JP5337385B2 - Magnetic resonance imaging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inform a subject of useful information for appropriately adjusting a respiratory level. <P>SOLUTION: An NMR signal for detecting the respiratory level of the subject 200 is acquired by the operation of each section under the control of a main control section 10g. The main control section 10g detects the respiratory level of the subject 200 as a first respiratory level based on the acquired NMR signals. A respiratory synchronization sensor 13 detects the respiratory level of the subject 200 as a second respiratory level based on a physical movement of the subject 200 following respiration. The NMR signals for obtaining an image are collected by the operation of each section under the control of the main control section 10g. The main control section 10g controls the collection to collect the NMR signals when the first respiratory level is within an allowable range. The main control section 10g forms a display image in which an image indicating the first respiratory level is combined with a graph indicating the change of the second respiratory level. A display system 12 displays the display image to the subject 200. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a magnetic resonance imaging apparatus that obtains an image of a body of a subject based on a magnetic resonance signal emitted from the body of the subject.

  In order to image the coronary artery by the magnetic resonance imaging (MRI) method, a method of capturing images under breath holding or natural breathing using a three-dimensional (3D) SSFP (steady state free precession) sequence is used. In particular, in the case of WH MRCA (whole heart MR coronary angiography) for imaging coronary artery travel of the entire heart, the spatial resolution may not be sufficient for breath holding. As countermeasures against this, under natural breathing, for example, the position of the diaphragm is detected based on NMR (nuclear magnetic resonance) signals to monitor the breathing level, and the image is picked up while changing the imaging position according to the breathing level. RMC (realtime motion correction) method is used.

  However, since there is a limit to the variable amount of the imaging position, a fixed threshold is set for the range of movement due to breathing, and when the movement is larger than the threshold, NMR signals for imaging are collected. A method of pausing is used. That is, for example, the position of the diaphragm in the body axis direction can be detected from a signal obtained by one-dimensional Fourier transform of the NMR signal collected for the region R as shown in FIG. Since the position of the diaphragm in the body axis direction periodically rises and falls according to breathing, the monitor signal as shown in FIG. 12 synchronized with the breathing motion is plotted by plotting the periodically detected diaphragm position in time series. Can be obtained. As shown in FIG. 12, when the peak of the monitor signal is outside the allowable range between the upper limit threshold USL and the lower limit threshold LSL, no imaging is performed or collected data is not used, and data is acquired when the peak is within the allowable range. Collect.

  FIG. 14 is a diagram showing an example of a sequence related to the above imaging method.

  The above imaging method is usually performed with electrocardiogram synchronization. After a certain delay time has elapsed from the R wave, MPP (motion probing pulse) is collected as an NMR signal for obtaining positional information for grasping the respiratory level. Immediately after this, data collection for photographing is performed.

  By doing so, a considerably high resolution 3D image can be obtained well even under natural breathing.

  However, the respiration level is not constant but gradually decreases or gradually increases, and the portion corresponding to the position of the diaphragm in the signal obtained by one-dimensional Fourier transform of the NMR signal is out of the allowable range as shown in FIG. In this case, there is a possibility that the imaging time becomes long or the inspection cannot be completed in the worst case.

Therefore, the applicant of the present application is applying Japanese Patent Application No. 2007-122737 for assisting the subject so that the subject can easily adjust the breathing level to an allowable range by notifying the subject of the breathing level monitored as described above. As proposed.
JP 2000-04-1970 JP 2000-157507 A JP 2004-057226 A

  However, the collection of NMR signals for obtaining position information is performed only once per heartbeat as described above. In other words, the respiratory level is monitored only once or twice for each breath as shown in FIG. 15. Even if only the monitored breathing level is notified to the subject, the subject is not breathing. Can not recognize the change. That is, the update speed of information acquired at the above-described cycle is too slow as the update speed of information for controlling the breathing level. In other words, the feedback time constant in respiration level control is long.

  For these reasons, the adjustment of the breathing level by the subject based on the breathing level monitored as described above is considered similar to the case where the feedback time constant in the automatic control is long. Can happen.

