JP6685097B2 - Magnetic resonance device - Google Patents

Description

  The present invention relates to a magnetic resonance apparatus that executes a scan for obtaining an image of a region to be imaged (for example, a liver).

  DWI (Diffusion Weighted Imaging) sequence, 3D FSE (Fast Spin Echo) sequence and the like are known as sequences used for imaging the liver. The DWI sequence is a sequence for acquiring a diffusion weighted image, and the 3D FSE sequence is a sequence suitable for acquiring a T2 weighted image or a proton density (PD: Proton Density) weighted image. By using these sequences, tumors and cysts can be visualized with high brightness. Therefore, in recent years, the usefulness of the DWI sequence and the 3D FSE sequence has attracted attention.

  However, since the liver moves due to respiration of the subject, it is important to reduce body movement artifacts due to respiration as much as possible when the subject is imaged. Further, since the liver is close to the heart, there is a problem that it is easily affected by the movement (pulsation) of the heart of the subject, and pulsation artifacts are likely to occur. In particular, the left lobe of the liver is known to have a reduced signal due to the influence of pulsation. Therefore, it is important to reduce the effects of breathing and pulsation.

  On the other hand, it is known that the effects of respiration and heartbeat can be reduced by an imaging method that uses both respiration synchronization and heartbeat synchronization. For example, Patent Document 1 discloses an example of an imaging method using both respiratory synchronization and heartbeat synchronization.

JP, 2005-002834, A

  In the method of Patent Document 1, a navigator sequence and an image acquisition sequence are repeatedly set in synchronization with a heartbeat signal, and when the navigator echo enters a gate window, the image data is accepted, while the navigator echo receives the gate window. If not entered, the image data is discarded. Therefore, it is possible to reduce the effects of breathing and heartbeat.

  Further, in the method of Patent Document 1, the navigator sequence and the image acquisition sequence are repeatedly set in synchronization with the heartbeat signal. Therefore, the repetition time TR becomes TR = 1 second. When TR is about 1 second, it is suitable for capturing a T1-weighted image.

  On the other hand, when acquiring a DWI image, a T2-weighted image, and a PD-weighted image, it is necessary to recover the tissue in the imaging region sufficiently by T1 before data collection. Therefore, TR should be set as long as possible. Will be needed. However, in the method of Patent Document 1, since TR≈1 second, the next image acquisition sequence is executed after the image acquisition sequence is performed and before the tissue of the imaging region is fully recovered by T1, so that the DWI There is a problem that it is difficult to acquire an image, a T2-weighted image, and a PD-weighted image.

  Therefore, it is an imaging method using both respiratory synchronization and heartbeat synchronization, and after performing a sequence, such as a scan for acquiring a DWI image, T2-weighted image, or PD-weighted image, after performing T1 recovery as much as possible, There is a need to provide an imaging method suitable for performing the scans required to perform the following sequence.

A first aspect of the present invention is a magnetic field for performing a first scan for obtaining respiration information from a first region of a subject and a second scan for obtaining an image of an imaged region of the subject. A resonance device,
In the first scan, a plurality of first navigator sequences for collecting a plurality of first data including respiratory information from the first region are executed, and in the second scan, the first navigator sequence is executed. Scanning means for performing a plurality of second navigator sequences for collecting a plurality of second data including respiratory information from a region and a plurality of data acquisition segments for collecting a plurality of imaging data of the imaging region When,
Based on the first data, the signal value of the first respiratory signal of the subject during the first scan is obtained, and based on the second data, the subject value during the second scan is determined. Means for determining the signal value of the second respiratory signal,
Window setting means for setting a window representing a range of signal values for executing the data acquisition segment based on the signal value of the first respiratory signal;
First determining means for determining whether the signal value of the second respiratory signal is included in the window,
Trigger generating means for generating a trigger for executing each of the plurality of second navigator sequences based on a heartbeat signal including heartbeat information of the subject;
A control unit that controls the scanning unit so that the second navigator sequence is executed based on the trigger, and is obtained by a second navigator sequence of one of the plurality of second navigator sequences. If it is determined that the signal value of the acquired second respiration signal is included in the window, one of the plurality of data acquisition segments is detected before the next second navigator sequence is executed. A control unit for controlling the scanning means so that a data acquisition segment is executed;
After the one data acquisition segment is executed and before the next data acquisition segment is executed, the one data acquisition segment is executed and then necessary for T1 recovery of the tissue in the imaging region. Second determining means for determining whether or not the first time has elapsed,
Have
The control unit is
The next data acquisition segment is not executed until it is determined that the first time has elapsed, and the signal value of the second respiratory signal is determined after it is determined that the first time has elapsed. The second navigator sequence is executed until it is determined to be included in the window, and when it is determined that the signal value of the second respiratory signal is included in the window, the next data acquisition segment is performed. Is a magnetic resonance apparatus for controlling the scanning means so that

A second aspect of the present invention is a magnetic field for performing a first scan for obtaining respiratory information from a first region of a subject and a second scan for obtaining an image of the imaged region of the subject. A resonance device,
Setting means for setting a plurality of slices in the imaging region,
Grouping means for dividing the plurality of slices into a plurality of groups,
In the first scan, a plurality of first navigator sequences for collecting a plurality of first data including respiratory information from the first region are executed, and in the second scan, the first navigator sequence is executed. A scan performing a plurality of second navigator sequences for collecting a plurality of second data including respiratory information from a site and a plurality of data acquisition segments for acquiring a plurality of imaging data for each group. Means and
Based on the first data, the signal value of the first respiratory signal of the subject during the first scan is obtained, and based on the second data, the subject value during the second scan is determined. Means for determining the signal value of the second respiratory signal,
Window setting means for setting a window representing a range of signal values for executing the data acquisition segment based on the signal value of the first respiratory signal;
First determining means for determining whether the signal value of the second respiratory signal is included in the window,
Trigger generating means for generating a trigger for executing each of the plurality of second navigator sequences based on a heartbeat signal including heartbeat information of the subject;
A control unit that controls the scanning unit so that the second navigator sequence is executed based on the trigger, and is obtained by a second navigator sequence of one of the plurality of second navigator sequences. If it is determined that the signal value of the acquired second respiratory signal is included in the window, the data of one of the plurality of data acquisition segments is determined before executing the next second navigator sequence. A control unit for controlling the scanning means so that the acquisition segment is executed;
After the one data acquisition segment for collecting the imaging data of the first group of the plurality of groups is executed, the next data acquisition segment for collecting the imaging data of the first group is performed. Before execution, determining whether the first time required to T1 recover tissue in slices included in the first group has elapsed since the one data acquisition segment was executed. Second determining means for
The control unit is
The next data acquisition segment is not executed until it is determined that the first time has elapsed, and the signal value of the second respiratory signal is determined after it is determined that the first time has elapsed. The second navigator sequence is executed until it is determined to be included in the window, and when it is determined that the signal value of the second respiratory signal is included in the window, the next data acquisition segment is performed. Is a magnetic resonance apparatus for controlling the scanning means so that

  The second navigator sequence is executed in synchronization with the heartbeat signal. Then, when it is determined that the signal value of the second respiratory signal obtained by the second navigator sequence is included in the window, the data acquisition segment is executed. Therefore, it is possible to perform imaging using both heartbeat synchronization and respiratory synchronization.

  Also, after the data collection segment is executed, the next data collection segment is not executed until it is determined that the first time required for the T1 recovery has elapsed, and the first data required for the T1 recovery is not executed. After it is determined that the time of 1 has elapsed, the second sequence is executed until it is determined that the signal value of the second respiratory signal is included in the window. Then, when it is determined that the signal value of the second respiratory signal is included in the window, the next data acquisition segment is executed. Therefore, after the T1 recovery, the next data acquisition segment is executed, so that a high quality image can be obtained.

It is a schematic diagram of the magnetic resonance device of the 1st form of the present invention. It is explanatory drawing of the means implement | achieved by the processing apparatus 9. It is explanatory drawing of the scan performed by a 1st form. It is a figure which shows the flow for imaging a liver. It is a figure which shows roughly an example of the image LD acquired by the localizer scan LS. It is a figure which shows the navigator area | region R1 roughly. It is explanatory drawing of pre-scan PS. It is a figure which shows an example of the window W. It is explanatory drawing of the example which performs the main scan MS by a method different from the method of a 1st form. It is explanatory drawing of the main scan MS in a 1st form. Is an illustration of a data acquisition segments _C 1 -C _W. It is a figure which shows the flow of the process performed in the main scan MS of a 1st form. It is a figure which shows the example which performed the navigator sequence before it determines with the time required for T1 recovery having passed. It is a figure which shows an example of another time H '. It is explanatory drawing of the processing apparatus 9 of a 2nd form. It is a figure which shows roughly slice # 1- # 2m set to the liver. It is a figure which shows the slice divided into groups. It is explanatory drawing of the main scan MS in a 2nd form. It is explanatory drawing of a data collection segment. It is a figure which shows the flow of the process performed in the main scan MS of a 2nd form.

  Hereinafter, modes for carrying out the invention will be described, but the present invention is not limited to the following modes.

(1) First Mode FIG. 1 is a schematic diagram of a magnetic resonance apparatus according to a first mode of the present invention.
A magnetic resonance apparatus (hereinafter referred to as “MR apparatus”; MR: Magnetic Resonance) 1 includes a magnet 2, a table 3, a receiving coil 4, and the like.

  The magnet 2 has an accommodation space 21 in which the subject 15 is accommodated. Further, the magnet 2 has a superconducting coil 22, a gradient coil 23, and an RF coil 24. The superconducting coil 22 applies a static magnetic field, the gradient coil 23 applies a gradient pulse, and the RF coil 24 transmits an RF pulse. A permanent magnet may be used instead of the superconducting coil 22.

  The table 3 has a cradle 3a for carrying the subject 15. The subject 15 is transported to the accommodation space 21 by the cradle 3a.

  The receiving coil 4 is attached from the chest of the subject 15 to the abdomen and receives a magnetic resonance signal from the subject 15.

  The MRI apparatus 100 further includes a control unit 5, a transmitter 6, a gradient magnetic field power supply 7, a receiver 8, a processing device 9, a storage unit 10, an operation unit 11, a display unit 12, a signal processing unit 13, and the like. There is.

  The control unit 5 receives, from the processing device 9, data including waveform information of RF pulses and gradient pulses used in the sequence, application timing, and the like. Then, the control unit 5 controls the transmitter 6 based on the RF pulse data, and controls the gradient magnetic field power supply 7 based on the gradient pulse data. The control unit 5 also controls the movement of the cradle 3a. In FIG. 1, the control unit 5 controls the transmitter 6, the gradient magnetic field power supply 7, the cradle 3a, and the like, but the transmitter 6, the gradient magnetic field power supply 7, the cradle 3a, and the like are controlled by a plurality of control units. You may go in. For example, a control unit that controls the transmitter 6 and the gradient magnetic field power supply 7 and a control unit that controls the cradle 3a may be separately provided.

The transmitter 6 supplies a current to the RF coil 24 based on the data received from the control unit 5.
The gradient magnetic field power supply 7 supplies a current to the gradient coil 23 based on the data received from the control unit 5.

  The receiver 8 performs processing such as detection on the magnetic resonance signal received by the receiving coil 4 and outputs the processed signal to the processing device 9. The combination of the magnet 2, the receiving coil 4, the transmitter 6, the gradient magnetic field power supply 7, and the receiver 8 corresponds to the scanning means.

  A pulse wave sensor 14 is attached to the subject 15. The pulse wave sensor 14 detects heartbeat information of the subject 15 and outputs an analog signal including the heartbeat information to the signal processing unit 13. The signal processing unit 13 executes signal processing such as AD conversion for converting an analog signal into a digital signal, and outputs a pulse wave signal including heartbeat information to the processing device 9.

