. We demonstrate that longitudinal B-mode imaging can produce accurate North American Symptomatic Carotid Endarterectomy Trial (NASCET) style measurements which have good correlation with angiographic images. Ultrasound B-mode stenosis measurement provides a third parameter which can be used in conjunction with the two Doppler parameters for the assessment of ICA stenosis. Taking the highest grade of stenosis of the three parameters produces a sensitivity of 100% for the detection of greater than 50% and greater than 80% stenosis with specificity of 66 and 90%, respectively. The performance of satisfactory B-mode imaging against digital subtraction angiography (DSA) was very encouraging. When the B-mode stenosis measurement showed a normal ICA, the positive predictive value (PPV) of the DSA being normal was 94%. When the B-mode stenosis measurement was 35% or less, the PPV of the DSA stenosis being 35% or less was 93%. These excellent results support the use of good quality B-Mode NASCET style stenosis measurement as the initial ultrasound measurement, with Doppler ultrasound only being performed when the B-mode stenosis measurement is greater than 35% or if the B-mode image is unsatisfactory. This approach would save considerable time enabling better utilization of ultrasound resources.     

Reappraisal of flow velocity ratio in common carotid artery to predict hemodynamic change in carotid stenosis

BACKGROUND AND PURPOSE: Various Doppler criteria have been used to predict hemodynamically significant carotid stenosis. This study was performed to elucidate whether hemodynamically significant stenosis can be predicted indirectly by the blood flow velocity in the common carotid artery (CCA) measured with duplex ultrasonography in patients with unilateral stenosis of internal carotid artery (ICA). METHODS: Eighty-five patients who were scheduled to undergo carotid endarterectomy for unilateral stenosis of ICA origin were analyzed. The flow velocities and their side-to-side ratios in the CCA were calculated. The flow velocities in the CCA were measured with conventional ultrasonography and poststenotic blood flow with transoral carotid ultrasonography. Cerebral angiography was performed to evaluate the intracranial collateral flow. RESULTS: Among the absolute values and side-to-side ratios of Doppler flow velocities in the CCA, the end diastolic flow velocity (EDV) ratio in the CCA best correlated with the residual lumen area (r = 0.35; P = .0009), stenosis of diameter (r = 0.48; P < .0001), and poststenotic flow (r = 0.60; P < .0001). EDV ratios in the CCA were significantly lower in patients with collateral pathways (anterior communicating artery, P = .0005; posterior communicating artery, P = .004; ophthalmic artery, P < .0001; leptomeningeal collateral, P = .004). The optimal threshold value of the EDV ratio in the CCA for the presence of intracranial collateral flow and stenosis of diameter > or = 70% was 1.2. Those for tight stenosis in a cross-sectional area >95%, the reduction of poststenotic flow, and poststenotic narrowing were 1.4, 1.5, and 1.6, respectively. CONCLUSION: The EDV ratio in the CCA appears to be an additional parameter for predicting hemodynamically significant stenosis in patients with unilateral ICA stenosis.     

Assessment of stenosis: implications of variability of Doppler measurements in normal-appearing carotid arteries.

PURPOSE: To examine the variability of Doppler measurements along the extra-cranial courses of the nondiseased common carotid artery (CCA) and internal carotid artery (ICA) and determine the effect of this variability on assessment of carotid arterial stenosis. MATERIALS AND METHODS: During the study period, 580 patients were referred for carotid arterial ultrasonography (US), including Doppler measurements of flow velocities in the proximal, middle, and distal portions of the CCA, in the bulb, and in the proximal and distal portions of the ICA. Eighty-five patients (average age, 59 years) with normal ICAs and CCAs formed the cohort for this study. RESULTS: The range of peak systolic velocity (PSV) measurement (maximum minus minimum) averaged 20 cm/sec +/- 13 in the CCA and 15 cm/sec +/- 13 in the ICA. ICA/CCA velocity ratios varied, depending on the CCA measurement location. In five arteries, PSV ratios exceeded a threshold of 1.8 (suggesting > or = 60% stenosis); in 23 arteries, end diastolic velocity ratios exceeded a threshold of 2.4 (also suggesting > or = 60% stenosis). Right-to-left CCA PSV ratios were abnormal in up to 26 patients (suggesting > 50% ICA stenosis), depending on where CCA measurements were obtained. When the CCA ratios were obtained at the same level, 16 were in the abnormal range. CONCLUSION: Variability of Doppler measurements in the CCA and ICA in patients without visible disease is substantial and could lead to inaccuracies in carotid arterial stenosis assessment.     

