Contrast-enhanced magnetic resonance angiography of carotid arteries: utility in routine clinical practice

Carotid Duplex Ultrasonography: Additional Imaging is Rarely Necessary for Appropriate Treatment Planning for Carotid Artery Disease

This study was conducted to determine the utility of multiple imaging studies (CT angiography, magnetic resonance angiography, and/or conventional angiography), in addition to duplex ultrasonography (DU), in evaluating patients with carotid stenosis. A retrospective case series was conducted of patients with carotid stenosis who underwent DU alone or DU plus additional imaging. Concordance between DU and additional imaging and the effect on treatment plan was evaluated. Two hundred patients with carotid stenosis were evaluated. Sixty-four had DU plus additional imaging. Sixty-two of the patients (96.9%) had no change in treatment due to additional imaging. Only 2 of the 64 patients (3.1%) with additional imaging had a change in treatment plan. In conclusion, additional imaging, beyond DU, is rarely necessary for treatment planning in patients with carotid disease.

Discharge on the first postoperative day after elective carotid endarterectomy

BACKGROUND

Medical complications may prolong the hospital stay after elective carotid endarterectomy (CEA). We prospectively assessed the social and medical feasibility and safety of patient discharge on the first postoperative day after elective CEA and unplanned readmissions.

METHODS

Between June 2011 and January 2012, 57 consecutive patients scheduled for elective CEA were enrolled with the aim of discharge on the first postoperative day if there were no medical contraindications and on the condition that the patient should not be left alone during the first day and night at home. CEA was carried out under local or general anesthesia. After discharge, the patients were contacted to ascertain the occurrence of arterial hypertension, cerebral hyperperfusion, focal cerebral ischemia, or hospital readmission.

RESULTS

Sixty-two CEA were carried out in 57 patients (33 men and 24 women ranging in age from 51-89 years). The indications for CEA were: asymptomatic high grade stenosis in 27, hemispheric transient ischemic attack in 12, amaurosis fugax in 6, recovered stroke in 16, and nonlateralizing signs in 1. There were no cases of perioperative stroke or death. Discharge on the first postoperative day was achieved in 45 cases (73%). In 15 cases (24%), discharge was on the second postoperative day because of the absence of a relative (12 cases) or for medical reasons (3 cases). Discharge was on day 3 in 1 case, and on day 10 in another, both for medical reasons. No cases of severe arterial hypertension, stroke, mortality, or readmission for reasons related to the CEA procedure were recorded up to postoperative day 30.

CONCLUSION

In this study, the majority of patients undergoing elective CEA were discharged safely on the first postoperative day. Social reasons, rather than medical reasons, underlied most cases of later discharge. There were no unplanned readmissions for complications of CEA.

Imaging of the carotid arteries: the role of duplex ultrasonography, magnetic resonance arteriography, and computerized tomographic arteriography

Stenosis of the internal carotid artery represents a major cause of stroke, with atherosclerosis representing the major pathophysiology of this stenosis. It is estimated that over 700,000 Americans suffer a stroke annually. A prompt and accurate diagnosis of carotid artery disease is critical when planning a therapeutic strategy. Physical examination is inaccurate in determining the presence and severity of carotid artery disease. Therefore, reliable imaging tests which offer little risk to the patient are required.

Indications for carotid artery surgery and stent: the role of carotid ultrasound

Carotid artery disease is the most frequently identified cause of ischemic stroke and is mostly due to atherosclerotic disease. Landmark trials have demonstrated that surgical intervention in cases of high-grade carotid stenosis can reduce the risk of subsequent stroke. Endovascular approaches continue to be evaluated in ongoing trials. Careful patient selection is critical if the potential benefits of carotid revascularization are to be realized. Ultrasound is a safe, accurate, readily available method to evaluate carotid artery disease. The degree of stenosis is the parameter most frequently used to make decisions about therapeutic approaches. Plaque characteristics may also be useful for identifying high-risk patients. Microembolic signals detected by transcranial Doppler ultrasound can identify cerebral embolization before or after carotid intervention. This review discusses the current clinical role of carotid ultrasound in the selection of patients for the two most frequently used carotid interventions: carotid endarterectomy or carotid angioplasty and stenting.

