Nuclear magnetic resonance apparatus and methods of use and facilities for incorporating the same

• US 6,023,165 A
• Filed: 12/18/1992
• Issued: 02/08/2000
• Est. Priority Date: 09/28/1992
• Status: Expired due to Term

• Current Assignee: Fonar Corporation
• Original Assignee: Fonar Corporation
• Inventors: Hsieh, Hank, Damadian, Raymond V., Danby, Gordon T., Morrone, Terry, Jackson, John W., Damadian, Timothy
• Primary Examiner(s): ARANA, LOUIS M
• Application Number:
  US07/993,072
• Time in Patent Office: 2,608 Days
• Field of Search: 324/318, 324/319, 324/320, 324/322, 324/300, 324/307, 324/309, 335/296, 335/297, 335/298, 128/653.5
• US Class Current: 324/318
• CPC Class Codes: A61B 18/00 Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body eye surgery A61F9/007; ear surgery A61F11/00
• CPC Class Codes: A61B 2017/22038 with a guide wire
• CPC Class Codes: A61B 2090/374 NMR or MRI
• CPC Class Codes: A61B 34/10 Computer-aided planning, simulation or modelling of surgical operations
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 90/36 Image-producing devices or illumination devices not otherwise provided for
• CPC Class Codes: G01R 33/3806 Open magnet assemblies for improved access to the sample, e.g. C-type or U-type magnets

Abstract

NMR apparatus for achieving construction of improved patient access. Faciliites and methods for mobile and fixed site NMR scanning.

Claims

1. Magnetic resonance imaging apparatus comprising:

a pair of opposed ferromagnetic poles disposed facing each other and defining therebetween a patient-receiving gap for receiving a patient to be studied by magnetic resonance;

a ferromagnetic yoke and establishing a magnetic flux return path for magnetic flux which passes from one pole to the other through the patient-receiving gap;

said ferromagnetic yoke comprising upper and lower pole supports comprised of ferromagnetic material supporting said pair of poles one above the other, said poles projecting toward one another from said pole supports, and at least three columns comprised of ferromagnetic material disposed between said pole supports for supporting said upper pole support above said lower pole support with said pair of poles spaced one above the other; and

means for generating magnetic flux flowing through said projecting poles and flowing from one to the other of said poles through the patient-receiving gap and having a strength sufficient to develop a flux in excess of 3000 gauss at the center of the patient-receiving gap.

20. Apparatus according to any of claims 1, 2, 3, 5, 8, 11 or 15 further comprising means for suppressing the generation of eddy currents in said pole surfaces by time-varying magnetic fields developed during magnetic resonance studies carried out with said magnet.

21. Apparatus according to claim 20, further comprising conductors disposed overlying each of said pole surfaces and configured to develop gradient magnetic fields within the gap in response to current flowing through said conductors, said means for suppressing the generation of eddy currents comprising said conductors being spaced a sufficient distance from the respective pole surfaces which they overlie to reduce the strength of generated eddy currents to less than a predetermined value.

22. Apparatus according to claim 20, wherein said means for suppressing the generation of eddy currents is comprised of a layer of eddy current-suppressing material.

23. Apparatus according to claim 20, wherein said means for suppressing the generation of eddy currents is comprised of respective layers of high magnetic permeability material overlying said pole surfaces, wherein the value of magnetic permeability is sufficiently high to suppress eddycurrents relative to eddy currents which would be developed in said pole surfaces in the absence of said layers of high permeability material.

24. Apparatus according to any of claims 1, 2, 3, 5, 8, 11 or 15 further comprising a shim bar projecting from each of said pole surfaces and conductors disposed overlying each of said pole surfaces and configured to develop gradient magnetic fields within the gap in response to current flowing through said conductors, said conductors extending over said shim bars.

25. Apparatus according to any of claims 1, 2, 3, 5, 8, 11 or 15 further comprising first conductors disposed overlying each of said pole surfaces and configured to develop time varying gradient magnetic fields within the gap in response to current flowing through said first conductors, and second conductors disposed between said first conductors and said pole surfaces and connected for receiving current to develop magnetic fields proximate said pole surfaces for at least partially canceling the gradient magnetic fields in regions proximate said pole surfaces to suppress eddy currents in said pole surfaces generated by time-varying gradient magnetic fields.

26. Apparatus according to any of claims 1, 2, 3, 8, 11 or 15, wherein said means for generating magnetic flux is comprised of permanent magnet material.

27. Apparatus according to claim 26, wherein said permanent magnet material is disposed underlying said pole surfaces.

28. Apparatus according to any of claims 1, 2, 3, 8, 11 or 15 wherein said means for generating magnetic flux is comprised of at least one resistive electromagnet winding encircling a portion of said ferromagnetic flux path.

