US5177442A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Transverse gradient coils for imaging the head
Assignee: General Electric Co
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Filing: 1991-07-01
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Granted: 1993-01-05
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Expires: 2011-07-01
Abstract
Abstract Apparatus for producing a magnetic field gradient for magnetic resonant imaging of the head of a subject employs two fingerprint coils disposed apart from each other, creating a generally cylindrical cavity in which subject's head is placed. A power supply provides current through the two fingerprint coils. The fingerprint coils are comprised of concentric current-carrying paths with each path being elongated along the length of the cylindrical cavity on only one end. The shape and geometry of the fingerprint coils create a magnetic field gradient that has high linearity inside the cavity, and monotonically decreases outside the cavity, thereby minimizing artifacts introduced by the body of the subject.
Inventors
- 👤 Peter B. Roemer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 22:57
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/28; G01R33/38; G01R33/385
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
163 words
A means for providing a magnetic field gradient for creating medical images of a subject's head while minimizing interference from remaining portions of said subject comprising: at least two current-carrying fingerprint coils, each comprised of a plurality of concentric turns, positioned apart from each other to create a cavity, and positioned such that lines normal to a center of each fingerprint coil would pass through the cavity, each turn comprising: a) a current return lobe enclosing a side of a first end of the cavity, and b) an imaging lobe enclosing a side of a second end of the cavity into which said subject's head is placed and the imaging lobe extending along a z axis that passes between the fingerprint coils through the center of the cavity, said lobes being situated for creating, when energized, a magnetic field having an area of high linearity and homogeneity over said subject's head, the magnetic field decreasing monotonically over said remaining portions of said subject.
Claim 2
Dependent Claim
163 words
A means for providing a magnetic field gradient for creating medical images of a subject's head while minimizing interference from remaining portions of said subject comprising: at least two current-carrying fingerprint coils, each comprised of a plurality of concentric turns, positioned apart from each other to create a cavity, and positioned such that lines normal to a center of each fingerprint coil would pass through the cavity, each turn comprising: a) a current return lobe enclosing a side of a first end of the cavity, and b) an imaging lobe enclosing a side of a second end of the cavity into which said subject's head is placed and the imaging lobe extending along a z axis that passes between the fingerprint coils through the center of the cavity, said lobes being situated for creating, when energized, a magnetic field having an area of high linearity and homogeneity over said subject's head, the magnetic field decreasing monotonically over said remaining portions of said subject.
Claim 3
Dependent Claim
30 words
The means for providing a magnetic field gradient of claim 1 wherein the imaging lobe is substantially larger than the current return lobe for providing an extended area for imaging.
Claim 4
Dependent Claim
28 words
The means for providing a magnetic field gradient of claim 2 wherein the current return lobe is shaped to create a monotonically decreasing magnetic field outside the cavity.
Claim 5
Dependent Claim
18 words
The means for providing a magnetic field gradient of claim 1 wherein the cavity is generally cylindrically shaped.
Claim 6
Dependent Claim
101 words
The means for providing a magnetic field gradient of claim 1 wherein the lines of current flow substantially follow stream lines described by ##EQU18## where θ is an angle measured around the z axis starting from the x axis, z 1 is the length of a current return lobe of the fingerprint coil along the z axis, z 2 is a length of a imaging lobe of the fingerprint coil along the z axis, which is orthogonal to the x axis, N is the number of turns on each fingerprint coil, and I is the current flowing in the fingerprint coils.
Claim 7
Dependent Claim
105 words
The means for providing a magnetic field gradient of claim 1 wherein the lines of current flow substantially follow lines described by: ##EQU19## θ is an angle measured around the z axis starting from the x axis, z 1 is the length of a current return lobe of the fingerprint coil along the z axis, which is orthogonal to the x axis, z 2 is a length of a imaging lobe of the fingerprint coil along the z axis, N is the number of turns on each fingerprint coil, I is the current flowing in the fingerprint coils, k=2πm/T, and T is the periodic interval.
Claim 8
Dependent Claim
27 words
The means for providing a magnetic field gradient of claim 4 wherein the fingerprint coils are positioned such that lines normal to each fingerprint coil is collinear.
Claim 9
Dependent Claim
23 words
The means for providing a magnetic field gradient of claim 5 wherein each turn comprises a plurality of substantially parallel closed conductive paths.
Claim 10
Dependent Claim
23 words
The means for providing a magnetic field gradient of claim 6 wherein each turn comprises a set of substantially parallel closed conductive paths.
Claim 11
Dependent Claim
20 words
The means for providing a magnetic field gradient of claim 5 wherein each turn comprises a substantially spiral conductive path.
Claim 12
Dependent Claim
20 words
The means for providing a magnetic field gradient of claim 6 wherein each turn comprises a substantially spiral conductive path.
Claim 13
Dependent Claim
24 words
The means for providing a magnetic field gradient as recited in claim 1 including a power supply for driving a current through the turns.
Claim 14
Dependent Claim
24 words
The means for providing a magnetic field gradient as recited in claim 5 including a power supply for driving a current through the turns.
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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) | 1996-01-05 | 1996-07-06 | 1997-01-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-01-05 | 2000-07-06 | 2001-01-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-01-05 | 2004-07-06 | 2005-01-05 | $7700.00 | Window Closed / Lapsed |