WO2005102162A1 - Appareil d'imagerie à résonance magnétique et méthode - Google Patents

Appareil d'imagerie à résonance magnétique et méthode Download PDF

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Publication number
WO2005102162A1
WO2005102162A1 PCT/JP2005/007955 JP2005007955W WO2005102162A1 WO 2005102162 A1 WO2005102162 A1 WO 2005102162A1 JP 2005007955 W JP2005007955 W JP 2005007955W WO 2005102162 A1 WO2005102162 A1 WO 2005102162A1
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pulse
magnetic resonance
sequence
resonance imaging
subject
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PCT/JP2005/007955
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English (en)
Japanese (ja)
Inventor
Hiroyuki Itagaki
Tomohiro Goto
Tetsuhiko Takahashi
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Hitachi Medical Corporation
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Priority to JP2006512648A priority Critical patent/JPWO2005102162A1/ja
Publication of WO2005102162A1 publication Critical patent/WO2005102162A1/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
    • G01R33/563—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution of moving material, e.g. flow contrast angiography
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves 
    • A61B5/055—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves  involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/316—Modalities, i.e. specific diagnostic methods
    • A61B5/318—Heart-related electrical modalities, e.g. electrocardiography [ECG]
    • A61B5/346—Analysis of electrocardiograms
    • A61B5/349—Detecting specific parameters of the electrocardiograph cycle
    • A61B5/352—Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7271—Specific aspects of physiological measurement analysis
    • A61B5/7285—Specific aspects of physiological measurement analysis for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal

