WO2003037183A1 - Dispositif d'imagerie par resonance magnetique - Google Patents

Dispositif d'imagerie par resonance magnetique Download PDF

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Publication number
WO2003037183A1
WO2003037183A1 PCT/JP2002/009631 JP0209631W WO03037183A1 WO 2003037183 A1 WO2003037183 A1 WO 2003037183A1 JP 0209631 W JP0209631 W JP 0209631W WO 03037183 A1 WO03037183 A1 WO 03037183A1
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Prior art keywords
magnetic field
pulse
gradient magnetic
gradient
slice
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PCT/JP2002/009631
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English (en)
Japanese (ja)
Inventor
Yoshinori Togasawa
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Hitachi Medical Corporation
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Priority to JP2003539531A priority Critical patent/JP4319035B2/ja
Publication of WO2003037183A1 publication Critical patent/WO2003037183A1/fr

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    • 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
    • G01R33/565—Correction of image distortions, e.g. due to magnetic field inhomogeneities
    • G01R33/56518—Correction of image distortions, e.g. due to magnetic field inhomogeneities due to eddy currents, e.g. caused by switching of the gradient magnetic field
    • 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]

Definitions

  • the present invention relates to a magnetic resonance imaging apparatus (hereinafter, referred to as an MRI apparatus) for imaging nuclear distribution and spectrum information in a subject by utilizing a nuclear magnetic resonance phenomenon.
  • an MRI apparatus magnetic resonance imaging apparatus
  • a multi-shot based on the Carr-Purcel l-Meiboom-Gill (CPMG) method was used to reduce the eddy currents and artifacts generated by the residual gradient magnetic field due to the influence of the gradient magnetic field for the previous shot or slice measurement.
  • the present invention relates to an improvement of an MRI apparatus having a single-slice slice and a multi-shot multi-slice imaging pulse sequence. Background technology
  • An MRI apparatus applies a high-frequency magnetic field to a subject placed in a uniform static magnetic field, causing nuclear magnetic resonance to occur in nuclei (usually protons) existing in an arbitrary region of the subject, thereby generating the nuclear magnetic resonance.
  • the tomographic image of the area is obtained from the nuclear magnetic resonance signal (echo signal).
  • an MRI apparatus applies a slice gradient magnetic field that specifies a plane on which a tomographic image of a subject is to be obtained, and simultaneously applies an excitation pulse (high-frequency pulse) that excites spins in the plane, and is excited by this. Obtain the echo signal generated when the spin converges.
  • a phase encoding gradient magnetic field and a readout (frequency encoding) gradient magnetic field are applied in directions orthogonal to each other in the tomographic plane during the period from excitation to obtaining the echo signal.
  • the echoes thus obtained are arranged in k-space with the phase encoding direction as the ordinate and the readout direction as the abscissa, and an image is reconstructed by performing an inverse Fourier transform on the data arranged in the k-space.
  • a high-frequency pulse for generating an echo signal and each gradient magnetic field are applied based on a preset pulse sequence.
  • Various pulse sequences are known according to the purpose of imaging.
  • the fast spin echo method 180 ° inversion pulses equal to the number of set echo numbers are applied after the 90 ° excitation pulse, and at that time, echo signals are collected by giving a different phase encoding amount for each echo number. It is a high-speed imaging method that acquires multiple echo signals with a short repetition time (TR).
  • Fig. 5A shows the pulse sequence by the fast spin echo method based on the CPMG method
  • Fig. 5B shows the behavior of the spin due to it.
  • the high-frequency pulse and the frequency code ( Readout) Only the gradient magnetic field in the direction is shown.
  • a 90 ° excitation pulse 51 by applying a 90 ° excitation pulse 51, a specific spin tilted to the x′-y ′ plane is rotated from the position 1 to 2 by the gradient magnetic field 53.
  • the amount of phase rotation at this time is defined as Next, the position is changed from 2 to 3 by the 180 ° inversion pulse 52, and further moved from 3 to 4 by the gradient magnetic field 54.
