Power Doppler imaging of carotid artery stenosis. Comparison with color Doppler flow imaging and angiography

Potential Anti-Inflammatory and Anti-Coagulation Effects of One-Time Application of Remote Ischemic Conditioning in Patients With Subacute/Chronic Cerebral Arteriostenosis and Venostenosis

BACKGROUND

Remote ischemic conditioning (RIC) is an extremely simple, non-invasive, and cost-effective method with a neuroprotective effect. This study aimed to evaluate the immediate effects of one-time application of RIC on inflammation and coagulation in patients with chronic cerebral vascular stenosis, and compare the different effects of RIC on cerebral arteriostenosis and cerebral venostenosis.

METHOD

A total of 47 patients with defined cerebral arteriostenosis (n=21) or venostenosis (n=26) were prospectively enrolled. RIC intervention was given once with 5 cycles of inflating and deflating for 5 minutes alternately. Blood was sampled 5 minutes before and after RIC for inflammatory and thrombophilia biomarkers. Differences in inflammatory and thrombotic variables at differing time points in the group were assessed using paired t tests or Wilcoxon matched-pairs signed-rank test.

RESULTS

Patients with cerebral arteriostenosis had a higher level of pre-RIC neutrophil-to-lymphocyte ratio ( P =0.034), high-sensitivity C-reactive protein ( P =0.037), and fibrinogen ( P =0.002) than that with cerebral venostenosis. In the arterial group, levels of fibrinogen ( P =0.023) decreased, and interleukin-6 levels were elevated ( P =0.019) after a single RIC. Age was negatively related to interleukin-6, C-reactive protein, and fibrinogen.

CONCLUSION

One-time RIC interventions may show seemingly coexisted proinflammatory and anti-coagulation effects of a single bout on patients with cerebral arteriostenosis. Older age was a negative predictor for multiple biomarkers in the cerebral arteriostensosis group. The protective effect of RIC on cerebral venostenosis patients needs to be further studied in a larger sample size.

Duplex ultrasound for diagnosing symptomatic carotid stenosis in the extracranial segments

BACKGROUND

Carotid artery stenosis is an important cause of stroke and transient ischemic attack. Correctly and rapidly identifying patients with symptomatic carotid artery stenosis is essential for adequate treatment with early cerebral revascularization. Doubts about the diagnostic value regarding the accuracy of duplex ultrasound (DUS) and the possibility of using DUS as the single diagnostic test before carotid revascularization are still debated.

OBJECTIVES

To estimate the accuracy of DUS in individuals with symptomatic carotid stenosis verified by either digital subtraction angiography (DSA), computed tomography angiography (CTA), or magnetic resonance angiography (MRA).

SEARCH METHODS

We searched CRDTAS, CENTRAL, MEDLINE (Ovid), Embase (Ovid), ISI Web of Science, HTA, DARE, and LILACS up to 15 February 2021. We handsearched the reference lists of all included studies and other relevant publications and contacted experts in the field to identify additional studies or unpublished data.

SELECTION CRITERIA

We included studies assessing DUS accuracy against an acceptable reference standard (DSA, MRA, or CTA) in symptomatic patients. We considered the classification of carotid stenosis with DUS defined with validated duplex velocity criteria, and the NASCET criteria for carotid stenosis measures on DSA, MRA, and CTA. We excluded studies that included < 70% of symptomatic patients; the time between the index test and the reference standard was longer than four weeks or not described, or that presented no objective criteria to estimate carotid stenosis.

DATA COLLECTION AND ANALYSIS

The review authors independently screened articles, extracted data, and assessed the risk of bias and applicability concerns using the QUADAS-2 domain list. We extracted data with an effort to complete a 2 × 2 table (true positives, true negatives, false positives, and false negatives) for each of the different categories of carotid stenosis and reference standards. We produced forest plots and summary receiver operating characteristic (ROC) plots to summarize the data. Where meta-analysis was possible, we used a bivariate meta-analysis model.

