JP5633902B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus that images a subject in synchronization with a respiratory synchronization trigger.

  A respiratory synchronization method is known as a method for imaging a part (for example, a bile duct) that moves due to breathing of a subject (see Patent Document 1).

JP 2008-307287 A

As an example of the respiratory synchronization method, a respiratory synchronization method is known in which a scan is executed when a respiratory signal reaches a trigger level (see FIG. 1).
FIG. 1 is a diagram illustrating an example of a respiratory synchronization method.
In FIG. 1, when the respiratory signal S of the subject exceeds the trigger level TL and then reaches the trigger level TL again, the respiratory synchronization trigger AT _k (k = 1, 2,..., N, n + 1, ...) occurs. Then, a scan RS _i (i = 1, 2,..., N, n + 1,...) For collecting image data of the imaging region of the subject is executed in synchronization with the respiratory synchronization trigger AT _k. The Therefore, since the scan RS _i can be executed while the body movement due to the breathing of the subject is small, an image with reduced body movement artifacts can be obtained.
However, the subject's breathing may become shallow due to the subject's sleep during imaging. Referring to FIG. 1, after time t _{n + 1} , the subject's breathing becomes shallow, and the breathing signal S remains lower than the trigger level TL. Therefore, after the respiratory synchronization trigger AT _{n + 1} is generated at the time point t _{n + 1} , the state in which the respiratory synchronization trigger is not generated continues. Therefore, after the scan RS _{n + 1} is performed in synchronization with the respiratory synchronization trigger AT _{n + 1} , the next scan is performed. The state where RS _i is not executed continues. In this case, the shooting time may become very long, or in some cases, scanning may stop during shooting. Therefore, it is desired that the scan can be continuously executed even if the subject's breathing becomes shallow due to the subject's sleep during imaging.

The first aspect of the present invention is:
Trigger generating means for generating a respiratory synchronization trigger based on the respiratory signal of the subject;
Scanning means for performing a respiratory synchronization scan for collecting magnetic resonance signals from the subject in synchronization with the respiratory synchronization trigger;
A photographing device having
The scanning means includes
If a respiratory synchronization trigger does not occur even after a predetermined time has elapsed from the respiratory synchronization scan, a respiratory asynchronous scan for collecting a magnetic resonance signal from the subject is executed even if the respiratory synchronization trigger has not occurred , A photographing device.

The second aspect of the present invention is:
Trigger generating means for generating a respiratory synchronization trigger based on the respiratory signal of the subject;
Scanning means for executing a scan of the subject in synchronization with the respiratory synchronization trigger;
If a respiratory synchronization trigger does not occur even after the predetermined time has elapsed since the respiratory synchronization scan, a magnetic resonance signal is collected from the subject based on the respiratory signal even if the respiratory synchronization trigger has not occurred. Scan execution determination means for determining whether to perform a breath asynchronous scan for
A photographing device having
The scanning means includes
When the scan execution determination unit determines to execute the respiratory asynchronous scan, the imaging apparatus performs the respiratory asynchronous scan.

  Even if the respiratory synchronization trigger is not generated due to the reason that the subject sleeps during imaging, the scan can be continuously executed.

It is a figure which shows an example of the respiration synchronization method. 1 is a schematic diagram of a magnetic resonance imaging apparatus according to a first embodiment of the present invention. It is a figure which shows the scan performed when the subject 12 is a normal respiratory state. It is a figure which shows a mode when the test subject's 12 becomes shallow. It is a figure which shows an example of the scan performed between the start of photography, and completion | finish. It is a figure which shows the predetermined time from which a start time differs. It is the schematic of the MRI apparatus of a 2nd form. It is a figure which shows an example of the scan performed in a 2nd form. It is the schematic of the MRI apparatus of the 3rd form. It is a figure which shows an example of the scan performed in a 3rd form. It is the schematic of the MRI apparatus of the 4th form. It is a figure which shows an example of the scan performed in a 4th form.

  Hereinafter, although the form for inventing is demonstrated, this invention is not limited to the following forms.

(1) First Embodiment FIG. 2 is a schematic diagram of a magnetic resonance imaging apparatus according to the first embodiment of the present invention.

  A magnetic resonance imaging apparatus (MRI apparatus MRI: Magnetic Resonance Imaging) 100 includes a magnetic field generator 2, a table 3, a receiving coil 4, and the like.

  The magnetic field generator 2 includes a bore 21 in which the subject 12 is accommodated, a superconducting coil 22, a gradient coil 23, and a transmission coil 24. The superconducting coil 22 applies a static magnetic field B0, and the gradient coil 23 applies a gradient magnetic field. The transmission coil 24 transmits an RF pulse. In place of the superconducting coil 22, a permanent magnet may be used.

  The table 3 has a cradle 31 for supporting the subject 12. The cradle 31 is configured to be movable to the bore 21. The subject 12 is transported to the bore 21 by the cradle 31.

  The receiving coil 4 is attached from the chest to the abdomen of the subject 12 and receives a magnetic resonance signal.

  The MRI apparatus 100 further includes a sequencer 5, a transmitter 6, a gradient magnetic field power source 7, a receiver 8, a central processing unit 9, an input device 10, and a display device 11.

