超声背向散射技术诊断心脏疾病的临床研究

心肌超声组织定征 (myocardialultrasonictissuecharacterization ,MUTC)是近年来发展较快的无创性评价心肌内在声学物理特征的方法 ,它通过探讨心肌组织声学特性与超声表现之间的相互关系 ,寻求能有效反映心肌状态的声学参数 ,以其作为区别不同组织及鉴别病变性质的依据。临床常用的方法有 :视频法 (声像度回声强度分析法 )和射频法 (超声背向散射积分分析法 )。理论上射频法较视频法更客观、准确 ,在近年来的心脏疾病诊断的临床研究中应用较为广泛。1　超声背向散射 (IntegratedBackscatter,IB)技术的基本原理声波入射人体组织时 ,组…     

老年高血压心肌背向散射成像声学密度定量的临床应用

目的　应用声学密度定量 (AD)方法对老年高血压病人心肌超声背向散射成像 (IBS)进行分析 ,探讨其临床诊断应用价值及意义。方法　按 1 999年 WHO高血压治疗标准并应用超声心动图仪检测 64例老年男性住院病人 ,其中正常组 31例 ,高血压组 33例 (高血压病史均 >3年且治疗时间均 >1年 ) ,比较各组室间隔心肌 IBS的 AD诸参数。结果　 Loop和两种触发方式声学密度曲线的峰值密度 (pi)、曲线下面积 (auc)高血压组均高于正常组 (均 P<0 .0 5)。结论　长期高血压和衰老致心肌组织纤维化进一步加重 ,致声学密度参数显著改变 ,其可作为简单、有效且无创的研究心肌病理学方面改变的辅助检测方法     

肥厚型心肌病与高血压性心脏病心肌超声组织定征的鉴别诊断

目的探讨肥厚型心肌病、高血压病患者与正常人左室后壁、室间隔心肌声学特性是否存在差异,以期将超声组织定征作为鉴别诊断的指标之一. 方法将被检者分成3组肥厚型心肌病组(HCM组)、高血压性心脏病组(EH组)及正常对照组,分别测定各组左室后壁、室间隔部位的心肌背向散射参数.结果左室后壁心肌HCM组与EH组的IBS、CVIB无显著性差异(P>0.05),而与正常对照组均有差异(P<0.05);室间隔部位3组IBS、CVIB均有显著性差异(P<0.05);HCM组室间隔、左室后壁均存在IBS、CVIB的跨壁梯度,而EH组、正常对照组则无上述异常存在.结论 HCM患者左室后壁心肌的声学特性与正常对照组有差异,室间隔与左室后壁均存在IBS、CVIB的跨壁梯度.因此背向散射参数测定可作为鉴别肥厚型心肌病和高血压性心脏病的一项指标.     

声学密度定量评价老年肾功能不全的心肌改变

目的　探讨声学密度定量技术对老年慢性肾功能不全病人心肌改变的临床应用价值。方法　正常组 32例 ,慢性肾功能不全组 38例 ,分别进行超声背向散射积分 (IBS)、二次谐波 (SHI)和声学密度定量 (AD)检查。结果　 Loop方法显示 :正常组与异常组的左室前壁心肌声学密度曲线整体水平高于正常者 ;两种触发方式 IBS和 SHI曲线 :峰值和曲线下面积收缩期整体略高于舒张期 ,异常组均较正常组峰值和曲线下面积显著增高 (Ppd<0 .0 5,Pacu<0 .0 5)。结论　老年慢性肾功能不全病人心肌病理学改变的声学密度定量心肌超声组织定征是一种识别力高、相对无创、诊断有效而可靠的检测手段 ,降低了人为差异。     

超声心肌声学造影对存活心肌的评价及临床意义

超声心肌声学造影为一种诊断心肌组织水平灌注的新型超声技术,可从微循环完整性的角度评价存活心肌。存活心肌的识别对冠状动脉粥样硬化性心脏病患者选择积极、合理的治疗方案、评估疗效及预后有重要临床价值。本文就该技术对存活心肌的评价及临床意义作一综述。     

