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WO2010058732A1 - Dispositif d'imagerie à résonance magnétique et procédé d'imagerie à résonance magnétique - Google Patents

Dispositif d'imagerie à résonance magnétique et procédé d'imagerie à résonance magnétique Download PDF

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Publication number
WO2010058732A1
WO2010058732A1 PCT/JP2009/069269 JP2009069269W WO2010058732A1 WO 2010058732 A1 WO2010058732 A1 WO 2010058732A1 JP 2009069269 W JP2009069269 W JP 2009069269W WO 2010058732 A1 WO2010058732 A1 WO 2010058732A1
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Prior art keywords
magnetic resonance
measurement
resonance imaging
period
imaging apparatus
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English (en)
Japanese (ja)
Inventor
義隆 本間
正幸 磯部
隆史 常木
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Hitachi Healthcare Manufacturing Ltd
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Hitachi Medical Corp
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Priority to JP2010539213A priority Critical patent/JP5536665B2/ja
Priority to CN200980146043.8A priority patent/CN102215749B/zh
Publication of WO2010058732A1 publication Critical patent/WO2010058732A1/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
    • G01R33/567—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution gated by physiological signals, i.e. synchronization of acquired MR data with periodical motion of an object of interest, e.g. monitoring or triggering system for cardiac or respiratory gating
    • G01R33/5673—Gating or triggering based on a physiological signal other than an MR signal, e.g. ECG gating or motion monitoring using optical systems for monitoring the motion of a fiducial marker
    • 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
    • G01R33/56509—Correction of image distortions, e.g. due to magnetic field inhomogeneities due to motion, displacement or flow, e.g. gradient moment nulling

Definitions

  • the present invention measures nuclear magnetic resonance (hereinafter referred to as ⁇ NMR '') signals from hydrogen, phosphorus, etc. in a subject and images nuclear density distribution, relaxation time distribution, etc. , "MRI”) related to respiratory synchronized measurement in an apparatus.
  • ⁇ NMR '' nuclear magnetic resonance
  • MRI nuclear density distribution, relaxation time distribution, etc.
  • MRI equipment measures NMR signals (echo signals) generated by nuclear spins that make up the body of a subject, especially the human body, and forms the shape and function of the head, abdomen, limbs, etc. two-dimensionally or three-dimensionally. It is a device that automatically images.
  • the echo signal is given different phase encoding depending on the gradient magnetic field and is frequency-encoded and measured as time-series data.
  • the measured echo signal is reconstructed into an image by two-dimensional or three-dimensional Fourier transform.
  • Respiratory motion is one type of body motion of the subject, and various methods are employed to eliminate artifacts based on respiratory motion.
  • Respiratory motion is one type of body motion of the subject, and various methods are employed to eliminate artifacts based on respiratory motion.
  • This method uses a body motion detection sensor for monitoring respiration and navigator echo (navigator echo) to detect the respiratory time phase, i.e., the displacement position of the abdominal wall based on respiration, and the predetermined respiratory time phase, i.e. An image is reconstructed using an echo signal obtained at a predetermined displacement position.
  • This respiratory synchronization imaging may be performed in combination with the synchronization with the electrocardiogram waveform.
  • a delay time until the respiration is stabilized from a trigger signal that is driven according to respiration is visually determined by the operator.
  • Patent Document 1 As a measure for reducing respiratory artifacts mixed in an image, for example, there is a method described in Patent Document 1. In this method, application of phase encoding is controlled so that an echo signal measured at the timing when the acceleration of abdominal wall movement due to respiration becomes the lowest is arranged in a low-frequency region of k-space. The time efficiency of this method is the same as that of normal imaging without such phase encoding control, and artifacts are reduced compared to normal imaging.
  • the pulse sequence for the time that falls within the set respiratory stabilization time is executed, so that it is inevitably within the respiratory stabilization time.
  • the number of pulse sequences repeated and the number of echo signals measured are constant regardless of the respiratory cycle. Therefore, when the breathing interval of the subject is irregular, there is a possibility that the imaging time becomes long and becomes inefficient. This is because when trying to acquire an image with less body movement artifacts, it is necessary to match the execution time of the pulse sequence for one breath to the minimum breath stabilization time within the irregular breath stabilization time. This is because the number of echo signals that can be measured is reduced. Furthermore, no matter how much the pulse sequence execution time for one breath is shortened, if the echo signal measured at the timing when the breathing is disturbed due to irregular breathing, the artifact becomes conspicuous.
  • an object of the present invention is to acquire an image with good imaging efficiency and few body motion artifacts even in the case of irregular body motion in imaging using a magnetic resonance imaging apparatus.
  • a magnetic resonance imaging apparatus and a magnetic resonance imaging method of the present invention perform measurement for each period based on body movement information of a plurality of periods detected from a subject having periodic body movements. A period is detected, and the number of echo signals to be measured is controlled according to the detected time width of the measurement period.
  • the magnetic resonance imaging apparatus of the present invention is based on a body motion detection unit that detects periodic body motion information of a subject who breathes freely, and a body motion information based on a predetermined pulse sequence.
