Ultrasound measurements of carotid intima–media thickness by two semi‐automated analysis systems

Increased carotid intima–media thickness (cIMT) is associated with an increased risk of cardiac events and stroke. Several semi‐automated edge‐detection techniques for measuring cIMT are used for research and in clinical practice. Our aim was to compare two currently available semi‐automated techniques for the measurement of cIMT. Carotid ultrasound recordings were obtained from 99 subjects (mean age 54·4 ± 8·9 years, range 33–69) without known cardiovascular diseases using a General Electric (GE) Vivid 7 ultrasound scanner, 8‐MHz transducer. The far‐wall cIMT was evaluated 1–2 cm proximal to the carotid bulb. Three diastolic images (ECG R‐wave) from the left and three images from the right common carotid arteries were analysed using GE and Artery Measurement System (AMS) semi‐automated softwares. Mean systolic and diastolic blood pressures were 120 ± 13 and 76 ± 8 mmHg, respectively. The cIMT_mean (left + right)/2 by GE and cIMT_mean (left + right)/2 AMS were highly correlated (r = 0·92, P<0·001). Higher values were measured by GE (0·72 ± 0·12 mm) compared with AMS (0·69 ± 0·12 mm), and this was significant (P<0·001). The coefficients of variation for the intra‐observer variability of cIMT_mean (left + right)/2 were 1·0% (GE) and 2·2% (AMS). cIMT_mean measured by GE's semi‐automated edge‐detection method correlated well with that measured by AMS. However, there were small but significant systematic differences between the cIMT_mean values measured by the two techniques. Thus, the use of only one type of measurement program seems favourable in follow‐up studies and when evaluating treatment effects.     

Fully Automatic Plaque Segmentation in 3-D Carotid Ultrasound Images

Automatic segmentation of the carotid plaques from ultrasound images has been shown to be an important task for monitoring progression and regression of carotid atherosclerosis. Considering the complex structure and heterogeneity of plaques, a fully automatic segmentation method based on media-adventitia and lumen-intima boundary priors is proposed. This method combines image intensity with structure information in both initialization and a level-set evolution process. Algorithm accuracy was examined on the common carotid artery part of 26 3-D carotid ultrasound images (34 plaques ranging in volume from 2.5 to 456 mm³) by comparing the results of our algorithm with manual segmentations of two experts. Evaluation results indicated that the algorithm yielded total plaque volume (TPV) differences of −5.3 ± 12.7 and −8.5 ± 13.8 mm³ and absolute TPV differences of 9.9 ± 9.5 and 11.8 ± 11.1 mm³. Moreover, high correlation coefficients in generating TPV (0.993 and 0.992) between algorithm results and both sets of manual results were obtained. The automatic method provides a reliable way to segment carotid plaque in 3-D ultrasound images and can be used in clinical practice to estimate plaque measurements for management of carotid atherosclerosis.     

Histopathologic Validation of Grayscale Carotid Plaque Characteristics Related to Plaque Vulnerability

Inflammation and angiogenesis play major roles in carotid plaque vulnerability. The purpose of this study was to determine whether gray-scale features of carotid plaques are associated with histologic markers for inflammation. Thirty-eight individuals completed a dedicated research carotid ultrasound exam before carotid endarterectomy. Gray-scale analysis was performed on plaque images to measure plaque echogenicity (gray-scale median [GSM] pixel brightness), plaque area, presence of discrete white areas (DWAs) and the percent of black area near the lumen on any one component of the plaque. Plaques with higher ultrasound GSM had greater percent calcification (p = 0.013) on histopathology. Presence of an ultrasound DWA was associated with more plaque hemosiderin (p = 0.0005) and inflammation (p = 0.019) on histopathology examination. The percent of plaque black area in any one component was associated with a higher score for macroscopic ulceration (p = 0.028). Ultrasound plaque characteristics (GSM, DWAs and black areas) represent histopathologic markers associated with plaque vulnerability. ClinicalTrials.gov identifier: NCT02476396.     

