WO2002075346A1 - Procede d'imagerie par resonance magnetique pour analyser un echantillon par acquisition de signaux d'echo de spin et d'echo de gradient - Google Patents

Procede d'imagerie par resonance magnetique pour analyser un echantillon par acquisition de signaux d'echo de spin et d'echo de gradient Download PDF

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Publication number
WO2002075346A1
WO2002075346A1 PCT/DE2002/000711 DE0200711W WO02075346A1 WO 2002075346 A1 WO2002075346 A1 WO 2002075346A1 DE 0200711 W DE0200711 W DE 0200711W WO 02075346 A1 WO02075346 A1 WO 02075346A1
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WO
WIPO (PCT)
Prior art keywords
echo
excitation
pulse
spin
gradient
Prior art date
Application number
PCT/DE2002/000711
Other languages
German (de)
English (en)
Inventor
Nadim Joni Shah
Karl Zilles
Original Assignee
Forschungszentrum Jülich GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Forschungszentrum Jülich GmbH filed Critical Forschungszentrum Jülich GmbH
Publication of WO2002075346A1 publication Critical patent/WO2002075346A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems
    • G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
    • G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
    • G01R33/561—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution by reduction of the scanning time, i.e. fast acquiring systems, e.g. using echo-planar pulse sequences
    • G01R33/5615—Echo train techniques involving acquiring plural, differently encoded, echo signals after one RF excitation, e.g. using gradient refocusing in echo planar imaging [EPI], RF refocusing in rapid acquisition with relaxation enhancement [RARE] or using both RF and gradient refocusing in gradient and spin echo imaging [GRASE]
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems
    • G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
    • G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
    • G01R33/561—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution by reduction of the scanning time, i.e. fast acquiring systems, e.g. using echo-planar pulse sequences
    • G01R33/5615—Echo train techniques involving acquiring plural, differently encoded, echo signals after one RF excitation, e.g. using gradient refocusing in echo planar imaging [EPI], RF refocusing in rapid acquisition with relaxation enhancement [RARE] or using both RF and gradient refocusing in gradient and spin echo imaging [GRASE]
    • G01R33/5617—Echo train techniques involving acquiring plural, differently encoded, echo signals after one RF excitation, e.g. using gradient refocusing in echo planar imaging [EPI], RF refocusing in rapid acquisition with relaxation enhancement [RARE] or using both RF and gradient refocusing in gradient and spin echo imaging [GRASE] using RF refocusing, e.g. RARE

