ON THE PERFORMANCE OF TUBULAR SURFACE COILS IN NUCLEAR-MAGNETIC-RESONANCE IMAGING AND SPECTROSCOPY

Surface coils are important devices in the clinical application of nuc lear magnetic resonance imaging and spectroscopy (NMRIS) because they have higher signal-to-noise ratios than body or head coils in superfic ial regions. This paper describes our theoretical and experimental stu dy of the performances of tubular surface coils, aiding the effective application of such coils to NMRIS. We present formulas for the RF mag netic (H1) fields produced by tubular surface coils placed over layere d media, and for the self- and loaded-impedances of these coils. The c alculated results show the dependence of the coil performances on the coil design parameters and the characteristics of the sample under tes t. We include the calculated results for the H1 field phase shifts in conductive samples.