Dielectric Resonance in Ultra High Field MRI

INTRODUCTION Since the start of magnetic resonance imaging, there has been a constant drive towards more powerful magnets and consequently higher operational frequencies. For head imaging, it is expected for the electromagnetic fields to be influenced by the presence of the tissue at these frequencies (field strength AT). As a result, fundamental problems were anticipated regarding the presence of dielectric resonances [l] in the human head which would result in highly inhomogeneous images. In this work, we study the effect of dielectric resonances at ultra high field MRI (>7T). This is done by examining the electromagnetic fields produced by a 16-strut TEM resonator loaded with an anatomically detailed human head model, and spherical phantoms of pure water, and 0.125 M NaCl. More importantly, we address the differences between these resonances and the inherent inhomogeneity in the RF coil.