MAIN RESULTS

We identified 25,087 unique studies, of which 22 were deemed eligible for inclusion (4957 carotid arteries). The risk of bias varied considerably across the studies, and studies were generally of moderate to low quality. We narratively described the results without meta-analysis in seven studies in which the criteria used to determine stenosis were too different from the duplex velocity criteria proposed in our protocol or studies that provided insufficient data to complete a 2 × 2 table for at least in one category of stenosis. Nine studies (2770 carotid arteries) presented DUS versus DSA results for 70% to 99% carotid artery stenosis, and two (685 carotid arteries) presented results from DUS versus CTA in this category. Seven studies presented results for occlusion with DSA as the reference standard and three with CTA as the reference standard. Five studies compared DUS versus DSA for 50% to 99% carotid artery stenosis. Only one study presented results from 50% to 69% carotid artery stenosis. For DUS versus DSA, for < 50% carotid artery stenosis, the summary sensitivity was 0.63 (95% confidence interval [CI] 0.48 to 0.76) and the summary specificity was 0.99 (95% CI 0.96 to 0.99); for the 50% to 69% range, only one study was included and meta-analysis not performed; for the 50% to 99% range, the summary sensitivity was 0.97 (95% CI 0.95 to 0.98) and the summary specificity was 0.70 (95% CI 0.67 to 0.73); for the 70% to 99% range, the summary sensitivity was 0.85 (95% CI 0.77 to 0.91) and the summary specificity was 0.98 (95% CI 0.74 to 0.90); for occlusion, the summary sensitivity was 0.91 (95% CI 0.81 to 0.97) and the summary specificity was 0.95 (95% CI 0.76 to 0.99). For sensitivity analyses, excluding studies in which participants were selected based on the presence of occlusion on DUS had an impact on specificity: 0.98 (95% CI 0.97 to 0.99). For DUS versus CTA, we found two studies in the range of 70% to 99%; the sensitivity varied from 0.57 to 0.94 and the specificity varied from 0.87 to 0.98. For occlusion, the summary sensitivity was 0.95 (95% CI 0.80 to 0.99) and the summary specificity was 0.91 (95% CI 0.09 to 0.99). For DUS versus MRA, there was one study with results for 50% to 99% carotid artery stenosis, with a sensitivity of 0.88 (95% CI 0.70 to 0.98) and specificity of 0.60 (95% CI 0.15 to 0.95); in the 70% to 99% range, two studies were included, with sensitivity that varied from 0.54 to 0.99 and specificity that varied from 0.78 to 0.89. We could perform only a few of the proposed sensitivity analyses because of the small number of studies included.

AUTHORS' CONCLUSIONS

This review provides evidence that the diagnostic accuracy of DUS is high, especially at discriminating between the presence or absence of significant carotid artery stenosis (< 50% or 50% to 99%). This evidence, plus its less invasive nature, supports the early use of DUS for the detection of carotid artery stenosis. The accuracy for 70% to 99% carotid artery stenosis and occlusion is high. Clinicians should exercise caution when using DUS as the single preoperative diagnostic method, and the limitations should be considered. There was little evidence of the accuracy of DUS when compared with CTA or MRA. The results of this review should be interpreted with caution because they are based on studies of low methodological quality, mainly due to the patient selection method. Methodological problems in participant inclusion criteria from the studies discussed above apparently influenced an overestimated estimate of prevalence values. Most of the studies included failed to precisely describe inclusion criteria and previous testing. Future diagnostic accuracy studies should include direct comparisons of the various modalities of diagnostic tests (mainly DUS, CTA, and MRA) for carotid artery stenosis since DSA is no longer considered to be the best method for diagnosing carotid stenosis and less invasive tests are now used as reference standards in clinical practice. Also, for future studies, the participant inclusion criteria require careful attention.

Measurement of the Internal Carotid Artery Cross-Sectional Area: Systematic Differences Depending on Grayscale, Power Doppler, and Color Doppler Techniques

OBJECTIVES

To determine how measurements of the internal carotid artery (ICA) cross-sectional area will differ systematically when obtained by grayscale, color Doppler, and power Doppler imaging.

METHODS

A total of 451 patients had greater than 40% diameter stenosis in at least a single ICA. Anteroposterior and transverse luminal diameters were measured in 609 arteries on grayscale, color, and power Doppler transverse images of the carotid bulb and proximal and distal ICAs. Cross-sectional areas were calculated and compared by a repeated-measures analysis of variance model to assess for significant differences.

