Dielectric resonance in magnetic resonance imaging: Signal inhomogeneities in samples of high permittivity

Abstract

A distinctive signal inhomogeneity arises in magnetic resonance (MR) images of samples whose dimension is comparable to the wavelength of electromagnetic fields at the resonant frequency. In this study, spatial distributions of magnitude and phase of MR signals in cylindrical phantoms were obtained by theoretical calculations and experiments. As the diameter of the phantom approaches the wavelength of electromagnetic fields in the phantom, the center of the phantom exhibited high magnitude of MR signals. An increase in conductivity resulted in a suppression of the signal inhomogeneity due to skin effect. In addition, the increase in conductivity caused a phase delay at the center of the phantom.