  • a measurement control unit that measures an echo signal of a predetermined phase encoding from the subject, an arithmetic processing unit that reconstructs the image of the subject using the echo signal, and a display unit that displays the image,
  • the arithmetic processing unit detects a measurement period for each cycle based on the body movement information of a plurality of cycles, and the measurement control unit controls the number of echo signals to be measured according to the time width of the detected measurement period. It is characterized by.
  • the magnetic resonance imaging method of the present invention detects a body motion detection step for detecting periodic body motion information of a freely breathing subject and detects a measurement period for each cycle based on body motion information of a plurality of cycles. And a measurement step of measuring an echo signal of a predetermined phase encoding from the subject according to body movement information based on a predetermined pulse sequence, and in the measurement step, The number of echo signals to be measured is controlled according to the time width.
  • the magnetic resonance imaging apparatus and magnetic resonance imaging method of the present invention it is possible to perform measurement in the same body motion time phase without depending on the stability of body motion. As a result, even if there is an irregular body movement, it is possible to acquire an image with good imaging efficiency and less body movement artifacts.
  • the block diagram which shows the whole structure of one Example of the MRI apparatus which concerns on this invention
  • An example of a respiratory waveform when breathing is irregular and a diagram illustrating a first embodiment of respiratory synchronous imaging according to the present invention
  • the flowchart showing the processing flow which concerns on the 1st Embodiment of this invention
  • An example of a respiration waveform when respiration is irregular and a diagram for explaining a second embodiment of respiration synchronization imaging according to the present invention
  • the figure which shows an example of GUI which sets the threshold value for selecting a flat period on a respiration waveform The figure which shows the example of a display which displays the progress of the breathing synchronous imaging which concerns on this invention
  • An example of a respiration waveform when respiration is irregular and a diagram for explaining a third
  • FIG. 1 is a block diagram showing the overall configuration of an embodiment of an MRI apparatus according to the present invention.
  • This MRI apparatus uses a NMR phenomenon to obtain a tomographic image of a subject.
  • the MRI apparatus includes a static magnetic field generation unit 2, a gradient magnetic field generation unit 3, a transmission unit 5,
  • the receiving unit 6, the arithmetic processing unit 7, and the measurement control unit 4 are configured.
  • the static magnetic field generator 2 generates a uniform static magnetic field in the direction perpendicular to the body axis in the space around the subject 1 if the vertical magnetic field method is used, and in the direction of the body axis if the horizontal magnetic field method is used. Therefore, a permanent magnet type, normal conducting type or superconducting type static magnetic field generating source is arranged around the subject 1.
  • the gradient magnetic field generator 3 includes a gradient magnetic field coil 9 wound in the three-axis directions of X, Y, and Z, which are coordinate systems (stationary coordinate system) of the MRI apparatus, and a gradient magnetic field power source 10 that drives each gradient magnetic field coil It consists of.
  • the gradient magnetic field power supply 10 of each coil is driven in accordance with a command from the measurement control unit 4 to be described later, so that the subject 1 lies in the gradient magnetic fields Gx, Gy, and Gz in the X, Y, and Z directions. Applied to the static magnetic field space.
  • a slice direction gradient magnetic field pulse is applied in a direction orthogonal to the slice plane (imaging cross section) to set a slice plane for the subject 1, and the remaining planes orthogonal to the slice plane and orthogonal to each other are set.
  • a phase encoding direction gradient magnetic field pulse (Gp) and a frequency encoding direction gradient magnetic field pulse (Gf) are applied in two directions, and position information in each direction is encoded in the echo signal.
  • the transmitter 5 irradiates the subject 1 with a high-frequency magnetic field pulse (hereinafter referred to as “RF pulse”) in order to induce an NMR phenomenon in the nuclear spin of atoms constituting the living tissue of the subject 1.
  • RF pulse high-frequency magnetic field pulse
  • the high-frequency pulse output from the high-frequency oscillator 11 is amplitude-modulated by the modulator 12 at a timing according to a command from the measurement control unit 4, and after the amplitude-modulated high-frequency pulse is amplified by the high-frequency amplifier 13, the subject 1 By being supplied to the high-frequency coil 14a arranged close to the RF pulse, the subject 1 is irradiated with the RF pulse.
  • the receiving unit 6 detects an echo signal emitted by the NMR phenomenon of the nuclear spin constituting the living tissue of the subject 1, and receives a high frequency coil (receiving coil) 14b on the receiving side, a signal amplifier 15, and quadrature detection. And an A / D converter 17.
  • the echo signal of the response of the subject 1 induced by the RF pulse irradiated from the high frequency coil 14a on the transmission side is detected by the high frequency coil 14b arranged close to the subject 1 and amplified by the signal amplifier 15. After that, it is divided into two orthogonal signals by the quadrature phase detector 16 at the timing according to the command from the measurement control unit 4, and each is converted into a digital quantity by the A / D converter 17 and calculated as echo data. It is sent to the processing unit 7.
  • the measurement control unit 4 controls the gradient magnetic field generation unit 3, the transmission unit 5, and the reception unit 6 on the basis of a predetermined pulse sequence to apply the RF pulse and the gradient magnetic field pulse and to measure the echo signal. It is a control means to repeat.
