Carotid artery stenosis: accuracy of noninvasive tests--individual patient data meta-analysis

Correlation of Computed Tomography Angiography to Digital Subtraction Angiography in Carotid Stenosis with Real-World Assessment of Overestimation of Carotid Stenosis on Computed Tomography Angiography

OBJECTIVE

Computed tomography angiography (CTA) is a well-established diagnostic modality for carotid stenosis. However, false-positive CTA results may expose patients to unnecessary procedural complications in cases where surgical intervention is not warranted. We aim to assess the correlation of CTA to digital subtraction angiography (DSA) in carotid stenosis and characterize patients who were referred for intervention based on CTA and did not require it based on DSA.

METHODS

We retrospectively reviewed 186 patients who underwent carotid angioplasty and stenting following preprocedural CTA at our institution from April 2017 to December 2022.

RESULTS

Twenty-one of 186 patients (11.2%) were found to have <50% carotid stenosis on DSA (discordant group). Severe plaque calcification on CTA was associated with a discordant degree of stenosis on DSA (LR+=7.4). Among 186 patients, agreement between the percentage of stenosis from CTA and DSA was weak-moderate (r2=0.27, P<0.01). Among concordant pairs, we found moderate-strong agreement between CTA and DSA (adj r2=0.37) (P < 0.0001). Of 186 patients, 127 patients had CTA stenosis of ≥70%, and 59 had CTA of 50%-69%. Correlation between CTA and DSA in severe CTA stenosis was weak (r2=0.11, P<0.01).

CONCLUSIONS

In patients with stenosis found on CTA, over 88% also had stenosis on DSA, with this positive predictive value in line with previous studies. The percent-stenosis value from CTA and DSA was weakly correlated but does not affect the overall clinical judgement of stenosis. Severe calcification found on CTA may potentially indicate nonstenosis on DSA.

Imaging of Carotid Stenosis: Where Are We Standing? Comparison of Multiparametric Ultrasound, CT Angiography, and MRI Angiography, with Recent Developments

Atherosclerotic disease of the carotid arteries is a crucial risk factor in predicting the likelihood of future stroke events. In addition, emerging studies suggest that carotid stenosis may also be an indicator of plaque load on coronary arteries and thus have a correlation with the risk of acute cardiovascular events. Furthermore, although in symptomatic patients the degree of stenosis is the main morphological parameter studied, recent evidence suggests, especially in asymptomatic patients, that plaque vulnerability should also be evaluated as an emerging and significant imaging parameter. The reference diagnostic methods for the evaluation of carotid stenosis are currently ultrasonography, magnetic resonance imaging (MRI), and computed tomography angiography (CTA). In addition, other more invasive methods such as 123I-metaiodobenzylguanidine (MIBG) scintigraphy and PET-CT, as well as digital subtraction angiography, can be used. Each method has advantages and disadvantages, and there is often some confusion in their use. For example, the usefulness of MRI is often underestimated. In addition, implementations for each method have been developed over the years and are already enabling a significant increase in diagnostic accuracy. The purpose of our study is to make an in-depth analysis of all the methods in use and in particular their role in the diagnostic procedure of carotid stenosis, also discussing new technologies.

Imaging modality-dependent carotid stenosis severity variations against intravascular ultrasound as a reference: Carotid Artery intravasculaR Ultrasound Study (CARUS)

PURPOSE

Different non-invasive and invasive imaging modalities are used to determine carotid artery stenosis severity that remains a principal parameter in clinical decision-making. We compared stenosis degree obtained with different modalities against vascular imaging gold standard, intravascular ultrasound, IVUS.

METHODS

300 consecutive patients (age 47-83 years, 192 men, 64% asymptomatic) with carotid artery stenosis of " ≥ 50%" referred for potential revascularization received as per study protocol (i) duplex ultrasound (DUS), (ii) computed tomography angiography (CTA), (iii) intraarterial quantitative angiography (iQA) and (iv) and (iv) IVUS. Correlation of measurements with IVUS (r), proportion of those concordant (within 10%) and proportion of under/overestimated were calculated along with recipient-operating-characteristics (ROC).

RESULTS

For IVUS area stenosis (AS) and IVUS minimal lumen area (MLA), there was only a moderate correlation with DUS velocities (peak-systolic, PSV; end-diastolic, EDV; r values of 0.42-0.51, p < 0.001 for all). CTA systematically underestimated both reference area and MLA (80.4% and 92.3% cases) but CTA error was lesser for AS (proportion concordant-57.4%; CTA under/overestimation-12.5%/30.1%). iQA diameter stenosis (DS) was found concordant with IVUS in 41.1% measurements (iQA under/overestimation 7.9%/51.0%). By univariate model, PSV (ROC area-under-the-curve, AUC, 0.77, cutoff 2.6 m/s), EDV (AUC 0.72, cutoff 0.71 m/s) and CTA-DS (AUC 0.83, cutoff 59.6%) were predictors of ≥ 50% DS by IVUS (p < 0.001 for all). Best predictor, however, of ≥ 50% DS by IVUS was stenosis severity evaluation by automated contrast column density measurement on iQA (AUC 0.87, cutoff 68%, p < 0.001). Regarding non-invasive techniques, CTA was the only independent diagnostic modality against IVUS on multivariate model (p = 0.008).

CONCLUSION

IVUS validation shows significant imaging modality-dependent variations in carotid stenosis severity determination.

The Effect of PCSK9 Inhibition on the Stabilization of Atherosclerotic Plaque Determined by Biochemical and Diagnostic Imaging Methods

Atherosclerosis is a multifactorial, progressive, chronic inflammatory disease. Ultrasound and magnetic resonance imaging are the most accurate predictors of atherosclerotic plaque instability (MRI). Cytokines such as osteopontin, osteoprotegerin, and metalloproteinase 9 could be used as the most recent markers to identify and track the efficacy of anti-atherosclerotic therapy. Patients with USG and MRI-verified unstable atherosclerotic plaque were included in the study. Biomarker concentrations were measured and compared before and after PCSK9 inhibitor therapy. Additionally, concentrations prior to treatment were correlated with MRI images of the carotid artery. After treatment with alirocumab, the concentrations of MMP-9 (p < 0.01) and OPN, OPG (p < 0.05) decreased significantly. Furthermore, the results of OPN, OPG, and MMP 9 varied significantly depending on the type of atherosclerotic plaque in the MRI assay. In stable atherosclerotic plaques, the concentrations of OPN and OPG were greater (p < 0.01), whereas the concentration of MMP9 correlated with the instability of the plaque (p < 0.05). We demonstrated, probably for the first time, that alirocumab therapy significantly decreased the serum concentration of atherosclerotic plaque markers. In addition, we demonstrated the relationship between the type of atherosclerotic plaque as determined by carotid MRI and the concentration of these markers.

New Technologies in the Assessment of Carotid Stenosis: Beyond the Color-Doppler Ultrasound-High Frame Rate Vector-Flow and 3D Arterial Analysis Ultrasound

Atherosclerotic plaque in the carotid artery is the main cause of ischemic stroke, with a high incidence rate among people over 65 years. A timely and precise diagnosis can help to prevent the ischemic event and decide patient management, such as follow up, medical, or surgical treatment. Presently, diagnostic imaging techniques available include color-Doppler ultrasound, as a first evaluation technique, computed tomography angiography, which, however, uses ionizing radiation, magnetic resonance angiography, still not in widespread use, and cerebral angiography, which is an invasively procedure reserved for therapeutically purposes. Contrast-enhanced ultrasound is carving out an important and emerging role which can significantly improve the diagnostic accuracy of an ultrasound. Modern ultrasound technologies, still not universally utilized, are opening new horizons in the arterial pathologies research field. In this paper, the technical development of various carotid artery stenosis diagnostic imaging modalities and their impact on clinical efficacy is thoroughly reviewed.

Clinical Application of High-Frame-Rate Vector Flow Imaging in Evaluation of Carotid Atherosclerotic Stenosis

OBJECTIVE

This study seeks to evaluate the value of the high-frame-rate vector flow imaging technique in assessing the hemodynamic changes of carotid atherosclerotic stenosis in aging people (>60 years old).

METHODS

Aging patients diagnosed with carotid atherosclerotic stenosis who underwent carotid high-frame-rate vector flow imaging examination were prospectively enrolled. A Mindray Resona7s ultrasound machine equipped with high-frame-rate vector flow function was used for ultrasound evaluation. First, B mode ultrasound and color Doppler flow imaging were used to evaluate carotid stenosis. Then, the vector arrows and flow streamline detected by V Flow were analyzed and the wall shear stress values (Pa) at the carotid stenosis site were measured. All patients were divided into symptomatic and asymptomatic groups according to whether they had acute/subacute stroke or other clinical symptoms within 2 weeks before ultrasound examination. The results of digital subtraction angiography or computed tomography angiography were used as the gold standard. The stenosis rate was calcified, according to North American Symptomatic Carotid Endarterectomy Trial criteria. The diagnostic values of wall shear stress, conventional ultrasound, and the combined diagnosis in carotid atherosclerotic stenosis were compared.

