US4595899A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic structure for NMR applications and the like
Assignee: Leland Stanford Junior University
•
Filing: 1985-03-18
•
Granted: 1986-06-17
•
Expires: 2005-03-18
Abstract
Abstract Magnetic shielding of a magnet such as a first set of superconducting coils as used in nuclear magnetic resonance (NMR) applications includes a second set of coils around and spaced from the first set of coils. The magnetic flux of the second set of coils opposes and offsets the magnetic flux of the first set of coils in the region outside of the second set of coils but is less than the magnetic flux of the first set of coils in the region within the first set of coils. The uniformity of the magnetic flux within the first set of coils is not adversely affected by the magnetic flux produced by the second set of coils. In a preferred embodiment the coils of the first set are independently energized to establish a uniform field within the coils having suppressed lower order derivatives of flux with respect to position within the uniform field. The external field of the first set of coils comprises a dipole which is offset by the field of the second set of coils. Higher order multipoles beyond the dipole are also suppressed by the geometries of the two sets of coils.
Inventors
- 👤 Todd I. Smith
- 👤 Michael S. McAshan
- 👤 William M. Fairbank
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 05:50
CPC Classifications
H; H01; H01F; H01F6/00; G; G01; G01R; G01R33/00; G01R33/20; G01R33/28; G01R33/38; G01R33/385; G01R33/42; G01R33/421; G01R33/4215; Y; Y10; Y10S; Y10S505/00; Y10S505/825; Y10S505/872
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
92 words
A magnetic structure useful in NMR applications comprising a first set of coils provided about a volume and independently energized to establish a field with suppressed lower order derivatives of flux through said volume and a dipole with higher order magnetic moments outside of said first set of coils, and a second set of coils provided about the first set of coils and independently energized for producing a magnetic field which opposes said dipole of said first set of coils while not substantially affecting the uniformity of said field through said volume.
Claim 2
Dependent Claim
92 words
A magnetic structure useful in NMR applications comprising a first set of coils provided about a volume and independently energized to establish a field with suppressed lower order derivatives of flux through said volume and a dipole with higher order magnetic moments outside of said first set of coils, and a second set of coils provided about the first set of coils and independently energized for producing a magnetic field which opposes said dipole of said first set of coils while not substantially affecting the uniformity of said field through said volume.
Claim 3
Dependent Claim
53 words
The magnetic structure as defined by claim 1 wherein said first and second sets of coils are configured and energized to suppress lower orders of derivatives of flux within said first and second sets of coils and to suppress corresponding multipole moments of the magnetic flux outside of said second set of coils.
Claim 4
Dependent Claim
17 words
The magnetic structure as defined by claim 1 wherein said structure includes openings for receiving a patient.
Claim 5
Dependent Claim
23 words
The magnetic structure as defined by claim 2 wherein said first and second sets of coils suppress multipole moments outside of said structure.
Claim 6
Dependent Claim
26 words
The magnetic structure as defined by claim 2 wherein said first set of coils and said second set of coils are arranged on generally spheroidal surfaces.
Claim 7
Dependent Claim
21 words
The magnetic structure as defined by claim 5 and further including a ferromagnetic shield provided about said second set of coils.
Claim 8
Dependent Claim
23 words
The magnetic structure as defined by claim 1 wherein said first set of coils and said second set of coils comprise superconducting coils.
Claim 9
Dependent Claim
19 words
The magnetic structure as defined by claim 1 wherein said magnetic field through said volume includes a non-uniform component.
Claim 10
Dependent Claim
141 words
A magnetic structure for NMR imaging comprising a first set of coils arranged to define a first spheroidal surface having two opposing openings for receiving a patient for imaging, each coil of said first set of coils being independently energizable to establish a uniform field within said first spheroidal surface and a dipole outside of said first spheroidal surface, and a second set of coils arranged to define a second spheroidal surface having two opposing openings for receiving a patient for imaging, said second spheroidal surface being concentric with and outside of said first spheroidal surface, each coil of said second set of coils being independently energizable to establish a field outside of said second spheroidal surface which offsets said dipole of said first set of coils while not significantly affecting the uniformity of said field within said first spheroidal surface.
Claim 11
Dependent Claim
141 words
A magnetic structure for NMR imaging comprising a first set of coils arranged to define a first spheroidal surface having two opposing openings for receiving a patient for imaging, each coil of said first set of coils being independently energizable to establish a uniform field within said first spheroidal surface and a dipole outside of said first spheroidal surface, and a second set of coils arranged to define a second spheroidal surface having two opposing openings for receiving a patient for imaging, said second spheroidal surface being concentric with and outside of said first spheroidal surface, each coil of said second set of coils being independently energizable to establish a field outside of said second spheroidal surface which offsets said dipole of said first set of coils while not significantly affecting the uniformity of said field within said first spheroidal surface.