背向散射积分技术在心肌缺血诊断中的应用

背向散射积分 (Integratedbackscatter,IBS)技术是近年发展起来的新型无创性超声组织定征技术 ,它结合计算机自动处理、分析二维图像中取样容积内背向散射信号的强度大小 ,而定量评价组织器官的结构特性与功能状态。相对于二维及M型超声 ,IBS技术能更客观、定量地评价心肌组织结构特征 ,目前国内外在心脏方面的相关研究报道较多 ,本文拟就IBS技术在心肌缺血诊断中的应用作一概述。1 　 背向散射及IBS的定义当超声界面直径小于入射超声波波长的 1 / 2时 ,就可引起声散射 ,其中朝向探头方向的散射波叫后散射波 ,即背向散射。将背向散射…     

脑梗塞患者颈动脉斑块分布及超声背向散射积分分析

目的:定量分析脑梗塞患者的颈动脉斑块分布及其声学组织定征特点,探讨预测脑梗塞发生的超声提示性诊断指标。方法:对76例经CT或MRI诊断的单一血管供血区梗塞的脑梗塞患者和60例健康对照受检者进行对比研究, 观察颈动脉斑块分布、回声性质、背向散射积分(IBS)值、斑块引起狭窄动脉病例数。结果:脑梗塞组颈动脉狭窄病例数显著增多(P<0．01)。脑梗塞组颈动脉斑块混合回声、弱回声、低回声、强回声的发生率分别为45％、36％、 10％、9％,与对照组的发生率15％、8％、26％、51％相比,差别均显著(P<0．01)。强回声IBS值(42．60± 5．76)dB;低回声IBS值(33．01±4．51)dB,弱回声IBS值(28．13±4．46)dB,两两比较P均<0．01。结论:超声组织定征技术能够定量分析颈动脉斑块的组织成分,对脑梗塞发生有提示性诊断作用。     

超声二次谐波心肌声学造影评价心肌的血流灌注

目的探讨心肌声学造影对冠状动脉(冠脉)病变的诊断价值。 方法静脉注射声学造影剂利声显(levovist),通过超声二次谐波技术获取心肌灌注图像,对比冠脉造影显示的冠脉支配区域的心肌灌注与超声心肌声学造影获取的心肌灌注类型的关系。按心肌灌注积分指数将异常冠脉分为3组,心肌灌注积分指数1分(A组,27支),2分≥心肌灌注积分指数＞1分(B组,24支),＞2分(C组,33支)。 结果心肌灌注积分指数与冠脉狭窄度呈中度正相关(r＝0.75,P＜0.001),3组病人的冠脉狭窄程度、心肌灌注积分指数明显差异(P＜0.001)。冠脉狭窄度＜75%者,病人室壁灌注多为正常,随着冠脉狭窄程度加重,室壁灌注出现异常。 结论静脉心肌声学造影是反映心肌灌注的有效方法,能够反应冠脉血流的改变及微循环结构的完整性变化,从而弥补了冠脉造影仅能显示心外膜下的冠脉而无法观察毛细血管水平心肌灌注的缺限。     

心绞痛患者心肌组织微循环灌注与冠状动脉内皮损伤的相关性及临床意义

目的探讨冠状动脉内皮损伤与心肌组织微循环灌注状况的相关性及其临床意义。方法 30例心绞痛患者均经冠状动脉造影证实有明显冠状动脉狭窄,18例对照组患者经临床检查和选择性冠状动脉造影排除冠心病。在介入手术中采集冠状窦血液标本,测定一氧化氮(NO)、内皮素(ET)含量和循环内皮细胞(CEC)数量,以此反映冠状动脉内皮损伤情况。冠状动脉造影后超声声学造影剂由冠状动脉直接注入,完成超声心肌声学造影。采用视觉评分法对心肌灌注进行定性分析,并由心肌灌注时间-强度曲线得到以下参数进行定量分析:造影剂峰值密度、达峰时间及曲线下面积,分别反映心肌血容量、灌注速度及心肌血流量。结果心绞痛患者尤其是不稳定型心绞痛患者冠状窦血中NO浓度明显降低,ET浓度和CEC数量均明显增高(P0.01,或P0.05),NO浓度与心肌组织微循环灌注水平呈显著正相关,ET浓度和CEC数量与之呈显著负相关。结论冠状动脉内皮损伤与心肌组织微循环灌注水平密切相关,心肌组织微循环灌注水平的高低结合实验室检查冠状动脉内皮损伤程度,有助于更确切地评估冠脉病变的程度和判断冠心病患者的预后。     