Accuracy and utility of three-dimensional contrast-enhanced magnetic resonance angiography in planning carotid stenting

BACKGROUND

Contrast-enhanced magnetic resonance angiography (CE-MRA) is a proven diagnostic tool for the evaluation of carotid stenosis; however, its utility in planning carotid artery stenting (CAS) has not been addressed. This study assessed the accuracy of three-dimensional CE-MRA as a noninvasive screening tool, compared with digital subtraction angiography (DSA), for evaluating carotid and arch morphology before CAS.

METHODS

In a series of 96 CAS procedures during a 2-year period, CE-MRAs and DSAs with complete visualization from the aortic arch to the intracranial circulation were obtained before CAS in 60 patients. Four additional patients, initially considered potential candidates for CAS, were also evaluated with CE-MRA and DSA. The two-by-two table method, receiver operating characteristic curve, and Bland-Altman analyses were used to characterize the ability of CE-MRA to discriminate carotid and arch anatomy, suitability for CAS, and degree of carotid stenosis.

RESULTS

The sensitivity and specificity of CE-MRA were, respectively, 100% and 100% to determine CAS suitability, 87% and 100% to define aortic arch type, 93% and 100% to determine severe carotid tortuosity, and 75% and 98% to detect ulcerated plaques. CE-MRA had 87% sensitivity and 100% specificity for the detection of carotid stenosis >/=80%. The accuracy of CE MRA to determine optimal imaging angles and stent and embolic protection device sizes was >90%. The operative technique for CAS was altered because of the findings of preoperative CE-MRA in 22 procedures (38%). The most frequent change in the operative plan was the use of the telescoping technique in 11 cases (18%). CAS was aborted in four patients (5%) due to unfavorable anatomy identified on CE-MRA, including prohibitive internal carotid artery tortuosity (n = 1), long string sign of the internal carotid artery (n = 2), and concomitant intracranial disease (n = 1). Among patients considered suitable for CAS by CE-MRA, technical success was 100%, and the 30-day stroke/death rate was 1.6%.

CONCLUSIONS

Contrast-enhanced magnetic resonance angiography of the arch and carotid arteries is accurate in determining suitability for CAS and may alter the operative technique. Certain anatomic contraindications for CAS may be detected without DSA. Although CE-MRA is less accurate to estimate the degree of stenosis, it can accurately predict imaging angles, and stent and embolic protection device size, which may facilitate safe and expeditious CAS.

Duplex Scanning Diagnosis of Internal Carotid Artery Dissections

BACKGROUND

The reliability of duplex scanning (DS) for the diagnosis of internal carotid artery dissections (ICAD) is not clear.

METHODS

Nine DS signs known to be suggestive for the diagnosis of ICAD were compared between 70 patients with ICAD and 70 matched patients without dissection.

RESULTS

Visible internal tapering occlusion, regular eccentric narrowing channel, ectasia beyond the carotid bulb, resistive index asymmetry, blood flow slowdown, ophthalmic artery blood flow inversion, and biphasic flow are more frequent in cases than in controls (p < 0.001). Atheroma plaques were absent in 80% of ICAD. When DS direct signs and hemodynamic signs were studied, sensitivity was 90% and specificity 60%.

CONCLUSION

Diagnosis of ICAD by DS could be improved if direct signs were combined with hemodynamic signs, giving a high sensitivity and a rather good specificity.

Practical noninvasive neurovascular imaging of the neck arteries in patients with stroke, transient ischemic attack, and suspected arterial disease that may lead to ischemia, infarction, or flow abnormalities

Stroke is the third leading cause of death in the United States, killing nearly 157,000 people a year with an estimated society cost of dollar 58 billion in 2006. A large percentage of ischemic strokes is secondary to extracranial carotid and vertebral arterial disease. While digital subtraction angiography has traditionally been used for the initial evaluation of the degree of stenosis, noninvasive imaging has moved to the forefront in the extracranial arterial evaluation. The importance of understanding the imaging techniques, findings, interpretation, artifacts, and pitfalls is essential to appropriate patient management.

Agreement of multislice CT angiography and MR angiography in assessing the degree of carotid artery stenosis in consideration of different methods of postprocessing

OBJECTIVE

We investigated the agreement of multislice computed tomography angiography (CTA) and magnetic resonance angiography (MRA) in the quantitative measurement of carotid artery stenosis. The dependency of the agreement of the chosen postprocessing procedures was also investigated.

