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US4748409A
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Imaging magnetic spin resonance method and apparatus
Assignee: Max-Planck-Gesellschaft zur Förderung der Wissenschaften eV
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Filing: 1985-12-09
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Granted: 1988-05-31
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Expires: 2005-12-09
Abstract
Abstract A method and an apparatus for a locally resolved investigation of a specimen, wherein the specimen is exposed to a constant magnetic field and a variable combination of three gradient magnetic fields directed substantially perpendicularly to each other and to a sequence of high-frequency (RF) pulses which contains three successive pulses with flip angles not equal to ¦m Pi¦, and signals corresponding to a magnetic resonance of spin moments, in particular nuclear spin moments in said specimen are detected. The interval (tau) between the first and the second pulse is greater than T2eff and smaller than 5T2, and that the interval (T-tau) between the second and the third pulse is greater than T2eff and smaller than 5T1, wherein m is an integer, T1 is the spin-lattice relaxation time, T2 is the spin-spin relaxation time and T2eff is the effective spin-spin relaxation time of the spins to be determined in the specimen. At least one of said gradient fields is switched between the first and/or the second pulse and/or the second and the third pulse and/or after the third pulse, wherein at least one of the RF pulses is a frequency-selective pulse and at least one echo signal stimulated by the third pulse is detected and evaluated.
Inventors
- 👤 Jens Frahm
- 👤 Axel Haase
- 👤 Wolfgang Haenicke
- 👤 Klaus-Dietmar Merboldt
- 👤 Dieter Matthaei
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 23:17
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/483; G01R33/4833; G01R33/4818; G01R33/482
Claims Analysis
Total Claims: 41
Claim 1
Independent Claim
234 words
A method for locally resolved investigation of a specimen, in which the specimen is exposed to a constant magnetic field and a variable combinatio of three gradient magnetic fields directed substantially perpendicularly to each other and the specimen is subjected to a sequence of high-frequency pulses which sequence contains three successive pulses with flip angles differeing from 180 degrees and multiples thereof, and in which signals corresponding to a magnetic resonance of spin moments, in particular of nuclear spin moments, are measured, characterized in that the interval (tau) between the first and the second of said three pulses is greater than T 2eff and smaller than 5T 2 , and that the interval (T-tau) between the second and the third pulses is greater than T 2eff and smaller than 5T 1 , wherein T 1 is the spin-lattice relaxation time, T 2 is the spin-spin relaxation time, and T 2eff is the effective spin-spin relaxation time of the spinds to be determined in the specimen, that at least one of the gradient fields is switched over during at least one of the following periods of time: (a) between the first and the second pulses, (b) between the second and the third pulses, (c) after the third pulse, that at least one of the pulses is a frequency-selective pulse and that at least one echo signal stimulated by the third pulse is detected and evaluated.
Claim 2
Independent Claim
234 words
A method for locally resolved investigation of a specimen, in which the specimen is exposed to a constant magnetic field and a variable combinatio of three gradient magnetic fields directed substantially perpendicularly to each other and the specimen is subjected to a sequence of high-frequency pulses which sequence contains three successive pulses with flip angles differeing from 180 degrees and multiples thereof, and in which signals corresponding to a magnetic resonance of spin moments, in particular of nuclear spin moments, are measured, characterized in that the interval (tau) between the first and the second of said three pulses is greater than T 2eff and smaller than 5T 2 , and that the interval (T-tau) between the second and the third pulses is greater than T 2eff and smaller than 5T 1 , wherein T 1 is the spin-lattice relaxation time, T 2 is the spin-spin relaxation time, and T 2eff is the effective spin-spin relaxation time of the spinds to be determined in the specimen, that at least one of the gradient fields is switched over during at least one of the following periods of time: (a) between the first and the second pulses, (b) between the second and the third pulses, (c) after the third pulse, that at least one of the pulses is a frequency-selective pulse and that at least one echo signal stimulated by the third pulse is detected and evaluated.
Claim 3
Dependent Claim
15 words
Method according to claim 1, characterized in that tau is smaller than 2T 2 .