Definitions

  • the present invention relates to a magnetic resonance imaging (hereinafter, referred to as MRI) apparatus and method, and more particularly to a delayed contrast imaging method of a myocardium or the like using a diaphragm navigation technique (hereinafter, referred to as diaphragm navigation).
  • MRI magnetic resonance imaging
  • diaphragm navigation a diaphragm navigation technique
  • NMR nuclear magnetic resonance
  • One of the preferable imaging methods of the myocardium in MRI is a delayed contrast imaging method.
  • This is an imaging technique that utilizes the property of a contrast agent such as Gd-DTPA to aggregate in necrotic or infarcted myocardium.
  • a predetermined time for example, 15 minutes
  • an inversion recovery image irradiation of an IR pulse followed by acquisition of an NMR signal by a gradient echo method, etc.
  • Enhanced image irradiation of an IR pulse followed by acquisition of an NMR signal by a gradient echo method, etc.
  • the myocardium in the necrotic or infarcted state is depicted with a higher signal than the normal myocardium (for example, see Non-Patent Document 1).
  • Non-Patent Document 1 Radiology 2001; 218: 215-223
  • a diaphragm navigation as an effective method for reducing an artifact based on a respiratory movement of a subject appearing on an image.
  • two cross sections that intersect at the position of the diaphragm are separately excited by a high frequency magnetic field pulse (Radio Frequency pulse or RF pulse) such as a 90 ° pulse and a 180 ° pulse.
  • An NMR signal (hereinafter referred to as a navi echo signal) generated from the superimposed region of the cross section is acquired, and the position of the diaphragm is detected based on the NMR signal.
  • an image is created using only NMR signals obtained by an imaging sequence executed when the position of the diaphragm is within a predetermined range.
  • Patent Document 1 US Pat. No. 4,937,526
  • the above-mentioned conventional technique does not disclose the technique for performing the delayed contrast imaging of the myocardium described in Non-Patent Document 1 in combination with the diaphragm navigation described in Patent Document 1; The technology regarding the order in which the sequence for the execution is executed is disclosed.
  • An object of the present invention is to provide a magnetic resonance imaging that optimizes a procedure for applying a magnetic field and the like in a delayed contrast imaging method of a cardiac muscle or the like using a diaphragm navigation technology (hereinafter, referred to as a diaphragm navigation). It is to provide an apparatus and a method.
  • a magnetic resonance imaging apparatus of the present invention emphasizes a difference between a body motion monitor sequence for obtaining body motion information of a subject and a longitudinal relaxation time due to the tissue of the subject.
  • the present invention is characterized in that a means for executing an imaging sequence for obtaining a magnetic resonance image in this order is provided.
  • the body motion information obtained by the body motion monitoring sequence becomes more accurate.
  • the imaging sequence is first performed in order to obtain a magnetic resonance image. It is characterized by applying a short pulse.
  • the body movement The two-step sequence and the imaging sequence are performed at a predetermined phase timing of a periodically moving portion in the subject.
  • the body motion motor sequence includes a first RF pulse application, a second RF pulse applied next, and Exciting the two slice areas in the intersecting direction by the slice selection gradient magnetic field applied along with them, and then detecting the echo signal generated from the overlapping portion of the two slice areas.
  • body motion information of the subject is obtained.
  • the body movement monitoring sequence is more specifically performed.
  • the magnetic resonance imaging apparatus further comprises means for applying the first RF pulse and the second RF pulse with different phases. I have.
  • the echo signal is generated.
  • the magnetic resonance imaging apparatus includes means for applying the flip angle of the second RF pulse as twice the flip angle of the first RF pulse. As a feature! / Puru.
  • the magnetic resonance imaging apparatus further comprises means for applying the flip angle of the first RF pulse to be smaller than 60 °.
  • a desired region of the subject can be imaged with good contrast.
  • the first RF pulse and the second RF pulse are used during the execution of the body movement monitoring sequence and the imaging sequence.
  • the method is characterized in that a third RF pulse and a fourth RF pulse for canceling the excited magnetization are applied.
  • a desired region of the subject can be imaged with good contrast.
  • the time from when the body movement monitoring sequence is executed to obtain an echo signal to execute the pressurization sequence is set. It is characterized by having means for adjusting.
  • a desired region of the subject can be imaged with good contrast.
  • the embodiment is characterized in that the pressurization pulse is an IR pulse having a flip angle of 180 °.
  • a desired region of the subject can be imaged with good contrast.
  • the body movement monitoring sequence and the imaging sequence are used to detect a movement of a periodically moving portion in the subject. It is performed between adjacent timings when the signal strength is greater than a predetermined strength.
  • the body movement monitor sequence is characterized by detecting movement of a diaphragm or the like due to respiration of the subject.
  • the magnetic resonance imaging apparatus is used in combination with a means for administering a contrast agent to the subject prior to execution of each of the sequences.
  • a T1-weighted image of the subject can be obtained by the imaging sequence.
