Ultrasonic tissue characterization with integrated backscatter during inotropic stimulation

Ultrasonic tissue characterization with integrated backscatter is an objective method to quantitatively define the physical state of the myocardium. To determine if backscatter imaging during inotropic stimulation could be used objectively to determine the myocardial viability and ischemia in patients with ischemic heart disease, the backscatter changes were examined in 23 patients with myocardial infarction during dobutamine stress two-dimensional (2-D) echocardiography. Coronary angiography was performed within 1 to 2 days after the stress test. The results of this study demonstrated that changes in backscatter variability correlated significantly with the wall motion changes in stress echocardiography during dobutamine infusion (p < 0.0001). In addition, it was shown that the backscatter changes were significantly different in various types of myocardial tissue. In 23 healthy control segments, the ultrasonic backscatter variability was preserved and unchanged during inotropic stimulation (p = NS). In 15 viable infarct zones, restoration or an increase in backscatter variability during low-dose dobutamine infusion was noted, this being lost when ischemia developing during high-dose dobutamine infusion (p < 0.01). In 9 nonviable infarct zones, the phase-weighted variation was usually ≤ 0 and did not change significantly during inotropic stimulation, regardless of the patency of the infarct-related arteries. In 15 remote ischemic myocardial zones, the backscatter variability was preserved at the baseline level, did not change during low-dose dobutamine infusion, but decreased significantly during high-dose dobutamine stress (p < 0.01). In conclusion, dobutamine stress tissue characterization could offer an objective approach for the detection of myocardial viability and ischemia, and might be a useful adjunct to the conventional stress echocardiography.     

Robustness of integrated backscatter for myocardial tissue characterization

Integrated backscatter (IB) has been used for ultrasonic tissue characterization. To assess the potential variables in IB measurements, we performed both theoretical simulations and in vitro phantom measurements. First, we simulated data in which the scatterer position randomly was varied. IB values for the resulting images were calculated. Second, RF data from a tissue-mimicking phantom were acquired. Third, an adapted imaging approach, based on phase insensitivity, was evaluated. For both the simulations and phantom measurements, IB showed a standard deviation of +/-20%. These large deviations can be explained by variations in interference of signals and are not related to the state of the tissue. Small deviations in position of the scatterers resulted in important variations in IB. They must be taken into account and may limit the use of IB in cardiological applications. An improvement potentially can be obtained using phase insensitivity in new ultrasound processing schemes.     

Mechanisms and outcomes of angioplasty and atherectomy assessed by intravascular ultrasound imaging

Catheter-based intravascular ultrasound is a relatively new imaging tool to examine endovascular structure. One major goal for the development of intravascular ultrasound imaging has been to help clarify the mechanism of interventional therapies such as balloon angioplasty and directional atherectomy. Pathologic studies have suggested that plaque distribution and composition are key features that relate to initial and long-term success of coronary interventions. However, relatively little is known by angiography about the nature of plaque in the clinical setting. Intravascular ultrasound imaging provides a high resolution, “on-line” method of tracking the effects of catheter interventions such as balloon angioplasty and atherectomy. Because of its ability to visualize tissue beneath the luminal surface, ultrasound is generating new insights into the effect of plaque composition and distribution on the response to catheter therapies. With pre-procedure ultrasound imaging, it is increasingly possible to predict the result of a particular intervention, offering the potential for developing strategies of lesion-targeted therapy based on certain plaque characteristics. This article presents the early results of the GUIDE trial as a “works in progress” view of the role of intravascular ultrasound in helping interventionalists to understand—and to optimize—angioplasty and atherectomy. © 1993 John Wiley & Sons, Inc.     