  Under the control of the central processing unit 9, the sequencer 5 sends information for executing a pulse sequence to the transmitter 6 and the gradient magnetic field power supply 7. Specifically, under the control of the central processing unit 9, the sequencer 5 sends RF pulse information (center frequency, bandwidth, etc.) to the transmitter 6, and gradient magnetic field information (gradient magnetic field strength, etc.). Send to gradient magnetic field power supply 7.

  The transmitter 6 outputs a drive signal for driving the RF coil 24 based on the information sent from the sequencer 5.

  The gradient magnetic field power supply 7 outputs a drive signal for driving the gradient coil 23 based on the information sent from the sequencer 5.

  The receiver 8 processes the magnetic resonance signal received by the receiving coil 4 and transmits it to the central processing unit 9.

  The central processing unit 9 implements various operations of the MRI apparatus 100 such as transmitting necessary information to the sequencer 5 and the display unit 11 and reconstructing an image based on a signal received from the receiver 8. The operation of each unit of the MRI apparatus 100 is controlled. The central processing unit 9 is constituted by a computer, for example.

  The central processing unit 9 includes trigger generation means 91, trigger determination means 92, time setting means 93, and the like.

Based on the respiratory signal S, the trigger generation unit 91 generates a respiratory synchronization trigger AT _k (k is an integer equal to or greater than 1) that serves as a trigger when starting the respiratory synchronization scan RS _i (i is an integer equal to or greater than 1). .

The trigger determination unit 92 performs the following operation after a predetermined time TX has elapsed since the start of the respiratory synchronization scan RS _i (i is an integer of 1 or more) or the respiratory asynchronous scan BN _j (j is an integer of 1 or more). It is determined whether or not the respiratory synchronization trigger AT _{k + 1} is generated.

  The time setting means 93 sets a predetermined time TX based on information input from the input device 10 by the operator 13.

  The central processing unit 9 is an example of the trigger generating unit 91, the trigger determining unit 92, and the time setting unit 93, and functions as these units by executing a predetermined program.

  The input device 10 inputs various commands to the central processing unit 9 according to the operation of the operator 13. The display device 11 displays various information.

  The MRI apparatus 100 is configured as described above. The combination of the magnetic field generator 2, the sequencer 5, the transmitter 6, the gradient magnetic field power source 7, and the receiving coil 4 corresponds to the scanning means described in the means for solving the problem.

Next, the operation of the MRI apparatus 100 will be described in comparison with the method shown in FIG.
When a part (for example, a bile duct) that moves due to breathing of the subject 12 is imaged using the method shown in FIG. 1, there is a problem that a scan is not executed because a respiratory synchronization trigger does not occur. However, by performing imaging using the MRI apparatus 100 according to the first embodiment, it is possible to execute a scan even if a respiratory synchronization trigger does not occur. The reason for this will be described below with reference to FIGS.

  FIG. 3 is a diagram illustrating a scan executed when the subject 12 is in a normal breathing state. FIG. 3A is a diagram showing the respiratory signal S, and FIG. 3B is a diagram showing a period during which the scan is executed.

  The MRI apparatus 100 performs imaging while acquiring the respiratory signal S of the subject 12. Specifically, when the respiratory signal S exceeds the trigger level TL and then returns to the trigger level TL again, a respiratory synchronization trigger is generated, and a respiratory synchronization scan is executed in synchronization with the generated respiratory synchronization trigger. .

Referring to respiration signal S in FIG. 3 (a), the respiratory signal S reaches the trigger level TL at time _{t p,} then exceed the trigger level TL, at time _{t k,} it returns again to the trigger level TL. Therefore, at time t _k , the respiratory synchronization trigger AT _k is generated. When the respiratory synchronization trigger AT _k occurs, the respiratory synchronization scan RS _i is executed in synchronization with the respiratory synchronization trigger AT _k .

Further, the MRI apparatus 100 determines whether or not the next respiratory synchronization trigger AT _{k + 1} has occurred before the predetermined time TX has elapsed since the start of the respiratory synchronization scan RS _i . The predetermined time TX is a time determined in advance by the operator 13 before imaging the subject 12. The length of the predetermined time TX is determined to be about several seconds longer than the respiratory cycle Tn of the subject 12.

Referring to FIG. 3, before the predetermined time TX elapses, the respiration signal S exceeds the trigger level TL and returns to the trigger level TL again. Therefore, before the predetermined time TX elapses, the next respiratory synchronization trigger AT _{k + 1} is generated. In this case, the MRI apparatus 100 executes the next respiratory synchronization scan RS _{i + 1} in synchronization with the respiratory synchronization trigger AT _{k + 1} .

  However, the breathing of the subject 12 may become shallow due to the reason that the subject 12 falls asleep during imaging (see FIG. 4).

FIG. 4 is a diagram showing a state when the breathing of the subject 12 becomes shallow.
Referring to the time points t _{p to} t _k in FIG. 4, as in FIG. 3, the respiration signal S exceeds the trigger level TL and returns to the trigger level TL again. Therefore, since the breath synchronization trigger AT _k is generated at the time t _k , the breath synchronization scan RS _i is executed in synchronization with the breath synchronization trigger AT _k . However, the time t _k and later becomes shallow breathing of the subject 12, the respiratory signal S has a remains below the trigger level TL. Therefore, after the respiration synchronization trigger RS _i occurs at time t _k, later, so that the respiration synchronization trigger does not occur. In this case, the MRI apparatus 100 operates as follows.

