US5359310A
Expired / Lapsed
US
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Ultrashort cylindrical shielded electromagnet for magnetic resonance imaging
Assignee: Houston Advanced Research Center
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Filing: 1992-04-15
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Granted: 1994-10-25
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Expires: 2012-04-15
Abstract
Abstract A superconducting magnet suitable for use in magnetic resonance imaging applications is disclosed. A plurality of driving coils are located around a cylindrical bore, for generating an axial magnetic field therein. At the ends of the magnet, within the same cryostat as the driving coils, first and second shielding coils are located, each carrying a current of opposite polarity relative to the driving coils. The location, size, and current in the coils are determined by a methodology in which the error between the desired field and the simulated field is minimized at target locations within the bore and outside of the bore. A flux return is disposed in the gap between the first and second shielding coils, so that the shielding coils inject return magnetic flux into the flux return. The flux return may be of iron, or may consist of a superconducting coil. The resulting magnet has relatively low superconductor cost as well as relatively low weight, due to the efficient use of both superconductor and iron.
Inventors
- 👤 Sergio Pissanetzky
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 23:15
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/28; G01R33/38; G01R33/381; G01R33/3815; G01R33/3806; G01R33/387; G01R33/3875; G01R33/42; G01R33/421
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
202 words
A superconducting magnet, comprising: a plurality of driving coils surrounding a cylindrical bore, each comprises of superconducting cable, for conducting current in a first direction to generate magnetic flux in said bore having substantially an axial orientation therein, said plurality of coils disposed at varying axial distance surrounding said bore; first and second shielding coils, each comprised of superconducting cable, each having a radius greater than that of said driving coil, and disposed at first and second ends of said electromagnet, respectively, said first and second shielding coils conducting current in a second direction opposing said first direction; and a flux return, comprising ferromagnetic material and having an innermost radius greater than an outermost radius of said driving coils so as to radially surround at least one of said plurality of driving coils, said flux return axially disposed between said first and second shielding coils, for providing a return path for magnetic flux generated by said driving coil; wherein the axial length of said flux return is less than the distance between axially outermost ones of said plurality of driving coils, so that magnetic flux is injected into the axial ends of said flux return by said first and second shielding coils.
Claim 2
Dependent Claim
202 words
A superconducting magnet, comprising: a plurality of driving coils surrounding a cylindrical bore, each comprises of superconducting cable, for conducting current in a first direction to generate magnetic flux in said bore having substantially an axial orientation therein, said plurality of coils disposed at varying axial distance surrounding said bore; first and second shielding coils, each comprised of superconducting cable, each having a radius greater than that of said driving coil, and disposed at first and second ends of said electromagnet, respectively, said first and second shielding coils conducting current in a second direction opposing said first direction; and a flux return, comprising ferromagnetic material and having an innermost radius greater than an outermost radius of said driving coils so as to radially surround at least one of said plurality of driving coils, said flux return axially disposed between said first and second shielding coils, for providing a return path for magnetic flux generated by said driving coil; wherein the axial length of said flux return is less than the distance between axially outermost ones of said plurality of driving coils, so that magnetic flux is injected into the axial ends of said flux return by said first and second shielding coils.
Claim 3
Dependent Claim
28 words
The magnet of claim 1, wherein first and second ones of said plurality of driving coils are disposed radially inwardly from said first and second shielding coils, respectively.
Claim 4
Dependent Claim
33 words
The magnet of claim 2, wherein said first and second ones of said plurality of driving coils each conduct a higher magnitude of current than the remainder of said plurality of driving coils.
Claim 5
Dependent Claim
21 words
The magnet of claim 1, wherein at least one of said plurality of driving coils has a cross-section of irregular shape.
Claim 6
Dependent Claim
19 words
The magnet of claim 1, wherein said first and second shielding coils each have a cross-section of irregular shape.
Claim 7
Dependent Claim
28 words
The magnet of claim 1, further comprising: a cryostat, surrounding said plurality of driving coils and said first and second shielding coils, for maintaining a cryogenic temperature therewithin.
Claim 8
Dependent Claim
15 words
The magnet of claim 6, wherein said flux return is disposed outside of said cryostat.
Claim 9
Dependent Claim
163 words
A superconducting magnet comprising: a driving coil surrounding a cylindrical bore, comprised of superconducting cable, for conducting current in a first direction to generate magnetic flux in said bore having substantially an axial orientation therein; first and second shielding coils, each comprised of superconducting cable, each having a radius greater than that of said driving coil, and disposed at first and second ends of said electromagnet, respectively, said first and second shielding coils conducting current in a second direction opposing said first direction; and a flux return surrounding said driving coil and disposed between said first and second shielding coils, for providing a return path for magnetic flux generated by said driving coil, and injected thereinto by said first and second shielding coils, said flux return comprising a plurality of plates of ferromagnetic material arranged in segments around said driving coil, each of said segments comprising a group of said plurality of plates, disposed adjacent one another, and arranged according to increasing width.
Claim 10
Dependent Claim
163 words
A superconducting magnet comprising: a driving coil surrounding a cylindrical bore, comprised of superconducting cable, for conducting current in a first direction to generate magnetic flux in said bore having substantially an axial orientation therein; first and second shielding coils, each comprised of superconducting cable, each having a radius greater than that of said driving coil, and disposed at first and second ends of said electromagnet, respectively, said first and second shielding coils conducting current in a second direction opposing said first direction; and a flux return surrounding said driving coil and disposed between said first and second shielding coils, for providing a return path for magnetic flux generated by said driving coil, and injected thereinto by said first and second shielding coils, said flux return comprising a plurality of plates of ferromagnetic material arranged in segments around said driving coil, each of said segments comprising a group of said plurality of plates, disposed adjacent one another, and arranged according to increasing width.