RESULTS

Finally, 88 patients with carotid atherosclerotic plaque were enrolled (71 males (80.7%), mean age 67.6 ± 5.4 years). The success rate of high-frame-rate vector flow imaging was 96.7% (88/91). The WSS value of symptomatic carotid stenosis (1.4 ± 0.15 Pa) was significantly higher than that of asymptomatic carotid stenosis (0.80 ± 0.08 Pa) (p < 0.05). Taking the wall shear stress value > 0.78 Pa as the diagnostic criteria for symptomatic carotid atherosclerotic plaque, the area under receiver operating characteristic curves was 0.79 with 87.1% sensitivity and 69.6% specificity. The area under receiver operating characteristic curves of the combined diagnosis (0.966) for differentiating severe carotid atherosclerotic stenosis was significantly higher than that of conventional ultrasound and WSS value, with 89.7% sensitivity and 93.2% specificity (p < 0.05).

CONCLUSION

As a non-invasive imaging method, the high-frame-rate vector flow imaging technique showed potential value in the preoperative assessment of the symptomatic carotid atherosclerotic stenosis and diagnosing carotid atherosclerotic stenosis in aging patients.

Ultrasonography Grading of Internal Carotid Artery Disease: Multiparametric German Society of Ultrasound in Medicine (DEGUM) versus Society of Radiologists in Ultrasound (SRU) Consensus Criteria

PURPOSE

 We sought to determine the diagnostic agreement between the revised ultrasonography approach by the German Society of Ultrasound in Medicine (DEGUM) and the established Society of Radiologists in Ultrasound (SRU) consensus criteria for the grading of carotid artery disease.

MATERIALS AND METHODS

 Post-hoc analysis of a prospective multicenter study, in which patients underwent ultrasonography and digital subtraction angiography (DSA) of carotid arteries for validation of the DEGUM approach. According to DEGUM and SRU ultrasonography criteria, carotid arteries were independently categorized into clinically relevant NASCET strata (normal, mild [1-49 %], moderate [50-69 %], severe [70-99 %], occlusion). On DSA, carotid artery findings according to NASCET were considered the reference standard.

RESULTS

 We analyzed 158 ultrasonography and DSA carotid artery pairs. There was substantial agreement between both ultrasonography approaches for severe (κw 0.76, CI95 %: 0.66-0.86), but only fair agreement for moderate (κw 0.38, CI95 %: 0.19-0.58) disease categories. Compared with DSA, both ultrasonography approaches were of equal sensitivity (79.7 % versus 79.7 %; p = 1.0) regarding the identification of severe stenosis, yet the DEGUM approach was more specific than the SRU approach (70.2 % versus 56.4 %, p = 0.0002). There was equality of accuracy parameters (p > 0.05) among both ultrasonography approaches for the other ranges of carotid artery disease.

CONCLUSION

 While the sensitivity was equivalent, false-positive identification of severe carotid artery stenosis appears to be more frequent when using the SRU ultrasonography approach than the revised multiparametric DEGUM approach.

Diagnostic accuracy of DSA in carotid artery stenosis: a comparison between stenosis measured on carotid endarterectomy specimens and DSA in 644 cases

BACKGROUND AND PURPOSE

DSA (digital subtraction angiography) is the gold standard for measuring carotid artery stenosis (CS). Yet, the correlation between DSA and stenosis is not well documented.

MATERIAL AND METHODS

We compared CS as measured by DSA to carotid artery specimens obtained from carotid endarterectomy surgery. Patients were divided into three groups according to NASCET criteria (North American Symptomatic Carotid Endarterectomy Trial): stenosis of 30-49% (mild), stenosis of 50-69% (moderate), and stenosis of 70-99% (severe).

RESULTS

This prospective cohort study involved 644 patients. The mean stenosis in the mild stenosis group (n = 128 patients) was 54% ECST (European Carotid Surgery Trial), 40% NASCET, and 72% ESs (endarterectomy specimens). The mean absolute difference between ECST and NASCET was 14%. The mean stenosis in the moderate stenosis group (n = 347 patients) was 66% ECST, 60% NASCET, and 77% ES. The mean absolute difference between ECST and NASCET was 6%. The mean stenosis in the severe group (n = 169 patients) was 80% ECST, 76% NASCET, and 79% ES. No significant correlation coefficients were found between DSA and ES methods. In the mild group, the CC was 0.16 (ESCT) and 0.13 (NASCET); in the moderate group, the CC was 0.05 (ESCT) and 0.01 (NASCET); and in the severe group, the CC was 0.23 (ESCT) and 0.10 (NASCET). For all groups combined, CC was 0.22 for the ECST and 0.20 for the NASCET method.

CONCLUSION

The relationship between DSA and ES methods to measure CS is almost random. This lack of a relationship between the DSA and ES techniques questions the validity of current DSA-based guidelines.

3D-Arterial analysis software and CEUS in the assessment of severity and vulnerability of carotid atherosclerotic plaque: a comparison with CTA and histopathology

Purpose

Our purpose is to assess Multiparametric Ultrasound (MPUS) efficacy for evaluation of carotid plaque vulnerability and carotid stenosis degree in comparison with Computed Tomography angiography (CTA) and histology.

Material and methods

3D-Arterial Analysis is a 3D ultrasound software that automatically provides the degree of carotid stenosis and a colorimetric map of carotid plaque vulnerability.

We enrolled 106 patients who were candidates for carotid endarterectomy. Prior to undergoing surgery, all carotid artery plaques were evaluated with Color-Doppler-US (CDUS), Contrast-Enhanced Ultrasound (CEUS), and 3D Arterial analysis (3DAA) US along with Computerized Tomographic Angiography (CTA) to assess the carotid artery stenosis degree. Post-surgery, the carotid specimens were fixed with 10% neutral buffered formalin solution, embedded in paraffin and used for light microscopic examination to assess plaque vulnerability morphological features.

Results

The results of the CTA examinations revealed 91 patients with severe carotid stenoses with a resultant diagnostic accuracy of 82.3% for CDUS, 94.5% for CEUS, 98.4% for 3DAA, respectively. The histopathological examination showed 71 vulnerable plaques with diagnostic accuracy values of 85.8% for CDUS, 93.4% for CEUS, 90.3% for 3DAA, 92% for CTA, respectively.

Conclusions

The combination of CEUS and 3D Arterial Analysis may provide a powerful new clinical tool to identify and stratify “at-risk” patients with atherosclerotic carotid artery disease, identifying vulnerable plaques. These applications may also help in the postoperative assessment of treatment options to manage cardiovascular risks.

Clinical utility of skin perfusion pressure measurement in diabetic foot wounds: An observational study

The degree of blood vessel stenosis significantly influences diabetic foot treatment. This study aimed to investigate the association between computed tomography angiography (CTA) stenosis and skin perfusion pressure (SPP), which are noninvasive vascular assessments used to evaluate diabetic foot wounds. Forty patients who reported diabetic foot wounds between November 2016 and December 2017 were included in the study. SPPand CTA were performed to evaluate the blood flow, and the rate of decrease in wound size was measured for the wounds corresponding to Meggitt-Wagner grade 1 at the first evaluation and 4-week intervals. The P value of the association between the degree of CTA stenosis and the SPP value was 0.915, and the P value of the association between CTA stenosis and decreasing rate of wound size was .235. There was no statistically significant association between SPP and the decreasing rate of wound size according to the degree of CTA stenosis. The association between SPP value and the decreasing rate of wound size was statistically significant (P < .05). The decreasing rate in diabetic foot wound size was significantly associated with SPP but not with CTA stenosis.

Guideline on carotid surgery for stroke prevention: updates from the Italian Society of Vascular and Endovascular Surgery. A trend towards personalized medicine

BACKGROUND

This guideline (GL) on carotid surgery as updating of "Stroke: Italian guidelines for Prevention and Treatment" of the ISO-SPREAD Italian Stroke Organization-Group, has recently been published in the National Guideline System and shared with the Italian Society of Vascular and Endovascular Surgery (SICVE) and other Scientific Societies and Patient's Association.

METHODS

GRADE-SIGN version, AGREE quality of reporting checklist. Clinical questions formulated according to the PICO model. Recommendations developed based on clinical questions by a multidisciplinary experts' panel and patients' representatives. Systematic reviews performed for each PICO question. Considered judgements filled by assessing the evidence level, direction, and strength of the recommendations.

RESULTS

The panel provided indications and recommendations for appropriate, comprehensive, and individualized management of patients with carotid stenosis. Diagnostic and therapeutic processes of the best medical therapy, carotid endarterectomy (CEA), carotid stenting (CAS) according to the evidences and the judged opinions were included. Symptomatic carotid stenosis in elective and emergency, asymptomatic carotid stenosis, association with ischemic heart disease, preoperative diagnostics, types of anesthesia, monitoring in case of CEA, CEA techniques, comparison between CEA and CAS, post-surgical carotid restenosis, and medical therapy are the main topics, even with analysis of uncertainty areas for risk-benefit assessments in the individual patient (personalized medicine [PM]).

