US4290019A
Expired / Lapsed
US
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Methods of deriving image information from objects
Assignee: BTG International Ltd
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Filing: 1979-02-09
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Granted: 1981-09-15
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Expires: 1999-02-09
Abstract
Abstract A method of deriving image formation from an object using nuclear magnetic resonance signals comprises the steps of subjecting an object to a static magnetic field along one axis, applying a first gradient to said magnetic field which varies in a direction orthogonal to said axis together with a 90° high frequency pulse, reversing the direction of said magnetic field gradient and simultaneously applying a gradient to said magnetic field which varies in a direction parallel to said one axis and then reversing the direction of said last-mentioned gradient and reading out the free induction signal from said object.
Inventors
- 👤 James M. S. Hutchison
- 👤 John R. Mallard
- 👤 Robert J. Sutherland
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 16:34
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/54
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
99 words
A method of deriving image information from an object using nuclear magnetic resonance signals comprising the steps of subjecting an object to a static magnetic field along one axis, applying a first gradient to said magnetic field which varies in a direction orthogonal to said axis together with a 90° high frequency pulse, reversing the direction of said magnetic field gradient and applying a second gradient to said magnetic field which varies in a direction orthogonal to said first gradient and then reversing the direction of said second gradient while reading out the free induction signal from said object.
Claim 2
Independent Claim
99 words
A method of deriving image information from an object using nuclear magnetic resonance signals comprising the steps of subjecting an object to a static magnetic field along one axis, applying a first gradient to said magnetic field which varies in a direction orthogonal to said axis together with a 90° high frequency pulse, reversing the direction of said magnetic field gradient and applying a second gradient to said magnetic field which varies in a direction orthogonal to said first gradient and then reversing the direction of said second gradient while reading out the free induction signal from said object.
Claim 3
Dependent Claim
59 words
The method as claimed in claim 1 and including a prior step of applying a third gradient to said magnetic field which varies in a direction orthogonal both to the first and second gradients and applying a high frequency pulse to the object in the presence of said third gradient to invert nuclear spins in a selective plane therein.
Claim 4
Dependent Claim
28 words
The method as claimed in claim 2 and including an interval between the application of the third gradient and the first gradient to allow inverted spins to relax.
Claim 5
Dependent Claim
32 words
The method as claimed in claim 1 in which the said gradient to said magnetic field which varies in a direction parallel to said axis is applied simultaneously with said first gradient.
Claim 6
Dependent Claim
28 words
The method as claimed in claim 1 in which the said gradients to said magnetic field are applied so that their rising and falling edges are time varying.
Claim 7
Independent Claim
220 words
A method of deriving image information using nuclear magnetic resonance signals from an object subjected to a static magnetic field along one axis comprising the steps of: applying a first gradient to said magnetic field which varies in a direction orthogonal to said axis together with a 90° high frequency pulse, reversing the direction of said magnetic field gradient and applying a second gradient to said magnetic field which varies in a direction orthogonal to said first gradient and then reversing the direction of said second gradient while reading out the free induction signal from said object to obtained an So signal; applying a third gradient to said magnetic field which varies in a direction orthogonal both to the first and second gradient and applying an inverting high frequency pulse to the object in the presence of said third gradient to invert nuclear spins in a selected plane therein, then immediately applying the first gradient to said magnetic field together with a 90° high frequency pulse, reversing the direction of said first gradient and applying the second gradient to said magnetic field and then reversing the direction of said second gradient while reading out the free induction signal from said object to obtain an S1 signal; and calculating a signal which is the difference between the So and S1 signals.
Claim 8
Independent Claim
220 words
A method of deriving image information using nuclear magnetic resonance signals from an object subjected to a static magnetic field along one axis comprising the steps of: applying a first gradient to said magnetic field which varies in a direction orthogonal to said axis together with a 90° high frequency pulse, reversing the direction of said magnetic field gradient and applying a second gradient to said magnetic field which varies in a direction orthogonal to said first gradient and then reversing the direction of said second gradient while reading out the free induction signal from said object to obtained an So signal; applying a third gradient to said magnetic field which varies in a direction orthogonal both to the first and second gradient and applying an inverting high frequency pulse to the object in the presence of said third gradient to invert nuclear spins in a selected plane therein, then immediately applying the first gradient to said magnetic field together with a 90° high frequency pulse, reversing the direction of said first gradient and applying the second gradient to said magnetic field and then reversing the direction of said second gradient while reading out the free induction signal from said object to obtain an S1 signal; and calculating a signal which is the difference between the So and S1 signals.
Claim 9
Dependent Claim
135 words
The method as claimed in claim 6 and including the additional steps of: applying a third gradient to said magnetic field which varies in a direction orthogonal both to the first and second gradient and applying an inverting high frequency pulse to the object in the presence of said third gradient to invert nuclear spins in a selected plane therein, providing a delay period and then applying the first gradient to said magnetic field together with a 90° high frequency pulse, receiving the direction of said first gradient and applying the second gradient to said magnetic field and then reversing the direction of said second gradient while reading out the free induction signal from said object to obtain an S2 signal; and calculating a signal which is the difference between the So and S2 signals.
Claim 10
Dependent Claim
24 words
The method as claimed in claim 7 in which the said delay period is comparable to the average spin-lattice relaxation time of the object.
Claim 11
Dependent Claim
47 words
The method as claimed in claim 7 in which the said steps are repeated for each of a series of different frequencies of the inverting high frequency pulses whereby a series of different planes are selected from each of which So, S1 and S2 signals are obtained.
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) | 1984-09-14 | 1985-03-16 | 1985-09-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-09-14 | 1989-03-16 | 1989-09-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-09-14 | 1993-03-16 | 1993-09-15 | $7700.00 | Window Closed / Lapsed |