  • the imaging sequence generates a plurality of NMR signals, and the plurality of NMR signals are respectively provided. It is characterized in that measurement is performed with different phase encodings applied.
  • the body movement monitoring sequence and the execution of the imaging sequence are repeated over a plurality of movement periods of the periodically moving portion, whereby, NMR signals required for image reconstruction of the magnetic resonance image are acquired as a set.
  • the above object can also be solved by a magnetic resonance imaging method.
  • the magnetic resonance imaging method of the present invention provides a body movement monitoring sequence for obtaining body movement information of a subject, and a tissue of the subject.
  • a characteristic feature is that an imaging sequence for obtaining a magnetic resonance image by emphasizing a difference in longitudinal relaxation time due to the above is executed in this order.
  • the magnetic resonance imaging method of the present invention in order to obtain a magnetic resonance image by emphasizing the difference in the longitudinal relaxation time due to the tissue of the subject, Is characterized by applying a presaturation pulse first.
  • the body movement monitor sequence and the imaging sequence may include a predetermined portion of the body that moves periodically within the subject. It is characterized by being executed at the timing of the phase.
  • the body motion motor sequence includes the application of a first RF pulse and the application of a second RF pulse subsequent thereto. And a gradient magnetic field for slice selection applied along with the excitation of the two slice areas in the intersecting direction, and thereafter, an echo signal generated from an overlapping portion of the two slice areas is detected. By doing so, body motion information of the subject is obtained. Thus, the body movement monitoring sequence is more specifically performed.
  • the phases of the first RF pulse and the second RF pulse are applied with a phase difference of 180 °, and the second RF pulse is further applied.
  • the flip angle of the first RF pulse is applied as twice the flip angle of the first RF pulse, and the flip angle of the first RF pulse is smaller than 60 °.
  • the first RF pulse and the second RF pulse are provided between the execution of the body movement monitoring sequence and the imaging sequence. Applying a third RF pulse and a fourth RF pulse for canceling the magnetization excited by the pulse.
  • a desired region of the subject can be imaged with good contrast.
  • a contrast agent is administered to the subject prior to execution of the sequence.
  • a T1-weighted image of the subject can be obtained by the imaging sequence.
  • An object of the present invention is to provide a magnetic resonance imaging method that optimizes a procedure for applying a magnetic field and the like in a delayed contrast imaging method of a myocardium or the like using a diaphragm navigation technology (hereinafter, referred to as a diaphragm navigation). It is to provide an apparatus and a method.
  • FIG. 1 is a block diagram illustrating an overall configuration of an MRI apparatus according to an embodiment of the present invention.
  • this MRI apparatus mainly includes a static magnetic field generation system 1, a gradient magnetic field generation system 2, a transmission system 3, a reception system 4, a signal processing system 5, and a control system (sequencer 6 and CPU 7). It has.
  • the static magnetic field generation system 1 generates a uniform static magnetic field in a space (imaging space) around the subject 9, and has a magnet device such as a permanent magnet system, a normal conduction system, or a superconducting system. Also, the direction of the static magnetic field is usually the direction of the body axis of the subject or a direction orthogonal thereto.
  • the gradient magnetic field generation system 2 includes three gradient magnetic field coils 10 that generate gradient magnetic field pulses in these three axial directions, for example, when the direction of the static magnetic field is the Z direction, and the two directions orthogonal thereto are X and Y. And a gradient power supply 11 for driving them.
  • a gradient magnetic field pulse can be generated in the three axes of X, Y, and ⁇ ⁇ ⁇ ⁇ or in a direction in which these are combined.
  • the gradient magnetic field pulse is applied to give position information to the NMR signal generated from the subject 9.
  • the transmission system 3 includes a high-frequency oscillator 12, a modulator 13, a high-frequency amplifier 14, and a high-frequency magnetic field irradiation coil 15 for transmission.
  • a high frequency magnetic field pulse (hereinafter referred to as an RF pulse) generated by a high frequency oscillator 12 is modulated into a signal having a predetermined envelope by a modulator 13, then amplified by a high frequency amplifier 14 and applied to a high frequency magnetic field irradiation coil 15.
  • the subject is irradiated with an electromagnetic wave (high-frequency signal) that causes nuclear nuclei of atoms constituting the subject to undergo nuclear magnetic resonance.
  • the high-frequency magnetic field irradiation coil 15 is usually arranged close to the subject.
  • the receiving system 4 includes a receiving high-frequency receiving coil 16, an amplifier 17, a quadrature phase detector 18, and an A / D converter 19.
  • the transmitting high-frequency magnetic field irradiating coil 15 The NMR signal generated by the subject in response to the electromagnetic wave irradiated with the force is detected by the high-frequency receiving coil 16 for receiving, amplified by the amplifier 17, and then passed through the quadrature phase detector.
  • the signal is converted into a digital value by the A / D converter 19 via the signal 18 and sent to the signal processing system 5 as two series of collected data.
