In vivo mechanical characterization of soft biological tissues has broad applications ranging from disease diagnosis to tissue engineering. Shear wave elastography based on the bulk wave theory has been widely used to measure the mechanical properties of soft tissues. Given that most soft tissues basically have layered structures, the dispersive feature of elastic waves should be considered when the thickness of the interested layer is comparable to or smaller than the wavelength. Bearing this fundamental issue in mind, we propose an ultrasound-based guided wave elastography (GWE) method to characterize the mechanical properties of layered soft tissues. The dispersion relations of guided waves in layered structures were derived first, and its explicit expression was achieved. An inverse approach based on the dispersion relation to characterize the mechanical properties of layered soft tissues was then established. Both finite element analysis (FEA) and phantom experiments were carried out to validate the new method. In vivo experiments on forearm skin demonstrate the usefulness of the present method in characterizing layered soft tissues. STATEMENT OF SIGNIFICANCE: Layered soft tissues and artificial soft materials are ubiquitous in both nature and engineering. Imaging their in vivo/in situ mechanical properties finds important applications and remains a great challenge to date. Here, we propose an ultrasound-based guided wave elastography method to in vivo/in situ characterize the elastic properties of layered soft materials. We validate the method via finite element analysis and phantom experiments and further demonstrate its usefulness in practice by performing in vivo measurements on forearm skins. Given that the dispersive feature of elastic waves in layered soft media is considered in our method, it provides the opportunity to assess the intrinsic elastic properties of an individual layer in a non-destructive manner as shown in our experiments.

中文翻译：

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分层软组织的导波弹性成像。

软生物组织的体内机械表征具有广泛的应用，范围从疾病诊断到组织工程。基于体波理论的剪切波弹性成像技术已被广泛用于测量软组织的力学性能。考虑到大多数软组织基本上都具有分层结构，因此当感兴趣层的厚度等于或小于波长时，应考虑弹性波的色散特征。考虑到这一基本问题，我们提出了一种基于超声的导波弹性成像（GWE）方法，以表征分层软组织的机械性能。首先导出了层状结构中导波的色散关系，并得到了其明确的表示形式。然后建立了一种基于色散关系的逆方法，以表征层状软组织的机械性能。进行了有限元分析（FEA）和体模实验，以验证该新方法。在前臂皮肤上的体内实验证明了本方法在表征层状软组织中的有用性。意义声明：分层的软组织和人造软材料在自然界和工程学中无处不在。对它们的体内/原位机械性能进行成像发现了重要的应用，并且迄今为止仍然是巨大的挑战。在这里，我们提出了一种基于超声的导波弹性成像方法，以体内/原位表征层状软材料的弹性。我们通过有限元分析和幻像实验验证了该方法，并通过在前臂皮肤上进行体内测量进一步证明了其在实践中的实用性。考虑到在我们的方法中考虑了弹性波在分层软介质中的色散特征，它为我们以实验中所示的非破坏性方式评估单个层的固有弹性特性提供了机会。