  The present invention has been made in consideration of such circumstances, and the purpose of the present invention is to notify useful information that enables the subject to appropriately adjust the respiratory level. It is to provide a magnetic resonance imaging apparatus.

A magnetic resonance imaging apparatus according to an aspect of the present invention is a magnetic resonance imaging apparatus that obtains an image of a body of a subject based on a magnetic resonance signal radiated from the body of the subject. Means for acquiring the magnetic resonance signal for detecting the respiration, first detection means for detecting the respiration level of the subject as a first respiration level based on the acquired magnetic resonance signal, and respiration A second detecting means for detecting the respiratory level of the subject as a second respiratory level based on the physical motion of the subject, and a collection for collecting the magnetic resonance signal for obtaining the image; Means, a means for controlling the acquisition means to acquire the magnetic resonance signal when the first respiration level is within an allowable range, and a graph representing a change in the second respiration level. First respiratory level Comprising generation means for generating a display image by combining an image representing, and display means for displaying the display image with respect to said subject.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to notify the useful information which enables a subject to adjust a respiration level appropriately.

  Hereinafter, first to third embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a magnetic resonance imaging apparatus (MRI apparatus) 100 according to the first to third embodiments. The MRI apparatus 100 includes a static magnetic field magnet 1, a gradient magnetic field coil unit 2, a gradient magnetic field power source 3, a bed 4, a bed control unit 5, a transmission RF coil 6, a transmission unit 7, a reception RF coil 8, a reception unit 9, and a computer system. 10, a video transmission system 11, a display system 12, and a respiratory synchronization sensor 13.

  The static magnetic field magnet 1 has a hollow cylindrical shape and generates a uniform static magnetic field in an internal space. For example, a permanent magnet or a superconducting magnet is used as the static magnetic field magnet 1.

  The gradient magnetic field coil unit 2 has a hollow cylindrical shape and is disposed inside the static magnetic field magnet 1. In the gradient coil unit 2, three types of coils corresponding to the X, Y, and Z axes orthogonal to each other are combined. In the gradient magnetic field coil unit 2, the above three types of coils are individually supplied with current from the gradient magnetic field power supply 3, and generate gradient magnetic fields whose magnetic field strengths change along the X, Y, and Z axes. The Z-axis direction is, for example, the same direction as the static magnetic field. The gradient magnetic fields of the X, Y, and Z axes are arbitrarily used as, for example, a slice selection gradient magnetic field Gs, a phase encoding gradient magnetic field Ge, and a readout gradient magnetic field Gr. The slice selection gradient magnetic field Gs is used to arbitrarily determine an imaging section. The phase encoding gradient magnetic field Ge is used to change the phase of the NMR signal in accordance with the spatial position. The readout gradient magnetic field Gr is used to change the frequency of the NMR signal in accordance with the spatial position.

  The subject 200 is inserted into the cavity of the gradient coil unit 2 while being placed on the top 4 a of the bed 4. The couchtop 4a of the couch 4 is driven by the couch controller 5 and moves in the longitudinal direction and the vertical direction. Usually, the bed 4 is installed such that the longitudinal direction thereof is parallel to the central axis of the static magnetic field magnet 1.

  The transmission RF coil 6 is disposed inside the gradient coil unit 2. The transmission RF coil 6 receives a high frequency pulse from the transmission unit 7 and generates a high frequency magnetic field.

  The transmission unit 7 transmits a high-frequency pulse corresponding to the Larmor frequency to the transmission RF coil 6.

  The reception RF coil 8 is disposed inside the gradient coil unit 2. The reception RF coil 8 receives an NMR signal radiated from the subject due to the influence of the high frequency magnetic field. An output signal from the reception RF coil 8 is input to the reception unit 9.

  The receiving unit 9 generates NMR signal data based on the output signal from the receiving RF coil 8.

  The computer system 10 includes an interface unit 10a, a data collection unit 10b, a reconstruction unit 10c, a storage unit 10d, a display unit 10e, an input unit 10f, and a main control unit 10g.

