Shim coil for nuclear magnetic resonance imaging apparatus
AssigneeKabushiki Kaisha Toshiba
InventorMotoji Haragashira
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Abstract
A shim coil for a nuclear magnetic resonance imaging apparatus capable of being independent of influences from time varying magnetic fields generated by gradient coil. The shim coil includes primary coil for producing an extra magnetic field in accordance with a direct current to be supplied, and compensatory coil for producing a compensatory magnetic field which cancels a magnetic field produced by the primary coil means in response to an induced current due to the time varying gradient magnetic fields.
Claims14
A shim coil, to which a direct current is to be supplied from a power supply, to be incorporated in a nuclear magnetic resonance imaging apparatus equipped with a gradient coil for generating time varying gradient magnetic fields, the shim coil comprising:
- primary coil means for producing an extra magnetic field in accordance with said direct current;
- and compensatory coil means for producing a compensatory magnetic field which causes cancellation of a magnetic field produced by said primary coil means in response to an induced current due to the time varying gradient magnetic fields.
In a nuclear magnetic resonance imaging system, the combination comprising:
- a. means for producing a static magnetic field encompassing a region of interest, said static field being subject to conditions causing inhomogeneity therein;
- b. means for superimposing upon said static field an extra magnetic field for causing a net magnetic field, having a net homogeneity, upon said static field being subject to said conditions causing said inhomogeneity;
- c. means coupled to said extra field for causing transient change in said extra field;
- and
- d. means for compensating for said transient change without producing a field in the nature of said extra field.
In a method for operating a nuclear magnetic resonance imaging system, the steps comprising:
- a. producing a magnetic field pattern providing homogeneity in a static magnetic field in a region of interest under conditions tending to cause inhomogeneity therein;
- and
- b. preventing time varying changes other than said conditions from affecting said magnetic field pattern.
Dependencies are inferred from the claim text.