METHODS

Fifty consecutive symptomatic patients were included in this study. In all patients, a CTA was performed with a 16-slice CT scanner. Within 30 days, the extracranial vessels were examined using a combined time-of-flight and contrast-enhanced MRA. The CT data sets were used to calculate the degree of stenosis according to the North American Symptomatic Carotid Endarterectomy Trial, European Carotid Surgery Trial, and Common Carotid methods by means of the 1-mm thick, transverse raw data (RD), a sagittal maximum-intensity projection reconstruction, and sagittal multiplanar reconstruction. In addition, a semiautomated analysis was done using a specialized postprocessing software. For all combinations of postprocessing procedures and methods of calculating the degree of stenosis, the correlation coefficient and the agreement based on Bland/Altman plots were calculated.

RESULTS

Eleven of the 100 primarily included carotid arteries could not be evaluated. The correlation coefficients for all combinations were comparable and lied in the interval between 0.932 and 0.787. The best correlation was found for the combination of RD/sagittal multiplanar reconstruction and ECST method. The evaluation of the agreement gave a systematic overestimation of CTA between 1.9% and 10.7% with a 95% confidence interval between +/-26.7% and +/-43.3%. With the semiautomated postprocessing software, additional 33 vessels could not be evaluated. The agreement of the calculated degrees of stenoses was worse than that of the planar procedures.

CONCLUSIONS

CTA and MRA had a feasible agreement in measuring the degree of stenosis of the carotid arteries. The best result could be obtained for the evaluation of the RD and the NASCET method. In this case one has to take into account a systematic overestimation of CTA of 1.9%. The combination with an additional reconstructive postprocessing procedure did not improve the result but might be useful for the radiologist to identify the location of the closest narrowing.

Contrast-Enhanced 3-D MRA in Decision Making for Carotid Endarterectomy: A 6-Year Experience

BACKGROUND

Systematic need for angiography in diagnosis of carotid artery stenosis and indication of surgical therapy is still debated. Noninvasive imaging techniques such as MR angiography (MRA) or CT angiography (CTA) offer an alternative to digital subtraction angiography (DSA) and are increasingly used in clinical practice. In this study, we present the radiological characteristics and clinical results of a series of patients operated on the basis of combined ultrasonography (US)/MRA.

METHODS

This observational study included all the patients consecutively operated for a carotid stenosis in our Department from October 1998 to December 2004. The applied MRA protocol had previously been established in a large correlation study with DSA. DSA was used only in case of discordance between US and MRA. The preoperative radiological information furnished by MRA was compared with intraoperative findings. The outcome of the operation was assessed according to ECST criteria.

RESULTS

Among 327 patients, preoperative MRA was performed in 278 (85%), DSA in 44 (13.5%) and CT angiography in 5 (1.5%). Most of DSA studies were performed as emergency for preparation of endovascular therapy or for reasons other than carotid stenosis. Eleven additional DSA (3.3%) complemented US/MRA, mostly because diverging diagnosis of subocclusion of ICA. No direct morbidity or intraoperative difficulty was related to preoperative MRA. Combined mortality/major morbidity rate was 0.9% (3 patients) and minor morbidity rate 5.5% (18 patients).

CONCLUSIONS

This observational study describes a well-established practice of carotid surgery and supports the exclusive use of non invasive diagnostic imaging for indicating and deciding the operation.

The reliability of ultrasound measurements of carotid stenosis compared to MRA and DSA

OBJECTIVE

Carotid ultrasound (US) is a screening test for patients with transient ischemic attacks (TIAs) or stroke who then undergo Digital Subtraction Angiogram (DSA) or Magnetic Resonance Angiography (MRA). Gold standard DSA is invasive with inherent risks and costs. MRA is an evolving technology. This study compares reliability of MRA and US modes with DSA in determining degree of internal carotid artery stenosis.

METHODS

A five year retrospective analysis of 140 carotid arteries from patients who had carotid US and DSA, and possibly Magnetic Resonance Angiography was undertaken. Recorded US parameters were peak systolic velocity (PSV), end diastolic velocity (EDV), and ICA/CCA peak systolic velocity ratio. The MRA and DSA parameters used NASCET technique for measuring stenosis. Statistical analysis included ROC curves and Kappa computation.

