A solenoid-like coil producing transverse RF fields for MR imaging

Abstract

A solenoidal RF coil is presented that generates an RF field only perpendicular to the long axis, so that it can be used longitudinally in the usual superconducting solenoid magnet for NMR. This new design is superior to the traditional saddle coil or Helmholtz pair. Applications for the coil will include imaging of legs, arms, etc., as well as analytical application in high-resolution NMR. A tilted single-turn-solenoid, which has the plane of each loop tilted with respect to the cylinder axis, is implemented to generate an RF field with a component perpendicular to the coil-cylinder axis. The novel addition of an eddy-current coil eliminates the undesirable longitudinal component of the RF field, leaving an RF field entirely perpendicular to the coil-cylinder axis. By inserting the eddy coil, the spatial homogeneity of the transverse RF field is greatly improved, with significant increases in the H1 field strength and receiving sensitivity. Images with the eddy-coil-modified tilted solenoid are remarkably uniform in intensity over a large useful volume.