MRI中低噪声前置放大器的研制及磁共振图像非均匀场校正算法研究

发布时间：2018-05-18 07:24

本文选题：磁共振成像 + 低噪声　；参考：《南京理工大学》2017年硕士论文

【摘要】：磁共振成像(MRI)技术已经逐渐成为医学图像检测领域中的重要手段,并且在其他领域也有充分应用。磁共振图像的好坏会对医学临床诊断、物体特性分析等多方面应用造成极大的影响,致力于获取好的磁共振图像一直是磁共振成像探测领域的研究重点。低噪声前置放大器作为磁共振接收机系统的重要组成部分直接影响着磁共振图像的好坏。本文首先对低场磁共振系统中的低噪声前置放大器的相关设计理论进行详细的介绍,然后利用Keysight公司的ADS仿真设计软件完成低场磁共振系统中的低噪声前置放大器的仿真设计,同时根据仿真设计结果完成低噪声前置放大器的实物制作与调试工作,最后利用Keysight公司矢量网络分析仪E5061B和噪声系数分析仪N8974A完成对放大器性能参数的测量并与同类商用磁共振系统中的前置放大器进行了对比,实际测量结果显示本文设计的低噪声前置放大器增益达到30dB、噪声系数约为0.5dB,达到了与商用磁共振系统的前置放大器性能相当的水平,甚至优于部分商用产品。最后将完成的实物应用于磁共振成像系统中完成水模的磁共振成像实验,成像效果良好,进一步验证了本文所设计的低噪声前置放大器性能稳定可靠。此外,针对多通道接收线圈给磁共振图像带来的非均匀性问题,本文对磁共振图像中的非均匀场校正算法进行了研究。首先介绍了基于滤波和非参数的两种传统的非均匀性校正算法,然后采用改进的基于同态滤波的能量最小化方法对磁共振图像非均匀场校正,对校正后图像进行了定性和定量分析,并与基于滤波和非参数的校正图像进行了对比。结果表明本文采用的算法能够有效校正磁共振图像的非均匀场,在目标区域内具有更高的均匀性,显著减少背景干扰,具有更高的辨识度,并且校正结果优于另外两种算法。
[Abstract]:Magnetic resonance imaging (MRI) technology has gradually become an important means in the field of medical image detection, and has been fully applied in other fields. The quality of magnetic resonance images will have a great impact on the medical clinical diagnosis, object characteristics analysis and other applications. It has been the focus of research in the field of magnetic resonance imaging detection to obtain good magnetic resonance images. As an important part of magnetic resonance receiver system, low noise preamplifier directly affects the quality of magnetic resonance image. In this paper, the related design theory of low noise preamplifier in low field magnetic resonance system is introduced in detail, and then the simulation design of low noise preamplifier in low field magnetic resonance system is completed by using ADS simulation design software of Keysight company. At the same time, according to the result of simulation design, the physical fabrication and debugging of low-noise preamplifier are completed. Finally, the Keysight vector network analyzer E5061B and the noise coefficient analyzer N8974A are used to measure the performance parameters of the amplifier and compared with the preamplifier in the similar commercial magnetic resonance system. The actual measurement results show that the gain of the low noise preamplifier designed in this paper is 30 dB and the noise coefficient is about 0.5 dB, which is equivalent to the preamplifier performance of the commercial magnetic resonance system, and even better than some commercial products. Finally, the completed physical object is applied to the magnetic resonance imaging experiment of the water mode in the magnetic resonance imaging system, and the imaging effect is good, which further verifies the stability and reliability of the low noise preamplifier designed in this paper. In addition, aiming at the nonuniformity of magnetic resonance image caused by multi-channel receiving coil, the nonuniform field correction algorithm in magnetic resonance image is studied in this paper. Firstly, two traditional nonuniformity correction algorithms based on filtering and non-parameter are introduced, and then an improved energy minimization method based on homomorphic filtering is used to correct the nonuniform field of magnetic resonance images. The corrected images are qualitatively and quantitatively analyzed and compared with the filtered and nonparametric corrected images. The results show that the proposed algorithm can effectively correct the nonuniform field of the magnetic resonance image, have higher uniformity in the target region, reduce the background interference significantly, and have a higher identification degree, and the correction results are better than the other two algorithms.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN722.71;TP391.41

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