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Abstract

A gradient coil assembly is directly coupled throughout its entire axial length and circumferential area to the inner cylinder of the cryostat vacuum container enclosing a cylindrical superconducting MRI static field magnet. Any air space between the concentric gradient coil assembly and the cryostat is eliminated. This stiffer system produces lower velocities of the switched gradient coil assembly, which in turn produces lower noise levels in the patient opening of the gradient coil assembly and in the ambient environment. Alternatively, an annular space separates the gradient coil assembly from the MRI static field magnet assembly, and the gradient coil assembly is rigidly coupled to the inner cylinder of the MRI static field magnet assembly by discrete coupling rings. The annular space or chamber between the two assemblies is broken into smaller volumes or subchambers, which do not interconnect in the axial direction and thereby prevent axial propagation of noise generated in the chambers. Acoustic treatment of the surfaces within the chambers, including evacuation of that space, can reduce the amount of noise escaping to the ambient environment.

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First Claim