  • the signal processing system 5 is composed of the CPU 7, the storage device 20, and the operation unit 30.
  • the CPU 7 converts the digital signal received by the reception system 4 into various signals such as Fourier transform, correction coefficient calculation, and image reconstruction. Perform processing.
  • the storage device 20 includes a ROM 21, a RAM 22, an optical disk 23, a magnetic disk 24, and the like.For example, a program for performing image analysis processing and measurement over time and invariable parameters used in the execution of the program are used for the ROM 21. Measurement parameters and reception The echo signal detected by the system is stored in the RAM 22, and the reconstructed image data is stored in the optical disk 23 and the magnetic disk 24, respectively.
  • the operation unit 30 includes input means such as a trackball or a mouse 31, a keyboard 32, and the like, and a display 33 for displaying a GUI required for input and for displaying a processing result in the signal processing system 5, and the like. .
  • Information necessary for various processes and control performed by the CPU 7 is input via the operation unit 30.
  • the image obtained by the photographing is displayed on the display 33.
  • the control system also includes the CPU 7 and the sequencer 6, and controls the operations of the gradient magnetic field generation system 2, the transmission system 3, the reception system 4, and the signal processing system 5 described above.
  • the application timing and applied intensity of the gradient magnetic field pulse and the RF pulse generated by the gradient magnetic field generation system 2 and the transmission system 3 and the timing of the acquisition of the echo signal by the reception system 4 are determined by the imaging method described in detail in the following embodiments. , Controlled by the sequencer 6.
  • the delayed contrast imaging with diaphragm navigation is to obtain an IR image of the myocardium etc. in equilibrium after a predetermined time has elapsed from the administration of the contrast agent while detecting the respiratory movement of the subject in the diaphragm navigation echo sequence.
  • the imaging sequence for obtaining an IR image includes the application of an IR pulse and the subsequent execution of a gradient echo method.
  • a contrast agent is administered to a subject prior to application of a magnetic field according to the sequence diagram shown below.
  • FIG. 2 41 is an electrocardiogram waveform
  • 42 is a line showing a diaphragm position
  • 43 is a sequence showing an imaging procedure using an MRI device
  • 44 is a power to adopt data obtained in an imaging sequence
  • 45 is an R wave in the electrocardiogram waveform
  • 46 is a gate window for identifying whether the position of the diaphragm is within a predetermined range.
  • TD indicates how much time has elapsed since the R-wave to start the gradient echo method in the force acquisition sequence to begin NMR signal acquisition, and TI
  • ⁇ ! ⁇ Indicates whether to apply an IR pulse in the imaging sequence before standing.
  • ⁇ This shows how far before the application of the IR pulse the diaphragm navigation sequence is performed.
  • Navi indicates the execution of a diaphragm navigation sequence
  • IR indicates the application of an IR pulse
  • Dara indicates the execution of the gradient echo method sequence shown in FIG.
  • NMR signals are acquired per heartbeat with different phase encodings, and this is repeated for 10 to 20 heartbeats to reconstruct one slice in about 15 seconds.
  • the NMR signals necessary to perform this are acquired as a set, and one slice is imaged.
  • the symbols indicated by adoption and discarding in 44 are symbols indicating whether the NMR signal obtained in the imaging sequence is to be discarded by force adopted for image generation.
  • the present inventors performed the diaphragm navigation sequence in two cases before the application of the IR pulse and after the end of the application of the IR pulse and before the start of the acquisition of the NMR signal by the gradient echo method.
  • the S / N of the navigation echo signal obtained by the sequence was compared experimentally. As a result, it was confirmed that the navi-echo signal acquired between the end of the application of the IR pulse and before the execution of the gradient echo method was inferior in S / N to the navi-echo signal acquired before the application of the IR pulse.
  • the reason for this is that if the Navi-Echo signal is acquired after the completion of the IR pulse application and before the acquisition of the NMR signal by the gradient echo method,
  • the diaphragm navigation sequence is executed before the application of the IR pulse. It was to so. More specifically, within one cycle of the electrocardiogram, a diaphragm navigation sequence is executed after the timing of the R wave at which the size of the electrocardiogram waveform is the largest, followed by the application of an IR pulse and the subsequent gradient echo. The shooting sequence by was executed. This has made it possible to acquire navigation echo signals with high S / N.
  • FIG. 4 47 indicates application of an RF pulse
  • 48 indicates a gradient magnetic field applied in the X direction
  • 49 indicates a gradient magnetic field applied in the Y direction
  • 50 indicates a gradient magnetic field applied in the Z direction
  • 51 indicates a gradient magnetic field applied in the Z direction. It is a line showing a state of generation of an NMR signal.
  • 1001 is the first RF pulse applied at the flip angle ⁇
  • 1002 is the second pulse applied ⁇ / 2 after the first RF pulse
  • the waveforms shown at 48, 49, and 50 are It shows how the gradient magnetic field in the X, ⁇ , and ⁇ directions is applied for the amplitude and the elapsed time
  • 1003 shows the generated MR signal.
