Research On The Method Of Ultrasonic Temperature Measurement Based On The Transmission Characteristics

High intensity focused ultrasound(HIFU) technique is another innovative technology after the four famous cancer treatment technology. It is non-destructive, local green, in line with the concept of "health concept", and so on.Thus it is considered to be one of the most potential applications of new tumor treatment technology in the 21 st century. Noninvasive temperature measurement about the treatment of target area tissue in real-time and accurately is one of the research focuses and key technologies. The ultrasonic noninvasive temperature measurement method is focused on low cost, good compatibility, simple operation and other advantages.In this thesis, through the experiments on pork tissue in vitro with the HIFU noninvasive temperature measurement, it has obtained a lot of ultrasonic echo signal data at different temperatures.Then after the research on the ultrasonic transmission characteristics and signal processing methods,the thesis discusses the relationship between the scattering characteristics and attenuation characteristics of ultrasonic transmissions with the change of the tissue temperature. Here are the main contents :1. Using the HIFU noninvasive measurement experiment system to experiment with pork tissue in vitro, we have access to a lot of ultrasonic echo signal data at different temperatures. And then we study on the pretreatment methods of echo signal, including filter, the methods of capturing data,and analyze the results of pretreatment.2. On the basis of random fluctuation medium ultrasonic scattering theory and the acoustic wave equation in biological non-homogeneous medium, the relationship between scattering coefficient and temperature is deduced. And two kinds of methods, direct interception and the EMD method,have been respectively adopted to analyze the experimental data. The results show that ultrasonic scattering coefficient increases with the temperature, which can be used to extract temperature information in tissue from the ultrasonic echo signal effectively.3. According to the acoustic attenuation characteristics of transmission, a variety of methods, such as time domain,frequency domain, time-frequency domain, transfer function,are adopted to extract the ultrasonic scattering coefficient.The results have been compared, and the feasibility of measuring temperature has been analyzed. The results show thatthe methods of the time-frequency domain analysis and transfer function can primely reflect the change of tissue characteristics: The temperature sensitivity and distinguish ability of the time-frequency domain method are quite high and they almost present a linear relationship, while the solidification and the degree of damage of the tissue protein can be more easily obtained by the transfer function method.