ANISOTROPY IN MYOCARDIAL ULTRASOUND

项目摘要/摘要本研究的长期目标是提高超声心动图作为主要成像方式的能力，以确定心脏特性的量化和评估最佳诊断所需的功能。心脏诊断超声的临床应用需要声音以相对于主要心肌纤维方向的不同角度传播的成像。因此，超声特性随组织传播方向的变化，即各向异性，是临床超声心动图的一个重要因素。心脏超声应用前景广阔的领域，如心肌应变和应变率成像、超声心动图对比、心肌组织表征等，都受到心肌各向异性特性的影响。与本研究相关的所有研究的基础是，更好地理解心肌各向异性超声特性的基本机制，以及病变心脏各向异性特性改变的后果，将促进和增强超声在临床领域中对特定病理程度和严重程度的无创检测和量化中的作用。因此，本研究的具体目标是确定导致心肌固有超声特性各向异性的机制，并开发利用各向异性在基于超声心动图的患者心脏评估中的影响的方法。为了集中研究工作，特别强调了研究旨在调查与肥厚性心肌病相关的心肌结构改变（即各向异性改变）对超声心动图成像和组织表征的影响。为了实现这些目标，我们确定了以下具体目标，为提高超声诊断能力提供基础：1)确定导致超声后向散射、衰减和心肌速度各向异性的机制；2)制定策略，利用机会和克服超声心动图成像和正常和病变心脏心肌评估的各向异性所带来的潜在障碍。旨在解决这些具体目标的研究包括：测量切除的心肌标本，以提供宽带上的固有超声散射和衰减特性；测量和开发与识别有效散射特性和粘弹性特性相关的模型，这些特性负责观察到的特性的各向异性；心肌各向异性对谐波成像影响的研究一种测量跨壁肌纤维方向的极性后向散射方法的建立研究肥厚性心肌病引起的心肌结构和特性改变程度对超声后向散射和衰减特性的影响以及评估患者这些特性改变的方法的发展。项目叙述相关性：本研究结果将增强心脏超声成像作为辅助心脏病诊断的有效工具的能力。由于心脏的微观结构特性可以显著影响超声特性，因此，超声图像，更好地了解这些特性的性质将为使用超声来表征患病心脏的特征提供新的见解。

DESCRIPTION (provided by applicant): Project Summary/Abstract The long-term objective of this research is to enhance the capabilities of echocardiography as a primary imaging modality for the definitive quantification of cardiac properties and assessment of function needed for optimal diagnoses. Clinical applications of cardiac diagnostic ultrasound require imaging with the sound propagating at varying angles relative to the predominant myocardial fiber orientation. Consequently, variation of ultrasonic properties with the direction of propagation in tissue, i.e., anisotropy, is a significant factor in clinical echocardiography. Promising areas of application of cardiac ultrasound such as myocardial strain and strain-rate imaging, contrast echocardiography, and myocardial tissue characterization are all subject to effects arising from the anisotropic properties of myocardium. Underlying all of the studies associated with this research is the assertion that a better understanding of the fundamental mechanisms underlying the observed anisotropic ultrasonic properties of myocardium, and the consequences of altered anisotropic properties of diseased hearts, will facilitate and enhance the role of ultrasound in the non-invasive detection and quantification of the extent and severity of specific pathologies in the clinical arena. Hence, the specific goals of this research are to identify the mechanisms contributing to the observed anisotropy of the intrinsic ultrasonic properties of myocardium and to develop approaches for exploiting the effects of anisotropy in echocardiographic-based assessments of the hearts of patients. In order to focus the research effort, a special emphasis has been placed on studies designed to investigate the effects of altered myocardial architecture (i.e., altered anisotropy) associated with hypertrophic cardiomyopathy on echocardiographic imaging and tissue characterization. To achieve these goals, the following Specific Aims have been identified to provide a basis for improving the diagnostic power of ultrasonics: 1) Identify mechanisms contributing to the observed anisotropy in ultrasonic backscatter, attenuation, and velocity of myocardium; and 2) Develop strategies for exploiting opportunities and overcoming potential stumbling blocks arising from anisotropy in echocardiographic imaging and myocardial assessment in normal and diseased hearts. Studies designed to address these Specific Aims include: measurements of excised myocardial specimens to provide the intrinsic ultrasonic scattering and attenuation properties over a broad bandwidths; measurements and the development of models associated with the identification of effective scatterer characteristics and viscoelastic properties responsible for the observed anisotropy of properties; investigations of the effects of myocardial anisotropy on harmonic imaging; development of a polar backscatter method of measuring the transmural myofiber orientation; and measurements investigating how the degree of altered myocardial structure and properties due to hypertrophic cardiomyopathy affect the ultrasonic backscatter and attenuation properties and the development of methods for assessing these altered properties in patients.Project Narrative Relevance: Results of this research will enhance the capabilities of ultrasonic imaging of the heart as an effective tool in aiding diagnoses of heart disease. Because the microstructural properties of the heart can significantly influence the ultrasonic properties and, therefore, ultrasonic images, a better understanding of the nature of these properties will provide new insights into the use of ultrasound to characterize features of diseased hearts.