Deep Learning-Based Carotid Plaque Segmentation from B-Mode Ultrasound Images

Carotid ultrasound measurement of total plaque area (TPA) provides a method for quantifying carotid plaque burden and monitoring changes in carotid atherosclerosis in response to medical treatment. Plaque boundary segmentation is required to generate the TPA measurement; however, training of observers and manual delineation are time consuming. Thus, our objective was to develop an automated plaque segmentation method to generate TPA from longitudinal carotid ultrasound images. In this study, a deep learning-based method, modified U-Net, was used to train the segmentation model and generate TPA measurement. A total of 510 plaques from 144 patients were used in our study, where the Monte Carlo cross-validation was used by randomly splitting the data set into 2/3 and 1/3 for training and testing. Two observers were trained to manually delineate the 510 plaques separately, which were used as the ground-truth references. Two U-Net models (M1 and M2) were trained using the two different ground-truth data sets from the two observers to evaluate the accuracy, variability and sensitivity on the ground-truth data sets used for training our method. The results of the algorithm segmentations of the two models yielded strong agreement with the two manual segmentations with the Pearson correlation coefficient r = 0.989 (p < 0.0001) and r = 0.987 (p < 0.0001). Comparison of the U-Net and manual segmentations resulted in mean TPA differences of 0.05 ± 7.13 mm² (95% confidence interval: 14.02–13.02 mm²) and 0.8 ± 8.7 mm² (17.85–16.25 mm²) for the two models, which are small compared with the TPA range in our data set from 4.7 to 312.8 mm². Furthermore, the mean time to segment a plaque was only 8.3 ± 3.1 ms. The presented deep learning-based method described has sufficient accuracy with a short computation time and exhibits high agreement between the algorithm and manual TPA measurements, suggesting that the method could be used to measure TPA and to monitor the progression and regression of carotid atherosclerosis.     

Repeated visual and computer-assisted carotid plaque characterization in a longitudinal population-based ultrasound study: the Tromsø study

In a longitudinal population-based ultrasound survey, we evaluated the reproducibility of carotid plaque detection, off-line vs. online visual classification of plaque echogenicity and computer-assisted plaque echogenicity (grey-scale median, GSM) classification and plaque area measurements. The number of paired observations in the reproducibility analyses was 107 in the baseline study and 83 in the follow-up study. In addition, 198 and 222 images were selected from the baseline and the follow-up study for GSM- and plaque-area analyses. The total number of plaque images (11,160) was used to obtain comparative reference values. Despite good agreement in the reproducibility study (kappa values ranging from 0.52 to 0.57), there was a substantial drift in online visual classification of plaque echogenicity during the survey period. Inter- and intraobserver agreement on computer-assisted GSM classification was substantial, with kappa values (95% CI) of 0.77 (0.73 to 0.80) and 0.79 (0.75 to 0.84), respectively. A systematic bias in plaque area measurements was observed. Visual online classification may introduce systematic measurement errors that are not intercepted in a reproducibility study of restricted duration. Computer-assisted off-line classification had better reproducibility. However, the method is influenced by measurement errors, both in the outlining of the plaque and in the standardization procedure.     

Carotid plaque: comparison between visual and grey-scale median analysis

Plaque morphology plays an important prognostic role in the occurrence of cerebrovascular events. Echolucent and heterogeneous plaques, in particular, carry an increased risk of subsequent stroke. Most of the trials emphasizing the relationship between plaque echo structure and stroke risk are based on high-resolution ultrasound (US) using a visual method of classification. More recently, several studies have suggested that the computerized measurement of the grey-scale median (GSM) may evaluate carotid plaque echogenicity more objectively and accurately. We sought to compare these two types of evaluations. We studied 68 consecutive patients, with 86 carotid bifurcation plaques causing 30% to 99% stenosis on duplex scanning. We assessed the GSM of these plaques and compared it to the visually evaluated echogenicity using the five-type classification system with vessel lumen and adventitia as reference structures. Plaque heterogeneity was also studied in a subgroup of 47 patients with 60 carotid stenoses by comparing visual analysis with the GSM method. The mean GSM value of the plaques increased with the plaque type. The difference of echogenicity between the five types of plaques was statistically significant (p < 0.02). We found a good concordance between visual analysis and the GSM method regarding plaque heterogeneity. Our results suggest that the visual evaluation of plaque echogenicity and heterogeneity based on the five-type classification correlates well with the computerized measurement of the GSM. The visual evaluation of carotid plaque remains, therefore, a valuable method in daily clinical practice.     

