【作者】 徐志坚；

【导师】 李鲠颖；

【作者基本信息】 华东师范大学 ， 无线电物理， 2006， 硕士

【副题名】1、基于PCI总线的模拟接收机 2、图像的小波降噪

【摘要】 核磁共振成像(MRI)技术在临床和科研应用中正发挥着越来越重要的作用。2003年的诺贝尔医学奖被授予了Paul C．Lauterbur和Peter Mansfield以表彰他们对MRI做出的重大贡献。MRI仪器的关键技术被少数国外大公司所掌握，仪器价格昂贵。因此有必要在国内开展MRI仪器技术方面的研究。本文后面的内容将讨论核磁共振成像仪中的接收机的设计，以及数据后处理过程中的图像降噪方法。 第一部分简单介绍了核磁共振成像的基本原理，以及MRI仪器的各个组成部分。其中包括脉冲序列发生器、射频发射单元、接收机单元和梯度发生单元。它们都采用了基于普通PC机的PCI总线。 第二部分介绍了核磁共振成像仪中的接收机单元，它是MRI谱仪中比较重要的部分。这部分内容讨论了一个低成本模拟接收机的设计过程。此接收机的核心是单片模拟接收芯片AD607，采用了基于PCI总线，以FPGA为主要逻辑控制中心的构架。文中描述了接收机的硬件结构，简介了卡上FPGA内部结构及FPGA内部控制逻辑的设计流程。最后进行实验并分析结果。 最后一部分内容是关于磁共振图像降噪的内容。主要介绍了小波变换的基本概念，及其在图像和信号处理中的应用以及几种常用的小波域去噪方法。然后，简单讨论核磁共振图像中噪声的特点。最后，结合磁共振图像的噪声特点给出两种去噪的方法。并且结合实验结果进行分析和总结。更多还原

【Abstract】 Magnetic Resonance Imaging (MRI) has become more and more important in clinical diagnostic and scientific researches. The Nobel Prize in Medicine (2003) was given to Paul C. Lauterbur and Peter Mansfield for their discoveries concerning magnetic resonance imaging. The key technique of MRI instruments is hold by several abroad companies, and this led to the high price of MR scanner. So the research of MRI instruments is necessary. The following content of this thesis is about an analog receiver for MR spectrometer based on PCI bus and wavelet based MR image denoising method.The first part introduce the basic principle of Magnetic Resonance Imaging and the structure of MRI spectrometer, which includes pulse sequence generator and compiler, RF unit,receiver unit and pulse field gradient unit. They’re all based on PCI bus.The second part is mainly about the receiver which is the core component of MRI spectrometer. A low cost design of an analog receiver use one-chip receiver IF Subsystem is described. FPGA is used for logic controlling on the card. The hardware structure and the logic control flow of the receiver are described in detail. The MRI experiment result is also given.Finally, wavelet-based noise removal for MR imaging is discussed. We introduce the wavelet transform and its application in signal and image processing. Useful wavelet-based denoising methods are also introduced. Then we analyse the characteristic of noise in MRI. At last, two denoising methods based on wavelet for MR imaging are described in detail, with the result of its application in MR imaging.更多还原