Radiofrequency (RF) coils for use in MRI can have a significant effect on both the signal-to-noise-ratio of MR images and the specific absorption rate inside the biological sample. In the past, prototypes were constructed and tested to investigate the performance of the RF coils and often required several iterations to achieve an acceptable result. However, with the advancement in computational electromagnetic techniques, RF coil modelling has now become the modus operandi of coil design because it can produce accurate numerical results, thus reducing the time and effort spent in designing and prototyping RF coils. Two hybrid methods -method of moments (MoM)/finite difference time domain (FDTD) and MoM/finite element method (FEM) - for RF coil modelling are presented herein. The paper provides a brief overview of FDTD, FEM and MoM. It discusses the hybridisation of these methods and how they are integrated to form versatile techniques. The numerical results obtained from these hybrid methods are compared with experimental results from prototype coils over a range of operating frequencies. The methods are then applied to the design of a new type of phased-array coil - the rotary phased array. From these comparisons, it can be seen that the numerical methods provide a useful aid for the design and optimisation of RF coils for use in MRI.

This article introduces a new concept for spin excitation and signal acquisition in magnetic resonance imaging (MRI) using rapid rotation of a single radiofrequency (RF) coil about a sample. A rotating RF coil system was constructed for 2 and 4.7 Tesla imaging. The acquired images of biological specimens were comparable to those of a conventional RF coil system. This approach may obviate the need for multiple channels and intricate RF decoupling of many coils, which impede the progress of multichannel array technology. It is hoped that hardware advantages of coil rotation and the additional parameter of rotational velocity will initiate advances in MRI through the development of new sequences and methods.

Accurate, computationally intensive numerical algorithms have become necessary to handle the increasing complexity of electromagnetic problems in biological applications. In this work, a high performance hybrid - MoM/FDTD approach is presented for electromagnetic analysis and design applications in microwave breast tumor detection. The proposed algorithm is based on Huygen's equivalent surface methods. The simulation study of a bow-tie antenna-breast phantom interaction demonstrates the efficacy of the proposed algorithm and suggests that, with further development, this hybrid scheme would be a useful tool in the continued development of microwave imaging for breast cancer.