Imaging magnetic spin resonance method and apparatus
First Claim
1. 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 thatthe interval (tau) between the first and the second of said three pulses is greater than T2eff and smaller than 5T2, and that the interval (T-tau) between the second and the third pulses is greater than T2eff and smaller than 5T1, whereinT1 is the spin-lattice relaxation time,T2 is the spin-spin relaxation time, andT2eff 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.
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Abstract
A method and an apparatus for a locally resolved investigation of a speci, 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.
41 Citations
39 Claims
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1. 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 T2eff and smaller than 5T2, and that the interval (T-tau) between the second and the third pulses is greater than T2eff and smaller than 5T1, wherein 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 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 36, 37, 38, 39)
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35. 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 T2eff and smaller than 5T2, and that the interval (T-tau) between the second and the third pulses is greater than T2eff and smaller than 5T1, wherein 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, 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.
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Specification