Open-type magnetic resonance imaging apparatus

Patent metadata

Field	Value
Publication number	US-11320504-B2
Application number	US-202117195796-A
Country	US
Kind code	B2
Filing date	Mar 9, 2021
Priority date	Apr 27, 2020
Publication date	May 3, 2022
Grant date	May 3, 2022

Abstract

An open-type MRI apparatus includes a pair of static magnetic field magnets and a pair of gradient magnetic field coils. Each static magnetic field magnet includes a discoid magnetic pole configured to generate a static magnetic field in a Z axis direction in which the pair of static magnetic field magnets are opposed each other, and an annular magnetic pole configured to generate a static magnetic field on an X-Y plane perpendicular to the Z axis direction. Each gradient magnetic field coil includes a Z coil configured to provide a magnetic field being gradient in the Z axis direction in the imaging region, a magnetic material block configured to shield the discoid magnetic pole from a magnetic flux generated from the Z coil, and a correction coil configured to shield the annular magnetic pole from the magnetic flux generated from the Z coil.

First claim

What is claimed is:

1. An open-type magnetic resonance imaging apparatus comprising:
a pair of static magnetic field magnets opposed to each other with respect to an imaging region; and
a pair of gradient magnetic field coils opposed to each other with respect to the imaging region, wherein
each static magnetic field magnet includes
a discoid magnetic pole configured to generate a static magnetic field in a Z axis direction in which the pair of static magnetic field magnets are opposed each other, and
an annular magnetic pole configured to generate a static magnetic field on an X-Y plane perpendicular to the Z axis direction, and

each gradient magnetic field coil includes
a Z coil configured to provide a magnetic field being gradient in the Z axis direction in the imaging region,
a magnetic material block configured to shield the discoid magnetic pole from a magnetic flux generated from the Z coil, and
a correction coil configured to shield the annular magnetic pole from the magnetic flux generated from the Z coil.

2. The open-type magnetic resonance imaging apparatus according to claim 1 , wherein
the each static magnetic field magnet includes:
an annular main coil configured to generate the static magnetic field in the Z axis direction; and
a shield coil configured to reduce a magnetic field outside the open-type magnetic resonance imaging apparatus.

3. The open-type magnetic resonance imaging apparatus according to claim 2 , wherein
the shield coil is arranged radially outside of the main coil and configured to generate a magnetic field which has an opposite polarity to a polarity of the magnetic field in the imaging region.

4. The open-type magnetic resonance imaging apparatus according to claim 2 , wherein
the correction coil is arranged radially outside of the Z coil, and
the correction coil is arranged at the same height in the Z axis direction as the Z coil.

5. The open-type magnetic resonance imaging apparatus according to claim 1 , wherein
the each gradient magnetic field coil includes:
an X coil configured to provide a magnetic field being gradient in an X axis direction in the imaging region; and
a Y coil configured to provide a magnetic field being gradient in a Y axis direction in the imaging region.

6. The open-type magnetic resonance imaging apparatus according to claim 5 , wherein
the correction coil is arranged radially outside of the Z coil, and
the correction coil is arranged at the same height in the Z axis direction as the Z coil.

7. The open-type magnetic resonance imaging apparatus according to claim 5 , wherein
the each X coil includes two coils which are arranged in the X axis direction with the Z axis interposed between the two coils, and
the each Y coil includes two coils arranged in the Y axis direction with the Z axis interposed between the two coils.

8. The open-type magnetic resonance imaging apparatus according to claim 1 , further comprising:
an RF coil configured to apply a radiofrequency electromagnetic pulse to the static magnetic field in the imaging region.

9. The open-type magnetic resonance imaging apparatus according to claim 8 , further comprising:
a receiver coil configured to receive a magnetic resonance-related signal from a test subject in response to application of a radiofrequency electromagnetic pulse to the test subject by the RF coil.

10. The open-type magnetic resonance imaging apparatus according to claim 1 , further comprising:
a movable bed configured to convey a test subject into the imaging region of the open-type magnetic resonance imaging apparatus.

11. The open-type magnetic resonance imaging apparatus according to claim 1 , wherein
the correction coil is arranged radially outside of the Z coil, and
the correction coil is arranged at the same height in the Z axis direction as the Z coil.

12. The open-type magnetic resonance imaging apparatus according to claim 1 , wherein
the each magnetic material block includes sheet magnetic materials which are stacked on each other in the Z axis direction and arranged side by side in a tile-like formation in an X axis direction and in a Y axis direction perpendicular to the Z axis direction.

13. The open-type magnetic resonance imaging apparatus according to claim 12 , wherein
the sheet magnetic material of the magnetic material block includes a silicon steel plate.

14. The open-type magnetic resonance imaging apparatus according to claim 12 , wherein
the magnetic material block has a thickness of 20 mm or more.

15. The open-type magnetic resonance imaging apparatus according to claim 1 , wherein
the Z coil is formed in an annular shape about the Z axis.

Assignees

• Hitachi Ltd
• Fujifilm Healthcare Corp

Inventors

• Takayanagi Taisuke
• Aoki Manabu
• Imamura Yukinobu
• Takeuchi Hiroyuki

Classifications

• G01R33/30

  Sample handling arrangements, e.g. sample cells, spinning mechanisms · CPC title

• G01R33/383

  using permanent magnets · CPC title

• G01R33/3806 Primary

  Open magnet assemblies for improved access to the sample, e.g. C-type or U-type magnets · CPC title

• G01R33/4215

  of the gradient magnetic field, e.g. using passive or active shielding of the gradient magnetic field · CPC title

• G01R33/3875

  using correction coil assemblies, e.g. active shimming · CPC title