彩色双功能超声在诊断颈内动脉粥样硬化狭窄中的临床应用

目的:探讨彩色双功能超声在颈内动脉粥样硬化狭窄中的临床应用价值。方法:对58例由于动脉粥样硬化导致颈内动脉狭窄的患者进行二维超声及彩色多普勒血流显像检查,并利用脉冲多普勒对动脉血管狭窄处及狭窄前的血流信号进行测量,同时测量颈总动脉的血流速度。结果:通过测量颈内动脉狭窄处收缩期峰值流速和舒张末期血流速度、颈总动脉收缩期峰值流速和舒张末期血流速度,将二者血流速度相比较并进行分析,同时与彩色多普勒血流显像通过狭窄处血管面积的变化所测的狭窄程度相对照,共检出62支颈内动脉狭窄,其中5支颈内动脉血管腔内血栓形成。二者相结合诊断颈内动脉狭窄的灵敏性和准确性分别为96%和94%。结论:彩色双功能超声在颈内动脉狭窄的诊断中具有重要的临床价值。     

Comparison of two Doppler ultrasound criteria for grading cervical internal carotid artery stenosis

In a review of 49 carotid arteries that had been assessed by ultrasound and angiography, two Doppler criteria were compared for accuracy in grading internal carotid artery (ICA) stenosis. The Seattle criteria for Doppler spectral analysis and the internal-to-common carotid artery peak systolic velocity ratio were of similar accuracy. When used in combination, there was an increase in sensitivity compared with the use of a single criterion. The velocity ratio had a higher sensitivity for detection of high-grade stenosis, but it tended to overestimate the grade of stenosis more than the Seattle criteria. To increase the sensitivity for detection of severe stenosis, the criteria should be used together and the higher grade of stenosis should be taken if there is a mismatch in assessment.     

Detection of internal carotid artery stenosis: comparison of MR angiography, color Doppler sonography, and arteriography.

Findings of two-dimensional time-of-flight magnetic resonance (MR) angiography projection angiograms were prospectively compared with those of color Doppler sonography by using angiography as a standard in 23 consecutive patients (42 carotid bifurcations) to evaluate their utility in determining the presence of carotid artery stenosis. MR angiography helped detect 50% or greater lumen diameter stenosis (sensitivity, 0.96; specificity, 0.64). Color Doppler sonography with 1.25 m/sec peak systolic velocity as a threshold had a sensitivity of 0.96 and a specificity of 0.71. Statistical analysis showed a correlation between percentage of lumen diameter narrowing and the length of the zone of signal intensity loss with MR angiography (r = .69; P less than .0001). A stronger relationship was obtained between angiographic narrowing and peak systolic velocity derived from color Doppler sonography (r = .80; P less than .0001). Two-dimensional time-of-flight MR angiography displayed as projection angiograms and combined with carotid artery and combined with carotid artery sonography is a useful approach for helping detect and potentially grade the severity of stenoses of the carotid artery.     

Diagnosis of internal carotid artery stenosis greater than 70% with power Doppler duplex sonography

BACKGROUND AND PURPOSE: Duplex sonography is an effective tool for evaluating internal carotid artery (ICA) stenosis, and power Doppler imaging has improved its value in this regard. Our goal was to elucidate which parameters, such as linear stenosis, area stenosis, and peak systolic velocity (PSV), are the most reliable predictors of ICA stenosis greater than 70% using the method proposed by the North American Symptomatic Carotid Endarterectomy Trial (NASCET). METHODS: Duplex sonography with power Doppler imaging and cerebral angiography were performed prospectively in 75 patients (135 vessels). The grade of stenosis on angiograms was calculated by the NASCET method, and linear stenosis, area stenosis, and PSV were measured in the most stenotic part of the ICA. RESULTS: Angiography revealed 20 ICA vessels with stenosis greater than 70%. The correlation between angiographic stenosis and linear stenosis, area stenosis, and PSV was .82, .78, and .84, respectively. A sensitivity-specificity curve analysis determined optimal threshold values of linear stenosis, area stenosis, and PSV as predictors of ICA stenosis greater than 70% as 74.7%, 83.3%, and 200 cm/s, respectively. Calculations of positive and negative predictive values, and accuracy using the optimal threshold values were 90.5%, 99.1%, and 97.8% for linear stenosis; 76.0%, 99.1%, and 94.8% for area stenosis; and 100%, 100%, and 100% for PSV. CONCLUSION: All parameters corresponded relatively well with angiographic stenosis. In particular, PSV greater than 200 cm/s was the most reliable predictor of ICA stenosis greater than 70%. We believe that the combination of parameters plays a crucial role in the accurate assessment of ICA stenosis.     

