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

将逆传输线矩阵建模方法应用于超声计算机层析成像。数值模拟中考虑了二维声场。并对几个对象进行了数值演示。对于对象的密度仅与环境介质不同的情况，对象的形状被很好地重构。结果表明，逆传输线矩阵模型适用于计算机层析成像。对于对象的声速仅与环境介质不同的另一种情况，对象的重建形状被变形。当测量点的间距大于入射声波的波长时，不能重建物体的形状。通过水下实验，超声换能器前方几个位置的测量波形与计算的正向传播过程的TLM解定性地吻合。然后将测量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的反向传播。

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.