| 摘要 |
PURPOSE:To obtain an clear image in accordance with the size of an object, by providing a plurality of optimum shim coil current value setting means and a means for selecting the optimum shim coil current value to uniform the magnetic field of said objective region. CONSTITUTION:Main magnets 1 generate the main magnetic field BZ in a Z-axis direction and shim coils 2 are arranged between the main magnets 1 and correct the error of the distribution of the magnetic field BZ in the Z-axis direction to uniformize the same. A shim coil current supply means 4 supplies the shim coil current 4a corresponding to a shim coil current value to the shim coils 2. To n pieces of optimum shim coil current value setting means 3A, shim coil current values 3a1-3an for optimumly uniformizing the magnetic field distribution in the Z-axis direction are preset in accordance with respective regions 1 to region n. A shim coil current value selecting means 5 constituted of an appropriate manual change-over switch selects one shim coil current value 5a out of the optimum shim coil current value setting means 3A1-3An of the regions 1-n if necessary to output the same to the shim coils current supply means 4. |
