Magnetic field generating device for use in MRI

摘要

The invention relates to field generating apparatus with a pair of magnetic pole pieces (2) disposed facing one another to define in the space (4) between them a working air gap. Each pole piece (2) has a laminate structure comprising a soft ferrite layer (53,55; 63,65) facing the space (4) and carried on a base layer (51;61) of magnetic material. A layer (57;67) having low magnetic permeability and high electrical resistance is interposed between said soft ferrite layer and said base layer (51;61); and optionally, there is interposed between said low permeability layer (57,67) and said base layer (51;61) a layer (66) composed of laminated silicon steel sheets). The laminated layers disposed on the base plate (51;61) are surrounded by a rim (52;62) of magnetic material, said rim protruding from the periphery of the base plate (51;61). High speed image pick-up at high sensitivity and sharpness is promoted by reducing the eddy current and the remanent magnetism generated in the pole piece by gradient magnetic field coils. <MATH>