RESULTS

Mean ICA cross-sectional areas ± SDs as measured by grayscale, power Doppler, and color Doppler imaging were 122 ± 81, 122 ± 79, and 125 ± 79 mm² , respectively. The mean ICA area estimated by color Doppler imaging was significantly greater than that estimated by power Doppler imaging (P < .0001) and grayscale imaging (P = .02). Area estimates on grayscale and power Doppler images were not significantly different (P = .99). After accounting for the correlation of repeated measurements within single vessels, color Doppler estimates of the luminal area were on average 3.44 and 9.5 mm² greater than grayscale and power Doppler estimates. Relative cross-sectional area estimates were on average 9.4% greater with color Doppler imaging at smaller luminal diameters (<60 mm² ) compared with larger luminal diameters.

CONCLUSIONS

Measurements of the ICA cross-sectional area by color Doppler imaging were significantly greater than those obtained by power Doppler or grayscale imaging. This difference should be considered when stenosis estimates are confirmed or graded by luminal measurements.

Effect of Ultrasonography in the Assessment of Carotid Artery Stenosis

Although ultrasonography (US) advantageously portrays lumen and wall thickness, velocity criteria have been used primarily to interpret carotid artery stenosis. The relationship of US and velocity measurements was investigated.

Peak-systolic and end-diastolic velocities (PSV, EDV) increase exponentially as the lumen of the internal carotid artery narrows and the percent stenosis (%S) increases. We tested the consistency of the relationship between carotid velocities and US %S in two distinct data sets. One data set was used to obtain regression equations relating velocity parameters and %S based on US. Validation of these equations was conducted using a separate, independent data set. US measurements were classified in 12 %S intervals. PSV, EDV, the ratio of the internal carotid artery to the common carotid artery PSV, and %S were entered consecutively until 10 records for each %S interval were obtained. Regression equations obtained in the first data set were used to predict %S in the second data set. Predicted %S was then compared with actual US %S.

The highest correlation in the first data set ( r = .89) was between %S and the natural logarithm (ln) of PSV. This ln PSV -%S equation was then applied to a second data set of an additional 120 carotid duplex images. In the second data set, actual %S and PSV–predicted %S differed by > 10% in 38 cases (32%). When all velocity-%S regression equations were used for comparison, differences between actual and at least one velocity-predicted %S were > 10% in 19% of the arteries. Conversely, actual %S matched at least one prediction of %S based on velocity data in 81% of the cases.

US %S differed significantly from single velocity-based estimates of %S in at least one-third of the cases. On the other hand, four of five US measurements were confirmed by at least one velocity parameter. Emphasis on US, in addition to velocity data, is recommended for the interpretation of duplex US carotid examinations.

Signal losses with real-time three-dimensional power Doppler imaging

Power Doppler imaging (PDI) has been shown to be influenced by the wall filter when assessing arterial stenoses. Real-time 3-D Doppler imaging may likely become a widespread practice in the near future, but how the wall filter could affect PDI during the cardiac cycle has not been investigated. The objective of the study was to demonstrate that the wall filter may produce unexpected major signal losses in real-time 3-D PDI. To test our hypothesis, we first validated binary images obtained from analytical simulations with in vitro PDI acquisitions performed in a tube under pulsatile flow conditions. We then simulated PDI images in the presence of a severe stenosis, considering physiological conditions by finite element modeling. Power Doppler imaging simulations revealed important signal losses within the lumen area at different instants of the flow cycle, and there was a very good concordance between measured and predicted PDI binary images in the tube. Our results show that the wall filter may induce severe PDI signal losses that could negatively influence the assessment of vascular stenosis. Clinicians should therefore be aware of this cause of signal loss to properly interpret power Doppler angiographic images.

The Spencer's Curve: clinical implications of a classic hemodynamic model

Merrill P Spencer and John M Reid applied the Hagen-Poiseuille law, continuity principle, and cerebrovascular resistance to describe a theoretical model of the relationship between the flow velocity, flow volume, and decreasing size of the residual vessel lumen. The model was plotted in a graph that became widely known as the Spencer's curve. Although derived for a smooth and axis-symmetric arterial stenosis of a short length in a segment with no bifurcations being perfused at stable arterial pressures and viscosity, this model represents a milestone in understanding cerebral hemodynamics with long-lasting practical and research implications. This review summarizes several hemodynamic principles that determine velocity and flow volume changes, explains how the model aids interpretation of cerebrovascular ultrasound studies, and describes its impact on clinical practice and research.

