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EP0228056A2 Expired / Lapsed EP ⏱️ 0.0 years remaining

A method for magnetic field gradient eddy current compensation

Assignee: OFFERTA DI LICENZA AL PUBBLICO
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Filing: 1986-12-19
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Granted: —
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Expires: 2006-12-19
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Abstract

Abstract A method is provided for characterizing the spurious, time-dependent magnetic field gradient response and for compensating therefor. In accordance with the method a small sample object is placed away from the system isocenter where the gradient to be compensated is non-zero. A magnetic field gradient pulse is applied to the sample, followed by the application after a variable time of a 90° radio frequency pulse. The phase of the resulting free induction decay (FID) signal is monitored as a function of total time since the end of the gradient pulse. These data are related to the gradient impulse response and are fit to a set of (e.g., two or three) exponentials by regression techniques wherein an initial estimate is improved in one embodiment by chi-squared minimization of a Taylor's series expansion about the initial estimate point.

Inventors

  • 👤 Gary Harold Glover
  • 👤 Norbert Joseph Pelc

Bibliographic Details

Application Number —
Jurisdiction EP
Data Source google_patents
Last Synchronized 2026-11-09 23:16
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/54; G01R33/56; G01R33/565; G01R33/56518; G01R33/28; G01R33/38; G01R33/385

Claims Analysis

Total Claims: 2
Claim 1
Independent Claim 115 words
A method for magnetic field gradient eddy current compensation comprising the steps of: (a) positioning an NMR-active sample away from the isocenter of an MR scanner apparatus; (b) applying along at least one dimensional axis of said sample a gradient pulse; (c) irradiating said sample with an RF excitation pulse within a predetermined time following application of said gradient pulse so as to generate an NMR signal; (d) measuring the phase of said NMR signal as a function of the total time since the application of said gradient; (e) relating the measured phase to the impulse response of said gradient; and ( f ) compensating for magnetic field gradient eddy current using said impulse response.
Claim 2
Independent Claim 115 words
A method for magnetic field gradient eddy current compensation comprising the steps of: (a) positioning an NMR-active sample away from the isocenter of an MR scanner apparatus; (b) applying along at least one dimensional axis of said sample a gradient pulse; (c) irradiating said sample with an RF excitation pulse within a predetermined time following application of said gradient pulse so as to generate an NMR signal; (d) measuring the phase of said NMR signal as a function of the total time since the application of said gradient; (e) relating the measured phase to the impulse response of said gradient; and ( f ) compensating for magnetic field gradient eddy current using said impulse response.

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