CONCLUSIONS

This GL updates on the main recommendations for the most appropriate diagnostic and medical-surgical management of patients with atherosclerotic carotid artery stenosis to prevent ischemic stroke. This GL also provides useful elements for the application of PM in good clinical practice.

High-Frame Rate Vector Flow Imaging Technique: Initial Application in Evaluating the Hemodynamic Changes of Carotid Stenosis Caused by Atherosclerosis

Objective: To investigate the value of high-frame rate vector flow imaging technique (V flow) in evaluating the hemodynamic changes of carotid stenosis caused by atherosclerotic plaques.

Methods and Materials: In this prospective study, patients with stenosis rate (diameter) ≥30% caused by carotid atherosclerotic plaques were included. Degrees of carotid stenosis were graded according to North American Symptomatic Carotid Endarterectomy Trial criteria: moderate (30–69%) or severe (70–99%). Mindray Resona 7s ultrasound machine with a linear array transducer (3–11 MHz) was used for ultrasound examinations. The mean WSS value of carotid arteries was measured at the proximal, narrowest region and distal of carotid stenosis. The mean WSS values were correlated with peak systolic velocity (PSV) measured by color Doppler flow imaging and stenosis degree detected by digital subtraction angiography (DSA). The vector arrows and flow streamline detected by V flow dynamic imaging were analyzed. Imaging findings of DSA in carotid arteries were used as the gold standard.

Results: Finally, 51 patients were included. V flow measurements were performed successfully in 17 patients (100%) with moderate-grade stenosis and in 30 patients (88.2%) with severe-grade stenosis. Dynamic V flow imaging showed yellow or red vectors at the stenotic segment, indicating fast speed blood flow (up to 260.92 cm/s). Changes of streamlines were detected in the stenotic segment. The mean WSS value measured at the narrowest region of the carotid artery had a moderately positive correlation with stenosis degree (r = 0.58, P < 0.05) and PSV value (r = 0.54, P < 0.05), respectively. Significant difference was detected in mean WSS value at the narrowest region of the carotid artery between severe carotid stenosis (1.47 ± 0.97 Pa) and moderate carotid stenosis (0.96 ± 0.44 Pa) (P < 0.05).

Conclusion: The hemodynamic changes detected by V flow of the carotid stenosis might be a potential non-invasive imaging tool for assessing the degree of carotid stenosis.

Dual Energy Computed Tomography of Internal Carotid Artery: A Modified Dual-Energy Algorithm for Calcified Plaque Removal, Compared With Digital Subtraction Angiography

Background: Atherosclerotic disease of the internal carotid artery (ICA) is a common reason for ischemic stroke. Computed tomography angiography (CTA) is a common tool for evaluation of internal carotid artery (ICA) stenosis. However, blooming artifacts caused by calcified plaques might lead to overestimation of the stenosis grade. Furthermore, the intracranial ICA is more vulnerable to calcification than other ICA segments. The proposed technique, dual-energy computed tomography (DECT) with a modified three-material decomposition algorithm may facilitate the removal of calcified plaques and thus increase diagnostic accuracy.

Objectives: The objective of the study is to assess the accuracy of the modified three-material decomposition algorithm for grading intracranial ICA stenosis after calcified plaque removal, with digital subtraction angiography (DSA) used as a reference standard.

Materials and Methods: In total, 41 patients underwent DECT angiography and DSA. The three-material decomposition DECT algorithm for calcium removal was applied. We evaluated 64 instances of calcified stenosis using conventional CTA, the previous non-modified calcium removal DECT technique, the modified DECT algorithm, and DSA. The correlation coefficient (r²) between the results generated by the modified algorithm and DSA was also calculated.

Results: The virtual non-calcium images (VNCa) produced by the previous non-modified calcium removal algorithm were named VNCa 1, and those produced by the modified algorithm were named VNCa 2. The assigned degree of stenosis of VNCa 1 (mean stenosis: 39.33 ± 19.76%) differed significantly from that of conventional CTA images (mean stenosis: 59.03 ± 25.96%; P = 0.001), DSA (13.19 ± 17.12%, P < 0.001). VNCa 1 also significantly differed from VNCa 2 (mean stenosis: 15.35 ± 18.70%, P < 0.001). In addition, there was a significant difference between the degree of stenosis of VNCa 2 and conventional CTA images (P < 0.001). No significant differences were observed between VNCa 2 and DSA (P = 0.076). The correlation coefficient (r²) between the stenosis degree of the VNCa 2 and DSA images was 0.991.

Conclusions: The proposed DECT with a modified three-material decomposition algorithm for calcium removal has high sensitivity for the detection of relevant stenoses, and its results were more strongly correlated with DSA than with those of conventional CTA or the previous non-modified algorithm. Further, it overcomes CTA's previous problem of overestimating the degree of stenosis because of blooming artifacts caused by calcified plaques. It is useful to account for calcified plaques while evaluating carotid stenosis.

Overestimation of carotid stenosis on CTA - Real world experience

BACKGROUND

Symptomatic carotid stenosis is responsible for 10% of all strokes. Currently, CT angiography (CTA) is the main diagnostic tool for carotid stenosis. It is frequently the only diagnostic test preceding recommendations for carotid angioplasty and stenting (CAS) or carotid endarterectomy (CEA). However, the specificity of CTA, especially in patients with 50-70% stenosis, was previously reported to be relatively low. Most studies testing the diagnostic accuracy of CTA were published more than a decade ago. Therefore, we aimed to test the diagnostic accuracy of CTA, performed with current available technology, compared with digital subtraction angiography (DSA) in patients with carotid stenosis. This study aims to characterize patients who were candidates for CAS/CEA based on CTA, but may not require it based on DSA.

METHODS

Consecutive candidates for carotid interventions (CAS or CEA) following CTA were identified from prospectively maintained stroke center registries at two large academic centers. As part of our institutional practice all patients had a routine pre-procedural diagnostic DSA. In each patient, degree of carotid stenosis was compared between CTA and DSA. Patients with concordant degree of stenosis on DSA and CTA (true positive group) were compared to patients with a discordant degree of stenosis with less than 50% on DSA (false positive group).

RESULTS

Out of 90 patients with significant stenosis on CTA, only 70 (78%) were found to have a significant stenosis on DSA. Severe plaque calcification was significantly more common in the false-positive group. In those patients whose CTA reported stenosis of ≥90%, we found a strong agreement between CTA and DSA (positive predictive value [PPV] - 0.9) for a significant stenosis (≥50%). Conversely, the correlation between CTA and DSA in patients with CTA reported 50-70% stenosis was poor (PPV - 0.29) (p < 0.001).

CONCLUSIONS

Our results suggest that despite ongoing radiological progress, the specificity of CTA in accurately assessing carotid stenosis remains relatively low in patients with both moderate stenosis and heavily calcified plaques. Consequently, patients could possibly be referred for unnecessary CEA surgery and may become exposed to associated potential complications.

CT texture-based radiomics analysis of carotid arteries identifies vulnerable patients: a preliminary outcome study

PURPOSE

To assess the potential role of computed tomography (CT) texture analysis (CTTA) in identifying vulnerable patients with carotid artery atherosclerosis.

METHODS

In this case-control pilot study, 12 patients with carotid atherosclerosis and a subsequent history of transient ischemic attack or stroke were age and sex matched with 12 control cases with asymptomatic carotid atherosclerosis (follow-up time 103.58 ± 9.2 months). CTTA was performed using a commercially available research software package (TexRAD) by an operator blinded to clinical data. CTTA comprised a filtration-histogram technique to extract features at different scales corresponding to spatial scale filter (fine = 2 mm, medium = 3 mm, coarse = 4 mm), followed by quantification using histogram-based statistical parameters: mean, kurtosis, skewness, entropy, standard deviation, and mean value of positive pixels. A single axial slice was selected to best represent the largest cross-section of the carotid bifurcation or the greatest degree of stenosis, in presence of an atherosclerotic plaque, on each side.

RESULTS

CTTA revealed a statistically significant difference in skewness between symptomatic and asymptomatic patients at the medium (0.22 ± 0.35 vs - 0.18 ± 0.39, p < 0.001) and coarse (0.23 ± 0.22 vs 0.03 ± 0.29, p = 0.003) texture scales. At the fine-texture scale, skewness (0.20 ± 0.59 vs - 0.18 ± 0.58, p = 0.009) and standard deviation (366.11 ± 117.19 vs 300.37 ± 82.51, p = 0.03) were significant before correction.

CONCLUSION

Our pilot study highlights the potential of CTTA to identify vulnerable patients in stroke and TIA. CT texture may have the potential to act as a novel risk stratification tool in patients with carotid atherosclerosis.

Multiple reader comparison of 2D TOF, 3D TOF, and CEMRA in screening of the carotid bifurcations: Time to reconsider routine contrast use?

