Development of Ultrasonic CT System Using Inverse Transmission-Line Matrix Modeling

将反传输在线矩阵建模应用于超声计算机断层扫描（CT）。数值模拟考虑二维声场。对几个对象进行了数值演示。对于物体的密度仅与周围介质不同的情况，可以很好地重建物体的形状。结果表明，反传输在线矩阵模型可以用于计算机层析成像。对于另一种情况，即物体的声速仅与周围介质不同时，物体的重构形状发生变形。当测点间距大于投影声波的波长时，物体形状无法重建。通过水下实验，超声换能器前几个位置的实测波形与计算得到的正向传播过程TLM解定性一致。然后将测量到的波形输入到为反向传播开发的计算机程序中。证实了声波向主声源反向传播。

The inverse transmission-line matrix modeling is applied to a ultrasonic computer tomography (CT). Two-dimensional acoustic field is considered for the numerical simulations. Some numerical demonstrations are made for several objects. For the case that the density of the object is only different from the ambient medium, the shape of the object is well reconstructed. It is found that the inverse transmission-line matrix modeling is capable for the computer tomography. For another case that the sound speed of the object is only different from the ambient medium, the reconstructed shape of object is deformed. The object shape can not be reconstructed for the case that the separation of measurement points is lager than the wavelength of projected sound wave. Through the experiments under the water, the measured waveforms at the several position in front of the ultrasonic transducer qualitatively agree with the calculated TLM solutions for the forward propagation process. The measured waveforms are then inputted into the computer program developed for the inverse propagation. It is confirmed that the sound waves propagate reversely to the primary sound source.