Researching On Signals Acquisition System Of Microwave Induced Thermoacoustic Tomography

Microwave-induced thermoacoustic tomography (MITT) for biological tissue has been a hot research area these years. With this technique, a short-pulsed microwave beam is used to irradiate tissue samples. The tissue absorbs the microwave energy in a confined time and simultaneously generates temporal ultrasonic waves (named thermoacoustic signals) by thermoelastic expansion. The generated thermoacoustic signals carry information about the microwave absorption properties of the sample. The realization of MITT is based on these acquired thermoacoustic signals.Now, owing to the research on MITT still at its original stage in our nation, we haven't enough experimental systems as references. The experimental system was built up and the thermoacoustic signals were acquired successfully are the important preconditions of the realization of MITT. In order to acquire and pick-up the thermoacoustic signals, which were induced by microwave pulses, the data acquisition system used to acquire the thermoacoustic signals is developed based on the experimental system of MITT. The experimental system of MITT was also developed by our group. And all the acquisition system parameters were designed based on the characteristic of thermoacoustic signals. The acquisition system takes the advantages of small size, low cost and easy to operate, and it can finish signals acquisition, control, analysis, de-noised, display and convenient to use.The following research work has been carried out in this thesis:1. Developed the preprocessor. The characteristic of thermoacoustic signals such as amplitude and frequency were analyzed in our works. According to the analyzed results, the signal preprocessor was developed. The micro-controller (AT89C4051), the intelligence control and display chip (HD7279A) and some other elements were used to build up the gain display and control module of preprocessor. And AD604 and some other elements were used to build up the signals amplify and filter module of preprocessor. Moreover, the preprocessor can meet the needs of thermoacoustic signals acquisition in bandwidth, gain and noise control.2. Design and compilation of data acquisition and signals de-noised program. In order to control the acquisition length, sampling rate and saving mode of thermoacoustic signals, the data acquisition program was compiled based on LabVIEW platform. According to the mixing programming between LabVIEW and C language, the de-noised program was also complied to pick-up the thermoacoustic signals.3. Acquired the experimental data. Realize Experimental scheme design and thermoacoustic signals acquisition in animal tissue experiment. Finish analysis of the acquired signals. At the same time, According to the presented problem in experiment, the signals acquisition system was improved.In our research, we finished the follow works: developed the preprocessor, compiled the relative programs and acquired the experimental data. And the realization of these works can lay a solid foundation for building the experimental platform and realizing MITT.