US4649347A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for off-center field-of-view imaging using MR
Assignee: General Electric Co
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Filing: 1985-11-15
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Granted: 1987-03-10
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Expires: 2005-11-15
Abstract
Abstract Off-center field-of-view studies are achieved in MR multi-slice imaging methods by rotation of the axes along which the phase-encoding and readout magnetic field gradients are applied and offsetting the frequency of the MR receiver from the system isocenter frequency. The method is particularly useful in two-dimensional multi-slice imaging using surface coils.
Inventors
- 👤 Tzong Y. Hwang
- 👤 Nicholas F. Campagna
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 11:31
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/483; G01R33/4833; G01R33/54; G01R33/56; G01R33/5604
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
179 words
A method for imaging, using MR, a predetermined region of an object, which region is removed from the isocenter of an MR system having gradient coils for generating magnetic field gradients along the x, y and z axes of a Cartesian coordinate system, said MR system having RF means for exciting and receiving MR signals from said region, said method comprising the steps of: (a) exciting nuclear spins in said region; (b) applying a phase-encoding gradient having one of a plurality of predetermined amplitudes to phase encode spatial information into said excited nuclear spins, said phase-encoding gradient being applied along a y' axis rotated by an angle θ relative to the y axis; (c) receiving an MR signal from said excited spins in the presence of a readout magnetic field gradient applied along an X' axis which is orthogonal to said y' axis, said angle θ being greater than zero and selected such that said x' axis intersects said predetermined region; and (d) repeating said steps (a)-(c) so as to sequence through each of said plurality of predetermined amplitudes.
Claim 2
Independent Claim
179 words
A method for imaging, using MR, a predetermined region of an object, which region is removed from the isocenter of an MR system having gradient coils for generating magnetic field gradients along the x, y and z axes of a Cartesian coordinate system, said MR system having RF means for exciting and receiving MR signals from said region, said method comprising the steps of: (a) exciting nuclear spins in said region; (b) applying a phase-encoding gradient having one of a plurality of predetermined amplitudes to phase encode spatial information into said excited nuclear spins, said phase-encoding gradient being applied along a y' axis rotated by an angle θ relative to the y axis; (c) receiving an MR signal from said excited spins in the presence of a readout magnetic field gradient applied along an X' axis which is orthogonal to said y' axis, said angle θ being greater than zero and selected such that said x' axis intersects said predetermined region; and (d) repeating said steps (a)-(c) so as to sequence through each of said plurality of predetermined amplitudes.
Claim 3
Dependent Claim
87 words
The method of claim 1 wherein said phase-encoding gradient is defined by g.sub.y y'=-g.sub.y sin (θ)x+g.sub.y cos (θ)y and wherein said readout gradient is defined by g.sub.x x'=g.sub.x cos (θ)x+g.sub.x sin (θ)y where g y is one of said predetermined amplitudes of said phase-encoding magnetic field gradient; g x is the amplitude of said readout magnetic field gradient; x and y are unit vectors directed along the x and y axes, respectively; and x' and y' are unit vectors directed along the x' and y' axes, respectively.
References Cited (Backward Citations)
US4015196A
Cited
US4471306A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-03-09 | 1990-09-08 | 1991-03-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-03-09 | 1994-09-08 | 1995-03-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-03-09 | 1998-09-08 | 1999-03-10 | $7700.00 | Window Closed / Lapsed |