超声心动图热点探讨

超声心动图技术发展迅速,热点甚多,本文拟就如何进一步发掘M型超声的潜力、深化心肌灌注声学造影研究、心脏介入超声在临床治疗中的作用、心肌组织动态超声显示新技术、心腔内超声成像的应用和实时三维超声心动图的发展前景等问题进行探讨。     

Ultrasonic tissue characterization of normal and ischemic myocardium

Cardiac ultrasonic tissue characterization is designed to use the alterations in acoustic signals from the myocardium to differentiate normal from ischemic or infarcted tissue due to their characteristic backscatter attenuation. Various approaches such as use of a gray scale, color display, or quantitative image analysis have been used for tissue characterization, but all depend on subjective assessments and are not necessarily reproducible. The most promising method has been the use of "raw" radiofrequency signals and measure changes in the ultrasonic attenuation with an index of backscatter to distinguish normal from abnormal myocardium called "integrated backscatter" (IB). Various studies have demonstrated the changes in the ultrasonic backscatter with ischemia or infarction. In this review we summarize our experience with a research prototype instrument in tissue characterization and differentiation of normal, ischemic, infarcted, and post ischemic reperfused myocardium in anesthetized open chest dogs. Currently we are investigating the role of ultrasonic tissue characterization to estimate infarct size and plan to apply these observations to patients in order to detect viable myocardium and quantitate infarct size.     

Integrated backscatter for the assessment of myocardial viability

PURPOSE OF REVIEW: Ultrasonic tissue characterization is a non-invasive diagnostic method that uses myocardial integrated backscatter analysis to determine contractile performance and myocardial viability independent of wall motion. This review discusses recent clinical findings regarding the application of ultrasonic tissue characterization for the assessment of myocardial viability. RECENT FINDINGS: As this technique is non-invasive, ultrasonic tissue characterization can be used to predict the patency of infarct-related arteries in patients in the early stage of acute myocardial infarction. Several recent studies have shown that this technique is useful in identifying myocardial contractile reserve. The accuracy of ultrasonic tissue characterization for predicting functional recovery after coronary reperfusion is comparable to dobutamine echocardiography and radionuclide methods. Several studies have suggested that the cyclic variation of myocardial integrated backscatter reflects myocardial viability rather than contractile reserve. The cyclic variation of integrated backscatter is associated with myocardial viability confirmed by the integrity of the microvasculature identified by contrast echocardiography. In addition, the cyclic variation of integrated backscatter better reflects myocardial viability confirmed by the integrity of cellar metabolism than contractile reserve. SUMMARY: Ultrasonic tissue characterization with integrated backscatter is a useful non-invasive method that can provide unique information for the assessment of myocardial viability.     

Estimation of myocardial infarct size with ultrasonic tissue characterization

BACKGROUND. Ultrasonic tissue characterization (UTC) can distinguish normal from infarcted myocardium. Infarcted myocardium shows an increase in integrated backscatter and loss of cardiac cycle-dependent variation in backscatter. The cyclic variation of backscatter is closely related to regional myocardial contractile function; the latter is a marker of myocardial ischemia. The present study was designed to test the hypothesis that intramural cyclic variation of backscatter can map and estimate infarct size. METHODS AND RESULTS. Transmural myocardial infarction was produced in 12 anesthetized, open-chest dogs by total occlusion of the left anterior descending coronary artery for 4 hours. A real-time ultrasonic tissue characterization instrument, which graphically displays integrated backscatter Rayleigh 5, cardiac cycle-dependent variation, and patterns of cyclic variation in backscatter, was used to map infarct size and area at risk of infarction. Staining with 2,3,4-triphenyltetrazolium chloride (TTC) and Patent Blue Dye was used to estimate infarct size and the area at risk, respectively. The ratio of infarct size to area at risk of infarction determined with UTC correlated well with that determined with TCC (r = 0.862, y = 23.7 +/- 0.792x). Correlation coefficients for infarct size and area at risk were also good (r = 0.736, y = 12.3 +/- 737x for infarct size and r = 0.714, y = 5.80 +/- 1.012x for area at risk). However, UTC underestimated both infarct size and area at risk. CONCLUSIONS. Ultrasonic tissue characterization may provide a reliable, noninvasive method to estimate myocardial infarct size.     