  • the gradient magnetic field 53 and the gradient magnetic field 54 have an applied intensity X application time of 1: 2, and thus the phase rotation amount at this time is 2.
  • the same repetition occurs at the position of 5 to 6 by the next inversion pulse 52 and gradient magnetic field 54, but when the first 1: 2 relationship is broken, multiple echo signals are generated.
  • spin rotation errors occur in the spins and accumulate, causing signal loss and the like, and artifacts occur.
  • Japanese Patent Application Laid-Open No. H11-89817 discloses a magnetic detection method that generates a correction magnetic field waveform for correcting a gradient field distortion due to eddy current. It has been proposed to introduce a digital eddy current correction circuit including a circuit.
  • Eddy current correction by adding a hardware circuit as described above is extremely effective in correcting gradient magnetic field distortion due to eddy currents with little fluctuation, but fluctuations occur in pulse sequences with different conditions such as the number of slices and repetition time. It is not possible to deal with the residual magnetic field.
  • a plurality of slices three in this case, S1 to S3 are measured adjacent or very close within a given repetition time TR
  • Imaging is repeated by equally distributing the time for each slice.
  • the time interval between slices (the time from the end of measurement of one slice to the measurement of the next slice) is not always the same, so that a certain time due to eddy currents generated in the magnet's conductive members, etc.
  • the gradient magnetic field error component that attenuates with a constant is different for each slice, and this error component affects the slice to be measured next, so that the spin is affected by a different phase error for each slice.
  • the residual gradient magnetic field component due to the magnetic hysteresis will also be different if the time interval between each slice is different. Therefore, the resulting phase error component of the spin which differs for each slice cannot be completely removed by the zero-order or first-order phase error correction. Therefore, it was difficult to remove the artifacts caused by these phase errors, especially in a multi-shot multi-slice using the fast spin echo method based on the CPMG method that requires the accuracy of the spin phase.
  • an object of the present invention is to provide a gradient magnetic field applied at the time of the immediately preceding shot or slice measurement in an MRI apparatus having an imaging function using a multi-shot single slice and a multi-shot multi-slice pulse sequence based on the CPMG method.
  • the gradient magnetic field error component that fluctuates for each shot or slice due to eddy current or residual magnetic field due to The purpose is to suppress the artifacts caused by the phase rotation error of the spins generated for each shot or slice. Disclosure of the invention
  • the present invention provides an MRI apparatus having an imaging function based on a multi-slice method pulse sequence, in which a different residual gradient magnetic field component for each slice, which is mixed in a slice measurement to be measured next from a slice measurement completed immediately before, is used for each slice measurement.
  • a predetermined amount of gradient magnetic field pre-pulse is applied prior to application of the excitation pulse in each slice measurement so that the same value is applied when the excitation pulse (first high-frequency magnetic field pulse) is applied.
  • the residual component of the gradient magnetic field pre-pulse is canceled by the time of applying the second high frequency magnetic field pulse after the excitation.
  • a gradient magnetic field component is applied.
  • the imperfections of the gradient magnetic field applied in the immediately preceding shot or slice measurement at the time of applying the 90 ° excitation high-frequency pulse for spin excitation can be obtained by adding a gradient magnetic field pre-pulse.
  • the error component due to the gradient magnetic field is substantially nullified. Only the known and constant gradient magnetic field error component due to the gradient magnetic field pre-pulse can be artificially introduced.
  • the phase rotation error component that is uniform over each shot or slice of the spin caused by such a constant residual gradient magnetic field error component that does not fluctuate can be easily removed by zero-order or first-order correction, and the Can be controlled.