Variability of Doppler US measurements along the common carotid artery: effects on estimates of internal carotid arterial stenosis in patients with angiographically proved disease

PURPOSE: To determine the effect of variability of common carotid arterial (CCA) velocities on velocity ratios used to assess internal carotid arterial (ICA) stenosis. MATERIALS AND METHODS: Doppler ultrasonographic (US) velocity measurements were obtained at three levels in the CCA and in the carotid bulb and ICA in all patients referred for carotid US between September 1996 and October 1997. Only ICAs (n = 98, in 57 patients) without ipsilateral CCA disease at angiography were analyzed. The range of CCA peak systolic velocities (PSVs) and end diastolic velocities (EDVs) and velocity ratios were calculated for each CCA measurement. For each ICA/CCA velocity ratio, receiver operating characteristic analysis was performed. RESULTS: CCA PSV and EDV ranges averaged 23.1 cm/sec +/- 15.7 (SD) and 5.1 cm/sec +/- 3.6, respectively. For a given side, the difference averaged 1.0 +/- 1.3 for PSV ratios and 2.7 +/- 6.9 for EDV ratios, depending on where CCA measurements were taken. By using a threshold of 60% stenosis as indication for endarterectomy, variability in CCA velocities could have altered recommendations in 16 (28%) of 57 patients. Receiver operating characteristic analysis showed that ratios made by using the three CCA velocities or their mean were not significantly different. CONCLUSION: Variability in velocity measurements along the course of the CCA in patients with ICA disease can be substantial and can result in inaccuracies in assessment of carotid stenosis.     

Assessment of carotid stenosis using three-dimensional T2-weighted dark blood imaging: Initial experience

Purpose:

To evaluate the use of a T2‐weighted SPACE sequence (T2w‐SPACE) to assess carotid stenosis via several methods and compare its performance with contrast‐enhanced magnetic resonance angiography (ceMRA).

Materials and Methods:

Fifteen patients with carotid atherosclerosis underwent dark blood (DB)‐MRI using a 3D turbo spin echo with variable flip angles sequence (T2w‐SPACE) and ceMRA. Images were coregistered and evaluated by two observers. Comparisons were made for luminal diameter, luminal area, degree of luminal stenosis (NASCET: North American Symptomatic Endarterectomy Trial; ECST: European Carotid Surgery Trial, and area stenosis), and vessel wall area. Degree of NASCET stenosis was clinically classified as mild (<50%), moderate (50%–69%), or severe (>69%).

Results:

Excellent agreement was seen between ceMRA and T2w‐SPACE and between observers for assessment of lumen diameter, lumen area, vessel wall area, and degree of NASCET stenosis (r > 0.80, P < 0.001). ECST stenosis was consistently higher than NASCET stenosis (48 ± 14% vs. 24 ± 22%, P < 0.001). Area stenosis (72 ± 2%) was significantly higher (P < 0.001) than both ESCT and NASCET stenosis.

Conclusion:

DB‐MRI of carotid arteries using T2w‐SPACE is clinically feasible. It provides accurate measurements of lumen size and degree of stenosis in comparison with ceMRA and offers a more reproducible measure of ECST stenosis than ceMRA. J. Magn. Reson. Imaging 2012;449‐455. © 2011 Wiley Periodicals, Inc.     