  The interface unit 10a is connected to the gradient magnetic field power source 3, the bed control unit 5, the transmission unit 7, the reception RF coil 8, the reception unit 9, the respiratory synchronization sensor 13, and the like. The interface unit 10a inputs and outputs signals exchanged between these connected units and the computer system 10.

  The data collection unit 10b collects digital signals output from the reception unit 9 via the interface unit 10a. The data collection unit 10b stores the collected digital signal, that is, NMR signal data, in the storage unit 10d.

  The reconstruction unit 10c performs post-processing, that is, reconstruction such as Fourier transform, on the NMR signal data stored in the storage unit 10d, and obtains spectrum data or image data of the desired nuclear spin in the subject 200. Ask.

  The storage unit 10d stores NMR signal data and spectrum data or image data for each patient.

  The display unit 10e displays various information such as spectrum data or image data under the control of the main control unit 10g. As the display unit 10e, a display device such as a liquid crystal display can be used.

  The input unit 10f receives various commands and information input from the operator. As the input unit 10f, a pointing device such as a mouse or a trackball, a selection device such as a mode switch, or an input device such as a keyboard can be used as appropriate. The input unit 10f accepts designation by an operator of an excitation slice or excitation slab as an imaging region such as the entire heart or a synchronization target region such as the diaphragm.

  The main control unit 10g includes a CPU, a memory, and the like (not shown), and controls the MRI apparatus 100 overall. The main control unit 10g generates a video signal indicating whether or not the respiration level is within the allowable range. This video signal is, for example, an NTSC (national television system committee) signal.

  The video transmission system 11 transmits the video signal generated by the main control unit 10g with light.

  The display system 12 displays an image based on the image signal so that the subject 200 placed in the imaging state can view the image.

  As the video transmission system 11 and the display system 12, for example, the configuration described in Japanese Patent Application No. 2007-122737 can be employed.

  The respiratory synchronization sensor 13 is attached to the abdomen of the subject 200 and detects the respiratory level of the subject 200 based on the physical movement of the abdomen of the subject 200.

(First embodiment)
In the first embodiment, the main controller 10g has a plurality of functions as follows. The plurality of functions can be realized by causing a processor included in the main control unit 10g to execute a program.

  One of the functions is to control each related unit so that the data collection unit 10b acquires an NMR signal (hereinafter referred to as a monitoring NMR signal) for detecting the breathing level of the subject 200. One of the functions is to detect the respiratory level of the subject 200 based on the monitoring NMR signal acquired by the data collection unit 10b. One of the functions described above is that an NMR signal for reconstructing an image (hereinafter referred to as a reconstruction NMR signal) is detected when a respiration level detected based on the monitor NMR signal is within an allowable range. Each related unit is controlled so as to be collected by the data collecting unit 10b. One of the functions is to generate a display image in which an image representing the respiratory level detected based on the monitoring NMR signal is combined with a respiratory waveform representing a change in the respiratory level detected by the respiratory synchronization sensor 13. Hereinafter, the respiration level detected based on the monitoring NMR signal is referred to as a first respiration level, and the respiration level detected by the respiration synchronization sensor 13 is referred to as a second respiration level.

  In the MRI apparatus 100 of the first embodiment, WH MRCA is executed according to a known sequence. During execution of such WH MRCA, the main control unit 10g generates a display image for notifying the subject 200 whether or not the breathing level of the subject 200 is within the allowable range as follows. In WH MRCA, an NMR signal for monitoring is acquired. The monitoring NMR signal is an NMR signal collected from a synchronization target site (excitation slice, excitation slab, etc.). The NMR signal for monitoring is acquired without applying a gradient magnetic field for phase encoding, for example.

  The main control unit 10g acquires the second respiration level detected by the respiration synchronization sensor 13 at a rate sufficient to reproduce the respiration waveform. The respiratory synchronization sensor 13 can continuously detect the respiratory level in real time using a bellows or the like.

  The main control unit 10g detects the first respiration level at a rate of once per heartbeat in the control for WH MRCA. The main control unit 10g generates, for example, a first image as shown in FIG. 2 in which each of the first respiration levels acquired in a recent fixed period is arranged on a plane defined by the time axis and the respiration level axis. To do.