不稳定斑块血管内超声特征的实验研究

目的　明确不稳定斑块的血管内超声 (IVUS)影像学特点。方法　 2 7只雄性新西兰纯种兔随机分成A组 (17只 )与B组 (10只 ) ,A组用球囊损伤腹主动脉 高脂喂养 10周 ,B组仅给予高脂喂养 10周。于 8周末将A组在腹主动脉斑块形成处转染携带人野生型 p5 3基因的重组腺病毒载体 ,于 10周末 ,两组实验兔分别给予中国斑点蝰蛇毒和组胺药物触发斑块破裂。应用IVUS分别测量、比较斑块破裂前的腹主动脉同一血管段中多个病变部位及其参考部位的IVUS指标 ,明确不稳定斑块的IVUS影像学特点。结果　破裂与未破裂斑块的参考部位的血管外弹力膜面积 (EEMA)、管腔面积、斑块面积及管腔面积狭窄率相比 ,差异无显著性意义 (P >0 .0 5 )。与未破裂斑块相比较 ,破裂斑块具有较大的偏心性 (P <0 .0 0 1) ,EEMA、斑块面积及管腔面积狭窄率明显大于前者 ,差异有显著性意义 (均P <0 .0 0 1)。破裂斑块呈现明显的正性重构 ,而稳定斑块主要表现为负性重构。结论　IVUS应用于已建立的动脉粥样硬化不稳定斑块动物模型上 ,能够准确地识别动脉粥样硬化不稳定斑块 ,本研究为临床早期发现不稳定斑块并预测斑块破裂奠定了实验基础。     

背向散射积分超声组织定征对风湿性二尖瓣病变程度判断的对比研究

目的　探讨背向散射积分 (IBS)超声组织定征判断风湿性二尖瓣病变程度的临床应用价值。方法　应用HP SONOS 2 5 0 0LE型超声诊断仪检测 3 2例二尖瓣机械瓣置换术患者和 3 0例正常人二尖瓣IBS及与主动脉后壁 (AOPW )和心包 (PC)标化值 ,以背向散射积分百分比 ( %IBS)表示 ,并与X线照片及病理结果进行对比。结果　异常组二尖瓣前叶瓣尖 (AMV )IBS[( 2 6.1± 6.1)dB]和与AOPW及PC的%IBS[( 91.6± 2 1.5 ) % ,( 68.9± 2 3 .6) % ]均高于正常对照组 [( 14 .7± 3 .9)dB ,( 5 8.6± 18.6) % ,( 3 9.3±10 .7) % ] ;钙化区IBS[( 4 0 .8± 4.5 )dB]和 %IBS[( 15 1.5± 2 8.5 ) % ,( 112 .3± 13 .6) % ]明显高于异常组 (P<0 .0 0 1)。结论　IBS对反映风湿性二尖瓣病变程度有一定的意义 ,尤其对钙化的判断有较高的敏感性。当IBS值 >3 6dB ,%IBS >12 0 % (AMV/AOPW )及 >95 % (AMV/PC)应考虑为瓣叶钙化。其敏感性为96.4% ,92 .9%和 10 0 % ,特异性为 93 .8% ,93 .8%和 90 .6%。     

Evaluation of in-stent neointimal tissue components using integrated backscatter intravascular ultrasound: comparison of drug-eluting stents and bare-metal stents

Although in-stent restenosis (ISR) occurs after drug-eluting stents (DES) implantation, neointimal tissue characteristics have not been fully investigated. We assessed neointimal tissue components using integrated backscatter intravascular ultrasound (IB-IVUS) after DES and bare-metal stents (BMS) implantation. Fifty-seven consecutive patients with 61 lesions underwent repeated percutaneous coronary intervention (PCI) for the treatment of ISR (DES: 24 lesions, BMS: 37 lesions). PCI was performed using plain old balloon angioplasty (POBA). Before PCI, we assessed neointimal tissue characteristics using IB-IVUS. Neointima was divided into four categories: category 1 (-11 to -29?dB), category 2 (-29 to -35?dB), category 3 (-35 to -49?dB), and category 4 (-49 to -130?dB) according to IB values. We compared neointimal tissue components between DES and BMS. Thirty-three patients with 33 lesions (DES: 17, BMS: 16) were finally included. Neointima was predominantly composed of category 3 tissue in both groups (DES: 68?±?8%, BMS: 73?±?5%, P?=?0.053). DES had a broader distribution of category 4 tissue component than BMS. After POBA, distal slow flow phenomenon occurred in 5 of DES (29%), whereas none of BMS. In DES, the optimal threshold of category 4 tissue to predict distal slow flow phenomenon after POBA was 30% (sensitivity: 100%, specificity: 92%). Neointima was mainly composed of category 3 tissue at ISR site, irrespective of DES or BMS. In DES, there was a subgroup with category 4 rich tissue, which caused distal slow flow phenomenon after POBA. IB-IVUS might be useful to identify vulnerable neointima in DES restenosis.     