Color Doppler, power Doppler and B-flow ultrasound in the assessment of ICA stenosis: Comparison with 64-MD-CT angiography

The purpose of this study is to investigate the diagnostic potential of color-coded Doppler sonography (CCDS), power-Doppler (PD) and B-flow ultrasound in assessing the degree of extracranial internal carotid artery (ICA) stenosis in comparison to CT-angiography (MD-CTA). Thirty-two consecutive patients referred for CTA with 41 ICA-stenoses were included in this prospective study. MD-CTA was performed using a 64 row scanner with a CTDIvol of 13.1 mGy/cm. In CTA, CCDS, PD and B-flow, the degree of stenosis was evaluated by the minimal intrastenotic diameter in comparison to the poststenotic diameter. Two radiologists performed a quantitative evaluation of the stenoses in consensus blinded to the results of ultrasound. These were correlated to CTA, CCDS, PD and B-flow, intraoperative findings and clinical follow-up. Grading of the stenoses in B-flow ultrasound outperformed the other techniques in terms of accuracy with a correlation coefficient to CTA of 0.88, while PD and CCDS measurements yield coefficients of 0.74 and 0.70. Bland-Altman analysis additionally shows a very little bias of the three US methods between 0.5 and 3.2 %. There is excellent correlation (coefficient 0.88, CI 0.77-0.93) with 64-MD-CTA and B-flow ultrasound in terms of accuracy for intrastenotic and poststenotic diameter. Duplex sonography is useful for screening purposes.

Screening for High-grade Carotid Stenosis Using a Portable Ultrasonography Instrument

BACKGROUND AND PURPOSE

We investigated the diagnostic performance of a brief Power Doppler Imaging (PDI) screening examination for carotid artery stenoses using a newly developed portable instrument.

METHODS

A highly experienced sonographer screened in total 152 carotid arteries by either continuous wave (cw) Doppler (n= 50) or a lightweight (2.4 kg) portable duplex device (n= 102) in a prospective study of 76 high-risk patients. The screening protocols included either spectrum analysis and frequency shift measurement in both internal carotid arteries with cw-Doppler or determination of area and diameter ratios in transverse and longitudinal views of both carotid arteries in B-mode and with PDI, but without velocity measurement. Both protocols were evaluated against a complete routine duplex ultrasonography examination.

RESULTS

According to the complete examination, stenoses were <50% in 73 of 102 (71.6%), 50-75% in 19 of 102 (18.6%), 75-95% in 7 of 102 (6.9%), and occluded in 3 of 102 (2.9%) arteries (PDI cohort), and <50% in 39 of 50 (78%), 50-75% in 8 of 50 (16%), 75-95% in 2 of 50 (4%), and occluded in 1 of 50 (2%) artery (cw-Doppler cohort). Mean screening time was 8.8 +/- 2.5 minute (PDI) and 9.4 +/- 2.6 minute (cw-Doppler). For stenoses >75%, A(z) values (area under the receiver operating characteristics curve) were 0.897 for area ratios, 0.843 for diameter ratios (PDI protocol) and 1.0 for the cw-Doppler protocol.

CONCLUSIONS

The diagnostic performance of the cw-Doppler protocol was superior to the PDI protocol. Nevertheless, both protocols appear suitable as inexpensive screening strategies to identify subjects with >75% stenosis measured by carotid Doppler ultrasound. However, these preliminary data need further verification.

Diagnostics and characterisation of preocclusive stenoses and occlusions of the internal carotid artery with B-flow

The purpose was to evaluate whether B-flow can improve the ultrasonographic diagnosis of preocclusive stenosis and occlusion of the internal carotid artery (ICA) compared with colour-coded Doppler and power Doppler. Ninety patients with occlusions or preocclusive stenoses of the ICA suspected by Doppler sonography were examined with B-flow in comparison with colour-coded Doppler sonography (CCDS), power Doppler (PD) and intra-arterial digital subtraction angiography (DSA). Intrastenotic flow detection and lengths of stenoses were the main criteria. Ulcerated plaques found by surgery in 42/90 patients were compared by ultrasonography (US). Diagnosis of ICA occlusion with CCDS, PD and B-flow was correct in all 42 cases. A preocclusive ICA stenosis in DSA was detected correctly in all 48/48 cases (100%) for B-flow, in 44/48 (92%) for PD and in 39/48 (81%) for CCDS. Surgical findings showed in 17/42 cases ulcerated plaques; 15/17 (89%) of these cases were detected with B-flow, 12/17 (71%) with PD, 10/17 (59%) with CCDS, and 8/17 (47%) with DSA. With B-flow the extent of stenosis was appraised more precisely than with PD and CCDS (P<0.0001). In conclusion, B-flow is a reliable method for preocclusive stenosis of the ICA with less intrastenotic flow artefacts. B-flow facilitates the characterization of plaque morphologies.