  On the other hand, the main control unit 10g generates, for example, a second image as shown in FIG. 3 that represents the respiratory waveform in the period based on the second respiratory level acquired in the certain period.

  Then, the main control unit 10g generates a display image as an image obtained by combining the first image and the second image. At this time, the main control unit 10g normalizes and matches the amplitude scales (maximum value and minimum value) of the first respiratory level and the second respiratory level.

  The main control unit 10g updates the display image every time the second respiration level is acquired. Thus, the display image is an image in which the respiration waveform scrolls with time.

  By the way, since the first respiratory level requires some time to acquire the monitoring NMR signal or to obtain the respiratory level based on the monitoring NMR signal, the first respiratory level is more real-time than the respiratory synchronization sensor 13. Low. Therefore, as shown in FIG. 4, the first respiration level has a certain delay with respect to the second respiration level. Therefore, the main control unit 10g combines the first image and the second image so as to correct this delay.

  That is, assume that the display image immediately before the first respiration level is newly detected is in the state shown in FIG. When the display image is updated after the first respiration level is newly detected, the newly detected respiration level is not represented as current information, but the above-described delay as shown in FIG. The display image is updated so as to be represented as information at a time point back in time.

  The display image generated in this way is transmitted to the display system 12 via the interface unit 10a and the video transmission system 11, and the display system 12 displays the subject 200 in a state where the subject 200 can be seen.

  Thus, according to the first embodiment, the display image includes the first respiratory level detected based on the monitoring NMR signal and the second respiratory level detected based on the respiratory synchronization sensor 13. Represented at the same time. Therefore, the subject 200 can recognize the change of the respiratory level based on the respiratory waveform of the display image and the accurate respiratory level based on the display of the second respiratory level. As a result, the subject 200 can accurately grasp the actual breathing state, and can appropriately adjust the breathing.

(Second Embodiment)
In the second embodiment, the main controller 10g has a plurality of functions as follows. The plurality of functions can be realized by causing a processor included in the main control unit 10g to execute a program.

  One of the functions described above controls each related unit so that the data acquisition unit 10b acquires an NMR signal (hereinafter referred to as a monitoring NMR signal) used for detection of a respiration level for WH MRCA. One of the functions is to detect the respiratory level of the subject 200 (hereinafter referred to as the first respiratory level) based on the monitoring NMR signal. One of the functions described above is that an NMR signal for reconstructing an image (hereinafter referred to as a reconstruction NMR signal) is detected when a respiration level detected based on the monitor NMR signal is within an allowable range. Each related unit is controlled so as to be collected by the data collecting unit 10b. One of the functions is to control each related unit so that the data acquisition unit 10b acquires an NMR signal (hereinafter referred to as a display NMR signal) used to detect a respiration level for display. One of the functions is to detect the breathing level of the subject 200 (hereinafter referred to as the second breathing level) based on the display NMR signal. One of the functions described above generates a display image representing changes in the first and second respiratory levels.

  In the MRI apparatus 100 of the second embodiment, when performing WH MRCA, the main control unit 10g causes the data collection unit 10b to collect NMR signals according to a sequence as shown in FIG.

  In the sequence shown in FIG. 7, MPPs are collected a plurality of times within one heartbeat. The plurality of MPPs are classified into a main MPP collected immediately before the data collection period of the imaging region and a sub MPP collected at a timing different from the main MPP while avoiding the data collection period. The sub-MPP may be collected before or after the main MPP as long as it is a period excluding the data collection period of the imaging region. For example, a plurality of sub MPPs may be collected before the main MPP. Further, a plurality of MPPs (including not only the sub MPP but also the main MPP) may be collected at equal intervals within one heartbeat. In this case, if any of the plurality of MPPs set at equal intervals is included in the data collection period of the imaging region, the MPP is not collected.

  The main MPP corresponds to the MPP acquired in the conventional sequence shown in FIG. 14, and is used as an NMR signal for monitoring. The sub MPP is additionally acquired regardless of the control of the WH MRCA, and is used as a display NMR signal.

