Magnetic Resonance RF Coil Modeling and Simulation: Analysis of Biot-Savart Law and Frequency Response Methods

Magnetic resonance applications in diagnostic medical imaging often utilize radiofrequency (RF) coils for signal excitation and acquisition. The use of RF coils in magnetic resonance imaging provides a method to place a near-field antenna in close proximity with the anatomy of imaging interest and enables substantial improvements in the signal-to-noise ratios (SNR) and image quality relative to the standard whole-volume coils. This thesis focuses on the methods and ability to electronically model the behavior of an RF coil antenna. The capability to simulate a coil and predict the resulting performance characteristics is a significant advantage in the coil design and development process. The investigation analyzes several configurations of three different size coils, 10cm, 13 cm, and 16 cm, single element/loop coils and the effect of frequency changes on the resulting magnetic field patterns. The relative performance differences of the coils are evaluated at two primary MRI field strengths, 1.5 Tesla (64 MHz) and 3.0 Tesla (127 MHz). Several modeling methods are briefly reviewed and the advantages and disadvantages of each are compared, with an emphasis on using the Numerical Electromagnetics Code (NEC) for the coil simulations. Electronic models are created for each of the coils and simulations conducted to compare the resulting magnetic field distributions created by each coil antenna. A uniform magnetic field pattern that covers the largest area of the coil geometry is the goal. Analysis of the magnetic field patterns that are calculated from the simulations, investigation of the current magnitude distribution, and review of the coil input impedance variations, lead to defining a method that can be used to alter the coil performance to improve the magnetic field uniformity. The simulation results are then used as input for building a physical coil antenna and results are verified using RF laboratory equipment and basic MRI scans