IEEE Trans Ultrason Ferroelectr Freq Control. 2016 Sep;63(9):1306-20. doi: 10.1109/TUFFC.2016.2547341. Epub 2016 Mar 25.
The estimation of many spectral-based quantitative ultrasound parameters assumes that backscattered echo signals are from a stationary, incoherent scattering process. The accuracy of these assumptions in real tissue can limit the diagnostic value of these parameters and the physical insight about tissue microstructure they can convey. This work presents an empirical decision test to determine the presence of significant coherent contributions to echo signals and whether they are caused by low scatterer number densities or the presence of specular reflectors or scatterers with periodic spacing. This is achieved by computing parameters from echo signals that quantify stationary or nonstationary features related to coherent scattering, and then comparing their values to thresholds determined from a reference material providing diffuse scattering. The paper first presents a number of parameters with demonstrated sensitivity to coherent scattering and describes criteria to select those with the highest sensitivity using simulated and phantom-based echo data. Results showed that the echo amplitude signal-to-noise ratio and the multitaper-generalized spectrum were the parameters with the highest sensitivity to coherent scattering with stationary and nonstationary features, respectively. These parameters were incorporated into the reference-based decision test, which successfully identified regions in simulated and tissue-mimicking phantoms with different incoherent and coherent scattering conditions. When scatterers with periodic organization were detected, the combination of stationary and nonstationary analysis permitted the estimation of the mean spacing below and above the resolution limit imposed by the pulse size. Preliminary applications of this algorithm to human cervical tissue ex vivo showed correspondence between regions of B-mode images showing bright reflectors, tissue interfaces, and hypoechoic regions with regions classified as specular reflectors and low scatterer number density. These results encourage further application of the algorithm to more structurally complex phantoms and tissue.
许多基于光谱的定量超声参数的估计假设背散射回波信号来自于一个静止的、非相干散射过程。这些假设在实际组织中的准确性可能会限制这些参数的诊断价值，以及它们能够传递的关于组织微观结构的物理洞察力。这项工作提出了一种经验决策测试，以确定回声信号中是否存在显著的相干贡献，以及它们是由低散射体密度还是镜面反射器或具有周期性间隔的散射体引起的。这是通过计算与相干散射相关的静止或非静止特征的回波信号参数来实现的，然后将它们的值与来自提供漫散射的参考材料确定的阈值进行比较。本文首先介绍了一些已被证明对相干散射敏感的参数，并描述了使用模拟和基于体模的回波数据选择具有最高敏感性的参数的标准。结果表明，回波幅度信噪比和多谱广义谱是对具有静止和非静止特征的相干散射最敏感的参数。这些参数被纳入基于参考的决策测试中，该测试成功地识别了具有不同非相干和相干散射条件的模拟和组织模拟体模中的区域。当检测到具有周期性组织的散射体时，静止和非静止分析的组合允许估计在脉冲大小施加的分辨率限制以下和以上的平均间距。该算法对人宫颈组织的初步应用表明，B 模式图像中显示亮反射器、组织界面和低回声区域的区域与分类为镜面反射器和低散射体密度的区域之间存在对应关系。这些结果鼓励进一步将该算法应用于更具结构复杂性的体模和组织。