Evaluation of cervical lymph node vascularity: a comparison of colour Doppler, power Doppler and 3-D power Doppler sonography

This study was undertaken to compare the performance of colour Doppler (CDS), power Doppler (PDS) and 3-D power Doppler sonography (3-D PDS) in the assessment of vascular pattern and vessel displacement of cervical lymph nodes. Colour Doppler (2-D CDS), power Doppler (2-D PDS) and 3-D power Doppler sonograms (3D PDS) of 145 cervical nodes were reviewed (metastases n=60, lymphoma n=30, tuberculosis n=23, reactive n=25, Kimura disease n=7). Sonograms of the three imaging modes were reviewed separately with an interval of 2 weeks. Lymph nodes were assessed for the vascular pattern (hilar, peripheral or mixed) and the presence or absence of displacement of hilar vascularity. For the assessment of displacement of hilar vascularity, only lymph nodes that showed hilar or mixed vascularity in the three imaging modes were included in the analysis. Results showed that there was a high level of agreement between CDS and PDS in assessment of vascular patterns (kappa=0.914), whereas the level of agreement between CDS and 3-D PDS (kappa=0.484) and between PDS and 3-D PDS (kappa=0.452) was low. There was a high level of agreement in the assessment of displacement of hilar vascularity among the three imaging modes (CDS and PDS, kappa=0.942; CDS and 3-D PDS, kappa=0.808; PDS and 3-D PDS, kappa=0.865). In the assessment of vascular patterns of cervical lymphadenopathy, CDS and PDS have a similar performance. However, accurate assessment of the vascular pattern of cervical nodes may be difficult using 3-D PDS. In the assessment of displacement of hilar vascularity, the performances of CDS, PDS and 3-D PDS are similar.

Comparison of ultrasonography, CT angiography, and digital subtraction angiography in severe carotid stenoses

Digital subtraction angiography (DSA) is considered to be the 'gold standard' for confirmation of severe (70-99%) stenoses of internal carotid arteries (ICAs). However, it is associated with a risk of complications. The aim of this study was to assess the accuracy of ultrasonography (US), computed tomographic angiography (CTA), and their combined use for the detection and quantification of severe carotid stenoses, when compared with DSA. Severe ICA stenoses were diagnosed by US in a set of 29 patients. All patients also underwent CTA and DSA. Sensitivity, specificity, positive (PPV), negative predictive values (NPV), and Pearson's correlation coefficient were used in the evaluation of the percentage of stenosis results. Homogeneity chi2 test was applied when assessing statistical significance. Severe stenosis was diagnosed in 34 ICAs. Two ICAs with uninterpretable CTA finding were excluded. The number of ICAs with stenoses 70-99%/<70%- US 32/0; CTA 29/3; US + CTA 29/3; DSA 24/8. Pearson's correlation coefficient - US 0.601; CTA 0.725; US + CTA 0.773. Sensitivity/specificity/PPV/NPV - US 1.0/0.75/0.75/xxx; CTA 1.0/0.844/0.828/1.0; US + CTA 1.0/0.844/0.828/1.0. Homogeneity chi2 test results - US, P = 0.002; CTA, P = 0.098; US + CTAG, P = 0.098. US in combination with CTA can be used for relatively secure diagnostics of severe ICA stenoses. Thus, invasive DSA can be avoided in a substantial number of patients.

A comparison of Power Doppler with conventional sonographic imaging for the evaluation of renal artery stenosis

Background

Power Doppler (PD) has improved diagnostic capabilities of vascular sonography, mainly because it is independent from the angle of insonation. We evaluated this technique in a prospective comparison with conventional imaging, consisting in Duplex and Color Doppler, for the evaluation of Renal Artery (RA) stenosis.

Methods

Sensitivity, specificity and predictive values of PD and conventional imaging were assessed in a blinded fashion on eighteen patients, 9 with angiographic evidence of unilateral RA stenosis (hypertensive patients) and 9 with angiographically normal arteries (control group). PD images were interpreted with an angiography-like criteria.

