Radio frequency coil tuning methods and apparatus

• US 10,551,452 B2
• Filed: 09/29/2017
• Issued: 02/04/2020
• Est. Priority Date: 09/29/2016
• Status: Active Grant

• Current Assignee: Hyperfine Operations Incorporated
• Original Assignee: Hyperfine Research, Inc.
• Inventors: Rearick, Todd, Jordan, Jeremy Christopher, Charvat, Gregory L., Rosen, Matthew Scot
• Primary Examiner(s): Assouad, Patrick
• Assistant Examiner(s): Pretlow, Demetrius R
• Application Number:
  US15/720,245
• Publication Number:
  US 20180088193A1
• Time in Patent Office: 858 Days
• Field of Search: 324314
• CPC Class Codes: G01R 33/24 for measuring direction or magnitude of magnetic fields or magnetic flux
• CPC Class Codes: G01R 33/3628 Tuning/matching of the transmit/receive coil
• CPC Class Codes: G01R 33/445 MR involving a non-standard magnetic field B0, e.g. of low magnitude as in the earth's magnetic field or in nanoTesla spectroscopy, comprising a polarizing magnetic field for pre-polarisation, B0 with a temporal variation of its magnitude or direction such as field cycling of B0 or rotation of the direction of B0, or spatially inhomogeneous B0 like in fringe-field MR or in stray-field imaging
• CPC Class Codes: G01R 33/583 Calibration of signal excitation or detection systems, e.g. for optimal RF excitation power or frequency G01R33/246 takes precedence

Abstract

Some aspects comprise a tuning system configured to tune a radio frequency coil for use with a magnetic resonance imaging system comprising a tuning circuit including at least one tuning element configured to affect a frequency at which the radio frequency coil resonates, and a controller configured to set at least one value for the tuning element to cause the radio frequency coil to resonate at approximately a Larmor frequency of the magnetic resonance imaging system determined by the tuning system. Some aspects include a method of automatically tuning a radio frequency coil comprising determining information indicative of a Larmor frequency of the magnetic resonance imaging system, using a controller to automatically set at least one value of a tuning circuit to cause the radio frequency coil to resonate at approximately the Larmor frequency based on the determined information.

Claims

1. A method of automatically tuning a radio frequency coil for use with a magnetic resonance imaging system using a tuning system comprising a tuning circuit connected to the radio frequency coil, the method comprising:

determining information indicative of a Larmor frequency of the magnetic resonance imaging system; and

using a controller to automatically set at least one value of the tuning circuit to cause the radio frequency coil to resonate at approximately the Larmor frequency based on the determined information, wherein;

the tuning circuit comprises at least one tuning element arranged across a first output and a second output of the tuning circuit,

the tuning system further comprises an output connector connected to the first output and the second output of the tuning circuit, and

the output connector is configured to connect to a coil connector of the radio frequency coil.

2. The method of claim 1, wherein determining information indicative of the Larmor frequency comprises estimating an actual Larmor frequency of the magnetic resonance system.

3. The method of claim 2, wherein estimating an actual Larmor frequency comprises measuring magnetic resonance signals emitted from a sample.

4. The method of claim 1, wherein determining information indicative of a Larmor frequency comprises measuring a current B₀ magnetic field strength produced by the magnetic resonance imaging system.

5. The method of claim 1, wherein determining information indicative of the Larmor frequency comprises receiving information indicating a desired Larmor frequency and/or a desired B₀ magnetic field strength produced by a B₀ magnet of the magnetic resonance imaging system.

6. The method of claim 5, wherein the information indicating the desired Larmor frequency and/or the desired B₀ magnetic field strength produced by the B₀ magnet is received from a coil connector of the radio frequency coil.

7. The method of claim 5, wherein the information indicating the desired Larmor frequency and/or the desired B₀ magnetic field strength produced by the B₀ magnet is received from a console of the magnetic resonance imaging system.

8. The method of claim 7, wherein determining the current resonant frequency of the radio frequency coil comprises identifying a frequency in spectra of the detected electromagnetic noise at which the radio frequency coil exhibited a maximum response.

9. The method of claim 1, further comprising:

controlling the radio frequency coil to detect electromagnetic noise;

determining a current resonant frequency of the radio frequency coil based on the detected electromagnetic noise,

wherein the determined current resonant frequency is used by the controller to set the at least one value of the tuning element.

10. The method of claim 1, wherein using the controller comprises using the controller to set at least one value of the at least one tuning element of the tuning circuit to cause the radio frequency coil to resonate at approximately the Larmor frequency.

11. A tuning system configured to tune a radio frequency coil for use with a magnetic resonance imaging system, the tuning system comprising:

a tuning circuit including at least one tuning element configured to affect a frequency at which the radio frequency coil resonates; and

a controller configured to set at least one value for the tuning element to cause the radio frequency coil to resonate at approximately a Larmor frequency of the magnetic resonance imaging system determined by the tuning system, wherein;

the at least one tuning element is arranged across a first output and a second output of the tuning circuit;

the tuning system further comprises an output connector connected to the first output and the second output of the tuning circuit; and

the output connector is configured to connect to a coil connector of the radio frequency coil.

12. The tuning system of claim 11, wherein the information indicative of the Larmor frequency is determined by the tuning system at least in part by estimating an actual Larmor frequency of the magnetic resonance system.

