US4706025A
Expired / Lapsed
US
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Methods of producing image formation from objects
Assignee: BTG International Ltd
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Filing: 1986-06-27
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Granted: 1987-11-10
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Expires: 2006-06-27
Abstract
Abstract To produce image information from an object it is subjected to a continuous static magnetic field along a Z axis and to sets of sequences of orthogonal gradients G x , G y and G z to the magnetic field. Spins in a selected plane (the X-Z plane) are excited by selective rf pulses and an associated G y gradient and the selected spins are subjected to all three gradients of which the G z gradient provides twist or warp to each column of spins extending along the Z axis to phase-encode the columns. The spin-echo signals are read out in the presence of a G x gradient. In each set of sequences a different value of Z gradient is employed. The Fourier transformed spin-echo signals obtained from each sequence, when arranged in order of increasing G z gradient and subjected to a second Fourier transform represent the distribution of spin density in the Z direction, thus giving a two-dimensional image of the selected X-Z plane.
Inventors
- 👤 William A. Edelstein
- 👤 James M. S. Hutchison
- 👤 Glyn Johnson
- 👤 Thomas W. T. Redpath
- 👤 John R. Mallard
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 06:48
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/4818; G01R33/482; G01R33/54; G01R33/56; G01R33/561; G01R33/5615; G01R33/5616
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
90 words
In a method of deriving image information from an object using nuclear magnetic resonance signals the improvement comprising: subjecting an object to a continuous static magnetic field along an axis and carrying out a set of sequential steps which comprise: (1) inverting selected nuclear spins in a selected plane in the presence of a plane selection gradient of the static magnetic field, the direction of said plane selection gradient being perpendicular to said plane; (2) allowing the inverted spins to relax for an interval comparable with their spin-lattice relaxation time;
Claim 2
Dependent Claim
90 words
In a method of deriving image information from an object using nuclear magnetic resonance signals the improvement comprising: subjecting an object to a continuous static magnetic field along an axis and carrying out a set of sequential steps which comprise: (1) inverting selected nuclear spins in a selected plane in the presence of a plane selection gradient of the static magnetic field, the direction of said plane selection gradient being perpendicular to said plane; (2) allowing the inverted spins to relax for an interval comparable with their spin-lattice relaxation time;
Claim 3
Dependent Claim
206 words
(3) exciting said selected nuclear spins in the presence of said plane selection gradient of the static magnetic field; (4) rephasing the selected nuclear spins in the selected plane in a direction parallel to the direction of the said plane selection gradient by applying the said plane selection gradient in the reverse direction, applying a phase encoding gradient of the magnetic field having a gradient direction parallel to the selected plane for phase encoding the selected nuclear spins in the direction of the phase encoding gradient, applying a dephasing gradient of the static magnetic field having a gradient direction orthogonal to both the phase selection gradient direction and the phase encoding gradient direction, said rephasing, phase encoding and dephasing gradients all being applied simultaneously; (5) removing the said rephasing, phase encoding and dephasing gradients and reading out the resultant free induction signal from the said object in the presence of a read gradient of the magnetic field having a gradient direction which is reverse to the direction of the said dephasing gradient; and then successively repeating the above set of sequential steps with different values of time integral of the phase encoding gradient, there being a recovery interval between the repetition of successive sets of steps.
Claim 4
Dependent Claim
206 words
(3) exciting said selected nuclear spins in the presence of said plane selection gradient of the static magnetic field; (4) rephasing the selected nuclear spins in the selected plane in a direction parallel to the direction of the said plane selection gradient by applying the said plane selection gradient in the reverse direction, applying a phase encoding gradient of the magnetic field having a gradient direction parallel to the selected plane for phase encoding the selected nuclear spins in the direction of the phase encoding gradient, applying a dephasing gradient of the static magnetic field having a gradient direction orthogonal to both the phase selection gradient direction and the phase encoding gradient direction, said rephasing, phase encoding and dephasing gradients all being applied simultaneously; (5) removing the said rephasing, phase encoding and dephasing gradients and reading out the resultant free induction signal from the said object in the presence of a read gradient of the magnetic field having a gradient direction which is reverse to the direction of the said dephasing gradient; and then successively repeating the above set of sequential steps with different values of time integral of the phase encoding gradient, there being a recovery interval between the repetition of successive sets of steps.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-11-09 | 1991-05-11 | 1991-11-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-11-09 | 1995-05-11 | 1995-11-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-11-09 | 1999-05-11 | 1999-11-10 | $7700.00 | Window Closed / Lapsed |