Microwave Heat Caused By Ultrasound Imaging And Its Application In The Detection Of Breast Cancer

According to a large number of medical statistics, the cancer with the highest incidence is breast cancer among women. At present, about 1.2 million women suffer from breast cancer around the world each year, and over 0.45 million of them die of breast cancer. In the past 25 years, Chinese women's breast cancer incidence rate has increased by 52%. This rate has risen from the second to the first one in all the kinds of women's cancer. According to statistical data on clinical breast cancer treatment, early detection of breast cancer plays a decisive role in the effectiveness of treatment. The earlier the breast cancer is detected and treated, the higher survival rate after treatment can be obtained.As a kind of new technology, Microwave Induced Thermoacoustic Tomography (MITAT) has great potential in many areas of biomedical applications. In MITAT technology, by recording the ultrasound signals generated by the biological tissue, we reconstruct the radiation absorption characteristics of biological tissue. The reconstructed images are able to explain both physiology and pathology status of biological tissue. Thus it becomes a diagnostic basis. On one hand, the MITAT technology takes advantage of the high-contrast features of biological organization in the electromagnetic spectrum. On the other hand, it can use the small wavelength characteristics of ultrasonic signals. So this technology can obtain both high contrast and high resolution images. This paper focuses on the MITAT technology and its application in breast cancer detection. The discussion is mainly divided into five parts.1. Research background related to breast cancer detection. First the conventional methods of breast cancer detection have been introduced, and the difficulties and limitations of these methods in image reconstruction have also been described. Then the basic principles of MITAT have been discussed, including electromagnetic high contrast and ultrasonic high resolution. The history and current status of this research have been introduced at last.2. Theory of microwave induced thermoacoustic tomography. First the interaction between microwave and biological tissue has been analyzed, and the propagation characteristics of microwave in biological tissue have been discussed from electromagnetic point of view. Then the interaction between ultrasonic and biological tissue has been analyzed, and the propagation characteristics of ultrasonic in biological tissue have been discussed from acoustic point of view. At last, the whole process of MITAT has been discussed comprehensively. Besides, the simulative result of microwave heat accumulation effect has also been given.3. Image reconstruction method based on time reversal mirror (TRM) and pseudospectral time domain method (PSTD). First, several kinds of traditional medical imaging algorithm are introduced at first. Then image reconstruction method based on TRM and PSTD has been discussed in detail. Then the TRM-PSTD imager has been given. At last, two-dimensional and three-dimensional simulation results based on the TRM-PSTD imager are given.4. The design of the MITAT system. According to the requirement of MITAT, several key parts of the MITAT system have been carried out a detailed study, including microwave generator, pulse amplifier and ultrasonic transducer. Then a rectangular-circular horn has been designed and manufactured to improve the performance of electromagnetic radiation a reliable experimental imaging system has been built. The development of the system control program has been introduced at last.5. A variety of MITAT experiment has been carried out by the imaging system. First the characteristics of MITA signals are studied. Then MITAT and ultrasound imaging have been compared with experiment. At last, a number of different biological tissue imaging experiments are carried out.In this paper, microwave induced thermoacoustic tomography and its application in breast cancer detection have been systematic and deeply studied. By the TRM and PSTD method, both experimental and simulative results demonstrated superior to conventional medical imaging method performance. This work shows that the MITAT technique in breast cancer detection has great strengths and potential, and it will be promoted in biomedical engineering applications in the future.