  The processing device 9 transmits various information to the control unit 5 and the display unit 12, reconstructs an image based on the signal received from the receiver 8, and implements various operations of the MR device 100. , And controls the operation of each part of the MR device 100. The storage unit 10 stores programs executed by the control unit 5 and the processing device 9. The storage unit 10 may be a non-transitory storage medium such as a hard disk or a CD-ROM. The processing device 9 reads a program stored in the storage unit 10 and operates as a processor that executes the process described in the program. The processing device 9 realizes various means by executing the processing described in the program. FIG. 2 is an explanatory diagram of means realized by the processing device 9.

The image generating means 91 generates an image based on the data obtained by the scan described later.
The region setting means 92 sets the navigator region R1 (see FIG. 6) for detecting the movement of the lung side edge of the liver.
The range setting means 93 sets an imaging range R2 (see FIG. 6) that represents the range of the imaging region of the subject.
The profile generation unit 94 generates a profile F (see FIG. 7) that represents the relationship between each position in the SI (Superior-Inferior) direction in the navigator region R1 and the signal strength.
The position detection means 95 detects the position of the lung side edge of the liver based on the profile generated by the profile generation means 94. The position detection unit 95 obtains the detected edge position as the signal value of the respiratory signal. The position detecting means 95 corresponds to a means for obtaining a signal value.
The window setting means 96 sets the window W (see FIG. 8). The window W will be described later.
The initial value setting means 97 initializes the subscript _{i of} the data collection segment C _i (see FIG. 11), that is, sets i = 1. The data collection segment C _i will be described later.
The i-value determination means 98 determines whether i> 1 or i = 1.
The peak detecting means 99 detects the peak of the pulse wave signal.
The trigger generating means 100 generates a trigger for executing the navigator sequence and the data acquisition segment.
The signal value determination means 101 determines whether or not the signal value obtained by the navigator sequence is in the window W. The signal value determination means 101 corresponds to the first determination means.
The data collection determination means 102 determines whether or not all the data in the k space necessary for image reconstruction has been collected.
The increment means 103 increments i.
The time determination means 104 determines whether or not the time required for T1 recovery of the tissue within the imaging range R2 (see FIG. 6) has elapsed since the i−1th data acquisition segment C _i−1 was executed. To judge. The time determination means 104 corresponds to the second determination means.

The MR device 1 includes a computer including a processing device 9. The processing device 9 realizes the image generation unit 91 to the time determination unit 104 and the like by reading the program stored in the storage unit 10. The processing device 9 may implement the image generation unit 101 to the time determination unit 104 by one processor, or may implement the image generation unit 101 to the time determination unit 104 by two or more processors. . Further, a part of the image generation unit 101 to the time determination unit 104 may be allowed to be executed by the control unit 5. The program executed by the processing device 9 may be stored in one storage unit or may be stored separately in a plurality of storage units.
Returning to FIG. 1, the description will be continued.

The operation unit 11 inputs various commands to the processing device 9 according to the operation of the operator. The display unit 12 displays various information.
The MR device 1 is configured as described above.

FIG. 3 is an explanatory diagram of the scan executed in the first mode.
In the first mode, the localizer scan LS, the prescan PS, and the main scan MS are executed. These scans will be described below.

  The localizer scan LS is a scan for acquiring an image used for setting the navigator region R1 (see FIG. 6) and the like.

  The pre-scan PS is a scan for setting a window W (see FIG. 8) described later. The window will be described later.

  The main scan MS is a scan for acquiring an image of the liver. In the first mode, the main scan MS is a scan for acquiring a T2-weighted image of the liver by using the 3D fast spin echo method.

  The flow when executing the localizer scan LS, the prescan PS, and the main scan MS will be described below.

FIG. 4 is a diagram showing a flow for photographing the liver.
In step ST1, the localizer scan LS (see FIG. 3) is executed. The image generation unit 91 (see FIG. 2) generates an axial image, a sagittal image, and a coronal image based on the data obtained by the localizer scan LS. FIG. 5 is a diagram schematically showing an example of the image LD acquired by the localizer scan LS. A coronal image is shown in FIG. After executing the localizer scan LS, the process proceeds to step ST2.

  In step ST2, scan conditions are set. For example, a navigator area for detecting the movement of the lung side edge of the liver is set. FIG. 6 schematically shows the navigator region R1 set to detect the movement of the lung side edge 15a of the liver. The operator operates the operation unit 11 and inputs information necessary for setting the navigator region R1 with reference to the image LD. The area setting means 92 (see FIG. 2) sets the navigator area R1 based on the input information.

  The shooting range R2 is also set. The operator operates the operation unit 11 and inputs information necessary for setting the photographing range R2 with reference to the image LD. The range setting means 93 (see FIG. 2) sets the shooting range R2 based on the input information. In the first mode, since the imaging region is the liver, the imaging range R2 is set so that the entire liver is included. After setting the scan conditions, the process proceeds to step ST3.

In step ST3, the prescan PS is executed.
FIG. 7 is an explanatory diagram of the prescan PS.
The pre-scan PS is executed to obtain respiratory information of the subject. Specifically, in the prescan PS, the navigator sequence N for detecting the movement of the edge 15a of the liver is repeatedly executed. The navigator sequence N is, for example, a pencil beam type navigator sequence. The control unit 5 (see FIG. 1) sends the RF pulse data included in the navigator sequence N to the transmitter 6, and sends the gradient pulse data included in the navigator sequence N to the gradient magnetic field power supply 7. The transmitter 6 supplies a current to the RF coil 24 based on the data received from the control unit 5, and the gradient magnetic field power supply 7 supplies a current to the gradient coil 23 based on the data received from the control unit 5. Therefore, the RF coil 24 applies the RF pulse, and the gradient coil 23 applies the gradient pulse. By executing the navigator sequence N, an MR signal for detecting the movement of the edge 15a of the liver is generated from the navigator region R1 (see FIG. 6). This MR signal is received by the receiving coil 4 (see FIG. 1). The receiving coil 4 receives the MR signal and outputs an analog signal containing the information of the MR signal. The receiver 8 performs signal processing such as detection on the signal received from the receiving coil 4 and outputs the data obtained by the signal processing to the processing device 9.

In the processing device 9, the profile generation means 94 (see FIG. 2) Fourier-transforms the received data to generate the profile F. The horizontal axis of the profile F represents each position in the SI direction within the navigator region R1, and the vertical axis represents the signal strength at each position. The navigator sequence N is designed so that the liver has a high signal. Therefore, the liver side of profile F has a high signal. On the other hand, since the lung contains air, the signal on the lung side is low. Therefore, in the profile F, the signal intensity rapidly changes between the lung and the liver. The position detecting means 95 (see FIG. 2) detects the position where the signal intensity changes abruptly as the position of the lung side edge 15a of the liver. In FIG. 7, the position of the edge 15a of the liver is indicated by z _a , z _b , z _c , ... Z _d . In the first mode, the detected edge positions z _a , z _b , z _c , ... Z _d are used as the signal values of the respiratory signal S _res . Therefore, by executing the pre-scan PS, the respiratory signal S _res of the subject 15 can be obtained.
After executing the prescan PS, the process proceeds to step ST4.

In step ST4, the window setting means 96 (see FIG. 2) sets the window W based on the signal value of the respiratory signal S _res . FIG. 8 shows an example of the window W. The window W represents a range of signal values for executing the data acquisition segments C _{1 to} C _W (see FIG. 10 described later) in the main scan MS. Below, an example of a method of setting the window W will be briefly described.

The window setting unit 96 specifies the position Pex of the edge 15a of the liver when the subject 15 _finishes exhaling from the respiratory signal S _res . While the subject 15 is exhaling, the position of the edge 15a moves in the S direction (see FIG. 6), but when the subject 15 begins to inhale, the position of the edge 15a is in the I direction (see FIG. 6). Start moving to. Therefore, by detecting the maximum value of the respiratory signal S _res , the position Pex of the edge 15a when the subject 15 has finished exhaling can be specified. After specifying the position Pex, the window setting means 96 sets a certain range for the position Pex as the window W. How the window W is used when executing the main scan MS will be described later. After setting the window W, the process proceeds to step ST5.

  In step ST5, the main scan MS is executed. The imaged part of the main scan MS is the liver. The liver is an organ that moves by breathing. Further, the left lobe of the liver is close to the heart, and therefore moves by the pulsation of the heart. Therefore, the liver is an organ that is affected by the respiration and pulsation of the subject. Therefore, in the main scan MS, the sequence is executed using both respiratory synchronization and heartbeat synchronization. Hereinafter, the main scan MS in which the sequence is executed using both respiratory synchronization and heartbeat synchronization will be described. In the description of the main scan MS, an example in which the main scan MS is executed by a method different from the method of the first mode will be described first in order to clarify the effect of the first mode. Then, a problem that occurs when the main scan MS is executed by another method is clarified, and then a method of executing the main scan MS in the first mode will be described.

FIG. 9 is an explanatory diagram of an example of executing the main scan MS by a method different from the method of the first embodiment.
FIG. 9 schematically shows a respiratory signal and a pulse wave signal of the subject 15 during the main scan MS. Further, under the pulse wave signal, navigator sequence N1~Nx and data acquisition segments C ₁ -C _X is performed during the scanning MS is schematically shown.

Each of the navigator sequences N1 to Nx is a sequence for detecting the position of the edge of the liver of the subject 15, and has the same sequence chart as the navigator sequence N shown in FIG. Each of the data acquisition segments C _{1 to} C _X is a segment executed to acquire imaging data of the imaging range R2 (see FIG. 6).

In FIG. 9, first, the navigator sequence N1 is executed in synchronization with the peak P1 of the pulse wave signal, and immediately after the navigator sequence N1, the data acquisition segment C ₁ for acquiring the imaging data of the imaging range R2 is executed. . Similarly, every time the peak of the pulse wave signal occurs, the navigator sequence and the data acquisition segment are executed. 9, an example of navigator sequence N1~Nx and data acquisition segments C ₁ -C _X is executed in synchronization with the peak of the pulse wave signal is shown.

  Each time the navigator sequence is executed, the position of the edge of the liver is detected based on the data obtained by the navigator sequence. In FIG. 9, signal values representing the positions of the edges of the liver detected by the navigator sequences N1 to Nx are indicated by z1 to zx. In the method shown in FIG. 9, it is determined whether or not each of the signal values z1 to zx is in the window W. If the signal value falls within the window W, the k-space data obtained by the data acquisition segment is accepted as data for image reconstruction. On the other hand, when the signal value does not fall within the window W, the k-space data obtained by the data acquisition segment is not accepted as image reconstruction data and is discarded. If the data is discarded, the data is recaptured until it is determined that the signal value has fallen within the window W. Therefore, only the k-space data obtained when the signal value enters the window W is accepted as data for image reconstruction, so that an image with reduced body motion artifacts can be obtained.

  However, in the first embodiment, it is considered to perform the scan for acquiring the T2-weighted image. When obtaining a T2-weighted image, it is necessary to execute the next data acquisition segment after the data acquisition segment has been executed and the tissue within the imaging range R2 has sufficiently recovered in T1. Therefore, when performing a scan to acquire a T2-weighted image, the time interval TW between a data acquisition segment and the next data acquisition segment should be as long as possible. For example, it is necessary to set TW = about 2 seconds. However, in the method of FIG. 9, the data acquisition segment is executed each time the peak of the pulse wave signal occurs. Therefore, the time interval TW from the execution of the data collection segment to the execution of the next data collection segment is a value of about TW = 0.8 to 1.2 seconds. Therefore, in the method of FIG. 9, the next data acquisition segment is executed after the data acquisition segment is executed and before each tissue in the imaging range R2 is fully recovered by T1, so that the T2 value of each tissue is calculated. There is a problem that it is difficult to obtain a high-quality T2-weighted image that reflects the difference.

  Therefore, in the first embodiment, the main scan MS is executed so that a high-quality T2-weighted image can be obtained. The method of executing the main scan MS in the first mode will be described below.

FIG. 10 is an explanatory diagram of the main scan MS in the first mode.
FIG. 10 schematically shows the respiratory signal and the pulse wave signal of the subject 15 during the main scan MS. Further, under the pulse wave signal, navigator sequence N1~Nv and data acquisition segments C ₁ -C _W performed during the scan MS is schematically shown.