  • the phases of the two applied RF pulses are made different. More specifically, the phase was shifted by 180 degrees between the two pulses. More specifically, the flip angle of the second RF pulse is set to twice the flip angle of the first RF pulse (hereinafter, the flip angle of the first RF pulse is ⁇ , the second RF pulse is ⁇ , Reduce the flip angle of the pulse by -2). By satisfying all of these conditions, the signal strength of the navigation echo signal could be maximized.
  • FIG. 5 (a) shows an image obtained by the delayed contrast imaging method, in which 61 regions, 63 are regions excited by both the first RF pulse 1001 and the second RF pulse 1002, and 64 are the first regions.
  • the region where neither the first RF pulse 1001 nor the second RF pulse 1002 is applied is shown.
  • a region 61 excited by the first RF pulse 1001 and a region 62 excited by the second RF pulse 1002 are parallel to, but intersect with, the direction of the body axis, and are partially illustrated. Contains no diaphragm.
  • Fig. 5 (b) shows the maximum signal area in the image obtained by the delayed contrast imaging method when the diaphragm navigation combined delay imaging method is performed by changing the value of the flip angle ⁇ of the RF pulse.
  • the upper row shows the flip angle ⁇ of the RF pulse applied in the diaphragm navigation sequence
  • the second row from the upper row shows which area of the area 62 and the infarcted myocardium has the maximum signal intensity in delayed contrast imaging.
  • the lower column shows the S / N of the navigation echo signal. Is a symbol that indicates whether it is high or moderate.
  • the flip angle was 30 or 45 degrees
  • the signal strength of the infarcted myocardium, which was the object of diagnosis increased
  • the navi echo signal also increased.
  • the flip angle was 90 °
  • the signal intensity in the region 62 was high, and it was not possible to obtain sufficient contrast between the infarcted myocardium and the normal myocardium for the purpose of diagnosis.
  • We analyzed the cause as follows.
  • the signal intensity of the infarcted myocardium which is the lesion, is maximized due to the effect of the contrast agent, and the value of the delayed contrast image is the infarcted myocardium whose signal intensity is the maximum.
  • image data when expressing image data as digital data, the range of image data (0 to the maximum value) is converted to the range of digital data (for example, 0 to 65535 when expressed in 16 bits), so that the maximum The value (in this case, the value of the infarcted myocardium) is normalized so as to correspond to the maximum value of the digital data.
  • the diaphragm navigation sequence when executed prior to the imaging sequence, and when the flip angle in the diaphragm navigation sequence is 90 degrees, according to the experiment performed by the present inventors, the diaphragm navigation sequence
  • the area 62 to which the RF pulse was applied was the high signal area in the delayed contrast image obtained by the imaging sequence.
  • the signal intensity of the liver, fat, and the like was maximized.
  • the signal intensity of the entire delayed contrast image is standardized by the region 62 where the signal intensity is maximum, and sufficient contrast is obtained between the infarcted myocardium and the normal myocardium, which need to be relatively contrasted for diagnosis. I can no longer get it!
  • FIG. 6 the leftmost column 71 is a column indicating in which region in FIG. 5 (a) the longitudinal magnetic field is to be considered, and the second column 72 from the left is the diaphragm navigation sequence.
  • the third column 73 from the left is a column indicating whether to apply the second RF pulse in the diaphragm navigation sequence.
  • the fourth column 74 is a column indicating whether or not to apply an IR pulse, and the rightmost column 75 is a column This is a column showing how the size of the longitudinal magnetism after applying the pulse is! /.
  • a mark indicates that each RF pulse or IR pulse is applied, and a mark indicates that each RF pulse is present! / ⁇ indicates that no IR pulse is applied.
  • regions 61 to 63 are regions where the RF pulse for the diaphragm navigation sequence is applied, and region 61 is where the first RF pulse 1001 of 90 ° and the IR pulse are applied.
  • Region 62 is the region where the second RF pulse 1002 at 180 ° and the IR pulse are applied, and region 63 is the first RF pulse 1001 at 90 ° and the second RF pulse at 180 °. This is the area where the pulse 1002 and the IR pulse are applied.
  • a region 64 is a region where an RF pulse required in the diaphragm navigation sequence is not applied and an IR pulse is applied.
  • the longitudinal magnetic field after the application of the IR pulse is the first RF pulse 1001 of 90 ° and the second RF pulse of 180 ° in the diaphragm navigation sequence in the regions 61 and 63.
  • the force region 62 which is almost zero, is restored by the excitation of the second RF pulse 1002 at 180 ° and the IR pulse in the diaphragm navigation sequence, It turned out that Mz was the same as the initial value of Gyi-Dani.
  • FIG. 7 is a graph showing how the size of the longitudinal magnetic field changes with time after the application of the IR pulse.
  • the horizontal axis represents the elapsed time from the end of the application of the IR pulse
  • the vertical axis represents the size of the longitudinal magnetic field, which is standardized by the initial value Mz of the vertical magnetic field.
  • the graph shows how the longitudinal magnetization of the region 61, the region 62, the region 63, and the region 64 changes.
  • the symbol “ ⁇ ” indicates the size of the longitudinal magnetization of the normal myocardium.
  • the mark X indicates the size of the longitudinal muscles of the infarcted myocardium
