| 摘要 |
PURPOSE:To obtain a shielding effect even if a main magnetic field is intensified, by providing a cancelling coil, which generates magnetic flux in the opposite direction with respect to magnetic flux from a main coil so as not to saturate a magnetic body, in the inside of the magnetic body. CONSTITUTION:A cancelling coil 6 is arranged between a magnetic body 5, i.e., a shield, and a main coil 3. A current in the reverse direction with respect to the main coil 3, is made to flow through the cancelling coil 6, and a magnetic field in the magnetic body 5 is weakened. Thus, the magnetic body 5 can absorb the leakage magnetic field from the main coil. Since the magnetic field Bi in the magnetic body is weakened and is not saturated, the characteristics as the magnetic body can be maintained, and the shielding effect can be maintained. In this way, even if the main magnetic field is intensified in a magnetic resonance image apparatus, the leakage magnetic field yielded in the main coil can be absorbed into iron by the function of the cancelling coil, and the shielding effect with the iron can be maintained.
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