Background and purpose

MR contrast-enhanced techniques are undergoing increased scrutiny since the FDA applied a warning for gadolinium-based MR contrast agents due to gadolinium deposition within multiple organ systems. While CE-MRA provides excellent image quality, is it required in a screening carotid study? This study compares 2D TOF and 3D TOF MRA vs. CE-MRA in defining carotid stenosis in a large clinical patient population, and with multiple readers with varying experience.

Materials and methods

200 consecutive patients had their carotid bifurcations evaluated with 2D TOF, 3D TOF and CE-MRA sequences by 6 board-certified neuroradiologists. Stenosis and quality of examinations were defined for each study. Inter-rater reliability was assessed using two-way random effects intraclass correlation coefficients. Intra-reader reliability was computed via weighted Cohen’s κ. Weighted Cohen’s κ were also computed to assess agreement in stenosis ratings between enhanced images and unenhanced images.

Results

Agreement between unenhanced and enhanced ratings was substantial with a pooled weighted κ of 0.733 (0.628–0.811). For 5 of the 6 readers, the combination of unenhanced 2D TOF and 3D TOF showed better agreement with contrast-enhanced than either 2D TOF or 3D TOF alone. Intra-reader reliability was substantial.

Conclusions

The combination of 2D TOF and 3D TOF MRA showed substantial agreement with CE-MRA regarding degree of carotid stenosis in this large outpatient population across multiple readers of varying experience. Given the scrutiny that GBCA are undergoing due to concerns regarding CNS and soft tissue deposition, it seems prudent to reserve CE-MRA for cases which are not satisfactorily answered by the nonenhanced study or other noninvasive examinations.

Atherosclerosis in intracranial or extracranial vessels in diabetic patients and the association with stroke subtype

Background

Diabetes mellitus (DM) is associated with increased prevalence and severity of atherosclerosis. This study aimed to assess the prevalence and location of atherosclerosis in intracranial and extracranial vessels in diabetic patients and to investigate their association with ischemic stroke subtype.

Methods

Diabetes patients (n=128) and nondiabetic patients (n=195) were enrolled. Brain MRI, MR angiography, and digital subtraction angiography (DSA) imaging findings in the two groups were retrospectively compared. The characteristics of atherosclerosis (prevalence, location, severity) and collateral flow in diabetic and nondiabetic patients and their association with stroke subtype were analyzed.

Results

Atherosclerosis in extracranial vessels was more common in diabetes patients than in nondiabetic patients (43.8% vs. 23.1%; P<0.001). Symptomatic stenoses were commonly in the proximal internal carotid artery (ICA) and proximal vertebral artery (pVA). Diabetes patients were more likely to have lacunar infarction (49.2% vs. 32.3%; P=0.002) and less likely to have large artery infarct (36.7% vs. 48.2%; P=0.042). DM (OR, 2.03; 95% CI, 1.96-4.30; P=0.006) and age >65 years (OR, 2.55; 95% CI, 1.24-5.22; P=0.011) were independent risk factors for lacunar infarct. Diabetes patients with symptomatic extracranial stenosis or occlusion, combined with good collateral circulation, had significantly higher risk of lacunar infarction than nondiabetic patients (47.8% vs. 30.5%; P=0.045).

Conclusions

DM aggravates the severity of extracranial atherosclerosis. Lacunar stroke is relatively common in diabetic patients and could even be due to large artery disease (LAD).

The Growing Field of Imaging of Atherosclerosis in Peripheral Arteries

In the past decades, peripheral arteries have represented a model for the comprehension of atherosclerosis as well as for the development of new diagnostic imaging modalities and therapeutic strategies. Peripheral arteries may represent a window to study atherosclerosis. Pathology has prominently contributed to move the clinical and research attention from the arterial lumen stenosis and angiography to morphological and functional imaging techniques. Evidence from large and prospective cohort or randomized controlled studies is still modest. Nevertheless, several emerging imaging investigations represent a potential tool for a comprehensive "in vivo" evaluation of the entire natural history of peripheral atherosclerosis. This constitutes a demanding assignment, as it would be desirable to obtain both single-lesion focused and extensive arterial system views to achieve the most accurate prognostic information. Our narrative review rests upon the fundamental pathological evidence, summarizing the rapidly growing field of imaging of atherosclerosis in peripheral arteries and presenting a selection of both currently available and emerging imaging techniques.

Carotid Artery Wall Imaging: Perspective and Guidelines from the ASNR Vessel Wall Imaging Study Group and Expert Consensus Recommendations of the American Society of Neuroradiology

Identification of carotid artery atherosclerosis is conventionally based on measurements of luminal stenosis and surface irregularities using in vivo imaging techniques including sonography, CT and MR angiography, and digital subtraction angiography. However, histopathologic studies demonstrate considerable differences between plaques with identical degrees of stenosis and indicate that certain plaque features are associated with increased risk for ischemic events. The ability to look beyond the lumen using highly developed vessel wall imaging methods to identify plaque vulnerable to disruption has prompted an active debate as to whether a paradigm shift is needed to move away from relying on measurements of luminal stenosis for gauging the risk of ischemic injury. Further evaluation in randomized clinical trials will help to better define the exact role of plaque imaging in clinical decision-making. However, current carotid vessel wall imaging techniques can be informative. The goal of this article is to present the perspective of the ASNR Vessel Wall Imaging Study Group as it relates to the current status of arterial wall imaging in carotid artery disease.

Cost-effectiveness of magnetic resonance carotid plaque imaging for primary stroke prevention in Canada

OBJECTIVE

Magnetic resonance of the carotid arteries provides important insight into plaque composition and vulnerability in addition to the traditional measure of stenosis. The purpose of this study was to evaluate the cost-effectiveness of MR imaging as a first-line modality to assess carotid disease and guide management for high-risk patients with <50% stenosis.

METHODS

Using TreeAge Pro, a cost-effectiveness simulation was conducted comparing two strategies: (a) standard of care first-line carotid duplex ultrasound (DUS) with regular follow-up, vs (b) first-line MR assessment of stenosis and intraplaque haemorrhage (MRIPH) in which patients with IPH received annual DUS surveillance and immediate carotid endarterectomy in case of plaque progression.

RESULTS

For patients aged 70 years old, using a first-line MRIPH strategy resulted in a 16.8% relative risk reduction in strokes compared to DUS (0.080 vs 0.097 strokes per patient per lifetime), and an increased quality-adjusted-life years (12.23 vs 12.20) at an increased cost of $897.33 over a patient's lifetime ($5784.53 vs $4887.20 average total cost per patient per lifetime). The incremental cost-effectiveness ratio was $29,744 per quality-adjusted-life years. MRIPH remained cost-effective below a willingness-to-pay threshold of $50,000 for 91.8% of sensitivity analyses.

CONCLUSION

MRIPH was found to be a cost-effective first-line tool to identify asymptomatic patients at high risk for stroke requiring annual surveillance and prompt management. Advances in Knowledge: Using MR imaging as a fist-line method to detect the presence of IPH provides clinically useful and cost-effective information that allows for enhanced risk evaluation and primary stroke prevention.

Functional assessment of the stenotic carotid artery by CFD-based pressure gradient evaluation

The functional assessment of a hemodynamic significant stenosis base on blood pressure variation has been applied for evaluation of the myocardial ischemic event. This functional assessment shows great potential for improving the accuracy of the classification of the severity of carotid stenosis. To explore the value of grading the stenosis using a pressure gradient (PG)-we had reconstructed patient-specific carotid geometries based on MRI images-computational fluid dynamics were performed to analyze the PG in their stenotic arteries. Doppler ultrasound image data and the corresponding MRI image data of 19 patients with carotid stenosis were collected. Based on these, 31 stenotic carotid arterial geometries were reconstructed. A combinatorial boundary condition method was implemented for steady-state computer fluid dynamics simulations. Anatomic parameters, including tortuosity (T), the angle of bifurcation, and the cross-sectional area of the remaining lumen, were collected to investigate the effect on the pressure distribution. The PG is highly correlated with the severe stenosis (r = 0.902), whereas generally, the T and the angle of the bifurcation negatively correlate to the pressure drop of the internal carotid artery stenosis. The calculation required <10 min/case, which made it prepared for the fast diagnosis of the severe stenosis. According to the results, we had proposed a potential threshold value for distinguishing severe stenosis from mild-moderate stenosis (PG = 0.88). In conclusion, the PG could serve as the additional factor for improving the accuracy of grading the severity of the stenosis.

Multi-parametric ultrasound criteria for internal carotid artery disease-comparison with CT angiography

INTRODUCTION

The German Society of Ultrasound in Medicine (known by its acronym DEGUM) recently proposed a novel multi-parametric ultrasound approach for comprehensive and accurate assessment of extracranial internal carotid artery (ICA) steno-occlusive disease. We determined the agreement between duplex ultrasonography (DUS) interpreted by the DEGUM criteria and CT angiography (CTA) for grading of extracranial ICA steno-occlusive disease.

METHODS

Consecutive patients with acute cerebral ischemia underwent DUS and CTA. Internal carotid artery stenosis was graded according to the DEGUM-recommended criteria for DUS. Independent readers manually performed North American Symptomatic Carotid Endarterectomy Trial-type measurements on axial CTA source images. Both modalities were compared using Spearman's correlation and Bland-Altman analyses.

