一种实用的使用铁磁材料匀场的开放式超导MRI磁体的优化方法

摘要

Magnetic resonance imaging (MRI) system is an important medical diagnostic equipment.We present a practical method for optimizing the shapes of ferromagnetic materials to generate a target static magnetic field for open superconducting MRI magnet.The method integrates improved Multi - Input - Multi - Output (MIMO) negative feedback control theory with the finite element method (FEM) to calculate nonlinear ferromagnetic material configurations,subjecting to high magnetic field homogeneity constraints for MRI systems containing nonlinear ferromagnetic yoke structures.It should be noted that the initial condition of the material shape isnt critical for convergence.In particular,the method is well suited for magnet design problems necessitating large three - dimensional FEM models which can be realized easily and quickly.We demonstrate this method works well with a test 2D axisymmtric yoked bi-planar magnet.%磁共振成像(MRI)系统是一种重要的医学诊断设备.作者提出了一种针对使用铁磁材料匀场的开放式超导MRI主磁场匀场的优化方法.在这种方法中,为了使这种包含非线性铁磁轭结构的MRI磁体产生高均匀度的磁场,集成了改进的多输入多输出负反馈控制理论和有限元方法,来计算匀场区非线性铁磁材料的形状.特别要指出的是,这种方法对初始值的要求不高,一定可以收敛,如果配置得当,可以快速收敛.另外,由于收敛速度快,这种方法也可以应用于大型的非轴对称三维模型优化分析.在文中,作者在一个二维轴对称磁体模型上测试了该方法,表现良好.