C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.
Magn Reson Med. 2018 Mar;79(3):1781-1788. doi: 10.1002/mrm.26784. Epub 2017 Jun 20.
Dielectric resonator antenna (DRAs) are compact structures that exhibit low coupling between adjacent elements and therefore can be used as MRI transmit arrays. In this study, we use very high permittivity materials to construct modular flexible transceive arrays of a variable numbers of elements for operation at 7T.
DRAs were constructed using rectangular blocks of ceramic (lead zirconate titanate, ε = 1070) with the transverse electric (TE) mode tuned to 298 MHz. Finite-difference time-domain simulations were used to determine the B and specific absorption rate distributions. B1+ maps were acquired in a phantom to validate the simulations. Performance was compared to an equally sized surface coil. In vivo images were acquired of the wrist (four elements), ankle (seven elements), and calf muscle (16 elements).
Coupling between DRAs spaced 5 mm apart on a phantom was -18.2 dB compared to -9.1 dB for equivalently spaced surface coils. DRAs showed a higher B1+ intensity close to the antenna but a lower penetration depth compared to the surface coil.
DRAs show very low coupling compared to equally sized surface coils and can be used in transceive arrays without requiring decoupling networks. The penetration depth of the current DRA geometry means they are ideally suited to imaging of extremities. Magn Reson Med 79:1781-1788, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
介质谐振器天线 (DRA) 是一种紧凑的结构，其相邻单元之间的耦合较低，因此可用作 MRI 发射阵列。在这项研究中，我们使用非常高的介电常数材料来构建可灵活配置的、具有可变数量单元的收发一体阵列，以在 7T 下运行。
使用具有横向电场 (TE) 模式调谐至 298 MHz 的陶瓷（锆钛酸铅，ε=1070）矩形块构建 DRA。使用时域有限差分法模拟来确定 B 和比吸收率分布。在体模中采集 B1+图以验证模拟。将性能与同等大小的表面线圈进行比较。采集手腕（四个单元）、脚踝（七个单元）和小腿肌肉（16 个单元）的体内图像。
在体模上，彼此间隔 5mm 的 DRA 之间的耦合为-18.2dB，而同等间隔的表面线圈为-9.1dB。DRA 在靠近天线的地方显示出更高的 B1+强度，但与表面线圈相比，穿透深度更低。
与同等大小的表面线圈相比，DRA 显示出非常低的耦合，并且可以在收发一体阵列中使用，而无需使用去耦网络。当前 DRA 几何形状的穿透深度意味着它们非常适合于四肢成像。磁共振医学 79:1781-1788, 2018。© 2017 作者磁共振医学由 Wiley 期刊出版公司代表国际磁共振医学学会出版。这是在知识共享署名非商业许可下的许可条款下授予的许可，允许在任何媒介中使用、分发和复制原始作品，只要原始作品正确引用且不用于商业目的。
