Efficient analysis of dielectric materials in coupled RF coil configurations

Abstract

MRI at high fields requires new approaches to RF coil design to maximize RF performance. Over the past years, various technologies have been developed, ranging fromactive control via parallel RF transmission (pTx), to passive approaches using dielectric materials. Previous work also indicates that the combination of both can yield furtherimprovements.1,2 However, the analysis of a dielectric shim in resonant coil structures such as surface arrays can involve long simulation times due to mutual coupling. Thisimpedes a constructive analysis on the design of the dielectric in such scenarios.A domain decomposition method has previously been presented which reduces the computational domain to that of the dielectric shim, allowing for much faster evaluation of itseffect.3 This approach is especially powerful in a decoupled scenario in which the coil’s current distribution is minimally affected by the dielectric. In this work, we extend thedomain decomposition method using circuit co-simulation techniques to account for tuned coil models as well as array configurations. Examples are shown for a tuned 7T birdcageanalysis and a four-channel dipole array design study.