4920316 Method and apparatus for reducing base field shifts in a magnetic resonance device due to pulsed magnetic field gradients

Abstract

A magnetic resonance imager/spectrometer including a main magnet having a bore axially formed therethrough in which a base field is formed. A gradient field forming means is positioned inside the bore of the main magnet for providing at least one axial field gradient inside the bore. An electrically conductive media in the main magnet surrounds the gradient coil and has eddy currents induced thereon via pulsing of the gradient field which generates a disturbing magnetic field along said same axis as said gradient field. A gradient position adjusting means, including an adjustable positioner, is used for adjusting the position of the gradient field forming means with respect to the bore of the main magnet in order to cause the center point of the axial magnetic fields of the electrically conductive media and the gradient field forming means to substantially coincide.