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Abstract

A structure provides a gradient field useful in magnetic resonance imaging. Axially aligned, solenoidal-like coils are symmetrically distributed around the perimeter of the bore of a superconducting magnet in an MRI system so as to produce transverse gradients in the X and Y directions with exceptionally high efficiency and exceptionally low acoustic noise. Opposed solenoidal endcoils may be added to reduce axial flux leakage by generating an axial quadrupolar field. Radially aligned coils may be positioned near each end of the axial coils to reduce leakage flux by adding a transverse quadrupolar field to form a resulting octopolar field. Typically, the solenoid-like coils have a mean radius of about 15% of the radius of that of the imaging ellipsoidal region. A thick-walled stainless steel, copper and resin cylinder may be used to simplify gradient shielding problems. Silver plated bronze or stainless steel sheet is used as an rf shield.

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First Claim