Permanent magnet for nuclear magnetic resonance imaging equipment

• US 5,332,971 A
• Filed: 03/26/1993
• Issued: 07/26/1994
• Est. Priority Date: 07/30/1990
• Status: Expired due to Fees

• Current Assignee: Universite Joseph Fourier
• Original Assignee: Universite Joseph Fourier
• Inventors: Aubert, Guy
• Primary Examiner(s): Tokar, Michael J.
• Assistant Examiner(s): MAH, RAYMOND
• Application Number:
  US07/961,699
• Time in Patent Office: 487 Days
• Field of Search: 324/319, 324/318, 324/322, 324/300, 324/320, 335/306, 335/322
• US Class Current: 324/319
• CPC Class Codes: G01R 33/383 using permanent magnets
• CPC Class Codes: H01F 7/0278 for generating uniform fields, focusing, deflecting electrically charged particles for magnetic separation by Lorentz force B03C1/023; specially adapted for NMR applications G01R33/383

Abstract

A permanent magnet for nuclear magnetic resonance imaging that provides an intense and highly homogeneous magnetic magnetic field is disclosed. The magnet is made up of a set of rings having two sub-sets of rings of permanently magnetized polygonal blocks, wherein the rings of a sub-set of rings are substantially concentric. In addition, the rings of the two sub-sets are complementary in terms of magnetization. Each ring of a sub-set is separated from its complementary ring by a space that is substantially the same for all pairs of complementary rings. The rings have a regular polygonal structure and are made up of blocks that also have regular polygonal shapes.

Claims

1. A permanent magnet for nuclear magnetic resonance imaging equipment, comprising:

a set of rings comprising two sub-sets of rings of magnetized blocks for producing an intense and homogeneous magnetic field in a region of space, the rings within each sub-set being substantially concentric the rings in each subset being complementary in terms of magnetization, each ring of a sub-set being separated from its complementary ring in a facing sub-set by a height of this region, said height being substantially the same for all pairs of complementary rings, wherein the rings have a regular polygonal structure and are comprised of blocks, the number of blocks in each ring being substantially greater than or equal to four times the number of rings in a subset of rings.

2. A magnet according to claim 1, wherein internal rings of each of the sub-sets of rings are provided with blocks in which the orientation of the magnetization is transverse with respect to the planes of the internal rings.

3. A Magnet according to claim 1, wherein internal rings of each of the sub-sets of rings are each provided with a central hole.

4. A magnet according to claim 1, producing a homogeneous magnetic field, wherein an analytical expression of said homogeneous magnetic field comprises no term of an order equal to or smaller than 2p₀, the rings having a regular polygonal structure formed by sets of blocks comprising at least 2(p₀ +1) blocks.

7. A magnet according to claim 1, wherein magnetic fields produced by the blocks of a ring are parallel to the direction of magnetic fields produced by directly facing blocks of its complementary ring.

5. A permanent magnet for nuclear magnetic resonance imaging equipment, comprising:

a set of rings comprising two sub-sets of rings of permanently magnetized blocks for producing an intense and homogeneous magnetic field in a region of space, the rings being complementary in terms of magnetization, the rings within each sub-set of rings being substantially concentric, each ring of a sub-set of rings being separated from its complementary ring in a facing sub-set by a height of this region, said height being substantially the same for all pairs of complementary rings, rings of successively greater diameter in each of the sub-sets of rings being provided with blocks in which the orientation of magnetization is radial with respect to the rings.

6. A magnet according to claim 5, wherein magnetic fields produced by the blocks of a ring are parallel to the direction of magnetic fields produced by directly facing blocks of its complementary ring.

8. A magnet according to claim 5, wherein internal rings of each of the sub-sets of rings are provided with blocks in which the orientation of the magnetization is transverse with respect to the planes of the internal rings.

9. A magnet according to claim 5, wherein internal rings of each of the sub-sets of rings are each provided with a central hole.

10. A magnet according to claim 5, producing a homogeneous magnetic field, wherein an analytical expression of said homogeneous magnetic field comprises no term of an order equal to or smaller than 2p₀, the rings having a regular polygonal structure formed by sets of blocks comprising at least 2(p₀ +1) blocks.