Effect of tuning capacitor placement on mutual coupling for MRI array coils

Abstract

Mutual coupling is an important issue in RF coil array design for MRI. In this study, the dependence of mutual coupling behavior among RF coil array elements on the tuning capacitor placement is specially investigated at different field strengths. For phased arrays with different tuning capacitor configurations, the degree of mutual coupling is estimated by measuring parameters S11 and S12 using Advanced Design System (ADS) simulation and bench measurements. The simulation agrees well with experiment results and shows that the mutual coupling behavior of different configurations varies notably with the resonant frequency. Specifically, at frequencies lower than 64 MHz, the placement of one or two concentrated capacitors suffers less mutual coupling than that of four evenly distributed capacitors around the coil loop; whereas at frequencies higher than 128 MHz, the opposite is observed. This interesting phenomenon provides guidance on minimizing the mutual coupling for coil array design. © 2006 Wiley Periodicals, Inc.