13. The tuning system of claim 12, wherein estimating an actual Larmor frequency comprises measuring magnetic resonance signals emitted from a sample using the radio frequency coil.

14. The tuning system of claim 11, wherein the information indicative of the Larmor frequency is determined by the tuning system at least in part by measuring a current B₀ magnetic field strength produced by the magnetic resonance imaging system using at least one sensor.

15. The tuning system of claim 11, wherein the information indicative of the Larmor frequency is determined by the tuning system at least in part by receiving information indicating a desired Larmor frequency and/or a desired B₀ magnetic field strength produced by a B₀ magnet of the magnetic resonance imaging system.

16. The tuning system of claim 15, wherein the information indicating the desired Larmor frequency and/or the desired B₀ magnetic field strength produced by the B₀ magnet is received from a coil connector of the radio frequency coil.

17. The tuning system of claim 15, wherein the information indicating the desired Larmor frequency and/or the desired B₀ magnetic field strength produced by the B₀ magnet is received from a console of the magnetic resonance imaging system.

18. The tuning system of claim 11, wherein the controller is configured to control the radio frequency coil to detect electromagnetic noise in an environment of the magnetic resonance imaging system, and to determine a current resonant frequency of the radio frequency coil based on the detected electromagnetic noise, wherein the determined current resonant frequency is used by the controller to set the at least one value of the tuning element.

19. The tuning system of claim 18, wherein the controller is configured to identify a frequency in spectra of the detected electromagnetic noise at which the radio frequency coil exhibited a maximum response.

20. The tuning system of claim 11, wherein the tuning circuit comprises a balanced tuning network.

21. The tuning system of claim 11, wherein the at least one tuning element comprises at least one configurable tuning element comprising a variable capacitor, and wherein the controller is configured to send at least one control instruction to drive one or more motors adapted to set the at least one value for the at least one configurable tuning element.

22. The tuning system of claim 11, wherein the at least one tuning element comprises a switched network of fixed-value capacitors, wherein the switched network includes a plurality of capacitive branches, and wherein the controller is configured to control the state of switches in each of the plurality of capacitive branches to set the value for the resonance tuning element.

23. The tuning system of claim 11, wherein the at least one tuning element includes a first coupling tuning element arranged between a first input of the tuning circuit and the first output of the tuning circuit and a second coupling tuning element arranged between a second input of the tuning circuit and the second output of the tuning circuit.

24. The tuning system of claim 23, wherein the first coupling tuning element and/or the second coupling tuning element comprises a variable capacitor, and wherein the controller is configured to send at least one control instruction to drive one or more motors adapted to set a value for the first coupling tuning element and/or the second coupling tuning element.

25. The tuning system of claim 23, wherein the first coupling tuning element and/or the second coupling tuning element comprises a switched network of fixed-value capacitors, wherein the switched network includes a plurality of capacitive branches, and wherein the controller is configured to control the state of switches in each of the plurality of capacitive branches to set a value for the first coupling tuning element and/or the second coupling tuning element.

26. The tuning system of claim 11, further comprising a storage device associated with the controller and configured to store a data structure, wherein the controller is further configured to set the at least one value of the at least one tuning element based, at least in part, on at least one value stored in the data structure.

27. The tuning system of claim 26, wherein the data structure is configured to store a correspondence between Larmor frequencies and capacitance values for at least one tuning element of the tuning circuit.

28. The tuning system of claim 11, wherein the tuning circuit is configured to tune receive-only radio frequency coils for use with the magnetic resonance imaging system.

29. The tuning system of claim 28, wherein the at least one tuning element comprises a switched network of fixed-value capacitors, wherein the switched network includes a plurality of capacitive branches, and wherein the controller is configured to control the state of switches in each of the plurality of capacitive branches to set the value for the resonance tuning element.

30. The tuning system of claim 11, wherein the tuning circuit is configure to tune transmit/receive radio frequency coils for use with the magnetic resonance imaging system.

31. The tuning system of claim 11, wherein the magnetic resonance imaging system is a low-field magnetic resonance imaging system.

32. The tuning system of claim 31, wherein the desired field strength is less than or equal to approximately 0.2 T and greater than or equal to approximately 0.1 T.

33. The tuning system of claim 31, wherein the desired field strength is less than or equal to approximately 0.1 T and greater than or equal to approximately 50 mT.

34. The tuning system of claim 31, wherein the desired field strength is less than or equal to approximately 50 mT and greater than or equal to approximately 20 mT.

35. The tuning system of claim 31, wherein the desired field strength is less than or equal to approximately 20 mT and greater than or equal to approximately 10 mT.

36. A magnetic resonance imaging system, comprising:

a B₀ magnet configured to provide a B₀ field;

at least one radiofrequency coil; and

a tuning system configured to tune the at least one radio frequency coil, the tuning system comprising;

a tuning circuit including at least one tuning element configured to affect a frequency at which the radio frequency coil resonates wherein the at least one tuning element is arranged across a first output and a second output of the tuning circuit; and

a controller configured to set at least one value for the tuning element to cause the radio frequency coil to resonate at approximately a Larmor frequency of the magnetic resonance imaging system determined by the tuning system; and

an output connector connected to the first output and the second output of the tuning circuit, wherein the output connector is configured to connect to a coil connector of the radio frequency coil.