Each of the navigator sequences N1 to Nv is a sequence for detecting the position of the edge of the liver of the subject 15, and has the same sequence chart as the navigator sequence N shown in FIG. Each of the data acquisition segments C _{1 to} C _W is a segment executed to acquire imaging data of the imaging range R2. The data collection segment will be described below.

FIG. 11 is an explanatory diagram of the data collection segments C _{1 to} C _W.
In FIG. 11, one of the data collection segments C ₁ , C ₂ , C ₃ , ..., C _W is represented by C _i . The subscript _i of C _i represents any value from 1 to w. Thus, for example, if i = 1, the data collection segment C _i represents the data collection segment C ₁ , and if i = w, the data collection segment C _i represents the data collection segment C _W.

In the first embodiment, the data acquisition segment C _i is an imaging sequence IS for acquiring imaging data of the imaging range R2 (imaging region) using the 3D FSE (fast spin echo) method. The imaging data represents data of a partial area of k space. Therefore, by executing the data collection segment C _i once, the data of a partial region of the k space is collected. In the first embodiment, by executing the data acquisition segments C _{1 to} C _W , it is possible to obtain data of the entire region of the k space necessary for image reconstruction of the imaging range R2 (imaging region).

  Next, with reference to FIG. 12 together with FIG. 10, how the main scan MS is executed in step ST5 will be described.

FIG. 12 is a diagram showing a flow of processing executed in the main scan MS.
In step ST51, the initial value setting means 97 (see FIG. 2) initializes the subscript _i of the data collection segment C _i . That is, the initial value setting means 97 sets i = 1. After setting i = 1, the process proceeds to step ST52.

  In step ST52, the i-value determination means 98 (see FIG. 2) determines whether i> 1 or i = 1. If i> 1, the process proceeds to step ST57, while if i = 1, the process proceeds to step ST53. Since i = 1 here, the process proceeds to step ST53.

  In step ST53, the timing of the peak of the pulse wave signal is awaited. The signal processing unit 13 (see FIG. 1) receives an analog signal including heartbeat information from the pulse wave sensor 14, performs signal processing such as AD conversion for converting the analog signal into a digital signal, and the pulse wave including heartbeat information. The signal is transmitted to the processing device 9. In the processing device 9, the peak detecting means 99 (see FIG. 2) detects the peak of the pulse wave signal based on the digital signal received from the signal processing unit 13. In FIG. 10, the peak P1 occurs at the time point t1. Therefore, the peak detecting means 99 detects the peak P1 at the time point t1. When the peak is detected, the process proceeds to step ST54.

  In step ST54, the trigger generation means 100 (see FIG. 2) generates a trigger for executing the navigator sequence N1 in synchronization with the peak P1 detected by the peak detection means 99. When the trigger is generated, the control unit 5 sends the RF pulse data included in the navigator sequence N1 to the transmitter 6, and sends the gradient pulse data included in the navigator sequence N1 to the gradient magnetic field power supply 7. . The transmitter 6 supplies a current to the RF coil 24 based on the data received from the control unit 5, and the gradient magnetic field power supply 7 supplies a current to the gradient coil 23 based on the data received from the control unit 5. Therefore, since the RF coil 24 applies the RF pulse and the gradient coil 23 applies the gradient pulse, the navigator sequence N1 is executed. By executing the navigator sequence N1, an MR signal for detecting the movement of the edge 15a of the liver is generated from the navigator region R1 (see FIG. 6). This MR signal is received by the receiving coil 4 (see FIG. 1). The receiving coil 4 receives the MR signal and outputs an analog signal containing the information of the MR signal. The receiver 8 performs signal processing such as detection on the signal received from the receiving coil 4 and outputs the data obtained by the signal processing to the processing device 9.

  In the processing device 9, the profile generation means 94 Fourier transforms the received data. Therefore, it is possible to generate the profile F (not shown) representing the relationship between each position in the SI region (Z direction) in the navigator region R1 and the signal intensity. After generating the profile F, the process proceeds to step ST55.

  In step ST55, the position detecting means 95 detects the position z1 of the edge of the liver when the navigator sequence N1 is executed, based on the profile F. The detected liver edge position z1 represents the signal value z1 of the respiratory signal when the navigator sequence N1 is executed in the main scan MS. After detecting the signal value (position of the edge of the liver) z1 of the respiratory signal, the process proceeds to step ST56.

In step ST56, the signal value determination means 101 (see FIG. 2) determines whether or not the signal value z1 is within the window W. If the signal value z1 falls within the window W, this means it is time to execute the _first data acquisition segment C ₁ . Therefore, when it is determined that the signal value z1 is within the window W, the process proceeds to step ST59.

On the other hand, if the signal value z1 does not fall within the window W, this means that it is not the time when the _first data acquisition segment C ₁ can be executed. Therefore, when it is determined that the signal value z1 is not within the window W, the process returns to step ST53. Here, the signal value z1 does not fall within the window W. Therefore, the process returns to step ST53.

  In step ST53, the timing of the peak of the pulse wave signal is awaited. In FIG. 10, the peak P2 occurs at the time point t2. Therefore, the peak detecting means 99 detects the peak P2 at the time point t2. When the peak is detected, the process proceeds to step ST54.

  In step ST54, the trigger generating means 100 generates a trigger for executing the navigator sequence N2 in synchronization with the peak P2 detected by the peak detecting means 99. When the trigger is generated, the control unit 5 sends the data of the RF pulse included in the navigator sequence N2 to the transmitter 6 and the data of the gradient pulse included in the navigator sequence N2 to the gradient magnetic field power supply 7. . Therefore, the navigator sequence N2 is executed. The data obtained by executing the navigator sequence N2 is output to the processing device 9.

  In the processing device 9, the profile generation means 94 Fourier transforms the received data. Therefore, it is possible to generate the profile F (not shown) representing the relationship between each position in the SI region (Z direction) in the navigator region R1 and the signal intensity. After generating the profile F, the process proceeds to step ST55.

  In step ST55, the position detection means 95 detects the position z2 of the edge of the liver when the navigator sequence N2 is executed, based on the profile F. The detected liver edge position z2 represents the signal value z2 of the respiratory signal when the navigator sequence N2 is executed in the main scan MS. After detecting the signal value (the position of the edge of the liver) z2 of the respiratory signal, the process proceeds to step ST56.

  In step ST56, the signal value determination means 101 determines whether or not the signal value z2 is within the window W. Here, since the signal value z2 is not within the window W, the process returns to step ST53 again.

Similarly, in step ST56, the loop of steps ST53, ST54, ST55, and ST56 is repeatedly executed until it is determined in step ST56 that the signal value of the respiratory signal (the position of the edge of the liver) is within the window W. In the first embodiment, the signal value (the position of the edge of the liver) z3 of the respiratory signal when the navigator sequence N3 is executed is in the window W. Therefore, in step ST56, the signal value determination means 101 determines that the signal value z3 of the respiratory signal is within the window W. This means that it is the timing when the _first data acquisition segment C ₁ can be executed, so the process proceeds to step ST59.

In step ST59, the trigger generating means 100 generates a trigger for executing the data acquisition segment C _i . When the trigger is generated, the control unit 5 sends the data of the RF pulse included in the data acquisition segment C _i to the transmitter 6 and changes the data of the gradient pulse included in the data acquisition segment C _i into the gradient magnetic field. Send to power supply 7. The transmitter 6 supplies a current to the RF coil 24 based on the data received from the control unit 5, and the gradient magnetic field power supply 7 supplies a current to the gradient coil 23 based on the data received from the control unit 5. Therefore, the data collection segment C _i is executed. Since i = 1 here, the data collection segment to be executed is indicated by “C ₁ ”. The data acquisition segment C ₁ is executed immediately after the navigator sequence N3. By executing the data acquisition segment C ₁ , the imaging data of the imaging range R2 is acquired. After executing the data acquisition segment C ₁ , the process proceeds to step ST60.

  In step ST60, the data collection determination unit 102 (see FIG. 2) determines whether or not all the k-space data necessary for image reconstruction has been collected. If all the data has been collected, the flow ends, and if all the data has not been collected yet, the process proceeds to step ST61. Here, since all the data have not been collected yet, the process proceeds to step ST61.

  In step ST61, the increment means 103 (see FIG. 2) increments i. Here, it is incremented from i = 1 to i = 2. After incrementing i, the process returns to step ST52.

  In step ST52, the i value determination means 98 determines whether i> 1 or i = 1. Here, since i = 2 is set in step ST61, i> 1. Therefore, the process proceeds to step ST57.

  In step ST57, the timing of the peak of the pulse wave signal is awaited. In FIG. 10, the peak P4 occurs at the time point t4. Therefore, the peak detecting means 99 detects the peak P4 at the time point t4. When the peak is detected, the process proceeds to step ST58.

In step ST58, the time determining unit 104 (see FIG. 2) has elapsed time from the execution of the _i− 1th data acquisition segment C _i−1 to the time required for T1 recovery of the tissue within the imaging range R2. It is determined whether or not. Here, since i = 2 is set, the time determination means 104 has elapsed the time required for T1 recovery of the tissue in the imaging range R2 from the execution of the _first data acquisition segment C _1. It is determined whether or not. The reason for determining whether or not T1 has recovered is explained below.

The imaging sequence IS (see FIG. 11) executed in the first mode is a sequence for obtaining a T2-weighted image. In the case of obtaining a T2-weighted image, after the i-1th data acquisition segment C _i-1 is executed, the next i-th data acquisition segment C _i is acquired before the tissue in the imaging range R2 is sufficiently recovered in T1. If it is executed, there is a problem that it is not possible to obtain a high-quality T2-weighted image that reflects the difference in T2 value of each tissue. Therefore, in the first embodiment, before the i (> 1) th data collection segment C _i is executed, the tissue of the imaging range R2 is determined after the i−1th data collection segment C _i-1 is executed. It is determined whether or not the time required to recover T1 has elapsed.

Several methods are conceivable as a method for determining whether or not the time required for T1 recovery of the tissue in the imaging range R2 has elapsed. In the first embodiment, the time determination means 104, from the execution start time of the executed navigator sequence immediately before the i-1 th data acquisition segments C _i-1, i-1 th data acquisition segments C _i-1 The time H up to the point of occurrence of the peak of the pulse wave signal detected after is calculated, and this time H is compared with a predetermined time H0. The predetermined time H0 is a reference time for determining whether or not the time required for T1 recovery has elapsed, and H0 is, for example, H0 = 2 seconds. The time determination means 104 determines whether or not the time required for T1 recovery has elapsed based on the comparison result of the time H and the predetermined time H0. Here, since i = 2, the time determination means 104 starts after the first data collection segment C ₁ from the execution start time t31 of the navigator sequence N3 executed immediately before the first data collection segment C ₁ . The time H = H1 until the time point t4 at which the peak P4 of the detected pulse wave signal is generated is calculated. When the time H1 is equal to or greater than the predetermined time H0 (H1 ≧ H0), the time determination means 104 determines that the time required for T1 recovery has elapsed, while the time H1 is less than the predetermined time H0. (H1 <H0), it is determined that the time required for T1 recovery has not elapsed. Here, H1 <H0. Therefore, since it is determined that the time required for T1 recovery has not elapsed since the data collection segment C ₁ was executed, the process returns to step ST57.

  In step ST57, the timing of the peak of the pulse wave signal is awaited. In FIG. 10, a peak P5 occurs at time t5. Therefore, the peak detecting means 99 detects the peak P5 at the time point t5. When the peak is detected, the process proceeds to step ST58.

In step ST58, the time determination means 104 determines whether or not the time required for T1 recovery of the tissue within the imaging range R2 has elapsed since the execution of the _first data acquisition segment C ₁ .