Carotid artery stenosis: gray-scale and Doppler US diagnosis--Society of Radiologists in Ultrasound Consensus Conference

The Society of Radiologists in Ultrasound convened a multidisciplinary panel of experts in the field of vascular ultrasonography (US) to come to a consensus regarding Doppler US for assistance in the diagnosis of carotid artery stenosis. The panel's consensus statement is believed to represent a reasonable position on the basis of analysis of available literature and panelists' experience. Key elements of the statement include the following: (a) All internal carotid artery (ICA) examinations should be performed with gray-scale, color Doppler, and spectral Doppler US. (b) The degree of stenosis determined at gray-scale and Doppler US should be stratified into the categories of normal (no stenosis), <50% stenosis, 50%-69% stenosis, > or =70% stenosis to near occlusion, near occlusion, and total occlusion. (c) ICA peak systolic velocity (PSV) and presence of plaque on gray-scale and/or color Doppler images are primarily used in diagnosis and grading of ICA stenosis; two additional parameters, ICA-to-common carotid artery PSV ratio and ICA end-diastolic velocity may also be used when clinical or technical factors raise concern that ICA PSV may not be representative of the extent of disease. (d) ICA should be diagnosed as (i) normal when ICA PSV is less than 125 cm/sec and no plaque or intimal thickening is visible; (ii) <50% stenosis when ICA PSV is less than 125 cm/sec and plaque or intimal thickening is visible; (iii) 50%-69% stenosis when ICA PSV is 125-230 cm/sec and plaque is visible; (iv) > or =70% stenosis to near occlusion when ICA PSV is greater than 230 cm/sec and visible plaque and lumen narrowing are seen; (v) near occlusion when there is a markedly narrowed lumen at color Doppler US; and (vi) total occlusion when there is no detectable patent lumen at gray-scale US and no flow at spectral, power, and color Doppler US. (e) The final report should discuss velocity measurements and gray-scale and color Doppler findings. Study limitations should be noted when they exist. The conclusion should state an estimated degree of ICA stenosis as reflected in the above categories. The panel also considered various technical aspects of carotid US and methods for quality assessment and identified several important unanswered questions meriting future research.     

Sonographic NASCET index: a new doppler parameter for assessment of internal carotid artery stenosis

BACKGROUND AND PURPOSE: Established Doppler parameters for carotid stenosis assessment do not reflect North American Symptomatic Carotid Endarterectomy Trial (NASCET)-style methodology. We derived a Doppler parameter, termed sonographic NASCET index (SNI), and hypothesized that the SNI would provide greater angiographic correlation and better accuracy in predicting stenosis of 70% or greater than that of currently used peak systolic velocity (PSV) measurements. METHODS: Inclusion criteria of angiographically proved carotid stenoses of 40-95% and measured proximal and distal internal carotid artery Doppler PSV values were established. Occlusions and near occlusions were specifically excluded. Doppler and angiographic data meeting the inclusion criteria from 32 carotid bifurcations were identified; actual angiographic stenoses ranged 40-89%. SNI values were calculated for each vessel. PSV and SNI were correlated with angiography by using linear regression analysis. Accuracies of SNI and PSV in predicting stenosis of 70% or greater were compared at two thresholds. RESULTS: Correlation between SNI and angiography was superior to that between PSV and angiography (r2=0.64 vs 0.38). PSV and SNI values that corresponded to 70% angiographic stenosis were 345 cm/s and 45.5, respectively. Accuracy of PSV of 345 cm/s or greater in predicting stenosis of 70% or greater was 78%, compared with 88% for SNI of 45.5 or greater. The SNI value that corresponded to a PSV threshold of 250 cm/s was 33. Accuracy of PSV of 250 cm/s or greater in predicting stenosis of 70% or greater was 81%, compared with 88% for SNI of 33 or greater. CONCLUSION: Correlation between SNI and angiography was greater than that between PSV and angiography. Accuracy of SNI in predicting stenosis of 70% or greater was also superior to that of PSV at two thresholds. These results suggest that SNI may be a better predictor of high-grade carotid stenosis than is PSV.     

Stellenwert der Doppler-sonographischen Verfahren zur Diagnose der Karotisstenosen

Determining degree and morphology of stenoses is important for surgical planning or stent implantation. Vascular ultrasound is usually the first modality to evaluate carotid artery stenosis. Due to rapid development various methods of vascular ultrasound are applied including continuous wave (CW) Doppler, duplex Doppler, colour-coded duplex sonography (CCDS), power Doppler and B-flow technique. For quantitative assessment of the degree of stenosis the most frequently used parameters are peak systolic velocity (PSV), end-diastolic velocity (EDV) in the internal carotid artery (ICA), as well as ICA to CCA ratios of PSV and EDV. Different results reported in the literature may reflect differences in defining the degree of stenosis and methodological differences in protocol or imaging techniques.Differences in defining the degree of stenosis, advantages and disadvantages of the different Doppler techniques and future developments are discussed in detail.     