  • the measurement control unit 4 operates under the control of the CPU 8, and sends various commands necessary for collecting echo data necessary for reconstruction of the tomographic image of the subject 1 to the gradient magnetic field generation unit 3, the transmission unit 5, and the reception unit 6. To control them.
  • the arithmetic processing unit 7 performs various data processing and display and storage of processing results, and includes a CPU 8, an external storage device such as an optical disk 19 and a magnetic disk 18, and a display 20.
  • the echo data is stored in a memory corresponding to the K space in the CPU 8 (hereinafter described that the echo signal or echo data is arranged in the K space. Means that echo data is written and stored in this memory, and echo data arranged in K space is called K space data).
  • the CPU 8 performs arithmetic processing such as signal processing and image reconstruction on the K space data, and displays the tomographic image of the subject 1 as a result on the display 20 and records it in the external storage device. To do.
  • the operation unit 25 receives input of various control information of the MRI apparatus and control information of processing performed by the arithmetic processing unit 7 from the operator, and includes a trackball or mouse 23 and a keyboard 24.
  • the operation unit 25 is disposed close to the display 20, and the operator controls various processes of the MRI apparatus interactively through the operation unit 25 while looking at the display 20.
  • the MRI apparatus is mounted on or near the subject and receives a body motion sensor for detecting the body motion of the subject and a signal from the body motion sensor, A body motion detecting unit 26 for detecting the body motion information of the body.
  • the body motion information detected by the body motion detection unit 26 is input to the CPU 8 via the measurement control unit 4.
  • a body motion detection sensor that detects a change in position of the abdominal wall surface based on respiration
  • use an air pressure sensor that attaches an air bellows that expands and contracts according to the abdominal wall surface to the abdomen and detects the air pressure inside the air bellows. Can do. Since the bellows internal air pressure fluctuates in accordance with the expansion and contraction of the bellows, the fluctuating position of the abdominal wall surface can be indirectly detected by this air pressure.
  • an ultrasonic sensor that irradiates the abdominal wall surface with ultrasonic waves and detects the fluctuation position of the abdominal wall surface from the time required to detect the reflected wave may be used.
  • the high-frequency coil 14a and the gradient magnetic field coil 9 on the transmission side are located within the static magnetic field space of the static magnetic field generating unit 2 into which the subject 1 is inserted, and to the subject 1 if the vertical magnetic field method is used. Oppositely, if it is a horizontal magnetic field system, it is installed so as to surround the subject 1. The high-frequency coil 14b on the receiving side is installed so as to face or surround the subject 1.
  • the nuclide to be imaged by the current MRI apparatus is a hydrogen nucleus (proton) which is a main constituent material of the subject as widely used in clinical practice.
  • a first embodiment of the MRI apparatus and MRI method of the present invention will be described.
  • a stable period of body movement is detected based on body movement information of a plurality of cycles, and the number of echo signals to be measured is controlled according to the time width of each stable period.
  • respiratory motion as an example of body motion
  • the present invention and this embodiment are not limited to respiratory motion.
  • the outline of the present embodiment will be described, and then the processing flow of the embodiment will be described in detail.
  • the outline of the present embodiment is as follows.
  • the operator mounts the subject on the table in advance, attaches the body motion detection sensor to the subject, and the desired imaging region of the subject is positioned at the center of the magnetic field. So move the table. It is assumed that the subject is breathing freely without holding his / her breath during this preliminary preparation period and the next main measurement period. That is, the present invention and this embodiment do not force the subject to hold his / her breath.
  • the signal from the body motion detection sensor is input to the body motion detection unit 26.
  • the CPU 8 monitors the respiratory waveform of the subject input from the body motion detection unit 26 over a plurality of cycles before performing this measurement. Then, the respiratory waveform of multiple cycles is analyzed. Then, the CPU 8 determines a respiratory stable period to be detected from the respiratory waveform, that is, a flat period of the respiratory waveform (that is, an echo signal measurement period).
  • FIG. 2 and 3 show an example of the breathing waveform of the subject input from the body motion detection unit 26.
  • FIG. FIG. 2 shows an example of a respiratory waveform 200 of a subject with regular breathing
  • FIG. 3 shows an example of a respiratory waveform 300 of a subject with irregular breathing. Both show that the abdominal wall periodically moves up and down in the vertical direction as the subject periodically breathes.
  • the vertical axis represents the vertical displacement position of the abdominal wall
  • the horizontal axis represents time.
  • the upper side of the vertical axis corresponds to a state where the abdomen is inflated and the abdominal wall surface is raised
  • the lower side of the vertical axis corresponds to a state where the abdomen is depressed and the abdominal wall surface is lowered.
  • the flat period which is a stable breathing period in which the position of the abdominal wall surface does not change so much, has almost the same time interval over a plurality of periods in FIG. 2 where respiration is regular, and 201a and 201b are flat periods.
  • 201a and 201b are flat periods.
  • 301a, 301b, and 301c are flat periods, which are different time intervals within a plurality of periods.
  • the period between these flat periods is a non-flat period in which the abdominal wall surface is rapidly displaced.
  • the number of echo signals to be measured is changed according to the length of the flat period, and phase encoding applied to the echo signals to be measured is also controlled.
  • the number of echo signals measured in one respiratory cycle was constant (for example, 4), so in the case of a subject with irregular breathing as shown in FIG.