RESULTS

US grading of carotid stenosis can be made more reliable by choosing appropriate parameters. The best combination of sensitivity and specificity for stenosis > 70% in our hospital was seen at PSV > 173 cm/s (sensitivity 0.87, specificity 0.8, Positive Predictive Value (PPV) 0.70, Negative Predictive Value (NPV) 0.93, kappa 0.64 and weighted kappa 0.71). MRA kappa was 0.78, (sensitivity 0.75, specificity 1.0, PPV 1.0, NPV 0.85).

CONCLUSIONS

US parameters should be validated in each centre. At best, US can only approximate the accuracy of DSA, probably due to inherent limitations of this modality. Magnetic Resonance Angiography has a perfect specificity and PPV but this technique needs to be standardized. Simultaneous use of MRA and US for screening increases sensitivity to over 0.9 without compromising specificity in > 70% stenosis.

Diagnosing carotid stenosis by Doppler sonography: state of the art

OBJECTIVE

The goal of this review article is to present the state of the art in the clinical applications and technical performance and interpretation of carotid sonographic examinations.

METHODS

Relevant publications regarding color and duplex Doppler sonography (CDDS) of the carotid arteries extracted from a computerized database (MEDLINE) and from references cited in these articles not appearing on the Internet were reviewed.

RESULTS

The ability to quickly and efficiently identify stenosis in the carotid artery is an important goal for clinicians and vascular surgeons. Identification of potentially treatable carotid stenosis enables selection of appropriate candidates for endarterectomy or stent implantation. Advances in performance and interpretation of carotid sonographic studies over the last 20 years have been driven by technological improvements in gray scale and CDDS examinations and have made carotid sonography an important means to reach this goal. On the basis of CDDS, intima-media thickness measurements and plaque location and characterization on gray scale imaging, flow disturbance and areas of stenosis on color Doppler sonography, and flow velocities on spectral Doppler sonography are obtained. The degree of the diameter of a stenosis of the internal carotid artery is the main parameter used for therapeutic approaches. Advantages and limitations of the method are included.

CONCLUSIONS

Carotid sonography is a unique imaging method for the investigation of carotid abnormalities. Noninvasive, accurate, and cost-effective, it provides morphologic and functional information. It is increasingly becoming the first and often the sole imaging study before endarterectomy, whereas costly and invasive procedures are reserved for special cases.

Carotid Artery Stenosis: Intraindividual Correlations of 3D Time-of-Flight MR Angiography, Contrast-enhanced MR Angiography, Conventional DSA, and Rotational Angiography for Detection and Grading

PURPOSE

To compare three-dimensional (3D) time-of-flight (TOF) MR angiography, contrast-enhanced MR angiography, digital subtraction angiography (DSA), and rotational angiography for depiction of stenosis.

MATERIALS AND METHODS

The study had Ethics Committee approval, and each patient gave written informed consent. Forty-nine patients (18 women, mean age, 67.2 years +/- 9.1 [+/- standard deviation], and 31 men, mean age, 63.1 years +/- 8.0) with symptomatic stenosis of internal carotid artery (ICA) diagnosed at duplex ultrasonography underwent transverse 3D TOF MR angiography with sliding interleaved kY acquisition and coronal contrast-enhanced MR angiography, followed by DSA and rotational angiography within 48 hours. MR angiography was performed at 1.5-T with a cervical coil. Contrast-enhanced MR angiograms were obtained after a bolus injection of 20 mL of gadobenate dimeglumine. Maximum ICA stenosis on maximum intensity projection and source images was quantified according to NASCET criteria. Correlations for 3D TOF MR angiography, contrast-enhanced MR angiography, DSA, and rotational angiography were determined by means of cross tabulation, and accuracy for detection and grading of stenoses were calculated. Data were evaluated with analysis of variance, Wilcoxon signed rank test, and McNemar test, all at significance of P < .05.

