Force-compensated gradient coil

Patent metadata

Field	Value
Publication number	US-10036788-B2
Application number	US-201214352771-A
Country	US
Kind code	B2
Filing date	Nov 19, 2012
Priority date	Dec 1, 2011
Publication date	Jul 31, 2018
Grant date	Jul 31, 2018

Abstract

A cylindrical superconducting magnet system for use in magnetic resonance imaging has axially aligned primary superconducting coils that are situated within an outer vacuum chamber (OVC). A thermal radiation shield surrounds the primary superconducting coils within the OVC. A primary gradient coil assembly is axially aligned with the primary superconducting coils and is situated radially within the primary superconducting coils. The cylindrical superconducting magnetic system also includes a secondary gradient coil assembly, that is radially situated outside of the primary superconducting coils and that is mechanically attached to the primary gradient coil assembly.

First claim

I claim as my invention:

1. A cylindrical superconducting magnet system for use in magnetic resonance imaging, comprising:
axially aligned primary superconducting coils, situated within an outer vacuum chamber (OVC);
a thermal radiation shield surrounding the primary superconducting coils, within the OVC;
a primary gradient coil assembly axially aligned with the primary superconducting coils and located radially within the primary superconducting coils, a secondary gradient coil assembly radially situated outside of the primary superconducting coil assembly and mechanically attached to the primary gradient coil assembly; and
said primary gradient coil assembly comprising primary gradient coils and said second gradient coil assembly comprising secondary gradient coils, and said primary gradient coils and said second gradient coils being connected in series.

2. A cylindrical superconducting magnet system according to claim 1 wherein the OVC is supported on a support surface, and the primary and secondary gradient coil assemblies are supported on the support surface independently of the OVC.

3. A cylindrical superconducting magnet system according to claim 1 , further comprising a cryogen vessel housing the primary superconducting coils, with the thermal radiation shield surrounding the cryogen vessel, within the OVC.

4. A cylindrical superconducting magnet system according to claim 1 , wherein the OVC comprises a bore tube, an outer cylindrical wall and annular end pieces, wherein at least one of the end pieces has a re-entrant portion defining a recess, and the secondary gradient coil assembly is situated within the recess.

5. A cylindrical superconducting magnet system according to claim 4 , wherein said secondary gradient coil assembly is a first secondary gradient coil assembly, and comprising a second secondary gradient coil assembly, and wherein each of said end pieces has a re-entrant portion defining a recess, and the first secondary gradient coil assembly is situated within the recess of one of said end pieces and the second secondary gradient coil assembly is situated in the recess of the other of said end pieces.

6. A cylindrical superconducting magnet system according to claim 5 wherein at least one secondary gradient coil assembly is mechanically attached to the primary gradient coil assembly by mechanical attachments that pass through through-holes proceeding through the OVC, and the thermal radiation shield.

7. A cylindrical superconducting magnet system according to claim 6 , wherein the mechanical attachments pass between adjacent primary superconducting coils.

8. A cylindrical superconducting magnet system according to claim 6 , wherein the through-holes in the OVC are sealed by radially-directed cross-tubes extending between a bore tube of the OVC and the recess, and in which the mechanical attachments pass through the cross-tubes.

9. A cylindrical superconducting magnet system according to claim 8 , wherein the through-holes in the thermal radiation shield are sealed by radially-directed cross-tubes extending coaxially with the cross-tubes sealing the OVC.

10. A cylindrical superconducting magnet system according to any of claims 4 - 9 , wherein:
one of the end pieces of the OVC has a single recess extending axially along the length of the primary gradient coil assembly; and
the secondary gradient coil assembly extends axially along a length of the primary gradient coil assembly, mechanically attached to the primary gradient coil assembly at at least two axial positions, either side of a center line.

11. A cylindrical superconducting magnet system according to claim 10 , comprising superconducting shield coils, situated radially outside of the primary superconducting coils and the secondary gradient coil assembly, an intermediate support piece mechanically attached to and sealed to the OVC, and a mechanical support structure on which the superconducting shield coils are mounted, the mechanical support structure being supported on the intermediate support piece.

12. A cylindrical superconducting magnet system according to claim 11 , comprising an annular magnet connection structure situated at the axial end of the magnet structure away from the recess, that mechanically connects the superconducting shield coils to the primary magnet coils with annular parts of the thermal radiation shield, and annular parts of the OVC enclosing the annular magnet connection structure and completing the thermal radiation shield and OVC respectively.

13. A cylindrical superconducting magnet system according to claim 1 wherein the OVC has bore tubes therein and wherein, in use, the secondary gradient coil assembly induces eddy currents in material of the bore tubes of the OVC and the thermal radiation shield that oppose eddy currents induced in said bore tubes by the primary gradient coil assembly.

14. A method for operating a cylindrical superconducting magnet system for magnetic resonance imaging, said cylindrical superconducting magnet system comprising axially aligned primary superconducting coils, situated within an outer vacuum chamber (OVC), a thermal radiation shield surrounding the primary superconducting coils, within the OVC, a primary gradient coil assembly axially aligned with the primary superconducting coils and located radially within the primary superconducting coils, a secondary gradient coil assembly radially situated outside of the primary superconducting coil assembly and mechanically attached to the primary gradient coil assembly, said method comprising:
generating synchronized currents; and
balancing forces acting on at least one of said OVC and said thermal radiation shield by causing said synchronized currents to flow in a same direction in each of said primary gradient coil assembly and said secondary gradient coil assembly.

Assignees

• Calvert Simon James
• Siemens Healthcare Ltd

Inventors

• Calvert Simon James

Classifications

• G01R33/3815 Primary

  with superconducting coils, e.g. power supply therefor · CPC title

• G01R33/3854 Primary

  means for active and/or passive vibration damping or acoustical noise suppression in gradient magnet coil systems · CPC title

• G01R33/3858

  Manufacture and installation of gradient coils, means for providing mechanical support to parts of the gradient-coil assembly (manufacture of inductances or coils in general H01F41/00) · CPC title