Definitions

  • the invention relates to a method for examining a sample with at least one imaging sequence, wherein at least one excitation pulse and several rephasing pulses are irradiated into the sample, and at least one echo signal arises and is determined.
  • sample in its broadest meaning and includes living and non-living material.
  • Nuclear magnetic resonance imaging is preferably used to obtain spectroscopic information or image information about a substance.
  • a combination of nuclear magnetic resonance imaging with techniques of magnetic resonance imaging gives a spatial picture of the chemical composition of the substance.
  • Magnetic resonance imaging is, on the one hand, a sophisticated imaging method that is in clinical use worldwide. On the other hand, magnetic resonance imaging is also a very important examination tool for industry and research outside of the medical field. Applications are, for example, investigations of food, quality controls, preclinical investigations of medicines in the pharmaceutical industry or the investigation of geological structures such as pore sizes in rock samples for petroleum exploration.
  • Larmor frequency depends on the strength of the magnetic field and the magnetic properties of the substance, especially the gyromagneti Co.
  • Constant ⁇ of the nucleus is a characteristic quantity for each atom type.
  • a substance to be examined, or a person to be examined, is used in the
  • the uniform magnetic field is also referred to as the polarization field B 0 and the axis of the uniform magnetic field as the z-axis.
  • the individual magnetic moments of the spins in the tissue precess with their characteristic Larmor frequency around the axis of the uniform magnetic field.
  • a net magnetization M z is generated in the direction of the polarization field, the randomly oriented magnetic components canceling each other in the plane perpendicular to this (xy plane).
  • an excitation field Bi is additionally generated.
  • the excitation field Bx is polarized in the xy plane and has a frequency that is as close as possible to the Larmor frequency.
  • the net magnetic moment M z can be tilted into the xy plane, so that a transverse magnetic magnetization M t arises.
  • the transverse component of the magnetization rotates in the xy Level with the Larmor frequency.
  • Magnetic resonance spectroscopy enables the measurement of the spatial density distribution of certain chemical components in a material, especially in biological tissue.
  • Rapid magnetic resonance imaging (MRI) in conjunction with magnetic resonance spectroscopy (MRS) makes it possible to investigate local distributions of metabolic processes. For example, regional hemodynamics with changes in blood volumes and blood conditions as well as changes in metabolism in vivo depending on brain activity are determined, see: S. Posse et. al. : Functional Magnetic Resonance Studies of Brain Activation; Seminars in Clinical Neuropsychiatry, Vol. 1, No 1, 1996; p. 76-88.
  • NMR imaging methods are used to select layers or volumes which, under the appropriate irradiation of high-frequency pulses and the application of magnetic gradient fields, deliver a measurement signal which is digitized and stored in the measurement computer as a one- or multi-dimensional field.
  • the desired image information is obtained (reconstructed) from the recorded raw data by means of a one-dimensional or multi-dimensional Fourier transformation.
  • a reconstructed slice consists of pixels, a Volume data set from voxels.
  • a pixel picture element
  • a voxel volume pixel
  • the dimensions of a pixel are on the order of 1mm 2 , those of a voxel of 1mm 3 .
  • the geometries and dimensions can be variable.
  • fMRI Functional magnetic resonance imaging
  • DOH Deoxyhemoglobin
  • Oxyhemoglobin has a magnetic susceptibility, which essentially corresponds to the tissue structure in the brain, so that magnetic field gradients across a boundary between blood containing oxyhemoglobin and the tissue are very small. If the DOH concentration drops due to brain activity that triggers increasing blood flow, the signal relaxation in the active areas of the brain is slowed down. The protons of hydrogen in water are primarily excited.
  • the known methods require preliminary examinations in order to obtain correction data for the images.
  • the invention has for its object to develop a generic method that a high Has signal-to-noise ratio and with which a quick signal detection is possible.
  • this object is achieved in that at least one rephasing pulse is radiated in after the excitation pulse, that one or more spin echo excitations take place after the rephasing pulse, that an echo signal is detected after the spin echo excitation (s), and that after the Detection of the echo signal, one or more further spin echo excitations take place.
  • a further improvement in the signal-to-noise ratio can be achieved in a particularly simple and advantageous manner in that exactly one spin-echo excitation takes place between the irradiation of the rephasing pulse and the detection of the echo signal.
  • spin echo signals (SE) and gradient echo signals (GE) are acquired alternately.
  • Image information is advantageously obtained by repeating the recording sequence at least once.
  • gradient echo signals which were recorded at the same echo time T E are displayed as one image.
  • spin echo signals which were recorded at the same echo time T E , are displayed as one image.
  • a particularly advantageous embodiment of the invention is characterized in that images in the form of an NX N matrix in a sequence sequence [GE (1,1), SE (2,1), GE (3,1), ..., GE1 , N, SE (2, N), GE (3, N), ..., SE (N, N)] can be detected.
  • Both the relaxation time T 2 and the relaxation time T 2 * can be reliably determined in the manner shown.
  • the echo signals are rearranged so that echo signals that were recorded at the same echo time T are displayed as one image.
  • N repetitions of the recording sequence to take place in the form of an N x N matrix.