  • the number of echo signals to be measured is varied according to the length of the flat period.
  • the maximum possible number of echo signals is measured using the entire flat period. Therefore, it is possible to measure an echo signal necessary for image reconstruction using time efficiently.
  • the CPU 8 creates a histogram representing the frequency distribution of the values of the respiratory waveform, that is, the position frequency of the abdominal wall surface in the direction perpendicular to the abdominal wall surface (hereinafter z direction), using the respiration waveform as shown in FIG.
  • An example of the histogram is shown in FIG.
  • the horizontal axis of the histogram shown in FIG. 6 represents the displacement in the z direction of the position of the abdominal wall surface accompanying breathing, quantized between the lowest value and the highest value at a predetermined interval. That is, 0 (zero) corresponds to the lowest position of the abdominal wall position in the z direction, 144 corresponds to the highest position of the abdominal wall position in the z direction, and the values in between correspond to the intermediate positions of the abdominal wall surface. .
  • the vertical axis of the histogram represents the frequency of occurrence of each position on the abdominal wall surface in the z direction within one cycle of respiration.
  • the period when the abdominal wall position in the z-direction is low in the breathing cycle is longer than the period when the abdominal wall position in the z-direction is high in the breathing period.
  • the abdominal wall position is more frequent.
  • the CPU 8 After creating a histogram representing the frequency distribution of the values of the respiratory waveform as described above, the CPU 8 is in a range of the respiratory waveform corresponding to the state of exhaling, that is, a range of the respiratory waveform value lower than the created histogram.
  • the respiratory waveform value 601 having the highest frequency is detected.
  • the CPU 8 selects a respiratory waveform value range having a predetermined frequency as a respiratory stable state in both the left and right directions of the histogram centering on 601 and selects this respiratory stable state period as an echo signal measurement period. .
  • this period is referred to as a flat period.
  • the value of the respiratory waveform corresponding to the frequency at the right side from 601, that is, the larger one of the values of the respiratory waveform and having a predetermined frequency and located at a predetermined width ⁇ is set as the upper threshold 602.
  • the value of the respiratory waveform corresponding to the frequency at the left, that is, the smaller one of the values of the respiratory waveform and having the predetermined frequency and located at the predetermined width ⁇ is determined as the lower threshold 603, and the respiratory waveform sandwiched between them is determined.
  • the range of values is the flat period of the respiratory waveform.
  • ⁇ may be from 601 to the respiration waveform minimum value
  • ⁇ may be 0, and the respiration waveform minimum value to 601 may be the flat period of the respiration waveform.
  • the above is the description of the first determination method of the flat period of the respiratory waveform.
  • the second determination method is a method in which the operator selects the flat period directly on the respiratory waveform.
  • FIG. 7 shows an example of a GUI (graphical user interface) for selection of a flat period of the respiratory waveform by the operator.
  • a bar 701 representing an upper threshold for selecting a flat period range and a bar 702 representing a lower threshold are superimposed and displayed.
  • the operator uses the trackball or mouse 23 to adjust and set the vertical positions of these bars 701 and 702, thereby setting an upper threshold and a lower threshold, respectively.
  • the CPU 8 selects a period during which the value of the respiratory waveform is a value between the set upper and lower thresholds as a flat period.
  • the lower limit threshold 302 may be the respiratory waveform minimum value
  • the respiratory waveform minimum value to the upper threshold 701 may be the flat period of the respiratory waveform. The above is the description of the second determination method of the flat period of the respiratory waveform.
  • the threshold value for detecting the flat period may be determined by combining the above two methods.
  • the threshold value determined by the first method may be readjusted by the second method.
  • each threshold value determined by the first method is displayed as the initial position of the upper and lower limit threshold bars 701 and 702 in the second method.
  • the measurement control unit 4 Based on the imaging conditions set by the operator, the measurement control unit 4 repeatedly executes the pulse sequence with a repetition time (TR) set as one of the imaging conditions.
  • the repetition of this pulse sequence is preferably continued not only during the flat period but also during the non-flat period.
  • TR repetition time
  • SSFP Steady State Free Precision
  • the CPU 8 In a state where the pulse sequence is being executed, the CPU 8 continuously receives the respiratory waveform from the body motion detection unit 26, and based on each threshold value set or selected as described above, the CPU 8 Detect start time and end time as needed.
  • the start time of the flat period is the time when the respiration waveform falls outside the upper and lower threshold range
  • the end time of the flat period is the time when the respiration waveform falls outside the upper and lower threshold range. is there.
  • the CPU 8 instructs the measurement control unit 4 to start or restart the measurement of the echo signal. Then, the measurement control unit 4 starts or restarts the measurement of the echo signal by the pulse sequence based on the imaging conditions set in advance in accordance with the measurement start or restart instruction from the CPU 8. During the measurement of the echo signal, the CPU 8 instructs the measurement control unit 4 to stop measuring the echo signal when detecting the end point of the flat period. Then, the measurement control unit 4 interrupts the measurement of the echo signal according to the measurement interruption instruction from the CPU 8. The CPU 8 starts and restarts the measurement of the echo signal to the measurement control unit 4 and instructs the interruption until the measurement of the echo signal necessary for image reconstruction is completed. This is done for each detection. When the measurement of the echo signal necessary for image reconstruction is completed, the CPU 8 instructs the measurement control unit 4 to end the measurement, and the measurement control unit ends the execution of the pulse sequence according to the measurement end instruction from the CPU 8. .