The MRI apparatus 100 determines whether or not the next respiratory synchronization trigger AT _{k + 1} has occurred before the predetermined time TX has elapsed since the start of the respiratory synchronization scan RS _i . In FIG. 4, since the respiration signal S remains lower than the trigger level TL after the time t _k , the next respiration synchronization trigger AT _{k + 1} does not occur unlike the case of FIG. In this case, even if the next respiratory synchronization trigger AT _{k + 1} is not generated, the MRI apparatus 100 receives a magnetic resonance signal from the subject 12 when a predetermined time TX has elapsed since the start of the respiratory synchronization scan RS _i. Perform a breath asynchronous scan BN _j to collect. Therefore, the subject 12 can be scanned even if the next respiratory synchronization trigger AT _{k + 1} has not occurred.

As described above, the MRI apparatus 100 starts the execution of the respiratory asynchronous scan BN _j when the next respiratory synchronous trigger AT _{k + 1} does not occur even after the predetermined time TX has elapsed from the respiratory synchronous scan RS _i . Therefore, even if a situation in which the respiratory synchronization trigger does not occur due to the subject 12 sleeping during imaging, the scan can be continuously executed.

  Next, the operation of the MRI apparatus 100 from the start to the end of imaging of the subject 12 will be described more specifically with reference to FIG.

  FIG. 5 is a diagram illustrating an example of scanning executed between the start and end of imaging. FIG. 5A is a diagram showing a respiratory signal, and FIG. 5B is a diagram showing a period during which a scan is executed.

  First, the operator 13 determines a predetermined time TX as described with reference to FIG. 3 before imaging the subject 12. When the operator 13 determines the predetermined time TX, the operator 13 operates the input device 10 to input the predetermined time TX. When a predetermined time TX is input from the input device 10, the time setting means 93 (see FIG. 2) sets the predetermined time TX. Thus, after the predetermined time TX is set in advance, imaging of the subject 12 is started.

  The MRI apparatus 100 performs imaging while acquiring the respiratory signal S of the subject 12. In the first embodiment, a respiratory signal S is obtained by collecting navigator echoes from a region crossing the diaphragm and detecting the position of the diaphragm based on the collected navigator echoes. However, as long as the respiratory signal S can be obtained, the area where navigator echoes are collected does not necessarily have to cross the diaphragm. Since there is a certain time interval from the acquisition of the navigator echo to the acquisition of the next navigator echo, the respiratory signal S is actually expressed as a set of discrete data. In (a), the respiration signal S is shown by one curve for convenience of explanation.

Based on the respiratory signal S, the trigger generating means 91 (see FIG. 2) is configured to trigger a respiratory synchronization scan RS _i (i is an integer of 1 or more), a respiratory synchronization trigger AT _k (k is 1 or more). Integer). Specifically, the trigger generation means 91 generates a respiration synchronization trigger AT _k when the respiration signal S exceeds the trigger level TL and then returns to the trigger level TL again.

Referring to the respiratory signal of FIG. 5 (a), the respiratory signal S reaches the trigger level TL at time _{t 0,} then, exceeds the trigger level TL, at time _{t 1,} again, it returns to the trigger level TL. Therefore, the trigger generation means 91 generates the respiratory synchronization trigger AT ₁ at the time point t ₁ . When the breath synchronization trigger AT ₁ is generated, the breath synchronization scan RS ₁ is executed in synchronization with the breath synchronization trigger AT ₁ . During the time t ₁ ~t 1 _', since body motion due to respiration of the subject 12 is sufficiently small, respiratory gated scan RS ₁ is body motion due to respiration of the subject 12 is performed while sufficiently small.

Further, the trigger judgment means 92 (see FIG. 2) is from the start breathing synchronization scan RS _1, before the predetermined time TX has elapsed, it is determined whether the next breath synchronous trigger AT ₂ occurs . Referring to FIG. 5, from the start of the respiratory gated scan RS _1, at time t ₂ before the predetermined time TX has elapsed, the next breath synchronous trigger AT ₂ has occurred. Therefore, the trigger judgment unit 92, from the start breathing synchronization scan RS _1, before the predetermined time TX has elapsed, it is determined that the next breath synchronous trigger AT ₂ has occurred. In this case, the MRI apparatus 100 executes the respiration synchronization scan RS ₂ in synchronization with the respiration synchronization trigger AT ₂ . Between time _t 2 ~t ₂ ', since by respiration of the subject 12 motion is sufficiently small, respiratory gated scan RS _2, as in the respiratory gated scan RS _1, the body movement due to respiration of the subject 12 Performed while small enough.

Hereinafter, in the same manner, a respiratory synchronization scan is executed in synchronization with the respiratory synchronization trigger. For example, when the respiratory signal S reaches the trigger level TL at the time point t _{n + 1} , the respiratory synchronization trigger AT _{n + 1} is generated. Therefore, the respiratory synchronization scan RS _{n + 1} is executed in synchronization with the respiratory synchronization trigger AT _{n + 1} .

