An Inverse Methodology for High Frequency RF Coil Design with De-emphasized B1 field

B. Xu, B. K. Li, S. Crozier, F. Liu, Q. Wei School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, Queensland, Australia INTRODUCTION: High magnetic field (frequency) MRI technology has brought considerable engineering challenges in the form of ancillary hardware, including RF resonators. Studies in high frequency MRI have shown significant interactions between the RF (B1) field and biological loads [1]. Theoretical analyses and experimental results have also shown that, although the RF coils operated very well without loading, large distortions can be observed in MR images of larger biological samples [1, 2]. This necessitates the design of new types of high frequency RF coils considering the loading effect. The inverse method combined with Method of Moment has been introduced and described by Fujita et al. [4] and Lawrence, et al. [5] and the design concept presented here is an inverse method with de-emphasized B1 target fields. The de-emphasis method has been proved to be an effective strategy for high frequency RF coil design [3]. As inverse methods for RF coil design can prescribe and pre-set the target B1 fields in the DSV, we can therefore potentially include an estimate of the loading influences and de-emphasize the B1 field to counteract the resultant higher B1 strength in the centre of loads. In this work, the combination of both methods has been implemented, and FDTD simulations at 4T demonstrate that the method improve the B1 homogeneity compared with traditional transmitter coils.