Magnetic resonance angiography, digital subtraction angiography and Doppler ultrasonography in detection of carotid artery stenosis: a comparison with findings from histological specimens

Background

Patients' life expectancy, clinical symptomatology and the extent of carotid stenosis are the most important factors when deciding whether to perform carotid endarterectomy (CEA) in patients with carotid stenosis. Therefore, the accuracy of measuring carotid stenosis is of utmost importance.

Methods

Patients with internal carotid artery (ICA) stenosis were investigated by digital subtraction angiography (DSA), Doppler ultrasonography (DUS) and magnetic resonance angiography (MRA). Atherosclerotic plaque specimens were transversally cut into smaller segments and histologically processed. The slides were scanned and specimens showing maximal stenosis were determined; the minimal diameter and the diameter of the whole plaque were measured. DSA, DUS and MRA measurements were obtained in 103 patients. A comparison between preoperative and histological findings was performed. In addition, correlation coefficients were computed and tested.

Results

Results show a significant correlation for each of the diagnostic procedures. Mean differences in the whole cohort between preoperative measurements and the histological measurements are as follows: angiographic measurement of carotid stenosis underestimated histological measurement by 14.5% and MRA by 0.7%, but DUS overestimated by 6.6%. The results in severe stenosis (≥70%) are as follows: angiographic measurement underestimated the histological measurements by 2.3%, but MRA overestimated by 12.1% and DUS by 11.3%. The results in moderate stenosis (50–69%): angiographic measurement underestimated the histological measurements by 12.3%, but MRA overestimated by 0.2% and DUS by 7.2%. The results in mild stenosis (30–49%): angiographic measurement underestimated the histological measurements by 24.7% and MRA by 7.6%, but DUS overestimated by 3.3%.

Conclusions

Our study confirms that DSA underestimates moderate and mild ICA stenosis. DUS slightly overestimated moderate ICA stenosis and highly overestimated high-grade ICA stenosis. MRA proved to be accurate in detecting moderate ICA stenosis, but slightly underestimated mild stenosis and overestimated high-grade stenosis. The surgeon should be aware of these discrepancies when deciding whether to perform CEA in patients with ICA stenosis.     

Reappraisal of velocity criteria for carotid bulb/internal carotid artery stenosis utilizing high-resolution B-mode ultrasound validated with computed tomography angiography

OBJECTIVE: Reliability of the most commonly used duplex ultrasound (DUS) velocity thresholds for internal carotid artery (ICA) stenosis has been questioned since these thresholds were developed using less precise methods to grade stenosis severity based on angiography. In this study, maximum percent diameter carotid bulb ICA stenosis (European Carotid Surgery Trial [ECST] method) was objectively measured using high resolution B-mode DUS validated with computed tomography angiography (CTA) and used to determine optimum velocity thresholds for > or =50% and > or =80% bulb internal carotid artery stenosis (ICA). METHODS: B-mode DUS and CTA images of 74 bulb ICA stenoses were compared to validate accuracy of the DUS measurements. In 337 mild, moderate, and severe bulb ICA stenoses (n = 232 patients), the minimal residual lumen and the maximum outer bulb/proximal ICA diameter were determined on longitudinal and transverse images. This in contrast to the North American Symptomatic Carotid Endarterectomy Trial (NASCET) method using normal distal ICA lumen diameter as the denominator. Severe calcified carotid segments and patients with contralateral occlusion were excluded. In each study, the highest peak systolic (PSV) and end-diastolic (EDV) velocities as well as ICA/common carotid artery (CCA) ratio were recorded. Using receiver operating characteristic (ROC) analysis, the optimum threshold for each hemodynamic parameter was determined to predict > or =50% (n = 281) and > or =80% (n = 62) bulb ICA stenosis. RESULTS: Patients mean age was 74 +/- 8 years; 49% females. Clinical risk factors for atherosclerosis included coronary artery disease (40%), diabetes mellitus (32%), hypertension (70%), smoking (34%), and hypercholesterolemia (49%). Thirty-three percent of carotid lesions (n = 110) presented with ischemic cerebrovascular symptoms and 67% (n = 227) were asymptomatic. There was an excellent agreement between B-mode DUS and CTA (r = 0.9, P = .002). The inter/intraobserver agreement (kappa) for B-mode imaging measurements were 0.8 and 0.9, respectively, and for CTA measurements 0.8 and 0.9, respectively. When both PSV of > or =155 cm/s and ICA/CCA ratio of > or =2 were combined for the detection of > or =50% bulb ICA stenosis, a positive predictive value (PPV) of 97% and an accuracy of 82% were obtained. For a > or =80% bulb ICA stenosis, an EDV of > or =140 cm/s, a PSV of > or =370 cm/s and an ICA/CCA ratio of > or =6 had acceptable probability values. CONCLUSION: Compared with established velocity thresholds commonly applied in practice, a substantially higher PSV (155 vs 125 cm/s) was more accurate for detecting > or =50% bulb/ICA stenosis. In combination, a PSV of > or =155 cm/s and an ICA/CCA ratio of > or =2 have excellent predictive value for this stenosis category. For > or =80% bulb ICA stenosis (NASCET 60% stenosis), an EDV of 140 cm/s, a PSV of > or =370 cm/s, and an ICA/CCA ratio of > or =6 are equally reliable and do not indicate any major change from the established criteria. Current DUS > or =50% bulb ICA stenosis criteria appear to overestimate carotid bifurcation disease and may predispose patients with asymptomatic carotid disease to untoward costly diagnostic imaging and intervention.     