In addition, the trigger determination unit 92 determines whether or not the next respiratory synchronization trigger AT _{n + 2} has occurred before the predetermined time TX has elapsed since the start of the respiratory synchronization scan RS _{n + 1} . Referring to FIG. 5, since the breathing of the subject 12 becomes shallow after time t _{n + 1} and the respiratory signal S remains lower than the trigger level TL, the next respiratory synchronization trigger AT _{n + 2} does not occur. . Therefore, the trigger determination unit 92 determines that the next respiratory synchronization trigger AT _{n + 2} has not occurred before the predetermined time TX has elapsed since the start of the respiratory synchronization scan RS _{n + 1} . In this case, MRI device 100 starts breathing asynchronous scan BN _1. Therefore, the next respiratory synchronization trigger AT _{n + 2} does not occur, but the MRI apparatus 100 can scan the subject 12.

Furthermore, the trigger determination unit 92 determines whether or not the next respiratory synchronization trigger AT _{n + 3} has occurred before the predetermined time TX has elapsed since the start of the respiratory asynchronous scan BN ₁ . Referring to FIG. 5, after time t _{n + 1} , the respiration signal S remains lower than the trigger level TL, so that the respiration synchronization trigger AT _{n + 3} does not occur. Therefore, the trigger determination unit 92 determines that the next respiratory synchronization trigger AT _{n + 3} has not occurred before the predetermined time TX has elapsed since the start of the respiratory asynchronous scan BN ₁ . In this case, MRI device 100 starts the next breath asynchronous scan BN _2. Therefore, the next respiratory synchronization trigger AT _{n + 3} does not occur, but the MRI apparatus 100 can scan the subject 12.

Similarly, after time t _{n + 3} , a breath asynchronous scan is executed, and the last breath asynchronous scan BN _z is started at time t _z . When data from the last breath asynchronous scan BN _z is collected, the imaging is finished.

  In the first mode, when the next breath synchronization trigger does not occur during the predetermined time TX, a breath asynchronous scan is executed. Therefore, even if the respiratory synchronization trigger does not occur due to the subject 12 sleeping during imaging, the scan can be continuously executed.

  In the first embodiment, the respiratory signal S is obtained by collecting navigator echoes from the region crossing the diaphragm and detecting the position of the diaphragm based on the collected navigator echoes. However, instead of collecting navigator echoes, a respiratory signal S may be obtained using a bellows.

  In the first embodiment, the start time of the predetermined time TX set by the time setting means 93 coincides with the start time of the scan. However, if the next scan can be executed, the start point of the predetermined time TX does not necessarily need to coincide with the start point of the scan (see FIG. 6).

FIG. 6 is a diagram illustrating predetermined times at different start points.
FIG. 6 shows two predetermined times TX _e and TX _f . Beginning a predetermined time TX _e is consistent with the end t _e of the scan, the start time of the predetermined time TX _f coincides with the scanning of the middle point t _f. When the predetermined time set by the time setting means 93 is TX _e , the respiratory asynchronous scan BN _j starts according to the predetermined time TX _e . Specifically, the respiratory asynchronous scan BN _j is started when the next respiratory synchronization trigger is not generated even after a predetermined time TX _e has elapsed from the end time t _e of the respiratory synchronous scan RS _i .

On the other hand, when the predetermined time set by the time setting means 93 is TX _f , breathing asynchronous BN _j starts according to the predetermined time TX _f . Specifically, the respiratory asynchronous scan BN _j starts when the next respiratory synchronization trigger is not generated even after a predetermined time TX _f has elapsed from the mid-point t _f of the respiratory synchronous scan RS _i .

  As shown in FIG. 6, if the next scan can be executed, the start time of the predetermined time does not necessarily need to coincide with the start time of the scan.

  Further, the predetermined time TX may be changed during imaging of the subject. If the predetermined time TX can be changed during the imaging of the subject, the predetermined time TX can be adjusted in accordance with the change in the respiratory cycle even if the respiratory cycle of the subject changes during the imaging. Furthermore, it is possible to perform imaging suitable for the respiratory motion of the subject.

  In the first embodiment, the time setting means 93 sets the predetermined time TX when the operator 13 inputs the predetermined time TX from the input device 10. However, the time setting means 93 may analyze the respiratory signal S and automatically set the predetermined time TX.

(2) Second Embodiment FIG. 7 is a schematic diagram of an MRI apparatus according to a second embodiment.

  The MRI apparatus 200 of the second form includes the scan execution determination means 94, but the other configurations are the same as those of the MRI apparatus 100 of the first form. Therefore, with regard to the MRI apparatus 200 of the second embodiment, the scan execution determination unit 94 will be mainly described.

  If the next breath synchronization trigger does not occur even after a predetermined time TX has elapsed since the breath synchronization scan or the breath asynchronous scan, the scan execution determination means 94 indicates that the breath synchronization trigger has not occurred based on the breath signal S. Also, it is determined whether or not to execute a respiratory asynchronous scan for collecting magnetic resonance signals from the subject 12. The central processing unit 9 is an example of the scan execution determination unit 94 and functions as the scan execution determination unit 94 by executing a predetermined program.

  The operation of the MRI apparatus 200 according to the second embodiment will be described below with reference to FIG.

  FIG. 8 is a diagram illustrating an example of a scan executed in the second mode. FIG. 8A is a diagram showing a respiratory signal, and FIG. 8B is a diagram showing a period during which a scan is executed.

Note that since the respiratory synchronization scans RS _{1 to} RS _{n + 1} are executed in the same procedure as in the first embodiment, the description thereof is omitted.