  • the imaging method is preferably a spectroscopic echo planar imaging method, in particular a repeated two-dimensional echo planar imaging method, which consists of a repeated application of a two-dimensional echo planar image coding.
  • Spatial coding takes place in the shortest possible time, which can be repeated several times during a signal drop and is preferably 20 to 100 ms.
  • the repeated repetition of the echo planar coding shows a course of the signal drop in the sequence of reconstructed individual images during a signal drop.
  • the relaxation time T 2 is quantized using a plurality of images which are recorded at different echo times. For a given matrix size, the number of images is limited by the properties of the measuring apparatus and the value of T 2 . In order to generate quantitative images, data must therefore be adapted based on a limited number of data points that may be noisy.
  • the drawing shows a sequence diagram of a preferred embodiment of a method according to the invention.
  • Fig. 1 different components of the sequence are shown one above the other in chronological order.
  • Individual lines, each extending in a horizontal line, reflect the time dependence of individual parameters.
  • the individual parameters are arranged one above the other in such a way that simultaneous events are directly one above the other.
  • the created or resulting field RF is shown in a line representing the time dependence of the field and corresponding to a pulse sequence.
  • the first gradient field G s preferably extends in a main direction of a uniform magnetic field B 0 .
  • the magnetic field B 0 is also referred to as the polarization field and the axis of the uniform magnetic field as the z-axis.
  • a layer of a sample to be examined is selected by the gradient field G s . So that's why Gradient field G s also referred to as slice selection gradient. In order to be able to differentiate the different gradients better, the designation G s is used below for the slice selection gradient.
  • the phase coding gradient G P is preferably along a y axis. It is used to select lines of an impulse space to be examined.
  • a third gradient field is shown below the further gradient field, which corresponds to a reading gradient G R.
  • the reading gradient G R is preferably along an x-axis. It is used to read out signals, in particular echo signals from the sample to be examined. A reproduction of the signals in the form to allow an image to be with the read gradient G R more, in FIG. 1 one above the other illustrated performed acquisition sequences.
  • a net magnetization of the sample to be examined is excited by an excitation pulse AP, preferably a 90 ° pulse, shown in the top line on the left.
  • the excitation pulse AP has a duration of, for example, 1 to 10 milliseconds, with one Duration of 2 to 3 milliseconds is particularly preferred.
  • a first slice selection gradient G s l is applied to the sample, which leads to a partial dephasing of the transverse magnetization.
  • the spins are rephased by a further slice selection gradient G s 2 with a changed sign.
  • a time integral of the further slice selection gradient G s is preferably half as large as the time integral of the first slice selection gradient G s applied during the excitation pulse.
  • the further slice selection gradient G s acts as a rephasing gradient.
  • a rephasing pulse RP1 is then irradiated. It is expedient that the rephasing pulse RP1 is irradiated with a phase shift of 90 ° with respect to the excitation pulse AP. To select a layer, the is preferably used simultaneously
  • the layer is in particular the same layer as before.
  • the first rephasing pulse RP1 there is a spin echo excitation.
  • a spin echo excitation instead of the one spin echo excitation shown, several spin echo excitations can also take place, but the case shown is a single one Spin-echo excitation between the rephasing pulse RP1 and a detection of the echo signal is preferred.
  • the echo signal is then recorded.
  • the desired echo signals are read out.
  • spin echo excitation After observing the echo signal, a further spin echo excitation takes place. Although a single spin echo excitation is preferred, several spin echo excitations can also take place. If several spin echo excitations occur, they preferably have opposite signs.
  • this spin echo excitation has the same sign as the first spin echo excitation.
  • a further rephasing pulse RP2 then takes place, whereupon an echo signal is generated and measured.
  • a time development is recorded by repeating the individual measurements.
  • the sequence of the field shown in the top line runs as long as it corresponds to a desired number of sampling points of a T 2 relaxation curve.
  • the method is repeated as often as it corresponds to the number N y of lines of a desired (N y x N x ) image matrix.
  • SE Spin echo signals
  • GE gradient echo signals
  • each recording sequence contains N excitation pulses.
  • the recording sequence is repeated N times.
  • the number of rephasing pulses is preferably identical to the desired number of sampling points on the T 2 relaxation curve.
  • the invention provides for artifacts due to an essentially identical phase position between different ones Suppress recording sequences.
  • a rearrangement of echo signals is made possible by the invention. This ensures that only those echo signals that correspond to a desired echo time T E are reproduced in a desired level of the pulse space. In this way, a convolution of the signal with a, T 2 * decay function can be avoided. This is particularly useful if the impulse space is passed through from central areas to central areas up to - opposite to the first areas - external areas. This ensures that the spatial resolution remains high in the entire pulse space.
  • Data corresponding to central areas of the pulse space and coded with a 0-phase can be used for phase correction of measurement data of further recording sequences. In this way, preliminary measurements of the samples to be examined can be avoided.
  • Frequency-selective lipid presaturation is preferably used.