  The time determination means 104 calculates the time H2 from the execution start time t31 of the navigator sequence N3 to the occurrence time t5 of the peak P5 of the pulse wave signal, and compares this time H2 with a predetermined time H0. When H2 ≧ H0, it is determined that the time required for T1 recovery has elapsed, and when H2 <H0 or less, it is determined that the time required for T1 recovery has not elapsed. Here, H2 <H0. Therefore, the process returns to step ST57 again.

  Similarly, in step ST58, the loop of steps ST57 and ST58 is repeatedly executed until it is determined in step ST58 that the time required for T1 recovery has elapsed. Since the peak P6 occurs after the peak P5, the time determination means 104 calculates the time H3 from the execution start time t31 of the navigator sequence N3 to the occurrence time t6 of the pulse wave signal peak P6. Then, the time determination means 104 compares the time H3 with the predetermined time H0. Here, H3 ≧ H0. Therefore, it is determined that the time required for T1 recovery has elapsed, and the process proceeds to step ST54.

  In step ST54, the trigger generating means 100 generates a trigger for executing the navigator sequence N4 in synchronization with the peak P6 detected by the peak detecting means 99. When the trigger is generated, the control unit 5 sends the data of the RF pulse included in the navigator sequence N4 to the transmitter 6 and the data of the gradient pulse included in the navigator sequence N4 to the gradient magnetic field power supply 7. . Therefore, the navigator sequence N4 is executed. A profile F (not shown) is generated based on the data obtained by executing the navigator sequence N4. After generating the profile F, the process proceeds to step ST55.

  In step ST55, the position detecting means 95 detects the position z4 of the edge of the liver when the navigator sequence N4 is executed, based on the profile F. The detected liver edge position z4 represents the signal value z4 of the respiratory signal when the navigator sequence N4 is executed in the main scan MS. After detecting the signal value (position of the edge of the liver) z4 of the respiratory signal, the process proceeds to step ST56.

  In step ST56, the signal value determination means 101 determines whether or not the signal value z4 is within the window W. Here, since the signal value z4 is not within the window W, the process returns to step ST53 again.

  In step ST53, the timing of the peak of the pulse wave signal is awaited. In FIG. 10, the peak P7 occurs at the time point t7. Therefore, the peak detecting means 99 determines that the peak P7 has occurred at the time point t7. If it is determined that a peak has occurred, the process proceeds to step ST54.

  In step ST54, the navigator sequence N5 is executed in synchronization with the peak P7. Then, the profile F (not shown) is generated based on the data obtained by executing the navigator sequence N5. After generating the profile F, the process proceeds to step ST55.

  In step ST55, the position detecting means 95 detects the position z5 of the edge of the liver when the navigator sequence N5 is executed, based on the profile F. The detected liver edge position z5 represents the signal value z5 of the respiratory signal when the navigator sequence N5 is executed in the main scan MS. After detecting the signal value (the position of the edge of the liver) z5 of the respiratory signal, the process proceeds to step ST56.

  In step ST56, the signal value determination means 101 determines whether or not the signal value z5 is within the window W. Here, since the signal value z5 is not within the window W, the process returns to step ST53 again.

  Similarly, in step ST56, the loop of steps ST53, ST54, ST55, and ST56 is repeatedly executed until it is determined in step ST56 that the signal value of the respiratory signal (the position of the edge of the liver) is within the window W. In the first embodiment, the window W contains the signal value (the position of the edge of the liver) z7 of the respiratory signal when the navigator sequence N7 is executed. Therefore, in step ST56, the signal value determination means 101 determines that the signal value z7 of the respiratory signal is within the window W. When it is determined that the signal value z7 of the respiratory signal is within the window W, the process proceeds to step ST59.

In step ST59, the trigger generating means 100 generates a trigger for executing the data acquisition segment C _i for acquiring the imaging data of the imaging range R2. Since i = 2 here, the data collection segment C ₂ is executed. Data collection segment C ₂ is performed immediately after the navigator sequence N7. By executing the data collection segment C _2, the imaging data of the imaging range R2 is collected. After executing the data acquisition segment C ₂ , the process proceeds to step ST60.

  In step ST60, the data collection determination unit 102 determines whether or not all the k-space data necessary for image reconstruction has been collected. Here, since all the data have not been collected yet, the process proceeds to step ST61.

  In step ST61, the increment means 103 increments i. Here, it is incremented from i = 2 to i = 3. After incrementing i, the process returns to step ST52.

  In step ST52, the signal value determination means 101 determines whether i> 1 or i = 1. Here, since i = 3 is set in step ST61, i> 1. Therefore, the process proceeds to step ST57.

  In step ST57, the timing of the peak of the pulse wave signal is awaited. In FIG. 10, a peak P10 occurs at time t10. Therefore, the peak detecting means 99 detects the peak P10 at the time point t10. When the peak is detected, the process proceeds to step ST58.

In step ST58, the time determination means 104 determines whether or not the time required for T1 recovery of the tissue within the imaging range R2 has elapsed since the i−1th data acquisition segment C _i−1 was executed. judge. Here, since i = 3 is set, the time determination means 104 has elapsed the time required for T1 recovery of the tissue in the imaging range R2 from the execution of the _second data acquisition segment C _2. It is determined whether or not.

  The time determination means 104 calculates the time H4 from the execution start time point t91 of the navigator sequence N7 to the generation time point t10 of the peak P10 of the pulse wave signal, and compares this time H4 with a predetermined time H0. When H4 ≧ H0, it is determined that the time required for T1 recovery has elapsed, and when H4 <H0 or less, it is determined that the time required for T1 recovery has not elapsed. Here, H4 <H0. Therefore, the process returns to step ST57 again.

  Similarly, in step ST58, the loop of steps ST57 and ST58 is repeatedly executed until it is determined in step ST58 that the time required for T1 recovery has elapsed. In FIG. 10, when the time H6 (time from the execution start time t91 of the navigator sequence N7 to the time t12 when the peak P12 of the pulse wave signal is generated) is compared with H0, H6 ≧ H0. Therefore, it is determined that the time required for T1 recovery has elapsed, and the process proceeds to step ST54.

  In step ST54, the trigger generation means 100 generates a trigger for executing the navigator sequence N8 in synchronization with the peak P12 detected by the peak detection means 99. When the trigger is generated, the control unit 5 sends the data of the RF pulse included in the navigator sequence N8 to the transmitter 6 and the data of the gradient pulse included in the navigator sequence N8 to the gradient magnetic field power supply 7. . Therefore, the navigator sequence N8 is executed. A profile F (not shown) is generated based on the data obtained by executing the navigator sequence N8. After generating the profile F, the process proceeds to step ST55.

  In step ST55, the position detecting means 95 detects the position z8 of the edge of the liver when the navigator sequence N8 is executed, based on the profile F. The detected liver edge position z8 represents the signal value z8 of the respiratory signal when the navigator sequence N8 is executed in the main scan MS. After detecting the signal value (the position of the edge of the liver) z8 of the respiratory signal, the process proceeds to step ST56.

  In step ST56, the signal value determination means 101 determines whether or not the signal value z8 is within the window W. Here, since the signal value z8 is not within the window W, the process returns to step ST53.

  In step ST, the timing of the peak of the pulse wave signal is awaited. In FIG. 10, a peak P13 occurs at time t13. Therefore, the peak detecting means 99 determines that the peak P13 has occurred at the time point t13. If it is determined that a peak has occurred, the process proceeds to step ST54.

  In step ST54, the navigator sequence N9 is executed in synchronization with the peak P13. A profile F (not shown) is generated based on the data obtained by executing the navigator sequence N9. After generating the profile F, the process proceeds to step ST55.

  In step ST55, the position detection means 95 detects the position z9 of the edge of the liver when the navigator sequence N9 is executed, based on the profile F. The detected liver edge position z9 represents the signal value z9 of the respiratory signal when the navigator sequence N9 is executed in the main scan MS. After detecting the signal value (the position of the edge of the liver) z9 of the respiratory signal, the process proceeds to step ST56.

  In step ST56, the initial value setting means 97 determines whether or not the signal value z9 is within the window W. Here, since the signal value z9 is not within the window W, the process returns to step ST53.

  Similarly, in step ST56, the loop of steps ST53, ST54, ST55, and ST56 is repeatedly executed until it is determined in step ST56 that the signal value of the respiratory signal (the position of the edge of the liver) is within the window W. In the first embodiment, the signal value (the position of the edge of the liver) z10 of the respiratory signal when the navigator sequence N10 is executed is in the window W. Therefore, in step ST56, the initial value setting means 97 determines that the signal value z10 of the respiratory signal is within the window W. When it is determined that the signal value z10 of the respiratory signal is within the window W, the process proceeds to step ST59.

In step ST59, the trigger generating means 100 generates a trigger for executing the data acquisition segment C _i for acquiring the imaging data of the imaging range R2. Since i = 3 here, the data collection segment C ₃ is executed. Data acquisition segments _{C 3} is performed immediately after the navigator sequence N10. By executing the data acquisition segments C _3, the imaging data of the photographed range R2 is collected. After executing the data acquisition segment C ₃ , the process proceeds to step ST60.

  In step ST60, the data collection determination unit 102 determines whether or not all the k-space data necessary for image reconstruction has been collected. Here, since all the data have not been collected yet, the process proceeds to step ST61.

  In step ST61, the increment means 103 increments i. Here, it is incremented from i = 3 to i = 4. After incrementing i, the process returns to step ST52.

Similarly, in step ST60, the loop of steps ST52 to ST61 is repeatedly executed until it is determined in step ST60 that all the k-space data necessary for image reconstruction of the imaging range R2 has been collected. Here, it is assumed that all the data in the k space is collected by executing the data collection sequence C _W. Therefore, after the data collection sequence C _W is executed in step ST59, it is determined in step ST60 that all data has been collected. The image generation means 91 reconstructs the image of the imaging range R2 based on the data obtained by the data acquisition segments C _{1 to} C _W. In this way, the flow ends.

In the first embodiment, before performing the i th data acquisition segment C _i, from i-1 th data acquisition segments C _i-1 is performed, the required tissue imaging region in order to T1 recovery It is determined whether time has elapsed. When it is determined that the time required for T1 recovery has not elapsed, the i-th data acquisition segment C _i is not executed and the next peak of the pulse wave signal occurs. Then, when the next peak occurs, it is determined again whether or not the time required for T1 recovery has elapsed. If it is determined that the time required for T1 recovery has not elapsed, the i-th data collection segment C Wait for the next peak of the pulse wave signal to occur without executing _i . Therefore, it is possible to prevent the i-th data acquisition segment C _{i from} being executed before the time required for T1 recovery elapses, so that a high-quality T2-weighted image that reflects the difference in T2 value of each tissue is obtained. be able to.

In the first embodiment, the navigator sequence is not executed and it is waited for the peak of the pulse wave signal to occur until it is determined in step ST58 that the time required for T1 recovery has elapsed. However, the navigator sequence may be executed before it is determined that the time required for T1 recovery has elapsed. FIG. 13 is a diagram showing an example in which the navigator sequence is executed before it is determined that the time required for T1 recovery has elapsed. Unlike the main scan MS of FIG. 10, the main scan MS of FIG. 13 executes the navigator sequence in synchronization with each of the peaks P1 to Py of the pulse wave signal. However, in the main scan MS of FIG. 13, since the data acquisition segment C _i is executed at the same timing as the main scan MS of FIG. 10, a high quality image can be obtained.

In the first embodiment, the time H from the execution start time point of the navigator sequence executed immediately before the _i− 1th data acquisition segment C _i−1 to the occurrence time point of the peak of the heartbeat signal is calculated, and the time H is calculated. And a predetermined time H0 are compared with each other to determine whether the time required for T1 recovery has elapsed. However, instead of the time H, another time H ′ may be calculated, and whether or not the time required for T1 recovery has elapsed may be determined based on the comparison result of the time H ′ and the predetermined time H0. Good. FIG. 14 shows an example of another time H '. In FIG. 14, another time H ′ is set to the time from the execution start time point of the i−1th data acquisition sequence C _i−1 to the occurrence time point of the peak of the heartbeat signal. As described above, the time H ′ may be calculated instead of the time H as long as it is possible to determine whether or not the time required for T1 recovery has elapsed. Further, the time H ′ may be, for example, as a different example from FIG. 14, a time from the end of execution of the navigator sequence to the time of occurrence of the peak of the heartbeat signal.

