Patent US4616183A successfully refreshed from Google Patents.
US4616183A
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Method for reducing baseline error components in NMR signals
Assignee: General Electric Co
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Filing: 1984-10-22
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Granted: 1986-10-07
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Expires: 2004-10-22
Abstract
Abstract A method for reducing baseline errors in NMR signals utilizes NMR signals produced by RF excitation pulses selected to be 180° out of phase relative to one another to derive a baseline error signal. The baseline error signal is then used to compensate for baseline error component in other NMR signals. In the preferred embodiment, the method is useful in NMR imaging pulse sequences to not only achieve compensation of the baseline error, but also to shorten scan time.
Inventors
- 👤 Gary H. Glover
- 👤 James R. MacFall
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 08:32
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/54; G01R33/56; G01R33/565
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
95 words
A method of performing NMR studies of a sample object, the method including multiple steps of exciting nuclear spins in a region of the sample object and receiving the resulting NMR signals, said method comprising: irradiating the sample object with at least one pair of RF pulses which are 180° out of phase relative to one another; deriving a first baseline error signal from the NMR signals due to said pair of RF pulses; and using the derived baseline error signal to compensate for the baseline error component in at least one other NMR signal.
Claim 2
Independent Claim
95 words
A method of performing NMR studies of a sample object, the method including multiple steps of exciting nuclear spins in a region of the sample object and receiving the resulting NMR signals, said method comprising: irradiating the sample object with at least one pair of RF pulses which are 180° out of phase relative to one another; deriving a first baseline error signal from the NMR signals due to said pair of RF pulses; and using the derived baseline error signal to compensate for the baseline error component in at least one other NMR signal.
Claim 3
Dependent Claim
43 words
The method of claim 1 wherein said pair of RF pulses comprise a pair of selective 90° RF excitation pulses applied in the presence of magnetic field gradients so as to selectively excite nuclear spins in a predetermined region of said sample object.
Claim 4
Dependent Claim
62 words
The method of claim 1 or 2 wherein said baseline error signal is derived using the equation B(t)=1/2[S.sub.1 (t)+S.sub.2 (t)], wherein B(t) is the baseline error signal, S 1 (t) is the NMR signal due to one of the pair of RF pulses, and S 2 (t) is the NMR signal due to the other one of the pair of RF pulses.
Claim 5
Dependent Claim
74 words
The method of claim 3 further comprising: subjecting said region of said sample object, following each of said steps of exciting nuclear spins, to at least one programmable amplitude, phase-encoding magnetic field gradient; and sampling the received NMR signals in the presence of a linear magnetic field gradient, said phase-encoding and linear magnetic field gradients encoding into said NMR signals spatial information useful for reconstructing an image of a region of the sample object.
Claim 6
Dependent Claim
29 words
The method of claim 4 wherein the amplitude of said phase-encoding magnetic field gradient is selected to be substantially identical for each of the RF pulses in said pair.
Claim 7
Dependent Claim
50 words
The method of claim 3 further comprising observing the received NMR signals in the presence of a linear magnetic field gradient having a plurality of directions within said region so as to encode sufficient line integral projection data to reconstruct an image of at least a portion of said region.
Claim 8
Dependent Claim
84 words
The method of claim 3 further comprising: irradiating said sample region with at least one additional pair of RF pulses which are 180° out of phase relative to one another; deriving a second baseline error signal from the NMR signals due to said additional pair of RF pulses; interpolating said first and second baseline error signals to produce a composite baseline error signal; and using said composite baseline error signal to compensate for the baseline error component in at least one other NMR signal.
Claim 9
Dependent Claim
27 words
The method of claim 3 wherein the resulting NMR signals comprise spin-echo signals produced by irradiating the excited nuclear spins with a plurality of 180° RF pulses.
Claim 10
Dependent Claim
13 words
The method of claim 1 wherein said NMR signals comprise free-induction decay signals.
Claim 11
Dependent Claim
12 words
The method of claim 1 wherein said NMR signals comprise spin-echo signals.
Claim 12
Dependent Claim
34 words
The method of claim 1 wherein said step of irradiating includes irradiating the sample object with at least a pair of 180° RF pulses which are 180° out of phase relative to one another.
