IP Library › Granted Patent US 12693358
Granted Patent B2
US 12693358 · App. 18/453,372 · Granted Jul 28, 2026

MRI apparatus

Inventors: Takehiro Shibuya (Nasushiobara, JP); Hiromi Kawamoto (Yaita, JP); Sadanori Tomiha (Nasushiobara, JP); Misaki Hattaha (Sakura, JP)
Assignee: Canon Kabushiki Kaisha
G01R33/3815G01R33/3804G01R33/543
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Quick Facts
Patent No.
US 12693358
App. No.
18/453,372
Granted
Jul 28, 2026
Kind
B2
Abstract

In one embodiment, an MRI apparatus includes: a static magnet provided with a superconducting coil and configured to generate a static magnetic field having static magnetic field distribution in an open space outside the superconducting coil; control circuitry configured to adjust the static magnetic field distribution; and a reconstruction processing circuit configured to generate a magnetic resonance image on the basis of magnetic resonance signals emitted from an object that is at least partially placed in the open space outside the superconducting coil.

Claims (57)

1 . An MRI apparatus, comprising:

a static magnet provided with a superconducting coil and configured to generate a static magnetic field having static magnetic field distribution in an open space outside the superconducting coil, the superconducting coil being divided into a plurality of segments, each segment having a superconducting subcoil that is electrically independent of other of the plurality of segments, the plurality of the segments in the superconducting coil being divided into a first group and a second group;

control circuitry configured to adjust the static magnetic field distribution, by having a direction of a first electric current applied to the segments in the first group opposite to a direction of a second electric current applied to the segments in the second group, and by independently controlling a magnitude of the first electric current and a magnitude of the second electric current, so as to adjust at least one of a position of an imaging region of an object and a range of the imaging region of the object; and

a reconstruction processing circuit configured to generate a magnetic resonance image based on magnetic resonance signals emitted from the object that is at least partially placed in the open space outside the superconducting coil.

2 . The MRI apparatus according to claim 1 , further comprising a magnet power supply configured to apply the electric current to the superconducting coil,

wherein the control circuitry is further configured to control the static magnetic field distribution by a persistent current mode in which the electric current applied to the superconducting coil is increased to a predetermined value and then the electric current continues to flow in the superconducting coil in a state of being disconnected from the magnet power supply.

3 . The MRI apparatus according to claim 1 , further comprising a magnet power supply configured to apply the electric current to the superconducting coil,

wherein the control circuitry is further configured to control the static magnetic field distribution by adjusting the electric current applied to the superconducting coil under a state where the magnet power supply is connected to the superconducting coil.

4 . The MRI apparatus according to claim 1 , further comprising an imaging-condition setting circuit configured to set at least one imaging condition, wherein:

the at least one imaging condition comprises the at least one of the position of the imaging region of the object and the range of the imaging region of the object; and

the control circuitry is further configured to adjust the static magnetic field distribution based on the at least one imaging condition being set by the imaging-condition setting circuit.

5 . The MRI apparatus according to claim 1 , further comprising a magnet power supply configured to apply an electric current to the superconducting coil,

wherein the control circuitry is further configured to determine temporal change patterns of the electric current from the magnet power supply for both cases of magnetizing the static magnet and demagnetizing the static magnet based on at least one of:

the static magnetic field distribution;

a strength of the static magnetic field;

a temperature of the superconducting coil;

an experienced magnetic field of the superconducting coil; and

a cooling performance of the superconducting coil.

6 . The MRI apparatus according to claim 1 , further comprising:

a magnetic material configured to adjust the static magnetic field distribution; and

a driver configured to move the magnetic material,

wherein the control circuitry is further configured to adjust the static magnetic field distribution by controlling the driver in such a manner that the magnetic material is moved relative to the static magnet.

7 . The MRI apparatus according to claim 1 , further comprising:

a gradient coil configured to apply a gradient magnetic field to the object;

an RF coil configured to apply a radio-frequency magnetic field to the object;

a table configured to support the object; and

a driver configured to move at least one of the gradient coil, the RF coil, and the table,

wherein the control circuitry is further configured to adjust the static magnetic field distribution by controlling the driver in such a manner that the at least one of the gradient coil, the RF coil, and the table is moved relative to the static magnet.

8 . The MRI apparatus according to claim 1 , wherein the control circuitry is further configured to adjust the magnetic field distribution so as to adjust the position of the imaging region of the object.

9 . An MRI apparatus, comprising:

a static magnet provided with a superconducting coil and configured to generate a static magnetic field having static magnetic field distribution in an open space outside the superconducting coil, the superconducting coil being divided into a plurality of segments, each segment having a superconducting subcoil that is electrically independent of other of the plurality of segments, the plurality of the segments in the superconducting coil being divided into a first group and a second group;

a magnet power supply configured to apply an electric current to the superconducting coil;

control circuitry configured to adjust the static magnetic field distribution by independently controlling the electric current applied to the superconducting coil for each segment so as to adjust at least one of a position of an imaging region of an object and a range of the imaging region of the object: wherein the control circuitry is further configured to

control the static magnetic field distribution relating to the segments in the first group by having a persistent current mode in which an electric current applied to the first superconducting coil is increased to a predetermined value and then the electric current continues to flow in the segments in the first group in a state of being disconnected from the magnet power supply; and

control the static magnetic field distribution relating to the segments in the second group by adjusting an electric current applied to the segments in the second group under a state where the magnet power supply is connected to the segments in the second group; and

a reconstruction processing circuit configured to generate a magnetic resonance image based on magnetic resonance signals emitted from the object that is at least partially placed in the open space outside the superconducting coil.

10 . The MRI apparatus according to claim 9 , further comprising an imaging-condition setting circuit configured to set at least one imaging condition, and wherein:

the at least one imaging condition comprises the at least one of the position of the imaging region of the object and the range of the imaging region of the object; and

the control circuitry is further configured to adjust the static magnetic field distribution based on the at least one imaging condition being set by the imaging-condition setting circuit.

11 . The MRI apparatus according to claim 9 , further comprising a magnet power supply configured to apply an electric current to the superconducting coil, and

wherein the control circuitry is further configured to determine temporal change patterns of the electric current from the magnet power supply for both cases of magnetizing

the static magnet and demagnetizing the static magnet based on at least one of:

the static magnetic field distribution;

a strength of the static magnetic field;

a temperature of the superconducting coil;

an experienced magnetic field of the superconducting coil; and

a cooling performance of the superconducting coil.

12 . The MRI apparatus of claim 9 , further comprising:

a magnetic material configured to adjust the static magnetic field distribution; and

a driver configured to move the magnetic material,

wherein the control circuitry is further configured to adjust the static magnetic field distribution by controlling the driver in such a manner that the magnetic material is moved relative to the static magnet.

13 . The MRI apparatus of claim 9 , further comprising:

a gradient coil configured to apply a gradient magnetic field to the object;

an RF coil configured to apply a radio-frequency magnetic field to the object;

a table configured to support the object; and

a driver configured to move at least one of the gradient coil, the RF coil, and the table,

wherein the control circuitry is further configured to adjust the static magnetic field distribution by controlling the driver in such a manner that the at least one of the gradient coil, the RF coil, and the table is moved relative to the static magnet.