Modeling and design of resonators for electron paramagnetic resonance imaging and ultra high field magnetic resonance imaging.

摘要

The purpose of this work was to use computer-aided design methods to analyze resonant cavities for electron paramagnetic resonance (EPR) and magnetic resonance (MR) imaging. As a result of this analysis, a new design and modifications to existing ones were proposed.;The behavior of a L-band transverse electric reentrant resonator (TERR) for in-vivo EPR spectroscopy and imaging was analyzed. The influence of various geometrical parameters on the B1 field distribution was investigated. The optimal size of a sample that can be imaged with this type of resonator was determined, as well as the dependence of the quality factor on the sample size and geometry. Some of the numerical results were compared with experimental data. Finally, a design for a 300 MHz TERR was proposed.;In the second part of this work, numerical studies using a model of a 16-strut transverse electromagnetic (TEM) resonator for MR imaging were performed. Simulations were performed either with a saline-filled spherical phantom or with a 4-mm resolution head model. The purpose was to investigate ways to improve the B1 homogeneity, obtain localized imaging, and explore the potential use of the first mode of the TEM structure. Models of TEM structures with reduced number of struts to allow for better patient access were designed. The effect of partially filling the TEM resonator with high dielectric constant material on the field homogeneity was analyzed.