29. Apparatus according to claim 28, wherein said at least one resistive electromagnet winding is comprised of stacked layers of conductor turns defining an electromagnet, a cooling plate intermediate to said stacked layers of conductor turns, and external cooling plates for removing heat from said resistive electromagnet winding.

30. Apparatus according to claim 28, wherein said cooling plates include internal fluid conduits for providing a path for cooling fluid to effectuate heat dissipation by said cooling plates.

31. Apparatus according to claim 28, wherein said at least one resistive electromagnet winding is comprised of a coiled conductor having an internal fluid conduit extending along its length for providing a path for cooling of said winding.

32. Apparatus according to any of claims 1, 2, 3, 8, 11 or 15 wherein said means for generating magnetic flux is comprised of a superconductive magnet.

33. Apparatus according to claim 32 wherein said superconductive magnet comprises a multiplicity of superconductive magnets wherein each superconductive magnet underlies a respective one of said pole surfaces of the magnet.

34. Apparatus according to any of claims 1, 2, 3, 11 or 15 wherein said ferromagnetic material has magnetic permeability values equal to or exceeding those of grade 1006 steel.

35. Apparatus according to any of claims 1, 2, 5, 8, 11 or 15 wherein said pole surfaces define a gap distance therebetween equal to or greater than twenty-two inches.

36. Apparatus according to any of claims 1, 2, 3, 5, 8, 11 or 15 wherein said yoke is dimensioned to define a gap distance between said pole surfaces greater than the shoulder-to-shoulder dimension of a patient to be studied by magnetic resonance.

37. Apparatus according to any of claims 1, 2, 3, 5, 8, 11 or 15 wherein said means for generating magnetic flux has sufficient strength to develop magnetic flux in excess of 6000 gauss at the center of the patient-receiving gap.

38. Apparatus according to any of claims 1, 2, 3, 5, 8, 11 or 15 wherein said means for generating magnetic flux has sufficient strength to develop magnetic flux in excess of 4500 gauss at the center of the patient-receiving gap.

40. Apparatus according to any one of claims 1, 2, 3, 5, 8 or 12 wherein the distance between said upper and lower pole supports is at least 60 inches.

41. Apparatus according to any one of claims 1, 2, 3, 5, 8 or 12 wherein said pole surfaces define a polar axis extending therebetween and wherein the distance from the center of the patient-receiving gap to one of said columns, measured in a plane orthogonal to the polar axis, is at least 45 inches.

2. Magnetic resonance imaging apparatus comprising:

a pair of poles projecting towards one another and defining opposed ferromagnetic pole surfaces disposed facing each other and defining therebetween a patient-receiving gap for receiving a patient to be studied by magnetic resonance;

a ferromagnetic yoke for supporting said pair of poles and establishing a magnetic flux return path for magnetic flux which passes through said poles and which passes from one pole surface to the other through the patient-receiving gap, said yoke defining at least two different non-collinear directions of patient entry into and egress from the patient-receiving gap; and

means for generating magnetic flux through said projecting poles and flowing from one to the other of said pole surfaces through the patient-receiving gap and having a strength sufficient to develop a flux in excess of 3000 gauss at the center of the patient-receiving gap.

3. Magnetic resonance imaging apparatus comprising:

a pair of poles projecting towards one another and defining opposed ferromagnetic pole surfaces facing each other, spaced a distance equal to or greater than twenty-two inches, and defining therebetween a patient-receiving gap for receiving a patient to be studied by magnetic resonance;

a ferromagnetic yoke for supporting said pair of poles, and establishing a magnetic flux return path for magnetic flux which passes through said poles and which passes from one pole surface to the other through the patient-receiving gap; and

means for generating magnetic flux flowing through said projecting poles and flowing from one to the other of said pole surfaces through the patient-receiving gap and having a strength sufficient to develop a flux in excess of 3000 gauss at the center of the patient-receiving gap.

4. Apparatus according to claim 3, wherein said ferromagnetic flux path is comprised of

upper and lower pole supports comprised of ferromagnetic material for supporting said pair of poles one above the other;

and

at least three columns comprised of ferromagnetic material disposed between said pole supports for supporting said upper pole support above said lower pole support with said pair of poles spaced one above the other.

5. Magnetic resonance imaging apparatus comprising:

(a) a ferromagnetic yoke including a pair of ferromagnetic pole supports spaced apart from one another, a pair of poles projecting towards one another from said pole supports, said poles defining a pair of pole surfaces facing towards one another with a patient-receiving gap therebetween, and one or more ferromagnetic elements extending between said pole supports, said yoke defining at least two different non-collinear directions of patient entry into and egress from the patient-receiving gap; and

(b) resistive electromagnet windings encircling said poles between said pole supports and said pole surfaces for generating magnetic flux flowing in said patient-receiving gap, said windings being operative to develop a flux in excess of 3000 gauss at the center of the patient-receiving gap.

