Gradient magnetic field coil device, adjustment method therefor, and magnetic resonance imaging apparatus

Patent metadata

Field	Value
Publication number	US-9689938-B2
Application number	US-201214239872-A
Country	US
Kind code	B2
Filing date	Aug 10, 2012
Priority date	Sep 5, 2011
Publication date	Jun 27, 2017
Grant date	Jun 27, 2017

Abstract

In a gradient magnetic field coil device including: a plurality of main coils generating in an imaging region of a magnetic field resonance imaging device a magnetic field distribution in which an intensity linearly inclines; and a plurality of shield coils, arranged on an opposite side of the imaging region across the main coils, suppressing residual magnetic field generated by the main coils on the opposite side. The plurality of main coils and the plurality of shield coils are connected in series. The device further includes a plurality of current adjusting devices, connected to the shield coils in parallel, independently adjusting currents flowing through the shield coils, respectively, to enhance symmetry of the residual magnetic field. The gradient magnetic field coil device is provided which can suppress generation of eddy current magnetic field even if there is a relative position deviation between the main coils and shield coils.

First claim

The invention claimed is:

1. A gradient magnetic field coil device comprising:
a plurality of first coils each of which generates in an imaging region of a magnetic field resonance imaging device a magnetic field distribution in which an intensity linearly increases in a predetermined direction; and
a plurality of second coils each of which is arranged on an opposite side of the imaging region across the first coils and suppresses residual magnetic field generated on the opposite side by the first coil, wherein
the plurality of first coils and the plurality of second coils are connected in series, the gradient magnetic field coil device further comprising
a plurality of current adjusting devices, connected to either of the first coils or the second coils in parallel, independently adjusting currents flowing through the first coils or the second coils, respectively,
wherein the plurality of first coils and the plurality of second coils are connected in series by alternately connecting a member from the first coils and a member from the second coils.

2. The gradient magnetic field coil device as claimed in claim 1 , wherein
the plurality of current adjusting devices includes first and second driving sources, a part of the plurality of first coils and a part of the plurality of second coils being connected in series and connected to the first driving power source, and
a remaining part of the plurality of first coils and a remaining part of the plurality of second coils are connected in series and connected to the second driving power source which is synchronous with the first driving power source.

3. The gradient magnetic field coil device as claimed in claim 1 , wherein the current adjusting device is disposed at one end of the gradient magnetic field coil device in the predetermined direction in which the intensity linearly increases or a direction orthogonal with the predetermined direction.

4. The gradient magnetic field coil device as claimed in claim 1 , wherein the current adjusting device adjusts a value of a current flowing through the first coil or the second coil so as to enhance symmetry of the residual magnetic field.

5. The gradient magnetic field coil device as claimed in claim 1 , wherein the current adjusting device adjusts currents so as to make a direction and an intensity of the residual magnetic field distribution in plane symmetry with respect to a plane passing a center of the imaging region or point symmetry with respect to a center of the imaging region.

6. The gradient magnetic field coil device as claimed in claim 1 , further comprising a magnet device, generating a static magnetic field, arranged on an opposite side of the imaging region across the second coil.

7. A gradient magnetic field coil device, comprising:
a plurality of first coils each of which generates in an imaging region of a magnetic field resonance imaging device a magnetic field distribution in which an intensity linearly increases in a predetermined direction; and
a plurality of second coils each of which is arranged on an opposite side of the imaging region across the first coils and suppresses residual magnetic field generated on the opposite side by the first coil, wherein
the plurality of first coils and the plurality of second coils are connected in series, the gradient magnetic field coil device further comprising
a plurality of current adjusting devices, connected to either of the first coils or the second coils in parallel, independently adjusting currents flowing through the first coils or the second coils, respectively,
wherein the plurality of first coils and the plurality of second coils are connected in series by alternately connecting a member from the first coils and a member from the second coils,

wherein the current adjusting device includes a variable resistor and a variable inductor as a variable impedance element, and wherein
a ratio of resistance components between either one of the first coil or the second coil and the current adjusting device is substantially equal to a ratio of inductance components between the either one of the first coil or the second coil and the current adjusting device.

8. The gradient magnetic field coil device as claimed in claim 7 , wherein
the plurality of current adjusting devices includes first and second driving sources, a part of the plurality of first coils and a part of the plurality of second coils being connected in series and connected to the first driving power source, and
a remaining part of the plurality of first coils and a remaining part of the plurality of second coils are connected in series and connected to the second driving power source which is synchronous with the first driving power source.

9. The gradient magnetic field coil device as claimed in claim 7 , wherein the current adjusting device is disposed at one end of the gradient magnetic field coil device in the predetermined direction in which the intensity linearly increases or a direction being orthogonal with the predetermined direction.

10. The gradient magnetic field coil device as claimed in claim 7 , wherein the current adjusting device adjusts a value of a current flowing through the first coil or the second coil so as to enhance symmetry of the residual magnetic field.

11. The gradient magnetic field coil device as claimed in claim 7 , wherein the current adjusting device adjusts currents so as to make a direction and an intensity of the residual magnetic field distribution in plane symmetry with respect to a plane passing a center of the imaging region or point symmetry with respect to a center of the imaging region.

12. The gradient magnetic field coil device as claimed in claim 7 , further comprising a magnet device, generating a static magnetic field, arranged on an opposite side of the imaging region across the second coil.

13. A gradient magnetic field coil device comprising:
a plurality of first coils each of which generates in an imaging region of a magnetic field resonance imaging device a magnetic field distribution in which an intensity linearly increases in a predetermined direction; and
a plurality of second coils each of which is arranged on an opposite side of the imaging region across the first coils and suppresses residual magnetic field generated on the opposite side by the first coil, wherein
the plurality of first coils and the plurality of second coils are connected in series, the gradient magnetic field coil device further comprising
a plurality of current adjusting devices, connected to either of the first coils or the second coils in parallel, independently adjusting currents flowing through the first coils or the second coils, respectively,
wherein the plurality of first coils and the plurality of second coils are connected in series by alternately connecting a member from the first coils and a member from the second coils,

wherein the current adjusting device includes a variable resistor and a variable inductor as a variable impedance element, and wherein
a value of the variable resistor and a value of the variable inductor can be adjusted from an outside.

14. The gradient magnetic field coil device as claimed in claim 13 , wherein
the plurality of current adjusting devices includes first and second driving sources, a part of the plurality of first coils and a part of the plurality of second coils being connected in series and connected to the first driving power source, and
a remaining part of the plurality of first coils and a remaining part of the plurality of second coils are connected in series and connected to the second driving power source which is synchr

Assignees

• Imamura Yukinobu
• Abe Mitsushi
• Yatsuo Takeshi
• Terada Masanao
• Ando Ryuya
• Kawamura Takeshi
• Hitachi Ltd

Inventors

• Imamura Yukinobu
• Abe Mitsushi
• Yatsuo Takeshi
• Terada Masanao
• Ando Ryuya
• Kawamura Takeshi

Classifications

• G01R33/34007

  Manufacture of RF coils, e.g. using printed circuit board technology; additional hardware for providing mechanical support to the RF coil assembly or to part thereof, e.g. a support for moving the coil assembly relative to the remainder of the MR system · CPC title

• G01R33/56518

  due to eddy currents, e.g. caused by switching of the gradient magnetic field · CPC title

• Y10T29/49117

  Conductor or circuit manufacturing · CPC title

• G01R33/34092 Primary

  RF coils specially adapted for NMR spectrometers · CPC title

• G01R33/4215 Primary

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