The trigger determination unit 92 (see FIG. 7) determines whether or not the next respiratory synchronization trigger AT _{n + 2} has occurred before the predetermined time TX has elapsed since the start of the respiratory synchronization scan RS _{n + 1} . Referring to FIG. 8, the next respiratory synchronization trigger AT _{n + 2} is generated at a time point t _{n + 2} when a predetermined time TX has elapsed since the respiratory synchronization scan RS _{n + 1} has been started, and further, a time ΔT has elapsed. That is, the next respiratory synchronization trigger AT _{n + 2} has not occurred before the predetermined time TX has elapsed since the start of the respiratory synchronization scan RS _{n + 1} (time point t _{n + 1 to} t _{n + 1} ′). Therefore, the trigger determination unit 92 determines that the next respiratory synchronization trigger AT _{n + 2} has not occurred before the predetermined time TX has elapsed since the start of the respiratory synchronization scan RS _{n + 1} . When the trigger determination unit 92 determines that the next breath synchronization trigger AT _{n + 2} has not occurred, the scan execution determination unit 94 (see FIG. 7) determines whether or not to execute a breath asynchronous scan. This determination is made as follows.

The scan execution determination means 94 first determines whether or not the signal value Va of the respiratory signal S at the time point t _{n + 1} ′ is included in a predetermined range AW (the hatched range shown in FIG. 8). The predetermined range AW represents a range in which body movement due to respiration is small. The predetermined range AW may be set by the operator 13 or may be automatically set by the MRI apparatus 200 by analyzing the respiratory signal S.

In FIG. 8, since the signal value Va of the respiratory signal S at the time point t _{n + 1} ′ is out of the predetermined range AW, the scan execution determination means 94 includes the respiratory signal S in the predetermined range AW at the time point t _{n + 1} ′. Judge that it is not. If the respiratory asynchronous scan is started when the respiratory signal S is not included in the predetermined range AW, the respiratory asynchronous scan is likely to be executed while body movement due to respiration is large. If the asynchronous breathing scan is performed while the body motion due to breathing is large, it causes a body motion artifact. Therefore, it is desirable that the respiratory asynchronous scan be performed while the body motion is as small as possible. Therefore, the scan execution determining means 94 determines not to execute the respiratory asynchronous scan when it is determined that the respiratory signal S is not included in the predetermined range AW at the time t _{n + 1} ′.

After elapse of time t _{n + 1} ′, the respiratory signal S gradually increases but decreases again and reaches the trigger level TL at time t _{n + 2} . Therefore, the trigger generation means 91 (see FIG. 7) generates the respiratory synchronization trigger AT _{n + 2} at the time point t _{n + 2} . Since the respiratory synchronization trigger AT _{n + 2} is generated, the MRI apparatus 200 executes the respiratory synchronization scan RS _{n + 2} in synchronization with the respiratory synchronization trigger AT _{n + 2} .

The trigger determination unit 92 determines whether or not the next respiratory synchronization trigger AT _{n + 3} has occurred before the predetermined time TX has elapsed since the start of the respiratory synchronization scan RS _{n + 2} . Referring to FIG. 8, since the breathing of the subject 12 becomes shallow after the time t _{n + 2} and the respiratory signal S remains lower than the trigger level TL, the respiratory synchronization trigger AT _{n + 3} does not occur. Therefore, the trigger determination unit 92 determines that the next respiratory synchronization trigger AT _{n + 3} has not occurred before the predetermined time TX has elapsed since the start of the respiratory synchronization scan RS _{n + 2} . When the trigger determination unit 92 determines that the next respiratory synchronization trigger AT _{n + 3} has not occurred, the scan execution determination unit 94 (see FIG. 7) reads the respiratory signal S at the time t _{n + 3} when the predetermined time TX has elapsed. It is determined whether or not the signal value Vb is included in a predetermined range AW (a hatched range shown in FIG. 8). In FIG. 8, since the signal value Vb of the respiratory signal S at the time point t _{n + 3} is included in the predetermined range AW, the scan execution determination unit 94 includes the respiratory signal S in the predetermined range AW at the time point t _{n + 3} . Judge that When the respiratory asynchronous scan BN ₁ is started when the respiratory signal S is included in the predetermined range AW, the respiratory asynchronous scan BN ₁ is likely to be executed while the body movement due to respiration is small. Therefore, when it is determined that the respiratory signal S is included in the predetermined range AW at the time point t _{n + 3} , the scan execution determination unit 94 determines to execute the respiratory asynchronous scan BN ₁ . In response to this determination, the MRI apparatus 200 starts the respiratory asynchronous scan BN ₁ .

The trigger determination unit 92 determines whether or not the next respiratory synchronization trigger AT _{n + 4} has occurred before the predetermined time TX has elapsed since the start of the respiratory asynchronous scan BN ₁ . Referring to FIG. 8, since the breathing of the subject 12 becomes shallow after the time point t _{n + 2} and the respiratory signal S remains lower than the trigger level TL, the respiratory synchronization trigger AT _{n + 4} does not occur. Therefore, the trigger determination unit 92 determines that the next respiratory synchronization trigger AT _{n + 4} has not occurred before the predetermined time TX has elapsed since the start of the respiratory asynchronous scan BN ₁ . When the trigger determination unit 92 determines that the next respiratory synchronization trigger AT _{n + 4} has not occurred, the scan execution determination unit 94 (see FIG. 7) reads the respiratory signal S at the time t _{n + 4} when the predetermined time TX has elapsed. It is determined whether or not the signal value Vc is included in a predetermined range AW (the hatched range shown in FIG. 8). In FIG. 8, since the signal value Vc of the respiratory signal S at the time point t _{n + 4} is included in the predetermined range AW, the scan execution determination unit 94 includes the respiratory signal S in the predetermined range AW at the time point t _{n + 4} . Judge that Thus, the scan execution determination means 94 determines to execute the breathing asynchronous scan BN _2. In response to this determination, MRI apparatus 200 starts breathing asynchronous scan BN _2.