  • the gradient magnetic field pre-pulse is applied a predetermined time before the application of the 90 ° excitation high-frequency magnetic field pulse.
  • the MRI apparatus of the present invention is suitable for an MRI apparatus having a multi-shot multi-slice type pulse sequence based on the CPMG method. That is, in a preferred embodiment of the present invention, the 90 ° excitation high-frequency magnetic field pulse and the 180 ° inverted high-frequency magnetic field pulse are applied such that their applied axes are orthogonal to each other in the rotating coordinate system.
  • FIG. 1 is a diagram showing an overall outline of an MRI apparatus to which the present invention is applied.
  • FIG. 2 is a diagram showing an imaging sequence by the high-speed spin echo method based on the CPMG method provided in the MRI apparatus of the present invention.
  • Figure 3 illustrates the incompleteness of the gradient magnetic field due to eddy currents.
  • FIG. 4 is a diagram illustrating a residual gradient magnetic field due to magnetic hysteresis.
  • FIG. 5A is a diagram illustrating a conventional high-speed spin echo method based on the CPMG method.
  • FIG. 5B is a diagram for explaining the behavior of the spin in the sequence of FIG. 5A.
  • FIG. 6 is a diagram for explaining a change in a gradient magnetic field error component in multi-slice imaging.
  • FIG. 1 is a block diagram showing the overall configuration of an MRI device to which the present invention is applied.
  • This MRI apparatus mainly includes a static magnetic field generating magnet 2 for generating a uniform static magnetic field in a space where the subject 1 is placed, a gradient magnetic field generating system 3 for applying a magnetic field gradient to the static magnetic field, and a tissue of the subject 1.
  • a transmission system 5 that generates a high-frequency magnetic field that causes nuclear magnetic resonance in the nuclei (usually, protons) of the atoms that make up the target, a reception system 6 that receives an echo signal generated from the subject 1 by nuclear magnetic resonance,
  • the signal processing system 7 processes the echo signal received by the receiving system 6 and creates an image representing the spatial density and spectrum of the nucleus.
  • the signal processing system 7 performs various operations and controls the entire device.
  • a central processing unit (CPU) 8 is provided.
  • the static magnetic field generating magnet 2 is composed of a permanent magnet, a normal conducting type or a superconducting type magnet, and generates a uniform static magnetic field around the subject 1 in the body axis direction or in a direction orthogonal to the body axis.
  • the gradient magnetic field generation system 3 includes a gradient magnetic field coil 9 wound in three directions of x, y, and z, and a gradient magnetic field power supply 10 for driving each gradient magnetic field coil. Drives the gradient power supply 10 for each coil according to Thereby, gradient magnetic fields Gx, Gy, Gz in the three axes of x, y, z are applied to the subject 1.
  • an imaging target region (slice, slab) of the subject 1 can be set, and position information such as phase encoding and frequency encoding can be added to the echo signal.
  • the triaxial gradient magnetic fields Gx, Gy, and Gz can be any of the slice gradient magnetic field Gs, the phase encode gradient magnetic field Gp, and the frequency encode gradient magnetic field Gf according to the set cross section of the MRI apparatus. Can correspond.
  • the transmission system 5 irradiates a high-frequency magnetic field to cause nuclear magnetic resonance in the nuclei of the atoms constituting the biological tissue of the subject 1 by the high-frequency pulse sent from the sequencer 4, and includes a high-frequency oscillator 11; It comprises a modulator 12, a high-frequency amplifier 13, and a high-frequency coil 14a on the transmission side.
  • the high-frequency pulse output from the high-frequency oscillator 11 is amplitude-modulated by the modulator 12, and the amplitude-modulated high-frequency pulse is amplified by the high-frequency amplifier 13 and then placed close to the subject 1.
  • the subject 1 is irradiated with a high-frequency magnetic field (electromagnetic wave) by supplying it to the high-frequency coil 14a.
  • the receiving system 6 detects an echo signal (NMR signal) emitted from the subject 1 by nuclear magnetic resonance, and includes a high-frequency coil 14b on the receiving side, an amplifier 15, a quadrature phase detector 16, A / D converter 17.