血管内超声检测易损斑块的研究进展

早期检测易损斑块对于急性冠脉综合征的防治有重要意义。血管内超声是检测易损斑块的重要方法,有着独特优势。本文就血管内超声及其衍生技术检测易损斑块的基本原理和研究进展作一综述。     

Application of neural networks for the analysis of intravascular ultrasound and histological aortic wall appearance-an in vitro tissue characterization study

The role of tissue characterization by intravascular ultrasound (IVUS) imaging of the aortic wall has not been well established. The artificial neural networks (ANNs) are a promising tool for image classification. The aim of the study was to assess the texture correlation between matching IVUS and histologic images of the aortic wall. The computer-based discrimination of pathology within the data sets was also evaluated. In vitro IVUS images and histologic sections from 36 aortic segments were compared using texture parameters that produced the best correlation or the highest discriminative value. The images were classified as normal or abnormal with variable degrees of pathology. Tissue characterization was performed by a nearest neighbor classifier, linear discriminant analysis (LDA) and the ANN-based approach. Good agreement was observed between IVUS and the histologic reference with a correlation coefficient of r = 0.89, r = 0.76 and r = 0.71 for the three most successful texture parameters. The ANN-based approach was the most effective in discriminant analysis, with a correct classification rate of 87.5% for histologic images and 79.2% for IVUS data. The study shows that ANNs are a potentially effective tool for assessment of IVUS aortic images.     

血管内超声组织定征显像的研究现状

一、背景 近年来,动脉粥样硬化导致的心脑血管疾病已成为危害人类健康的"第一杀手",在我国乃至全世界,其患病率和死亡率已居各类疾病之首.研究表明,动脉粥样硬化病变的严重程度与其导致的临床事件之间仅存在弱的相关性,没有临床症状的动脉粥样硬化患者,常常以猝死和急性冠脉综合征(acutecoronary syndrome,ACS)作为首次发病的表现,这些临床事件中的大多数(60%～70%)是因为动脉粥样硬化斑块的破裂、继发血栓形成所致,而发生破裂的斑块往往是非血流限制性的病变,传统的冠状动脉造影检查(coronary angiography,CAG)并不能发现显著的冠脉管腔狭窄,这就是临床上所说的"小斑块、大血栓"事件~([1,2]).     

背向散射积分超声组织定征识别存活心肌的实验

目的探讨背向散射积分检测技术识别存活心肌的敏感性和准确性。方法应用商品化的背向散射积分联机分析处理系统检测活体开胸犬重度缺血、晕厥和梗死心肌模型的标化背向散射积分（ＩＢＳ）、标化背向散射积分周期变异（ＣＶＩＢ）及室壁增厚率。结果重度缺血心肌ＩＢＳ明显增高,ＣＶＩＢ明显减低。再灌注后ＣＶＩＢ的恢复幅度高于室壁增厚率。晕厥心肌的ＩＢＳ和ＣＶＩＢ基本正常,但室壁增厚率明显减低。梗死心肌的ＩＢＳ明显增高,ＣＶＩＢ消失或呈反相,再灌注后无改善。结论背向散射积分超声组织定征能敏感反映不同程度缺血心肌的散射特性变化,为无创判定心肌存活性和评价心肌功能提供了一个新的技术手段     

Myocardial tissue characterization in heart failure by real-time integrated backscatter.

OBJECTIVE: Differentiation between normal and abnormal physical state of the myocardium, not possible with conventional echocardiography, so far could be done with integrated backscatter (IBS) as a research tool only. METHODS: This study investigates myocardial texture analysis with new commercially available real time IBS in 12 normal individuals and in 18 patients with severe left ventricular dysfunction due to coronary artery disease (CAD) in 8 and dilated cardiomyopathy (DCM) in 10 patients. Analysis of IBS amplitude and cyclic variation (dB) in the parasternal long and short axis view of the septum and the posterior wall were measured and corrected with IBS curve of the blood to get absolute values. RESULTS: Compared to normal individuals patients with left ventricular dysfunction had a reduced myocardial cyclic variation (P<0.0001), which correlated to regional systolic wall thickening (r=0.64, P=0.001) and global shortening fraction (r=0.62, P<0.01). Although systolic wall thickening in the posterior wall was lower in CAD patients (% thickening, 11.9+/-10 vs. 21.9+/-8, P=0.004), absolute cyclic variation was reduced in both, CAD and DCM patients in the same order of magnitude. However, the higher maximal IBS amplitude in the posterior wall observed in CAD when compared to DCM patients (13.2+/-4.4 vs. 9.2+/-2.4 dB; P=0.002) indicate fibrosis or scar. The dissociation between cyclic variation and systolic wall thickening could implicate hybernating myocardium. CONCLUSION: Real-time IBS has progressed from research to routine as a tool to obtain additional and valuable information to conventional echocardiography in daily practice.     

