Radio-frequency magnetic field regulating apparatus for magnetic resonance imaging

• US 5,227,727 A
• Filed: 12/17/1991
• Issued: 07/13/1993
• Est. Priority Date: 06/20/1991
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Segawa, Toru, Makita, Junichi
• Primary Examiner(s): Tokar, Michael J.
• Application Number:
  US07/809,730
• Time in Patent Office: 574 Days
• Field of Search: 324/300, 324/307, 324/309, 324/318, 324/322, 128/653.5, 128/653.2
• US Class Current: 324/318
• CPC Class Codes: G01R 33/36 Electrical details, e.g. matching or coupling of the coil to the receiver
• CPC Class Codes: G01R 33/5659 caused by a distortion of the RF magnetic field, e.g. spatial inhomogeneities of the RF magnetic field G01R33/56509, G01R33/56518, G01R33/56536 take precedence

Abstract

Between at least one of a transmitting coil and a receiving coil and a subject to be examined is interposed a member containing a high molecular compound such as a molded sheet of nonconductive fiber or rubber, a PVA gel sheet or a PAR gel sheet. Thereby, the radio-frequency magnetic field distribution can be regulated with ease without adjusting hardware or software of a magnetic resonance diagnostic apparatus, thus permitting diagnosises to be made with high accuracy.

Claims

1. For use in a magnetic resonance diagnostic apparatus which produces a magnetic resonance phenomenon in a specific region of a subject to be examined placed in a static magnetic field by irradiating said subject with an excitation radio-frequency pulse from a transmitting coil and collecting magnetic resonance signals produced by the magnetic resonance phenomenon by using a receiving coil, thereby obtaining diagnostic information on said specific region, a radio-frequency magnetic field regulating device comprising a member interposed between at least one of said transmitting and receiving coils and said subject to be examined and having dielectric property.

2. A radio-frequency magnetic field regulating device according to claim 1, in which said member includes a conductive substance.

3. A radio-frequency magnetic field regulating device according to claim 1, in which said member includes an electrolytic aqueous solution.

4. A radio-frequency magnetic field regulating device according to claim 1, in which said member comprises a high molecular material containing an electrolytic aqueous solution.

5. A radio-frequency magnetic field regulating device according to claim 4, in which said electrolytic aqueous solution is an inorganic ion aqueous solution such as Na⁺, K⁺, Ca²⁺ or Cl^-.

6. A radio-frequency magnetic field regulating device according to claim 4, in which said high molecular gel material is a poly-acryl resin.

7. A radio-frequency magnetic field regulating device according to claim 4, in which said high molecular gel material is poly-vinyl alcohol.

8. A radio-frequency magnetic field regulating device according to claim 1, in which said substance has a property for growing a region where the flux density of a radio-frequency magnetic field near said member is increased.

9. For use in a magnetic resonance diagnostic apparatus which produces a magnetic resonance phenomenon in a specific region of a subject to be examined placed in a static magnetic field by irradiating said subject with an excitation radio-frequency pulse from a transmitting coil and collecting magnetic resonance signals produced by the magnetic resonance phenomenon by using a receiving coil, thereby obtaining diagnostic information on said specific region, a radio-frequency magnetic field regulating device comprising a member interposed between at least one of said transmitting and receiving coils and said subject to be examined and formed by molding a non-magnetic conductive metal into a predetermined shape with a molding material.

10. A radio-frequency magnetic field regulating device according to claim 9, in which said non-magnetic conductive metal is in the form of foil.

11. A radio-frequency magnetic field regulating device according to claim 9, in which said non-magnetic conductive metal is in the form of a mesh sheet for RF shielding.

12. A radio-frequency magnetic field regulating device according to claim 9, in which said molding material is a nonconductive fiber high molecular compound.

13. A radio-frequency magnetic field regulating device according to claim 9, in which said molding material is a rubber high molecular compound.

14. A radio-frequency magnetic field regulating device according to claim 9, in which said predetermined shape is the shape of a sheet.

15. For use in a magnetic resonance diagnostic apparatus which produces a magnetic resonance phenomenon in a specific region of a subject to be examined placed in a static magnetic field by irradiating said subject with an excitation radio-frequency pulse from a transmitting coil and collecting magnetic resonance signals produced by the magnetic resonance phenomenon by using a receiving coil, thereby obtaining diagnostic information on said specific region, a radio-frequency magnetic field regulating device comprising a member interposed between at least one of said transmitting and receiving coils and said subject to be examined and formed by filling a bag with a non-magnetic conductive gel material.

16. A radio-frequency magnetic field regulating device according to claim 15, in which said bag is formed of a high-molecular compound.

17. A radio-frequency magnetic field regulating device according to claim 15, in which said bag is formed of rubber.

18. A radio-frequency magnetic field regulating device according to claim 15, in which said non-magnetic conductive gel material is formed of a high-molecular compound impregnated with an inorganic electrolytic ion aqueous solution.

19. A radio-frequency magnetic field regulating device according to claim 18, in which said high molecular compound is poly-vinyl alcohol.

20. A radio-frequency magnetic field regulating device according to claim 18, in which said inorganic electrolytic ion aqueous solution contains at least one of Na⁺, K⁺, Ca²⁺ or Cl^-.

21. For use in a magnetic resonance diagnostic apparatus which produces a magnetic resonance phenomenon in a specific region of a subject to be examined placed in a static magnetic field by irradiating said subject with an excitation radio-frequency pulse from a transmitting coil and collecting magnetic resonance signals produced by the magnetic resonance phenomenon by using a receiving coil, thereby obtaining diagnostic information on said specific region, a radio-frequency magnetic field regulating device comprising a bag interposed between at least one of said transmitting and receiving coils and said subject to be examined and filled with a high molecular compound impregnated with an inorganic electrolytic ion aqueous solution.

22. A radio-frequency magnetic field regulating device according to claim 21, in which said high molecular compound is a poly-acryl resin.

23. A radio-frequency magnetic field regulating device according to claim 21, in which said inorganic electrolytic ion aqueous solution contains at least one of Na⁺, K⁺, Ca²⁺ or Cl^-.