Magnet apparatus suitable for magnetic resonance imaging.

摘要

The invention relates to an apparatus for producing a magnetic field in a space between two oppositely arranged permanent magnet discs, which is suitable for use in magnetic resonance imaging (MRI). An object of the invention is to reduce the size and weight of the yoke connecting the two permanent magnet discs without causing magnetic saturation of the yoke in view of the fact that magnetic saturation of the yoke leads to the appearance of leakage flux and consequential lowering of the uniformity of the magnetic field. The object is accomplished by regulating the cross-sectional area of the whole magnetic path in the yoke, Ay, such that the following equation holds: Ay = 1/a x AmBm/Bys, where Am is the cross-sectional area of magnetic path in each permanent magnet disc, Bm is the magnetic flux density in each permanent magnet disc at normal temperature, Bys is the saturation magnetic flux density of the yoke at normal temperature, and a is a coefficient the value of which is not larger than 1 and not smaller than 0.6. <IMAGE>