Brachial artery hyperemic blood flow velocities are related to carotid atherosclerosis

Objective: Cardiovascular (CV) risk relates to the blood flow velocity pattern in the brachial artery during hyperemia, especially to the hyperaemic systolic to diastolic mean blood flow velocity (SDFV) ratio. Here, we investigated the relations between SDFV in the brachial artery and different characteristics of carotid atherosclerosis. Material and methods: Data were collected from 1016 70‐year‐olds participating in the Prospective Investigation of Uppsala Seniors study. Doppler recordings of blood flow velocity during hyperemia were analysed in the brachial artery. In the carotid artery, intima‐media thickness (IMT) was recorded together with an assessment of echogenicity by the Grey scale median (GSM) method in both overt plaques and in the intima‐media complex (IM‐GSM). Results: The SDFV ratio was related to the number of carotid arteries affected by plaque (P = 0·018) and inversely to plaque echogenicity (P = 0·0003). The SDFV ratio was also related to IMT (P = 0·0022) and inversely to IM‐GSM (P = 0·0001). These relations were statistically significant also after adjusting for major CV risk factors, individually as well as summarised as the Framingham risk score. Conclusion: Our results indicate that the hyperemic systolic to diastolic blood flow velocity ratio in the brachial artery is related to atherosclerosis in the carotid artery.     

Non-invasive Vascular Radial/Circumferential Strain Imaging and Wall Shear Rate Estimation Using Video Images of Diagnostic Ultrasound

The aim of this work was to develop a convenient method for radial/circumferential strain imaging and shear rate estimation that could be used as a supplement to the current routine screening for carotid atherosclerosis using video images of diagnostic ultrasound. A reflection model-based correction for gray-scale non-uniform distribution was applied to B-mode video images before strain estimation to improve the accuracy of radial/circumferential strain imaging when applied to vessel transverse cross sections. The incremental and cumulative radial/circumferential strain images can then be calculated based on the displacement field between consecutive B-mode images. Finally, the transverse Doppler spectra acquired at different depths along the vessel diameter were used to construct the spatially matched instantaneous wall shear values in a cardiac cycle. Vessel phantom simulation results revealed that the signal-to-noise ratio and contrast-to-noise ratio of the radial and circumferential strain images were increased by 2.8 and 5.9 dB and by 2.3 and 4.4 dB, respectively, after non-uniform correction. Preliminary results for 17 patients indicated that the accuracy of radial/circumferential strain images was improved in the lateral direction after non-uniform correction. The peak-to-peak value of incremental strain and the maximum cumulative strain for calcified plaques are evidently lower than those for other plaque types, and the echolucent plaques had higher values, on average, than the mixed plaques. Moreover, low oscillating wall shear rate values, found near the plaque and stenosis regions, are closely related to plaque formation. In conclusion, the method described can provide additional valuable results as a supplement to the current routine ultrasound examination for carotid atherosclerosis and, therefore, has significant potential as a feasible screening method for atherosclerosis diagnosis in the future.     

The echogenicity of the intima–media complex in the common carotid artery is related to insulin resistance measured by the hyperinsulinemic clamp in elderly men

The echogenicity of the intima–media complex (IM‐GSM) has recently been shown to be related to the echogenicity in carotid artery plaque and to predict cardiovascular (CV) mortality. The present study aims to evaluate the relationship between metabolic CV risk factors, with special emphasis on insulin resistance, and IM‐GSM in the carotid artery. Carotid artery ultrasound with grey‐scale median analysis of the intima–media complex, IM‐GSM, was performed in a population sample of 480 men aged 75 years. In these subjects, a euglycemic hyperinsulinemic clamp to investigate insulin resistance was performed together with measurements of conventional CV risk factors at the age of 70. The metabolic syndrome (MetS) was defined by the NCEP/ATPIII‐criteria. In univariate analysis, IM‐GSM in the common carotid artery was inversely correlated with the intima–media thickness (IMT), body mass index (BMI), waist/hip ratio, fasting glucose, serum triglycerides, low HDL cholesterol and insulin resistance at the clamp (r = ?0·24, P<0·001). In multiple regression analysis, only insulin resistance at the clamp and BMI were independently related to IM‐GSM. Subjects with the MetS (22%) showed a reduced IM‐GSM when compared to those without (64 ± 20 SD versus 68 ± 19, P<0·05). Because the echogenicity of the intima–media complex in the carotid artery is related to obesity and insulin resistance at clamp independently of IMT, this new vascular characteristic would serve as a marker of vascular alterations induced by insulin resistance and the MetS and has the advantage to be obtainable in almost all subjects.     

