Parker Kevin J, Ormachea Juvenal, Will Scott, Hah Zaegyoo
Department of Electrical and Computer Engineering, University of Rochester, Rochester, New York, USA.
Department of Electrical and Computer Engineering, University of Rochester, Rochester, New York, USA.
Ultrasound Med Biol. 2018 Jul;44(7):1504-1515. doi: 10.1016/j.ultrasmedbio.2018.03.014. Epub 2018 Apr 26.
The propagation of shear waves from impulsive forces is an important topic in elastography. Observations of shear wave propagation can be obtained with numerous clinical imaging systems. Parameter estimations of the shear wave speed in tissues, and more generally the viscoelastic parameters of tissues, are based on some underlying models of shear wave propagation. The models typically include specific choices of the spatial and temporal shape of the impulsive force and the elastic or viscoelastic properties of the medium. In this work, we extend the analytical treatment of 2-D shear wave propagation in a biomaterial. The approach applies integral theorems relevant to the solution of the generalized Helmholtz equation, and does not depend on a specific rheological model of the tissue's viscoelastic properties. Estimators of attenuation and shear wave speed are derived from the analytical solutions, and these are applied to an elastic phantom, a viscoelastic phantom and in vivo liver using a clinical ultrasound scanner. In these samples, estimated shear wave group velocities ranged from 1.7 m/s in the liver to 2.5 m/s in the viscoelastic phantom, and these are lower-bounded by independent measurements of phase velocity.
剪切波从脉冲力的传播是弹性成像中的一个重要课题。可以通过众多临床成像系统获得剪切波传播的观测结果。组织中剪切波速度的参数估计，以及更一般地组织的粘弹性参数估计，是基于一些剪切波传播的基础模型。这些模型通常包括脉冲力的空间和时间形状以及介质的弹性或粘弹性特性的特定选择。在这项工作中，我们扩展了生物材料中二维剪切波传播的解析处理。该方法应用与广义亥姆霍兹方程解相关的积分定理，并且不依赖于组织粘弹性特性的特定流变模型。衰减和剪切波速度的估计器从解析解中导出，并使用临床超声扫描仪将其应用于弹性体模、粘弹性体模和体内肝脏。在这些样本中，估计的剪切波群速度范围从肝脏中的1.7米/秒到粘弹性体模中的2.5米/秒，并且这些速度由相速度的独立测量给出下限。