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.     

Assessment of carotid artery stenosis by ultrasonography,conventional angiography,and magnetic resonance angiography: Correlation with ex vivo measurement of plaque stenosis

Purpose: Several studies have investigated the correlation between Doppler ultrasonography (DUS), angiography (CA), and magnetic resonance angiography (MRA) in the evaluation of stenosis of the carotid bifurcation. However, these studies suffer from the lack of a true control—the lesion itself—and therefore conclusions about the diagnostic accuracy of each method remain relative. To determine the absolute accuracy of these modalities, we have prospectively studied lesion size with DUS, MRA, and CA in 28 patients undergoing 31 elective carotid endarterectomies and compared the percent of carotid stenosis determined by each technique to the carotid atheroma resected en bloc.Methods: All patients were evaluated by each modality within 1 month before the thromboendarterectomy. With DUS, stenosis size was determined by standard flow criteria. For angiography and MRA, stenosis was defined as residual lumenal diameter/estimated normal arterial diameter (European Carotid Surgery Trial criteria). At surgery the carotid atheroma was removed en bloc in all patients. Patients in whom the lesion could not be removed successfully without damage were excluded from the study. Stenosis of the atheroma was determined ex vivo with high-resolution (0.03 mm³) magnetic resonance and confirmed by acrylic injection of the specimen under pressure and measurement of the atheroma wall and lumen.Results: The measurements of the ex vivo stenosis by high-resolution magnetic resonance imaging correlated closely with the size of stenosis determined by the acrylic specimen casts ( r = 0.92). By ex vivo measurement, the lesions were placed in the following size categories: 40% to 59% stenosis ( n = 2), 60% to 79% stenosis ( n = 6), 80% to 89% stenosis ( n = 7), and 90% to 99% stenosis ( n = 16).Conclusions: In general, the correlation of measurements of ex vivo stenosis with all modalities was good in these severely diseased arteries, although it was better for DUS ( r = 0.80; p < 0.001) and MRA ( r = 0.76; p < 0.001) than for CA ( r = 0.56; p < 0.05). (J VASC SURG 1995;21:82-9.)     

Proposed new duplex classification for threshold stenoses used in various symptomatic and asymptomatic carotid endarterectomy trials

Current duplex ultrasound criteria for internal carotid artery (ICA) stenosis (1%–15%, 16%–49%, 50%–69%, 70%–99%) may not be applicable to threshold stenoses used in symptomatic (North American Symptomatic Carotid Endarterectomy Trial [NASCET], Veterans’ Administration [VA]) and asymptomatic (Asymptomatic Carotid Atherosclerosis Study, VA) carotid endarterectomy (CEA) trials. This, along with increasing reports advocating CEA based on duplex results alone, prompted us to identify (1) new velocity criteria consistent with threshold stenoses used by these trials, and (2) velocity criteria with a high positive predictive value (PPV) (> 95%) and accuracy for detecting ⩾ 60% and ⩾ 70% ICA stenoses. This is the first study to propose criteria which can be used for all current CEA trials. The color duplex ultrasound (CDU) and arteriogram results of 462 ICAs were analyzed in blind fashion. Angiographic stenosis was calculated as in NASCET. Three velocity criteria (peak systolic velocity [PSV] of the ICA, end diastolic velocity [EDV] of the ICA, and the ratio of the PSV of the ICA/common carotid artery) were recorded and subjected to receiver operator characteristic curves (ROC) analysis to determine optimum criteria for identifying ICA stenoses of ⩾ 30%, ⩾ 50%, ⩾ 60%, and ⩾= 70%-99%. For ⩾ 30% stenosis (st): PSV ⩾ 120 cm/sec had an overall accuracy (OA) of 87%, sensitivity (sen.) of 93%, specificity (spec.) of 67%, PPV of 90%, and negative predictive value (NPV) of 77%; for ⩾ 50% st: PSV ⩾ 140 cm/sec had an OA of 93%, sen. of 92%, spec, of 95%, PPV of 97%, and NPV of 89%; for ⩾ 60% st: PSV ⩾ 150 cm/sec and an EDV of ⩾ 65 had an OA of 90%, sen. of 82%, spec, of 97%, PPV of 96%, and NPV of 86%; for ⩾ 70%–99% st: PSV ⩾ 150 cm/sec and an EDV of ⩾ 90 had an OA of 92%, sen. of 85%, spec, of 95%, PPV of 91%, and NPV of 92%. An ICA-PSV and EDV of 150, 65, and 150,110 had the best PPV (⩾ 95%) in detecting ⩾ 60% and ⩾ 70% st, respectively. When these new criteria are used, CDU can accurately detect threshold stenoses used by various CEA trials. Selected velocities with a high PPV (> 95%) may be used as the sole preoperative imaging. Presented at the 21st Annual Meeting of the Southern Association for Vascular Surgery, January 24–27, 1997. Coronado, CA.     

