新型人工电磁介质在磁共振成像中的应用研究

发布时间：2018-09-15 07:10

【摘要】：新型人工电磁介质是一种具有一些天然材料所不具备的超常物理性质的人工复合材料,其电磁特性主要是由结构而不是由其构成材料所决定。近数十年来,其在左手材料、完美透镜、慢波、电磁器件以及隐性材料等方面的应用得到很多的理论和实验研究。核磁共振成像技术(MRI)在脑科学、神经生理学和认知神经科学上有着重要的应用前景。本论文研究具有等效负磁导率的人工电磁超透镜在核磁共振医学成像中的应用。论文主要涉及以下几方面的研究：首先研究基本的开路环流共振结构单元的电磁传输特性,我们提出了一种基于开路环流共振单元外开环内闭环的基本结构的平板电磁超透镜。利用均一化理论研究其电磁响应,得到了等效磁导率为负的电磁超透镜。在理论上研究其对人体组织中肿瘤细胞的高分辨探测和定位扫描成像,并指出平板电磁超透镜在医学成像中的潜在应用。其次,我们提出了一种基于单个开路环流共振单元并在开口处加载非磁性电容的弯曲圆柱形电磁超透镜结构,并对超透镜的聚焦特性进行了深入的探讨。在临床实验上,该器件在现有的GE 1.5 T MRI系统下对表面线圈信号有良好的聚焦效果,有效地提高了表面线圈的探测深度。同时由于电磁超透镜本身的弯曲结构特点,我们指出其在超分辨成像上的应用,该器件有效地降低各个电磁波源的信号干扰因而可以应用于MRI系统中的并行成像。人工电磁介质超透镜由于其结构本身的离散特点,对磁共振成像的信噪比有一定的减弱,后期将着重优化结构。最后总结了全文,并对未来的研究提出展望。
[Abstract]:The new artificial electromagnetic medium is a kind of artificial composite material which has some supernormal physical properties which are not possessed by some natural materials. The electromagnetic properties of artificial electromagnetic medium are mainly determined by the structure rather than the composition material. In recent decades, its applications in left-handed materials, perfect lenses, slow waves, electromagnetic devices and recessive materials have been studied in theory and experiment. Magnetic resonance imaging (MRI) technology has important applications in brain science, neurophysiology and cognitive neuroscience. In this paper, the application of artificial electromagnetic superlens with equivalent negative permeability in NMR medical imaging is studied. The main contents of this paper are as follows: firstly, the electromagnetic transmission characteristics of the basic open circuit resonant structure unit are studied. We propose a flat plate electromagnetic superlens based on the basic structure of the open loop inner closed loop outside the open loop resonance unit. By using the homogenization theory, the electromagnetic superlens with negative equivalent permeability is obtained. The high resolution detection and localization scanning imaging of tumor cells in human tissues are studied theoretically, and the potential application of plate electromagnetic superlens in medical imaging is pointed out. Secondly, we propose a curved cylindrical electromagnetic superlens structure based on a single open-loop resonant element and load a non-magnetic capacitance at the opening. The focusing characteristics of the superlens are discussed in depth. In clinical experiments, the device has a good focusing effect on the surface coil signal under the existing GE 1.5 T MRI system, and effectively improves the detection depth of the surface coil. At the same time, due to the bending structure of the electromagnetic superlens, we point out its application in super-resolution imaging, the device can effectively reduce the signal interference of various electromagnetic sources, so it can be used in the parallel imaging of MRI system. Due to the discrete characteristics of the structure of artificial electromagnetic medium superlens, the signal-to-noise ratio (SNR) of magnetic resonance imaging is weakened to a certain extent, and the structure will be optimized at the later stage. Finally, the paper summarizes the full text and puts forward the prospect of future research.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：R445.2

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