RF probe for MRI

• US 5,489,847 A
• Filed: 06/01/1994
• Issued: 02/06/1996
• Est. Priority Date: 06/08/1993
• Status: Expired due to Term

• Current Assignee: Hitachi Medical Corporation (Hitachi, Ltd.)
• Original Assignee: Hitachi, Ltd., Hitachi Medical Corporation (Hitachi, Ltd.)
• Inventors: Matsunaga, Yoshikuni, Takahashi, Tetsuhiko, Nabeshima, Takayuki, Katakura, Kageyoshi, Yamamoto, Etsuji
• Primary Examiner(s): Arana, Louis M.
• Application Number:
  US08/252,624
• Time in Patent Office: 615 Days
• Field of Search: 324/318, 324/322, 324/314, 324/307, 324/309, 324/300, 128/653.5
• US Class Current: 324/318
• CPC Class Codes: G01R 33/34053 Solenoid coils; Toroidal coils
• CPC Class Codes: G01R 33/3415 comprising arrays of sub-coils , i.e. phased-array coils with flexible receiver channels
• CPC Class Codes: G01R 33/3628 Tuning/matching of the transmit/receive coil
• CPC Class Codes: G01R 33/365 Decoupling of multiple RF coils wherein the multiple RF coils have the same function in MR, e.g. decoupling of a receive coil from another receive coil in a receive coil array, decoupling of a transmission coil from another transmission coil in a transmission coil array
• CPC Class Codes: G01R 33/3678 involving quadrature drive or detection, e.g. a circularly polarized RF magnetic field

Abstract

An RF probe for MRI, in which a plurality of unit coils including conductive loops having resonance capacitors and inductors connected with the conductive loops in series are arranged so as to be distant from each other with a predetermined distance, electromagnetic coupling being produced between at least two inductors to remove electromagnetic coupling between the unit coils.

Claims

1. An RF probe for MRI comprising:

a plurality of unit coils, each of said unit coils including a conductive loop, a capacitor for resonance connected in series with the conductive loop, and an inductor connected in series with the conductive loop;

wherein said unit coils are arranged so that an electromagnetic coupling is produced between at least two of said inductors which are connected to each of said conductive loops so as to compensate for and reduce an electromagnetic coupling of at least two of said conductive loops of at least two of said unit coils.

2. An RF probe according to claim 1, wherein said plurality of unit coils are arranged so that central axes of unit coils perpendicular to planes containing conductive loops are approximately in accordance with each other.

3. An RF probe according to claim 1, wherein said plurality of unit coils are arranged with a certain interval in a direction of an RF magnetic field detected by the different unit coils.

4. An RF probe according to claim 1, wherein said plurality of unit coils are arranged with a certain interval in a direction perpendicular to a direction of an RF magnetic field detected by the different unit coils.

5. An RF probe according to claim 1, wherein said inductors are air-core coils.

6. An RF probe according to claim 5, wherein each of said air-core coils has 1-10 turns.

7. An RF probe according to claim 5, wherein each of said air-core coils has a cross-sectional area of 10-10,000 mm².

8. An RF probe according to claim 5, wherein each of said air-core coils is made of wire having a cross-sectional area of 3-100 mm².

9. An RF probe according to claim 1, wherein each of said inductors is arranged so that a direction of magnetic field generated by each of said inductors differs from a direction of magnetic field detected by each of said conductive loops.

10. An RF probe according to claim 1, wherein each of said inductors has an inductance 0.1-3 times as great as inductance of distributed constant of each of said conductive loops.

11. An RF probe according to claim 1, wherein each of said inductors is an 8-shaped inductor.

12. An RF probe according to claim 1, further comprising a magnetic shield in the neighborhood of said inductors.

13. An RF probe according to claim 1, wherein each of said conductive loops constitutes a part of a loop element of a multiple element resonator.

14. An RF probe according to claim 13, wherein said inductors include two groups of inductors, which are arranged so as to be deviated by 90°

from each other around a central axis of said multiple element resonator.

15. An RF probe according to claim 1, wherein each of said conductive loops constitutes a part of one of a loop coil, a saddle coil and a solenoid coil.

16. An RF probe according to claim 1, further comprising arranging means for arranging at least two of said inductors so that central axes of said inductors are approximately in accordance with each other.

17. An RF probe according to claim 1, further comprising regulating means for regulating a magnitude of electromagnetic coupling between at least two of said inductors.

18. An RF probe according to claim 17, wherein said regulating means varies distance between said inductors.

19. An RF probe according to claim 17, wherein said regulating means displaces central axes of said inductors.

20. An RF probe according to claim 1, further comprising an auxiliary conductive loop disposed between at least two inductors, said auxiliary conductive loop acts as an intermediary for coupling electromagnetically said inductors.

