Abstract: In a magnetic resonance imaging system, wherein a subject to be imaged is supported within a bore of a magnet assembly and exposed to radio frequency (RF) energy emitted from an excitation coil, gradient coils and an RF screen are disposed within the region of the bore exteriorly to an excitation coil and are configured with a split or open region facing sections of the excitation coil for reduced image currents in the gradient coils and the RF screen from RF field generated by the excitation coil. The X gradient coil is reduced to two enlarged coil sections to the left and to the right of the bore. The two opposed sections of the X gradient coil, the two opposed sections of the Y gradient coil, and the opposed pairs of sections of the Z gradient coil are spaced apart at the top and the bottom of the bore for reduced interaction with the excitation coil section located at the top and the bottom of the bore. Thereby, the space between the excitation coil and the shield can be reduced.

Abstract: A permanent magnet assembly having a central elliptical bore, suitable for reception of a patient in an MRI system, is formed of a plurality of elliptically shaped sections disposed along an axis of the bore. Each section is subdivided into a plurality of segments in which each segment is constructed of bricks of magnetic material. Each brick has the shape of a right parallel piped. In any one of the segments, all of the bricks are arranged parallel to a common plane which is parallel to the bore axis. The bricks are magnetized with magnetization vector oriented in a common direction perpendicular to the plane. Full bricks are employed throughout all of the segments with the exception of a plurality of bricks along a surface of the bore wherein truncation of one or more of the bricks may be required to attain a desired homogeneity to a dipole magnetic field within the field.