Duplex ultrasound criteria for defining the severity of carotid stenosis

Duplex ultrasound scan (DUS) criteria for grading >50% carotid artery stenosis is typically divided into broad categories such as 50-79% stenosis, 80-99% stenosis, and occlusion. The purpose of this study is to validate DUS criteria for stratifying 50 to 100% carotid stenosis into 10% intervals using digital substraction cerebral angiography (DSCA) as the standard of comparison. Between 1996 and 2001, 163 patients were evaluated with duplex ultrasound and angiography. A total of 326 carotid arteries were studied using DUS in an accredited ICAVL vascular laboratory. Threshold velocity criteria for determining the degree of carotid stenosis was defined according to seven categories: <50%, 50-59%, 60-69%, 70-79%, 80-89%, 90-99%, and occlusion. Treatment decisions were based on the angiographic findings. In cases where the degree of stenosis as defined by duplex velocity criteria did not correlate with angiographically defined stenosis, each record was reviewed to determine whether the angiographic findings altered the surgeon's treatment decision. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for DUS-defined degree of stenosis as compared to angiographically defined stenosis were determined. There was a high correlation (R = 0.96) between duplex scan and angiography in 93% (302/326) of the cases. Clinical management was altered in only 3% (10/326) of the cases because of the results of angiography. The DUS velocity criteria to grade the severity of carotid disease in 10% intervals is reliable and accurate. Clinical management of patients with carotid stenosis can be based solely on carotid DUS in 97% of patients considered for treatment of carotid artery disease.     

Carotid duplex velocity criteria revisited for the diagnosis of carotid in-stent restenosis

Carotid percutaneous transluminal angioplasty/stenting has become an accepted treatment modality for carotid artery stenosis in high-risk patients. There has been an ongoing debate regarding which duplex ultrasound (DUS) criteria to use to determine the rate of in-stent restenosis. This prospective study revisits DUS criteria for determining the rate of in-stent restenosis. In analyzing a subset of 12 patients (pilot study) who had both completion carotid angiography and DUS within 30 days, 10 patients with normal post-stenting carotid angiography (< 30% residual stenosis) had peak systolic velocities (PSVs) of the stented internal carotid artery (ICA) of < or = 155 cm/s and two patients with > or = 30% residual stenosis had internal carotid artery (ICA) PSVs of > 155 cm/s. Eighty-three patients who underwent carotid stenting as part of clinical trials were analyzed. All patients underwent post-stenting carotid DUS that was done at 1 month and every 6 months thereafter. PSVs and end-diastolic velocities of the ICA and common carotid artery were recorded. Patients with PSVs of the ICA of > 140 cm/s underwent carotid computed tomographic (CT) angiography. The perioperative stroke rate was 1.2%. When the old DUS velocity criteria for nonstented carotid arteries were applied, 54% of patients had > or = 30% restenosis (PSV of > 120 cm/s), but when our new proposed DUS velocity criteria for stented arteries were applied (PSV of > 155 cm/s), 33% had > or = 30% restenosis at a mean follow-up of 18 months (p = .007). The mean PSVs for patients with normal stented carotid arteries based on CT angiography, were 122 cm/s versus 243 cm/s for > or = 30% restenosis and 113 cm/s versus 230 cm/s for > or = 30% restenosis based on our new criteria. The mean PSVs of in-stent restenosis of 30 to < 50%, 50 to < 70%, and 70 to 99%, based on CT angiography, were 205 cm/s, 264 cm/s, and 435 cm/s, respectively. Receiver operating curve analysis demonstrated that an ICA PSV of > 155 cm/s was optimal for detecting > or = 30% in-stent restenosis, with a sensitivity of 100%, a specificity of 90%, a positive predictive value of 74%, and a negative predictive value of 100%. The currently used carotid DUS velocity criteria overestimated the incidence of in-stent restenosis. We propose new velocity criteria for the ICA PSV of > 155 cm/s to define > or = 30% in-stent restenosis.     