Results

In the control group both techniques allowed correct visualization of 16 out of the 18 normal arteries (93% specificity). Only in five hypertensive patients RA stenosis was correctly identified with conventional technique (56% sensitivity and 86% negative predictive value); PD was successful in all hypertensive patients (100% sensitivity and negative predictive value), since the operators could obtain in each case of RA stenosis a sharp color signal of the whole vessel with a clear "minus" at the point of narrowing of the lumen. All results were statistically significant (p < 0.01).

Conclusions

This study demonstrates that PD is superior to conventional imaging, in terms of sensitivity and specificity, for the diagnosis of RA stenosis, because it allows a clear visualization of the whole stenotic vascular lumen. Especially if it is used in concert with the other sonographic techniques, PD can enable a more accurate imaging of renovascular disease with results that seem comparable to selective angiography.

Evaluation of blood flow in carotid artery stenosis using B-flow sonography

B-flow ultrasonography can directly visualize blood streams by reflecting the intravascular red blood cells, and so can detect turbulent flow in vessels. B-flow sonography was used to evaluate flow abnormalities in patients with cervical carotid artery stenosis, and to investigate the mechanism of large embolus formation that may cause distal arterial occlusion. Twenty-two patients with > or = 60% stenosis of the cervical carotid artery excluding cardiovascular embolism were examined by B-flow and color Doppler sonography. Two patients had distal embolism as revealed by digital subtraction angiography, 16 patients had lacunar infarction, and four patients had transient ischemic attacks. B-flow sonography demonstrated reverse flow at the poststenotic site in patients with > or = 70% stenosis. Increased echogenicity at the site of the stenosis was seen in patients with at least 80% stenosis. Prestenotic reverse flow was seen in nine patients with > or = 85% stenosis. The two patients with distal embolism had decreased echogenicity and flow velocity, and diastolic flow was absent. B-flow sonography could detect various turbulent flow patterns and changes in echogenicity associated with cervical carotid artery stenosis. Prestenotic reverse flow and decreased flow velocity may be potential causes of distal embolism. B-flow sonography is a useful method for the evaluation of flow abnormality in patients with carotid artery stenosis.

US of neurovascular occlusive disease: interpretive pearls and pitfalls

Ultrasonography (US) of the head and neck is a convenient but operator-dependent screening tool for detection and diagnosis of neurovascular occlusive disease. In US examination of the extracranial carotid arteries, stenosis is most commonly graded according to the peak systolic Doppler velocity in the region of maximal luminal narrowing rather than according to the percentage of atheromatous plaque occupying the lumen. However, the peak systolic velocity is not always reliable in estimation of the degree of stenosis. General diagnostic pitfalls include technical difficulties with scanning, failure to review the spectral waveform patterns, the presence of additional stenotic lesions, and anatomic variants. Specific examples of pitfalls include tandem lesions, differentiation of pseudo-occlusion from true total occlusion, pseudonormalization of velocities in cases of very severe stenosis, lesions of the carotid artery origin or aortic valve, progression of subclavian steal, underestimation of severe stenosis due to heavily calcified plaque, a persistent trigeminal artery, and contralateral carotid artery stenosis. Although conventional angiography remains the standard of reference for assessment of carotid artery disease, recognition of these common sources of error in US can improve the accuracy of this noninvasive test in diagnosis of carotid artery occlusion.

Comparison of color-flow Doppler scanning, power Doppler scanning, and frequency shift for assessment of carotid artery stenosis

OBJECTIVE

We investigated the accuracy of color-flow Doppler (CD) scanning, power Doppler (PD) scanning, and peak systolic Doppler frequency shift (PSF) in assessment of carotid artery stenosis with angiography used as gold standard, including the measurement techniques used in the North American Symptomatic Carotid Surgery Trial (NASCET) and the European Carotid Surgery Trial (ECST).

