Caenen Annette, Knight Anna E, Rouze Ned C, Bottenus Nick B, Segers Patrick, Nightingale Kathryn R
IBiTech-bioMMeda, Ghent University, Ghent, Belgium; Department of Cardiology, University Medical Center Rotterdam, Erasmus MC, Rotterdam, The Netherlands.
Department of Biomedical Engineering, Duke University, Durham, NC, United States.
J Mech Behav Biomed Mater. 2020 Jul;107:103754. doi: 10.1016/j.jmbbm.2020.103754. Epub 2020 Apr 8.
Tissue nonlinearity is conventionally measured in shear wave elastography by studying the change in wave speed caused by the tissue deformation, generally known as the acoustoelastic effect. However, these measurements have mainly focused on the excitation and detection of one specific shear mode, while it is theoretically known that the analysis of multiple wave modes offers more information about tissue material properties that can potentially be used to refine disease diagnosis. This work demonstrated proof of concept using experiments and finite element simulations in a uniaxially stretched phantom by tilting the acoustic radiation force excitation axis with respect to the material's symmetry axis. Using this unique set-up, we were able to visualize two propagating shear wave modes across the stretch direction for stretches larger than 140%. Complementary simulations were performed using material parameters determined from mechanical testing, which enabled us to convert the observed shear wave behavior into a correct representative constitutive law for the phantom material, i.e. the Isihara model. This demonstrates the potential of measuring shear wave propagation in combination with shear wave modeling in complex materials as a non-invasive alternative for mechanical testing.
在剪切波弹性成像中，组织非线性通常通过研究组织变形引起的波速变化来测量，这一现象通常被称为声弹性效应。然而，这些测量主要集中在一种特定剪切模式的激发和检测上，而从理论上可知，对多种波模式的分析能够提供更多关于组织材料特性的信息，这些信息有可能用于改进疾病诊断。这项工作通过在单轴拉伸体模中进行实验和有限元模拟，将声辐射力激发轴相对于材料对称轴倾斜，从而证明了概念。利用这种独特的设置，对于大于140%的拉伸，我们能够在拉伸方向上可视化两种传播的剪切波模式。使用通过力学测试确定的材料参数进行了补充模拟，这使我们能够将观察到的剪切波行为转化为体模材料的正确代表性本构定律，即石原模型。这证明了在复杂材料中结合剪切波传播测量和剪切波建模作为力学测试的非侵入性替代方法的潜力。
