IEEE Trans Ultrason Ferroelectr Freq Control. 2020 Mar;67(3):483-496. doi: 10.1109/TUFFC.2019.2945620. Epub 2019 Oct 4.
Ultrasound shear wave elastography (SWE) is an increasingly used noninvasive modality for quantitative evaluation of tissue mechanical properties. SWE typically uses an acoustic radiation force to produce laterally propagating shear waves that are tracked in the spatial and temporal domains, in order to obtain the wave velocity. One of the ways to study the viscoelasticity is through studying the shear wave phase velocity dispersion curves. Shear wave attenuation can be also characterized in viscoelastic tissues with methods that use multiple lateral data samples. In this article, we present an alternative method for measuring the shear wave attenuation without using a rheological model two-point frequency shift (2P-FS). The technique uses information related to the amplitude spectra FS of shear waves measured at only two lateral locations. The theoretical basis for the 2P-FS is derived and validated. We examined how the first signal position and the distance between the two locations affect the shear wave attenuation estimation in the 2P-FS method. We tested this new method on digital phantom data created using the local interaction simulation approach (LISA) in viscoelastic media. Moreover, we tested data acquired from custom-made tissue-mimicking viscoelastic phantom experiments and ex vivo porcine liver measurements. We compared results from the 2P-FS method with the other two techniques used for assessing a shear wave attenuation: the FS-based method and the attenuation-measuring ultrasound shear wave elastography (AMUSE) technique. In addition, we evaluated the 2P-FS algorithm with different levels of added white Gaussian noise to the shear wave particle velocity using numerical phantoms. Tests conducted showed that the 2P-FS method gives robust results based on only two measurements and can be used to measure attenuation of viscoelastic soft tissues.
超声剪切波弹性成像（SWE）是一种越来越常用的非侵入性方法，用于定量评估组织力学特性。SWE 通常使用声辐射力产生横向传播的剪切波，在空间和时间域中跟踪这些剪切波，以获得波速。研究粘弹性的一种方法是通过研究剪切波相速度频散曲线。使用使用多个横向数据样本的方法也可以在粘弹性组织中表征剪切波衰减。本文提出了一种无需使用流变模型两点频移（2P-FS）即可测量剪切波衰减的替代方法。该技术仅使用在两个横向位置测量的剪切波 FS 的幅度谱信息。推导并验证了 2P-FS 的理论基础。我们研究了在 2P-FS 方法中，第一个信号位置和两个位置之间的距离如何影响剪切波衰减的估计。我们在粘弹性介质中使用局部相互作用模拟方法（LISA）创建的数字体模数据上测试了这种新方法。此外，我们还在定制的组织模拟粘弹性体模实验和离体猪肝测量中测试了这种新方法。我们将 2P-FS 方法的结果与用于评估剪切波衰减的其他两种技术（基于 FS 的方法和衰减测量超声剪切波弹性成像（AMUSE）技术）进行了比较。此外，我们还使用数值体模对剪切波粒子速度添加不同水平的加性高斯噪声，评估了 2P-FS 算法。测试结果表明，2P-FS 方法仅基于两次测量即可提供稳健的结果，可用于测量粘弹性软组织的衰减。