Joint learning of ultrasonic backscattering statistical physics and signal confidence primal for characterizing atherosclerotic plaques using intravascular ultrasound

Intravascular Ultrasound (IVUS) is a predominant imaging modality in interventional cardiology. It provides real-time cross-sectional images of arteries and assists clinicians to infer about atherosclerotic plaques composition. These plaques are heterogeneous in nature and constitute fibrous tissue, lipid deposits and calcifications. Each of these tissues backscatter ultrasonic pulses and are associated with a characteristic intensity in B-mode IVUS image. However, clinicians are challenged when colocated heterogeneous tissue backscatter mixed signals appearing as non-unique intensity patterns in B-mode IVUS image. Tissue characterization algorithms have been developed to assist clinicians to identify such heterogeneous tissues and assess plaque vulnerability. In this paper, we propose a novel technique coined as Stochastic Driven Histology (SDH) that is able to provide information about co-located heterogeneous tissues. It employs learning of tissue specific ultrasonic backscattering statistical physics and signal confidence primal from labeled data for predicting heterogeneous tissue composition in plaques. We employ a random forest for the purpose of learning such a primal using sparsely labeled and noisy samples. In clinical deployment, the posterior prediction of different lesions constituting the plaque is estimated. Folded cross-validation experiments have been performed with 53 plaques indicating high concurrence with traditional tissue histology. On the wider horizon, this framework enables learning of tissue-energy interaction statistical physics and can be leveraged for promising clinical applications requiring tissue characterization beyond the application demonstrated in this paper.     

对比血管内超声与磁共振管壁成像评价左冠状动脉斑块负荷

目的 对比分析血管内超声(IVUS)与MR黑血序列冠状动脉管壁成像评价左冠状动脉斑块负荷。 方法 对拟诊为冠心病(CAD)的患者15例,于7天内分别进行IVUS和MR检查。在两种技术所获图像相对应的层面上分别测量血管横截面积、管腔横截面积计算斑块负荷,并行配对t检验、直线相关分析和Bland-Altman分析。 结果 IVUS和MRI评价血管横截面积、管腔横截面积和斑块负荷具有显著相关性,r值分别为0.59、0.68和0.59(P<0.001)。与IVUS比较,MR检查测得的血管横截面积和管腔横截面积较小,斑块负荷计算值较大,差异有统计学意义(P<0.05)。Bland-Altman分析显示IVUS和MR测量冠状动脉斑块负荷均具有较好的重复性。 结论 IVUS和MRI技术均可准确评价冠状动脉病变程度。     

Morphology of coronary artery lesions assessed by virtual histology intravascular ultrasound tissue characterization and fractional flow reserve

Fractional flow reserve (FFR) is an index of the physiological significance of a coronary stenosis. Patients who have lesions with a FFR of >0.80, even optimally treated with medication, have however a MACE rate ranging from 8 to 21%. Coronary plaques at high risk of rupture and clinical events can be also identified by virtual histology intravascular ultrasound (IVUS-VH) as plaques with high amount of necrotic core (NC) abutting the lumen. Aim of this exploratory study was to investigate whether the geometry and composition of lesions with FFR????0.80 were different from their counterparts. Fifty-five consecutive patients in whom FFR was clinically indicated on a moderate angiographic lesion, received also an imaging investigation on the same lesion with IVUS-VH. Data on plaque geometry and composition was analyzed. Patients were subdivided in two groups according to the value of FFR (> or ??0.80). Lesions with a FFR????0.80 (n?=?17) showed a slightly larger plaque burden than those with FFR?>?0.80 (n?=?38) (54.6?±?0.7% vs. 51.7?±?0.7% P?=?0.1). In addition, they tend to have less content of necrotic core than their counterparts (14.2?±?8% vs. 19.2?±?10.2%, P?=?0.08). No difference was found in the distribution of NC-rich plaques (fibroatheroma and thin-capped fibroatheroma) between groups (82% in FFR????0.80 vs. 79% in FFR?>?0.80, P?=?0.5). Although FFR????0.80 lesions have larger plaque size, they do not differ in composition from the ones with FFR?>?0.80. Further exploration in a large prospective study is needed to study whether the lesions with FFR?>?0.80 that are NC rich are the ones associated with the presence of clinical events at follow-up.     

