Coil structure with tapered conductive members for improved homogeneity in MRI

• US 6,831,460 B2
• Filed: 02/05/2002
• Issued: 12/14/2004
• Est. Priority Date: 11/25/1998
• Status: Expired due to Fees

• Current Assignee: Medrad Incorporated (Bayer AG)
• Original Assignee: Medrad Incorporated (Bayer AG)
• Inventors: Misic, George J., Monski, William J., Reid, Eric D., Reisker, Theodore J.
• Primary Examiner(s): Shrivastav, Brij B.
• Application Number:
  US10/068,300
• Publication Number:
  US 20030071622A1
• Time in Patent Office: 1,043 Days
• Field of Search: 324/318, 324/320-322, 324/309, 324/307, 324/306, 324/300, 400/421
• US Class Current: 324/318
• CPC Class Codes: G01R 33/34046 Volume type coils, e.g. bird-cage coils; Quadrature bird-cage coils; Circularly polarised coils

Abstract

A coil for creating improved homogeneity in magnetic flux density in a radio frequency resonator for magnetic resonance imaging and spectroscopy of the human head. The coil has a plurality of conductive members. Each of the conductive members has a linear portion and a tapered portion. The conductive members are arranged to form a first opening having a first diameter and a second opening having a second diameter, with the second diameter being different from the first diameter. The tapered portions of the conductive members provide the coil with a substantially homogeneous pattern of magnetic flux density in at least one of three orthogonal imaging planes of the coil.

Claims

1. A coil for use with a magnetic resonance imaging (MRI) system to form images of a region of a patient during an MRI scanning procedure, said coil comprising:

(a) a first ring at one end of said coil, said first ring being electrically conductive and having a first diameter;

(b) a second ring at an other end of said coil, said second ring being electrically conductive and having a second diameter different from said first diameter of said first ring; and

(c) a plurality of rods electrically interconnecting said first and said second rings to form said coil therewith, each of said rods having a linear portion and a tapered portion with said linear portion being connected to said first ring and said tapered portion being connected to said second ring, said tapered portions of said rods configured to provide said coil with a substantially homogeneous pattern of magnetic flux density in at least one of an XZ imaging plane and a YZ imaging plane of said coil.

2. The coil claimed in claim 1, wherein said coil is a birdcage coil.

3. The coil claimed in claim 1, wherein said second diameter of said second ring is smaller than said first diameter of said first ring.

4. The coil claimed in claim 1 wherein said tapered portion of each of said rods comprises at least one angled linear segmented section.

5. The coil claimed in claim 1 wherein said first ring and said second ring are each larger in diameter than a center of said coil to thereby enable a concentration of said magnetic flux density to be produced at a region centered within said coil.

6. The coil claimed in claim 1, further comprising at least one additional coil at least partially overlapping said coil at an inferior end thereof to form therewith, and for operation as, a phased array.

7. The coil claimed in claim 1, wherein said first and said second rings are circular.

8. The coil claimed in claim 1 wherein said first and said second rings are elliptical with said first diameter being a major diameter of said first ring and said second diameter being a major diameter of said second ring.

9. The coil claimed in claim 1 wherein said coil is a receive-only coil.

10. The coil claimed in claim 1 wherein said coil is a transmit/receive coil.

11. The coil claimed in claim 1 wherein each of said rods and said first and said second rings contain therein a plurality of reactive electrical components.

12. The coil claimed in claim 1 wherein said coil is configured as one of a low pass coil, a high pass coil and a band pass coil.

13. The coil claimed in claim 1 wherein said coil is operable in one of a linear mode and a quadrature mode.

14. A coil for use with a magnetic resonance imaging (MRI) system to form images of a region of a patient during an MRI scanning procedure, said coil comprising:

(a) a first ring at one end of said coil, said first ring being electrically conductive and having a first diameter;

(b) a second ring at an other end of said coil, said second ring being electrically conductive and having a second diameter; and

(c) a plurality of rods electrically interconnecting said first and said second rings to form said coil therewith, each of said rods having a linear portion and at each end thereof a tapered portion to which said first and said second rings respectively connect, said tapered portions being selected to provide said coil with a subsantially homogeneous pattern of magnetic flux density in at least one of an XZ imaging plane and a YZ imaging plane of said coil.

15. The coil claimed in claim 14 wherein said first and said second diameters of said first and said second rings, respectively, are equal.

16. The coil claimed in claim 14 wherein said first and said second diameters are each larger than a diameter at a center of said coil such that said tapered portions of said rods are tapered outwardly.

17. The coil claimed in claim 14 wherein said first and said second diameters are each smaller than a diameter at a center of said coil such that said tapered portions of said rods are tapered inwardly.