RESULTS

Ninety-eight ICAs were evaluated at contrast-enhanced MR angiography, DSA, and rotational angiography, and 97 were evaluated at 3D TOF MR angiography. Correlations for contrast-enhanced MR angiography, 3D TOF MR angiography, and DSA relative to rotational angiography were r2 = 0.9332, r2 = 0.9048, and r2 = 0.9255, respectively. Lower correlation (r2 = 0.8593) was noted for contrast-enhanced MR angiography and DSA. Respective sensitivity and specificity for detection of hemodynamically relevant stenosis relative to rotational angiography were 100% and 90% for contrast-enhanced MR angiography, 95.5% and 87.2% for 3D TOF MR angiography, and 88.6% and 100% for DSA. Four of 31 severe stenoses were underestimated at DSA, and three were underestimated at contrast-enhanced MR angiography. Three severe stenoses were underestimated at 3D TOF MR angiography, and one was misclassified as occluded. Of 13 moderate (50%-69%) stenoses, one was overestimated at contrast-enhanced MR angiography, two were underestimated and three overestimated at 3D TOF MR angiography, and two were underestimated at DSA.

CONCLUSION

DSA results in an underestimation of ICA stenosis compared with rotational angiography. Contrast-enhanced MR angiography correlates best with rotational angiography.

Recommendations for Comprehensive Stroke Centers

Background and Purpose— To develop recommendations for the establishment of comprehensive stroke centers capable of delivering the full spectrum of care to seriously ill patients with stroke and cerebrovascular disease. Recommendations were developed by members of the Brain Attack Coalition (BAC), which is a multidisciplinary group of members from major professional organizations involved with the care of patients with stroke and cerebrovascular disease.

Summary of Review— A comprehensive literature search was conducted from 1966 through December 2004 using Medline and Pub Med. Articles with information about clinical trials, meta-analyses, care guidelines, scientific guidelines, and other relevant clinical and research reports were examined and graded using established evidence-based medicine approaches for therapeutic and diagnostic modalities. Evidence was also obtained from a questionnaire survey sent to leaders in cerebrovascular disease. Members of BAC reviewed literature related to their field and graded the scientific evidence on the various diagnostic and treatment modalities for stroke. Input was obtained from the organizations represented by BAC. BAC met on several occasions to review each specific recommendation and reach a consensus about its importance in light of other medical, logistical, and financial factors.

Conclusions— There are a number of key areas supported by evidence-based medicine that are important for a comprehensive stroke center and its ability to deliver the wide variety of specialized care needed by patients with serious cerebrovascular disease. These areas include: (1) health care personnel with specific expertise in a number of disciplines, including neurosurgery and vascular neurology; (2) advanced neuroimaging capabilities such as MRI and various types of cerebral angiography; (3) surgical and endovascular techniques, including clipping and coiling of intracranial aneurysms, carotid endarterectomy, and intra-arterial thrombolytic therapy; and (4) other specific infrastructure and programmatic elements such as an intensive care unit and a stroke registry. Integration of these elements into a coordinated hospital-based program or system is likely to improve outcomes of patients with strokes and complex cerebrovascular disease who require the services of a comprehensive stroke center.

Carotid angiography in contemporary vascular surgery practice

While most patients with carotid artery disease can safely undergo carotid endarterectomy based on duplex ultrasound alone, carotid angioplasty and stenting must, by its nature, be performed in conjunction with carotid arteriography. The techniques of carotid angiography are a necessary prerequisite to carotid intervention. The indications, technique, and results of carotid angiography in a contemporary vascular surgery practice are described.

Toward clinical equipoise: the current case for carotid angioplasty and stent placement

Recent advances in carotid artery (CA) stent placement procedures have propelled this technology into the forefront of treatment options for both symptomatic and asymptomatic patients with CA stenosis. Until recently, endarterectomy was the only surgical option for patients with CA occlusive disease. For high-risk surgical candidates, periprocedural stroke rates remained unacceptable and were significantly higher than those associated with the natural history of the disease. Advances in stent technology and improvements in antiplatelet and antithrombotic regimens, in conjunction with distal protection devices, have significantly lowered the risk of periprocedural complications for high-risk surgical candidates requiring CA revascularization. In this paper the authors review data gleaned from the important recent CA stent trials and address questions concerning the safety, efficacy, and durability of stent-assisted angioplasty for extracranial CA occlusive disease. Additionally, they review the role of noninvasive imaging modalities for the diagnosis and surveillance of CA disease in these high-risk patients.

