Noninvasive Measurement of 3D Thermal Distribution by Using the Ultrasonic Inverse Scattering Quantitative CT Technique

本文针对遥感无创CT测温技术的实现，对逆散射定量CT技术进行了研究。本技术利用了介质的温度依赖性随声速变化的声学特性。也就是说，物体的温度分布是从已知的恒温状态重建物体的声速变化得到的。为了满足逆散射定量CT技术实现的实际要求，研究了利用目标垂直轴周围观测数据的准CT技术和基于后向传播Rytov变换的弱散射线性化逼近方法。作为试验检验的结果，利用模拟数据论证了实际情况下假设的接收复声压幅值的测量误差与水介质中温度图像的精度之间的依赖关系。当图像分辨率设置为5 mm，接收信号的信噪比大于30d B时，在10℃温度范围内，重建的温度图像的精度低于0.1度。因此，发展了一种高速、高精度的介质三维温度分布的无创测量技术，在医疗诊断或工业控制中有很好的应用前景。

In this study, the inverse scattering quantitative CT technique was investigated aiming at the realization of the remote sensing noninvasive CT temperature measurement technique. The present technique utilizes the acoustic character of the temperature dependencies of the medium with the variation of the sound speed. That is, the temperature distribution of the objet was obtained from the reconstruction of the sound speed variation of the object from the known constant temperature state. The quasi 31) CT technique using the observation data around the perpendicular axis of the object, and the weak scattering linearization approximation method by the backward propagation Rytov transform were examined to meet the practical requirement encountered in the realization of the inverse scattering quantitative CT technique. As a result of the test examination, the dependencies between the measurement error of the received complex sound pressure amplitude assumed in the practical situation and the precision of the temperature image in the water medium was demonstrated using the simulation data. For the case when the resolution of the image was set with 5mm and the signal to noise ratio of the received signal was over 30 dB, the precision of the reconstructed temperature image was proved to be under 0.1 degree over the 10 degree temperature range. As a result, high speed and high precision noninvasive measurement technique of the 3D temperature distribution of the medium was developed, which promises well to the applications in the medical diagnosis or the industrial plant control.