Propagation of shear waves generated by a modulated finite amplitude radiation force in a viscoelastic medium
Propagation of shear waves generated by a modulated finite amplitude radiation force in a viscoelastic medium
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粘弹性介质中调制有限幅辐射力产生的剪切波的传播
DOI：
10.1109/tuffc.2009.1074
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
Richard S. C. Cobbold
中科院分区：
文献类型：
--
作者：
A. Giannoula;Richard S. C. Cobbold
利用两个频率略有不同的共焦准连续波束干涉产生的调制辐射力，是在组织内非侵入性产生局域窄带低频剪切波的有效方法。本课题组曾利用近似粘弹性格林函数研究了基波调制频率下传播剪切场分量的性质。然而，可能需要高幅度的源激励来提高组织中剪切波检测的信噪比。本文研究了在一般符合诊断安全标准的条件下，在调制频率的谐波下，动态辐射力分量的产生和传播。我们描述了产生的简谐横波的传播特性，并讨论了它们如何依赖于非线性、聚焦增益和吸收参数。对于高粘度(被认为是软组织的特征)和较高调制频率的条件，近似剪切波格林函数是不合适的。在k-空间中导出了一个更精确的粘弹性格林函数，并用它来表示与Voigt组织模型相关的低通和色散效应。最后，说明了如何根据剪切波谱的几个频谱分量来估计传播介质的粘弹性性质。
An effective way to generate localized narrow-band low-frequency shear waves within tissue noninvasively, is by the modulated radiation force, resulting from the interference of two confocal quasi-CW ultrasound beams of slightly different frequencies. By using approximate viscoelastic Green's functions, investigations of the properties of the propagated shear-field component at the fundamental modulation frequency were previously reported by our group. However, high-amplitude source excitations may be needed to increase the signal-to-noise-ratio for shear-wave detection in tissue. This paper reports a study of the generation and propagation of dynamic radiation force components at harmonics of the modulation frequency for conditions that generally correspond to diagnostic safety standards. We describe the propagation characteristics of the resulting harmonic shear waves and discuss how they depend on the parameters of nonlinearity, focusing gain, and absorption. For conditions of high viscosity (believed to be characteristic of soft tissue) and higher modulation frequencies, the approximate shear wave Green's function is inappropriate. A more exact viscoelastic Green's function is derived in k-space, and using this, it is shown that the lowpass and dispersive effects, associated with a Voigt model of tissue, are more accurately represented. Finally, it is shown how the viscoelastic properties of the propagating medium can be estimated, based on several spectral components of the shear wave spectrum.
衰减介质中超声波束图案的有限振幅效应。
DOI：
10.1121/1.398441
发表时间：
1989
期刊：
The Journal of the Acoustical Society of America
影响因子：
--
作者：
Reilly,CR;Parker,KJ
通讯作者：
Parker,KJ