Full-wave simulation of radio frequency resonators for MRI: Strip and wire conductors inductance estimation

In magnetic resonance (MR) systems, radio frequency (RF) resonators are key components in both the study transmission and receiving phases. The design of home-made, organ-specific RF resonators can be a constraint in many research projects. Such RF resonators can be built by using conductors with different cross-sectional shapes (circular wire and flat strip, hereafter named "wire" and "strip," respectively), which strongly affects the conductor resistance and then the RF resonator performance in terms of quality factor and signal-to-noise ratio, especially for low frequency MR experiments. However, both conductor types are used in different MR applications. For the design of RF resonators, it is necessary to evaluate the conductor inductance in order to define the capacitor's value for tuning the RF resonator at the desired Larmor frequency. To avoid time-consuming trial-and-error approaches and achieve a fast RF resonator-prototyping process, it is necessary to perform a priori RF resonator inductance estimation. This paper proposes the application of a numerical full-wave method based on the finite-difference time-domain algorithm to help the RF resonator builder in the choice of the conductor cross section for maintaining the same RF resonator inductance value. Simulation results accuracy was validated with workbench tests performed on some RF resonator prototypes.