Synopsis

I will present some key tools for simulation of RF coils. First, I will review the three main types of EM solver: Finite difference time domain, finite element modeling and integral equation. I will introduce the co-simulation method, a powerful method for tuning, matching and decoupling of coil that requires a minimum number of EM solves. I will then present a simulation study that aims to find the ideal pTx coil for 3T body and head imaging. Finally, I will present our recent work on ultra-fast SAR calculation as the patient lies in the scanner for individualized SAR prediction.

Summary

FDTD, FEM or IE; which to choose? I will weigh the pros and cons of each EM solver and will introduce the co-simulation method for fast tuning, matching and decoupling in simulation. At the end of this talk, you will be ready to simulate any coils with confidence!

Take home messages

1) EM solvers have different strengths and weaknesses, so one needs to choose the right one for the job at hand.
2) Unless your coil has a single port and you don’t mind long simulation times, use the co-simulation for fast tuning, matching and decoupling.
3) FDTD is good to quickly evaluate the broadband response of the coil, since it is a time-domain simulation (frequency response computed in a single solve).
4) FDTD is naturally compatible with voxel body models, which is a major advantage.
5) FEM with tetrahedron discretization is an extremely powerful adaptive mesh strategy, that allows simulation of widely different geometrical scales in a single model (microns to meters) without paying a high computation price (computation time increases linearly with the number of elements, not quadratically like FDTD).
6) FEM can compute multi-port system in a single solve (FDTD requires N-solves for an S-port system).
7) MARIE (Magnetic Resonance Integral Equation) is a powerful coupled surface integral equation / volume integral equation solver that allows modeling thin conductors and voxel body models.
8) MARIE is fast.
9) For pTx coils: Use an FEM solver and a powerful circuit simulator (ADS if available).
10) For birdcage coils: FDTD works fine here since there are few capacitors values to optimize and we generally have a good idea of their values. Many body models available for FDTD (voxels), which makes it practical to study population SAR (mean +/- std. dev.).
11) For Rx coils: Use MARIE for this application, which can be more easily batched and is faster than other tools.

Acknowledgements

No acknowledgement found.

References

No reference found.