Magnetic resonance imaging apparatus

A superconducting magnet apparatus comprising:

• magnetic field generating sources, which are made of substances having superconducting properties and are operative to feed electric current for generating a uniform magnetic field, whose direction is a first direction, in a finite region;
• cooling means for cooling said magnetic field generating sources to a temperature, at which the substances exhibit the superconducting properties, and for maintaining said magnetic field generating sources at the temperature;
• and
• supporting means for supporting said magnetic field generating sources,
• wherein said magnetic field generating sources are placed equidistantly in such a way as to face each other across said uniform magnetic field region along the first direction and are composed of two sets of magnetic field generating device groups for feeding electric current in a coaxial direction with said first direction being made a center axis,
• wherein each of the sets of magnetic field generating device groups comprises:
• one or more first magnetic field generating devices for feeding electric current which flows in a second direction along a circumference of a circle, whose center axis extends in said first direction, so as to generate a main component of said uniform magnetic field;
• one or more second magnetic field generating devices for feeding electric current which flows in a direction opposite to said second direction, so as to reduce a magnetic field generated outside said magnetic field generating sources;
• and
• one or more third magnetic field generating devices for feeding electric current which flows in a direction that is same as or opposite to the second direction so as to improve magnetic homogeneity of said uniform magnetic field, and,
• wherein a diameter of said first magnetic field generating device is nearly equal to that of the second magnetic field generating device, a diameter of said third magnetic field generating device is less than that of the first magnetic field generating device, an amount of electric current fed to said third magnetic field generating device is less than an amount of electric current fed to said first magnetic field generating device, and a distance between said first magnetic field generating devices facing each other across said uniform magnetic field region is shorter than that between said second magnetic field generating devices facing each other across said uniform magnetic field region.