Near-field effects in Green's function retrieval from cross-correlation of elastic fields: experimental study with application to elastography.
Near-field effects in Green's function retrieval from cross-correlation of elastic fields: experimental study with application to elastography.
复制标题
从弹性场互相关检索格林函数中的近场效应：应用于弹性成像的实验研究。
DOI：
10.1121/1.4795771
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
C. Negreira
中科院分区：
文献类型：
--
作者：
N. Benech;J. Brum;S. Catheline;T. Gallot;C. Negreira
在无损耗系统中，弹性波的因果和非因果绿色函数可以通过在两个位置处互相关弹性场来恢复。这个领域，由会聚波和发散波，被解释在一个时间反演过程的框架。本文通过弹性动力学绿色函数分析了近场效应对弹性波时空聚焦的影响。与标量场的情况相反，空间聚焦不是对称的，而是保持简单源的方向性图案。空间不对称性的一个重要特征是它依赖于固体的泊松比。此外，它表明，体波速度值的检索是受衍射。校正因子取决于源和观测场之间的相对方向。对软固体的体积进行了实验验证。在样品的自由表面处的随机冲击产生低频扩散状场。通过标准散斑跟踪技术使用超声对位移场进行成像。这项工作的一个重要应用是在软生物组织中的剪切弹性模量的估计中，其量化可以用于各种疾病的非侵入性诊断。
In a lossless system, the causal and acausal Green's function for elastic waves can be retrieved by cross-correlating the elastic field at two positions. This field, composed of converging and diverging waves, is interpreted in the frame of a time-reversal process. In this work, the near-field effects on the spatio-temporal focusing of elastic waves are analyzed through the elastodynamic Green's function. Contrary to the scalar field case, the spatial focusing is not symmetric preserving the directivity pattern of a simple source. One important feature of the spatial asymmetry is its dependency on the Poisson ratio of the solid. Additionally, it is shown that the retrieval of the bulk wave speed values is affected by diffraction. The correction factor depends on the relative direction between the source and the observed field. Experimental verification of the analysis is carried out on the volume of a soft-solid. A low-frequency diffuse-like field is generated by random impacts at the sample's free surface. The displacement field is imaged using ultrasound by a standard speckle tracking technique. One important application of this work is in the estimation of the shear elastic modulus in soft biological tissues, whose quantification can be useful in non-invasive diagnosis of various diseases.
影响因子：
56.9
作者：
MUTHUPILLAI, R;LOMAS, DJ;EHMAN, RL
通讯作者：
EHMAN, RL