System and method for electromagnet coil construction and operation

Patent metadata

Field	Value
Publication number	US-9842689-B2
Application number	US-201414894212-A
Country	US
Kind code	B2
Filing date	Dec 9, 2014
Priority date	Dec 9, 2014
Publication date	Dec 12, 2017
Grant date	Dec 12, 2017

Abstract

A method of manufacturing electromagnet coils for use in a magnetic resonance imaging (MRI) system is provided. The method comprises forming a coil representation of a coil surface for the electromagnet coils; setting a plurality of performance metric requirements for a plurality of performance metrics for the electromagnet coils, the plurality of performance metrics including a magnetic field-shape metric and an eddy-field metric; forming a performance functional, based on the coil representation and the plurality of performance metrics, for generating a current density pattern over the coil surface; optimizing the performance functional based on the plurality of performance metric requirements; generating a current density pattern over the coil surface based on the minimized performance functional; and obtaining coil windings from the current density pattern.

First claim

We claim:

1. A method of manufacturing electromagnet coils for use in a magnetic resonance imaging (MRI) system, the method comprising:
forming a coil representation of a coil surface for the electromagnet coils;
setting a plurality of performance metric requirements for a plurality of performance metrics for the electromagnet coils, the plurality of performance metrics including a magnetic field-shape metric and an eddy-field metric;
forming a performance functional, based on the coil representation and the plurality of performance metrics, for generating a current density pattern over the coil surface;
optimizing the performance functional based on the plurality of performance metric requirements;
generating a current density pattern over the coil surface based on an optimized performance functional;
obtaining coil windings from the current density pattern;
wherein optimizing the performance functional further comprises optimizing a predicted eddy-current density pattern generated over an eddy-field producing structure surface based on the performance metrics as functions; and
wherein the eddy-field metric is a predetermined eddy field shape and optimizing of the performance functional further comprises constraining an eddy current density representation over an eddy-field producing structure surface such that eddy fields predicted by the eddy-current density representation take on the predetermined eddy field shape.

2. The method of claim 1 wherein the current density pattern is based on a stream function.

3. The method of claim 1
wherein the magnetic field-shape metric further comprises a target magnetic field; and
wherein the optimizing of the performance functional further comprises optimizing the difference between the target magnetic field and a predicted magnetic field generated based on the performance.

4. The method of claim 1
wherein the eddy-field metric further comprises a target eddy field shape; and
wherein the optimizing of the performance functional further comprises optimizing the difference between the target eddy field shape and a predicted eddy field generated based on the performance functional.

5. The method of claim 1 wherein the eddy-current density representation is based on a linearly independent basis set of stream function modes, and wherein the constraining further comprises suppressing one or more of the stream function modes.

6. The method of claim 5 wherein the MRI system further comprises correction coils and wherein the suppressed stream function modes correspond to modes that are uncorrectable by a combination of the correction coils and the gradient coils.

7. The method of claim 1 wherein the performance metrics can further comprise at least one of: a net force metric, a net torque metric, a dissipative power metric and an energy metric.

8. The method of claim 1 further comprising:
forming a plurality of performance metric functions based on the plurality of performance metrics, and
wherein the performance functional is formed from the plurality of performance metric functions.

9. The method of claim 1 wherein the coil representation is based on a boundary element method.

10. The method of claim 1 wherein the coil surface is cylindrical.

11. The method of claim 1 wherein the eddy-field producing structure is at least one of a bore of a main magnet and end flanges of a main magnet.

12. A method of manufacturing electromagnet coils for use in a magnetic resonance imaging (MRI) system, the method comprising:
forming a coil representation of a coil surface for the electromagnet coils;
setting a plurality of performance metric requirements for a plurality of performance metrics for the electromagnet coils, the plurality of performance metrics including a magnetic field-shape metric and an eddy-field metric;
forming a performance functional, based on the coil representation and the plurality of performance metrics, for generating a current density pattern over the coil surface;
optimizing the performance functional based on the plurality of performance metric requirements;
generating a current density pattern over the coil surface based on an optimized performance functional;
obtaining coil windings from the current density pattern;
wherein optimizing the performance functional further comprises optimizing a predicted eddy-current density pattern generated over an eddy-field producing structure surface based on the performance metrics as functions;
generating simulated eddy currents based on the optimized performance functional;
determining compensation currents based on the simulated eddy currents for correcting eddy fields producible by the simulated eddy currents; and wherein the electromagnet coils are gradient coils and wherein determining further comprises:
when the MRI is constructed:
measuring the time and spatial variations of the eddy currents for a pulse sequence; and
determining the compensation currents based on the measured time and spatial variations of the eddy currents for the pulse sequence.

13. The method of claim 12 wherein the electromagnet coils are gradient coils and the compensation currents are to be generated by gradient coils during the operation of the MRI.

14. The method of claim 12 wherein the electromagnet coils are gradient coils, the MRI further includes correction coils and the compensation currents are to be generated by a combination of the gradient coils and the correction coils during the operation of the MRI.

15. The method of claim 12 wherein the determining further comprises:
optimizing the eddy fields producible by the simulated eddy currents.

16. The method of claim 12 further comprising:
after the determining, storing the compensation currents in association with the pulse sequence.

17. The method of claim 12 wherein the electromagnet coils are one of a main magnet, gradient coils and correction coils.

18. An MRI system manufactured in accordance with the method of claim 12 .

Assignees

• Bindseil Geron André
• Harris Chad Tyler
• Handler William Bradfield
• Chronik Blaine Alexander
• Synaptive Medical Barbados Inc

Inventors

• Bindseil Geron André
• Harris Chad Tyler
• Handler William Bradfield
• Chronik Blaine Alexander

Classifications

• G01R33/385

  using gradient magnetic field coils · CPC title

• H01F41/04 Primary

  for manufacturing coils {(coils for transformer or inductances H01F27/28)} · CPC title

• G01R33/28 Primary

  Details of apparatus provided for in groups G01R33/44 - G01R33/64 · CPC title

• G01R33/381

  using electromagnets · CPC title

• G01R33/3854

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