Magnetic resonance imaging apparatus and static magnetic field correction method
AssigneesKabushiki Kaisha Toshiba, Toshiba Medical Systems Corporation
InventorsShigehide Kuhara, Hirofumi Anno, Masato Ikedo
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Abstract
A magnetic resonance imaging apparatus includes a collector which collects magnetic resonance signals emitted from a region of interest of a subject, and a correction magnetic field generator which generates a correction magnetic field to correct the nonuniformity of a static magnetic field on the basis of magnetic resonance signals which are contained in the magnetic resonance signals collected by the collector, are emitted from a specific region which forms a portion of the region of interest.
Claims15
A magnetic resonance imaging apparatus adapted to reconstruct an image associated with a subject placed in a static magnetic field on the basis of magnetic resonance signals emitted from the subject, comprising:
- a collector which collects magnetic resonance signals emitted from a region of interest of the subject;
- and
- a correction magnetic field generator which generates a correction magnetic field to correct the nonuniformity of the static magnetic field on the basis of magnetic resonance signals which are contained in the magnetic resonance signals collected by the collector, are emitted from a specific region which forms a portion of the region of interest.
A magnetic resonance imaging apparatus which subjects a subject under examination placed in a static magnetic field to a radio-frequency magnetic field and gradient magnetic fields to collect magnetic resonance signals from the subject, comprising:
- a shim coil to correct the nonuniformity of the static magnetic field;
- a setup unit which sets up a three-dimensional region within the static magnetic field;
- a measurement unit which measures the distribution of strength of the static magnetic field within the three-dimensional region set up by the setup unit;
- and
- a calculation unit which calculates a value of current to be applied to the shim coil to correct the nonuniformity of the static magnetic field in accordance with the magnetic field distribution, of the magnetic field distribution measured by the measurement unit, within a spherical, elliptical or combined ellipsoid region contained in the three-dimensional region.
A magnetic resonance imaging apparatus which subjects a subject under examination placed in a static magnetic field to a radio-frequency magnetic field and gradient magnetic fields to collect magnetic resonance signals from the subject, comprising:
- a measurement unit which measures the distribution of strength of the static magnetic field;
- an extraction unit which extracts the distribution of strength of the static magnetic field within a spherical, elliptical or combined ellipsoid region from the static magnetic field distribution measured by the measurement unit;
- and
- a shimming unit which carries out shimming to increase the uniformity of the static magnetic field in accordance with the magnetic field distribution extracted by the extraction unit.
For use with a magnetic resonance imaging apparatus in which a subject under examination from which magnetic resonance signals are to be collected is placed in a static magnetic field, a method of correcting the static magnetic field comprising the steps of:
- collecting magnetic resonance signals emitted from a region of interest of the subject;
- and
- generating a correction magnetic field to correct the nonuniformity of the static magnetic field on the basis of magnetic resonance signals which are contained in the collected magnetic resonance signals, are emitted from a specific region which forms a portion of the region of interest.
For use with a magnetic resonance imaging apparatus in which a subject under examination placed in a static magnetic field is subjected to a radio-frequency magnetic field and gradient magnetic fields to collect magnetic resonance signals from the subject and a shim coil is set to correct the nonuniformity of the static magnetic field, a method of correcting the static magnetic field comprising the steps of:
- setting up a three-dimensional region within the static magnetic field;
- measuring the distribution of strength of the static magnetic field within the three-dimensional region;
- and
- calculating a value of current to be applied to the shim coil to correct the nonuniformity of the static magnetic field in accordance with the magnetic field distribution, of the measured magnetic field distribution, within a spherical or elliptical region contained in the three-dimensional region.
For use with a magnetic resonance imaging apparatus which subjects a subject under examination placed in a static magnetic field to a radio-frequency magnetic field and gradient magnetic fields to collect magnetic resonance signals from the subject, a method of correcting the static magnetic field comprising the steps of:
- measuring the distribution of strength of the static magnetic field;
- extracting the distribution of strength of the static magnetic field within a spherical or elliptical region from the measured static magnetic field distribution;
- and
- performing shimming to increase the uniformity of the static magnetic field in accordance with the extracted magnetic field distribution within the spherical or elliptical region.
Dependencies are inferred from the claim text.