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剂超声心动图(MCE)的非侵入性方法，由于辐射造影剂微泡发出的谐波信号的可变衰减，重复性有限而受到严重的阻碍。我们的长期目标是研究非线性超声信号在心血管系统内的传播，并开发一个稳健的数学模型来进行衰减补偿。我们将接收到的宽带信号分解成基频和谐波(即双重)频谱的初步方法导致了频谱包络的谐波与基波比峰值(HFRp)的引入。HFRp参数对信号衰减的变化进行自我补偿，同时区分灌流心肌和非灌流心肌。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地校正谐波频谱衰减。本研究的短期目标是在确定的信号衰减水平下，在校准的组织模体和心肌灌注的动物模型中检验这一假说。目的1：研究组织模体传播过程中基波和谐波谱的变化。目的2：利用所提出的双谱方法进行衰减校正，确定活体可变流速测量的精密度和准确度。目的3：确定不同衰减程度下双谱方法估计局部心肌血流量的精密度和准确度。目的4：验证冠脉狭窄时心肌灌注定量的新方法。目的5：验证微血管梗阻的双频谱血流灌注定量方法。为了实现这些目标，我们将分析从组织灌注模体和诱导缺血心脏跳动中获得的数字射频超声数据，确定染色样本中的缺血风险区域，并根据放射性标记微球的局部活性确定参考灌注量。其新奇之处在于使用双光谱的基本成分作为直接的“内部参照物”，以自动补偿谐波“灌注成像”成分的衰减。这样的原则应该允许通过MCE可重复性地定量灌注量。

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.