磁共振成像仪线圈调谐模块的研究与设计电子与通信工程专业论文.docxVIP

ABSTRACTCoil ABSTRACT Coil as all important part of magnetic resonance imaging system，its performance directly effects the imaging quality．The resonance行equency and impedance are changed When different human body are loaded into the RF coil，it impact on the quality of imaging because of the degradation of signal to noise and quality factor， and the signal reflection will damage the power module．So it needs tuning when before or after imaging．Traditional tuning method is manual operation and displayed by computer,its slowly and not convenient．Design a manual tuning detection device what is convenient to observe is all improved scheme．Automatic tuning does not require the participation of people，and has a big improvement in tuning speed and accuracy． This paper first reviews the history and development of nuclear magnetic resonance，expounds the principle of nuclear magnetic resonance and magnetic resonance imaging，and brief introduce the system of magnetic resonance instruments including magnetic resonance spectrometer and magnetic resonance imaging． Then it analyzed the characteristics of L-section matching network，obtained matching area of C—C matching network，and analyzed the RF coil by this method． Expound the process of coil tuning by Smith chart and admittance chart． On the manual tuning detection module design，analyze S parameter matrix of directional couple，use the reflected voltage as a tuning light．Then introduce the working principle and circuit design of the power detector．The signal processing part is base on STM32，it mainly divides into three parts：the ADC sampling，data conversion and LCD display．Then testing and each part of the detection module． Finally，present the automatic tuning principle and system，design the matching network of automatic tuning．Put forward two kinds of algorithms that applied to the automatic tuning，expounds the main idea of two algorithms，and introduces the design of two kinds of algorithms that applied to the automatic Uming． 万方