Comparison of intra-arterial digital subtraction angiography, magnetic resonance angiography and duplex ultrasonography for measuring carotid artery stenosis

BACKGROUND: Duplex ultrasonography and magnetic resonance angiography (MRA) are becoming competitive alternatives to angiography for determining the degree of internal carotid artery (ICA) stenosis. Varying reports have been published regarding the suitability of each technique for grading ICA disease. This retrospective study compared the merits of these three modalities for measuring ICA stenosis. METHODS: One hundred and eleven patients being considered for carotid endarterectomy underwent intra-arterial digital subtraction angiography (DSA) via arch injection. Duplex imaging was performed in all patients and MRA in 50. The degree of carotid stenosis estimated by the three modalities was compared. RESULTS: There was good correlation between subjectively graded MRA and DSA images (r = 0.87, P < 0.001, n = 82 carotids) but poor correlation for objective estimates. MRA tended to underestimate the degree of stenosis (bias - 4.5 per cent) compared with DSA, but showed good correlation with duplex ultrasonography estimates (r = 0. 86, P < 0.001, n = 87 carotids). Both non-invasive modalities produced high values of sensitivity and specificity in estimating stenoses of greater than 70 per cent. MRA was less sensitive for distinguishing between severe stenosis and complete occlusion. CONCLUSION: This study did not resolve the debate regarding the method of choice as both MRA and duplex ultrasonography were accurate for imaging carotid stenoses.     

MR angiography in patients with subarachnoid hemorrhage: adequate to evaluate vasospasm-induced vascular narrowing?

The diagnosis of cerebral vasospasm (CVS) following subarachnoid hemorrhage (SAH) is still challenging. We evaluate the accuracy of time of flight MR angiography (TOF-MRA) to assess the arterial diameters of the circle of Willis in SAH patients with suspected CVS. MR examinations (1.5 Tesla) including 3D TOF-MRA with maximum intensity projections (MIP) and digital subtraction angiography (DSA) were performed within 24 h in 21 patients with acute aneurysmal SAH and suspicion of CVS. Arterial diameters of the circle of Willis including the distal internal carotid artery (ICA) were measured as ratios to the extradural ICA in standard projections. The diagnosis of CVS was established by comparing the luminal size of baseline and follow-up DSA. The correlation between the arterial ratios measured on MIP angiograms and on follow-up DSA was assessed with Pearson's linear regression analysis. Arterial ratios on MIP angiograms were categorized as correct, overestimated, and underestimated compared to the ratios on follow-up DSA. Pearson's correlation coefficient between the ratios of MIP angiograms and DSA was r = 0.5799 and the regression coefficient was b = 0.4775. Highest correlation was found for the category of severe CVS (r = 0.8201). Of all MIP angiograms, 34.9% showed consistent results compared to the DSA, while 44.2% of MIP images overestimated the vascular narrowing. Standard MIP angiograms from TOF-MRA are not accurate to assess vascular narrowing in patients with suspected CVS after aneurysmal SAH. The multifocal arterial stenoses in CVS may induce severe changes in blood flow dynamics, which compromise the diagnostic accuracy of the TOF-MRA.     