(2) Second Mode The MR device of the second mode is different from the MR device of the first mode in the processing executed by the processing device 9, but the other configurations are the same as those of the first mode. is there. Therefore, with regard to the MR device of the second system, the processing device 9 will be mainly described.

FIG. 15 is an explanatory diagram of the processing device 9 of the second embodiment.
The image generating means 91 generates an image based on the data obtained by scanning.
The area setting means 92 sets the navigator area R1 (see FIG. 16).
The slice setting unit 921 sets a slice (see FIG. 16) on the imaging region.
The grouping unit 922 divides the slices set by the slice setting unit 921 into a plurality of groups.
The profile generation unit 94 generates a profile F that represents the relationship between each position in the SI direction in the navigator region R1 and the signal strength.
The position detection means 95 detects the position of the lung side edge of the liver based on the profile generated by the profile generation means 94. The position detection unit 95 obtains the detected edge position as the signal value of the respiratory signal. The position detecting means 95 corresponds to a means for obtaining a signal value.
The window setting means 96 sets a window W (see FIG. 8) that represents a range of signal values for executing data acquisition segments A _i and B _j described below, based on the signal values of the respiratory signal.
The initial value setting means 97 initializes the subscript _i of the data collection segment A _{i and} the subscript _j of the data collection segment B _j , that is, sets i = 1 and j = 1. The data collection segments A _i and B _j will be described later.
Whether the determination unit 961 collects the imaging data of the group Ga (the even numbered slices # 2 to # 2m) or the imaging data of the group Gb (the odd numbered slices # 1 to # 2m-1). To decide. The groups Ga and Gb will be described later.
The ij value determination means 971 determines whether i> 1 or i = 1, and also determines whether j> 1 or j = 1.
The peak detecting means 99 detects the peak of the pulse wave signal.
The trigger generating means 100 generates a trigger for executing the navigator sequence and the data acquisition segment.
The signal value determination means 101 determines whether or not the signal value obtained by the navigator sequence is in the window W.
The data collection determination means 102 determines whether or not all the data in the k space necessary for image reconstruction has been collected.
The increment means 103 increments i and j.
The time determination unit 104 determines the time required for T1 recovery of the tissue in the even-numbered slices # 2 to # 2m (see FIG. 19) after the i−1th data acquisition segment A _i−1 is executed. Is determined. In addition, the time determination unit 104 restores the tissue in the odd-numbered slices # 1 to # 2m-1 (see FIG. 19) to T1 after the j-1th data acquisition segment B _j-1 is executed. It is determined whether or not the time required for.

  The processing device 9 realizes each unit shown in FIG. 15 by reading the program stored in the storage unit 10. It should be noted that the processing device 9 may realize the plurality of means shown in FIG. 15 by one processor or may be realized by two or more processors. Further, a part of the plurality of means shown in FIG. 15 may be executed by the control unit 5.

  Next, a method of acquiring an image in the second mode will be described with reference to the flow of FIG. 4 as in the first mode.

  In step ST1, the localizer scan LS is executed. The image LD (see FIG. 5) is obtained by executing the localizer scan LS. After executing the localizer scan LS, the process proceeds to step ST2.

  In step ST2, scan conditions are set. Also in the second mode, the navigator region R1 is set as in the first mode. The navigator region R1 is schematically shown in FIG.

  The operator also sets other scan conditions. For example, a slice is set. FIG. 16 schematically shows the set slices # 1 to # 2m. The operator operates the operation unit 11 and inputs information necessary for setting the slices # 1 to # 2m with reference to the image LD. The slice setting means 921 (see FIG. 15) sets slices # 1 to # 2m based on the input information. In the second mode, since the liver is imaged, slices # 1 to # 2m are set in the imaging region including the liver.

The grouping unit 922 (see FIG. 15) divides the slices # 1 to # 2m into a plurality of groups. FIG. 17 is a diagram showing slices divided into groups. In the second mode, the slices # 1 to # 2m are divided into two groups Ga and Gb. The group Ga includes even-numbered slices # 2 to # 2m, while the group Gb includes odd-numbered slices # 1 to # 2m-1. The group Ga is a group whose data is collected in a data collection sequence A _i (see FIG. 19) described later, and the group Gb is a group which is collected in a data collection sequence B _j described later (see FIG. 19). The method of collecting the data of the groups Ga and Gb will be described in detail later. After setting the scan conditions, the process proceeds to step ST3.

  Steps ST3 and ST4 are the same as in the first mode. Therefore, the window W (see FIG. 8) is set. After setting the window W, the process proceeds to step ST5.

In step ST5, the main scan MS is executed. FIG. 18 is an explanatory diagram of the main scan MS.
FIG. 18 schematically shows the respiratory signal and the pulse wave signal of the subject 15 during the main scan MS. Below the pulse wave signal, the navigator sequences N1 to Nt and the data acquisition segments A _{1 to} A _h and B _{1 to} B _h executed during the main scan MS are schematically shown.

The navigator sequences N1 to Nt are sequences for detecting the position of the edge of the liver of the subject 15, and have the same sequence chart as the navigator sequence N shown in FIG. The data acquisition segments A ₁ , A ₂ , A ₃ , ..., A _h are the segments executed to acquire the imaging data of the slices of the group Ga (see FIG. 17), and the data acquisition segments B ₁ , B ₂ , B ₃ , ... B _h are segments executed to collect imaging data of slices of the group Gb (see FIG. 17). The data collection segment will be described below.

FIG. 19 is an explanatory diagram of the data collection segment.
First, the data collection segments A ₁ , A ₂ , A ₃ , ... A _h will be described.

In FIG. 19, one of the data collection segments A ₁ , A ₂ , A ₃ , ... A _h is represented by A _i . The subscript _i of A _i represents any value from 1 to h. Thus, for example, when i = 1, the data collection segment A _i represents the data collection segment A ₁ , and when i = h, the data collection segment A _i represents the data collection segment A _h .

The data acquisition segment A _i includes imaging sequences IS ₂ , IS ₄ , ... IS _2m for acquiring imaging data of even-numbered slices # 2 to # 2m. In the second mode, the imaging sequences IS ₂ , IS ₄ , ... IS _2m are used to collect the imaging data of the diffusion weighted images of the even-numbered slices # 2, # 4, ... # 2m, respectively. It is a 2D sequence. The imaging data acquired by performing each of the imaging sequences IS ₂ , IS ₄ , ... IS _2m represents a portion of the k-space data of the corresponding even numbered slices. For example, the imaging data collected by executing the imaging sequence IS ₂ represents a part of the data in the k space of the even-numbered slice # 2, and the imaging data collected by executing the imaging sequence IS _2m. The data represents a part of the data in the k space of the even-numbered slice # 2m. Therefore, by executing the data acquisition segment A _i once, the data of a partial region of the k-space of each even-numbered slice is acquired. Further, the magnitude of the phase encode gradient pulse of the imaging sequence IS ₂ , IS ₄ , ... IS _2m of the data acquisition segment A _i is set so as to change according to the value of i. In the second mode, by executing the data acquisition segments A _{1 to} A _h , it is possible to obtain the data of the entire region of the k space necessary for the image reconstruction of the even-numbered slices # 2 to # 2m.
Next, the data collection segments B ₁ , B ₂ , B ₃ , ... B _h will be described.

In FIG. 19, one of the data collection segments B ₁ , B ₂ , B ₃ , ... B _h is represented by B _j . The subscript _j of B _j represents any one of 1 to h. Thus, for example, when j = 1, the data collection segment B _j represents the data collection segment B ₁ , and when j = h, the data collection segment B _j represents the data collection segment B _h .

The data acquisition segment B _j includes imaging sequences IS ₁ , IS ₃ , ... IS _2m-1 for acquiring imaging data of odd-numbered slices # 1 to # 2m-1. In the second embodiment, the imaging sequences IS ₁ , IS ₃ , ... IS _2m-1 respectively obtain imaging data of diffusion-weighted images of odd-numbered slices # 1, # 3, ... # 2m-1. 2D sequence to collect. The imaging data acquired by executing each of the imaging sequences IS ₁ , IS ₃ , ... IS _2m−1 represents a portion of the data in the k-space of the corresponding odd numbered slice. For example, the imaging data collected by executing the imaging sequence IS ₁ represents a part of the k-space data of the odd-numbered slice # 1 and is collected by executing the imaging sequence IS _2m−1. Imaging data represents a part of k-space data of odd-numbered slice # 2m-1. Therefore, by executing the data acquisition segment B _j once, the data of a partial region of the k-space of each odd-numbered slice is acquired. Further, the magnitude of the phase encode gradient pulse of the imaging sequences IS ₁ , IS ₃ , ... IS _2m−1 of the data acquisition segment B _j is set so as to change according to the value of j. In the second mode, by executing the data acquisition segments B _{1 to} B _h , it is possible to obtain the data of the entire region of the k space necessary for the image reconstruction of the odd-numbered slices # 1 to # 2m−1. .

In the second mode, the data collection segment A _i and the data collection segment B _j are alternately executed.

  Next, with reference to FIG. 20 together with FIG. 18, how the main scan MS is executed will be described.

FIG. 20 is a diagram showing a flow of processing executed in the main scan MS.
In step ST510, the initial value setting means 97 (see FIG. 15) initializes the subscript _i of the data collection segment A _{i and} the subscript _j of the data collection segment B _j . That is, the initial value setting means 97 sets i = 1 and j = 1. After setting i = 1 and j = 1, the process proceeds to step ST520.

  In step ST520, the determining means 961 (see FIG. 15) collects the imaging data of the group Ga (the even numbered slices # 2 to # 2m) or the group Gb (the odd numbered slices # 1 to # 2m−). 1) Decide whether to collect the imaging data. When it is decided to collect the imaging data of the group Ga (even-numbered slices # 2 to # 2m), the process proceeds to step ST530, while the imaging data of the group Gb (odd-numbered slices # 1 to # 2m-1) is collected. If so, the process proceeds to step ST540. Here, it is assumed that it is determined to collect the imaging data of the group Ga (even-numbered slices # 2 to # 2m). Therefore, the process proceeds to step ST530.

In step ST530, a process for finding the timing for executing the i-th data acquisition segment A _i (a segment for acquiring imaging data of the group Ga) is executed. Here, since i = 1, a process for finding the timing for executing the _first data collection segment A ₁ is executed. Step ST530 has steps ST52a to ST58a. The steps ST52a to ST58a will be described below.

  In step ST52a, the ij value determination means 971 (see FIG. 15) determines whether i> 1 or i = 1. If i> 1, the process proceeds to step ST57a, while if i = 1, the process proceeds to step ST53a. Since i = 1 here, the process proceeds to step ST53a.

Steps ST53a to ST56a are the same as steps ST53 to ST56 of the first embodiment. Therefore, in step ST56a, the loop of steps ST53a, ST54a, ST55a, and ST56a is repeatedly executed until it is determined that the signal value of the respiratory signal (the position of the edge of the liver) is within the window W. In the second embodiment, the signal value (the position of the edge of the liver) z3 of the respiratory signal when the navigator sequence N3 is executed is in the window W. Therefore, in step ST56a, the signal value determination means 101 (see FIG. 15) determines that the signal value z3 of the respiratory signal is within the window W. This means that it is the timing when the _first data acquisition segment A ₁ can be executed, and therefore the process proceeds to step ST550.