Claim 13
Dependent Claim
68 words
The method of claim 18 wherein said baseline error signal is derived using the equation B(t)=S.sub.p (t)+DC, herein S p (t)=1/2(S 1 (t)-S 2 (t)), where S p (t) is the desired NMR signal, S 1 (t) and S 2 (t) are, respectively, NMR signals due to first and second of said 180° RF pulses, and DC is the output signal measured in the absence of RF excitation.
Claim 14
Independent Claim
187 words
A method of NMR imaging comprising: positioning a sample object to be imaged in a substantially homogeneous magnetic field; irradiating the sample object with a plurality of RF pulses so as to excite nuclear spins in a predetermined region to generate a corresponding plurality of NMR signals; observing said NMR signals in the presence of a linear magnetic field gradient to encode spatial information concerning at least one parameter associated with the excited nuclear spins; and applying at least one programmable amplitude, phase-encoding magnetic field gradient to said predetermined region prior to said step of observing to phase-encode spatial information concerning at least one parameter associated with the excited nuclear spins, wherein at least a pair of said RF pulses is selected to be 180° out of phase relative to one another and wherein the amplitude of said phase-encoding gradient is selected to be substantially identical for each of the RF pulses in said pair; deriving a baseline error signal from the NMR signals due to said pair of RF pulses; and compensating for the baseline error component in at least one of the remaining NMR signals.
Claim 15
Independent Claim
187 words
A method of NMR imaging comprising: positioning a sample object to be imaged in a substantially homogeneous magnetic field; irradiating the sample object with a plurality of RF pulses so as to excite nuclear spins in a predetermined region to generate a corresponding plurality of NMR signals; observing said NMR signals in the presence of a linear magnetic field gradient to encode spatial information concerning at least one parameter associated with the excited nuclear spins; and applying at least one programmable amplitude, phase-encoding magnetic field gradient to said predetermined region prior to said step of observing to phase-encode spatial information concerning at least one parameter associated with the excited nuclear spins, wherein at least a pair of said RF pulses is selected to be 180° out of phase relative to one another and wherein the amplitude of said phase-encoding gradient is selected to be substantially identical for each of the RF pulses in said pair; deriving a baseline error signal from the NMR signals due to said pair of RF pulses; and compensating for the baseline error component in at least one of the remaining NMR signals.
Claim 16
Dependent Claim
43 words
The method of claim 13 wherein said pair of RF pulses comprise a pair of selective 90° RF excitation pulses applied in the presence of magnetic field gradients so as to selectively excite nuclear spins in a predetermined region of said sample object.
Claim 17
Dependent Claim
62 words
The method of claim 13 or 14 wherein said baseline error signal is derived using the equation B(t)=1/2[S.sub.1 (t)+S.sub.2 (t)], wherein B(t) is the baseline error signal, S 1 (t) is the NMR signal due to one of the pair of RF pulses, and S 2 (t) is the NMR signal due to the other one of the pair of RF pulses.
Claim 18
Dependent Claim
84 words
The method of claim 15 further comprising: irradiating said sample region with at least one additional pair of RF pulses which are 180° out of phase relative to one another; deriving a second baseline error signal from the NMR signals due to said additional pair of RF pulses; interpolating said first and second baseline error signals to produce a composite baseline error signal; and using said composite baseline error signal to compensate for the baseline error component in at least one other NMR signal.
Claim 19
Dependent Claim
32 words
The method of claim 15 wherein the NMR signals resulting from said step of irradiating comprise spin-echo signals produced by irradiating the excited nuclear spins with a plurality of 180° RF pulse.
Claim 20
Dependent Claim
13 words
The method of claim 13 wherein said NMR signals comprise free-induction decay signals.
Claim 21
Dependent Claim
12 words
The method of claim 13 wherein said NMR signals comprise spin-echo signals.
References Cited (Backward Citations)
US3781650A
Cited
US4015196A
Cited
US4021726A
Cited
US4052661A
Cited
US4115730A
Cited
US4184110A
Cited
US4443760A
Cited
US4564017A
Cited
US4567893A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1989-10-06 | 1990-04-07 | 1990-10-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-10-06 | 1994-04-07 | 1994-10-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-10-06 | 1998-04-07 | 1998-10-07 | $7700.00 | Window Closed / Lapsed |