In this work a 21 MHz radiofrequency (RF) exposure system was designed, constructed and evaluated as a testing platform for MRI device safety. The exposure system consisted of a birdcage coil powered in quadrature by a power system consisting of a hybrid coupler, a power splitter, a phase shifter and two baluns. The birdcage coil was designed as a low‐pass 16 rung coil. Both the coil and the power system were fabricated as printed circuit boards with a copper thickness of 205.7 μm and a G10 substrate thickness of 581.7 μm. The birdcage was assembled by wrapping the copper clad G10 inside of an acrylic tube. A shield for the coil was created as a cylindrical ground plane with a diameter of 39.7 cm. The birdcage and the power system were simulated in ADS and EMPro, Keysight Technologies Inc. both as lumped elements and using full wave 3D simulations. Simulation results were compared to measurements of the produced components to validate each component and entire system. In addition, a 3D magnetic field probe was developed to measure and compare the fields to analytical and numerical calculations.

中文翻译：

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头戴式21 MHz射频暴露系统的设计和实现

在这项工作中，设计，构建和评估了21 MHz射频（RF）曝光系统，作为MRI设备安全性的测试平台。曝光系统由一个鸟笼线圈组成，该鸟笼线圈由一个由混合耦合器，一个功率分配器，一个移相器和两个巴伦组成的功率系统进行正交供电。鸟笼线圈设计为低通16档梯级线圈。线圈和电源系统都被制成印刷电路板，铜厚度为205.7μm，G10基板厚度为581.7μm。通过将覆铜箔的G10包裹在丙烯酸管的内部来组装鸟笼。将线圈的屏蔽创建为直径为39.7 cm的圆柱形接地平面。鸟笼和电源系统在Keysight Technologies的ADS和EMPro中作为集总元件并使用全波3D仿真进行了仿真。将仿真结果与生产组件的测量结果进行比较，以验证每个组件和整个系统。此外，还开发了3D磁场探头，用于测量磁场并将其与分析和数值计算进行比较。