Internal Carotid Artery Stenosis Measurement

Background and Purpose— Clinical trials have shown that carotid endarterectomy reduces stroke risk in symptomatic individuals with severe internal carotid artery (ICA) stenosis. As a result of these trials, digital subtraction angiography (DSA) became a standard of reference for ICA stenosis diagnosis. Newer 3D techniques provide a larger number of views than DSA, which may influence the estimated degree of stenosis. We evaluate this possibility by directly comparing stenosis grades from 3D computed rotational angiography (CRA) and DSA.

Methods— As a prospective diagnostic study, we performed CRA and DSA on 26 consecutive symptomatic patients. Only 1 angiographic procedure was performed on normal asymptomatic arteries, yielding 42 arteries for comparison. Four neuroradiologists graded the CRA maximum intensity projections (MIPs) and DSA images, according to the North American Symptomatic Carotid Endarterectomy Trial guidelines. CRA studies included a search for the narrowest view by evaluating 60 MIPs generated at 3° intervals and measurement of actual artery diameters. Artery diameters and stenosis grades were analyzed graphically; statistical significance was determined using a paired t test.

Results— The mean difference of 1.2% (CI, −18%, 21%) between CRA and DSA stenosis grades was not statistically significant ( P =0.55). Agreement of the optimal CRA viewing angle was limited, with an interobserver variability of 24±13°. The interobserver variability of DSA and CRA stenosis grades, 9.1% (CI, 0%, 21%) and 9.4% (CI, 0%, 22%), respectively, was not significantly different ( P =0.79).

Conclusion— CRA provides stenosis grades equivalent to DSA, as well as absolute measurements, providing a comparison for newer 3D techniques.

Can Carotid Angiography Be Performed by Vascular Surgeons? A Critical Evaluation of Indications, Technique, and Results

The purpose of this report is to examine the contemporary indications for diagnostic carotid arteriography and evaluate its utility and safety when performed by vascular surgeons. The records of all patients having selective carotid arteriography from September 2000 through March 2002 at our institution were reviewed. One hundred sixty-four consecutive patients had selective arteriography of the extracranial carotid arteries for the following indications: hemispheric symptoms with stenosis <80% by duplex ultrasound (20.6%), suspected brachiocephalic trunk stenosis (15.8%), unclear anatomy by duplex (10.3%), recurrent carotid stenosis (10.3%), symptomatic high-grade (>80% by duplex) internal carotid stenosis (9.8%), ipsilateral internal carotid artery occlusion (7.1%), bilateral high-grade internal carotid artery stenoses (7.1%), vertebral-basilar ischemia (7.0%), contralateral internal carotid occlusion (5.4%), duplex ultrasound from a nonaccredited vascular laboratory (3.3%), and evaluation of nonatherosclerotic carotid disease (3.3%). There were no transient ischemic attacks, strokes, or deaths related to the index procedure. Selective angiography of the extracranial carotid arteries remains an important adjunct in the evaluation of patients with carotid disease. This procedure can be performed safely by vascular surgeons.

Evaluation of Classic 2D Time-of-Flight MR Angiography in the Depiction of Severe Carotid Stenosis

OBJECTIVE

The purpose of this study is to determine the sensitivity, specificity, and clinical utility of classic 2D time-of-flight MR angiography (acquired with derated gradients) as an aid to predicting severe carotid stenosis.

SUBJECTS AND METHODS

Our study population was composed of 68 patients, yielding 133 carotid bifurcations for analysis. A 2D time-of-flight MR angiography pulse sequence was modified to provide greater sensitivity for carotid stenosis, which resulted in visualization of a carotid stenosis with a 70% or greater diameter as a signal void. Contrast-enhanced MR angiography was performed with the elliptical centric view order. Multiple overlapping thin-slab acquisition (MOTSA) MR angiography was performed in select patients. Digital subtraction angiography was performed in 51 patients, and the findings were used as the gold standard. In the remaining patients, findings on carotid duplex Doppler sonography and at surgery and clinical follow-up were used as the gold standard.