  • the country mark indicates the size of the longitudinal muscles of fat
  • the symbol ⁇ indicates the size of the longitudinal muscles of the liver.
  • the vertical dotted line indicates that the gradient echo method is performed within 130 msec and 330 msec after the application of the IR pulse.
  • FIG. 7 it is shown that the size of the longitudinal magnetism becomes maximum in the region 62 when the gradient echo method is performed, which is consistent with the experimental result shown in FIG. 5 (b).
  • the image data of the region 62 is normalized as the maximum value of the digital data, sufficient contrast cannot be obtained between the normal myocardium and the infarcted myocardium, which need to obtain relatively sufficient contrast. It was shown from the discussion results.
  • the flip angle (the flip angle of the first RF panelless) was set to 60 degrees or less, for example, 30 degrees or 45 degrees. This makes it possible to properly image (image) the normal and infarcted myocardium with sufficient contrast, and it is also possible to acquire the navigation echo signal with sufficient S / N to detect the diaphragm position. It became. However, since the S / N of the navigation echo signal depends on the static magnetic field strength and the size of the diaphragm navigation area, the flip angle of the first RF pulse does not have to be 30 or 45 degrees, and the diaphragm can be used.
  • the second RF pulse is required to efficiently invert the transverse magnetization component generated by the first RF pulse.
  • the flip angle of the second RF pulse be twice the flip angle of the first RF pulse, and in the present embodiment, the flip angle is twice as large.
  • the flip angle of the first RF pulse is greater than 0 degrees and less than 90 degrees
  • the flip angle of the second RF pulse is greater than 0 degrees and less than 180 degrees
  • the flip angle of the first RF pulse is Needless to say, it should be smaller than the flip angle of the RF panless.
  • the longitudinal magnetization of the region 62 is returned to its initial value by the application of the IR pulse, and the difference in contrast between the infarcted myocardium and the normal myocardium is prevented. Then, the longitudinal magnetic field excited by the first RF pulse and the second RF pulse is forcibly returned (flip back). That is, after acquiring the navigation echo signal, a third RF pulse in the opposite direction to the second RF pulse is applied to the area where the second RF pulse is applied, and the first RF pulse is applied to the area where the first RF pulse is applied. Apply a fourth RF pulse opposite to the RF pulse. For example, the first RF pulse is 90.
  • the third RF pulse is applied at -180 ° and the fourth RF pulse is applied at -90 °.
  • the first RF pulse is ⁇ ° and the second RF pulse is j8 °
  • the third RF pulse is ⁇ 13 °
  • the fourth RF pulse is ⁇ a °.
  • FIG. 8 A specific sequence diagram is shown in which 101 to 104 indicate the first to fourth RF pulses.
  • the time from when a diaphragm navigation sequence is executed to obtain a navigation echo signal to when an IR pulse is applied is externally input by an operator using a trackball or a mouse 31, a keyboard 32, or the like shown in FIG.
  • the longitudinal magnetization is returned to the initial value of the longitudinal magnetization as much as possible by longitudinal relaxation before applying the IR pulse in the imaging sequence. For example, increase the time interval of TN in Fig. 5.
  • the waiting time from obtaining the navigation echo signal to the application of the IR pulse is preferably such that the longitudinal magnetic field inverted by the IR pulse is half recovered. This time is equivalent to about 30% of the longitudinal relaxation time.
  • the value of the waiting time may be changed as needed.
  • the phases of the first and second RF pulses are made different, the magnitude of the second beam RF pulse is increased, and the IR pulse from the diaphragm navigation sequence is changed.
  • the application of the IR pulse does not have to be the application of the inversion pulse having the flip angle of 180 °, and the application of the presaturation pulse having the flip angle smaller than 180 ° is not required. To obtain the same effect.
  • the timing at which the pulse wave becomes stronger by the pulse wave meter It may be used as a reference, or a part of the blood vessel of the MRI image may be monitored, and the timing at which the pixel value changes rapidly may be used as a reference.
  • the operator can arbitrarily input the above-mentioned application timing and application intensity of the gradient magnetic field pulse and the RF pulse by using the trackball or the mouse 31 and the keyboard 32 shown in FIG. In accordance with that, the gradient pulse and RF pulse should be controlled by the sequencer 6!
  • FIG. 1 is a block diagram showing an overall configuration of an MRI apparatus according to an embodiment of the present invention.
  • FIG. 2 is a sequence diagram of a delayed contrast radiography with diaphragm navigation according to the first embodiment of the present invention.
  • FIG. 3 is a diagram showing a gradient echo sequence.
  • FIG. 4 is a diagram showing only a sequence diagram of a diaphragm navigation sequence in a sequence of a delay contrast imaging method using a diaphragm navigation according to a second embodiment of the present invention.
  • FIG. 5 (a) is an image obtained by the delayed contrast imaging method
  • FIG. 5 (b) is a diagram showing an experimental result obtained by changing the value of oc.
  • FIG. 6 is a diagram for examining a change in the size of longitudinal magnetism in each region of FIG. 5 (a).
  • FIG. 7 is a graph showing how the size of longitudinal magnetic field changes with time after application of an IR pulse.
  • FIG. 8 In Example 3 of the present invention! And four RF pulses It is a figure showing an example of applying.