  The main control unit 10g detects the first respiration level for the WH MRCA based only on the monitoring NMR signal. The main control unit 10g does not use the WH MRCA, but also detects the second respiration level based on the display NMR signal. Then, the main control unit 10g arranges the first respiratory level and the second respiratory level acquired during a recent fixed period on a plane defined by the time axis and the respiratory level axis, for example, as shown in FIG. A simple display image is generated.

  The display image generated in this way is transmitted to the display system 12 via the interface unit 10a and the video transmission system 11, and the display system 12 displays the subject 200 in a state where the subject 200 can be seen.

  Thus, according to the second embodiment, a large number of respiration levels detected in a short cycle are displayed in time series on the display image. Therefore, the subject 200 can recognize the state of change in the respiratory level from this display image. As a result, the subject 200 can accurately grasp the actual breathing state, and can appropriately adjust the breathing.

(Third embodiment)
In the third embodiment, the main controller 10g has a plurality of functions as follows. The plurality of functions can be realized by causing a processor included in the main control unit 10g to execute a program.

  One of the functions is to control each related unit so that the data acquisition unit 10b acquires an NMR signal (hereinafter referred to as a monitoring NMR signal) used for detection of the respiratory level. One of the functions described above detects the respiration level of the subject 200 based on the monitoring NMR signal. One of the functions described above is that an NMR signal for reconstructing an image (hereinafter referred to as a reconstruction NMR signal) is detected when a respiration level detected based on the monitor NMR signal is within an allowable range. Each related unit is controlled so as to be collected by the data collecting unit 10b. One of the functions generates a display image that represents the most recently detected respiratory level and the highest detected level detected within a predetermined period.

  In the MRI apparatus 100 of the third embodiment, WH MRCA is executed according to a known sequence. During execution of such WH MRCA, the main control unit 10g generates a display image for notifying the subject 200 whether or not the breathing level of the subject 200 is within the allowable range as follows.

  The main control unit 10g detects the respiration level at a rate of once per heartbeat in the control for WH MRCA. Each time the main control unit 10g newly detects a respiration level, the main control unit 10g generates a display image representing the detected respiration level.

  For example, as shown in FIG. 9, the main control unit 10g generates a display image IA as shown in FIG. 10 in response to the detection of the respiration level as shown in FIG. In the display image IA, the respiration level detected at the time point TA is represented by a black dot.

  On the other hand, in response to the detection of the respiration level as shown in FIG. 9 at the time TB, the main control unit 10g displays the respiration level detected at the time TB as a black dot as shown in FIG. Is generated. Now, the detection level detected at the time point TB is lower than the detection level detected at the time point TA. In such a case, the main control unit 10g represents the detection level detected at the time point TA in the display image IB as the latest highest level. In FIG. 10, the highest level is represented as a hatched point.

  In response to the detection of the respiration level as shown in FIG. 9 at time TB, the main control unit 10g generates a display image IC that represents the respiration level detected at time TC as a black dot, as shown in FIG. To do. Since the respiration level detected at the time point TC is higher than the highest level so far, the highest level is not displayed on the display image IC.

  Thereafter, similarly, the display images ID to IF of FIG. 10 are respectively generated at the time TD to the time TF of FIG.

  In response to the detection of the respiration level as shown in FIG. 9 at the time point TH, as shown in FIG. 10, the main control unit 10g generates a display image IH in which the respiration level detected at the time point TH is represented by a black dot. To do. The highest level so far has been the respiratory level detected at the time point TC, but at the time point TH, the specified time T1 or more has elapsed from the time point TC. In such a case, the main control unit 10g cancels the highest level so far and does not display it in a newly generated image.

  Thereafter, similarly, display images IG to IJ in FIG. 10 are generated at time points TH to TJ in FIG.

  The display image generated in this way is transmitted to the display system 12 via the interface unit 10a and the video transmission system 11, and is sequentially displayed by the display system 12 in a state in which the subject 200 is visible.

