【作者】 宁瑞鹏；

【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

【摘要】 磁共振成像技术诞生于1973年，作为一种对人体无害、无电离辐射的诊断工具，它不仅适合作结构成像，还可以进行功能性成像，因而与X射线、CT、超声成像和PET一道成为今天最常用的医学成像技术。频率源和梯度线圈是磁共振成像系统中的核心部件，本文对这两部分的设计进行了研究。 本文主要包括以下内容： 一、介绍磁共振成像的原理和磁共振成像系统的组成。原理部分介绍了核磁共振基本原理、空间编码的原理。系统组成部分介绍了磁体系统、谱仪系统和计算机系统。 二、梯度线圈。首先介绍了梯度线圈的设计方法，包括分离绕线法、分布绕线法，进一步分布绕线法中的矩阵反转、目标场、最小化磁能和流函数等技术。然后讨论了涡流问题，介绍了磁共振成像系统中的涡流补偿技术，包括加抗涡流板、预加重和自屏蔽线圈。详细介绍了双平面小型梯度线圈的设计。 三、全功能数字频率源。首先介绍了直接数字合成技术，比较其与传统频率合成技术的优劣。然后给出了频率源的硬件结构。由于采用了基于PCI总线的结构，因此对PCI总线和接口器件进行了介绍。最后给出了电气性能的测试结果和在一体化磁共振成像谱仪中应用的结果。更多还原

【Abstract】 Magnetic resonance imaging (MRI) is a tool of non-invasive and non-ironic, which appeared in 1973. MRI has been widely applied to structural and functional imaging, and has become a routine medical imaging technique with X-ray, CT, ultrasonic imaging and PET. In this thesis, frequency source and gradient coils are developed in detail, which are key components in MRI scanner.The main contents of the thesis include:The theory of MRI is introduced briefly, including nuclear magnetic resonance (NMR) and special encoding. The structure of MRI scanner is described, which consists of magnet subsystem, spectrum subsystem and computer subsystem.The design of gradient coils is reviewed. Tow kinds of gradient coils------discrete winding coils and distributed winding coils, are referred. The latter is described in detail, which applies several kinds of optimizations, such as matrix inversion method, target field method, minimum energy, stream function method, and so on. Eddy current must be considered. Traditional reducing eddy current techniques are compared, including anti-eddy-current board, pre-emphasis. current and self-shielded coils. The design of bi-planar mini gradient coil is described in detail.Finally, the complete digital frequency source is introduced. In this part, the direct digital synthesis technique is compared to traditional frequency synthesis techniques. PCI bus technique and PCI interface chip are referred. The structure of the frequency source is described. Results of performance test and application in the integrated MR spectrometer are given.更多还原