  Similarly, scanning is executed while judging whether or not the respiration signal S is included in the predetermined range AW, and when all necessary data is collected, the imaging is terminated.

  In the second embodiment, if the respiratory synchronization trigger has not occurred before the predetermined time TX has elapsed, it is determined whether or not the respiratory signal S is included in the predetermined range AW before the respiratory asynchronous scan is started. Deciding. Therefore, when it is considered that it is difficult to perform a scan while the body motion due to respiration is small, the respiratory asynchronous scan is not started, so that the body motion artifact can be reduced.

(3) Third Embodiment FIG. 9 is a schematic diagram of an MRI apparatus according to a third embodiment.

  The MRI apparatus 300 according to the third embodiment includes data rejection determination means 95 that determines whether or not the data collected by the scan is to be rejected. Other configurations are the same as those of the MRI apparatus 100 according to the first embodiment. The same. Therefore, regarding the MRI apparatus 300 according to the third embodiment, the data rejection determination unit 95 will be mainly described with reference to FIG. The central processing unit 9 is an example of the data rejection determination unit 95, and functions as the data rejection determination unit 95 by executing a predetermined program.

  FIG. 10 is a diagram illustrating an example of a scan executed in the third mode. FIG. 10A is a diagram showing a respiratory signal, and FIG. 10B is a diagram showing a period during which a scan is executed.

Note that since the respiratory synchronization scans RS _{1 to} RS _{n + 1} are executed in the same procedure as in the first embodiment, the description thereof is omitted.

The trigger determination unit 92 determines whether or not the next respiratory synchronization trigger AT _{n + 2} has occurred before the predetermined time TX has elapsed since the start of the respiratory synchronization scan RS _{n + 1} . Referring to FIG. 10, the respiratory signal S remains lower than the trigger level TL before the predetermined time TX has elapsed after the respiratory synchronization scan RS _{n + 1} is started (time t _{n + 1 to} t _{n + 2} ). Therefore, the respiratory synchronization trigger AT _{n + 2} does not occur. Therefore, the trigger determination unit 92 determines that the next respiratory synchronization trigger AT _{n + 2} has not occurred before the predetermined time TX has elapsed since the start of the respiratory synchronization scan RS _{n + 1} . In this case, MRI device 300 starts breathing asynchronous scan BN _1. Therefore, the MRI apparatus 300 can execute the scan of the subject 12 even when the next respiratory synchronization trigger AT _{n + 2} has not occurred.

After the respiratory asynchronous scan BN ₁ is completed, the data rejection determination unit 95 (see FIG. 9) determines whether to reject the data collected by the respiratory asynchronous scan BN ₁ . This determination is made as follows.

The data rejection determination unit 95 first determines whether or not the signal value Va ′ of the respiratory signal S at the time point t _{n + 2} ′ when the respiratory asynchronous scan BN ₁ ends is included in the predetermined range AW. The predetermined range AW represents a range in which body movement due to respiration is small. The predetermined range AW may be set by the operator 13 or may be automatically set by the MRI apparatus 200 by analyzing the respiratory signal S.

In FIG. 10, since the signal value Va ′ of the respiratory signal S is included in the predetermined range AW at the time point t _{n + 2} ′, the data rejection determination unit 95 determines that the respiratory signal S is in the predetermined range AW at the time point t _{n + 2} ′. Is determined to be included. When the respiration signal S at the time when the respiration asynchronous scan BN ₁ ends is included in the predetermined range AW, most of the data collected by the respiration asynchronous scan BS ₁ is collected while the body movement due to respiration is small. There is a high possibility. Therefore, even when an image is reconstructed using the data collected by the respiratory asynchronous scan BN _1, it would not become a cause of most motion artifacts. Therefore, the data rejection determination unit 95 determines to employ the data collected by the respiratory asynchronous scan BN ₁ as data for image reconstruction.

In addition, the trigger determination unit 92 determines whether or not the next respiration synchronization trigger AT _{n + 3} has occurred before a predetermined time TX has elapsed since the start of the respiration asynchronous scan BN ₁ (time point t _{n + 2 to} t _{n + 3} ). to decide. Referring to FIG. 10, the respiratory signal S exceeds the trigger level TL between time points t _{n + 2 to} t _{n + 3} , but after exceeding the trigger level TL, the respiration signal S changes to the trigger level TL between time points t _{n + 2 to} t _{n + 3.} Has not returned. Therefore, the next respiratory synchronization trigger AT _{n + 3} does not occur before the predetermined time TX has elapsed since the start of the respiratory asynchronous scan BN ₁ (time point t _{n + 2 to} t _{n + 3} ). In this case, MRI device 300 starts breathing asynchronous scan BN _2.