Claim 11
Dependent Claim
34 words
The magnet of claim 8, wherein said flux return further comprises: first and second ferromagnetic rings, disposed at first and second ends of said flux return, respectively, for supporting said plurality of plates thereupon.
Claim 12
Dependent Claim
37 words
The magnet of claim 9, wherein said flux return further comprises: a plurality of inner plates, each disposed between said first and second rings, and each corresponding to one of said segments of said plurality of plates.
Claim 13
Independent Claim
176 words
An apparatus for generating a high magnetic field suitable for nuclear magnetic resonance, comprising: a superconducting driving solenoid comprising a plurality of driving coils, and having an inner and an outer radius so as to define a cylindrical bore, each of said driving coils conducting current of a first polarity to generate a magnetic field in said bore; a flux return, comprising ferromagnetic material and having an inner radius greater than the outer radius of said driving solenoid so as to surround at least one of said plurality of driving coils in said driving solenoid, and having an axial length less than the distance between axially outermost ones of said plurality of driving coils; and first and second superconducting shielding coils, disposed at first and second axial ends of said flux return, each of said first and second shielding coils surrounding said bore and conducting current of a second polarity opposing said first polarity to direct the path of return magnetic flux into and out of the first and second ends of said flux return, respectively.
Claim 14
Independent Claim
176 words
An apparatus for generating a high magnetic field suitable for nuclear magnetic resonance, comprising: a superconducting driving solenoid comprising a plurality of driving coils, and having an inner and an outer radius so as to define a cylindrical bore, each of said driving coils conducting current of a first polarity to generate a magnetic field in said bore; a flux return, comprising ferromagnetic material and having an inner radius greater than the outer radius of said driving solenoid so as to surround at least one of said plurality of driving coils in said driving solenoid, and having an axial length less than the distance between axially outermost ones of said plurality of driving coils; and first and second superconducting shielding coils, disposed at first and second axial ends of said flux return, each of said first and second shielding coils surrounding said bore and conducting current of a second polarity opposing said first polarity to direct the path of return magnetic flux into and out of the first and second ends of said flux return, respectively.
Claim 15
Dependent Claim
29 words
The apparatus of claim 11, wherein said flux return comprises a plurality of segments of ferromagnetic material, each of said segments corresponding to a cross-sectional arc of said apparatus.
Claim 16
Dependent Claim
28 words
The apparatus of claim 11, wherein first and second ones of said plurality of driving coils are disposed radially inwardly from said first and second shielding coils, respectively.
Claim 17
Dependent Claim
33 words
The apparatus of claim 13, wherein said first and second ones of said plurality of driving coils each conduct a higher magnitude of current than the remainder of said plurality of driving coils.
Claim 18
Dependent Claim
21 words
The apparatus of claim 11, wherein at least one of said plurality of driving coils has a cross-section of irregular shape.
Claim 19
Dependent Claim
38 words
The apparatus of claim 11, further comprising: a cryostat, surrounding said plurality of driving coils and said first and second shielding coils, for maintaining a cryogenic temperature therewithin; wherein said flux return is disposed outside of said cryostat.
Claim 20
Dependent Claim
19 words
The apparatus of claim 11, wherein said first and second shielding coils each have a cross-section of irregular shape.
Claim 21
Independent Claim
131 words
An apparatus for generating a high magnetic filed suitable for nuclear magnetic resonance, comprising: a superconducting driving solenoid, surrounding a cylindrical bore, for conducting current of a first polarity to generate a magnetic field in said bore; a flux return, surrounding said driving solenoid and comprising a plurality of segments of ferromagnetic material, each of said segments corresponding to a cross-sectional arc of said apparatus and comprising a plurality of plates of said ferromagnetic material arranged adjacent one another in increasing width to substantially fill the cross-section arc; and first and second superconducting shielding coils, disposed at first and second axial ends of said flux return and surrounding said bore thereat, conducting current of a second polarity opposing said first polarity, and for injecting return magnetic flux into said flux return.
Claim 22
Independent Claim
131 words
An apparatus for generating a high magnetic filed suitable for nuclear magnetic resonance, comprising: a superconducting driving solenoid, surrounding a cylindrical bore, for conducting current of a first polarity to generate a magnetic field in said bore; a flux return, surrounding said driving solenoid and comprising a plurality of segments of ferromagnetic material, each of said segments corresponding to a cross-sectional arc of said apparatus and comprising a plurality of plates of said ferromagnetic material arranged adjacent one another in increasing width to substantially fill the cross-section arc; and first and second superconducting shielding coils, disposed at first and second axial ends of said flux return and surrounding said bore thereat, conducting current of a second polarity opposing said first polarity, and for injecting return magnetic flux into said flux return.
Claim 23
Dependent Claim
55 words
The apparatus of claim 18, wherein said flux return further comprises: first and second ferromagnetic rings, disposed at first and second ends of said flux return, respectively, for supporting said plurality of plates in each of said segments thereupon; and for each of said segments, an inner plate disposed between said first and second rings.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-10-24 | 1998-04-25 | 1998-10-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-10-24 | 2002-04-25 | 2002-10-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-10-24 | 2006-04-25 | 2006-10-25 | $7700.00 | Window Closed / Lapsed |