A magnet for MRI apparatus has a magnetic circuit which includes a magnetic flux
path formed by a ferromagnetic material and a magnetic flux path formed by magnetic
flux return coils or magnetic flux control coils, so that a 5-gauss line of leakage
fluxes can be kept within a sphere 3 m in radius even when the static magnetic
field intensity exceeds 1 tesla and a comparatively light magnet for MRI apparatus
can be provided. Further, the fluxes escaping vertically from the static magnetic
field sources are led compactly to a horizontal direction by installing magnetic
flux paths of ferromagnetic materials and coils with polarities opposing those
of the static magnetic fields. This arrangement minimizes an increase in the total
height of the magnet for MRI apparatus, keeping the magnet within the total height
of 3 m.