21. An RF probe according to claim 1, further comprising a second RF probe for detecting a second RF magnetic field perpendicular to direction of a first RF magnetic field detected by said RF probe which is a first RF probe.

22. An RF probe according to claim 21, wherein said second RF probe is-a saddle type coil.

23. An RF probe according to claim 21, wherein said second RF probe is an array coil.

24. An RF probe according to claim 1, wherein a magnitude of the electromagnetic coupling between at least two of said inductors is substantially equal to a magnitude of the electromagnetic coupling between the at least two conductive loops of at least two of said unit coils.

25. A RF probe according to claim 1, wherein each of said unit coils has approximately a same resonance frequency closely to each other.

26. An MRI apparatus comprising:

a receiving RF probe including a plurality of unit coils, each of said unit coils including a conductive loop, a capacitor for resonance connected in series with the conductive loop, and an inductor connected in series with the conductive loop, wherein said unit coils are arranged so that an electromagnetic coupling is produced between at least two said inductors which are connected to each of said conductive loops so as to compensate for and reduce an electromagnetic coupling of at least two said conductive loops of at least two of said unit coils;

means for receiving signals from said receiving RF probe to reconstruct an image;

means for displaying said image;

means for generating a static magnetic field;

means for generating gradient magnetic fields; and

means for generating an RF magnetic field.

27. An RF probe according to claim 26, wherein a magnitude of the electromagnetic coupling between at least two of said inductors is substantially equal to a magnitude of the electromagnetic coupling between at least two the conductive loops of at least two of said unit coils.

28. An MRI apparatus according to claim 26, wherein said means for generating an RF magnetic field comprises:

a plurality of unit coils, each of said unit coils including a conductive loop, a capacitor for resonance connected in series with the conductive loop, and an inductor connected in series with the conductive loop, wherein said unit coils are arranged so that an electromagnetic coupling is produced between at least two of said inductors which are connected to each of said conductive loops so as to compensate for and reduce an electromagnetic coupling of at least two of said conductive loops of at least two of said unit coils.

29. An RF probe according to claim 28, wherein a magnitude of the electromagnetic coupling between at least two of said inductors is substantially equal to a magnitude of the electromagnetic coupling between the conductive loops of at least two of said unit coils.

30. An MRI apparatus comprising:

means for generating an RF magnetic field including a plurality of unit coils, each of said unit coils including a conductive loop, a capacitor for resonance connected in series with the conductive loop, and an inductor connected in series with the conductive loop, wherein said unit coils are arranged so that an electromagnetic coupling is produced between at least two of said inductors which are connected to each of said conductive loops so as to compensate for and reduce an electromagnetic coupling of at least two of said conductive loops of at least two of said unit coils;

means for giving rise to electromagnetic coupling between at least two of said inductors;

a receiving RF probe;

means for receiving signals from said receiving RF probe to reconstruct an image;

means for displaying said image;

means for generating a static magnetic field; and

means for generating gradient magnetic fields.

31. An RF probe according to claim 30, wherein a magnitude of the electromagnetic coupling between at least two of said inductors is substantially equal to a magnitude of the electromagnetic coupling between the conductive loops of at least two of said unit coils.

32. An MRI comprising:

a receiving RF probe including a plurality of unit coils, each of said unit coils including a conductive loop, a capacitor for resonance connected in series with the conductive loop, and an inductor connected in series with the conductive loop, wherein said unit coils are arranged so that an electromagnetic coupling is produced between at least two of said inductors which are connected to each of said conductive loops so as to compensate for and reduce an electromagnetic coupling of at least two of said conductive loops of at least two of said unit coils;

means for regulating a magnitude of the electromagnetic coupling between at least two of said inductors;

means for receiving signals from said receiving RF probe to reconstruct an image;

means for displaying said image;

means for generating a static magnetic field;

means for generating gradient magnetic fields; and

means for generating an RF magnetic field.

33. An MRI comprising:

means for generating an RF magnetic field including a plurality of unit coils, each of said unit coils including a conductive loop, a capacitor for resonance connected in series with the conductive loop, and an inductor connected in series with the conductive loop, wherein said unit coils are arranged so that an electromagnetic coupling is produced between at least two of said inductors which are connected to each of said conductive loops so as to compensate for and reduce an electromagnetic coupling of at least two of said conductive loops of at least two of said unit coils;

means for regulating a magnitude of the electromagnetic coupling between at least two of said inductors;

means for receiving signals from said receiving RF probe to reconstruct an image;

means for displaying said image;

means for generating a static magnetic field; and

means for generating gradient magnetic fields.

34. An RF probe for MRI comprising a plurality of unit coils, each of said unit coils including a conductive loop, a capacitor for resonance connected in series with the conductive loop, and an inductor connected in series with the conductive loop, wherein said unit coils are arranged proximate to each other so as to reduce an electromagnetic coupling of at least two of said unit coils.