Ultrasonic characterization of porcine liver tissue at frequency between 25 to 55 MHz

AIM: To study the relation between acoustic parameters and histological structure of biological tissue and to provide the basis for high-resolution image of biological tissues and quantitative ultrasonic diagnosis of liver disease. METHODS: Ultrasonic imaging and tissue characterization of four normal porcine liver and five cirrhotic liver tissue samples were performed using a high frequency imaging system. RESULTS: The acoustic parameters of cirrhotic liver tissue were larger than those of normal liver tissue. The sound velocity was 1577 m/s in normal liver tissue and 1631 m/s in cirrhotic liver tissue. At 35 MHz, the attenuation coefficient was 3.0 dB/mm in normal liver tissue and 4.1 dB/mm in cirrhotic liver tissue. The backscatter coefficient was 0.00431 dB/Srmm in cirrhotic liver tissue and 0.00303 dB/Srmm in normal liver tissue. The backscatter coefficient increased with the frequency. The high frequency images coincided with their histological features. CONCLUSION: The acoustic parameters, especially the sound backscatter coefficient, are sensitive to the changes of liver tissues and can be used to differentiate between the normal and pathological liver tissues. High frequency image system is a useful device for high-resolution image and tissue characterization.     

Detection of cardiomyopathic changes induced by doxorubicin based on quantitative analysis of ultrasonic backscatter

Ultrasonic measurements are valuable in characterizing cardiac dimensions and structure. Recently, analysis of ultrasonic properties of tissue has proved useful in detecting morphologic changes such as those accompanying myocardial infarction. This study was undertaken to determine whether acoustic properties of tissue can be utilized to detect cardiomyopathic changes as well. Cardiomyopathy was induced by prolonged administration of doxorublcin (Adriamycin) (1.2 mg/kg twice weekly) in 25 rabbits and results were compared with those in normal control rabbits, housed identically. The 15 surviving treated animals were killed at selected intervals 10 to 18 weeks after initiation of drug administration and the hearts were analyzed for collagen content based on hydroxyproline. Regional ultrasonic backscatter was assessed with a frequency-averaging procedure to minimize effects of phase cancellation and with an independent method employing spectral display over the frequency range of 1 to 11 megahertz from which an index of backscatter at a single frequency (2.25 megahertz) could be calculated. In hearts from treated animals, collagen content was significantly increased (p <0.05). Integrated ultrasonic backscatter was markedly increased (by more than 500 percent, that is, equivalent to 7 decibels) in fibrotic regions and significantly, although less markedly, in myopathic regions without marked collagen deposition. Thus, increased backscatter correlated with collagen deposition. Backscatter at 2.25 megahertz was significantly increased (by more than 500 percent, that is, equivalent to 7 decibels) in fibrotic regions.These results indicate that alterations in acoustic properties occur in cardiomyopathic tissue and that such alterations can be detected with the use of reflected ultrasound. Accordingly, assessment of integrated backscatter offers a promising approach for early clinical detection and characterization of evolution of cardiomyopathy induced by doxorubicin or of other causes.     

Quantitative ultrasonic assessment of normal and ischaemic myocardium with an acoustic microscope: relationship to integrated backscatter

PURPOSE OF INVESTIGATION--The aim was to study ultrasonic propagation properties of normal and ischaemic myocardium with a scanning laser acoustic microscope and to correlate these changes with ultrasonic backscatter. DESIGN--Myocardial ischaemia was produced by total occlusion of left anterior descending coronary artery in anaesthetised open chest dogs. Myocardium supplied by left circumflex coronary artery served as normal control. IBR5, an optimum weighted frequency average (4-6.8 MHz) of the squared envelope of diffraction corrected backscatter, was measured in vivo. Ultrasonic attenuation coefficient, an index of loss per unit distance, the propagation speed and heterogeneity index were measured from normal and ischaemic regions with a scanning laser acoustic microscope which operates at 100MHz in vitro. Myocardial water content of normal and ischaemic myocardium was also estimated. SUBJECTS--Were five anaesthetised mongrel dogs. RESULTS--Attenuation coefficient of 33.8(SD4.2) dB.mm-1 in the ischaemic tissue was lower than 63.8(17.2) dB.mm-1 in the normal tissue (p less than 0.01). Ultrasonic speed was lower in ischaemic than normal myocardium at 1584(25) v 1612(35) m.s-1 (p less than 0.05). Heterogeneity index of 11(7) m.s-1 in the ischaemic region was lower than 14(8) m.s-1 in the normal region (27% reduction, p less than 0.05). IBR5 and myocardial water content were higher in the ischaemic than the normal myocardium: -37.2(SEM1.8) dB v -46.6(0.6) dB, (p less than 0.01) and 80.9(0.0)% v 78(0.2)%, (p less than 0.05) respectively. CONCLUSION--Ultrasonic properties of the myocardium are significantly altered during acute ischaemia.     

