RF Simulation for MR Systems: Coil Design and Safety

Goals of the course

The course RF Simulation for MR systems: Coil Design and Safety is designed to give an in-depth introduction to the numerical computation of radio-frequency (RF) fields in magnetic resonance (MR) systems with the main focus on the application to RF coil design and patient RF safety. The course programme includes modules with theoretical lectures, practical exercises as well as hands-on training on commercial simulation platforms. The goal of the course is to enable the participants to solve typical MR-related field problems with suitable numerical models and to implement post-processing procedures to characterise multi-channel RF coils and to assess the RF exposure of patients/volunteers.

This course will focus on

• Commonly used numerical methods (e.g. FDTD/FIT, FEM)
• Characteristics of the solution in the time and frequency domain
• Basics of electromagnetic theory
• Basic RF engineering principles
• Practical simulation aspects
• Interpretation of numerical results
• Validation methods for numerical results
• Implementation of post-processing procedures for coil characterisation
• Numerical assessment of the RF exposure of the human body
• Learning through practical exercises with application of different numerical methods to fundamental MR-related problems

Educational level

The course is intended for MR physicists, engineers, other scientists and PhD students who either wish to start working in the field of RF coil development and/or RF exposure or who already have basic to intermediate experience in RF simulation.

Course description

The aim of the course is to give an in-depth introduction to the numerical computation of radio-frequency (RF) fields in magnetic resonance (MR) systems. Main focus will be the application to RF coil design and patient safety. After the course, participants will be able to solve typical MR-related field problems with suitable numerical methods and corresponding models, to interpret the calculated field distributions and to perform appropriate post-processing procedures to characterise multi-channel RF transmit coils and to assess the RF safety of patients/volunteers under consideration of common exposure scenarios.

The course is intended for MR physicists, engineers, other scientists and PhD students who either wish to start working in the field of RF coil development and/or RF exposure or who already have basic to intermediate experience in RF simulation.

The course programme includes modules with theoretical lectures, practical exercises as well as hands-on training on commercial simulation platforms. Lectures will prepare the fundamentals for successful application of numerical simulation and will start with selected topics of electromagnetic theory followed by an introduction to numerical methods. To derive appropriate numerical models and implementations of post-processing routines, lectures on RF coil design and characterisation as well as on common approaches to assess the RF exposure under consideration of current RF safety guidelines will be given. Further, methods for the validation of the calculated field distributions will be presented. During the practical exercises, the participants will apply the subject matter of the lectures individually by solving basic simulation problems in one of the two supported simulation platforms (CST Studio Suite, CST AG, Darmstadt, Germany or Sim4Life, Zurich MedTech AG, Zurich, Switzerland). Experienced staff members and representatives of the software vendors will ensure that the participants get acquainted with basic and advanced simulation skills, problem solving and the adjustment of important simulation parameters. During the course, software vendors will give an introduction to their simulation software and will present advanced application examples. For the practical exercises and hands-on training, desktop PCs will be provided for the participants.

Learning objectives

Electromagnetic theory

• Maxwell’s equations
• Field characteristics in quasi-static and electromagnetic regimes
• Conservation of energy – power balance
• Reciprocity
• Spin excitation and signal reception (B₁+ / B₁-)

Numerical methods

• Discretizing Maxwell’s equations
• FIT, FDTD, FEM, MoM
• Solution in time and frequency domain
• Hybrid methods

Validation methods

• B₁+ mapping
• Thermometry
• RF field measurements
• Realistic phantom design and characterisation
• Correlating simulations and measurements

RF coil design and characterisation

• Basic and advanced designs
  • Loop coil, dipole antenna, birdcage coil
  • Matching, tuning
• Multi-channel transmit and receive arrays
• Characterisation
  • Transmission mode: B₁+-efficiency, SAR
  • Receive mode: SNR, g-factor maps

RF safety and guidelines

• Physiological response to RF absorption
• Exposure assessment based on specific absorption rate and tissue temperature
• SAR determination for multi-channel transmit
• RF safety of medical devices

Exercises

• Modelling options with selected numerical methods
• Simulation of birdcage coils
• Network simulation
• RF coil arrays – Matching, tuning, decoupling
• RF coil characterisation
• Determination of RF exposure
• Thermal simulation