  • the echo signal detected by the high-frequency coil 14b is input to the A / D converter 17 via the amplifier 15 and the quadrature detector 16 to convert the echo signal into a digital signal. And sent to the signal processing system 7 as two series of collected data.
  • the signal processing system 7 includes a CFU 8, a recording device 18 such as a magnetic disk and a magnetic tape, and a display 19 such as a CRT.
  • the CPU 8 performs processing such as Fourier transform, correction coefficient calculation, and image reconstruction operation. The obtained image and image are displayed on the display 19. Further, the CPU 8 sends various commands necessary for data collection of tomographic images of the subject 1 to the gradient magnetic field generation system 3, the transmission system 5, and the reception system 6 via the sequencer 4.
  • the sequencer 4 generates a gradient magnetic field so as to collect data necessary for image reconstruction according to a pulse sequence which is a time chart of a predetermined control determined by an imaging method. Controls raw 3, transmitting 5 and receiving 6.
  • the pulse sequence includes a pulse sequence based on the CPMG method, for example, a pulse sequence based on the high-speed spin echo method. Such a pulse sequence is incorporated in the CPU 8 as a program.
  • FIG. 2 is a diagram showing a pulse sequence for one slice in the whole pulse sequence by the multi-shot multi-slice type fast spin echo method shown in FIG.
  • a gradient magnetic field 25 to 27 as a pre-pulse is added to the pulse sequence based on the conventional high-speed spin echo method based on the CPMG method, and the subsequent pulse trains are almost the same as the conventional pulse sequence.
  • a 90 ° excitation pulse 21 is applied simultaneously with the first slice selection gradient magnetic field 20 for selecting a predetermined cross section to excite spins in the cross section .
  • a plurality of 180 ° inversion pulses 22 are sequentially applied simultaneously with the slice selection gradient magnetic field 20 to generate an echo signal.
  • a phase encoding gradient magnetic field 23, 23 ' having a different polarity and strength is applied to give a different amount of phase encoding to each echo signal, and a gradient magnetic field 24 in the frequency direction is applied to generate an echo signal. measure.
  • a dephasing gradient magnetic field 24 ' is applied prior to the generation of the echo signal.
  • the illustrated pulse sequence is based on the CPMG method.
  • the applied axis y ′ of the 180 ° inversion pulse 22 is orthogonal to the applied axis x ′ of the 90 ° excitation pulse 21 and the 180 ° inverted pulse.
  • the application interval is set to be exactly twice the interval between the 90 ° excitation pulse and the first 180 ° inversion pulse.
  • the pulse sequence of the high-speed spin echo method based on the CPMG method is repeatedly executed by setting a plurality of slices within the repetition time TR to acquire the necessary number of echo signals to reconstruct an image for each slice You.
  • Prepulse gradient applied before the 90 ° excitation pulse in the pulse sequence Nos. 25 to 27 give a constant gradient magnetic field error component which does not fluctuate when a 90 ° excitation pulse is applied.
  • the induced phase error of the spin is made constant, ie, a phase error that can be subsequently removed by zero-order and first-order correction.
  • FIG. Figure 3 is a diagram showing a case where the gradient magnetic field has imperfections due to eddy currents.
  • the time from the application of the prepulse gradient magnetic field 25 to the application of the 90 ° excitation pulse 21 is made constant in the pulse sequence for each slice, so that the residual gradient magnetic field of the prepulse 25 becomes 90 °
  • the amount of phase rotation given to the excited spin ( ⁇ can always be set to the 0th and ⁇ 1st order correctable constant value iS later.
  • Such a constant phase rotation amount] 8 In the case of a slice gradient magnetic field, by adjusting the intensity of the refresh gradient magnetic field 20 ′ applied immediately after the 90 ° excitation pulse, the correction can be made so as to maintain the CPMG effect.
  • the error component due to the residual gradient magnetic field can be kept constant by keeping the time from the application of the pre-pulse gradient magnetic field to the application of the 90 ° excitation pulse constant. Is also removed by correction in the same manner as above. You can leave.
