Parasitic capacitance in MRI coil arrays: Models and application to array decoupling

The role of capacitive coupling in MRI RF coils has not been studied extensively largely because of the lack of comprehensive models in the literature. At higher MRI frequencies capacitive coupling greatly impacts coil coupling and therefore cannot be neglected. We provide a model that takes into account the distributed nature of the mutual and series capacitance on coils. It correctly predicts impedance variation due to parasitic and intentional mutual capacitance. In addition, the fitted capacitance is shown to depend strongly on substrate and phantom permittivity, while being mostly invariant to changes in frequency. A method of completely eliminating mutual impedance between coils results from this investigation.