基于材料变密度法的MRI匀场线圈设计  

Design of MRI shim coils based on material variable density method

作　　者：曲洪一 王秋良[1,2] 王耀辉 秦朗 QU Hong-yi;WANG Qiu-liang;WANG Yao-hui;QIN Lang(Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China;University of Chinese Academy of Sciences, Beijing 100049, China)

机构地区：[1]中国科学院电工研究所,北京100190 [2]中国科学院大学,北京100049

出　　处：《电工电能新技术》2019年第5期84-89,共6页Advanced Technology of Electrical Engineering and Energy

基　　金：国家自然科学基金项目(51777205; 11745005; 51477167)

摘　　要：核磁共振成像系统磁场的均匀度对成像的质量起着决定性作用,采用匀场线圈抵消磁场球谐波分量是提高磁场均匀度的有效手段。采用材料变密度法设计了一阶轴向匀场线圈,首先将设计区域划分为足量的网格,网格的材料密度作为设计变量,利用有限元法组装电导矩阵,求解设计区域的电流分布,建立了材料密度分布与磁场的关系。其次,将磁场均匀度作为优化目标,采用优化准则法对密度变量进行优化,得到了满足约束条件的最优解。最后,利用流函数方法将材料分布离散为导线,得到了线圈的拓扑结构。相比于室温有源匀场线圈设计常用的解析法,变密度法能够有效地利用材料,充分发挥材料特性,可设计出更高性能匀场线圈。The uniformity of the magnetic field of the MRI system plays a decisive role in the quality of the imaging.It is an important remedy to use the shim coils to correct the specific field harmonic component of the field. In this paper,the first-order axial shim coil is designed by the variable density method of material distribution. Firstly,the design area is divided into a sufficient number of meshes and material density distributed in every mesh is set as a variable. To solve the current distribution and the relationship between the material distribution and the magnetic field,the conductance matrix is assembled by FEM. Secondly,the uniformity of magnetic field is taken as the optimization target,and the design variable,i.e. material distribution,is computed by the optimization criteria method,and the optimal solution that satisfies the constraint condition is obtained. Finally,the stream function is used to discretize the material distribution into wires,and the topology of the coils is obtained. Compared with the common analytical method for designing room temperature shim coil,the variable density method can effectively utilize materials and fully utilize material properties to design high performance shim coils.

关 键 词：MRI 匀场线圈 变密度法 有限元 优化准则法 流函数 

分 类 号：TM153[电气工程—电工理论与新技术]