  • the pre-pulse is for keeping the residual gradient magnetic field constant, its intensity does not require a strong gradient magnetic field intensity such as a spoil gradient magnetic field, and the gradient applied in the pulse sequence is not required. It is sufficient to use the same strength and application time as the magnetic field.
  • the intensity of the slice selection gradient magnetic field changes depending on the set slice thickness, so that the phase error component in the slice direction is inversely proportional to the slice thickness. Become a relationship. Therefore, it is preferable to change the applied intensity of the prepulse gradient magnetic field 25 in inverse proportion to the slice thickness. As a result, a linear phase error component can be generated with respect to the applied intensity of the slice selection gradient magnetic field. Therefore, the rephase gradient magnetic field immediately after the first slice selection gradient magnetic field 20 can be easily added or subtracted at the time of application. Can be corrected.
  • the applied intensity and application time of the pre-pulse 27 are set to be the same as the applied intensity and application time of the phase gradient magnetic field 24 ', and the application of the 90 ° excitation pulse 21 is repeated.
  • the amount of application of the phase gradient magnetic field 24 ' is adjusted in order to correct the phase rotation of the spin due to the residual gradient magnetic field due to the prepulse 27 applied to the spins before the start of the application of the phase gradient magnetic field 24'.
  • the applied amount of the phase gradient magnetic field 24 ' is adjusted, the applied amount of the read gradient magnetic field 24 applied thereafter must be changed accordingly.
  • phase encoding direction in order to prevent the accumulation of the amount of phase rotation, it is preferable to use bipolar pre-pulses 26 and 26 'which are applied with close timing as shown in the figure. Further, it is preferable that the intensity of the pre-pulse in the phase encoding direction is changed depending on the number of phase encodings. That is, in the pulse sequence by the high-speed spin echo method, the intensity of the phase encoding gradient magnetic field 23, 23 'changes at each repetition. The pre-pulses 26 and 26 are applied in the same manner as the applied intensity and application time of the phase-encoding gradient magnetic field applied at the beginning of this repetition.
  • phase rotation error canceling gradient magnetic field pulse 26 By applying the phase rotation error canceling gradient magnetic field pulse 26 "to correct the phase rotation of the spin due to the residual gradient magnetic field due to the pre-pulses 26, 26 applied to the spin later, as in the case of the gradient magnetic field in other directions, Correction can be performed and the CPMG effect is maintained.
  • image reconstruction using echo signals acquired by repeating the pulse sequence to which the pre-pulse is applied is the same as that of a conventional MRI apparatus.
  • the resulting image is an image in which the artifact caused by the imperfect gradient magnetic field is suppressed.
  • FIG. 2 shows a case in which pre-pulses 25 to 27 are applied in three directions, ie, a slice direction, a phase encoder direction, and a frequency direction.
  • the effect can be obtained by performing at least one in one direction.
  • FIG. 2 shows the case of sequential ordering as the measurement order in the k-space, but the measurement order can be arbitrary.
  • Fig. 2 shows an imaging method using the fast spin echo method as a pulse sequence based on the CPMG method.
  • a sequence of a 90 ° excitation pulse and a plurality of 180 ° inversion pulses is repeated several times and multiple It can be applied as long as it is an imaging method that measures the echo of an object.
  • a gradient echo and spin echo imaging method in which a gradient magnetic field in the frequency direction is repeatedly inverted and a plurality of echo signals are measured after applying a 180 ° inversion pulse ( GRASE) can also be applied.
  • GRASE 180 ° inversion pulse
  • the gradient magnetic field error component that fluctuates according to the set TR, the number of multi-slices, and the like, and the phase error of the spin due to the gradient magnetic field error component. Reduce the impact Artifacts due to phase errors can be effectively suppressed.
  • an MRI apparatus having a multi-shot single slice and a multi-shot multi-slice pulse sequence that requires high speed and high image quality based on the CPMG method according to the present invention is useful as a medical image diagnostic apparatus. .

