Patent ID: 7224167
Filing Date: 2007-05-29
Classification: G01R

Abstract:
1. A magnetic field generating apparatus for use in magnetic resonance imaging (MRI), the apparatus comprising: an annular magnet field generator defining a patient bore having an imaging volume, a z-axis, and an isocenter; a gradient coil disposed between the magnetic field generator and the patient bore; a first set of shim elements disposed at a region between the magnetic field generator and the imaging volume; and a second set of shim elements disposed at the region at a location having equal to or greater than a specified Z/R ratio, where Z defines an axial distance from the isocenter and R defines a radial distance from the z-axis; wherein the first set of shim elements are configured and disposed to substantially compensate for field inhomogeneities resulting from the magnetic field generator; wherein the second set of shim elements are configured and disposed to substantially compensate for B wherein in response to the first set of shim elements being disposed at a location having less than the specified Z/R ratio a negative B