METHODS

Fifty-eight consecutive patients diagnosed for carotid artery surgery underwent color-coded duplex sonography and angiography. The duplex examination included the assessment of PSF and the videotaping of sagittal images in CD and PD mode from the proximal common carotid artery to the distal internal carotid artery. Two experienced examiners performed the studies, but once one examiner had done the taping, the other examiner was allowed only to review the tape. Separately, each examiner reviewed the tapes and determined by cursor settings each stenosis according to NASCET and ECST. For interobserver agreement kappa statistic was used. To compare with angiography (degree of stenosis 40%, 50%, 60%, 70%, and 80%) sensitivity, specificity, positive and negative predictive values, and overall accuracy were calculated. PSF cut-off frequencies were based on receiver operator curve analysis.

RESULTS

Because interobserver agreement in CD and PD was good (chance-corrected kappa > 0.6), further analysis used the between-observer mean value for each stenosis. With the NASCET measurement technique, accuracy of Doppler techniques to distinguish a 50% stenosis was 89% for PSF, 91% for CD, and 93% for PD; for a 70% stenosis it was 83% for PSF, 84% for CD, and 81% for PD. With the ECST measurement technique, accuracy to distinguish a 70% stenosis was 86% for PSF, 88% for CD, and 86% for PD; for an 80% stenosis it was 87% for PSF, 87% for CD, and 77% for PD.

CONCLUSION

CD and PD carotid artery stenosis measurements are highly reproducible, and in our hands provided accuracy equal to PSF.

Non-invasive assessment of arterial distension waveforms using gradient-based hough transform and power Doppler ultrasound imaging

The peripheral arterial vessel often appears as an elliptic shape under the constraints of the surrounding tissues. In this study, the gradient-based Hough transform was used to detect the central location of the ellipse and the lumen area of the arterial vessel non-invasively using power Doppler imaging. Sequential ultrasound images were used to construct arterial distension waveforms in both the major- and minor-axis directions for a few cardiac cycles. The common carotid arteries (CCAs) for nine healthy male volunteers (mean age 24 years), in the sitting position, were investigated in vivo. The CCAs (n = 9) had a mean diameter of 5.83mm, and the pulsatile diameter distension was 13.7+/-1.9%. The brachial artery and dorsalis pedis artery for five healthy male volunteers (mean age 26 years), in the supine position, had mean diameters of 4.03mm and 2.83mm and distensions of 16.7+/-4.6% and 15.5+/-5.4%, respectively. The movement of the arterial centre location during the cardiac cycle reflected the asymmetry of the reaction forces produced by the surrounding soft tissues. The present method can obtain the response of vessel distension to pulse pressure, as well as the constrained conditions of the arteries.

Grading of Internal Carotid Artery Stenosis: Validation of Doppler/Duplex Ultrasound Criteria and Angiography Against Endarterectomy Specimen

OBJECTIVES

duplex ultrasound has replaced angiography prior to carotid endarterectomy (CEA) in many institutions. However, the indications for CEA are based on angiographically controlled studies and widely accepted ultrasound criteria do not exist. Consequently, the reliability of Doppler and/or duplex ultrasound to predict a high-grade ICA stenosis has to be proven.

DESIGN

prospective validation study.

MATERIALS

one hundred and fifty carotid bifurcations assessed by ultrasound and selective angiography and 68 acrylat outcasts of carotid specimen after eversion CEA.

METHODS

ICA stenosis was measured angiographically according to the ECST criteria. Combined Doppler acoustic standard criteria (CDASC), peak systolic frequency (PSF), peak systolic velocity (PSV) and end-diastolic velocity (EDV) served as criteria for the ultrasound assessment. These criteria and the results of angiography were compared to the degree of ICA stenosis determined by specimen measurements.

RESULTS

the median degree of ICA stenosis as assessed by angiography (82%, range 56-97%) and CDASC (83%, range 50-99%) corresponded well to the specimen measurements (80%, range 50-95%). The sensitivity of angiography and CDASC to predict a 70-90% ICA stenosis (ECST criteria) compared to the specimen measurements was 88% and 95%, respectively. The positive predictive value (PPV) reached 92% and 96%, respectively. CDASC were equivalent to angiography and were superior to the best single frequency or velocity parameters. If CDASC do not indicate a >/=70% ICA stenosis in spite of a PSV >/=180 cm/s and/or an EDV >/=50 cm/s, angiography may detect patients with a >70% ICA stenosis.

CONCLUSIONS

CDASC are valid in the quantification of high-grade ICA stenosis. They are more reliable than single velocity and/or frequency measurements. However, if velocity criteria and CDASC do not agree, angiography should be performed.