  • the measurement control unit 4 measures an echo signal based on the same pulse sequence in each flat period. At this time, the measurement control unit 4 controls the number of echo signals to be measured according to the length of each flat period. Specifically, the measurement control unit 4 measures many echo signals during a long flat period and measures few echo signals during a short flat period. Preferably, the measurement control unit 4 measures the maximum possible number of echo signals in each flat period using the entire period regardless of the length of the flat period. As a result, the number of echo signals to be measured varies depending on the length of each flat period.
  • the measurement control unit 4 measures the echo signal by changing the phase encoding of the pulse sequence in each flat period. Specifically, in the measurement of the echo signal in each flat period, the measurement control unit 4 stores the measured phase encoding, and in the measurement of the echo signal in the next flat period, an unmeasured phase encoded echo Control application of phase encoding to measure the signal. For example, at the time of interruption of the measurement of the echo signal due to the end of the flat period, the measurement control unit 4 stores the phase encoding applied at the time of the measurement of the last echo signal, and at the time of restarting the measurement of the next flat period, The measurement control unit 4 restarts the measurement of the echo signal from the phase encoding next to the last stored phase encoding.
  • the measurement of the echo signal in the current flat period is performed by taking over the measurement of the echo signal in the previous flat period.
  • the measurement control unit 4 does not overlap the phase encoding applied to the echo signal measured in each flat period, and measures all the phase encoded echo signals necessary for image reconstruction. Control application of phase encoding during each flat period.
  • Fig. 2 shows an example of echo signal measurement during each flat period of a subject with regular breathing.
  • the vertical line represents the application timing of the excitation pulse in the pulse sequence. The same applies to FIGS. 3, 5, and 9 to be described later.
  • the echo signal 202a measured in the non-flat period before the flat period 201a is discarded.
  • the seven echo signals 203a of the phase encodes 1 to 7 are measured, and the echo signal 202b measured until the next flat period 201b is discarded.
  • the flat period 201b has the same period width as the previous flat period 301a, the phase encoding measured in the flat period 201b is 8 to 14, and the same 7 echo signal 203b. The same applies thereafter.
  • the number of echo signals measured in each flat period is substantially the same, and the phase encoding applied to each echo signal is continuous between the flat periods. Controlled.
  • FIG. 3 shows an example of echo signal measurement during each flat period of a subject with irregular breathing.
  • the echo signal 302a measured in the non-flat period before the flat period 301a is discarded.
  • the five echo signals 303a of the phase encodings 1 to 5 are measured, and the echo signal 302b measured until the next flat period 301b is discarded.
  • the measured phase encoding is only 6 and 7 two-echo signals 303b.
  • the period from the flat period 301b to the next flat period 301c is long, more echo signals 302c are measured and discarded during this period.
  • the four echo signals 303c of the phase encodes 8 to 11 are measured.
  • the echo signal 302d measured in the non-flat period next to the flat period 301c is discarded.
  • the number of echo signals measured in each flat period is controlled corresponding to the flat period width. That is, if the flat period is short, the number of echo signals is reduced, and if the flat period is long, the number of echo signals is increased.
  • the phase encoding applied to each echo signal is controlled to be continuous during each flat period.
  • the measurement control unit 4 terminates free breath measurement when measurement of all echo signals necessary for image reconstruction is completed.
  • the measurement control unit 4 repeats the measurement of the echo signal in the flat period and the discard of the echo signal in the non-flat period regardless of whether the breathing is regular or irregular.
  • the number of echo signals to be measured is controlled according to the length of each flat period, and the application of phase encoding is controlled so that the phase encoding applied to the echo signal to be measured is continuous in each flat period. .
  • This makes it possible to perform time-effective imaging regardless of whether the breathing is regular or irregular.
  • the pulse sequence is continuously executed during the non-flat period, the echo signal intensity is stabilized over a long period of time, and the image quality is improved.
  • the progress of the measurement may be displayed in an easy-to-understand manner to the operator, preferably also to the subject.
  • the display content may be, for example, the ratio of measured phase encoding to the total phase encoding, the number of measured / unmeasured phase encodings, the estimated value of the remaining imaging time, and the like.
  • FIG. 8 shows an example of progress display of respiratory synchronous measurement.
  • FIG. 8 (a) shows an example in which the measured number of phase encodings (802) is displayed on the left and right with “/” between the total number of phase encodings (801).
  • FIG. 8B shows an example in which the actual measurement elapsed time (804) and the total measurement time (803) predicted from the total number of phase encodings are displayed on the left and right with “/” in between.
  • Fig. 8 (c) shows an example of displaying the proportion of the measured phase encoding number corresponding to the total number of phase encodings with a progress bar, and the entire bar corresponding to the total number of phase encodings is represented as the proportion of the measured phase encoding number. An example of filling with different color bars corresponding to is shown.
  • FIG. 4 is a flowchart showing two processing flows of this embodiment. Hereinafter, the processing of each step will be described.
