Head-only 21 MHz radiofrequency exposure system design and implementation

摘要

In this work a 21 MHz radiofrequency (RF) exposure system was designed,constructed and evaluated as a testing platform for MRI device safety. Theexposure system consisted of a birdcage coil powered in quadrature by apower system consisting of a hybrid coupler, a power splitter, a phaseshifter and two baluns. The birdcage coil was designed as a low-pass16 rung coil. Both the coil and the power system were fabricated as printedcircuit boards with a copper thickness of 205.7 μm and a G10 substratethickness of 581.7 μm. The birdcage was assembled by wrapping the copperclad G10 inside of an acrylic tube. A shield for the coil was created as acylindrical ground plane with a diameter of 39.7 cm. The birdcage and thepower system were simulated in ADS and EMPro, Keysight TechnologiesInc. both as lumped elements and using full wave 3D simulations. Simulationresults were compared to measurements of the produced componentsto validate each component and entire system. In addition, a 3D magneticfield probe was developed to measure and compare the fields to analyticaland numerical calculations.