Effect of RF coil excitation on field inhomogeneity at ultra high fields: A field optimized TEM resonator
Effect of RF coil excitation on field inhomogeneity at ultra high fields: A field optimized TEM resonator
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DOI：
10.1016/s0730-725x(01)00404-0
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发表时间：
2001-12-01
影响因子：
2.5
通讯作者：
Robitaille, PML
中科院分区：
文献类型：
--
作者：
Ibrahim, TS;Lee, R;Robitaille, PML
在这项工作中，利用计算方法来优化在8特斯拉的人的头部的存在下，由横向电磁（TEM）谐振器产生的场。通过使用经典的时域有限差分（FDTD）方法和TEM谐振器加载解剖学上详细的人的头部模型，分辨率为2 mm × 2 mm × 2 mm。头部模型是从三维MR图像开发的。为了解释线圈和组织之间的电磁相互作用，在模型的所有步骤（包括数值调谐和激励）中将线圈和头部视为单个系统。除了2、3、4、6和10端口激励之外，通过驱动24支柱TEM谐振器的所有可能端口（24）来利用天线阵列概念。结果表明，采用多端口变相位定幅激励或变相位变幅激励可以显著改善横向磁场的圆极化分量。(C)2001 Elsevier Science Inc. All rights reserved.
In this work, computational methods were utilized to optimize the field produced by the transverse electromagnetic (TEM) resonator in the presence of the human head at 8 Tesla. Optimization was achieved through the use of the classical finite difference time domain (FDTD) method and a TEM resonator loaded with an anatomically detailed human head model with a resolution of 2 mm X 2 mm X 2 mm. The head model was developed from 3D MR images. To account for the electromagnetic interactions between the coil and the tissue, the coil and the head were treated as a single system at all the steps of the model including, numerical tuning and excitation. In addition to 2, 3, 4, 6, and 10-port excitations, an antenna array concept was utilized by driving all the possible ports (24) of a 24-strut TEM resonator. The results show that significant improvement in the circularly polarized component of the transverse magnetic field could be obtained when using multiple ports and variable phase and fixed magnitude, or variable phase and variable magnitude excitations. (C) 2001 Elsevier Science Inc. All rights reserved.