In step ST550, the trigger generating means 100 (see FIG. 15) generates a trigger for executing the data acquisition segment A _i . When the trigger is generated, the control unit 5 sends the data of the RF pulse included in the data acquisition segment A _i to the transmitter 6, and changes the data of the gradient pulse included in the data acquisition segment A _i into the gradient magnetic field. Send to power supply 7. The transmitter 6 supplies a current to the RF coil 24 based on the data received from the control unit 5, and the gradient magnetic field power supply 7 supplies a current to the gradient coil 23 based on the data received from the control unit 5. Therefore, the data collection segment A _i is executed. Since i = 1 here, the data collection segment to be executed is indicated by “A ₁ ”. The data acquisition segment A ₁ is executed immediately after the navigator sequence N3. The imaging data of the group Ga (even-numbered slices # 2 to # 2m) is acquired by executing the data acquisition segment A ₁ . After executing the data acquisition segment A ₁ , the process proceeds to step ST570.

  In step ST570, the data collection determination unit 102 (see FIG. 15) determines whether or not all the k-space data necessary for image reconstruction has been collected. If all the data has been collected, the flow ends, and if all the data has not been collected yet, the process proceeds to step ST580. Here, since all the data have not been collected yet, the process proceeds to step ST580.

In step ST580, the increment means 103 (see FIG. 15) increments i or j. When the data collection segment A _i is executed, the increment means 103 increments i, and when the data collection segment B _j is executed, the increment means 103 increments j. Here, since the data collection segment A _i (i = 1) has been executed, the increment means 103 increments i. i is incremented from i = 1 to i = 2. After incrementing i, the process returns to step ST520.

  In step ST520, the determining unit 961 collects the imaging data of the group Ga (slices # 2 to # 2m of even number) or the imaging data of the group Gb (slices # 1 to # 2m-1 of odd number). Decide what to collect. Here, it is determined that the imaging data of the group Gb (the odd-numbered slices # 1 to # 2m-1) is acquired. Therefore, the process proceeds to step ST540.

In step ST540, a process for finding the timing for executing the j-th data acquisition segment B _j (segment for acquiring imaging data of group Gb) is executed. Here, since j = 1, processing for finding the timing for executing the _first data collection segment B ₁ is executed. Step ST540 has steps ST52b to ST58b. The steps ST52b to ST58b will be described below.

  In step ST52b, the ij value determination means 971 determines whether j> 1 or j = 1. If j> 1, the process proceeds to step ST57b, while if j = 1, the process proceeds to step ST53b. Since j = 1 here, the process proceeds to step ST53b.

Steps ST53b to ST56b are the same as steps ST53 to ST56 of the first embodiment. Therefore, in step ST56b, the loop of steps ST53b, ST54b, ST55b, and ST56b is repeatedly executed until it is determined that the signal value of the respiratory signal (the position of the edge of the liver) is within the window W. In the second mode, the signal value (the position of the edge of the liver) z4 of the respiratory signal when the navigator sequence N4 is executed is in the window W. Therefore, in step ST56b, the signal value determination means 101 determines that the signal value z4 of the respiratory signal is within the window W. This means that it is the timing when the _first data collection segment B ₁ can be executed, and therefore the process proceeds to step ST560.

In step ST560, the trigger generating means 100 generates a trigger for executing the data collection segment B _j . When the trigger is generated, the control unit 5 sends the data of the RF pulse included in the data acquisition segment B _j to the transmitter 6, and changes the data of the gradient pulse included in the data acquisition segment B _j into the gradient magnetic field. Send to power supply 7. The transmitter 6 supplies a current to the RF coil 24 based on the data received from the control unit 5, and the gradient magnetic field power supply 7 supplies a current to the gradient coil 23 based on the data received from the control unit 5. Therefore, the data collection segment B _j is executed. Since at this time is j = 1, the data acquisition segments to be executed is indicated by "B _1". The data acquisition segment B ₁ is executed immediately after the navigator sequence N4. By executing the data acquisition segment B ₁ , the imaging data of the group Gb (slices # 1 to # 2m-1 of odd number) is acquired. After executing the data acquisition segment B ₁ , the process proceeds to step ST570.

  In step ST570, the data collection determination unit 102 determines whether or not all the k-space data necessary for image reconstruction has been collected. Here, since all the data have not been collected yet, the process proceeds to step ST580.

In step ST580, the increment means 103 increments i or j. Here, since the data collection segment B _j (j = 1) has been executed, the increment means 103 increments j. j is incremented from j = 1 to j = 2. After incrementing j, the process returns to step ST520.

  In step ST520, the determining unit 961 collects the imaging data of the group Ga (slices # 2 to # 2m of even number) or the imaging data of the group Gb (slices # 1 to # 2m-1 of odd number). Decide what to collect. Here, it is determined that the imaging data of the group Ga (even-numbered slices # 2 to # 2m) is acquired. Therefore, the process proceeds to step ST530.

  In step ST530, first, in step ST52a, the ij value determination means 971 determines whether i> 1 or i = 1. Here, since i = 2, i> 1. Therefore, the process proceeds to step ST57a.

  In step ST57a, the timing of the peak of the pulse wave signal is awaited. In FIG. 18, the peak P5 occurs at the time point t5. Therefore, the peak detecting means 99 detects the peak P5 at the time point t5. When the peak is detected, the process proceeds to step ST58a.

In step ST58a, the time determining unit 104 (see FIG. 15) takes time required to recover the tissue in the even-numbered slices T1 after the i−1th data acquisition segment A _i−1 is executed. It is determined whether or not it has passed. Step ST58a is provided for the same reason as step ST58 described in the first embodiment. That is, step ST58a is provided to suppress the image deterioration caused by the execution of the i-th data acquisition segment A _i before the tissue in the even-numbered slice is recovered by T1. Here, since i = 2, it is determined whether or not the time required for T1 recovery of the tissue in the even-numbered slice has elapsed since the execution of the _first data acquisition segment A ₁ .

As a method of determining whether or not the time required for T1 recovery has elapsed, the same method as in the first embodiment is used. Specifically, the heartbeat signal detected after the _j− 1th data acquisition segment B _j−1 from the start of execution of the navigator sequence executed immediately before the _i− 1th data acquisition segment A _i−1. The time H up to the point of occurrence of the peak is calculated, and it is determined whether the time required for T1 recovery has elapsed based on the comparison result of the time H and the predetermined time H0. Here, since i = 2 and j = 2, the time determination unit 104 has the first data collection segment from the execution start time point t31 of the navigator sequence N3 executed immediately before the _first data collection segment A _1. The time H = H11 until the time point t5 at which the peak P5 of the pulse wave signal detected after B ₁ is generated is calculated. Then, the time determination means 104 compares this time H11 with a predetermined time H0 and determines whether H11 ≧ H0 or H11 <H0. When H11 ≧ H0, it is determined that the time required for T1 recovery has elapsed. On the other hand, when H11 <H0, it is determined that the time required for T1 recovery has not elapsed. H0 is, for example, H0 = 2 seconds. Here, H11 <H0. Therefore, since it is determined that the time required for T1 recovery has not elapsed since the data collection segment A ₁ was executed, the process returns to step ST57a.

  In step ST57a, the timing of the peak of the pulse wave signal is awaited. In FIG. 18, a peak P6 occurs at time t6. Therefore, the peak detecting means 99 detects the peak P6 at the time point t6. When the peak is detected, the process proceeds to step ST58a.

In step ST58a, the time determination means 104 determines whether or not the time required for T1 recovery of the tissue in the even-numbered slice has elapsed since the execution of the _first data acquisition segment A1.

  The time determination means 104 calculates a time H12 from the execution start time point t31 of the navigator sequence N3 to the generation time point t6 of the peak P6 of the pulse wave signal, and compares this time H12 with a predetermined time H0. When H12 ≧ H0, it is determined that the time required for T1 recovery has elapsed, and when H12 <H0 or less, it is determined that the time required for T1 recovery has not elapsed. Here, H12 ≧ H0. Therefore, the process proceeds to step ST54a.

  In step ST54a, the trigger generating means 100 generates a trigger for executing the navigator sequence N5 in synchronization with the peak P6. When the trigger is generated, the control unit 5 sends the data of the RF pulse included in the navigator sequence N5 to the transmitter 6 and the data of the gradient pulse included in the navigator sequence N5 to the gradient magnetic field power supply 7. . Therefore, the navigator sequence N5 is executed. A profile F (not shown) is generated based on the data obtained by executing the navigator sequence N5. After generating the profile F, the process proceeds to step ST55a.

  In step ST55a, the position detection means 95 detects the position z5 of the edge of the liver when the navigator sequence N5 is executed, based on the profile. The detected liver edge position z5 represents the signal value z5 of the respiratory signal when the navigator sequence N5 is executed in the main scan MS. After detecting the signal value (the position of the edge of the liver) z5 of the respiratory signal, the process proceeds to step ST56a.

  In step ST56a, the signal value determination means 101 determines whether or not the signal value z5 is within the window W. Here, since the signal value z5 is not within the window W, the process returns to step ST53a again.

  Similarly, in step ST56a, the loop of steps ST53a, ST54a, ST55a, and ST56a is repeatedly executed until it is determined in step ST56a that the signal value of the respiratory signal (the position of the edge of the liver) is within the window W. In the second mode, the signal value (the position of the edge of the liver) z8 of the respiratory signal when the navigator sequence N8 is executed is in the window W. Therefore, in step ST56a, the signal value determination means 101 determines that the signal value z8 of the respiratory signal is within the window W. When it is determined that the signal value z8 of the respiratory signal is within the window W, the process proceeds to step ST550.

In step ST550, the trigger generating means 100 generates a trigger for executing the data acquisition segment A _i . When the trigger is generated, the control unit 5 sends the data of the RF pulse included in the data acquisition segment A _i to the transmitter 6, and changes the data of the gradient pulse included in the data acquisition segment A _i into the gradient magnetic field. Send to power supply 7. The transmitter 6 supplies a current to the RF coil 24 based on the data received from the control unit 5, and the gradient magnetic field power supply 7 supplies a current to the gradient coil 23 based on the data received from the control unit 5. Therefore, the data collection segment A _i is executed. Since i = 2 here, the data collection segment A ₂ is executed. Data collection segment A ₂ is performed immediately after the navigator sequence N8. By executing the data acquisition segment _{A 2,} imaging data of the group Ga (slice #. 2 to # 2m of even-number) it is collected. After executing the data acquisition segment A ₂ , the process proceeds to step ST570.

  In step ST570, the data collection determination unit 102 determines whether or not all the k-space data necessary for image reconstruction has been collected. Here, since all the data have not been collected yet, the process proceeds to step ST580.

In step ST580, the increment means 103 increments i or j. Here, since the data collection segment A _i (i = 2) has been executed, the increment means 103 increments i. i is incremented from i = 2 to i = 3. After incrementing i, the process returns to step ST520.

  In step ST520, the determining means 961 collects the imaging data of the group Ga (even-numbered slices # 2 to # 2m) or the imaging data of the group Gb (odd-numbered slices # 1 to # 2m-1). Decide what to collect. Here, it is determined that the imaging data of the group Gb (the odd-numbered slices # 1 to # 2m-1) is acquired. Therefore, the process proceeds to step ST540.

  In step ST540, first, in step ST52b, the ij value determination means 971 determines whether j> 1 or j = 1. Here, since j = 2, j> 1. Therefore, the process proceeds to step ST57b.

  In step ST57b, the timing of the peak of the pulse wave signal is awaited. In FIG. 18, a peak P10 occurs at time t10. Therefore, the peak detecting means 99 detects the peak P10 at the time point t10. When the peak is detected, the process proceeds to step ST58b.

In step ST58b, the time determination means 104 determines whether or not the time required for T1 recovery of the tissue in the odd-numbered slice has elapsed since the j−1th data acquisition segment B _j−1 was executed. To judge. Step ST58b is provided for the same reason as step ST58 described in the first embodiment. That is, step ST58b is provided to suppress the image deterioration caused by executing the j-th data acquisition segment B _j before the tissue in the odd-numbered slices is recovered by T1. Here, since j = 2, it is determined whether or not the time required for T1 recovery of the tissue in the odd-numbered slice has elapsed since the first data acquisition segment B ₁ was executed.