RESULTS

A total of 303 acute cerebral ischemia patients (mean age, 72 ± 12 years; 58 % men; median baseline National Institutes of Health Stroke Scale score, 4 [interquartile range 7]) provided 593 DUS and CTA vessel pairs for comparison. There was a positive correlation between DUS and CTA (r s  = 0.783, p < 0.001) with mean difference in degree of stenosis measurement of 3.57 %. Bland-Altman analysis further revealed widely varying differences (95 % limits of agreement -29.26 to 22.84) between the two modalities.

CONCLUSION

Although the novel DEGUM criteria showed overall good agreement between DUS and CTA across all stenosis ranges, potential for wide incongruence with CTA underscores the need for local laboratory validation to avoid false screening results.

The impact of the National Institute for Health Research Health Technology Assessment programme, 2003-13: a multimethod evaluation

BACKGROUND

The National Institute for Health Research (NIHR) Health Technology Assessment (HTA) programme supports research tailored to the needs of NHS decision-makers, patients and clinicians. This study reviewed the impact of the programme, from 2003 to 2013, on health, clinical practice, health policy, the economy and academia. It also considered how HTA could maintain and increase its impact.

METHODS

Interviews (n = 20): senior stakeholders from academia, policy-making organisations and the HTA programme. Bibliometric analysis: citation analysis of publications arising from HTA programme-funded research. Researchfish survey: electronic survey of all HTA grant holders. Payback case studies (n = 12): in-depth case studies of HTA programme-funded research.

RESULTS

We make the following observations about the impact, and routes to impact, of the HTA programme: it has had an impact on patients, primarily through changes in guidelines, but also directly (e.g. changing clinical practice); it has had an impact on UK health policy, through providing high-quality scientific evidence - its close relationships with the National Institute for Health and Care Excellence (NICE) and the National Screening Committee (NSC) contributed to the observed impact on health policy, although in some instances other organisations may better facilitate impact; HTA research is used outside the UK by other HTA organisations and systematic reviewers - the programme has an impact on HTA practice internationally as a leader in HTA research methods and the funding of HTA research; the work of the programme is of high academic quality - the Health Technology Assessment journal ensures that the vast majority of HTA programme-funded research is published in full, while the HTA programme still encourages publication in other peer-reviewed journals; academics agree that the programme has played an important role in building and retaining HTA research capacity in the UK; the HTA programme has played a role in increasing the focus on effectiveness and cost-effectiveness in medicine - it has also contributed to increasingly positive attitudes towards HTA research both within the research community and the NHS; and the HTA focuses resources on research that is of value to patients and the UK NHS, which would not otherwise be funded (e.g. where there is no commercial incentive to undertake research). The programme should consider the following to maintain and increase its impact: providing targeted support for dissemination, focusing resources when important results are unlikely to be implemented by other stakeholders, particularly when findings challenge vested interests; maintaining close relationships with NICE and the NSC, but also considering other potential users of HTA research; maintaining flexibility and good relationships with researchers, giving particular consideration to the Technology Assessment Report (TAR) programme and the potential for learning between TAR centres; maintaining the academic quality of the work and the focus on NHS need; considering funding research on the short-term costs of the implementation of new health technologies; improving the monitoring and evaluation of whether or not patient and public involvement influences research; improve the transparency of the priority-setting process; and continuing to monitor the impact and value of the programme to inform its future scientific and administrative development.

Timing-Invariant CT Angiography Derived from CT Perfusion Imaging in Acute Stroke: A Diagnostic Performance Study

BACKGROUND AND PURPOSE

Timing-invariant (or delay-insensitive) CT angiography derived from CT perfusion data may obviate a separate cranial CTA in acute stroke, thus enhancing patient safety by reducing total examination time, radiation dose, and volume of contrast material. We assessed the diagnostic accuracy of timing-invariant CTA for detecting intracranial artery occlusion in acute ischemic stroke, to examine whether standard CTA can be omitted.

MATERIALS AND METHODS

Patients with suspected ischemic stroke were prospectively enrolled and underwent CTA and CTP imaging at admission. Timing-invariant CTA was derived from the CTP data. Five neuroradiologic observers assessed all images for the presence and location of intracranial artery occlusion in a blinded and randomized manner. Sensitivity and specificity of timing-invariant CTA and standard CTA were calculated by using an independent expert panel as the reference standard. Interrater agreement was determined by using κ statistics.

RESULTS

We included 108 patients with 47 vessel occlusions. Overall, standard CTA and timing-invariant CTA provided similar high diagnostic accuracy for occlusion detection with a sensitivity of 96% (95% CI, 90%-100%) and a specificity of 100% (99%-100%) for standard CTA and a sensitivity of 98% (95% CI, 94%-100%) and a specificity of 100% (95% CI, 100%-100%) for timing-invariant CTA. For proximal large-vessel occlusions, defined as occlusions of the ICA, basilar artery, and M1, the sensitivity and specificity were 100% (95% CI, 100%-100%) for both techniques. Interrater agreement was good for both techniques (mean κ value, 0.75 and 0.76).

CONCLUSIONS

Timing-invariant CTA derived from CTP data provides diagnostic accuracy similar to that of standard CTA for the detection of artery occlusions in acute stroke.

The Accuracy of Noninvasive Imaging Techniques in Diagnosis of Carotid Plaque Morphology

BACKGROUND

The stroke is leading cause of death and severe disability worldwide. Atherosclerosis is responsible for over 30% of all ischemic strokes. It has been recently discovered that plaque morphology may help predict the clinical behavior of carotid atherosclerosis and determine the risk of stroke. The noninvasive imaging techniques have been developed to evaluate the vascular wall in an attempt to identify "vulnerable plaques".

AIM

The purpose is to investigate the diagnostic accuracy of ultrasound, multidetector computed tomography and magnetic resonance imaging in the identification of plaque components associated with plaque vulnerability.

MATERIAL AND METHODS

One hundred patients were admitted for carotid endarterectomy for high grade carotid stenosis. We defined the diagnostic value of B-mode ultrasound of carotid plaque in a half, and the accuracy of multidetector computed tomography and magnetic resonance imaging, in the other group, for detection of unstable carotid plaque. The reference standard was histology.

RESULTS

Sensitivity of ultrasound, multidetector computed tomography and magnetic resonance imaging is 94%, 83% and 100%, and the specificity is 93%, 73% and 89% for detection of unstable carotid plaque.

CONCLUSION

The ultrasound has high accuracy for diagnostics of carotid plaque morphology, magnetic resonance imaging has high potential for tissue differentiation and multidetector computed tomography determines precisely degree of stenosis and presence of ulceration and calcifications. The three noninvasive imaging modalities are complementary for optimal evaluation of the morphology of carotid plaque. This will help to determine the risk of stroke and to decide on the best treatment - carotid endarterectomy or carotid stenting.

Dual-Source Dual-Energy CT Angiography of the Supra-Aortic Arteries with Tin Filter: Impact of Tube Voltage Selection

RATIONALE AND OBJECTIVES

Automatic bone and plaque subtraction (BPS) in computed tomographic angiographic (CTA) examinations using dual-energy CT (DECT) remains challenging because of beam-hardening artifacts in the shoulder region and close proximity of the internal carotid artery to the base of the skull. The selection of the tube voltage combination in dual-source CT influences the spectral separation and the susceptibility for artifacts. The purpose of this study was to assess which tube voltage combination leads to an optimal image quality of head and neck DECT angiograms after bone subtraction.

MATERIALS AND METHODS

Fifty-one patients received tin-filter-enhanced DECT angiograms of the supra-aortic arteries using two voltage protocols: 24 patients were studied using 80/Sn140 kV and 27 using a 100/Sn140 kV protocol, both protocols with an additional tin filter. A commercially available DE-CTA BPS algorithm was used. Artificial vessel erosions in BPS maximum intensity projections (four-level Likert scale with CTA source data as reference) and vessel signal-to-noise ratio (SNR) were assessed in the level of the shoulders and the base of the skull in each patient and compared.

RESULTS

At the level of the shoulder, 100/Sn140 kV achieved higher SNR (23.4 ± 6.4 at 80/Sn140 kV vs. 35.1 ± 11.8 at 100/Sn140 kV; P < .0001) with less erosions (erosion score 3.9 ± 0.4 in 80/Sn140 kV vs. 2.1 ± 1.3 in 100/Sn140 kV; P < .0001) than 80/Sn140 kV. At the level of the skull base, erosion scores and objective image quality of arterial segments were comparable with both protocols (P = .14).

CONCLUSIONS

The 100/Sn140 kV protocol achieved more favorable results for BPS of the supra-aortic arteries than the 80/Sn140 kV protocol.

An assessment of the cost-effectiveness of magnetic resonance, including diffusion-weighted imaging, in patients with transient ischaemic attack and minor stroke: a systematic review, meta-analysis and economic evaluation

BACKGROUND

Patients with transient ischaemic attack (TIA) or minor stroke need rapid treatment of risk factors to prevent recurrent stroke. ABCD2 score or magnetic resonance diffusion-weighted brain imaging (MR DWI) may help assessment and treatment.