RESULTS

In 51 patients for whom a digital subtraction angiogram was available, we found that the sensitivity of classic 2D time-of-flight MR angiography for prediction of carotid stenosis with a 70% or greater diameter was 94%, and the specificity of the technique was 97%. In three patients with severe carotid stenosis, the stenoses that appeared as signal voids on the classic 2D time-of-flight MR angiography were underestimated on contrast-enhanced MR angiography. Severe stenosis was confirmed by subsequent digital subtraction angiography, surgical results, or both. Discrepancies between findings on MOTSA MR angiography and contrast-enhanced MR angiography were resolved with classic 2D time-of-flight MR angiography. Classic 2D time-of-flight MR angiography increased diagnostic confidence of a severe stenosis in three patients with focal internal carotid artery stenosis.

CONCLUSION

Classic 2D time-of-flight MR angiography has a high sensitivity and specificity for predicting carotid bifurcation stenosis of 70% or greater diameter. These probability measures allowed the detection of three significant stenoses that would have been missed on contrast-enhanced MR angiography and provided greater diagnostic confidence than contrast-enhanced or MOTSA MR angiography alone.

Quand, comment et pourquoi réaliser une imagerie des carotides extracrâniennes ?

The indications for treating carotid artery stenosis are related to the symptomatic nature of the lesion and the degree of stenosis. Duplex sonography is adequate for screening. While some groups believe that Duplex US alone or in combination with transcranial Doppler imaging may be sufficient for presurgical evaluation, it often is recommended to complete the evaluation with either MRA or CTA. Both techniques are advantageous since they allow evaluation of the cervical and intracranial arteries as well as cerebral parenchyma hence providing valuable information prior to definitive management. Catheter angiography remains indicated in patients with multi-vessel disease and ischemic cardiomyopathy, when results at non-invasive evaluation are discordant or in an emergency setting. Duplex US is used for routine follow-up of non-surgical lesions and after endarterectomy. Transcranial Doppler as well as advances in MRA and CTA techniques will be reviewed. Even though the treatment of atherosclerotic carotid artery stenoses remains primarily surgical, specific considerations related to angioplasty will be reviewed. Finally, diseases of the intracranial carotid artery and non-atherosclerotic diseases (dissection...) will also be discussed.

Using a stroke database to develop an optimal vascular imaging protocol for ischemic stroke

OBJECTIVE

There are many combinations of studies for imaging the cervicocranial vasculature for diagnosis of ischemic stroke mechanism. We demonstrate a simple approach for using data from a stroke database to determine an optimal sequence of imaging studies on the basis of cost minimization and diagnostic yield.

METHODS

Our study uses patient data from the Hennepin County Medical Center stroke database, Minneapolis, Minn, to compare two vascular imaging protocols. In protocol 1, carotid ultrasound was the first vascular investigation for clinically determined anterior circulation strokes. Additional imaging with cervical and intracranial magnetic resonance angiography was obtained in nonanterior circulation cases and in cases when carotid ultrasound did not explain the mechanism for anterior circulation events. In protocol 2, cervical and intracranial magnetic resonance angiography was the first vascular investigation irrespective of the presumed topography of the stroke.

RESULTS

The mean cost per patient for imaging workup with protocol 1 was $702. With protocol 2, the cost was $679. Protocol 2 also provided clinically relevant information regarding tandem lesions and variations in intracranial collateral patterns that would have been missed by strictly following protocol 1.

CONCLUSIONS

Our results indicate that, given our hospital costs and patient population, obtaining a cervical and intracranial magnetic resonance angiogram after acute ischemic stroke leads to a lower average cost per patient than obtaining a carotid ultrasound first on presumed anterior circulation events. This result depends on the relative costs of imaging studies and could be different among hospitals serving different patient populations.

Contrast-enhanced MR angiography for carotid disease

Objective: To compare contrast-enhanced MR angiography (CEMRA) with intra-arterial digital subtraction angiography (DSA) for evaluating carotid stenosis.

Methods: A total of 167 consecutive symptomatic patients, scheduled for DSA following screening duplex ultrasound (DUS), were prospectively recruited to have CEMRA. Three independent readers reported on each examination in a blinded and random manner. Agreement was assessed using the Bland-Altman method. Diagnostic and potential clinical impact of CEMRA was evaluated, singly and in combination with DUS.