A Prediction Model for Unstable Carotid Atheromatous Plaque in Acute Ischemic Stroke Patients: Proposal and Internal Validation

The aim of this prospective study was to analyze the utility of a gray-scale median (GSM) system for identifying unstable plaques and to design and validate a prediction model for unstable plaques in symptomatic atheromatous carotid arteries. Fifty-two patients with non-cardioembolic cerebral infarction were included in the study. The receiver operating characteristic analysis revealed 76% sensitivity and 82% specificity for a GSM of 29 (p < 0.001) as a cutoff point for unstable plaques. A logistic regression model indicated that a GSM <29, male gender and not having been treated with angiotensin-converting enzyme inhibitors were independently associated with an unstable plaque classification. A probability model for unstable plaques was achieved by combining the strength of each variable (high blood pressure, hypercholesterolemia, smoking, previous stroke, anti-hypertensive drugs, calcium channel blockers, intima–media thickness). The model was tested with receiver operating characteristic curve analysis (p < 0.001) and validated by the leave-one-out cross-validation method (p < 0.001). The prediction model based on a GSM <29, male gender and not having been treated with angiotensin-converting enzyme inhibitors resulted in a probable unstable plaque assessment.     

Fully Automated Carotid Plaque Segmentation in Combined Contrast-Enhanced and B-Mode Ultrasound

Carotid plaque segmentation in B-mode ultrasound (BMUS) and contrast-enhanced ultrasound (CEUS) is crucial to the assessment of plaque morphology and composition, which are linked to plaque vulnerability. Segmentation in BMUS is challenging because of noise, artifacts and echo-lucent plaques. CEUS allows better delineation of the lumen but contains artifacts and lacks tissue information. We describe a method that exploits the combined information from simultaneously acquired BMUS and CEUS images. Our method consists of non-rigid motion estimation, vessel detection, lumen–intima segmentation and media–adventitia segmentation. The evaluation was performed in training (n = 20 carotids) and test (n = 28) data sets by comparison with manually obtained ground truth. The average root-mean-square errors in the training and test data sets were comparable for media–adventitia (411 ± 224 and 393 ± 239 μm) and for lumen–intima (362 ± 192 and 388 ± 200 μm), and were comparable to inter-observer variability. To the best of our knowledge, this is the first method to perform fully automatic carotid plaque segmentation using combined BMUS and CEUS.     

Automated ultrasound edge‐tracking software comparable to established semi‐automated reference software for carotid intima‐media thickness analysis

Many commercial ultrasound systems are now including automated analysis packages for the determination of carotid intima‐media thickness (cIMT); however, details regarding their algorithms and methodology are not published. Few studies have compared their accuracy and reliability with previously established automated software, and those that have were in asymptomatic adults. Therefore, this study compared cIMT measures from a fully automated ultrasound edge‐tracking software (EchoPAC PC, Version 110.0.2; GE Medical Systems, Horten, Norway) to an established semi‐automated reference software (Artery Measurement System (AMS) II, Version 1.141; Gothenburg, Sweden) in 30 healthy preschool children (ages 3–5 years) and 27 adults with coronary artery disease (CAD; ages 48–81 years). For both groups, Bland–Altman plots revealed good agreement with a negligible mean cIMT difference of ?0·03 mm. Software differences were statistically, but not clinically, significant for preschool images (P = 0·001) and were not significant for CAD images (P = 0·09). Intra‐ and interoperator repeatability was high and comparable between software for preschool images (ICC, 0·90–0·96; CV, 1·3–2·5%), but slightly higher with the automated ultrasound than the semi‐automated reference software for CAD images (ICC, 0·98–0·99; CV, 1·4–2·0% versus ICC, 0·84–0·89; CV, 5·6–6·8%). These findings suggest that the automated ultrasound software produces valid cIMT values in healthy preschool children and adults with CAD. Automated ultrasound software may be useful for ensuring consistency among multisite research initiatives or large cohort studies involving repeated cIMT measures, particularly in adults with documented CAD.     

