Patent ID: 6456076
Filing Date: 2002-09-24
Classification: G01R

Abstract:
A cylindrical shielding coil for providing a canceling magnetic field gradient to cancel and error magnetic field gradient created within an imaging volume by eddy currents generated by a gradient coil in a volume outside of said gradient coil, the shielding coil defining an axis therethrough and comprising:a non-magnetic electrically insulating cylindrical coil support having an internal cavity which forms a volume for accepting said gradient coil and said imaging volume; and N electrically conductive cylindrical windings wound in a plurality of turns in a substantially helical path about a surface of said coil support, each turn of each winding being electrically spaced from each other turn of each said winding such that spacing between respective turns of each said winding decreases in approximate proportion to the distance of said respective turns from a center of each of said windings in a direction parallel to said axis of said coil, each of said N windings being interleavingly wound in the same direction about said surface of said coil support and separated from each other winding of said N windings in an angular orientation of approximately 360Â°/N about said coil support, whereby N is determined so as to cancel harmonics of an error magnetic field gradient up to and including the Mth harmonic.