  • the operator mounts the subject on the table, attaches the body motion detection sensor to the subject, moves the table, and moves the subject to the desired condition.
  • the following steps are executed in a state where the imaging part is arranged at the center of the magnetic field.
  • step 401 the CPU 8 monitors the breathing waveform of the subject breathing freely input from the body motion detection unit 26 for a certain period of time.
  • the CPU 8 analyzes the respiration waveform and determines a threshold value for detecting a flat period of the respiration waveform.
  • the flat period may be determined by either the above-described method using the histogram as the first method or the method directly selected by the operator as the second method.
  • the threshold value determined by the first method may be readjusted by the second method.
  • step 403 based on the imaging conditions set by the operator, the measurement control unit 4 repeatedly executes a pulse sequence at a repetition time (TR) and starts measuring an echo signal.
  • step 404 the CPU 8 obtains the breathing waveform value of the subject input from the body motion detection unit 26, that is, the displacement position of the abdominal wall surface.
  • step 405 the CPU 8 determines whether the value of the respiratory waveform belongs to the flat period or the non-flat period based on each threshold value determined in step 402. If it is determined that it belongs to the flat period, the process proceeds to step 406. If it is determined that it belongs to the non-flat period, the process proceeds to step 408.
  • step 406 since the measured echo signal is measured in a flat period, the CPU 8 sets the echo signal to a k-space position corresponding to the phase encoding applied to the echo signal in order to adopt the echo signal for image reconstruction. Place echo data. Further, as described above, the CPU 8 may update the measurement progress display according to the measured number of phase encodings.
  • step 407 the measurement control unit 4 advances the phase encoding to the next step.
  • step 408 since the measured echo signal is measured in a non-flat period, the CPU 8 discards the echo signal without using it for image reconstruction.
  • step 410 the CPU 8 determines whether or not an all-phase encoding echo signal has been measured. If the all-phase encoding echo signal has been measured, the CPU 8 ends this measurement processing flow and measures the all-phase encoding echo signal. If not, return to Step 404.
  • the CPU 8 determines whether or not an all-phase encoding echo signal has been measured. If the all-phase encoding echo signal has been measured, the CPU 8 ends this measurement processing flow and measures the all-phase encoding echo signal. If not, return to Step 404.
  • the CPU 8 determines whether or not an all-phase encoding echo signal has been measured. If the all-phase encoding echo signal has been measured, the CPU 8 ends this measurement processing flow and measures the all-phase encoding echo signal. If not, return to Step 404.
  • the respiratory waveform has been described as an example.
  • the present invention can be similarly applied to measurement using other biological information such as an electrocardiographic waveform and a pulse wave.
  • image reconstruction is performed using only echo signals measured during the flat period of the respiratory waveform, regardless of whether the breathing is regular or irregular. Therefore, even if the breathing is irregular, artifacts based on the irregular breathing can be suppressed and a high-quality image can be acquired.
  • the number of echo signals to be measured is controlled according to the length of the flat period of the respiratory waveform, and when the measurement extends over a plurality of flat periods, the phase encoding applied to the echo signal measured in each flat period The application of phase encoding is controlled so as not to overlap. As a result, imaging can be performed under free breathing without forcing the subject to hold his / her breath, and the imaging efficiency is improved regardless of whether the breathing is regular or irregular. It becomes possible to minimize.
  • FIG. 5 shows an example in which three multi-slice imaging is performed.
  • the measurement control unit 4 measures the echo signal for each slice with the same phase encoding in one repetition time (TR). For example, as shown in FIG. 5, in the flat period 501a, the measurement control unit 4 repeats the multi-slice sequence three times, measures the echo signal of phase encoding 1 for each slice at the first repetition time (TR), and Measure echo signals from encode 1-1 to phase encode 3-1.
  • the first number means a slice number
  • the next number means a phase encoding number.
  • the measurement control unit 4 measures the next phase encode 2 echo signal for each slice, and measures the echo signals of phase encode 1-2 to phase encode 3-2.
  • the measurement control unit 4 measures the next phase encode 3 echo signal for each slice, and measures the phase encode 1-3 to phase encode 3-3 echo signals.
  • the measurement control unit 4 measures the echo signal of the phase encode 4, which is the next step of the phase encode measured last in the flat period 501a, for each slice, and performs phase encoding 1-4 to phase encoding. Measure the echo signal of encode 3-4. Note that it is not necessary to repeatedly measure echo signals having the same slice number and phase encoding during each flat period, so that the slice number and phase encoding need not be continuous.
  • the measurement control unit 4 repeats the measurement of the echo signal of the same phase encoding for each slice in each subsequent flat period with the repetition time (TR) by changing the phase encoding, and for each slice.
  • the measurement of the echo signal in the flat period is repeated until the measurement of the phase encoded echo signal is completed.
  • the measurement control unit 4 repeats the multi-slice sequence even in the non-flat period, but the phase encoding at that time may be any or may not be applied. This stabilizes the signal strength of the echo signal and improves the image quality.
  • the echo signal of each slice measured in the non-flat period, before the flat period 501a, between the flat period 501a and the next flat period 501b, and after the flat period 501b is adopted for image reconstruction. It is destroyed without
  • the same effects as those of the first embodiment can be obtained even in multi-slice imaging.