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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)
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  • Magnetic Resonance Imaging Apparatus (AREA)

Abstract

L'invention concerne un dispositif IRM comportant une séquence d'impulsions d'imagerie permettant de mesurer des signaux d'écho, par l'application d'une impulsion d'excitation de 90° (21) et d'une impulsion (22) de champ magnétique haute fréquence de 180° inversée, une pluralité de fois. Lors de la réalisation de cette séquence d'impulsions, des préimpulsions (25-27) permettent de maintenir constante l'entrée de composant d'erreur de champ magnétique à gradient lors de la mesure de tranche immédiatement précédente, avant l'application de l'impulsion d'excitation de 90° (21), et sont appliquées pendant une durée prédéterminée avant l'application de l'impulsion d'excitation de 90° (21). De cette manière, le composant d'erreur de champ magnétique à gradient de fluctuation, provoqué par le champ magnétique à gradient appliqué lors de la mesure de tranche immédiatement précédente est rendu inefficace, et le composant de champ magnétique à gradient résiduel, lors de l'application de l'impulsion d'excitation de 90° (21) est toujours maintenu uniforme, transformant ainsi l'erreur de rotation de phase tournante provoquée ultérieurement en un composant d'erreur constant pouvant être éliminé par une correction ultérieure. Ainsi, l'invention concerne un dispositif IRM par un procédé d'imagerie faisant appel à un train d'impulsions par le biais d'un procédé CPMG, à partir duquel le composé d'erreur de champ magnétique à gradient variant en fonction de la condition de l'imagerie et de l'influence de l'erreur de phase tournante provoquée par le composant d'erreur est éliminé, ce qui permet de créer une image pour laquelle l'artefact dû à l'erreur de phase tournante est supprimé.
PCT/JP2002/009631 2001-10-30 2002-09-19 Dispositif d'imagerie par resonance magnetique WO2003037183A1 (fr)

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Cited By (5)

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JP2006262928A (ja) * 2005-03-22 2006-10-05 Hitachi Medical Corp 磁気共鳴イメージング装置
JP2008307303A (ja) * 2007-06-18 2008-12-25 Hitachi Medical Corp 磁気共鳴イメージング装置
JP2010142354A (ja) * 2008-12-17 2010-07-01 Toshiba Corp 磁気共鳴イメージング装置
JP2011036455A (ja) * 2009-08-12 2011-02-24 Hitachi Medical Corp 磁気共鳴イメージング装置
JP5438024B2 (ja) * 2008-11-07 2014-03-12 株式会社日立メディコ 磁気共鳴イメージング装置及び方法

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* Cited by examiner, † Cited by third party
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US11826134B2 (en) * 2019-06-13 2023-11-28 University Of Southern California Method for measuring water exchange across the blood-brain barrier using MRI

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EP1126286A1 (fr) * 2000-01-03 2001-08-22 Ge Yokogawa Medical Systems, Ltd. Compensation de l'influence de courants de Foucault et de magnétisation résiduelle dans l'imagerie par résonance magnétique à échos de spin rapides

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JPH02144039A (ja) * 1988-11-28 1990-06-01 Shimadzu Corp Ｍｒｉ装置の傾斜磁場印加方法
JPH06261877A (ja) * 1992-10-26 1994-09-20 Philips Electron Nv 磁気共鳴画像化における渦電流補償
JPH07163544A (ja) * 1993-07-15 1995-06-27 General Electric Co <Ge> Ｍｒｉシステムでのプレスキャン
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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006262928A (ja) * 2005-03-22 2006-10-05 Hitachi Medical Corp 磁気共鳴イメージング装置
JP4566039B2 (ja) * 2005-03-22 2010-10-20 株式会社日立メディコ 磁気共鳴イメージング装置
JP2008307303A (ja) * 2007-06-18 2008-12-25 Hitachi Medical Corp 磁気共鳴イメージング装置
JP5438024B2 (ja) * 2008-11-07 2014-03-12 株式会社日立メディコ 磁気共鳴イメージング装置及び方法
JP2010142354A (ja) * 2008-12-17 2010-07-01 Toshiba Corp 磁気共鳴イメージング装置
US8487614B2 (en) 2008-12-17 2013-07-16 Kabushiki Kaisha Toshiba Magnetic resonance imaging apparatus/method counter-actively suppressing remnant eddy current magnetic fields generated from gradients applied before controlling contrast pre-pulses and MRI image data acquisition
JP2011036455A (ja) * 2009-08-12 2011-02-24 Hitachi Medical Corp 磁気共鳴イメージング装置

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