After the breath asynchronous scan BN ₂ is completed, the data rejection determination unit 95 determines whether to reject the data collected by the respiratory asynchronous scan BN ₂ . In order to determine whether or not to reject the data, the data rejection determination means 95 first includes the signal value Vb ′ of the respiratory signal S at the time point t _{n + 3} ′ when the respiratory asynchronous scan BN ₂ ends within the predetermined range AW. It is determined whether or not. In FIG. 10, since the signal value Vb ′ of the respiratory signal S is out of the predetermined range AW at the time point t _{n + 3} ′, the data rejection determination unit 95 causes the respiratory signal S to fall within the predetermined range AW at the time point t _{n + 3} ′. Judged not included. If the respiratory signal S at the time point t _{n + 3} ′ when the respiratory asynchronous scan BN ₂ ends is outside the predetermined range AW, most of the data collected by the respiratory asynchronous scan BN ₂ It is likely that it was collected. Since reconstructing an image using data collected while body movement due to respiration is a cause of body movement artifacts, the data collected by respiratory asynchronous scan BN ₂ is used as data for image reconstruction. It is desirable not to use it. Therefore, data rejecting determining means 95, data collected by the respiratory asynchronous scan BN ₂ is judged to be rejected.
Similarly, the scan is continued while determining whether or not to reject the data.

  In the third embodiment, when the respiratory signal S is out of the predetermined range AW, it is determined to reject the data collected by the respiratory asynchronous scan. Therefore, data collected while body movement due to respiration is large is not adopted as data when reconstructing an image, so an image with reduced body movement artifacts can be obtained.

  In the third embodiment, it is determined whether or not to discard data only when a respiratory asynchronous scan is executed. However, it may be determined whether or not to reject data even when a breathing synchronization scan is executed.

(4) Fourth Embodiment In the second embodiment, an MRI apparatus 200 having a scan execution determination unit is described. In a third embodiment, an MRI apparatus 300 having a data rejection determination unit is described. In the fourth embodiment, an MRI apparatus having both scan execution determination means and data rejection determination means will be described.

FIG. 11 is a schematic view of the MRI apparatus of the fourth embodiment.
The MRI apparatus 400 of the fourth embodiment includes data rejection determination means 95 that determines whether or not the data collected by the scan is to be rejected, but the other configuration is the MRI apparatus 200 ( (See FIG. 7). Therefore, the data rejection determination unit 95 will be mainly described for the MRI apparatus 400 of the fourth embodiment. The central processing unit 9 is an example of the data rejection determination unit 95, and functions as the data rejection determination unit 95 by executing a predetermined program.

  The operation of the MRI apparatus 400 according to the fourth embodiment will be described below with reference to FIG.

  FIG. 12 is a diagram illustrating an example of a scan executed in the fourth mode. FIG. 12A is a diagram showing a respiratory signal, and FIG. 12B is a diagram showing a period during which a scan is executed.

Incidentally, respiratory gated scan _RS 1 _{to RS n + 2} is executed at the same steps as the second embodiment (see FIG. 8), description thereof is omitted.

After the respiration synchronization scan RS _{n + 2} ends, the data rejection determination means 95 (see FIG. 11) includes the signal value Va ′ of the respiration signal S at the time t _{n + 2} ′ when the respiration synchronization scan RS _{n + 2} ends within the predetermined range AW. It is determined whether or not. In FIG. 12, since the signal value Va ′ of the respiratory signal S is included in the predetermined range AW at the time point t _{n + 2} ′, the data rejection determination unit 95 causes the respiratory signal S to fall within the predetermined range AW at the time point t _{n + 2} . Judged to be included. When the respiratory signal S at the end of the respiratory synchronization scan RS _{n + 2} is included in the predetermined range AW, it is determined that the data collected by the respiratory synchronization scan RS _{n + 2} is adopted as image reconstruction data.

The trigger determination unit 92 determines whether or not the next respiratory synchronization trigger AT _{n + 3} has occurred before the predetermined time TX has elapsed since the start of the respiratory synchronization scan RS _{n + 2} . Referring to FIG. 12, the respiratory signal S remains lower than the trigger level TL before a predetermined time TX has elapsed since the start of the respiratory synchronization scan RS _{n + 2} (time point t _{n + 2 to} t _{n + 3} ). Therefore, the respiratory synchronization trigger AT _{n + 3} does not occur. Therefore, the trigger determination unit 92 determines that the next respiratory synchronization trigger AT _{n + 3} has not occurred before the predetermined time TX has elapsed since the start of the respiratory synchronization scan RS _{n + 2} . When the trigger determination unit 92 determines that the next respiratory synchronization trigger AT _{n + 3} has not occurred, the scan execution determination unit 94 (see FIG. 11) reads the respiratory signal S at the time t _{n + 3} when the predetermined time TX has elapsed. It is determined whether or not the signal value Vb is included in a predetermined range AW (a hatched range shown in FIG. 12). In FIG. 12, since the signal value Vb of the respiratory signal S at the time point t _{n + 3} is included in the predetermined range AW, the scan execution determination unit 94 includes the respiratory signal S in the predetermined range AW at the time point t _{n + 3} . Judge that In this case, MRI device 400 starts breathing asynchronous scan BN _1.