How should we estimate carotid stenosis using magnetic resonance angiography?

Our purpose was to assess the reproducibility of and differences between the most commonly used methods for assessing carotid artery stenosis using magnetic resonance angiography (MRA). We studied 55 patients who underwent axial three-dimensional time-of-flight MRA (1.5 T). Quantitative caliper measurements were performed from maximum intensity projection (MIP) and multiple planar reconstruction (MPR) images, according to the criteria of the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and European Carotid Surgery Trial (ECST). The measurements were compared to each other and to visual interpretation, using conventional angiography as the reference. The measured percentage stenoses were higher on MRA than on digital subtraction angiography (DSA) using both NASCET (mean difference 1.9–3.0%) and ECST (6.3–6.7%) criteria. The kappa coefficients for the agreement between DSA and MRA were higher using the NAS-CET (0.61–0.76) than the ECST criteria (0.52–0.65). No statistically significant differences were found between measurements from MIP and MPR images. The ECST measurement criteria gave significantly higher percentage stenoses than the NASCET criteria (P<0.001), this difference being more prominent on MRA (mean difference in diameter stenosis percentage 14.3–16.4%) than on DSA (7.6–11.2%) and most important with mild stenoses. The difference between visual interpretation and quantitative measurements on MRA was significant (P=0.01–0.001). There were no statistically significant interobserver differences in the MRA film readings, either in visually estimated degrees of stenosis or stenosis measurements. Thus, the different criteria of the two multicentre trials led to significantly different results, especially in the assessment of mild stenosis, and these differences are more important with MRA than with aging modalities or the reconstruction programs seem less important.     

Doppler sonographic parameters for detection of carotid stenosis: is there an optimum method for their selection?

OBJECTIVE: A wide range of Doppler threshold values for carotid stenosis is found in the literature. We undertook this study to compare methods of derivation and to determine if an optimum strategy of threshold selection exists for a high-risk population. MATERIALS AND METHODS: From the sonograms of all patent internal carotid arteries, peak systolic velocity in the internal carotid artery (ICA(PSV)) and the ratio of peak systolic velocity in the internal carotid artery to that of the common carotid artery (ICA(PSV)/ CCA(PSV)) were compared with the percentage of angiographically determined stenosis. Receiver operating characteristic curves were generated for levels of stenosis > or =60% and > or =70%. Doppler thresholds were chosen on the basis of maximum accuracy and on the basis of > or =90% sensitivity and specificity. Patients were then segregated into symptomatic and asymptomatic cohorts, and the above process was repeated. An effectiveness analysis was also conducted using various Doppler thresholds. Thresholds derived using these three methods were compared and optimal values chosen. RESULTS. Of 333 carotid arteries that fit inclusion criteria, 132 were found in asymptomatic patients and 201 in symptomatic patients. Maximum accuracy, > or =90% sensitivity and specificity, and effectiveness analysis each produced different ranges of thresholds. We chose final thresholds that maintained patient outcome profiles. For asymptomatic patients at the > or =60% stenosis level, thresholds were ICA(PSV) = 200 cm/sec and ICA(PSV)/CCA(PSV) = 3.0. For symptomatic patients with stenosis > or =70%, thresholds were ICA(PSV) = 175 cm/sec and ICA(PSV)/CCA(PSV) = 2.5. CONCLUSION: Considerable latitude exists in the choice of carotid Doppler thresholds. We propose a rational strategy for threshold selection based on a combination of three commonly used methods. Our observations indicate that it appears advisable to consider symptomatic and asymptomatic patients separately and to apply appropriately derived thresholds.     

Comparison of Doppler ultrasound, magnetic resonance angiographic techniques and catheter angiography in evaluation of carotid stenosis

