US4812762A
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Fast method and device for determining an NMR distribution in a region of a body
Assignee: US Philips Corp
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Filing: 1987-12-22
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Granted: 1989-03-14
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Expires: 2007-12-22
Abstract
Abstract The invention relates to a method of making NMR images (density distributions, location-dependent spectroscopy) utilizing two alternating gradient fields whose gradient directions are mutually perpendicular. Thus, a two-dimensional "plane" in the 3-D image frequency space can be filled with a uniform density of measurement points. Per FID signal more signal samples can be taken, resulting in a substantial reduction of the entire measurement procedure for a 3-D image. This method is very suitable for imaging of 3-D density distributions, 2-D or 3-D spectroscopy etc. The periods and the amplitudes of the alternating gradient fields are preferably the same; however, these fields are preferably phase-shifted 90° with respect to one another.
Inventors
- 👤 Johannes H. den Boef
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 17:53
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/446; G01R33/48; G01R33/4818; G01R33/482; G01R33/4822; G01R33/54; G01R33/56; G01R33/561
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
192 words
A method of determining an NMR distribution in a region of a body situated in a steady, uniform magnetic field, said method comprising the steps of: (a) generating an r.f. electromagnetic pulse during a preparation period in order to cause a precessional motion of the magnetization of the nuclei in the body so as to generate a resonance signal, (b) then during a subsequent measurement period, generating a steady gradient magnetic field, a first alternating, periodic gradient magnetic field with a gradient direction extending in a first direction and a second alternating, periodic gradient magnetic field with a gradient direction extending perpendicularly to said first direction, said measurement period being divided into a number of sampling intervals, (c) during said measurement period taking a sample of said resonance signal during each of said sampling intervals so as to obtain a plurality of signal samples, and (d) then repeating, each time after a waiting period, steps (a), (b) and (c), said preparation period having a different duration during each repetition so as to obtain a group of signal samples from which, after Fourier transformation thereof, an image of a nuclear magnetization is determined.
Claim 2
Independent Claim
192 words
A method of determining an NMR distribution in a region of a body situated in a steady, uniform magnetic field, said method comprising the steps of: (a) generating an r.f. electromagnetic pulse during a preparation period in order to cause a precessional motion of the magnetization of the nuclei in the body so as to generate a resonance signal, (b) then during a subsequent measurement period, generating a steady gradient magnetic field, a first alternating, periodic gradient magnetic field with a gradient direction extending in a first direction and a second alternating, periodic gradient magnetic field with a gradient direction extending perpendicularly to said first direction, said measurement period being divided into a number of sampling intervals, (c) during said measurement period taking a sample of said resonance signal during each of said sampling intervals so as to obtain a plurality of signal samples, and (d) then repeating, each time after a waiting period, steps (a), (b) and (c), said preparation period having a different duration during each repetition so as to obtain a group of signal samples from which, after Fourier transformation thereof, an image of a nuclear magnetization is determined.
Claim 3
Dependent Claim
28 words
A method as claimed in claim 1 wherein said first and second alternating gradient magnetic fields have the same period and are phase-shifted with respect to one another.
Claim 4
Dependent Claim
21 words
A method as claimed in claim 2, wherein said first and second alternating gradient magnetic fields are 90° out of phase.
Claim 5
Dependent Claim
29 words
A method as claimed in claim 1, 2 or 3, characterized wherein per period of an alternating gradient magnetic field a signal sample is taken at least four times.
Claim 6
Dependent Claim
54 words
A method as claimed in claim 1, 2 or 3, wherein the starting instant of one of said first and second alternating gradient magnetic fields coincides with the end of the preparation period, the instant at which a first signal sample is taken always commencing the same time interval after the r.f. electromagnetic pulse.
Claim 7
Dependent Claim
27 words
A method as claimed in claim 1, 2 or 3, wherein during the successive measurement periods the amplitudes of the alternating gradient magentic fields are the same.
Claim 8
Dependent Claim
21 words
A method as claimed in claim 1, wherein eight signal samples are taken per period of an alternating gradient magnetic field.
Claim 9
Dependent Claim
64 words
A method as claimed in claim 1, 2 or 3, wherein the periods of said alternating gradient magnetic fields generated during successive measurement periods are different and the ratio of the maximum field intensity of the total alternating gradient magnetic field resulting from summation of the individual alternating gradient fields and the period is always smaller than or equal to a predetermined, fixed value.
Claim 10
Independent Claim
161 words
A device for determining an NMR distribution in a region of a body, said device comprising: (a) means for generating a steady, uniform magnetic field, (b) means for generating r.f. electromagnetic radiation so as to produce processional motion of the magnetization of nuclei in the body disposed in said uniform field and thereby generate a resonance signal, (c) means for generating a steady, gradient magnetic field, (d) means for generating at least two alternating, periodic gradient magnetic fields whose gradient directions are mutually perpendicular, (e) sampling means for taking signal samples of said resonance signal in the presence of said alternating gradient magnetic fields, (f) control means for controlling at least the means specified in paragraphs (b) to (e) so as to generate and sample a plurality of said resonance signals during successive measurement cycles, (g) processing means controlled by said control means for processing said signal samples taken during said measurement cycles so as to obtain an NMR distribution therefrom.