OBJECTIVES

Is MR with DWI cost-effective in stroke prevention compared with computed tomography (CT) brain scanning in all patients, in specific subgroups or as 'one-stop' brain-carotid imaging? What is the current UK availability of services for stroke prevention?

DATA SOURCES

Published literature; stroke registries, audit and randomised clinical trials; national databases; survey of UK clinical and imaging services for stroke; expert opinion.

REVIEW METHODS

Systematic reviews and meta-analyses of published/unpublished data. Decision-analytic model of stroke prevention including on a 20-year time horizon including nine representative imaging scenarios.

RESULTS

The pooled recurrent stroke rate after TIA (53 studies, 30,558 patients) is 5.2% [95% confidence interval (CI) 3.9% to 5.9%] by 7 days, and 6.7% (5.2% to 8.7%) at 90 days. ABCD2 score does not identify patients with key stroke causes or identify mimics: 66% of specialist-diagnosed true TIAs and 35-41% of mimics had an ABCD2 score of ≥ 4; 20% of true TIAs with ABCD2 score of < 4 had key risk factors. MR DWI (45 studies, 9078 patients) showed an acute ischaemic lesion in 34.3% (95% CI 30.5% to 38.4%) of TIA, 69% of minor stroke patients, i.e. two-thirds of TIA patients are DWI negative. TIA mimics (16 studies, 14,542 patients) make up 40-45% of patients attending clinics. UK survey (45% response) showed most secondary prevention started prior to clinic, 85% of primary brain imaging was same-day CT; 51-54% of patients had MR, mostly additional to CT, on average 1 week later; 55% omitted blood-sensitive MR sequences. Compared with 'CT scan all patients' MR was more expensive and no more cost-effective, except for patients presenting at > 1 week after symptoms to diagnose haemorrhage; strategies that triaged patients with low ABCD2 scores for slow investigation or treated DWI-negative patients as non-TIA/minor stroke prevented fewer strokes and increased costs. 'One-stop' CT/MR angiographic-plus-brain imaging was not cost-effective.

LIMITATIONS

Data on sensitivity/specificity of MR in TIA/minor stroke, stroke costs, prognosis of TIA mimics and accuracy of ABCD2 score by non-specialists are sparse or absent; all analysis had substantial heterogeneity.

CONCLUSIONS

Magnetic resonance with DWI is not cost-effective for secondary stroke prevention. MR was most helpful in patients presenting at > 1 week after symptoms if blood-sensitive sequences were used. ABCD2 score is unlikely to facilitate patient triage by non-stroke specialists. Rapid specialist assessment, CT brain scanning and identification of serious underlying stroke causes is the most cost-effective stroke prevention strategy.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Multi-modal CT scanning in the evaluation of cerebrovascular disease patients

Ischemic stroke currently represents one of the leading causes of severe disability and mortality in the Western World. Until now, angiography was the most used imaging technique for the detection of the extra-cranial and intracranial vessel pathology. Currently, however, non-invasive imaging tool like ultrasound (US), magnetic resonance (MR) and computed tomography (CT) have proven capable of offering a detailed analysis of the vascular system. CT in particular represents an advanced system to explore the pathology of carotid arteries and intracranial vessels and also offers tools like CT perfusion (CTP) that provides valuable information of the brain's vascular physiology by increasing the stroke diagnostic. In this review, our purpose is to discuss stroke risk prediction and detection using CT.

Anal sex, vaginal sex and HIV risk among female sex workers in Papua New Guinea

Female sex workers (FSW) are considered one of the key affected populations in Papua New Guinea at risk of acquiring HIV. An integrated bio-behavioral survey of sex workers in Port Moresby was conducted to determine the nature and extent of this risk. About half (51.1 %) of the 411 FSW who reported having any sexual intercourse with clients had engaged in both anal and vaginal intercourse with clients in the last 6 months. In spite of having poorer HIV knowledge (OR95 % CI = 0.14-0.34), FSW who had anal intercourse with clients were significantly more likely to have used a condom at the last vaginal intercourse with a client (OR95 % CI = 1.04-2.87). Similarly, FSW who had anal intercourse with regular and casual partners were significantly more likely to have used a condom at the last vaginal intercourse. Those who engaged in both anal and vaginal intercourse with clients had similar condom use for both vaginal and anal intercourse, with the majority (78.1 %) using a condom at the last occasion for both vaginal and anal intercourse. These FSW may have different risk and protective factors that affect their use of condom during sexual intercourse. Further research is needed to investigate this difference between those who practice anal intercourse and those who do not in order to provide evidence for better programming.

Grading of carotid artery stenosis in the presence of extensive calcifications: dual-energy CT angiography in comparison with contrast-enhanced MR angiography

PURPOSE

We investigated the agreement of dual-energy computed tomography angiography (DE-CTA) and contrast-enhanced magnetic resonance angiography (CE-MRA)in the quantitative measurement of stenoses of the internal carotid artery in comparison with digital subtraction angiography (DSA).

METHODS

A total of 21 patients with stenoses of the external carotid artery were investigated with a DE-CTA and CE-MRA before undergoing carotid angioplasty. The grade of the stenoses was assessed in axial multiplanar reformations (MPR) before and multi-intensity projections (MIP) after plaque subtraction (PS) and compared with results from CE-MRA and DSA according to the North American Symptomatic Carotid Endarterectomy Trial.

RESULTS

Average grades of stenoses were 80.7 ± 16.1 % (DSA), 81.4 ± 15.3 % (MRA), 80.0 ± 16.7 % (DE-CTA-MPR), and 85.2 ± 14.7 % (DE-CTA-PS-MIP). Of 21 stenoses, 6 were filiform (stenosis grade, 99 %) in the DSA examination. Five of these cases were identified as pseudo-occlusions in MRA, while four were considered as occlusions in DE-CTA-PS-MIP. Another four cases were identified as pseudo-occlusion in DE-CTA-PS-MIP, which were identified as 90 % stenosis in the DSA examination.

CONCLUSIONS

In comparison with the gold standard DSA, DE-CTA-MPR had a slightly better agreement in measuring the degree of stenosis of the internal carotid arteries than CE-MRA. In DE-CTA-PS-MIP images, a systematic overestimation has to be taken into account due to partial extinction of the lumen by the PS algorithm. Nevertheless, DE-CTA should be preferred in imaging patients with carotid artery stenosis in the presence of extensive calcifications.

Long-term outcome of vertebral artery origin stenosis in patients with acute ischemic stroke

Background

Vertebral artery origin (VAO) stenosis is occasionally observed in patients who have acute ischemic stroke. We investigated the long-term outcomes and clinical significance of VAO stenosis in patients with acute ischemic stroke.

Methods

We performed a prospective observational study using a single stroke center registry to investigate the risk of recurrent stroke and vascular outcomes in patients with acute ischemic stroke and VAO stenosis. To relate the clinical significance of VAO stenosis to the vascular territory of the index stroke, patients were classified into an asymptomatic VAO stenosis group and a symptomatic VAO stenosis group.

Results

Of the 774 patients who had acute ischemic stroke, 149 (19.3%) of them had more than 50% stenosis of the VAO. During 309 patient-years of follow-up (mean, 2.3 years), there were 7 ischemic strokes, 6 hemorrhagic strokes, and 2 unknown strokes. The annual event rates were 0.97% for posterior circulation ischemic stroke, 4.86% for all stroke, and 6.80% for the composite cardiovascular outcome. The annual event rate for ischemic stroke in the posterior circulation was significantly higher in patients who had symptomatic VAO stenosis than in patients who had asymptomatic stenosis (1.88% vs. 0%, p = 0.046). In a multivariate analysis, the hazard ratio, per one point increase of the Essen Stroke Risk Score (ESRS) for the composite cardiovascular outcome, was 1.46 (95% CI, 1.02-2.08, p = 0.036).

Conclusions

Long-term outcomes of more than 50% stenosis of the VAO in patients with acute ischemic stroke were generally favorable. Additionally, ESRS was a predictor for the composite cardiovascular outcome. Asymptomatic VAO stenosis may not be a specific risk factor for recurrent ischemic stroke in the posterior circulation. However, VAO stenosis may require more clinical attention as a potential source of recurrent stroke when VAO stenosis is observed in patients who have concurrent ischemic stroke in the posterior circulation.

Imaging of the carotid artery vulnerable plaque

Atherosclerosis involving the carotid arteries has a high prevalence in the population worldwide. This condition is significant because accidents of the carotid artery plaque are associated with the development of cerebrovascular events. For this reason, carotid atherosclerotic disease needs to be diagnosed and those determinants that are associated to an increased risk of stroke need to be identified. The degree of stenosis typically has been considered the parameter of choice to determine the therapeutical approach, but several recently published investigations have demonstrated that the degree of luminal stenosis is only an indirect indicator of the atherosclerotic process and that direct assessment of the plaque structure and composition may be key to predict the development of future cerebrovascular ischemic events. The concept of "vulnerable plaque" was born, referring to those plaque's parameters that concur to the instability of the plaque making it more prone to the rupture and distal embolization. The purpose of this review is to describe the imaging characteristics of "vulnerable carotid plaques."

