Simulation of equivalent circuits for MRI surface coils

Optimisation of RF coils for Magnetic Resonance Imaging is normally a combination of experience and theory. Therefore, the ability to measure the key coil parameters is very important to obtain the best performance of a coil design. However, simulating an equivalent circuit of the coil can provide us guidelines to construct efficient coil prototypes. Coil parameters such as resonant frequency and quality factor can be simulated using an equivalent RLC circuit of a surface coil. The SPICE OPUS simulator was used to perform the simulation of the equivalent circuit of two coils: a square-shaped coil and a single-loop coil. Spectra of the frequency response represented as the reflection coefficients of the coils were obtained. Quality factors are computed from these spectra and compared. Results showed a good agreement with the values predicted by theory for both type of coils.