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Radiology & Medical Imaging (AREA)
  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)

Abstract

L'invention concerne un procédé pour analyser un échantillon à l'aide d'au moins une séquence d'imagerie, ce procédé consistant à envoyer sur l'échantillon au moins une impulsion d'excitation et plusieurs impulsions de rephasage de sorte qu'au moins un signal d'écho soit produit et détecté. Selon l'invention, ce procédé se caractérise en ce qu'au moins une impulsion de rephasage est envoyée suite à l'impulsion d'excitation, une ou plusieurs excitations d'écho de spin se produisent suite à cette impulsion de rephasage, un signal d'écho est acquis suite à cette ou ces excitations d'écho de spin et une ou plusieurs autres excitations d'écho de spin se produisent suite à l'acquisition du signal d'écho.
PCT/DE2002/000711 2001-03-15 2002-02-28 Procede d'imagerie par resonance magnetique pour analyser un echantillon par acquisition de signaux d'echo de spin et d'echo de gradient WO2002075346A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE2001112879 DE10112879A1 (de) 2001-03-15 2001-03-15 Verfahren zur Untersuchung einer Probe mittels Erzeugung und Ermittlung von Echosignalen
DE10112879.7 2001-03-15

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4709212A (en) * 1986-01-03 1987-11-24 General Electric Company Method of enhancing image signal-to-noise ratio by combining NMR images of differing pulse sequence timing
US4896113A (en) * 1988-11-25 1990-01-23 General Electric Company Use of repeated gradient echoes for noise reduction and improved NMR imaging
JPH0282942A (ja) * 1988-09-20 1990-03-23 Toshiba Corp 磁気共鳴イメージング方法
JPH0779949A (ja) * 1993-09-14 1995-03-28 Toshiba Corp 磁気共鳴映像装置
EP0685747A1 (fr) * 1994-05-31 1995-12-06 Shimadzu Corporation Procédé et appareil d'imagerie par résonance magnétique
US5565777A (en) * 1993-09-13 1996-10-15 Kabushiki Kaisha Toshiba Method/apparatus for NMR imaging using an imaging scheme sensitive to inhomogeneity and a scheme insensitive to inhomogeneity in a single imaging step
EP0745865A1 (fr) * 1995-06-02 1996-12-04 Picker International, Inc. Une méthode et appareil pour l'imagerie par résonance magnétique

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5270654A (en) * 1991-07-05 1993-12-14 Feinberg David A Ultra-fast multi-section MRI using gradient and spin echo (grase) imaging
DE69418404T2 (de) * 1993-09-16 1999-11-11 Koninkl Philips Electronics Nv Korrektur der Polarität des Auslesegradienten in Bilderzeugung durch EPI und GRASE magnetische Resonanz
US5680045A (en) * 1995-07-20 1997-10-21 Feinberg David A Grase-type MR pulse sequences
DE19720438A1 (de) * 1997-05-15 1998-11-19 Max Planck Gesellschaft Verfahren und Vorrichtung zur Gewinnung von Daten für Magnetresonanz-Bildgebung

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4709212A (en) * 1986-01-03 1987-11-24 General Electric Company Method of enhancing image signal-to-noise ratio by combining NMR images of differing pulse sequence timing
JPH0282942A (ja) * 1988-09-20 1990-03-23 Toshiba Corp 磁気共鳴イメージング方法
US4896113A (en) * 1988-11-25 1990-01-23 General Electric Company Use of repeated gradient echoes for noise reduction and improved NMR imaging
US5565777A (en) * 1993-09-13 1996-10-15 Kabushiki Kaisha Toshiba Method/apparatus for NMR imaging using an imaging scheme sensitive to inhomogeneity and a scheme insensitive to inhomogeneity in a single imaging step
JPH0779949A (ja) * 1993-09-14 1995-03-28 Toshiba Corp 磁気共鳴映像装置
EP0685747A1 (fr) * 1994-05-31 1995-12-06 Shimadzu Corporation Procédé et appareil d'imagerie par résonance magnétique
EP0745865A1 (fr) * 1995-06-02 1996-12-04 Picker International, Inc. Une méthode et appareil pour l'imagerie par résonance magnétique

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 014, no. 275 (C - 0728) 14 June 1990 (1990-06-14) *
PATENT ABSTRACTS OF JAPAN vol. 1995, no. 06 31 July 1995 (1995-07-31) *

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