US4814710A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of determining the spectral distribution of the nuclear magnetization in a limited volume range
Assignee: US Philips Corp
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Filing: 1987-02-27
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Granted: 1989-03-21
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Expires: 2007-02-27
Abstract
Abstract In order to avoid the disturbing influence of the decay of the transverse magnetization and/or of the eddy currents, a sequence comprising at least two high-frequency pulses is repeated n times, the distance being varied from sequence to sequence so that the position in time of the echo signals produced by the high-frequency pulses varies from sequence to sequence. If each time a sample value from each echo signal is used for the Fourier transformation which has a defined position with respect to the respective sequence, a frequency spectrum is obtained which does not depend or depends only to a smaller extent upon the said disturbing influences.
Inventors
- 👤 Graeme C. McKinnon
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 19:17
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/483; G01R33/4833; G01R33/54; G01R33/56; G01R33/565; G01R33/56518
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
125 words
A method for determining the spectral distribution of the nuclear magnetization in a limited volume range comprising the steps of repetitively producing sequences comprising at least two high-frequency pulses acting upon an examination area in the presence of a stationary homogeneous magnetic field, converting an echo signal produced in the volume range into digital sample values, and thereafter performing a Fourier transformation of the sample values wherein the position in time within the sequence of at least one high-frequency pulse is varied from sequence to sequence so that the position in time of the echo signal is displaced within successive sequences and, from each of these sequences, a sample value having a given position in time within the sequence is used for the Fourier transformation.
Claim 2
Independent Claim
125 words
A method for determining the spectral distribution of the nuclear magnetization in a limited volume range comprising the steps of repetitively producing sequences comprising at least two high-frequency pulses acting upon an examination area in the presence of a stationary homogeneous magnetic field, converting an echo signal produced in the volume range into digital sample values, and thereafter performing a Fourier transformation of the sample values wherein the position in time within the sequence of at least one high-frequency pulse is varied from sequence to sequence so that the position in time of the echo signal is displaced within successive sequences and, from each of these sequences, a sample value having a given position in time within the sequence is used for the Fourier transformation.
Claim 3
Dependent Claim
28 words
A method as claimed in claim 1, wherein each sequence comprises, for producing a resonance echo signal, a first 90° high-frequency pulse, and then a 180° high-frequency pulse.
Claim 4
Dependent Claim
21 words
A method as claimed in claim 1, wherein each sequence comprises, for producing a stimulated echo signal, three 90° high-frequency pulses.
Claim 5
Dependent Claim
129 words
A method as claimed in claim 3 wherein a magnetic gradient field is provided during each of said pulses and the polarity of the magnetic gradient field active during the first and the third high-frequency pulses is changed over after the first high-frequency pulse and the third high-frequency pulse, respectively, a magnetic gradient field having an opposite polarity is switched on by the second high-frequency pulse, and the variation with time of each of the gradient fields active during a high-frequency pulse is chosen so that the time integral is zero from the center of the first and the third high-frequency pulses, respectively, to the instant of switching-off the respective gradient field and from the switching-on instant of the gradient field to the center of the second high-frequency pulse.
Claim 6
Dependent Claim
59 words
A method as claimed in claim 3 or 4, wherein in the different sequences the first and the third high-frequency pulses have the same distance in time from each other and in that the position in time of the second high-frequency pulse with respect to the first and the third high-frequency pulses, respectively, is varied from sequence to sequence.
Claim 7
Independent Claim
42 words
A method as claimed in any one of claims 1 to 3, wherein the sample values from different sequences are subjected to a Fourier transformation, which sample values have the same distance in time from the first high-frequency pulse of the sequence.
Claim 8
Dependent Claim
53 words
A method as claimed in claim 2, wherein all sequences, magnetic gradient fields are switched on and off, respectively, in a fixed time relationship with the 180° pulse, and wherein each time those sample values from different sequences are subjected to a Fourier transformation at a fixed time from the 180° high-frequency pulse.
Claim 9
Dependent Claim
100 words
A method as claimed in claim 3, wherein in all sequences the second and the third high-frequency pulses have the same distance in time from each other, their distance from the first high-frequency pulse is varied from sequence to sequence, and magnetic gradient fields except one magnetic gradient field associated with the first high-frequency pulse, have in all sequences the same position in time with respect to the second and third high-frequency pulses and those sample values from the different sequences are subject to a Fourier transformation at a fixed time from the second and the third high-frequency pulses, respectively.
Claim 10
Independent Claim
62 words
A method as claimed in any one of claims 1-4, 7 or 8 characterized in that several sequences of sample values are subjected to a Fourier transformation, the sample values of a sequence each time having the same distance in time from one of the high-frequency pulses of the respective sequence, and in that the spectral distributions resulting therefrom are added together.
Claim 11
Dependent Claim
117 words
An arrangement for carrying out the method claimed in claim 1 comprising a magnet for producing a homogeneous stationary magnetic field, a high-frequency coil arrangement for producing a high-frequency magnetic field at right angles to the stationary magnetic field, a high-frequency generator for feeding the high-frequency coil arrangement, a control unit for controlling the high-frequency generator and a computer for processing nuclear magnetic resonance signals, characterized in that the control unit is constructed so that in each sequence at least two high-frequency pulses are produced, whose distance varies from sequence to sequence, and in that the computer is constructed so that it carries out a Fourier transformation with sample values of the echo signals from successive sequences.
References Cited (Backward Citations)
US4583044A
Cited
US4709212A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-03-20 | 1992-09-19 | 1993-03-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-03-20 | 1996-09-19 | 1997-03-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-03-20 | 2000-09-19 | 2001-03-21 | $7700.00 | Window Closed / Lapsed |