Payne Komlan, Bhosale Aditya Ashok, Zhang Xiaoliang
Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY 14260, USA.
Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY 14260, USA; Department of Electrical Engineering, State University of New York at Buffalo, Buffalo, NY 14260, USA.
J Magn Reson. 2023 Aug;353:107498. doi: 10.1016/j.jmr.2023.107498. Epub 2023 Jun 5.
In contrast to linearly polarized RF coil arrays, quadrature transceiver coil arrays are capable of improving signal-to-noise ratio (SNR), spatial resolution, and parallel imaging performance. Owing to a reduced excitation power, a low specific absorption rate can also be obtained using quadrature RF coils. However, due to the complex nature of their structure and their electromagnetic properties, it is challenging to achieve sufficient electromagnetic decoupling while designing multichannel quadrature RF coil arrays, particularly in ultra-high fields. In this work, we proposed a double-cross magnetic wall decoupling for quadrature transceiver RF arrays and implemented the decoupling method on common-mode differential mode quadrature (CMDM) quadrature transceiver arrays at an ultrahigh field of 7 T. The proposed magnetic decoupling wall, comprised of two intrinsically decoupled loops, is used to reduce the mutual coupling between all the multi-mode currents present in the quadrature CMDM array. The decoupling network has no physical connection with the CMDMs' resonators, which provides less design constraint over size-adjustable RF arrays. To validate the feasibility of the proposed cross-magnetic decoupling wall, systematic studies on the decoupling performance based on the impedance of two intrinsic loops are numerically performed. A pair of quadrature transceiver CMDMs is constructed along with the proposed decoupling network, and their scattering matrix is characterized using a network analyzer. The measured results indicate that all the current modes from coupling are simultaneously suppressed using the proposed cross-magnetic wall. Moreover, field distribution and local specific absorption rate (SAR) are numerically obtained for a well-decoupled 8-channel quadrature knee-coil array.
与线性极化射频线圈阵列相比，正交收发线圈阵列能够提高信噪比（SNR）、空间分辨率和并行成像性能。由于激励功率降低，使用正交射频线圈还可获得较低的比吸收率。然而，由于其结构和电磁特性的复杂性，在设计多通道正交射频线圈阵列时，尤其是在超高场中，实现足够的电磁去耦具有挑战性。在这项工作中，我们提出了一种用于正交收发射频阵列的双交叉磁壁去耦方法，并在7T超高场的共模差模正交（CMDM）正交收发阵列上实现了该去耦方法。所提出的磁去耦壁由两个本质上解耦的回路组成，用于减少正交CMDM阵列中存在的所有多模电流之间的相互耦合。去耦网络与CMDM的谐振器没有物理连接，这为尺寸可调的射频阵列提供了较少的设计约束。为了验证所提出的交叉磁去耦壁的可行性，基于两个固有回路的阻抗对去耦性能进行了系统的数值研究。构建了一对正交收发CMDM以及所提出的去耦网络，并使用网络分析仪对其散射矩阵进行了表征。测量结果表明，使用所提出的交叉磁壁可同时抑制所有耦合电流模式。此外，还通过数值计算得到了一个解耦良好的8通道正交膝部线圈阵列的场分布和局部比吸收率（SAR）。