Variability in measurement of internal carotid artery stenosis by arch angiography and duplex ultrasonography--time for a reappraisal?

OBJECTIVES

to determine the inter- and intra-observer variability of ICA stenosis measurement using duplex, ECST and NASCET methods.

DESIGN

a retrospective review of arch angiograms and carotid duplex scans in 50 patients.

MATERIALS AND METHODS

carotid stenoses were calculated by three independent observers according to NASCET and ECST methods. Variation between observers for NASCET and ECST was determined. For each observer, the variation between NASCET and ECST was determined. The variation between duplex and both NASCET and ECST was determined.

RESULTS

inter-observer agreement on the degree of ICA stenosis was clinically and statistically good for NASCET but was poorer for ECST. For each observer, comparison between NASCET and ECST showed 95% limits of agreement of around 50 percentage points. Comparison of duplex with NASCET and ECST showed similar 95% limits of agreement.

CONCLUSIONS

arch angiography allows reproducible measurement of carotid stenosis by the NASCET method between different observers. For the ECST method, reproducibility is not so good. Variations in results between NASCET and ECST and between angiography and duplex are significant. In view of the similar results of the NASCET and ECST trials, this suggests that degree of stenosis may only be a surrogate marker for outcome following carotid endarterectomy.

New duplex ultrasound scan criteria for managing symptomatic 50% or greater carotid stenosis

PURPOSE

The North American Symptomatic Carotid Endarterectomy Trial (NASCET) showed that selected patients benefited from surgery when their carotid artery was 50% or more stenosed. This study assessed the accuracy of color-flow duplex ultrasound scanning (DUS) parameters to detect 50% or greater carotid artery stenosis and to determine the situations in which carotid endarterectomy (CEA) without angiography could be justified.

METHODS

From March 1, 1995, to December 1, 1995, all patients considered for CEA were studied with DUS and carotid angiography. Results of the two tests were blindly compared. DUS measurements of internal carotid artery (ICA) peak systolic velocity (PSV), end diastolic velocity, and ratio of the ICA to common carotid artery PSV (ICA/CCA) were subjected to receiver operator characteristic curve analysis to determine the most accurate criterion predicting 50% or greater angiographic stenosis. The criterion for identifying patients for CEA without angiography was selected from criteria with a high positive predictive value (PPV) and sensitivity.

RESULTS

A total of 188 carotid bifurcations were available for comparison. A PSV (ICA/CCA) of 2 or higher was the most accurate criterion for detection of 50% or greater stenosis, with an accuracy rate of 93% (sensitivity, 96%; specificity, 89%; PPV, 92%). A PSV (ICA/CCA) of 3.6 or higher was the best criterion for identifying candidates for CEA who had not undergone earlier angiography, with PPV, sensitivity, specificity, and accuracy rates of 98%, 77%, 98%, and 86%, respectively.

CONCLUSION

These redefined criteria detect the NASCET-defined threshold level of 50% or greater ICA stenosis, above which CEA results in stroke reduction. A management algorithm based on these criteria should help to minimize both angiography and unnecessary intervention.

Cerebrovascular ultrasound

Rapid progress in noninvasive ultrasound techniques has resulted in a wide variety of clinical applications for assessment of both extracranial and intracranial arterial diseases. Recent highlights in cerebrovascular ultrasound research include imaging methods for characterization of intracranial aneurysms, use of echocontrast agents for improved evaluation of acute stroke patients and transient response harmonic imaging for depiction of brain perfusion. The important role of transcranial Doppler microembolism detection in carotid endarterectomy has been defined, new approaches to noninvasive Doppler measurement of intracranial pressure are progressing, and the clinical indications for transcranial Doppler monitoring of intracranial vasospasm to prevent secondary stroke have expanded. New functional transcranial Doppler applications, which are complementary to positron emission tomography and functional magnetic resonance imaging studies, are evolving for evaluation of functional recovery after stroke; investigation of perfusion asymmetries during complex spatial tasks; assessment of hemispheric dominance in surgical candidates for epilepsy surgery; and elucidation of temporal patterns of regional neuronal activity. With increasing sophistication of cerebrovascular ultrasound methodology, it is essential that standards for data acquisition and interpretation be established. Three recent consensus meetings have provided detailed recommendations on quantification of carotid artery stenosis, on characterization of carotid artery plaques and on microembolism detection by transcranial Doppler.