Birdcage coils: Equivalent capacitance and equivalent inductance

Birdcage coil is extensively used in MR systems thanks to its possibility to provide high signal-to- noise ratio and high radiofrequency magnetic field homogeneity that guarantee a large field of view. This work describes how to schematize the birdcage coil in terms of an equivalent inductance and an equivalent capacitance, whose knowledge can be useful for coil design and characterization. In particular, the knowledge of equivalent capacitance and equivalent inductance permits to estimate theoretically coil resonant frequency, quality factors and matching circuit capacitor values in a quick way, while workbench tests permit to estimate coil resistance and sample-induced resistance. The presented theory is validated for both lowpass and highpass birdcage coils.by using literature data.