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Abstract

Une séquence d'imagerie améliorée à contraste de retard associée à un navigateur de diaphragme satisfaisant à la fois à la qualité d'image d'une image au contraste amélioré et à la précision de détection de la position du diaphragme. La séquence du navigateur de diaphragme est réalisée avant toute impulsion IR. En ce qui concerne la RF de la séquence du navigateur de diaphragme, l'angle d'inclinaison est réduit et la phase d'une seconde impulsion RF est basculée de 180° depuis la phase d'une première impulsion RF.
PCT/JP2005/007955 2004-04-27 2005-04-27 Appareil d'imagerie à résonance magnétique et méthode WO2005102162A1 (fr)

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JP2006512648A JPWO2005102162A1 (ja) 2004-04-27 2005-04-27 磁気共鳴イメージング装置及び方法

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JP2004130550 2004-04-27
JP2004-130550 2004-04-27

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WO2005102162A1 true WO2005102162A1 (fr) 2005-11-03

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007020852A (ja) * 2005-07-15 2007-02-01 Hitachi Medical Corp 磁気共鳴イメージング装置
US20230408616A1 (en) * 2022-06-17 2023-12-21 Siemens Healthcare Gmbh Single-voxel spectroscopy for quantitation of myocardial metabolites

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JP2000342555A (ja) * 1999-03-31 2000-12-12 Toshiba Corp Ｍｒｉ装置およびｍｒイメージング方法
JP2002102200A (ja) * 2000-09-26 2002-04-09 Ge Medical Systems Global Technology Co Llc 磁気共鳴信号獲得方法および装置、記録媒体並びに磁気共鳴撮影装置
JP2004024669A (ja) * 2002-06-27 2004-01-29 Hitachi Medical Corp 磁気共鳴イメージング装置
JP2004024637A (ja) * 2002-06-27 2004-01-29 Toshiba Corp Ｍｒｉ装置およびｍｒｉ画像撮影方法

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Publication number Priority date Publication date Assignee Title
JP2000342555A (ja) * 1999-03-31 2000-12-12 Toshiba Corp Ｍｒｉ装置およびｍｒイメージング方法
JP2002102200A (ja) * 2000-09-26 2002-04-09 Ge Medical Systems Global Technology Co Llc 磁気共鳴信号獲得方法および装置、記録媒体並びに磁気共鳴撮影装置
JP2004024669A (ja) * 2002-06-27 2004-01-29 Hitachi Medical Corp 磁気共鳴イメージング装置
JP2004024637A (ja) * 2002-06-27 2004-01-29 Toshiba Corp Ｍｒｉ装置およびｍｒｉ画像撮影方法

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007020852A (ja) * 2005-07-15 2007-02-01 Hitachi Medical Corp 磁気共鳴イメージング装置
US20230408616A1 (en) * 2022-06-17 2023-12-21 Siemens Healthcare Gmbh Single-voxel spectroscopy for quantitation of myocardial metabolites

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