THE EVALUATION OF DIELECTRIC RESONATORS CONTAINING H2O OR D2O AS RF COILS FOR HIGH-FIELD MR-IMAGING AND SPECTROSCOPY

Electromagnetic resonators consisting of low-loss dielectric material and/or metallic boundaries are widely used in microwave technologies. These dielectric resonators usually have high Q factors and well-defin ed field distributions. Magnetic resonance imaging was shown as a way of visualizing the magnetic field distribution of the resonant modes o f these resonators, if the dielectric body contains NR;IR sensitive nu clei. Dielectric resonators have also been proposed as RF coils for ma gnetic resonance experiments. The feasibility of this idea in high-fie ld MR is discussed here. Specifically, the dielectric resonances of cy lindrical water columns were characterized at 170.7 MHz (4 T H-1 Larmo r frequency), and evaluated as NMR transmit and receive coils. The die lectric resonance of a cylindrical volume of D2O was used to image a h and at 170.7 MHz. This study demonstrated that MRI is an effective way of visualizing the magnetic field in dielectric structures such as a water cylinder, and can potentially be generalized to solid-state diel ectric devices. The possible applications of dielectric resonators oth er than simple cylindrical volumes in MRI and MR solution spectroscopy at high field strengths are also discussed. (C) 1996 Academic Press, Inc.