Duplex ultrasound velocity criteria for the stented carotid artery

OBJECTIVES: Ultrasound velocity criteria for the diagnosis of in-stent restenosis in patients undergoing carotid artery stenting (CAS) are not well established. In the present study, we test whether ultrasound velocity measurements correlate with increasing degrees of in-stent restenosis in patients undergoing CAS and develop customized velocity criteria to identify residual stenosis > or =20%, in-stent restenosis > or =50%, and high-grade in-stent restenosis > or =80%. METHODS: Carotid angiograms performed at the completion of CAS were compared with duplex ultrasound (DUS) imaging performed immediately after the procedure. Patients were followed up with annual DUS imaging and underwent both ultrasound scans and computed tomography angiography (CTA) at their most recent follow-up visit. Patients with suspected high-grade in-stent restenosis on DUS imaging underwent diagnostic carotid angiograms. DUS findings were therefore available for comparison with luminal stenosis measured by carotid angiograms or CTA in all these patients. The DUS protocol included peak-systolic (PSV) and end-diastolic velocity (EDV) measurements in the native common carotid artery (CCA), proximal stent, mid stent, distal stent, and distal internal carotid artery (ICA). RESULTS: Of 255 CAS procedures that were reviewed, 39 had contralateral ICA stenosis and were excluded from the study. During a mean follow-up of 4.6 years (range, 1 to 10 years), 23 patients died and 64 were lost. Available for analysis were 189 pairs of ultrasound and procedural carotid angiogram measurements; 99 pairs of ultrasound and CTA measurements during routine follow-up; and 29 pairs of ultrasound and carotid angiograms measurements during follow-up for suspected high-grade in-stent restenosis > or =80% (n = 310 pairs of observations, ultrasound vs carotid angiograms/CTA). The accuracy of CTA vs carotid angiograms was confirmed (r(2) = 0.88) in a subset of 19 patients. Post-CAS PSV (r(2) = .85) and ICA/CCA ratios (r(2) = 0.76) correlated most with the degree of stenosis. Receiver operating characteristic analysis demonstrated the following optimal threshold criteria: residual stenosis > or =20% (PSV >or =150 cm/s and ICA/CCA ratio > or =2.15), in-stent restenosis > or =50% (PSV > or =220 cm/s and ICA/CCA ratio > or =2.7), and in-stent restenosis > or =80% (PSV 340 cm/s and ICA/CCA ratio > or =4.15). CONCLUSIONS: Progressively increasing PSV and ICA/CCA ratios correlate with evolving restenosis within the stented carotid artery. Ultrasound velocity criteria developed for native arteries overestimate the degree of in-stent restenosis encountered. These changes persist during long-term follow-up and across all grades of in-stent restenosis after CAS. The proposed new velocity criteria accurately define residual stenosis >or =20%, in-stent restenosis >or =50%, and high-grade in-stent restenosis > or =80% in the stented carotid artery.     

An innovative method for detecting surgical errors using indocyanine green angiography during carotid endarterectomy: a preliminary investigation

Background  

Carotid endarterectomy (CEA) is the most effective treatment method of carotid stenosis or occlusion. Surgeons typically check the blood flow in each vessel using Duplex Doppler ultrasonography or radiocontrast angiography in order to prevent postoperative complications. Embolic cerebral infarction on the ipsilateral side has been reported in 4–7% of patients undergoing CEA despite a tolerable blood flow reported by Duplex ultrasonography. This study was designed to evaluate a new intraoperative method for detecting technical errors during CEA using indocyanine green (ICG) angiography.     

Modalities of preoperative imaging of the internal carotid artery used in France

A survey of the 382 members of the Société de Chirurgie Vasculaire de Langue Fran?aise was conducted to determine preferred imaging techniques for preoperative assessment of the proximal internal carotid artery. A total of 180 questionnaires were returned concerning 9390 carotid stenoses treated in the year 2000. Doppler ultrasound (DUS), angiography, magnetic resonance angiography (MRA), and computed tomography angiography (CTA) were routinely used in 99%, 51.5%, 4%, and 3% of cases. Usual work-up methods involved DUS and angiography in 64% of cases, DUS and MRA in 7%, and DUS and CTA in 4% of cases. Indications for endarterectomy were based on DUS and angiography findings in 69% of cases, on DUS and MRA findings in 14%, on DUS and CTA findings in 9%, and on DUS findings alone in 8%. In-house access to CTA or MRA was more frequent at state-run institutions (p = 0.00001). Indication of endarterectomy based on DUS and MRA was more common at institutions equipped with technical facilities for MRA (21% vs. 8%; p = 0.001). An inverse correlation was observed between the number of carotid artery procedures performed and use of DUS and angiography work-up. The number of carotid endarterectomies without angiography is increasing in France. Preoperative DUS is still routinely used. Combined DUS and MRA is the preferred work-up for endarterectomy without angiography. Lack of access to MRA is still a limiting factor. Further study will be needed to evaluate the benefits and risks of endarterectomy without angiography.     

Cross-sectional Magnetic Resonance Angiography Is Accurate in Predicting Degree of Carotid Stenosis

