US5289127A
Expired / Lapsed
US
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Correction of signal distortion in an NMR apparatus
Assignee: University of Queensland
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Filing: 1992-10-19
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Granted: 1994-02-22
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Expires: 2012-10-19
Abstract
Abstract Temporal B o shifts in NMR spectroscopy and/or imaging systems arising from pulsed field gradient induced eddy currents result in the distortion of free induction decay signals. A method of compensation of this distortion through modulation of the sender and/or receiver signal in opposite concert with the induced B o shifts is introduced. The method has the advantage of having a fast response and of not altering the magnetic gradient field. (FIG. 4)
Inventors
- 👤 David M. Doddrell
- 👤 Stuart Crozier
- 👤 Michael T. Gladwin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 09:29
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/54; G01R33/56; G01R33/565; G01R33/56518
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
96 words
A method for the compensation of signal distortion in an NMR apparatus, said NMR apparatus comprising a transmitter generating a spin excitation signal and a receiver detecting an NMR signal, and said signal distortion being caused by eddy currents induced by a switching on and off of a gradient magnetic field, said method comprising the steps of: A. Determining a time dependence of a magnitude of homogeneous B o component of a magnetic field and B. Phase modulating at least one of said spin excitation signal and said NMR signal to compensate for said time dependence.
Claim 2
Independent Claim
96 words
A method for the compensation of signal distortion in an NMR apparatus, said NMR apparatus comprising a transmitter generating a spin excitation signal and a receiver detecting an NMR signal, and said signal distortion being caused by eddy currents induced by a switching on and off of a gradient magnetic field, said method comprising the steps of: A. Determining a time dependence of a magnitude of homogeneous B o component of a magnetic field and B. Phase modulating at least one of said spin excitation signal and said NMR signal to compensate for said time dependence.
Claim 3
Dependent Claim
13 words
The method of claim 1, wherein said spin excitation signal is phase modulated.
Claim 4
Dependent Claim
24 words
The method of claim 2, wherein said spin excitation signal is phase modulated at a time during which said gradient magnetic field is on.
Claim 5
Dependent Claim
12 words
The method of claim 1, wherein said NMR signal is phase modulated.
Claim 6
Dependent Claim
17 words
The method of claim 1, wherein said spin excitation and said NMR signals are both phase modulated.
Claim 7
Dependent Claim
39 words
The method of claim 1, wherein said signal phase modulation is extracted for a given switching sequence of said gradient magnetic field by an analysis of said time dependence of said B o component for said given switching sequence.
Claim 8
Dependent Claim
27 words
The method of claim 1, wherein said time dependence of said B o component is extracted by a time dependent spherical harmonic expansion of said magnetic field.
Claim 9
Dependent Claim
17 words
The method of claim 7, wherein said magnetic field is measured at points on a spherical surface.
Claim 10
Dependent Claim
100 words
An NMR apparatus for the compensation of signal distortion caused by eddy currents induced by a switching on and off of a gradient magnetic field comprising: a transmitter to generate a spin excitation signal; a receiver to detect an NMR signal; phase modulation interference unit means, comprising a digital-to-analog-converter and an analog interface, for, after the time dependence of the magnitude of a homogeneous B o component of a magnetic field has been determined, phase modulating at least one of the spin excitation signal and the NMR signal, in order to compensate for the B o magnetic field time dependence.
Claim 11
Dependent Claim
100 words
An NMR apparatus for the compensation of signal distortion caused by eddy currents induced by a switching on and off of a gradient magnetic field comprising: a transmitter to generate a spin excitation signal; a receiver to detect an NMR signal; phase modulation interference unit means, comprising a digital-to-analog-converter and an analog interface, for, after the time dependence of the magnitude of a homogeneous B o component of a magnetic field has been determined, phase modulating at least one of the spin excitation signal and the NMR signal, in order to compensate for the B o magnetic field time dependence.
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| 3.5 Years (Year 4) | 1997-02-21 | 1997-08-23 | 1998-02-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-02-21 | 2001-08-23 | 2002-02-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-02-21 | 2005-08-23 | 2006-02-22 | $7700.00 | Window Closed / Lapsed |