Proposed radiofrequency phased-array excitation scheme for homogenous and localized 7-Tesla whole-body imaging based on full-wave numerical simulations
Proposed radiofrequency phased-array excitation scheme for homogenous and localized 7-Tesla whole-body imaging based on full-wave numerical simulations
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DOI：
10.1002/mrm.21139
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发表时间：
2007-02-01
影响因子：
3.3
通讯作者：
Ibrahim, Tamer S.
中科院分区：
文献类型：
--
作者：
Abraham, Roney;Ibrahim, Tamer S.
在这篇文章中，一个射频（RF）激励计划7特斯拉（T）的全身应用推导和分析使用时域有限差分（FDTD）方法。建议的激励方案和线圈（一个潜在的7 T全身横向电磁[TEM]谐振器设计）的重要特点，从操作和电磁的角度，进行了讨论。线圈工作模式的选择是非常规的;我们使用的不是典型的“均匀模式”，而是在低场应用中在线圈中心提供零场的模式。使用麦克斯韦方程的3D FDTD实现，我们证明了全身7 T TEM线圈（调谐到上述非常规模式并以优化的近场相控阵列方式激励）可以潜在地提供1）均匀的全切片（在三个轴向、矢状和冠状切片中展示）和2）3D局部（在心脏中展示）激励。由于在某些情况下，射频功率未被视为优化的一部分，因此通过全切片射频激励实现的显著改进是以射频功率要求大幅增加为代价的。Magn Reson Med 57：235-242，2007. (c)2007 Wiley-Liss，Inc.
In this article, a radiofrequency (RF) excitation scheme for 7-Tesla (T) whole-body applications is derived and analyzed using the finite difference time domain (FDTD) method. Important features of the proposed excitation scheme and coil (a potential 7T whole-body transverse electromagnetic [TEM] resonator design), from both operational and electromagnetic perspectives, are discussed. The choice of the coil's operational mode is unconventional; instead of the typical "homogenous mode," we use a mode that provides a null field in the center of the coil at low-field applications. Using a 3D FDTD implementation of Maxwell's equations, we demonstrate that the whole-body 7T TEM coil (tuned to the aforementioned unconventional mode and excited in an optimized near-field, phased-array fashion) can potentially provide 1) homogenous whole-slice (demonstrated in three axial, sagittal, and coronal slices) and 2) 3D localized (demonstrated in the heart) excitations. As RF power was not considered as a part of the optimization in several cases, the significant improvements achieved by whole-slice RF excitation came at the cost of considerable increases in RF power requirements. Magn Reson Med 57: 235-242, 2007. (c) 2007 Wiley-Liss, Inc.