Velichko Alexander, Villaverde Eduardo Lopez, Croxford Anthony J
Department of Mechanical Engineering, University of Bristol, Bristol, BS8 1TR, UK.
Sci Rep. 2021 Jan 13;11(1):993. doi: 10.1038/s41598-020-79617-z.
Ultrasonic imaging is a widely used tool for detection, localisation and characterisation of material inhomogeneities with important applications in many fields. This task is particularly challenging when imaging in a complex medium, where the ultrasonic wave is scattered by the material microstructure, preventing detection and characterisation of weak targets. Fundamentally, the maximum information that can be experimentally obtained from each material region consists of a set of reflected signals for different incident waves. However, these data are not directly accessible from the raw measurements, which represent a superposition of reflections from all scatterers in the medium. Here we show, that a complete set of transmitter-receiver data encodes sufficient information in order to achieve full spatio-temporal separation of transmitter-receiver data, corresponding to different local scattering areas. We show that access to the local scattering data can provide valuable benefits for many applications. More importantly, this technique enables fundamentally new approaches, exploiting the angular distribution of the scattering amplitude and phase of each local scattering region. Here we demonstrate how the local scattering directivity can be used to build the local scattering image, releasing the full potential and richness of the transmit-receive data. As a proof of concept, we demonstrate the detection of small inclusions in various highly scattering materials using numerical and experimental examples. The described principles are very general and can be applied to any research field where the phased array technology is employed.
超声成像作为一种广泛应用的工具，用于检测、定位和表征材料的不均匀性，在许多领域都有重要应用。当在复杂介质中成像时，这项任务极具挑战性，因为超声波会被材料微观结构散射，从而妨碍对弱目标的检测和表征。从根本上说，从每个材料区域实验获得的最大信息由一组针对不同入射波的反射信号组成。然而，这些数据无法从原始测量中直接获取，原始测量代表了介质中所有散射体反射的叠加。在此我们表明，一组完整的发射 - 接收数据编码了足够的信息，以便实现发射 - 接收数据在时空上的完全分离，对应于不同的局部散射区域。我们表明，获取局部散射数据可为许多应用带来宝贵益处。更重要的是，该技术开启了全新的方法，利用每个局部散射区域散射幅度和相位的角分布。在此我们展示了如何利用局部散射方向性构建局部散射图像，释放发射 - 接收数据的全部潜力和丰富信息。作为概念验证，我们通过数值和实验示例展示了在各种高散射材料中检测小夹杂物的方法。所描述的原理非常通用，可应用于任何采用相控阵技术的研究领域。