  • images are reconstructed using only the echo signal measured during the flat period of the respiration waveform for each slice, regardless of whether the respiration is regular or irregular. It is possible to obtain a high-quality image for each slice efficiently.
  • the respiratory synchronization measurement of the present invention is applied to three-dimensional imaging.
  • the three-dimensional imaging instead of changing the slice position in multi-slice imaging, after the volume is excited, slice encoding is applied in the slice direction independently of the phase encoding, and the position information in the slice direction is encoded into the echo signal.
  • the difference from each of the above-described embodiments is three-dimensional imaging, in which echo signal measurement during each flat period is performed so that slice encoding and phase encoding do not overlap, that is, at least slice encoding and phase encoding.
  • the point is that the application of each encoding is controlled so that one is different.
  • FIG. 9 shows an example of performing three-dimensional imaging with a slice encoding number of 4.
  • the measurement control unit 4 measures a predetermined slice encoding and phase encoding echo signal in one repetition time (TR), and the slice encoding and phase for each repetition.
  • the echo signal is measured by changing at least one of the encoding.
  • FIG. 9 shows an example in which the unit for repeating the measurement of the echo signal by changing the slice encoding with the phase encoding fixed is changed by changing the phase encoding.
  • the measurement control unit 4 changes the slice encoding loop to the inside, and provides a loop for changing the phase encoding outside this loop to apply both encodings. To control. Conversely, the unit in which the slice encoding is fixed and the phase encoding is changed to repeat the echo signal measurement may be repeated by changing the slice encoding.
  • the measurement control unit 4 controls the application of each encoding so that at least one of the slice encoding and the phase encoding is different in each flat period.
  • FIG. 9 shows an example in which the measurement control unit 4 controls each encoding so that the measurement order of slice encoding and phase encoding continues in each flat period. Since at least one of the encodings is different in each flat period, it is not necessary to be continuous.
  • the measurement control unit 4 repeats the three-dimensional pulse sequence in the flat period 901a as a first loop to change the slice encoding by fixing the phase encoding to 1. Measure four echo signals of encoding 1-1 to 4-1.
  • the first number represents slice encoding
  • the second number represents phase encoding.
  • a loop for changing the phase encoding to 2 and changing the slice encoding is repeated, and four echo signals of the encodings 2-1 to 2-4 are measured.
  • the measurement control unit 4 measures up to the echo signal of encode 3-3 in accordance with the period width of the flat period 901a, and adds 11 echo signals (903a of encode 1-1 to 3-3) in total. ).
  • the measurement control unit 4 starts measuring the echo signal from the next encode 4-3 after the last encode 3-3 applied in the previous flat period 901a.
  • a loop for changing the slice encoding by changing the phase encoding to 4 is repeated, and four echo signals of the encodings 1-4 to 4-4 are measured.
  • a loop for changing the slice encoding by changing the phase encoding to 5 is repeated, and two echo signals of encoding 1-5 to 2-5 are measured. That is, the measurement control unit 4 measures the echo signals from the encoding 4-3 to 2-5 according to the period width of the flat period 901b, and totals seven echo signals of the encoding 1-1 to 3-3. (903b) is measured. The same applies to the subsequent flat periods.
  • the measurement control unit 4 repeats the three-dimensional pulse sequence even in the non-flat period, but the slice encoding and the phase encoding at that time may be either or may not be applied. This stabilizes the signal strength of the echo signal and improves the image quality.
  • each echo signal measured in the non-flat period, before the flat period 901a, between the flat period 901a and the next flat period 901b, and after the flat period 501b is adopted for image reconstruction. It is destroyed without.
  • the same effects as those of the first embodiment can be obtained even in three-dimensional imaging.
  • images are reconstructed using only echo signals measured during the flat period of the respiration waveform, regardless of whether the respiration is regular or irregular. Therefore, artifacts based on respiration are suppressed and time is efficiently used. It becomes possible to acquire high-quality 3D images.
  • the MRI apparatus and the MRI method of the present invention are not limited to the contents disclosed in the description of the above embodiments, and can take other forms based on the gist of the present invention.
  • the present invention is not limited to the flat period, and a desired period of the body motion waveform is selected. You can choose. If there is another period in which the body movement is stable, such a stable period may be selected. For example, in breathing motion, a period of inhalation is possible. What is necessary is just to set a threshold value so that a desired period can be selected.
  • 1 subject 2 static magnetic field generation system, 3 gradient magnetic field generation system, 4 sequencer, 5 transmission system, 6 reception system, 7 signal processing system, 8 central processing unit (CPU), 9 gradient magnetic field coil, 10 gradient magnetic field power supply , 11 High-frequency transmitter, 12 modulator, 13 high-frequency amplifier, 14a high-frequency coil (transmitting coil), 14b high-frequency coil (receiving coil), 15 signal amplifier, 16 quadrature phase detector, 17 A / D converter, 18 magnetic disk , 19 Optical disk, 20 Display, 21 ROM, 22 RAM, 23 Trackball or mouse, 24 Keyboard, 51 Gantry, 52 Table, 53 Housing, 54 Processing device

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Abstract

L'invention permet d'acquérir une image avec une grande efficacité d'imagerie et peu d'artefacts de mouvement du corps en détectant une période de mesure pour chaque cycle sur la base des informations sur le mouvement du corps pour une pluralité de cycles après détection sur un sujet réalisant des mouvements cycliques du corps, et en contrôlant le nombre de signaux d'écho à mesurer selon la durée de la période de mesure détectée.
