Li S, Yang Q X, Smith M B
Department of Radiology (Center for NMR Research), Pennsylvania State University College of Medicine, Hershey 17033.
Magn Reson Imaging. 1994;12(7):1079-87. doi: 10.1016/0730-725x(94)91240-w.
Two-dimensional (2D) finite element analysis has been used to solve the full set of Maxwell's equations for the 2D magnetic field of radiofrequency (RF) coils. The field histogram method has been applied to evaluate and optimize the magnetic field homogeneity of some commonly used RF coils: the saddle coil, the slotted tube resonator, the multiple elements coil and the birdcage resonator, as well as the radial plate coil. Each coil model represents a cross-section of an infinitely long cylinder. The optimum configuration of each of these five RF coils is suggested. It was found that field homogeneity is more strongly dependent on the coil's window angle than on any other parameter. Additionally, eddy currents in the coil's conductive elements distort the current and magnetic field distribution. The frequency dependence of this eddy current distortion is analyzed and discussed.
二维（2D）有限元分析已被用于求解射频（RF）线圈二维磁场的麦克斯韦方程组。场直方图方法已被应用于评估和优化一些常用RF线圈的磁场均匀性：鞍形线圈、开槽管谐振器、多单元线圈、鸟笼谐振器以及径向平板线圈。每个线圈模型代表一个无限长圆柱体的横截面。提出了这五种RF线圈各自的最佳配置。研究发现，场均匀性对线圈的窗口角度的依赖性比对任何其他参数的依赖性更强。此外，线圈导电元件中的涡流会使电流和磁场分布发生畸变。对这种涡流畸变的频率依赖性进行了分析和讨论。