  Thus, according to the third embodiment, the display image shows the most recently detected respiration level and the highest respiration level detected within a recent period of time. Therefore, the subject 200 can recognize from this display image how the current respiration level is related to the latest highest level. As a result, the subject 200 can accurately grasp the actual breathing state, and can appropriately adjust the breathing.

  This embodiment can be variously modified as follows.

  In the first embodiment, normalization and delay correction may not be performed.

  In the second embodiment, the number of times per heartbeat at which the sub MPP is acquired may be any number of one or more.

  In the second embodiment, when the sub MPP is acquired a plurality of times per heartbeat, the respiration level determined based on the main MPP may not be included in the display image.

  In the third embodiment, if the highest level and the current respiratory level are expressed in different forms so that they are displayed even when both levels match, the highest level and the current respiratory level are displayed. Is more easily understood by the subject 200. This can be realized by changing the maximum level by a horizontal line, for example.

  In each embodiment, the specific content of the display image can be arbitrarily changed.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The figure which shows the structure of the magnetic resonance imaging device 100 which concerns on the 1st thru | or 3rd embodiment of this invention. The figure which shows an example of the 1st image in 1st Embodiment. The figure which shows an example of the 2nd image in 1st Embodiment. The figure which shows the delay with respect to the 2nd respiration level of the 1st respiration level in 1st Embodiment. The figure which shows an example of the display image immediately before the 1st respiration level in 1st Embodiment is newly detected. The figure which shows an example of the display image immediately after the 1st respiration level in 1st Embodiment is newly detected. The figure which shows the sequence in the case of performing WH MRCA in 2nd Embodiment. The figure which shows an example of the display image in 2nd Embodiment. The figure which shows an example of the detection state of the respiration level in 3rd Embodiment. The figure which shows an example of the display image produced | generated at each time in FIG. The figure which shows the area | region which collects the NMR signal for detecting a respiration level. The figure which shows an example of a monitor signal. The figure which shows an example of a mode that the peak of a monitor signal shift | deviates outside an allowable range. The figure which shows the basic sequence of WH MRCA. The figure which shows the relationship between the change of an actual respiration level, and the monitored respiration level.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Static magnetic field magnet, 2 ... Gradient magnetic field coil unit, 3 ... Gradient magnetic field power supply, 4 ... Bed, 5 ... Bed control part, 6 ... Transmission RF coil, 7 ... Transmission part, 8 ... Reception RF coil, 9 ... Reception part DESCRIPTION OF SYMBOLS 10a ... Interface part, 10b ... Data collection part, 10d ... Memory | storage part, 10 ... Computer system, 10c ... Reconstruction part, 10g ... Main control part, 10f ... Input part, 10e ... Display part, 11 ... Video transmission system, DESCRIPTION OF SYMBOLS 12 ... Display system, 13 ... Respiration synchronous sensor, 100 ... Magnetic resonance imaging device (MRI apparatus), 200 ... Subject.

Claims (3)

In a magnetic resonance imaging apparatus for obtaining an image in the subject's body based on a magnetic resonance signal emitted from the subject's body,
Means for obtaining the magnetic resonance signal for detecting the respiratory level of the subject;
First detection means for detecting the respiratory level of the subject as a first respiratory level based on the acquired magnetic resonance signal;
Second detection means for detecting the subject's breathing level as a second breathing level based on the physical movement of the subject accompanying breathing;
Collecting means for collecting the magnetic resonance signals for obtaining the image;
Means for controlling said acquisition means to acquire said magnetic resonance signal when said first respiratory level is within an acceptable range;
Generating means for generating a display image combining a graph representing a change in the second respiration level and an image representing the first respiration level;
A magnetic resonance imaging apparatus comprising: display means for displaying the display image to the subject.   The generation unit generates a display image in which a normalized graph representing a change in the second respiration level and a normalized image representing the first respiration level are combined. Item 2. The magnetic resonance imaging apparatus according to Item 1.   The generating means combines the images with the graph while correcting the difference in time required for the first and second detection means to detect the first and second respiration levels, respectively, and displays the display image. The magnetic resonance imaging apparatus according to claim 1, wherein the magnetic resonance imaging apparatus generates the magnetic resonance imaging apparatus.

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