6. Apparatus as claimed in claim 5 wherein said one or more ferromagnetic elements includes at least three columns disposed at spaced apart locations around said patient-receiving gap.

7. Magnetic resonance imaging apparatus comprising:

means for defining a ferromagnetic flux path for magnetic flux and having a patient-receiving gap therein for receiving a patient to be studied by magnetic resonance, and said means for defining a ferromagnetic flux path comprising a ferromagnetic material having magnetic permeability values equal to or exceeding those of grade 1006 steel and having a pair of facing and spaced pole surfaces for defining the patient-receiving gap therebetween; and

magnetic flux generating means for generating magnetic flux flowing from one to the other of said pole surfaces through the patient-receiving gap.

8. Apparatus according to claim 7, wherein said means for defining a ferromagnetic flux path includes a pair of ferromagnetic poles comprised of a ferromagnetic material having magnetic permeability values equal to or exceeding those of grade 1006 steel each said pole defining one said pole surface, said pair of ferromagnetic poles projecting toward one another and being positioned with their respective pole surfaces facing each other and spaced to define the patient-receiving gap therebetween.

9. Apparatus as claimed in claim 8 wherein said means for defining a ferromagnetic flux path includes upper and lower pole supports comprised of a ferromagnetic material having magnetic permeability values equal to or exceeding those of grade 1006 steel for supporting said pair of poles one above the other.

10. Apparatus as claimed in claim 9 wherein said means for defining a ferromagnetic flux path includes at least three columns comprised of a ferromagnetic material having magnetic permeability values equal to or exceeding those of grade 1006 steel disposed between said pole supports for supporting said upper pole support above said lower pole support with said pair of poles spaced one above the other.

11. Magnetic resonance imaging apparatus comprising:

a magnet comprising a pair of opposed ferromagnetic pole surfaces disposed facing each other and defining therebetween a patient-receiving gap for receiving a patient to be studied by magnetic resonance, means comprised of ferromagnetic material for providing a magnetic flux return circuit for magnetic flux which passes from one pole surface to the other through the patient-receiving gap, and means for generating magnetic flux flowing from one to the other of said pole surfaces through the patient-receiving gap; and

a plurality of walls together comprising a room, wherein said pole surfaces are within said room, said magnetic flux return circuit extends to the exterior of said room, and magnetic resonance studies are carried out with said magnet on a patient within said room.

12. Apparatus according to claim 11, wherein said means for defining a ferromagnetic flux return circuit is comprised of

upper and lower pole supports comprised of ferromagnetic material for supporting said pair of pole surfaces one above the other;

and

at least three columns comprised of ferromagnetic material disposed between said pole supports for supporting said upper pole support above said lower pole support with said pair of pole surfaces spaced one above the other.

13. A magnet as claimed in claim 11 wherein said flux return circuit includes a pair of pole supports disposed outside of said room and a pair of ferromagnetic poles projecting into said room from said pole supports, said poles defining said pole surfaces.

14. A magnet as claimed in claim 13 wherein said room is large enough for people to stand within it.

39. Apparatus according to any of claims 8, 11 or 15 wherein said means for generating magnetic flux has sufficient strength to develop magnetic flux in excess of 3000 gauss at the center of the patient-receiving gap.

15. Magnetic resonance scanning apparatus comprising:

a magnet comprising a pair of opposed ferromagnetic pole surfaces disposed facing each other and defining therebetween a patient-receiving gap for receiving a patient to be studied by magnetic resonance, means comprised of ferromagnetic material for providing a magnetic flux return circuit for magnetic flux which passes from one pole surface to the other through the patient-receiving gap, and means for generating magnetic flux flowing from one to the other of said pole surfaces through the patient-receiving gap; and

a room having a floor, wherein said pole surfaces are within said room and above said floor, said magnetic flux return circuit extends to the exterior of said room, and magnetic resonance studies are carried out with said magnet on a patient within said room.

16. Apparatus as claimed in claim 15 wherein said magnetic flux return circuit extends beneath said floor.

17. A magnet as claimed in claim 16 wherein said flux return circuit includes a upper and lower ferromagnetic pole supports disposed one above the other, columns supporting said upper pole support above said lower pole support, and poles projecting towards one another from said pole supports, said lower pole support being disposed beneath the floor of said room, one of said poles projecting upwardly from said lower pole support into the room.

18. A magnet as claimed in claim 17 wherein said room is large enough for people to stand within it.

19. A magnet as claimed in claim 17 further comprising a false floor, false walls and false ceiling concealing said pole supports and columns from view from within said room.