PCT/JP2009/069269 2008-11-18 2009-11-12 Dispositif d'imagerie à résonance magnétique et procédé d'imagerie à résonance magnétique Ceased WO2010058732A1 (fr)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011110433A (ja) * 2009-11-27 2011-06-09 Siemens Ag 呼吸する検査対象の測定データを磁気共鳴技術によって取得するための方法およびそれに用いられるコンピュータプログラム
JP2012000306A (ja) * 2010-06-18 2012-01-05 Hitachi Medical Corp 磁気共鳴イメージング装置およびその撮像方法
JP2014511745A (ja) * 2011-04-19 2014-05-19 コーニンクレッカ フィリップス エヌ ヴェ Ａｐｔ／ｃｅｓｔを使用する運動トリガｍｒ撮像
WO2015121103A1 (fr) * 2014-02-13 2015-08-20 Koninklijke Philips N.V. Procédé d'imagerie par résonance magnétique 4d à temps optimisé

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102016205718A1 (de) * 2016-04-06 2017-10-12 Siemens Healthcare Gmbh Verfahren zur Darstellung von medizinischen Bilddaten
JP7020930B2 (ja) * 2018-01-24 2022-02-16 富士フイルムヘルスケア株式会社 磁気共鳴イメージング装置、磁気共鳴イメージングシステム及びパラメータ推定方法
CN109001660B (zh) * 2018-06-12 2020-07-28 上海联影医疗科技有限公司 电影成像方法及磁共振成像系统
CN114795182B (zh) * 2022-06-24 2022-09-02 山东奥新医疗科技有限公司 一种磁共振成像伪影消除方法及相关组件

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63300750A (ja) * 1987-05-26 1988-12-07 ゼネラル・エレクトリック・カンパニイ 像の人為効果を減らす方法

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4567893A (en) * 1984-11-21 1986-02-04 General Electric Company Method of eliminating breathing artifacts in NMR imaging
JPH01218439A (ja) * 1988-02-26 1989-08-31 Hitachi Ltd 磁気共鳴イメージング装置
US5329925A (en) * 1991-11-14 1994-07-19 Picker International, Inc. Reduced scan time cardiac gated magnetic resonance cine and flow imaging
JP4515616B2 (ja) * 2000-09-25 2010-08-04 株式会社東芝 磁気共鳴イメージング装置
JP3669976B2 (ja) * 2002-07-08 2005-07-13 株式会社日立製作所 磁気共鳴撮影装置
JP4807825B2 (ja) * 2005-07-25 2011-11-02 株式会社日立メディコ 磁気共鳴イメージング装置
JP2007190114A (ja) * 2006-01-18 2007-08-02 Hitachi Medical Corp 磁気共鳴イメージング装置
JP2008055023A (ja) * 2006-09-01 2008-03-13 Hitachi Medical Corp 磁気共鳴イメージング装置
JP5288745B2 (ja) * 2006-09-13 2013-09-11 株式会社東芝 磁気共鳴イメージング装置
JP2008148918A (ja) * 2006-12-18 2008-07-03 Ge Medical Systems Global Technology Co Llc Ｍｒｉ装置およびその制御方法
JP4789961B2 (ja) * 2008-02-08 2011-10-12 オリンパス株式会社 画像表示装置

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63300750A (ja) * 1987-05-26 1988-12-07 ゼネラル・エレクトリック・カンパニイ 像の人為効果を減らす方法

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011110433A (ja) * 2009-11-27 2011-06-09 Siemens Ag 呼吸する検査対象の測定データを磁気共鳴技術によって取得するための方法およびそれに用いられるコンピュータプログラム
JP2012000306A (ja) * 2010-06-18 2012-01-05 Hitachi Medical Corp 磁気共鳴イメージング装置およびその撮像方法
JP2014511745A (ja) * 2011-04-19 2014-05-19 コーニンクレッカ フィリップス エヌ ヴェ Ａｐｔ／ｃｅｓｔを使用する運動トリガｍｒ撮像
US10175332B2 (en) 2011-04-19 2019-01-08 Koninklijke Philips N.V. Motion triggered MR imaging using APT/CEST
WO2015121103A1 (fr) * 2014-02-13 2015-08-20 Koninklijke Philips N.V. Procédé d'imagerie par résonance magnétique 4d à temps optimisé
JP2017506101A (ja) * 2014-02-13 2017-03-02 コーニンクレッカ フィリップス エヌ ヴェＫｏｎｉｎｋｌｉｊｋｅ Ｐｈｉｌｉｐｓ Ｎ．Ｖ． 時間効率的な４ｄ磁気共鳴イメージング
US10247804B2 (en) 2014-02-13 2019-04-02 Koninklijke Philips N.V. Method of time-efficient 4D magnetic resonance imaging

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