Gadobenate dimeglumine (MultiHance) in MR angiography: an in-vitro phantom comparison with gadopentetate dimeglumine (Magnevist) at different concentrations

BACKGROUND

Numerous clinical studies suggest that gadobenate dimeglumine is diagnostically superior to other gadolinium chelates for MR imaging applications, including contrast-enhanced MR angiography (CE-MRA). However, confirmatory in-vitro phantom studies have thus far been lacking.

PURPOSE

To evaluate the difference in signal intensity achieved with the high-relaxivity MR contrast agent gadobenate dimeglumine (MultiHance) relative to that achieved with the standard-relaxivity non-specific agent gadopentetate dimeglumine (Magnevist) at different concentrations using an in-vitro phantom study design.

MATERIAL AND METHODS

Test tubes with whole human blood were prepared with concentrations of gadobenate dimeglumine or gadopentetate dimeglumine ranging from 0 to 12 mM. A three-dimensional (3D) T1-weighted gradient echo sequence normally used for CE-MRA of the renal arteries was performed at flip angles of 25° and 35°. The signal-to-noise ratio (SNR) was calculated for all concentrations of both contrast agents. Furthermore a Look-Locker sequence was used and quantitative T1 mapping was performed for all the test tubes. The contrast agent concentration in the aorta was simulated using previously published data on T1 in the aorta during the first pass of a contrast agent. The differences between gadobenate dimeglumine and gadopentetate dimeglumine were compared at the simulated concentrations.

RESULTS

The SNR achieved with gadobenate dimeglumine was consistently greater than that achieved with gadopentetate dimeglumine at all concentrations. An improvement of 15-25% in SNR was obtained when increasing the flip angle from 25° to 35°. The relative improvement in SNR with gadobenate dimeglumine relative to gadopentetate dimeglumine ranged from 25-72% and was markedly greater at lower concentrations with a flip angle of 35°.

CONCLUSION

Our findings suggest that the relative benefit of gadobenate dimeglumine over gadopentetate dimeglumine for CE-MRA applications is greater at lower concentrations.

Poor agreement in carotid artery stenosis detection by ultrasound between external offices and a vascular center

BACKGROUND

Carotid duplex ultrasonography is the prime investigation used to grade carotid artery stenosis in clinical routine. We compared the carotid ultrasound (US) scans performed externally with our results.

MATERIALS AND METHODS

This retrospective study included 288 patients who had been referred to our outpatient department and initially presented with an external carotid duplex scan report indicating carotid atherosclerosis. The external scans were analyzed and compared with our scans in respect of the accuracy of identification and quantification of stenosis, the criteria used to grade stenosis and the duplex criteria used. Weighted Kappa coefficients (K) were computed to quantify the agreement between internal and external findings.

RESULTS

The majority of the external reports had been performed by radiologists [70.8 % (n = 204)], followed by specialists of internal medicine [19.4 (n = 56)] and by neurologists [9.8 % (n = 28)]. Only slight agreement was registered between the external reports and those performed at our institution with regard to the identification of stenosis (K = 0.2 for the left and K = 0.12 for the right side). Greater agreement was observed in respect of the level of stenosis (K = 0.42 for the right and K = 0.54 for the left side). Overestimation of the level of stenosis was registered for 45 % in the left internal carotid artery (ICA) and 36 % in the right ICA; the overestimation was most pronounced for occlusions and high-grade stenoses, which is a source of great concern for decision-making.

CONCLUSIONS

The present data indicate only a slight agreement between carotid duplex US imaging performed at medical offices and our results.

Comparison of carotid plaque ulcer detection using contrast-enhanced and time-of-flight MRA techniques

BACKGROUND AND PURPOSE

Ulceration in carotid plaque is a risk indicator for ischemic stroke. Our aim was to compare plaque ulcer detection by standard TOF and CE-MRA techniques and to identify factors that influence its detection.

MATERIALS AND METHODS

Carotid MR imaging scans were acquired on 2066 participants in the ARIC study. We studied the 600 thickest plaques. TOF-MRA, CE-MRA, and black-blood MR images were analyzed together to define ulcer presence (plaque surface niche ≥2 mm in depth). Sixty ulcerated arteries were detected. These arteries were randomly assigned, along with 40 nonulcerated plaques from the remaining 540, for evaluation of ulcer presence by 2 neuroradiologists. Associations between ulcer detection and ulcer characteristics, including orientation, location, and size, were determined and explored by CFD modeling.

RESULTS

One CE-MRA and 3 TOF-MRAs were noninterpretable and excluded. Of 71 ulcers in 56 arteries, readers detected an average of 39 (55%) on both TOF-MRA and CE-MRA, 26.5 (37.5%) only on CE-MRA, and 1 (1.5%) only on TOF-MRA, missing 4.5 (6%) ulcers by both methods. Ulcer detection by TOF-MRA was associated with its orientation (distally pointing versus perpendicular: OR = 5.57 [95% CI, 1.08-28.65]; proximally pointing versus perpendicular: OR = 0.21 [95% CI, 0.14-0.29]); location relative to point of maximum stenosis (distal versus isolevel: OR = 5.17 [95% CI, 2.10-12.70]); and neck-to-depth ratio (OR = 1.96 [95% CI, 1.11-3.45]) after controlling for stenosis and ulcer volume.

CONCLUSIONS

CE-MRA detects more ulcers than TOF-MRA in carotid plaques. Missed ulcers on TOF-MRA are influenced by ulcer orientation, location relative to point of maximum stenosis, and neck-to-depth ratio.

Safety of embolic protection device-assisted and unprotected intravascular ultrasound in evaluating carotid artery atherosclerotic lesions

BACKGROUND

Significant atherosclerotic stenosis of internal carotid artery (ICA) origin is common (5-10% at ≥ 60 years). Intravascular ultrasound (IVUS) enables high-resolution (120 µm) plaque imaging, and IVUS-elucidated features of the coronary plaque were recently shown to be associated with its symptomatic rupture/thrombosis risk. Safety of the significant carotid plaque IVUS imaging in a large unselected population is unknown.

MATERIAL/METHODS

We prospectively evaluated the safety of embolic protection device (EPD)-assisted vs. unprotected ICA-IVUS in a series of consecutive subjects with ≥ 50% ICA stenosis referred for carotid artery stenting (CAS), including 104 asymptomatic (aS) and 187 symptomatic (S) subjects (age 47-83 y, 187 men). EPD use was optional for IVUS, but mandatory for CAS.

RESULTS

Evaluation was performed of 107 ICAs (36.8%) without EPD and 184 with EPD. Lesions imaged under EPD were overall more severe (peak-systolic velocity 2.97 ± 0.08 vs. 2.20 ± 0.08 m/s, end-diastolic velocity 1.0 ± 0.04 vs. 0.7 ± 0.03 m/s, stenosis severity of 85.7 ± 0.5% vs. 77.7 ± 0.6% by catheter angiography; mean ± SEM; p<0.01 for all comparisons) and more frequently S (50.0% vs. 34.6%, p=0.01). No ICA perforation or dissection, and no major stroke or death occurred. There was no IVUS-triggered cerebral embolization. In the procedures of (i) unprotected IVUS and no CAS, (ii) unprotected IVUS followed by CAS (filters - 39, flow reversal/blockade - 3), (iii) EPD-protected (filters - 135, flow reversal/blockade - 48) IVUS + CAS, TIA occurred in 1.5% vs. 4.8% vs. 2.7%, respectively, and minor stroke in 0% vs. 2.4% vs. 2.1%, respectively. EPD intolerance (on-filter ICA spasm or flow reversal/blockade intolerance) occurred in 9/225 (4.0%). IVUS increased the procedure duration by 7.27 ± 0.19 min.

CONCLUSIONS

Carotid IVUS is safe and, for the less severe lesions in particular, it may not require mandatory EPD use. High-risk lesions can be safely evaluated with IVUS under flow reversal/blockade.

Concordance rates of Doppler ultrasound and CT angiography in the grading of carotid artery stenosis: a systematic literature review

Physicians have been increasingly relying on noninvasive imaging methods to grade carotid stenosis. The accuracy of Doppler ultrasound (DUS) and CT angiography (CTA) versus intra-arterial angiography (IA) has been assessed in many studies and at least two meta-analyses. Here, we performed a systematic review of studies that compared DUS to CTA. In a PubMed review of the literature from 2000 to 2009, we found 12 studies that compared DUS and CTA-based grading of carotid stenosis. Only 4 of them included at least 20 patients and provided data to classify the diseased arteries into the following categories: mild, moderate or severe NASCET stenosis or occlusion. We extracted 431 arteries from 244 patients (range per study: 48-164). It was not possible to distinguish symptomatic from asymptomatic stenoses. Nearly half arteries had severe stenosis (46% based on DUS and 43% based on CTA). The weighted kappa was 0.85 (95% CI 0.76-0.94), and the accuracy was 0.78. When the arteries were classified into medical and potentially surgical groups, the kappa was 0.76 (95% CI 0.70-0.83), and the accuracy was 0.89. Overall, 17% of the stenoses classified as medical based on DUS were reclassified as surgical based on CTA and 14% of the stenoses classified as medical based on CTA were reclassified as surgical based on DUS. The sparse available data comparing DUS and CTA suggest that the grading of a carotid stenosis as medical or potentially surgical remains uncertain in a relatively high proportion of patients.