Quantitative ultrasonic imaging: Tissue characterization and instantaneous quantification of cardiac function

Quantitative myocardial tissue characterization is being developed to complement and expand conventional echocardiography by delineating the physical state of myocardium under diverse pathophysiologic conditions. Real-time quantitative integrated backscatter imaging has already been applied to patients with ischemic heart disease, hypertrophic cardiomyopathy, and cardiac allograft rejection in clinical investigations performed in the United States, Europe, and Japan. A recently introduced modification of imaging processing algorithms employed for characterization of tissue facilitates automatic detection of endocardial-blood interfaces and on-line quantification of ventricular size and function. Further progress and anticipated developments in quantitative ultrasonic imaging will undoubtedly augment the clinical applications of tissue characterizations based on myocardial integrated backscatter for improved diagnosis, elucidation of pathophysiology, and assessment of cardiac function.     

Tissue Characterization by Ultrasound: What is Possible Now? What Will be Possible?

The purpose of this review is to discuss the principles of ultrasound tissue characterization. We describe gray scale analysis, backscatter techniques, real-time backscatter imaging, enhancement of abnormal tissue properties with contrast agents or liposomes, and use of acoustic microscopy. Ultrasound tissue characterization offers the promise of direct identification of abnormalities of the myocardium without relying on indirect manifestations such as abnormalities in cardiac function.     

In vivo ultrasonic tissue characterization of human intracardiac masses

Interactions between an ultrasonic signal and cardiac tissue have been used to characterize the histologic state of myocardium in vitro. To assess the utility of in vivo ultrasonic tissue characterization, stochastic analysis was applied to the digitized echocardiographic signals from 15 patients with 2-dimensional echocardiograms suggesting intracardiac masses. Ten subjects with echocardiograms suggesting mural thrombi underwent subsequent surgery or necropsy, which confirmed thrombi in 6 and revealed no thrombi (designated artifact) in 4. Five other patients had intracardiac tumors. The amplitudes within the digitized ultrasonic signals were displayed as histograms, which were described by a parameter k that represented the degree to which each histogram departed from a totally random probability density function. In 5 of 6 thrombi, k = 0, but in all 4 artifacts, k greater than 0. The sixth thrombus had k = 0.5 due to the specular effect of the interface between the thrombus' 2 lobes. All 5 tumors had k greater than 0. Ultrasonic tissue characterization using a stochastic analysis of backscatter can be performed in vivo and helps differentiate thrombus from artifact and tumor in the heart.     

Myocardial ultrasonic tissue characterization for estimating histological abnormalities in hypertrophic cardiomyopathy: comparison with endomyocardial biopsy findings.

AIMS: In this study, we investigated the clinical usefulness of ultrasonic tissue characterization with integrated backscatter for the evaluation of myocardial histological abnormalities in comparison with endomyocardial biopsy findings in patients with hypertrophic cardiomyopathy. METHODS: Twenty patients with hypertrophic cardiomyopathy and 20 normal subjects were enrolled in this study. We measured two parameters for the ultrasonic tissue characterization with integrated backscatter: the magnitude of the cardiac-cycle-dependent variation in integrated backscatter signals (cdv-IB) and the mean value of integrated backscatter signals calibrated by the pericardium (cal-IB). These parameters were measured at both the interventricular septum and the left ventricular posterior wall. Histological findings of right ventricular endomyocardial biopsy specimens were analyzed by computer image analyzer. RESULTS: cdv-IB was significantly lower and cal-IB significantly higher in both the interventricular septum and the left ventricular posterior wall in patients with hypertrophic cardiomyopathy compared with normal subjects. In patients with hypertrophic cardiomyopathy, the degree of myocardial disarray, interstitial fibrosis, and nonhomogeneity of myocyte size showed positive correlations with cal-IB and negative correlations with cdv-IB. CONCLUSIONS: Ultrasonic tissue characterization with IB enables the noninvasive evaluation of myocardial histological abnormalities in patients with hypertrophic cardiomyopathy.