Results: CEMRA tended to overestimate stenosis by a mean bias ranging from 2.4 to 3.8%. A significant part of the disagreement between CEMRA and DSA was directly caused by interobserver variability. For detection of severe stenosis, CEMRA alone had a sensitivity of 93.0% and specificity of 80.6%, with a diagnostic misclassification rate of 15.0% (n = 30). More importantly, clinical decision-making would, however, have been potentially altered only in 6.0% of cases (n = 12). The combination of concordant DUS and CEMRA reduced diagnostic misclassification rate to 10.1% (n = 19) at the expense of 47 (24.9%) discordant cases needing to proceed to DSA. An intermediate approach of selective DUS review resulted in a marginally worse diagnostic misclassification rate of 11.6% (n = 22) but with only 6.8% of discordant cases (n = 13).

Conclusions: DSA remains the gold standard for carotid imaging. The clinical misclassification rate with CEMRA, however, is acceptably low to support its safe use instead of DSA. The appropriateness of combination strategies depends on institutional choice and cost-effectiveness issues.

Evaluation of carotid stenosis with axial high-resolution black-blood MR imaging

High-resolution axial black-blood MR imaging (BB MRI) has been shown to be able to characterise carotid plaque morphology. The aim of this study was to explore the accuracy of this technique in quantifying the severity of carotid stenosis. A prospective study of 54 patients with symptomatic carotid disease was conducted, comparing BB MRI to the gold standard, conventional digital subtraction X-ray angiography (DSA). The BB MRI sequence was a fast-spin echo acquisition (TE = 42 ms, ETL = 24, field of view = 100 x 100 mm, slice thickness = 3.0 mm) at 1.5 T using a custom-built phased-array coil. Linear measurements of luminal and outer carotid wall diameter were made directly from the axial BB MRI slices by three independent blinded readers and stenosis was calculated according to European Carotid Surgery Trial (ECST) criteria. There was good agreement between BB MRI and DSA (intraclass correlation = 0.83). Inter-observer agreement was good (average kappa = 0.77). BB MRI was accurate for detection of severe stenosis (> or = 80%) with sensitivity and specificity of 87 and 81%, respectively. Eight cases of "DSA-defined" moderate stenosis were overestimated as severe by BB MRI and this may be related to non-circular lumens. Axial imaging with BB MRI could potentially be used to provide useful information about severity of carotid stenosis.

Carotid artery stenosis: grayscale and Doppler ultrasound 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: First, all internal carotid artery (ICA) examinations should be performed with grayscale, color Doppler, and spectral Doppler US. Second, the degree of stenosis determined at grayscale and Doppler US should be stratified into the categories of normal (no stenosis), less than 50% stenosis, 50 to 69% stenosis, > or =70% stenosis to near occlusion, near occlusion, and total occlusion. Third, ICA peak systolic velocity (PSV) and the presence of plaque on grayscale and/or color Doppler images are primarily used in the diagnosis and grading of ICA stenosis. Two additional parameters (the 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. Fourth, ICA should be diagnosed as normal when ICA PSV is less than 125 cm/second and no plaque or intimal thickening is visible, less than 50% stenosis when ICA PSV is less than 125 cm/second and plaque or intimal thickening is visible, 50 to 69% stenosis when ICA PSV is 125 to 230 cm/second and plaque is visible, > or =70% stenosis to near occlusion when ICA PSV is more than 230 cm/second and visible plaque and lumen narrowing are seen, near occlusion when there is a markedly narrowed lumen on color Doppler US, and total occlusion when there is no detectable patent lumen on grayscale US and no flow on spectral, power, and color Doppler US. Fifth, the final report should discuss velocity measurements and grayscale 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 these 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.

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.

Imaging of carotid artery disease: from luminology to function?

There have been tremendous advances in our ability to image atheromatous disease, particularly in the carotid artery, which is accessible and large enough to image. The repertoire of methodology available is growing, giving anatomical information on luminal narrowing which is approaching the level at which conventional carotid angiography will become very uncommon as CT and contrast-enhanced MR angiographic techniques become the norm. More exciting is the tentative ability to perform functional plaque imaging addressing enhancement patterns and macrophage activity using MR or positron-emission tomography techniques. These techniques, once rigorously evaluated, may, in addition to complex mathematical modelling of plaque, eventually allow us to assess true plaque risk. Time will best judge whether we will be able to move from the use of simple luminology to assessment of plaque function.