| MTCT (Microwave-induced thermoacoustic computed tomography) is a kind of tomography technology that uses pulse-modulated microwave to excite thermoacoustic signals by irradiating biological tissues, and a kind of functional imaging technology whose spatial resolution ratio is much higher. Microwave energy will convert into heat when biological tissues absorb it, which therefore leads to thermal dilation of biological tissues, and then thermal dilation will cause instantaneous pressure distribution. This kind of pressure distribution caused by microwave pulse creates acoustic wave, called thermoacoustic wave, which transmits to tissue surface at different speed. Ultrasound detector around tissues can record thermoacoustic wave, and then original distribution of sound source or electromagnetism absorption of tissues can be figured out conversely, which is concerned with some characteristics of tissues. Tissues' spatial distribution would be got as long as distributionprecision of sound source or electromagnetism absorption is high enough, and that is called tissues functional imaging.Microwave irradiation to tissues is a kind of nonionizing radiation, which would not cause irreversible lesion of tissues if microwave irradiation power and time were controlled properly. Microwave acted as imaging tools can easily distinguish different tissues, especially normal tissues and cancer whose rate of water content and metabolism differs remarkably. This characteristic shows that microwave imaging has better image contrast. However, microwave wavelength is much longer which brings about lower spatial resolution ratio of pure microwave imaging, as well as microwave intercoupling disturbance can not be solved and design requirement of microwave receiving antennae/array is rigid extraordinarily, so high-quality microwave imaging of biological tissues has more difficulties in implementation technique.MTCT system can be seemed as ultrasound imaging induced by microwave. Lower ultrasound wavelength brings higher spatial resolution ratio of ultrasound imaging. MTCT not only has the capability to distinguish different tissues that microwave imaging has, but also higher spatial resolution ratio that ultrasound imaging has. And MTCT system can be portable and low-cost easily using modem electronic technique and customized microwave source.MTCT provides anatomical structural information, as well as certain physiological and biochemical characteristics such as tissue permittivity, conductivity, wave sound conductive rules andmicrowave absorbed-dose. Combined with experimental results of biological spectroscopy, it is expected to be a low-price and effective way as functional imaging.Absorbed-dose differs greatly because of different water content in tissues, especially between normal tissues and cancer in which water content and metabolism is different specially, so MTCT images have better image contrast, and it's image resolution ratio can reach to millimeter level so as to be used for early prediction for malignant tumor.This article studies other biological tissues MTCT technology in the world, and researches on it when introducing modern microelectronic technique, computer and digital signal processing.This study has done several research works below:1. Summarize the research progress about MTCT around the world.2. Research on implementation plan of MTCT experimental system, and bring forward the research method to implement it.3. Design for MTCT experimental plan, and do some relevant experimental researches.4. Preliminarily deal with experimental data and analyze the factors affecting image quality, moreover, put forward relevant steps improved.The following achievements have been obtained by the researchof MTCT technology.1. Design for the research plan of MTCT experimental system and put forward the research method to implement it. It isfor the first time to set up MTCT experimental platform in domestic research area.2. Design for high-frequency wideband amplifier circuit...
|
PDF Full Text Request