颈动脉粥样硬化斑块二维超声特征与斑块标本结构一致性的研究

目的探讨颈动脉粥样硬化斑块术前二维超声基本形态及内部回声特征与颈动脉内膜剥脱术（CEA）后斑块大体标本高倍相机影像结构的一致性,以二维超声方法评估斑块易损性的特征。 方法连续纳入2014年1月至2015年5月因颈动脉狭窄70%~99%收入首都医科大学宣武医院行颈动脉内膜剥脱术治疗、术前颈动脉超声纵、横切面动脉粥样硬化斑块成像清晰的患者160例,根据二维超声斑块形态特征分为规则型（32例）与不规则型（128例）,其中溃疡型斑块91例,与CEA术后即刻斑块的外观形态结构进行比较;根据二维超声回声特征分为均质等回声斑块组（64例）、低至无回声斑块组（44例）、不均质强回声斑块组（52例）,分别与CEA术后即刻斑块的纵断解剖切面高倍相机成像显示内部结构特征进行对比。将超声回声均质的斑块（108例）按CEA术后斑块内部结构特征进行分类为均质性非粥样物质（64例）、粥样物质（10例）、新鲜出血（10例）及陈旧性出血坏死（5例）,测量不同性质斑块在二维超声图像上的平均灰阶中值（GSM）并进行比较。 结果160例颈动脉粥样硬化患者超声显示斑块形态与术中标本检查结果：（1）二维超声显示斑块形态与大体标本斑块形态特征的准确率93.1%（149/160）,对不规则斑块诊断的敏感度为95.3%,特异度83.9%;对溃疡性斑块诊断的敏感度84.8%,特异度88.5%,两种类型斑块的总准确率86.2%（138/160）。（2）二维超声回声特征为均质等回声斑块64例,标本内解剖结构显示为结构均匀一致非粥样物质者占95.3%（61/64）;低至无回声斑块44例,标本内结构显示为粥样物质和斑块内新鲜出血占86.3%（38/44）。术中标本显示为非粥样物质成分的斑块GSM值平均为55±19,显著高于粥样物质斑块39±11（P<0.001）和新鲜出血性斑块29±10（P<0.001）,而新鲜出血性斑块平均GSM值低于粥样物质性斑块。（3）不均质强回声斑块52例,二维超声特点为基底部钙化的斑块17例,CEA术中标本为斑块基底部钙化伴内部粥样物质8例,伴陈旧性出血坏死9例;中低回声混杂微小钙化（强回声）特征斑块29例,术中斑块大体标本均呈陈旧性出血与坏死组织相间。 结论二维超声对不规则型与溃疡型斑块的检出准确率高,回声特征的观察与斑块结构特征具有较高的一致性,GSM值的测量能弥补超声医师在二维超声影像上对低灰阶图像识别的困难,可在超声检测中进一步推广应用。     

Conventional treatment after myocardial infarction in routine clinical practice results in regression of left common carotid intima‐media thickness

This study aimed to evaluate the effect of standard medical treatment on the progression of atherosclerosis after a myocardial infarction, in an ordinary clinical setting, by measuring the right and left common carotid intima‐media thickness (IMT). The first investigation took place 3–12 months after the index event; the second took place 3·3–8·2 years after the first. In both investigations, the right and left carotid arteries of 102 patients were examined with an ultrasound duplex scanner. Common carotid IMT and calculated cross‐sectional intima‐media area (cIMa) were measured on both sides. More than 90% of the patients were treated with aspirin, beta‐blockers and statins. In the first investigation, IMT and cIMa were significantly greater on the left side compared to the right (IMT: 0·83 ± 0·22 and 0·74 ± 0·18 mm, P<0·001; cIMa: 18·2 ± 5·2 and 16·3 ± 5·1 mm², P<0·001). In the second investigation, IMT on the left side was significantly reduced compared to the first investigation (0·79 ± 0·22 and 0·83 ± 0·22 mm, P<0·05) with a corresponding tendency towards a decrease in cIMa on the same side. In our study, conventional medical treatment after a myocardial infarction in ordinary clinical routines resulted in regression of the common carotid IMT on the left side. The significant side difference in IMT emphasizes the importance of where and how the carotid IMT is measured in studies using this surrogate end point.     