Carotid stenosis is currently estimated using methods based on flow velocity or two-dimensional projection images. Manipulation of magnetic resonance (MR) images in three dimensions (3-D MR) allows for direct measurement of carotid artery cross-sectional luminal area. The objectives of this study were (1) to assess the accuracy of 3-DMR as a technique for estimating carotid artery stenosis, and (2) to compare 3-D MR results with estimates from duplex ultrasound sonography (DUS) and conventional angiography. Twenty-nine patients underwent rapid, contrast-enhanced MRA within 1 month prior to carotid endarterectomy to obtain 3-D angiographic images of the carotid bifurcation. From these data, post-processing software was used to generate a longitudinal axis through the center of the vessel along which orthogonal cross-sectional images were taken. Luminal area measurements at the location of tightest stenosis and the distal normal internal carotid artery were obtained and used to calculate percent area stenosis. Applying the same procedure, 18 en bloc, ex vivo carotid plaques served as the standard against which we compared in vivo 3-D MR measurements at the location of tightest stenosis. Percent stenosis comparisons between MRA, angiography, and duplex ultrasound were also made. Our results showed that the measurement of luminal area by 3-DMR is accurate in predicting the degree of carotid stenosis. Direct measurement of luminal area may overcome limitations inherent to methods that rely on flow velocities and two-dimensional views of the carotid vasculature. A larger prospective study is necessary to confirm the reliability of this technique.     

CTP与HR-MRI对颈动脉狭窄患者行颈动脉支架置入术疗效的评估及应用价值

背景与目的 颈动脉狭窄是导致脑卒中尤其是缺血性脑卒中的重要原因,早期发现及有效治疗是减少缺血性脑卒中发生的关键。颈动脉支架置入术（CAS）是治疗颈动脉狭窄的常用方法,但术中和术后可能发生各种并发症,以及发生再次狭窄或闭塞的风险,因此,通过有效的方法对其进行疗效评估具有重要的临床意义。本研究分析CT灌注成像（CTP）与高分辨磁共振成像（HR-MRI）对颈动脉狭窄患者CAS术后疗效的评估效能。方法 收集2017年2月—2020年2月期间44例颈动脉狭窄并接受CAS治疗的患者资料,所有入选患者于手术前、手术后2个月行CTP、HR-MRI以及DSA检查,比较患者手术前后CTP与HR-MRI参数的差异,以DSA检查结果作为金标准,比较两种方法诊断颈动脉残余狭窄的效能。结果 CTP结果显示,与术前比较,患者术后2个月大脑动脉相对脑血流量明显增多,相对通过时间、相对达峰时间明显减少（均P<0.05）,相对脑血容量无明显差异（P>0.05）;HR-MRI结果显示,与术前比较,患者术后2个月血管面积、管壁面积以及管腔面积无明显差异（均P>0.05）,斑块面积、斑块负荷明显减小（均P<0.05）。DSA检查出16支颈动脉存在狭窄,颈动脉狭窄改善率为80.00%,CTP检查出颈动脉存在狭窄12支,颈动脉狭窄改善率为85.00%,HR-MRI检查出颈动脉存在狭窄14支,颈动脉狭窄改善率为82.50%,两种检查方式对颈动脉残余狭窄的诊断效能相当（P>0.05）。结论 CTP、HR-MRI均可用于颈动脉狭窄患者CAS疗效评估,两种方法补充使用,具有一定的临床应用价值。     

Medical management versus investigate-and-operate strategy in asymptomatic carotid stenosis: a decision analysis

OBJECTIVE: The objective of this study was to determine whether asymptomatic patients at high risk for carotid stenosis should undergo screening Duplex ultrasound (DUS), with a view to offering carotid endarterectomy (CE) to those patients with significant stenosis. METHOD: We constructed a decision analysis model to evaluate the impact of an investigate-and-operate strategy, compared with medical management alone, on the risk of stroke in patients at high risk for carotid stenosis. We studied five investigate-and-operate models addressing different thresholds for intervention (in terms of degree of stenosis) and the effects of using or not using preoperative angiography. RESULTS: For each of the strategies, under the base case conditions (30% prevalence of >50% carotid stenosis), the number needed to screen (NNS) and the number needed to treat (NNT) are high (213 to 769 and 13 to 144, respectively). The strategy of angiography for >50% stenosis and CE for >70% stenosis was harmful. Other strategies were unattractive because of unacceptably high NNT (no angiography, CE >50% stenosis), or because of unacceptably high NNS (angiography >70%, CE >70% stenosis), or both (angiography >50% stenosis, CE >50% stenosis; no angiography, CE > 70% stenosis). At 50% prevalence of >50% stenosis, two models produced more reasonable combinations of NNT and NNS: 11 and 370, respectively, for angiography >70%, CE >70% stenosis; and 27 and 286, respectively, for no angiography, CE >70% stenosis. Within the range of clinically plausible values for sensitivity and specificity of DUS, results were not greatly influenced by the measurement properties of DUS. However, angiographic or surgical rates of stroke or death were critical to the outcomes with any strategy. Only 3% to 12% of strokes in the studied population were prevented. CONCLUSIONS: Screening is acceptable only in populations at >40% to 50% risk for >50% carotid stenosis, who are surgical candidates, and who would undergo surgery if recommended. Acceptable investigate-and-operate strategies include angiography for DUS stenosis >70%, with CE if this level of stenosis is confirmed, and CE for DUS-measured stenosis >70% without angiographic confirmation. Surgery for asymptomatic carotid stenosis is unlikely to have a large impact upon the burden of stroke in society.     

