Myocardial Perfusion Quantitation with Dual Spectra Echo

描述（由申请人提供）： 局部心肌灌注的定量对于评估心肌缺血的程度是必不可少的。现有的心肌声学造影（MCE）的无创方法显着阻碍了有限的再现性，由于不同的衰减的谐波信号发出的声学造影剂微泡。我们的长期目标是研究心血管系统内的非线性超声信号传播，并开发一个强大的衰减补偿的数学模型。我们的初步方法，用于将接收到的宽带信号分解成基波和谐波（即，双）频谱，导致在引入谐波到基波比峰值（HFRP）的频谱包络。HFRP参数在区分灌注和非灌注心肌时对信号衰减的变化进行自我补偿。我们假设线性和非线性超声信号传播的分析模型可以重复校正谐波频谱衰减。本研究的短期目标是在规定的信号衰减水平下，在校准的组织模型和心肌灌注的动物模型中检验这一假设。目的1：表征通过具有校准衰减的组织体模传播期间基波和谐波频谱的变化。目标二：定义的精密度和准确度的可变流速测量在体内使用衰减校正所提出的双谱方法。目标3：确定双谱方法在不同衰减水平下估计局部心肌血流量的精密度和准确度。目的4：探索冠状动脉狭窄时心肌灌注定量的新方法。目的5：建立双光谱法定量微血管阻塞血流灌注的方法。为了实现这些目标，我们将分析从组织灌注模型和跳动的狗心脏诱导缺血获得的数字射频超声数据，确定染色标本中的缺血风险区域，并从放射性标记微球的局部活动中定义参考灌注流量。新奇之处在于使用双光谱的基本分量作为谐波“灌注成像”分量的自动衰减补偿的即时“内部参考”。这样的原则应该允许通过MCE对灌注进行可再现的定量。

DESCRIPTION (provided by applicant): Quantitation of local myocardial perfusion is essential for the assessment of the extent of myocardial ischemia. The existing noninvasive approaches in myocardial contrast echocardiography (MCE) are significantly hampered by limited reproducibility due to variable attenuation of the harmonic signals emanating from insonated contrast microbubbles. Our long-term objective is to study nonlinear ultrasound signal propagation within the cardiovascular system and develop a robust mathematical model for attenuation compensation. Our preliminary method for decomposing a received broadband signal into the fundamental and harmonic (ie, dual) frequency spectra has resulted in the introduction of a Harmonic-to- Fundamental Ratio peak (HFRp) of the spectral envelope. The HFRp parameter self-compensates for variations in signal attenuation while differentiating perfused and nonperfused myocardium. We hypothesize that an analytical model of linear and nonlinear ultrasound signal propagation can reproducibly correct for harmonic spectrum attenuation. The short-term objective of the present reseach is to test the hypothesis in calibrated tissue phantoms and animal models of myocardial perfusion under defined levels of signal attenuation. Aim 1: Characterize changes in the fundamental and harmonic spectra during propagation through a tissue phantom with calibrated attenuation. Aim 2: Define the precision and accuracy of variable flow velocity measurements in vivo using attenuation correction by the proposed dual spectrum method. Aim 3: Determine the precision and accuracy of the dual spectrum method for estimation of regional myocardial blood flow under varying levels of attenuation. Aim 4: Validate the new method for quantitation of myocardial perfusion during coronary stenosis. Aim 5: Validate the dual spectrum method for perfusion quantitation in microvascular obstruction. To accomplish these aims, we will analyze digital radiofrequency ultrasound data obtained from tissue perfusion phantoms and beating dog hearts with induced ischemia, determine the region of ischemic risk in stained specimens, and define the reference perfusion flow from local activities of radiolabeled microspheres. The novelty is in the use of the fundamental component of the dual spectra as an immediate "internal reference" for automatic attenuation compensation of the harmonic "perfusion imaging" component. Such a principle should allow reproducible quantitation of perfusion by MCE.