Has iron SIMM magnetostatic field amendment means the super-conductivity magnet system null for MRI

摘要

PURPOSE:To realize a superconductive magnet apparatus for MRI with an iron shim magnetostatic field correction means which achieves a higher efficiency of a shield gradient magnetic field coil without changing the diameter of a clear bore of a magnet for magnetostatic fields and that of an internal gradient magnetic field coil. CONSTITUTION:An iron shim assembly 2 is mounted inside an external gradient magnetic field coil 4 but not inside a magnet 1 for magnetostatic fields. This structure allows increase in the diameter of the external gradient magnetic field coil 4 to reduce necessary current which flows through the external gradient magnetic field coil 4 thereby enabling the production of a superconductive magnet apparatus with high efficiency.