Claim 4
Dependent Claim
15 words
Method according to claim 1, characterized in that (T-tau) is smaller than 3T 2 .
Claim 5
Dependent Claim
26 words
Method according to claim 1, characterized in that the frequency-selective pulse is replaced by a sequence of separate single pulses which gives the necessary frequency selectivity.
Claim 6
Dependent Claim
19 words
Method according to claim 4, characterized in that at least two of the single pulses contain different carrier frequencies.
Claim 7
Dependent Claim
16 words
Method according to claim 4, characterized in that the single pulses contain the same carrier frequencies.
Claim 8
Dependent Claim
41 words
Method according to claim 6, characterized in that the single pulses are non-selective ("hard") pulses, i.e. a substantially rectangular envelope curve, have as short as possible a duration and as high as possible an amplitude and in themselves are not selective.
Claim 9
Dependent Claim
18 words
Method according to claim 1, characterized in that the at least one frequency-selective pulse is a frequency-modulated pulse.
Claim 10
Dependent Claim
17 words
Method according to claim 1, characterized in that the first pulse is a |90 degree| pulse (±10%).
Claim 11
Dependent Claim
17 words
Method according to claim 1, characterized in that the second pulse is a |90 degree| pulse (±50%).
Claim 12
Dependent Claim
17 words
Method according to claim 1, characterized in that the third pulse is a |90 degree| pulse (±50%).
Claim 13
Dependent Claim
21 words
Method according to claim 1, characterized in that at least the first and the second pulse are substantially 90 degree pulses.
Claim 14
Dependent Claim
64 words
Method according to claim 1, characterized in that the third pulse is a pulse corresponding to a fraction of said flip angle, that the third pulse is followed by at least one further "fraction pulse" at a distance which is greater than the distance betweenthe first and second pulses, and that each stimulated echo following one of the further pulses is detected and evaluated.
Claim 15
Dependent Claim
20 words
Method according to claim 13, characterized in that the flip angle of each fraction pulse is less than 15 degrees.
Claim 16
Dependent Claim
23 words
Method according to claim 13, characterized in that the spacing of each fraction pulse from the preceding pulse is greater than 2 tau.
Claim 17
Dependent Claim
25 words
Method according to claim 13, characterized in that the flip angle of each further pulse is greater than the flip angle of each preceding pulse.
Claim 18
Dependent Claim
15 words
Method according to claim 1, characterized in that the first pulse is a slice pulse.
Claim 19
Dependent Claim
15 words
Method according to claim 1, characterized in that the second pulse is a slice pulse.
Claim 20
Dependent Claim
15 words
Method according to claim 1, characterized in that the second pulse is a slice pulse.
Claim 21
Dependent Claim
18 words
Method according to claim 17, characterized in that the remaining pulses of the three pulses are non-selective pulses.
Claim 22
Dependent Claim
18 words
Method according to claim 18, characterized in that the remaining pulses of the three pulses are non-selective pulses.
Claim 23
Dependent Claim
18 words
Method according to claim 19, characterized in that the remaining pulses of the three pulses are non-selective pulses.
Claim 24
Dependent Claim
26 words
Method according to claim 1, characterized in that one of the pulses is a slice pulse and another of the pulses is a fragment (zoom pulse).
Claim 25
Dependent Claim
18 words
Method according to claim 1, characterized in that at least one of the pulses is a resonance-line-selective pulse.
Claim 26
Dependent Claim
15 words
Method according to claim 1, characterized in that the first pulse is a resonance-line-selective pulse.
Claim 27
Dependent Claim
15 words
Method according to claim 1, characterized in that the first pulse is a slice pulse.
Claim 28
Dependent Claim
17 words
Method according to claim 1, characterized in that the first pulse is a fragment or zoom pulse.
Claim 29
Dependent Claim
16 words
Method according to claim 23, characterized in that the second pulse is a non-selective (hard) pulse.
Claim 30
Dependent Claim
16 words
Method according to claim 24, characterized in that the second pulse is a non-selective (hard) pulse.