Prospective evaluation of new duplex criteria to identify 70% internal carotid artery stenosis

Purpose: Large multicenter trials (North American Symptomatic Carotid Endarterectomy Trial, European Carotid Surgery Trial) have documented the benefits of carotid endarterectomy for treating symptomatic patients with ≥70% stenosis of the internal carotid artery. Although color-flow duplex scanning has become the preferred method for noninvasive assessment of internal carotid artery disease, no criteria have been generally accepted to identify this subset of patients. We previously reported a retrospective series to establish such criteria. This study details our results when these criteria were applied prospectively.Methods: Carotid color-flow duplex scans were compared with arteriograms in 457 patients who underwent both studies. Criteria for ≥70% internal carotid artery stenosis were peak systolic velocity >130 cm/sec and end-diastolic velocity >100 cm/sec. Internal carotid arteries with peak systolic velocity <40 cm/sec in which only a trickle of flow could be detected were classified as preocclusive lesions (95% to 99% stenosis). Arteriographic stenosis was determined by comparing the diameter of the internal carotid artery at the site of maximal stenosis to the diameter of the normal distal internal carotid artery.Results: Internal carotid artery stenosis of ≥70% was detected with a sensitivity of 87%, specificity of 97%, positive predictive value of 89%, negative predictive value of 96%, and overall accuracy of 95%. Eighty-seven percent of 70% to 99% stenoses were correctly identified. False-positive errors (n = 10) were attributed to contralateral internal carotid artery occlusion or high-grade (>90%) stenosis (n = 5) and to interpreter error (n = 1); no explanation was apparent in the other four. Eleven of 12 false-negative examinations occurred in patients with 70% to 80% internal carotid artery stenosis.Conclusions: In our laboratories, prospective application of the above velocity criteria identified internal carotid artery stenosis of ≥70% with a reasonably high degree of accuracy. Errors occurred when stenoses were borderline and in patients with severe contralateral disease. With suitably modified velocity criteria, color-flow duplex scanning remains the most reliable noninvasive method for identifying symptomatic patients who are candidates for carotid endarterectomy. (J V ASC S URG 1996;23:254-62.)     

Carotid endarterectomy in asymptomatic patients — Is contrast angiography necessary? A morbidity analysis

Purpose: Findings from the Asymptomatic Carotid Atherosclerosis Study (ACAS) indicate that carotid endarterectomy can be beneficial in symptom-free patients with 60% to 99% carotid artery stenosis. However, patients in ACAS who underwent contrast angiography (CA) before carotid endarterectomy were exposed to an additional 1.2% risk of stroke.Methods: We used the methods of decision analysis to assess whether the overall 5-year stroke risk in symptom-free patients with suspected carotid artery disease can be reduced by preoperative imaging with magnetic resonance angiography (MRA) or duplex ultrasonography (DU). We compared four strategies for the preoperative evaluation of carotid artery stenosis in symptom-free patients: 1) CA alone, 2) MRA alone, 3) DU alone, and 4) MRA and DU with CA when the results of these tests disagree. Accuracies of MRA and DU were estimated from 81 patients exposed to all three procedures; stroke risks for patients with 60% to 99% carotid artery stenosis were obtained from ACAS.Results: For predicting 60% to 99% carotid stenoses, sensitivity and specificity for noninvasive tests, optimized to reduce morbidity, were as follows: DU (0.96, 0.66), MRA (1.00, 0.76), DU/MRA (1.00, 0.86; 26% would require CA). The 5-year stroke risk of these four strategies in order of decreasing benefit was MRA, 6.17%; MRA/DU, 6.34%; DU, 6.35%; and CA, 7.12%. In sensitivity analyses, noninvasive tests were advantageous even if the stroke rate with CA diminished to 0.4%, or if the sensitivity and specificity of noninvasive tests fell to 70%.Conclusion: The preoperative use of noninvasive tests resulted in a lower 5-year stroke risk compared with CA in symptom-free patients with suspected carotid artery stenosis. (J VASC SURG 1995;22:706-16.)     