After the breath asynchronous scan BN ₁ is finished, the data rejection determination means 95 determines whether or not the signal value Vb ′ of the breath signal S at the time t _{n + 3} ′ when the breath asynchronous scan BN ₁ is finished is included in the predetermined range AW. Judging. In FIG. 12, since the signal value Vb ′ of the respiratory signal S is out of the predetermined range AW, the data rejection determining unit 95 determines that the respiratory signal S is not included in the predetermined range AW at the time point t _{n + 3} ′. To do. When the respiratory signal S at the time point t _{n + 3} ′ when the respiratory asynchronous scan BN ₁ ends is out of the predetermined range AW, the data rejection determination unit 95 determines that the data collected by the respiratory asynchronous scan BN ₁ is rejected.

  Similarly, the scan is executed while determining whether to start the scan and whether to reject the data, and when all necessary data is collected, the imaging is terminated.

  In the fourth embodiment, if the respiratory synchronization trigger does not occur before the predetermined time TX elapses, it is determined whether or not the respiratory signal S is included in the predetermined range AW before the respiratory asynchronous scan is started. Deciding. Therefore, when it is considered that it is difficult to perform a scan while the body motion due to respiration is small, the respiratory asynchronous scan is not started, so that the body motion artifact can be reduced.

  Further, in the fourth embodiment, even if the respiratory asynchronous scan is executed, if the respiratory signal S at the end of the respiratory asynchronous scan is out of the predetermined range AW, it is determined that the data collected by the respiratory asynchronous scan is rejected. To do. Therefore, if the body movement due to breathing is small at the start of the asynchronous breathing scan but the body movement due to breathing is large at the end of the asynchronous breathing scan, the collected data will be used when the image is reconstructed. Since it is not adopted as the data, body movement artifacts can be further reduced.

  In the fourth embodiment, it is determined whether or not to discard data only when a respiratory asynchronous scan is executed. However, it may be determined whether or not to reject data even when a breathing synchronization scan is executed.

In the first to fourth embodiments, examples using a magnetic resonance imaging apparatus are described. However, if the present invention is a modality that scans in synchronization with the respiratory synchronization trigger, CT (Computed
Tomography) and other modalities other than magnetic resonance imaging apparatus can be applied.

2 Magnetic field generator 3 Table 4 Reception coil 5 Sequencer 6 Transmitter 7 Gradient magnetic field power supply 8 Receiver 9 Central processing unit 10 Input device 11 Display device 12 Subject 13 Operator 21 Bore 22 Superconducting coil 23 Gradient coil 24 Transmitting coil 31 Cradle 91 trigger generation means 92 trigger determination means 93 time setting means 94 scan execution determination means 95 data rejection determination means 100, 200, 300, 400 MRI apparatus

Claims (13)

Trigger generating means for generating a respiratory synchronization trigger related to the respiratory cycle based on the respiratory signal of the subject;
Scanning means for performing a respiratory synchronization scan, which is a scan synchronized with the respiratory synchronization trigger, on the subject ;
A photographing device having
The scanning means includes
If the next respiratory synchronization trigger does not occur even after a predetermined time has elapsed since the respiratory synchronization scan, a respiratory asynchronous scan that performs a scan even if the respiratory synchronization trigger has not occurred is performed on the subject . Shooting device.
The imaging device according to claim 1, wherein if the respiratory synchronization trigger does not occur even after the predetermined time has elapsed from the respiratory asynchronous scan, the next respiratory asynchronous scan is executed.
Trigger generating means for generating a respiratory synchronization trigger related to a respiratory cycle based on a respiratory signal of the subject;
Scanning means for performing a respiratory synchronization scan , which is a scan synchronized with the respiratory synchronization trigger, on the subject ;

If the next breath synchronization trigger does not occur even after the predetermined time has elapsed since the breath synchronization scan, a breath asynchronous scan is performed on the subject even if the breath synchronization trigger has not occurred. Scan execution determination means for determining whether or not based on the respiratory signal ;

I have a,
The scanning means includes
An imaging apparatus that executes the breath asynchronous scan when the scan execution determination unit determines to execute the breath asynchronous scan.
The scan execution determination means includes
The imaging apparatus according to claim 3, wherein it is determined whether to execute the respiratory asynchronous scan based on whether the value of the respiratory signal of the subject is out of a predetermined range.
The scan execution determination means includes
5. The method according to claim 3 , wherein if the respiratory synchronization trigger does not occur even after the predetermined time has elapsed from the respiratory asynchronous scan, whether or not to execute the next respiratory asynchronous scan is determined based on the respiratory signal. The imaging device described.
The imaging device according to claim 1, further comprising: a trigger determination unit that determines whether or not the respiratory synchronization trigger has occurred before the predetermined time has elapsed.
The imaging apparatus according to claim 1, further comprising a data rejection determination unit configured to determine whether to reject data collected by the respiratory synchronization scan or the respiratory asynchronous scan.
The data rejection determination means is
The imaging apparatus according to claim 7, wherein when the value of the respiratory signal of the subject is out of a predetermined range, it is determined that the data collected by the respiratory synchronous scan or the respiratory asynchronous scan is to be rejected.
The photographing apparatus according to claim 1, further comprising a time setting unit that sets the predetermined time. The imaging device according to claim 9, further comprising an input device for inputting the predetermined time. The starting point of the predetermined time is
The imaging device according to any one of claims 1 to 10, which coincides with a start time of the scan, an end time of the scan, or an intermediate time of the scan.
The imaging device according to claim 1, wherein the value of the predetermined time is changeable. The imaging apparatus according to claim 1, wherein the imaging apparatus is a magnetic resonance imaging apparatus or a CT apparatus.

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