As a method of determining whether or not the time required for T1 recovery has elapsed, the same method as in the first embodiment is used. Specifically, the peak of the j-1 th data acquisition segments B from the start point of the executed navigator sequence immediately before the _j-1, i-1 th detected heartbeat signal after the data acquisition segments A _i The time H up to the point of occurrence of T is calculated, and it is determined whether or not the time required for T1 recovery has elapsed based on the comparison result of the time H and the predetermined time H0. Here, since j = 2 and i = 3, the time determination means 104 has the second data collection segment from the execution start time point t41 of the navigator sequence N4 executed immediately before the _first data collection segment B _1. It calculates the time H = H21 until occurrence time t10 of the peak P10 of the detected pulse wave signal after a _2. Then, the time determination means 104 compares this time H21 with a predetermined time H0 and determines whether H21 ≧ H0 or H21 <H0. If H21 ≧ H0, it is determined that the time required for T1 recovery has elapsed, while if H21 <H0, it is determined that the time required for T1 recovery has not elapsed. H0 is, for example, H0 = 2 seconds. Here, H21 ≧ H0. Therefore, since it is determined that the time required for T1 recovery has elapsed since the data collection segment B ₁ was executed, the process proceeds to step ST54b.

  In step ST54b, the trigger generating means 100 generates a trigger for executing the navigator sequence N9 in synchronization with the peak P10. When the trigger is generated, the control unit 5 sends the data of the RF pulse included in the navigator sequence N9 to the transmitter 6 and the data of the gradient pulse included in the navigator sequence N9 to the gradient magnetic field power supply 7. . Therefore, the navigator sequence N9 is executed. A profile F (not shown) is generated based on the data obtained by executing the navigator sequence N9. After generating the profile F, the process proceeds to step ST55b.

  In step ST55b, the position detecting means 95 detects the position z9 of the edge of the liver when the navigator sequence N9 is executed, based on the profile. The detected liver edge position z9 represents the signal value z9 of the respiratory signal when the navigator sequence N9 is executed in the main scan MS. After detecting the signal value (the position of the edge of the liver) z9 of the respiratory signal, the process proceeds to step ST56b.

  In step ST56b, the signal value determination means 101 determines whether or not the signal value z9 is within the window W. Here, since the signal value z9 is not within the window W, the process returns to step ST53b again.

  Similarly, in step ST56b, the loop of steps ST53b, ST54b, ST55b, and ST56b is repeatedly executed until it is determined that the signal value of the respiratory signal (the position of the edge of the liver) is within the window W in step ST56b. In the second embodiment, the signal value (the position of the edge of the liver) z13 of the respiratory signal when the navigator sequence N13 is executed is in the window W. Therefore, in step ST56b, the signal value determination means 101 determines that the signal value z13 of the respiratory signal is within the window W. When it is determined that the signal value z13 of the respiratory signal is within the window W, the process proceeds to step ST560.

In step ST560, the trigger generating means 100 generates a trigger for executing the data collection segment B _j . When the trigger is generated, the control unit 5 sends the data of the RF pulse included in the data acquisition segment B _j to the transmitter 6, and changes the data of the gradient pulse included in the data acquisition segment B _j into the gradient magnetic field. Send to power supply 7. The transmitter 6 supplies a current to the RF coil 24 based on the data received from the control unit 5, and the gradient magnetic field power supply 7 supplies a current to the gradient coil 23 based on the data received from the control unit 5. Therefore, the data collection segment B _j is executed. Since j = 2 here, the data collection segment B ₂ is executed. Data collection segment _{B 2} is performed immediately after the navigator sequence N13. By executing the data acquisition segment _{B 2,} imaging data of the group Gb (odd number of slices # 1~ # 2m-1) are collected. After executing the data acquisition segment B ₂ , the process proceeds to step ST570.

  In step ST570, the data collection determination unit 102 determines whether or not all the k-space data necessary for image reconstruction has been collected. Here, since all the data have not been collected yet, the process proceeds to step ST580.

In step ST, the increment means 103 increments i or j. Here, since the data collection segment B _j (j = 2) has been executed, the increment means 103 increments j. j is incremented from j = 2 to j = 3. After incrementing j, the process returns to step ST520.

  In step ST520, the determining means 961 collects the imaging data of the group Ga (even-numbered slices # 2 to # 2m) or the imaging data of the group Gb (odd-numbered slices # 1 to # 2m-1). Decide what to collect. Here, it is determined that the imaging data of the group Ga (even-numbered slices # 2 to # 2m) is acquired. Therefore, the process proceeds to step ST530.

  In step ST530, first, in step ST52a, the ij value determination means 971 determines whether i> 1 or i = 1. Here, since i = 3, i> 1. Therefore, the process proceeds to step ST57a.

  In step ST57a, the timing of the peak of the pulse wave signal is awaited. In FIG. 18, the peak P15 occurs at the time point t15. Therefore, the peak detecting means 99 detects the peak P15 at the time point t15. When the peak is detected, the process proceeds to step ST58a.

In step ST58a, the time determination means 104 determines whether or not the time required for T1 recovery of the tissue in the even-numbered slice has elapsed since the i−1th data acquisition segment A _i−1 was executed. To judge. Here, since i = 3, it is determined whether or not the time required for T1 recovery of the tissue in the even-numbered slice has elapsed since the second data acquisition segment A ₂ was executed.

First, the time determination unit 104 calculates the time H13 from the execution start time t91 of the navigator sequence N8 executed immediately before the _second data acquisition segment A2 to the occurrence time t15 of the peak P15 of the heartbeat signal. Then, the time determination means 104 compares this time H13 with a predetermined time H0 and determines whether H13 ≧ H0 or H13 <H0. Here, H13 ≧ H0. Therefore, the data acquisition segment A ₂ is determined as the time required to T1 recover from being executed has elapsed, the process proceeds to step ST54a.

  In step ST54a, the navigator sequence N14 is executed in synchronization with the peak P15. A profile F (not shown) is generated based on the data obtained by executing the navigator sequence N14. After generating the profile F, the process proceeds to step ST55a.

  In step ST55a, the position detection means 95 detects the position z14 of the edge of the liver when the navigator sequence N14 is executed based on the profile. The detected liver edge position z14 represents the signal value z14 of the respiratory signal when the navigator sequence N14 is executed in the main scan MS. After detecting the signal value (position of the edge of the liver) z14 of the respiratory signal, the process proceeds to step ST56a.

  In step ST56a, the signal value determination means 101 determines whether or not the signal value z14 is within the window W. Here, since the signal value z14 is within the window W, the process proceeds to step ST550.

In step ST550, the trigger generating means 100 generates a trigger for executing the data acquisition segment A _i . When the trigger is generated, the control unit 5 sends the data of the RF pulse included in the data acquisition segment A _i to the transmitter 6, and changes the data of the gradient pulse included in the data acquisition segment A _i into the gradient magnetic field. Send to power supply 7. The transmitter 6 supplies a current to the RF coil 24 based on the data received from the control unit 5, and the gradient magnetic field power supply 7 supplies a current to the gradient coil 23 based on the data received from the control unit 5. Therefore, the data collection segment A _i is executed. Since i = 3 here, the data collection segment A ₃ is executed. Data acquisition segments _{A 3} is performed immediately after the navigator sequence N14. By executing the data acquisition segment _{A 3,} the imaging data of the group Ga (slice #. 2 to # 2m of even-number) it is collected. After executing the data acquisition segment A ₃ , the process proceeds to step ST570.

  In step ST570, the data collection determination unit 102 determines whether or not all the k-space data necessary for image reconstruction has been collected. Here, since all the data have not been collected yet, the process proceeds to step ST580.

In step ST580, the increment means 103 increments i or j. Here, since the data collection segment A _i (i = 3) has been executed, the increment means 103 increments i. i is incremented from i = 3 to i = 4. After incrementing i, the process returns to step ST520.

  In step ST520, the determining unit 961 collects the imaging data of the group Ga (slices # 2 to # 2m of even number) or the imaging data of the group Gb (slices # 1 to # 2m-1 of odd number). Decide what to collect. Here, it is determined that the imaging data of the group Gb (the odd-numbered slices # 1 to # 2m-1) is acquired. Therefore, the process proceeds to step ST540.

  In step ST540, first, in step ST52b, the ij value determination means 971 determines whether j> 1 or j = 1. Here, since j = 3, j> 1. Therefore, the process proceeds to step ST57b.

  In step ST57b, the timing of the peak of the pulse wave signal is awaited. In FIG. 18, the peak P16 occurs at the time point t16. Therefore, the peak detecting means 99 detects the peak P16 at the time point t16. When the peak is detected, the process proceeds to step ST58b.

In step ST58b, the time determination means 104 determines whether or not the time required for T1 recovery of the tissue in the odd-numbered slice has elapsed since the j−1th data acquisition segment B _j−1 was executed. To judge. Here, since j = 3, it is determined whether or not the time required for T1 recovery of the tissue in the odd-numbered slice has elapsed since the second data acquisition segment B ₂ was executed.

The time determination means 104 calculates the time H22 from the execution start time point t141 of the navigator sequence N13 executed immediately before the _second data acquisition segment B2 to the generation time point t16 of the peak P16 of the pulse wave signal. Then, the time determination means 104 compares this time H22 with the predetermined time H0 and determines whether H22 ≧ H0 or H22 <H0. Here, H22 <H0. Therefore, the data acquisition segment B ₂ is determined from being executed has not elapsed the time required for T1 recovery, the flow returns to step ST57b.

  In step ST57b, the timing of the peak of the pulse wave signal is awaited. In FIG. 18, the peak P17 occurs at the time point t17. Therefore, the peak detecting means 99 detects the peak P17 at the time point t17. When the peak is detected, the process proceeds to step ST58b.

At step ST58b, the time determination unit 104 determines the second data collection segment B ₂ is performed, whether the elapsed time required to organize a T1 recovery in a slice of odd numbers.

  The time determination means 104 calculates the time H23 from the execution start time point t141 of the navigator sequence N13 to the occurrence time point t17 of the peak P17 of the heartbeat signal, and compares this time H23 with the predetermined time H0. When H23 ≧ H0, it is determined that the time required for T1 recovery has elapsed, and when H23 <H0 or less, it is determined that the time required for T1 recovery has not elapsed. Here, H23 ≧ H0. Therefore, the process proceeds to step ST54b.

  In step ST54b, the trigger generating means 100 generates a trigger for executing the navigator sequence N15 in synchronization with the peak P17. When the trigger is generated, the control unit 5 sends the RF pulse data included in the navigator sequence N15 to the transmitter 6, and sends the gradient pulse data included in the navigator sequence N15 to the gradient magnetic field power supply 7. . Therefore, the navigator sequence N15 is executed. A profile F (not shown) is generated based on the data obtained by executing the navigator sequence N15. After generating the profile F, the process proceeds to step ST55b.

  In step ST55b, the position detecting means 95 detects the position z15 of the edge of the liver when the navigator sequence N15 is executed, based on the profile. The detected liver edge position z15 represents the signal value z15 of the respiratory signal when the navigator sequence N15 is executed in the main scan MS. After detecting the signal value (position of the edge of the liver) z15 of the respiratory signal, the process proceeds to step ST56b.

  In step ST56b, the signal value determination means 101 determines whether or not the signal value z15 is within the window W. Here, since the signal value z15 is not within the window W, the process returns to step ST53b again.

  Similarly, in step ST56b, the loop of steps ST53b, ST54b, ST55b, and ST56b is repeatedly executed until it is determined that the signal value of the respiratory signal (the position of the edge of the liver) is within the window W in step ST56b. In the second embodiment, the signal value (the position of the edge of the liver) z17 of the respiratory signal when the navigator sequence N17 is executed is in the window W. Therefore, in step ST56b, the signal value determination means 101 determines that the signal value z17 of the respiratory signal is within the window W. When it is determined that the signal value z17 of the respiratory signal is within the window W, the process proceeds to step ST560.