超声造影结合血清标志物对不稳定斑块及混合斑块的鉴别价值研究王辉,张强,申向辉,尹素芳,侯晓英河北省邯郸市中心医院超声医学科 河北省 邯郸市 056000

目的：探讨超声造影(CEUS)结合血清标志物对于不稳定斑块及混合斑块的鉴别价值研究。方法：选取2018年2月-2020年8月于本院行常规超声检查发现颈动脉粥样硬化斑块的190例患者,术前均行超声造影、血清Lp-PLA2、hs-CRP检测。以病理结果为金标准,根据斑块稳定性分为不稳定斑块(138例)和稳定斑块(52例);根据斑块性质分为软斑块组(138例)、硬斑块组(20例)以及混合斑块组(32例)。比较超声造影、血清Lp-PLA2、hs-CRP水平各组之间的差异。采用准确性、敏感度、特异度、阳性预测值、阴性预测值指标表达超声造影、血清标志物单独或联合诊断不稳定斑块的诊断效能差异。结果：CUES诊断斑块稳定性的差异具有统计学意义(x_²=93.479,P=0.000)。不同性质颈动脉粥样硬化斑块的CUES增强分级不同,当斑块回声越低,其强化越明显,分级也越高,且分布差异具有统计下意义(x_²=21.837,P=0.000)。不稳定斑块组患者血清hs-CRP[(23.17±0.53)mg/L]、Lp-PLA2[(57.36±4.22)ug/L]显著高于稳定斑块组[(16.32±0.56)mg/L]、[(46.73±4.14)ug/L],且差异具有统计学意义(t=0.347、8.432,P=0.000、0.000)。CUES结合血清标志物诊断不稳定斑块的准确性、敏感度、特异度、阳性预测值、阴性预测值最高,且差异具有统计学意义(P<0.05)。结论：超声造影结合血清hs-CRP、Lp-PLA2水平对不稳定斑块及混合斑块具有一定的鉴别诊断价值,有助于早期鉴别不稳定斑块以及混合斑块,进一步指导临床治疗方案的选择。     

How can the variability in ultrasound measurement of intima-media thickness be reduced? Studies of interobserver variability in carotid and femoral arteries

A critical component in scientific studies of most biological variables is the variation or error in measurements which leads to non-identical results of repeated measurements from the same subject. The aim of this study was to investigate whether the interobserver error (s) in measurement of intima-media thickness (IMT) in carotid and femoral arteries could be decreased if the mean value obtained using two ultrasound images from each of the right and left arteries was used in the analyses instead of the mean value obtained using images from only the right artery. In addition, we wished to evaluate two different reading procedures, one based on manual tracing of echo interfaces and the other on automated edge detection. In a methodological study, 50 subjects were examined with ultrasound twice in the same day by two independent laboratory technologists. The ultrasound images were analysed in two ways: using a computerized manual tracing analysing system and an automated analysing system. When both right and left carotid arteries were examined (manual reading), the interobserver error was smaller than that determined for the examination of only the right artery, for IMT_mean in both the common carotid artery (P = 0·06) and the carotid artery bulb (P<0·05). The interobserver error was also significantly smaller for double-sided vs. one-sided examination with automated reading of IMT_mean in the common carotid artery (P<0·01) and in the carotid artery bulb (P<0·01). The coefficient of variation (CV) for measurement in the common carotid artery decreased from 8·6% (one-sided, manual reading) to 5·3% (double-sided, automated reading). The interobserver error in measurement of IMT in the common femoral artery did not improve by examination of both right and left arteries. The results from this study show that the interobserver errors in measurement of IMT can be decreased by using ultrasound images from both the right and the left carotid arteries, and that the use of an automated analysing system greatly simplifies the reading of ultrasound images with sustained low variability.     

Parametric quantification of myocardial ischaemia using real‐time perfusion adenosine stress echocardiography images,with SPECT as reference method

Background: Real‐time perfusion (RTP) adenosine stress echocardiography (ASE) can be used to visually evaluate myocardial ischaemia. The RTP power modulation technique, provides images for off‐line parametric perfusion quantification using Qontrast^® software. From replenishment curves, this generates parametric images of peak signal intensity (A), myocardial blood flow velocity (β) and myocardial blood flow (Axβ) at rest and stress. This may be a tool for objective myocardial ischaemia evaluation. We assessed myocardial ischaemia by RTP‐ASE Qontrast^®‐generated images, using 99mTc‐tetrofosmin single‐photon emission computed tomography (SPECT) as reference. Methods: Sixty‐seven patients admitted to SPECT underwent RTP‐ASE (SONOS 5500) during Sonovue^® infusion, before and throughout adenosine stress, also used for SPECT. Quantitative off‐line analyses of myocardial perfusion by RTP‐ASE Qontrast^®‐generated A, β and Axβ images, at different time points during rest and stress, were blindly compared to SPECT. Results: We analysed 201 coronary territories [corresponding to the left anterior descendent (LAD), left circumflex (LCx) and right coronary (RCA) arteries] from 67 patients. SPECT showed ischaemia in 18 patients. Receiver operator characteristics and kappa values showed that A, β and Axβ image interpretation significantly identified ischaemia in all territories (area under the curve 0·66–0·80, P = 0·001–0·05). Combined A, β and Axβ image interpretation gave the best results and the closest agreement was seen in the LAD territory: 89% accuracy; kappa 0·63; P<0·001. Conclusion: Myocardial isachemia can be evaluated in the LAD territory using RTP‐ASE Qontrast^®‐generated images, especially by combined A, β and Axβ image interpretation. However, the technique needs improvements regarding the LCx and RCA territories.     