Imaging of the carotid artery

In the study of carotid arteries, modern techniques of imaging allow to analyze various alterations beyond simple luminal narrowing, including the morphology of atherosclerotic plaques, the arterial wall and the surrounding structures. By using CTA and MRI it is possible to obtain three-dimensional rendering of anatomic structures with excellent detail for treatment planning. This paper will detail the role of various imaging methods for the assessment of carotid artery pathology with emphasis on the detection, analysis and characterization of carotid atherosclerosis.

Preprocedural imaging strategies in symptomatic carotid artery stenosis

BACKGROUND

The benefit of carotid endarterectomy (CEA) over best medical therapy was established using intra-arterial angiography (IAA) for patient selection. Its cost, availability, and risk together with the emergence of newer imaging modalities have led to its replacement in the routine assessment of internal carotid artery (ICA) stenosis. The relative performance of these methods should dictate the optimum imaging strategy in symptomatic patients.

METHODS

A previous meta-analysis (NIHR Health Technology Assessment Programme) was reviewed. Medline and PubMed search was performed for relevant publications since 2006 together with a review of the references in retrieved publications.

RESULTS

Compared to IAA, the sensitivity and specificity for noninvasive imaging of a ≥70% to 99% ICA stenosis are duplex ultrasound (DUS): 0.89 (0.85-0.92) and 0.84 (0.77-0.89); time-of-flight magnetic resonance angiography (TOF-MRA): 0.88 (0.82-0.92) and 0.84 (0.76-0.97); contrast-enhanced MRA (CE-MRA): 0.94 (0.88-0.97) and 0.93 (0.89-0.96); and computed tomography angiography: 0.77 (0.68-0.84) and 0.95 (0.91-0.97), respectively. A policy of initial DUS followed by confirmatory CE-MRA best matches patient selection by arteriography. Single modality imaging for 50% to 69% ICA stenoses suggests reduced reliability resulting in more inappropriate operations.

CONCLUSIONS

DUS is the optimum screening tool due to its sensitivity and specificity, availability, and low cost. When CEA appears indicated, confirmatory imaging with CE-MRA is the most reliable and cost-effective method of investigation.

Radiological investigation of acute stroke 2: the multimodal approach

Stroke is an important condition with high mortality and morbidity. Radiology plays a central part in the acute stroke management pathway, with its role now widened beyond establishing the diagnosis. This article reviews radiological techniques beyond the non-enhanced computed tomography brain scan.

Virtual elastic sphere processing enables reproducible quantification of vessel stenosis at CT and MR angiography

PURPOSE

To develop and evaluate a user-friendly tool to enable efficient, accurate, and reproducible quantification of blood vessel stenosis in computed tomographic (CT) and magnetic resonance (MR) angiographic data sets.

MATERIALS AND METHODS

All clinical experiments were approved by the institutional review board, and informed patient consent was acquired. Animal experiments were approved by the governmental review committee on animal care. A virtual elastic sphere passes through a blood vessel specified by user-provided start and end points, and the adapting diameter over the course of the vessel is recorded. The program was tested in phantoms to determine the accuracy of diameter estimation, and it was applied in micro-CT data sets of mice with induced vessel stenosis. Dual-energy CT angiography and MR angiography were performed in 16 patients with carotid artery stenosis, and reproducibility and required reader time of this automated technique were compared with manual measurements. Additionally, the effect of dual-energy CT-based discrimination between iodine- and calcium-based enhancement was investigated. Differences between carotid artery diameters of mice and between automated and manual measurement durations were assessed with a paired t test. Reproducibility of stenosis scores was evaluated with the Fisher z test.

RESULTS

Phantom diameters were determined with an average error of 0.094 mm. Diameters of normal and injured carotid arteries of mice were significantly different (P < .01). For patient data, automated interreader variability was significantly (P < .01) lower than manual intra- and interreader variability, while time efficiency was improved (P < .01).

CONCLUSION

The virtual elastic sphere tool is applicable to CT, dual-energy CT, and MR angiography, and it improves reproducibility and efficiency over that achieved with manual stenosis measurements.

Digital subtraction angiography for the analysis of supra-aortic vessels: What is its role nowadays?

For about 50 years, angiography represented the only imaging method for studying carotid arteries in order to detect the presence of pathological stenosis due to atherosclerotic plaque. Recently, thanks to the use of non-invasive methods, physicians are able to study and quantify the presence of carotid atherosclerosis in vivo. These procedures have enabled the introduction of new concepts: (1) the degree of carotid stenosis is approximate to the volume and extension of carotid plaque; and (2) a set of parameters, easily identifiable by computed tomography angiography, magnetic resonance angiogram and ultra-sound echo-color Doppler, are closely linked to the development of ischemic symptoms and can significantly increase the risk of stroke regardless of the degree of stenosis. In light of these findings, vulnerable plaques should be identified early, and the role of Digital Subtraction Angiography which is a purely technical luminal technique should be determined.

High-resolution MRI of carotid plaque with a neurovascular coil and contrast-enhanced MR angiography: one-stop shopping for the comprehensive assessment of carotid atherosclerosis

OBJECTIVE

The objective of our study was to assess a protocol of study of carotid atherosclerosis coupling vascular wall imaging and luminal imaging in the same examination and to evaluate the accuracy of high-resolution MRI with a neurovascular coil in carotid plaque characterization.

SUBJECTS AND METHODS

Thirty-two consecutive patients with 34 carotid artery stenoses were prospectively enrolled. MRI was performed on a 1.5-T unit. Plaque assessment was performed starting with a diffusion-weighted sequence and followed by a fat-suppressed T1-weighted sequence; after contrast-enhanced MR angiography (CE-MRA), all patients were evaluated with a T1-weighted 3D high-resolution sequence. Carotid plaques were classified as type A, having a large lipid-necrotic core; type B, being a complex fibrotic-calcified plaque with soft content (mixed plaque); or type C, being a fibrotic-calcified plaque (hard). Additional features indicative of vulnerable plaque such as intraplaque hemorrhage (IPH), ulceration, and severe stenosis were registered. MR findings were compared with surgical specimens.

RESULTS

MRI correctly identified 11 of 13 type A, eight of 11 type B, and eight of 10 type C plaques (sensitivity, 84.6%, 72.7%, and 80%, respectively). In the identification of lipid-necrotic core plaque, MRI showed a sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 84.6%, 100%, 100%, and 91.3%, respectively (κ = 0.87). For reordering all plaques in two groups (i.e., soft vs nonsoft) in the identification of soft plaques, MRI had a sensitivity, specificity, PPV, and NPV of 83.3%, 80%, 90.9%, and 66.7%, respectively (κ = 0.59). IPH, ulcers, and severe stenosis were detected in eight of eight, 11 of 13, and 25 of 25 cases, respectively.

CONCLUSION

In patients with carotid atherosclerosis, ongoing CE-MRA with a neurovascular coil for the simultaneous detection of unstable plaques is feasible. Our MR protocol accurately identifies the major features of vulnerable plaque.

Noninvasive imaging of carotid arteries in stroke: emerging value of real-time high-resolution sonography in carotid occlusion due to cardiac embolism

OBJECTIVE

Comprehension of the pathophysiologic characteristics of atherosclerosis has focused its attention on the study of dynamic and metabolic processes involving the vessel wall as possible causes of stroke. When compared with conventional radiologic techniques, sonography has the main advantage of being a real-time imaging modality. We report 2 acute stroke cases in which carotid sonography showed some dynamic features that could not be identified with computed tomography (CT) and magnetic resonance angiography (MRA).

METHODS

Carotid sonography with high-resolution probes (9-14 MHz) was compared with CT and MRA findings showing carotid axis occlusion in 2 patients with acute stroke.

RESULTS

In case 1, the internal carotid artery occlusion observed on CT and MRA was interpreted as a dissection on a clinical basis, but sonography showed a mobile embolus originating from the heart in the internal carotid artery. In case 2, the occlusion of the whole carotid axis observed on CT and MRA was instead related to a heart-originating embolus floating in the common carotid artery.

CONCLUSIONS

The evaluation of dynamic aspects of atherosclerosis is fundamental to understanding the pathophysiologic characteristics of stroke. Sonography is fundamental in carotid artery imaging for its possibility of showing dynamic processes that could be misdiagnosed with "static" imaging. The correct identification of the pathophysiologic characteristics of stroke in these cases could have led to different diagnostic and therapeutic algorithms.