Distributed Capacitors for MR-Receive-Coils: Theory and Method.

MR coils are a crucial part in the receiving chain of an MRI. Their characteristics determine the signal-to-noise-ratio (SNR) as well as the quality of the illumination of the volume-of-interest (VOI), which is significantly reduced as the circumference of the conductor is comparable in size to the wavelength.A well-known countermeasure to this is the use of distributed capacitors on the circumference of conductor loops. Although this measure is mentioned in numerous works, there is no systematic framework to correctly determine the values of these capacitors. In this work a systematic framework for the analysis of distributed capacitors on conductor loops is established. This is achieved by a four-pole representation of the circular loop, which allows for a eigen-mode analysis to determine the correct values.Based on the results, an experimental method for determining the values is derived and validated in workbench measurements. This provides, for the first time, an easy-to-use method for determining the correct values of distributed capacitors.