Claim 12
Dependent Claim
93 words
A magnetic structure useful in NMR applications comprising a first set of coils provided about a first spheroidal surface, a second set of coils provided about a second spheroidal surface, said second spheroidal surface being generally concentric with and spaced around said first spheroidal surface, said first set of coils and said second set of coils being cooperatively and independently energizable to produce a magnetic field within said first spheroidal surface of a desired geometry and to produce at least one opposing component of a magnetic field outside of said second spheroidal surface.
Claim 13
Dependent Claim
93 words
A magnetic structure useful in NMR applications comprising a first set of coils provided about a first spheroidal surface, a second set of coils provided about a second spheroidal surface, said second spheroidal surface being generally concentric with and spaced around said first spheroidal surface, said first set of coils and said second set of coils being cooperatively and independently energizable to produce a magnetic field within said first spheroidal surface of a desired geometry and to produce at least one opposing component of a magnetic field outside of said second spheroidal surface.
Claim 14
Dependent Claim
50 words
The magnetic structure as defined by claim 10 wherein said desired geometry within said first spheroidal surface is a uniform field having suppressed orders of derivatives of flux and simultaneously suppressed multipole moments outside of said second spheroidal surface, said suppressed multipole moments corresponding to said suppressed orders of derivatives.
Claim 15
Dependent Claim
29 words
The magnetic structure as defined by claim 11 wherein said first set of coils and said second set of coils produce opposing dipoles outside of said second spheroidal surface.
Claim 16
Independent Claim
117 words
A method of effectively shielding a magnetic structure for use in NMR imaging comprising the steps of providing a first set of coils which define a first spheroidal surface, energizing each of said first set of coils to establish a uniform magnetic field within said first spheroidal surface and a dipole outside of said first spheroidal surface, providing a second set of coils which define a second spheroidal surface concentric with and outside of said first spheroidal surface, and energizing each of said second set of coils to establish a magnetic field outside of said second spheroidal surface which offsets said dipole while not significantly affecting the uniformity of said magnetic field within said first spheroidal surface.
Claim 17
Independent Claim
117 words
A method of effectively shielding a magnetic structure for use in NMR imaging comprising the steps of providing a first set of coils which define a first spheroidal surface, energizing each of said first set of coils to establish a uniform magnetic field within said first spheroidal surface and a dipole outside of said first spheroidal surface, providing a second set of coils which define a second spheroidal surface concentric with and outside of said first spheroidal surface, and energizing each of said second set of coils to establish a magnetic field outside of said second spheroidal surface which offsets said dipole while not significantly affecting the uniformity of said magnetic field within said first spheroidal surface.
Claim 18
Dependent Claim
48 words
The method as defined by claim 13 wherein each coil of said first set of coils is independently energized to suppress lower order derivatives of flux with respect to position within said uniform magnetic field and simultaneously suppress lower order magnetic moments outside of said first spheroidal surface.
Claim 19
Independent Claim
112 words
A method of generating a magnetic field of a desired configuration within a volume and simultaneously producing a magnetic field of reduced magnitude outside of said volume, said method comprising the steps of providing a first set of coils on a first spheroidal surface around said volume, providing a second set of coils on a second spheroidal surface generally concentric with said first spheroidal surface and spaced around said first spheroidal surface, independently energizing said first set of coils and said second set of coils to produce said magnetic field of desired configuration within said volume and to produce at least one opposing component of a magnetic field outside of said volume.
Claim 20
Independent Claim
112 words
A method of generating a magnetic field of a desired configuration within a volume and simultaneously producing a magnetic field of reduced magnitude outside of said volume, said method comprising the steps of providing a first set of coils on a first spheroidal surface around said volume, providing a second set of coils on a second spheroidal surface generally concentric with said first spheroidal surface and spaced around said first spheroidal surface, independently energizing said first set of coils and said second set of coils to produce said magnetic field of desired configuration within said volume and to produce at least one opposing component of a magnetic field outside of said volume.
Claim 21
Dependent Claim
49 words
The method as defined by claim 15 wherein said desired geometry within said first spheroidal surface is a uniform field having suppressed orders of derivatives of flux and simultaneously suppressed multipole moments outside of said second spheroidal surface, said suppressed multipole moments corresponding to said suppressed orders of derivatives.
References Cited (Backward Citations)
US2179257A
Cited
US2265041A
Cited
US3515979A
Cited
US3493904A
Cited
US3466499A
Cited
US3671902A
Cited
US3768054A
Cited
US4231008A
Cited
US4320342A
Cited
US4339718A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-06-16 | 1989-12-16 | 1990-06-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-06-16 | 1993-12-16 | 1994-06-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-06-16 | 1997-12-16 | 1998-06-17 | $7700.00 | Window Closed / Lapsed |