18. The coil claimed in claim 14 wherein said coil is a birdcage coil.

19. A coil for use with a magnetic resonance (MR) system, said coil comprising:

(a) a plurality of conductors arranged to form a first opening at one end having a first diameter and a second opening at an other end having second diameter different from said first diameter; and

(b) at least some of said conductors each having a linear portion a tapered portion, with said tapered portions of said conductors providing said coil with a substantially homogeneous pattern of magnetic flux density in at least one of an XZ imaging plane and a YZ imaging plane of said coil.

20. The coil claimed in claim 19 wherein said coil is a birdcage coil.

21. The coil claimed in claim 19 wherein said second diameter of said second opening is smaller than said first diameter of said first opening.

22. The coil claimed in claim 19 wherein said tapered portion of each of said at least some of said conductors comprises at least one angled linear segmented section.

23. The coil claimed in claim 19 wherein said plurality of conductors includes a first conductive ring defining said first opening and a second conductive ring defining said second opening, with said linear and said tapered portions of each of said at least some of said conductors being serially connected and thus electrically interconnecting said first and said second conductive rings.

24. The coil claimed in claim 19 wherein said first opening is adapted for accommodating insertion of a head of a patient into said coil.

25. The coil claimed in claim 19 wherein said conductors of said coil are supported by a housing therefor.

26. The coil claimed in claim 19 wherein said first and said second openings are circular.

27. The coil claimed in claim 19 wherein said first and said second openings are elliptical with said first diameter being a major diameter of said first opening and said second diameter being a major diameter of said second opening.

28. The coil claimed in claim 19 wherein said coil is a receive-only coil.

29. The coil claimed in claim 19 where said coil is a transmit/receive coil.

30. The coil claimed in claim 19 wherein said conductors contain therein a plurality of reactive electrical components.

31. The coil claimed in claim 19 wherein said coil is configured as one of a low pass coil, a high pass coil and a band pass coil.

32. The coil claimed in claim 19 wherein said coil is operable in one of a linear mode and a quadrature mode.

33. A coil for use with a magnetic resonance (MR) system, said coil comprising:

(a) a first end defining a first opening having a first diameter;

(b) a second end defining a second opening having a second diameter different from said first diameter; and

(c) a plurality of conductive rods extending between said first and said second ends, each of said conductive rods having a linear portion and a tapered portion with said linear portion extending from said first end and said tapered portion extending from said second end, said tapered portions of said conductive rods providing said coil with a substantially homogeneous pattern of magnetic flux density in at least one of an XZ imaging plane and a YZ imaging plane of said coil.

34. The coil claimed in claim 33 wherein said coil is a birdcage coil.

35. The coil claimed in claim 33 wherein said second diameter of said second end is smaller than said first diameter of said first end.

36. The coil claimed in claim 33 wherein said tapered portion of each of said conductive rods comprises at least one angled linear segmented section.

37. The coil claimed in claim 33 wherein said first end includes a first conductive ring and said second end includes a second conductive ring, with said conductive rods electrically interconnecting said first and said second conductive rings.

38. The coil claimed in claim 37 wherein said first conductive ring and said second conductive ring are each larger in diameter than a center of said coil to thereby enable a concentration of said magnetic flux density to be produced at a region centered within said coil.

39. The coil claimed in claim 33 further comprising at least one additional coil at least partially overlapping said coil at an inferior end thereof to form therewith, and for operation as, a phased array.

40. The coil claimed in claim 33 wherein said first and said second ends are circular.

41. The coil claimed in claim 33 wherein said first and said second ends are elliptical with said first diameter being a major diameter of said first end and said second diameter being a major diameter of said second end.

42. The coil claimed in claim 33 wherein said coil is a receive-only coil.

43. The coil claimed in claim 33 where said coil is a transmit/receive coil.

44. The coil claimed in claim 37 wherein each of said conductive rods and said first and said second conductive rings contain therein a plurality of reactive electrical components.

45. The coil claimed in claim 33 wherein said coil is configured as one of a low pass coil, a high pass coil and a band pass coil.

46. The coil claimed in claim 33 wherein said coil is operable in one of a linear mode and a quadrature mode.

47. A coil for use with a magnetic resonance (MR) system, said coil comprising:

(a) a first end defining a first opening having a first diameter;

(b) a second end defining a second opening having a second diameter; and

(c) a plurality of conductive rods extending between said first and said second ends, each of said conductive rods having a linear portion and at each end thereof a tapered portion, said tapered portions being selected to provide said coil with a subsantially homogeneous pattern of magnetic flux density in at least one of an XZ imaging plane and a YZ imaging plane of said coil.

48. The coil claimed in claim 47 wherein said first and said second diameters of said first and said second ends, respectively, are equal.

49. The coil claimed in claim 47 wherein said first and said second diameters are each larger than a diameter at a center of said coil such that said tapered portions of said conductive rods are tapered outwardly.

50. The coil claimed in claim 47 wherein said first and said second diameters are each smaller than a diameter at a center of said coil such that said tapered portions of said conductive rods are tapered inwardly.

51. The coil claimed in claim 47 wherein said coil is a birdcage coil.