AIM: To compare the accuracy of ultrasound and two magnetic resonance (MR) angiographic techniques with catheter angiography in assessing atherosclerosis at the carotid bifurcation.MATERIALS AND METHODS: Forty patients with symptomatic carotid stenosis were studied by Doppler ultrasound, time-of-flight MR angiography, contrast-enhanced MR angiography and conventional catheter angiography. The degree of stenosis found on ultrasound and MR angiography was compared with the results of catheter angiography. Four different assessment methods were conducted for the MR angiographic data. Kappa, sensitivity and specificity (with confidence intervals) values were calculated for the US and MR angiography results compared to catheter angiography.RESULTS: Catheter angiography showed 12 internal carotid artery occlusions (15%), 34 severe (44%), 12 moderate (15%) and 20 mild stenoses (26%), using NASCET criteria.Ultrasound showed 65% sensitivity and 95% specificity in detecting surgically amenable lesions, whilst the MR angiographic techniques had sensitivities varying from 82-100%, and specificities from 95-100%.A moderate kappa value was calculated for the US data, whilst all MR techniques were found to show very good agreement with catheter angiography.CONCLUSION: This data suggests that MR angiography is more accurate than Doppler ultrasound in defining surgical lesions and has comparable accuracy to catheter angiography. The use of contrast-enhanced MR angiography is useful in certain situations but is not essential in all cases.     

Efficacy of patient selection strategies for carotid endarterectomy by contrast-enhanced MRA on a 1 T machine and duplex ultrasound in a regional hospital

AIM: To investigate whether contrast-enhanced magnetic resonance angiography (CE-MRA) and duplex ultrasound (DUS) could replace digital subtraction angiography (DSA) for diagnosing internal carotid artery (ICA) stenosis in regional centres with less specialized technicians and equipment, such as a 1 Tesla MRI machine. MATERIALS AND METHODS: Sixty-six consecutive, symptomatic patients with ICA stenosis, as evidenced using DSA, were included. In the first 34 patients DUS was validated and cut-off criteria were established. Data were analysed by receiver operating characteristic curve and logistic regression. Two observers analysed the DUS and CE-MRA results of 32 patients. Stenoses were categorized in accordance with North American Symptomatic Endarterectomy Trial (NASCET) measurement criteria. RESULTS: Peak systolic velocity (PSV) in the ICA was defined as a better parameter for defining stenosis than end diastolic velocity and the PSV ICA:common carotid artery ratio. The optimal PSV threshold was 230cm/s. Four ICAs were not interpretable on DUS, and one on CE-MRA. Two patients did not undergo CE-MRA. The sensitivities and specificities were calculated: for DUS these were 100% and 68% respectively; for observer 1 on CE-MRA these were 93% and 89%, respectively; for observer 2 these were 92% and 87%, respectively. The sensitivity and specificity for combined DUS/CE-MRA were 100% and 85%, respectively. Seventy-eight percent of CE-MRA and DUS correlated. The weighted Kappa for CE-MRA and DSA were 0.8 and 0.9, respectively. CONCLUSION: DUS and CE-MRA are effective non-invasive methods for selecting patients with ICA stenosis for carotid endarterectomy in non-specialized centres using a 1T machine. The present results suggest that no referrals to more specialized centres for non-invasive diagnostic work-up for carotid artery stenoses will be necessary.     

Effect of an internal carotid stenosis on orbital blood velocity.

PURPOSE: To examine how an internal carotid artery (ICA) stenosis influences the orbital blood velocity and to determine which velocity parameters are most useful. MATERIAL AND METHODS: The study group comprised 94 randomly selected patients examined with orbital US; most of the patients had a carotid artery stenosis. There were 58 men and 36 women, ranging in age from 22 to 88 years with a mean age of 63.1 years. The ICA stenosis grade was determined with carotid US. Peak systolic (Vp) and end-diastolic blood velocities, systolic acceleration, mean velocity, pulsatile index (PI) and resistance index (RI) were measured within the central retinal artery (CRA) and the ophthalmic artery (OA), and peak velocity was measured within the central retinal vein (CRV). The area under the ROC curve was used to compare the outcome of diagnostic tests. RESULTS: Only a severe (> or =80%) ICA stenosis decreased orbital blood velocity significantly, while milder stenoses did not cause significant flow decrease or side differences. According to ROC curve analysis, the threshold values giving the highest accuracy in detecting a > or =80% ICA stenosis were Vp < or =0.08 cm/s for the CRA and Vp < or =0.14 cm/s for the OA. The sensitivities for detecting a > or =80% ICA stenosis were 45% for Vp CRA and 60% for Vp OA. Systolic acceleration also decreased in severe stenoses, but RI, PI and velocity in the CRV did not correlate with ICA pathology. Reversal of OA flow was seen in 92% of ICA occlusion and in 47% of severe ICA stenosis. CONCLUSION: Orbital Doppler combined with carotid Doppler can be helpful in the diagnosis of the ocular ischaemic syndrome and in the evaluation of whether the symptoms are related to occlusion of the ophthalmic or central retinal vessels or are a consequence of carotid artery stenosis.     

