Design and analysis of quadrature coils for high-field NMR system

Abstract

The quadrature coil has been known to have various advantages compared with conventional single coil. Saving of transmitted power and improvements of radiofrequency magnetic field homogeneity as well as the signal-to-noise ratio could be very useful especially in high field magnetic resonance imaging. A quadrature coil pair named as quadrature-quadrature coil for simultaneous proton and sodium imaging in high field MRI system is introduced. The quad.-quad. coil is composed of two quadrature coils, one of which is for proton imaging and the other is for sodium imaging. The proton quadrature coil is composed of two identical ring resonator coils which have been found to be one of the suitable coils for high field MRI. While, the sodium quadrature coil is composed of two identical saddle coils wellknown in low field MRI. Design scheme of each coil is considered. Experimental improvements with quadrature coils reach theoretical predictions verifying the advantages of quadrature excitation and detection in high field MRI. Also, some theoretical considrations on quadrature excitation and detection are given.