FEM Based design and simulation tool for MRI birdcage coils Including eigenfrequency analysis

Abstract

Radio Frequency (RF) birdcage coils are widely used in Magnetic Resonance Imaging (MRI). Before the actual construction of the coil, not only calculating the capacitance value, which is necessary for the coil to resonate at the desired frequency, but also modeling the birdcage coil in a 3D simulation environment and making electromagnetic analysis in the volume of interest have importance in terms of observing the resonance behavior of the coil, electromagnetic field distributions inside the coil, or specific absorption rate (SAR) distribution for any object. For this purpose, we have made two different electromagnetic analyses of low-pass and high-pass birdcage coils in COMSOL Multiphysics. These are frequency domain analysis and eigenfrequency analysis. We have also developed a software tool using MATLAB® to make these electromagnetic analyses easily and according to the userspecified parameters. Simulation results for these analyses are provided. For the experimental results, we have constructed a hand-made lowpass birdcage coil and measured the resonant modes of the coil for different capacitance values. Our eigenfrequency analysis tool calculates the resonant modes with high accuracy