Budé Lyanne M I, Vat Koen, Voogt Ingmar J, Zivkovic Irena, Raaijmakers Alexander J E
Department of Electrical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.
Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.
Magn Reson Med. 2025 Jun;93(6):2667-2679. doi: 10.1002/mrm.30464. Epub 2025 Feb 18.
In comparison to dipole antennas, the coax monopole antenna (CMA) diminishes the possibility of cable-coil coupling. This greatly facilitates cable routing in spatially restricted environments, such as head coil arrays. With the outlook of a 14T MRI system being installed at the Donders Center in Nijmegen, the Netherlands, this study aims to optimize the CMA for an eight-channel head array at 14 T and compare its performance with an array of fractionated dipole antennas.
Both antenna designs were optimized for head imaging at 14 T using single-channel finite-difference time-domain (FDTD) simulations at 596 MHz. Eight-channel simulations were then used on a human model to evaluate and specific absorption rate (SAR) distributions. For both antenna types, prototype arrays were built by placing eight elements on a 26-cm-diameter cylindrical holder. These prototype arrays were used for S and S evaluation.
The optimal dimensions of the CMA were a length of 20 cm and a gap position of 4 cm. The fractionated dipole was optimal for a length of 25 cm. Evaluation of 100 000 random shims revealed that the CMA performs with lower SAR efficiency, although the SAR efficiencies are similar in CP mode. Measured S and S levels were both lower for the CMA.
The coax monopole would be an excellent candidate for head coil arrays at 14T MRI. Although the CMA is expected to perform with lower SAR efficiency than the fractionated dipole, its single-ended design will facilitate elements placement and cable-routing, especially in a spatially restricted environment.
与偶极天线相比，同轴单极天线（CMA）降低了电缆-线圈耦合的可能性。这极大地方便了在空间受限环境（如头部线圈阵列）中的电缆布线。鉴于荷兰奈梅亨的东德斯中心将安装一台14T磁共振成像（MRI）系统，本研究旨在优化14T下八通道头部阵列的CMA，并将其性能与分段偶极天线阵列进行比较。
两种天线设计均针对14T下的头部成像进行优化，在596MHz频率下使用单通道时域有限差分（FDTD）模拟。然后在人体模型上进行八通道模拟，以评估比吸收率（SAR）分布。对于两种天线类型，通过将八个元件放置在直径26cm的圆柱形支架上构建原型阵列。这些原型阵列用于S和S评估。
CMA的最佳尺寸为长度20cm，间隙位置4cm。分段偶极子的最佳长度为25cm。对100000次随机匀场的评估表明，CMA的SAR效率较低，尽管在圆极化（CP）模式下SAR效率相似。CMA测量的S和S水平均较低。
同轴单极天线将是14T MRI头部线圈阵列的极佳候选方案。尽管预计CMA的SAR效率低于分段偶极子，但其单端设计将便于元件放置和电缆布线，特别是在空间受限的环境中。
