Acoustic radiation force in tissue-like solids due to modulated sound field
Acoustic radiation force in tissue-like solids due to modulated sound field
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DOI：
10.1016/j.jmps.2012.04.006
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发表时间：
2012-10-01
影响因子：
5.3
通讯作者：
Guzina, Bojan B.
中科院分区：
文献类型：
--
作者：
Dontsov, Egor V.;Guzina, Bojan B.
本研究的重点是由高强度聚焦超声场(马赫数= 0（10(-3)）在低频信号调制的情况下，在均匀类组织固体中产生的持续体力（即所谓的声辐射力）。这种中间渐近问题与许多新兴的生物医学应用相关，其特征是许多小（但不会消失）参数，包括马赫数，调制与超声频率之间的比率，剪切与体积模量的比率以及无量纲衰减系数。在将软组织的响应近似为具有热传导的非线性粘弹性固体的响应的基础上，通过缩放范式来解决具有特色的二阶问题，其中横向坐标按焦点区域的宽度缩放，而轴向和时间坐标分别分为“快”和“慢”分量，其双重目的是：(1)消去控制高强度超声传播的场方程中的线性项，(2)考虑超声调制的影响。在聚焦超声分析的背景下，所提出的研究的关键特征围绕着时间变量的双时间尺度处理，这使得人们能够解析出超声及其调制在非线性解中的贡献。通过这种方法，通过计算日耳曼场方程的“快速”时间平均值，可以求出引起平均组织运动的声辐射力（ARF）。与现有理论的比较揭示了新公式带来的一些关键特征，包括对超声调制和热膨胀的ARF的贡献，以及本构非线性在通过聚焦超声束在类组织固体中产生持续体力的精确作用。(C) 2012 Elsevier Ltd.版权所有。
The focus of this study is the sustained body force (the so-called acoustic radiation force) in homogeneous tissue-like solids generated by an elevated-intensity, focused ultrasound field (Mach number = O(10(-3))) in situations when the latter is modulated by a low-frequency signal. This intermediate-asymptotics problem, which bears relevance to a number of emerging biomedical applications, is characterized by a number of small (but non-vanishing) parameters including the Mach number, the ratio between the modulation and ultrasound frequency, the ratio of the shear to bulk modulus, and the dimensionless attenuation coefficient. On approximating the response of soft tissues as that of a nonlinear viscoelastic solid with heat conduction, the featured second-order problem is tackled via a scaling paradigm wherein the transverse coordinates are scaled by the width of the focal region, while the axial and temporal coordinate are each split into a "fast" and "slow" component with the twin aim of: (i) canceling the linear terms from the field equations governing the propagation of elevated-intensity ultrasound, and (ii) accounting for the effect of ultrasound modulation. In the context of the focused ultrasound analyses, the key feature of the proposed study revolves around the dual-time-scale treatment of the temporal variable, which allows one to parse out the contribution of ultrasound and its modulation in the nonlinear solution. In this way the acoustic radiation force (ARF), giving rise to the mean tissue motion, is exacted by computing the "fast" time average of the germane field equations. A comparison with the existing theory reveals a number of key features that are brought to light by the new formulation, including the contributions to the ARF of ultrasound modulation and thermal expansion, as well as the precise role of constitutive nonlinearities in generating the sustained body force in tissue-like solids by a focused ultrasound beam. (C) 2012 Elsevier Ltd. All rights reserved.