The inter-sonographer reliability of carotid duplex ultrasound

Carotid duplex ultrasound (CDUS) is a non-invasive technique used to assess the severity of carotid artery stenosis. It has been shown to have good correlation with digital subtraction angiography (DSA) but has been criticised for its variability. One source of this is the variation in results between studies responsible for re-validating velocity criteria to match the established treatment thresholds of internal carotid artery (ICA) stenosis. The aim of this study was to develop velocity criteria and determine the presence of inter-sonographer variation of CDUS when grading ICA stenosis in our department. Five sonographers measured the degree of ICA stenosis with CDUS in 33 patients who also underwent DSA. Receiver operator characteristic curve analysis was used to develop optimal velocity criteria for the 50%, 70% and 90% ICA stenosis thresholds as a group and for each individual sonographer. A peak systolic velocity ratio of > or = 3.25 was shown to have the highest accuracy (91.5%) for predicting a 70% stenosis. A moderate value of kappa (0.53 +/- 0.027) was calculated if the optimum velocity criterion was employed for each sonographer. There was no significant variation between the ability of sonographers to grade ICA stenosis (P > 0.05) and an excellent ICC of 0.911 was calculated. This study provides evidence to suggest that CDUS in our department is not an operator-dependant test for the investigation of ICA stenosis.     

Doppler ultrasound (pre- and post-contrast enhancement) for detection of recurrent stenosis in stented renal arteries: preliminary results

The purpose of the present paper was to assess whether conventional renal Doppler ultrasound and the commonly used parameters of peak systolic velocity and renal aortic ratio may be an appropriate modality for the follow-up of renal artery stents. A total of 19 arteries in 15 patients was examined with both renal Doppler ultrasound and angiography for the presence or absence of recurrent renal artery stenosis. Disease was considered present on angiography if the arterial diameter was more than 60% stenotic. Doppler criteria for stenosis were either a peak systolic velocity of > 180 cm/s or a renal aortic ratio of > 3.0. Echo enhancement with Levovist (Schering, Berlin, Germany) was used if studies were technically unsuccessful or to improve diagnostic confidence. Renal Doppler ultrasound detected 100% of renal artery stenoses. The specificity was 75%, the positive predictive value was 67% and the negative predictive value was 100%. Echo enhancement improved the technical success rate from 89 to 95% and also increased diagnostic confidence in six examinations. The present limited study suggests that similar renal Doppler parameters as used for the study of unstented renal arteries may be applied to the examination of renal arteries with renal stents in situ. It therefore suggests that Doppler ultrasound may provide an adequate non-invasive means of renal artery stent follow-up, particularly when combined with echo-enhancing agents. Further study is warranted to confirm these initial conclusions.     

Combined use of color duplex ultrasonography and B-flow imaging for evaluation of patients with carotid artery stenosis

BACKGROUND AND PURPOSE: Color duplex ultrasonography (CDU) is a standard method of noninvasive evaluation of internal carotid artery stenosis (ICAS). B-flow imaging (BFI), on the other hand, is a newer method. We investigated the accuracy of the two noninvasive tests--CDU and BFI--each separately and as a combination of the two tests by comparing with digital subtraction angiography as a reference standard. METHODS: We performed CDU, BFI, and digital subtraction angiography on 95 consecutive patients with ICAS. Separate and combined test results of CDU and BFI were compared with digital subtraction angiography results. RESULTS: For identifying 70% to 99% ICAS, as CDU criterion, the ratio of internal carotid artery to common carotid artery peak systolic velocity had the highest diagnostic accuracy (sensitivity, 94%; specificity, 96%). The sensitivity and specificity of BFI were 65% and 98%, respectively. With CDU and BFI, results were concordant in 144 (89%) cases for 70% to 99% ICAS. Sensitivity and specificity of combined CDU and BFI results for identification of ICAS were 95% and 99%, respectively. The misclassification rates of CDU and BFI were 4.7% and 8.1%, respectively. When combined test results were concordant, the misclassification rate decreased to 1.4%. CONCLUSION: CDU showed a slightly better accuracy than did BFI in the diagnosis of carotid artery stenosis. Combined use of CDU and BFI is more accurate than use of either test alone.