Claim 11
Independent Claim
161 words
A device for determining an NMR distribution in a region of a body, said device comprising: (a) means for generating a steady, uniform magnetic field, (b) means for generating r.f. electromagnetic radiation so as to produce processional motion of the magnetization of nuclei in the body disposed in said uniform field and thereby generate a resonance signal, (c) means for generating a steady, gradient magnetic field, (d) means for generating at least two alternating, periodic gradient magnetic fields whose gradient directions are mutually perpendicular, (e) sampling means for taking signal samples of said resonance signal in the presence of said alternating gradient magnetic fields, (f) control means for controlling at least the means specified in paragraphs (b) to (e) so as to generate and sample a plurality of said resonance signals during successive measurement cycles, (g) processing means controlled by said control means for processing said signal samples taken during said measurement cycles so as to obtain an NMR distribution therefrom.
Claim 12
Dependent Claim
24 words
A device as claimed in claim 9, wherein the periods of the alternating gradient magnetic fields are the same and 90° out of phase.
Claim 13
Dependent Claim
20 words
A device as claimed in claim 9 or 10, wherein the period of the alternating gradient magnetic fields is adjustable.
Claim 14
Dependent Claim
18 words
A device as claimed in claim 11, wherein the intensity of the alternating gradient magnetic fields is adjustable.
Claim 15
Independent Claim
214 words
A method of determining an NMR distribution in a region of a body situated in a steady, uniform magnetic field, said method comprising the steps of: (a) generating, during a preparation period, an r.f. electromagnetic pulse in order to cause a precessional motion of the magnetization of nuclei in the body so as to generate a resonance signal, (b) generating, during said preparation period, at least one preparation gradient magnetic field, (c) then during a subsequent measurement period, generating a first alternating, periodic gradient magnetic field with a gradient direction extending in a first direction and a second alternating, periodic gradient magnetic field with a gradient direction which extends perpendicularly to said first direction, said measurement period being divided into a number of sampling intervals, (d) during said measurement period, taking a sample of said resonance signal during each of said sampling intervals so as to obtain a plurality of signal samples, and (e) then repeating, each time after a waiting period, steps (a), (b), (c), and (d), the integral over the preparation period of said at least one preparation gradient magnetic field having a different value during each repetition in order to obtain a group of said signal samples from which, after Fourier transformation thereof, an image of a nuclear magnetization is determined.
Claim 16
Independent Claim
214 words
A method of determining an NMR distribution in a region of a body situated in a steady, uniform magnetic field, said method comprising the steps of: (a) generating, during a preparation period, an r.f. electromagnetic pulse in order to cause a precessional motion of the magnetization of nuclei in the body so as to generate a resonance signal, (b) generating, during said preparation period, at least one preparation gradient magnetic field, (c) then during a subsequent measurement period, generating a first alternating, periodic gradient magnetic field with a gradient direction extending in a first direction and a second alternating, periodic gradient magnetic field with a gradient direction which extends perpendicularly to said first direction, said measurement period being divided into a number of sampling intervals, (d) during said measurement period, taking a sample of said resonance signal during each of said sampling intervals so as to obtain a plurality of signal samples, and (e) then repeating, each time after a waiting period, steps (a), (b), (c), and (d), the integral over the preparation period of said at least one preparation gradient magnetic field having a different value during each repetition in order to obtain a group of said signal samples from which, after Fourier transformation thereof, an image of a nuclear magnetization is determined.
Claim 17
Dependent Claim
28 words
A method as claimed in claim 13, wherein said first and second alternating gradient magnetic fields have the same period and are phase-shifted with respect to one another.
Claim 18
Dependent Claim
21 words
A method as claimed in claim 14, wherein said first and second alternating gradient magnetic fields are 90° out of phase.
Claim 19
Dependent Claim
28 words
A method as claimed in claim 13, 14 or 15, wherein, per period of an alternating gradient magnetic field, a signal sample is taken at least four times.
Claim 20
Dependent Claim
55 words
A method as claimed in claim 13, 14 or 15, wherein one of said first and second alternating gradient magnetic fields starts at an instant which coincides with the end of the preparation period, the instant at which a first signal sample is taken always commencing the same time interval after the r.f. electromagnetic pulse.
Claim 21
Dependent Claim
27 words
A method as claimed in claim 13, 14 or 15, wherein the amplitudes of the respective alternating gradient magnetic fields are the same during successive measurement periods.
Claim 22
Dependent Claim
48 words
A method as claimed in claim 13, 14 or 15, wherein during the preparation period at least two of said preparation gradient magnetic fields are generated, the integral over the period of at least one preparation gradient magnetic field having a different value in two successive measurement periods.
Claim 23
Dependent Claim
63 words
A method as claimed in claim 19, wherein the gradient direction of one of said two preparation gradient magnetic fields is the same as the gradient directions of a respective one of the two alternating gradient magnetic fields and the gradient direction of the other preparation gradient magnetic field is the same as the gradient direction of the other alternating gradient magnetic field.
Claim 24
Dependent Claim
21 words
A method as claimed in claim 13, wherein eight signal samples are taken per period of an alternating gradient magnetic field.
Claim 25
Dependent Claim
64 words
A method as claimed in claim 13, 14 or 15, wherein the periods of said alternating gradient magnetic fields generated during successive measurement periods are different and the ratio of the maximum field intensity of the total alternating gradient magnetic field resulting from summation of the individual alternating gradient fields and the period is always smaller than or equal to a predetermined, fixed value.
Claim 26
Dependent Claim
22 words
A method as claimed in claim 13, 14 or 15, wherein a steady gradient magnetic field is generated during said measurement period.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-03-13 | 1992-09-12 | 1993-03-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-03-13 | 1996-09-12 | 1997-03-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-03-13 | 2000-09-12 | 2001-03-14 | $7700.00 | Window Closed / Lapsed |