Claim 31
Dependent Claim
16 words
Method according to claim 25, characterized in that the second pulse is a non-selective (hard) pulse.
Claim 32
Dependent Claim
15 words
Method according to claim 23, characterized in that the second pulse is a slice pulse.
Claim 33
Dependent Claim
15 words
Method according to claim 24, characterized in that the second pulse is a slice pulse.
Claim 34
Dependent Claim
15 words
Method according to claim 25, characterized in that the second pulse is a slice pulse.
Claim 35
Dependent Claim
32 words
Method according to claim 1, characterized in that the generation, observation and evaluation of stimulated echo signals is combined with other methods, in particular spinecho tomography methods, by adding 180 degrees pulses.
Claim 36
Independent Claim
250 words
An apparatus for locally resolved investigation of a specimen, said apparatus comprising means for exposing a specimen to a constant magnetic field and a variable combination of three gradient magnetic fields directed substantially perpendicularly to each other and to a sequence of high-frequency (RF) pulses which contains three successive pulses with flip angles differing from 180 degrees and multiples thereof, and means (24,30,14) for detecting signals corresponding to a magnetic resonance of spin moments, in particular of nuclear spin moments in said specimen, characterized in that said exposing means (14,16,18,20,22,24,30) produces said sequence so that the interval (tau) between the first and the second of said three pulses is greater than T 2eff and smaller than 5T 2 , and that the interval (T-tau) between the second and the third pulses is greater than T 2eff and smaller than 5T 1 , wherein T 1 is the spin-lattice relaxation time, T 2 is the spin-spin relaxation time, and T 2eff is the effective spin-spin relaxation time of the spins to be determined in the specimen, said exposing means further effecting switching of at least one of said gradient fields during at least one of the following periods of time: (a) between the first and the second pulses, (b) between the second and the third pulses, (c) after the third pulse, wherein at least one of the RF pulses is a frequency-selective pulse and wherein said detecting means detects at least one echo signal, stimulated by the third pulse, for evaluation.
Claim 37
Independent Claim
250 words
An apparatus for locally resolved investigation of a specimen, said apparatus comprising means for exposing a specimen to a constant magnetic field and a variable combination of three gradient magnetic fields directed substantially perpendicularly to each other and to a sequence of high-frequency (RF) pulses which contains three successive pulses with flip angles differing from 180 degrees and multiples thereof, and means (24,30,14) for detecting signals corresponding to a magnetic resonance of spin moments, in particular of nuclear spin moments in said specimen, characterized in that said exposing means (14,16,18,20,22,24,30) produces said sequence so that the interval (tau) between the first and the second of said three pulses is greater than T 2eff and smaller than 5T 2 , and that the interval (T-tau) between the second and the third pulses is greater than T 2eff and smaller than 5T 1 , wherein T 1 is the spin-lattice relaxation time, T 2 is the spin-spin relaxation time, and T 2eff is the effective spin-spin relaxation time of the spins to be determined in the specimen, said exposing means further effecting switching of at least one of said gradient fields during at least one of the following periods of time: (a) between the first and the second pulses, (b) between the second and the third pulses, (c) after the third pulse, wherein at least one of the RF pulses is a frequency-selective pulse and wherein said detecting means detects at least one echo signal, stimulated by the third pulse, for evaluation.
Claim 38
Dependent Claim
27 words
The method of claim 1, wherein at least one gradient field is switched over between said first and second pulses and between said second and third pulses.
Claim 39
Dependent Claim
25 words
The method of claim 1, wherein at least one graident field is switched over between said first and second pulses and after said third pulse.
Claim 40
Dependent Claim
25 words
The method of claim 1, wherein at least one gradient field is switched over between said second and third pulses and after said third pulse.
Claim 41
Dependent Claim
32 words
The method of claim 1, wherein at least one gradient field is switched over between said first and second pulses, and between said second and third pulses, and after said third pulse.
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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) | 1991-05-31 | 1991-11-30 | 1992-05-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-05-31 | 1995-11-30 | 1996-05-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-05-31 | 1999-11-30 | 2000-05-31 | $7700.00 | Window Closed / Lapsed |