Combined optical coherence tomography and intravascular ultrasound radio frequency data analysis for plaque characterization. Classification accuracy of human coronary plaques in vitro

This study was performed to characterize coronary plaque types by optical coherence tomography (OCT) and intravascular ultrasound (IVUS) radiofrequency (RF) data analysis, and to investigate the possibility of error reduction by combining these techniques. Intracoronary imaging methods have greatly enhanced the diagnostic capabilities for the detection of high-risk atherosclerotic plaques. IVUS RF data analysis and OCT are two techniques focusing on plaque morphology and composition. Regions of interest were selected and imaged with OCT and IVUS in 50 sections, from 14 human coronary arteries, sectioned post-mortem from 14 hearts of patients dying of non-cardiovascular causes. Plaques were classified based on IVUS RF data analysis (VH-IVUS^TM), OCT and the combination of those. Histology was the benchmark. Imaging with both modalities and coregistered histology was successful in 36 sections. OCT correctly classified 24; VH-IVUS 25, and VH-IVUS/OCT combined, 27 out of 36 cross-sections. Systematic misclassifications in OCT were intimal thickening classified as fibroatheroma in 8 cross-sections. Misclassifications in VH-IVUS were mainly fibroatheroma as intimal thickening in 5 cross-sections. Typical image artifacts were found to affect the interpretation of OCT data, misclassifying intimal thickening as fibroatheroma or thin-cap fibroatheroma. Adding VH-IVUS to OCT reduced the error rate in this study.     

超声评价颈动脉斑块稳定性的应用进展

颈动脉斑块的稳定性与脑梗死的发生息息相关。目前,超声是检测颈动脉斑块的有效手段之一。本文就超声评价颈动脉斑块稳定性的应用进展进行综述。     

采用血管内超声弹性成像技术分析动脉粥样硬化斑块负荷与面积应变的关系

目的 采用血管内超声弹性成像技术评价斑块负荷（PB）与面积应变（AS）的关系。方法 对40只雄性纯种新西兰兔全程高脂饲料喂养。第2周末行腹主动脉球囊拉伤术。第12周末行腹主动脉血管内超声检查,对每只动物选择两个等回声斑块,采集不少于3个心动周期的原位血管内超声图像,选择舒张末期连续2帧原位图像,构建血管内超声弹性图。测量并计算血管外弹力膜面积（EEM_area）、血管腔面积（Lumen_area）、斑块面积（PA）、PB、血管外弹力膜体积（EEM_volume）、血管腔体积（Lumen_volume）、斑块体积（PV）、斑块体积负荷（PVB）、斑块最大厚度（T_max）、斑块最小厚度（T_min）、斑块偏心指数（EI）、血管重构指数（RI）及AS。根据PB不同,将斑块分为低负荷斑块组（PB≤40%）和高负荷斑块组（PB>40%）,并对两组间以上参数的差异、斑块形态学和力学参数的关系等进行统计学分析。结果 两组的PA、PV、PB、PVB、T_min、T_max、Lumen_area、Lumen_volume、EI差异均有统计学意义（P均<0.01）。经逐步多元线性回归分析,回归方程为：Ŷ=－6.921+10.430X₁+12.207X₂（Ŷ：AS;X₁：EI;X₂：PB;R²=0.272,P<0.001）。在矫正偏心指数对AS的影响后,低负荷斑块组的AS明显小于高负荷斑块组（P=0.010）。结论 动脉粥样硬化斑块的负荷对斑块力学稳定性有影响。高负荷斑块较低负荷斑块更易受损。     

In-vivo mechanical characterization of coronary atherosclerotic plaques in living swine using intravascular laser speckle imaging

The ability to evaluate the viscoelastic properties of coronary arteries is crucial for identifying mechanically unstable atherosclerotic plaques. Here, we demonstrate for the first time in living swine, the capability of intravascular laser speckle imaging (ILSI) to measure an index of coronary plaque viscoelasticity, τ, using a human coronary to swine xenograft model. Cardiac motion effects are evaluated by comparing the EKG-non-gated τ¯NG, and EKG-gated τ¯G among different plaque types. Results show that both τ¯NG and τ¯G are significantly lower in necrotic-core plaques compared with stable lesions. Discrete-point pullback measurements demonstrate the capability of ILSI for rapid mechanical characterization of coronary segments under physiological conditions, in-vivo.