Duplex Ultrasound Verified by Angiography in Patients with Severe Primary and Restenosis of Internal Carotid Artery

There are very limited data in the literature about the reliability of duplex ultrasound (DU) verified by angiography in patients with restenosis of the internal carotid artery (ICA) after carotid surgery compared with primary carotid artery stenosis patients. Our objective was to compare the reliability of DU verified by conventional angiography in the diagnosis of severe primary stenosis versus restenosis of ICA. One hundred thirty-four patients (238 arteries) were examined by both DU and angiography. Severe stenosis (>70%) was found in 47 primary stenotic arteries and in 70 restenotic arteries. Accuracy, specificity, sensitivity, positive predictive value (PPV), and negative predictive value were obtained for basic DU criteria after verification of ultrasound data by angiography. The best accuracy for detection of >70% stenosis by end diastolic velocity was found for the velocity of 70 cm/sec or more in both groups, but accuracy for the restenosis group was significantly higher (96.9% vs. 89.8%, p = 0.025). Additionally, specificity (p = 0.01) and PPV (p = 0.01) were significantly higher in the restenosis group. The best accuracy for detection of >70% stenosis by peak systolic velocity was found for the velocity of 220 cm/sec or more for restenoses and 200 cm/sec or more for primary stenoses. The accuracy of the ultrasound was significantly higher in the restenosis group (94.6% vs. 87%, p = 0.04), as were specificity (p = 0.01) and PPV (p = 0.02). The diagnosis of severe restenosis by DU is reliable and can be used for decision making regarding surgery or stenting without angiography. In patients with Doppler parameters pointing to borderline moderate/severe primary carotid stenosis and technically complicated cases, angiography in addition to sonography before surgery is recommended.     

Helical CT angiography in the preoperative evaluation of carotid artery stenosis

Purpose: To determine the utility and accuracy of helical CT angiography (CTA) in the evaluation of carotid artery stenosis. Methods: A comparison of CTA and conventional arteriogram was performed in 53 patients undergoing evaluation for carotid artery stenosis. Ninety-six carotid systems were evaluable. CTA stenosis was determined by the percent of area reduction seen on axial images through the level of greatest narrowing. MIP images were used to identify the point of maximal stenosis and to visualize overall vascular anatomy. The percent diameter stenosis was measured on conventional arteriograms using strict North American Symptomatic Carotid Endarterectomy Trial (NASCET) and European Carotid Surgery Trial (ECST) criteria. Results: Significant correlation was found between CTA and arteriography (NASCET method R = 0.87, ECST method R = 0.87, p < 0.001). Using NASCET >60% as an indicator for disease, CTA had a sensitivity of 87%, specificity of 90%, accuracy of 89%, negative predictive value of 88%, and positive predictive value of 89%. CTA identified plaque characteristics such as ulcerations (8), occlusion (10), fatty plaques (22), calcifications (48), and fibrosis (2). CTA underestimated 2 cases of short segment stenoses because of volume averaging, but this discrepancy was detected by duplex scan. No complications or renal dysfunction occurred with CTA; 1 patient became symptomatic during arteriography, necessitating termination of the procedure. Conclusion: CTA is a safe, non-invasive technique that precisely measures carotid artery area reduction and highly correlates to conventional arteriography. With this new technology, the current standards for carotid artery imaging may need to be reevaluated, and the precise role for helical CTA more clearly defined. (J Vasc Surg 1998;28:290-300.)     

The Utility of Contrast Enhanced MR Angiography as a First Stage Diagnostic Modality for Treatment Planning in Lower Extremity Arterial Occlusive Disease

Introduction: The aim of this study was to evaluate the applicability of contrast enhanced magnetic resonance angiography (ce-MRA) as a first stage imaging tool for individual treatment planning in patients with lower extremity arterial occlusive disease.

Patients and Methods: Between August, 2003 and June, 2004, in 128 consecutive patients (182 extremities) with clinical manifestations of lower limb ischemia eligible for invasive therapy, treatment was planned based on clinical assessment, ankle/brachial pressure index measurements combined with ce-MRA. Additional duplex ultrasonography (DUS) or digital subtraction angiography (DSA) was done when necessary. Ce-MRA findings were compared with findings during open surgical, endovascular or combined procedures.

Results: In 28 extremities (15%) ce-MRA was found inconclusive and additional imaging was performed. In the remaining patients (85% of the extremities (n = 154), treatment was initiated as planned. However, in 19 (11%) of these patients, the treatment plan was altered. In 7 of them, procedural findings did not correspond with those at the time of ce-MRA, including 6 patients (3%) with a falsely diagnosed stenosis or occlusion.

In total, 62 patients received non-operative treatment (34%), 65 an endovascular procedure (36%), 49 open surgical reconstruction (27%) and 6 a combined treatment.

Conclusions: We conclude that in the majority of patients treatment can be planned based on ce-MRA images, although sometimes additional DUS or DSA may be required.