In step ST560, the trigger generating means 100 generates a trigger for executing the data collection segment B _j . When the trigger is generated, the control unit 5 sends the data of the RF pulse included in the data acquisition segment B _j to the transmitter 6, and changes the data of the gradient pulse included in the data acquisition segment B _j into the gradient magnetic field. Send to power supply 7. The transmitter 6 supplies a current to the RF coil 24 based on the data received from the control unit 5, and the gradient magnetic field power supply 7 supplies a current to the gradient coil 23 based on the data received from the control unit 5. Therefore, the data collection segment B _j is executed. Since j = 3 here, the data collection segment B ₃ is executed. Data collection segment _{B 3} is performed immediately after the navigator sequence N17. By executing the data acquisition segment _{B 3,} the imaging data of the group Gb (odd number of slices # 1~ # 2m-1) are collected. After performing the data collection segment _{B 3,} the process proceeds to step ST570.

  In step ST570, the data collection determination unit 102 determines whether or not all the k-space data necessary for image reconstruction has been collected. Here, since all the data have not been collected yet, the process proceeds to step ST580.

In step ST580, the increment means 103 increments i or j. Here, since the data collection segment B _j (j = 3) has been executed, the increment means 103 increments j. j is incremented from j = 3 to j = 4. After incrementing j, the process returns to step ST520.

  Similarly, in step ST570, the imaging data of the group Ga (slices of even numbers) and the group Gb (slices of odd numbers) are determined until it is determined that all the k-space data necessary for slice image reconstruction has been acquired. ), The loop of steps ST520 to ST580 is repeatedly executed. If it is determined in step ST570 that all data has been collected, the flow is ended.

In the second embodiment, before executing the i-th data acquisition segments A _i, since the i-1 th data acquisition segments A _i-1 is executed, whether the elapsed time required for T1 recovery Is determined. If it is determined that the time required for T1 recovery has not elapsed, then the i-th data acquisition segment A _i is not executed and the next peak of the heartbeat signal occurs. Then, when the next peak occurs, it is determined again whether or not the time required for T1 recovery has elapsed, and when it is determined that the time required for T1 recovery has not elapsed, the i-th data collection segment A Wait for the next peak of the heartbeat signal to occur without performing _i . Therefore, it is possible to prevent the i-th data acquisition segment A _{i from} being executed before the time required for T1 recovery elapses. DWI images can be obtained.

In the second embodiment, before executing the j-th data collection segment B _j, or since the j-1 th data acquisition segments B _j-1 is performed, has elapsed the time required for T1 recovery It is also determined whether or not. When it is determined that the time required for T1 recovery has not elapsed, the j-th data acquisition segment B _j is not executed and the next peak of the heartbeat signal occurs. Therefore, in the odd-numbered slices, it is possible to obtain a high-quality DW1 image that reflects the difference in T2 value of each tissue.

  In the second mode, the slices # 1 to # 2m are divided into two groups Ga and Gb. However, the slices # 1 to # 2m may be divided into three or more groups, and a plurality of data collection segments for collecting slice data may be executed for each group during the main scan MS.

  In the second embodiment, in steps ST58a and 58b, the navigator sequence is not executed and it waits for the peak of the pulse wave signal to occur until it is determined that the time required for T1 recovery has elapsed. However, the navigator sequence may be executed even before it is determined that the time required for T1 recovery has elapsed.

In the second mode, the peak of the heartbeat signal from the execution start time point of the navigator sequence executed immediately before the i−1th data acquisition segment A _i−1 (or the j−1th data acquisition segment B _j−1 ). The time H up to the occurrence time of T is calculated, and it is determined whether or not the time required for T1 recovery has elapsed based on the comparison result of the time H and the predetermined time H0. However, instead of the time H, another time H ′ may be calculated, and whether or not the time required for T1 recovery has elapsed may be determined based on the comparison result of the time H ′ and the predetermined time H0. Good. Another time H ′ is, for example, the time from the execution start time of the i−1th data acquisition sequence A _i−1 (j−1th data acquisition segment B _j−1 ) to the occurrence time of the peak of the heartbeat signal. , Or the time from the end of execution of the navigator sequence to the time of occurrence of the peak of the heartbeat signal.

  In the first form, the sequence using the 3D FSE method is executed in the main scan MS, and in the second form, the 2D sequence for acquiring the diffusion weighted image is executed in the main scan MS. . However, the present invention is not limited to the sequence using the 3D FSE method and the 2D sequence for acquiring the diffusion weighted image, and can be applied to the case of executing another imaging sequence.

  In the first and second embodiments, a pulse wave signal is obtained as a heartbeat signal including heartbeat information. However, a signal other than the pulse wave signal may be obtained as the heartbeat signal. For example, instead of the pulse wave signal, an electrocardiographic signal including heartbeat information may be obtained as the heartbeat signal.

  In the first and second forms, an example of collecting data of the entire region of k-space has been described. However, the present invention can also be applied to a case where data of a partial region of k space is not collected, such as partial kz, fractional echo, half Fourier, 1/2 NEX, phase conjugate symmetry method, and frequency conjugate symmetry method. .

DESCRIPTION OF SYMBOLS 1 MR device 2 Magnet 3 Table 3a Cradle 4 Receiving coil 5 Control part 6 Transmitter 7 Gradient magnetic field power supply 8 Receiver 9 Processing device 10 Storage part 11 Operation part 12 Display part 13 Subject 14 Pulse wave sensor 15 Signal processing part 21 Housing Space 22 Superconducting coil 23 Gradient coil 24 RF coil 91 Image generating means 92 Area setting means 93 Range setting means 94 Profile generating means 95 Position detecting means 96 Window setting means 97 Initial value setting means 98 i value determining means 99 Peak detecting means 100 Trigger generation means 101 Signal value determination means 102 Data collection determination means 103 Increment means 104 Time determination means 921 Slice setting means 922 Grouping means 971 ij value determination means

Claims (11)

A first scan for obtaining respiratory information from a first part of the subject and a second scan for obtaining a DWI image, a T2-weighted image, or a PD-weighted image of the imaging part of the subject are executed. A magnetic resonance apparatus,
In the first scan, a plurality of first navigator sequences for collecting a plurality of first data including respiratory information from the first region are executed, and in the second scan, the first navigator sequence is executed. Scanning means for performing a plurality of second navigator sequences for collecting a plurality of second data including respiratory information from a region and a plurality of data acquisition segments for collecting a plurality of imaging data of the imaging region When,
Based on the first data, the signal value of the first respiratory signal of the subject during the first scan is obtained, and based on the second data, the subject value during the second scan is determined. Means for determining the signal value of the second respiratory signal,
Window setting means for setting a window representing a range of signal values for executing the data acquisition segment based on the signal value of the first respiratory signal;
First determining means for determining whether the signal value of the second respiratory signal is included in the window,
Trigger generating means for generating a trigger for executing each of the plurality of second navigator sequences based on a heartbeat signal including heartbeat information of the subject;
A control unit that controls the scanning unit so that the second navigator sequence is executed based on the trigger, and is obtained by a second navigator sequence of one of the plurality of second navigator sequences. If it is determined that the signal value of the acquired second respiration signal is included in the window, one of the plurality of data acquisition segments is detected before the next second navigator sequence is executed. A control unit for controlling the scanning means so that a data acquisition segment is executed;
After the one data acquisition segment is executed and before the next data acquisition segment is executed, the one data acquisition segment is executed and then necessary for T1 recovery of the tissue in the imaging region. Second determining means for determining whether or not the first time has elapsed,
Have
The control unit is
The next data acquisition segment is not executed until it is determined that the first time has elapsed, and the signal value of the second respiratory signal is determined after it is determined that the first time has elapsed. The second navigator sequence is executed until it is determined to be included in the window, and when it is determined that the signal value of the second respiratory signal is included in the window, the next data acquisition segment is performed. A magnetic resonance apparatus for controlling the scanning means so that the above method is performed. The heartbeat signal has a plurality of peaks generated according to the movement of the heart of the subject,
The trigger generating means,
The magnetic resonance apparatus according to claim 1, wherein the trigger is generated in synchronization with the peak. Having a peak detecting means for detecting the peak,
The second determination means is
Calculating a second time between the start of the one second navigator sequence and the occurrence of the peak detected after the one data acquisition segment is performed,
Comparing the second time with a predetermined time serving as a reference for determining whether or not the first time has passed,
The magnetic resonance apparatus according to claim 2, wherein it is determined whether or not the first time has elapsed based on a comparison result between the second time and the predetermined time. The second determination means is
The magnetic resonance apparatus according to claim 3, wherein the second time is calculated each time the peak is detected until it is determined that the first time has elapsed. A first scan for obtaining respiratory information from a first part of the subject and a second scan for obtaining a DWI image, a T2-weighted image, or a PD-weighted image of the imaging part of the subject are executed. A magnetic resonance apparatus,
Setting means for setting a plurality of slices in the imaging region,
Grouping means for dividing the plurality of slices into a plurality of groups,
In the first scan, a plurality of first navigator sequences for collecting a plurality of first data including respiratory information from the first region are executed, and in the second scan, the first navigator sequence is executed. A scan performing a plurality of second navigator sequences for collecting a plurality of second data including respiratory information from a site and a plurality of data acquisition segments for acquiring a plurality of imaging data for each group. Means and
Based on the first data, the signal value of the first respiratory signal of the subject during the first scan is obtained, and based on the second data, the subject value during the second scan is determined. Means for determining the signal value of the second respiratory signal,
Window setting means for setting a window representing a range of signal values for executing the data acquisition segment based on the signal value of the first respiratory signal;
First determining means for determining whether the signal value of the second respiratory signal is included in the window,
Trigger generating means for generating a trigger for executing each of the plurality of second navigator sequences based on a heartbeat signal including heartbeat information of the subject;
A control unit that controls the scanning unit so that the second navigator sequence is executed based on the trigger, and is obtained by a second navigator sequence of one of the plurality of second navigator sequences. If it is determined that the signal value of the acquired second respiratory signal is included in the window, the data of one of the plurality of data acquisition segments is determined before executing the next second navigator sequence. A control unit for controlling the scanning means so that the acquisition segment is executed;
After the one data acquisition segment for collecting the imaging data of the first group of the plurality of groups is executed, the next data acquisition segment for collecting the imaging data of the first group is performed. Before execution, determining whether the first time required to T1 recover tissue in slices included in the first group has elapsed since the one data acquisition segment was executed. Second determining means for
The control unit is
The next data acquisition segment is not executed until it is determined that the first time has elapsed, and the signal value of the second respiratory signal is determined after it is determined that the first time has elapsed. The second navigator sequence is executed until it is determined to be included in the window, and when it is determined that the signal value of the second respiratory signal is included in the window, the next data acquisition segment is performed. A magnetic resonance apparatus for controlling the scanning means so that the above method is performed. The heartbeat signal has a plurality of peaks generated according to the movement of the heart of the subject,
The trigger generating means,
The magnetic resonance apparatus according to claim 5, wherein the trigger is generated in synchronization with the peak. Having a peak detecting means for detecting the peak,
The second determination means is
A start time point of the one second navigator sequence for collecting data of slices included in the first group, and collecting data of slices included in a second group of the plurality of groups Calculating a second time between the time of occurrence of the peak detected after the one data collection segment of
Comparing the second time with a predetermined time serving as a reference for determining whether or not the first time has passed,
The magnetic resonance apparatus according to claim 6, wherein it is determined whether or not the first time has elapsed based on a comparison result between the second time and the predetermined time. The second determination means is
The magnetic resonance apparatus according to claim 7, wherein the second time is calculated each time the peak is detected until it is determined that the first time has elapsed. The first group includes even-numbered slices of the plurality of slices,
The magnetic resonance apparatus according to claim 8, wherein the second group includes odd-numbered slices of the plurality of slices.   The magnetic resonance apparatus according to any one of claims 1 to 9, wherein the heartbeat signal is a pulse wave signal including heartbeat information or an electrocardiographic signal including heartbeat information. The scanning means is
A transmitter for supplying current to the RF coil,
A gradient magnetic field power supply that supplies current to the gradient coil,
Have
The magnetic resonance apparatus according to claim 1, wherein the control unit controls the transmitter and the gradient magnetic field power supply.