Ultrasound Speckle Tracking Strain Estimation of in Vivo Carotid Artery Plaque with in Vitro Sonomicrometry Validation

Our objective was to validate a previously developed speckle tracking (ST) algorithm to assess strain in common carotid artery plaques. Radial and longitudinal strain was measured in common carotid artery gel phantoms with a plaque-mimicking inclusion using an in-house ST algorithm and sonomicrometry. Moreover, plaque strain by ST for seven patients (77 ± 6 y) with carotid atherosclerosis was compared with a quantitative visual assessment by two experienced physicians. In vitro, good correlation existed between ST and sonomicrometry peak strains, both radially (r = 0.96, p < 0.001) and longitudinally (r = 0.75, p < 0.01). In vivo, greater pulse pressure-adjusted radial and longitudinal strains were found in echolucent plaques than in echogenic plaques. This illustrates the feasibility of ultrasound ST strain estimation in plaques and the possibility of characterizing plaques using ST strain in vivo.     

Changes in Carotid Plaque Echogenicity with Time Since the Stroke Onset: An Early Marker of Plaque Remodeling?

Carotid plaques undergo histologic changes early after an ischemic stroke. However, the evolution of carotid plaques echolucency after a recent brain ischemia is not well known. A prospective observational study that included consecutive stroke patients and asymptomatic individuals with plaques showing ≥50% stenosis on duplex ultrasound was conducted. Plaque echogenicity was measured with the standardized gray-scale median (GSM) and compared with respect to symptoms presence and time from stroke onset. One hundred twenty-six carotid plaques in 124 patients were studied and four groups of plaques were analyzed: (1) plaques seen within 24 h of stroke onset (32); (2) between 1–7 days (50); (3) more than 7 days after stroke onset (22) and; (4) plaques without associated symptoms (22). Plaques of group 1 had less echogenicity than those of groups 2–4: median GSM (interquartile range) 14 (16), 19.5 (19), 22.5 (21), 26.5 (16) respectively (p = 0.001). In conclusion, carotid plaque echogenicity is increased with time from stroke onset and could be an early marker of plaque remodeling.     

Non-Invasive Identification of Vulnerable Atherosclerotic Plaques Using Texture Analysis in Ultrasound Carotid Elastography: An In Vivo Feasibility Study Validated by Magnetic Resonance Imaging

The aims of this study were to quantify the textural information of strain rate images in ultrasound carotid elastography and evaluate the feasibility of using the textural features in discriminating stable and vulnerable plaques with magnetic resonance imaging as an in vivo reference. Ultrasound radiofrequency data were acquired in 80 carotid plaques from 52 patients, mainly in the longitudinal imaging view, and axial strain rate images were estimated with an ultrasound carotid elastography technique based on an optical flow algorithm. Four textural features of strain rate images—contrast, homogeneity, correlation and angular second moment—were derived based on the gray-level co-occurrence matrix in plaque regions to quantify the deformation distribution pattern. Conventional elastographic indices based on the magnitude of the absolute strain rate, such as the maximum, mean, median, standard deviation and 99th percentile of the axial strain rate, were also obtained for comparison. Composition measurement with magnetic resonance imaging identified 30 plaques as vulnerable and the other 50 as stable. The four textural features, as well as the magnitude of strain rate images, significantly differed between the two groups of plaques. The best performing features for plaque classification were found to be the contrast and 99th percentile of the absolute strain rate, with a comparative area under the receiver operating characteristic curve of 0.81; a slightly higher maximum accuracy of plaque classification can be achieved by the textural feature of contrast (83.8% vs. 81.3%). The results indicate that the use of texture analysis in plaque classification is feasible and that larger local deformations and higher level of complexity in deformation patterns (associated with the elastic or stiffness heterogeneity of plaque tissues) are more likely to occur in vulnerable plaques.