Research On The Monitoring Method Of The Biological Tissues’s Acoustic Characteristics’ Change In The Treatment Of HIFU

Due to its unique advantages,the technique of High intensity focused ultrasound(HIFU) has become one of the most potential applications of minimally invasive tumor treatment. In the treatment with HIFU technique, in order to kill cancer cells without damage to normal tissue, it is very important to monitoring the biological tissue characteristics for the treated area.In this thesis, we use the equipment build a High intensity focused ultrasound experimental system, and use it to heating the Pork tissue heating in vitro. Then, we can obtain the ultrasonic echo signal data in the experiment, to get the data what we wanted. After data preprocessing,use the signal processing methods to research the acoustic properties’ changes of biological tissue like the ultrasonic velocity and the ultrasonic attenuation coefficient. Here are the main contents:(1)Pre-treating the ultrasonic echo signal data of vitro tissue which obtained by experimental system. In order to use the echo signal data more convenient in next processing, we should do preprocessing for the signal, like filtering and intercepting waveforms.(2)Using Cross-correlation function procedure to process the signal data, detecting the time shifts between two backscattered ultrasonic signals. We can find that there do have some relationship between to the ultrasonic velocity and the properties of biological tissue, that the ultrasonic velocity will increase in the experiments, and the maximum rata take place in the 55℃-65℃.(3)We can find that there do have some relationship between to the ultrasonic attenuation coefficient and the properties of biological tissue by extracting the ultrasonic attenuation coefficient of the signal data. The ultrasonic attenuation coefficient will increase in the experiment due to the properties of biological tissue’s change. Then we can use this relationship to monitor the change of the properties of biological tissue in the treatment.(4)Based on discrete random medium model of biological tissue, use the ultrasonic echo signalsestablishing the AR transfer function. By using AIC, we can find out that in 80 order effect is best, then using the burg algorithm and the model parameters. And on the basis of the requested the transfer function, calculation of center of mass spectrum under different temperature and the normalized spectral power, we can find that the center of mass spectrum frequency will towards low frequency offset a rise of temperature, the normalized spectrum power will increase along with the rise of temperature.