JP2013180051A - Magnetic resonance imaging equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide magnetic resonance imaging equipment capable of appropriately setting an interval of reporting respiration timing according to a subject.SOLUTION: In a magnetic resonance imaging apparatus according to an embodiment, an implementation part implements preparation scan for collecting data indicating an amount of movement resulting from respiration of a subject while reporting respiration timing to the subject at a prescribed repetition interval for two or more times with various repetition intervals before main scan. A measurement part measures a length of a resting period which is a period during which such a state that the amount of the movement resulting from the respiration of the subject is smaller than a prescribed amount continues, for each of the plurality of repetition intervals, on the basis of the data collected by the preparation scan. A sequence setting part specifies the repetition interval with which the length of the resting period becomes longest, and sets a sequence for the main scan for collecting data for image generation in the resting period while reporting the respiration timing to the subject at the specified repetition interval.

Description

  Embodiments described herein relate generally to a magnetic resonance imaging apparatus.

  2. Description of the Related Art Conventionally, in a magnetic resonance imaging apparatus, as an imaging method for preventing image quality deterioration due to breathing, respiratory synchronization imaging is known in which imaging is performed in synchronization with the breathing of a subject. In such respiratory synchronized imaging, there is known a method for notifying a subject of sound for guiding the timing of breathing during imaging in order to keep the respiratory cycle constant.

Parenty et al. “Rental Artery Evaluation in Chronic Kidney Disease; Radiology: Volume 259: Number 2 pp 592-601, 2011

  The problem to be solved by the present invention is to provide a magnetic resonance imaging apparatus capable of appropriately setting an interval for reporting the breathing timing according to the subject.

  The magnetic resonance imaging apparatus according to the embodiment includes an execution unit, a measurement unit, and a sequence setting unit. The execution unit performs a preparatory scan that collects data indicating the amount of movement of the subject through respiration while notifying the subject at a predetermined repetition interval before the main scan at a plurality of repetition intervals. Run. The measurement unit measures the length of a stationary period, which is a period in which the movement amount due to breathing of the subject continues to be smaller than a predetermined amount, at a plurality of repetition intervals, based on data collected by the preparation scan. . The sequence setting unit specifies a repetition interval in which the length of the stationary period is the longest, and collects data for image generation during the stationary period while notifying the subject of breathing timing at the identified repetition interval Set the sequence for.

FIG. 1 is a diagram showing a configuration of an MRI apparatus according to the present embodiment. FIG. 2 is a functional block diagram showing a detailed configuration of the magnetic resonance imaging apparatus 100 according to the present embodiment. FIG. 3 is a diagram illustrating an example of a preparation scan executed by the execution unit 17a according to the present embodiment. FIG. 4 is a diagram showing an example of a sequence for the main scan set by the sequence setting unit 17c according to the present embodiment. FIG. 5 is a flowchart showing a processing procedure of respiratory synchronization imaging by the MRI apparatus 100 according to the present embodiment.

  Hereinafter, a magnetic resonance imaging (MRI) apparatus according to an embodiment will be described with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of an MRI apparatus according to the present embodiment. As shown in the figure, the MRI apparatus 100 according to this embodiment includes a static magnetic field magnet 1, a gradient magnetic field coil 2, a gradient magnetic field power source 3, a bed 4, a bed control unit 5, a transmission RF coil 6, a transmission unit 7, and a reception. An RF coil 8, a receiving unit 9, and a computer system 10 are provided.

  The static magnetic field magnet 1 is a magnet formed in a hollow cylindrical shape, and generates a uniform static magnetic field in an internal space. As the static magnetic field magnet 1, for example, a permanent magnet, a superconducting magnet or the like is used.

  The gradient magnetic field coil 2 is a coil formed in a hollow cylindrical shape, and is disposed inside the static magnetic field magnet 1. The gradient magnetic field coil 2 is formed by combining three coils corresponding to the X, Y, and Z axes orthogonal to each other, and these three coils are individually supplied with current from a gradient magnetic field power source 3 to be described later. In response, a gradient magnetic field whose magnetic field strength changes along the X, Y, and Z axes is generated. The Z-axis direction is the same direction as the static magnetic field.

  Here, the gradient magnetic fields of the X, Y, and Z axes generated by the gradient magnetic field coil 2 correspond to, for example, the slice selection gradient magnetic field Gs, the phase encoding gradient magnetic field Ge, and the readout gradient magnetic field Gr, respectively. . The slice selection gradient magnetic field Gs is used to arbitrarily determine an imaging section. The phase encoding gradient magnetic field Ge is used to change the phase of the magnetic resonance signal in accordance with the spatial position. The readout gradient magnetic field Gr is used for changing the frequency of the magnetic resonance signal in accordance with the spatial position.

  The gradient magnetic field power supply 3 is a device that supplies a current to the gradient coil 2 based on pulse sequence execution data sent from the computer system 10.

  The couch 4 is an apparatus including a couchtop 4a on which the subject S is placed, and the couchtop 4a is tilted in a state where the subject S is placed under the control of a couch controller 5 described later. The magnetic field coil 2 is inserted into the cavity (imaging port). Usually, the bed 4 is installed such that the longitudinal direction is parallel to the central axis of the static magnetic field magnet 1.

  The couch controller 5 is a device that controls the couch 4 and drives the couch 4 to move the top 4a in the longitudinal direction and the vertical direction.

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

  The transmission unit 7 is a device that transmits a high-frequency pulse corresponding to the Larmor frequency to the transmission RF coil 6 based on the pulse sequence execution data transmitted from the computer system 10, and includes an oscillation unit, a phase selection unit, a frequency conversion unit, an amplitude A modulation unit, a high-frequency power amplification unit, and the like are included. The oscillation unit generates a high-frequency signal having a resonance frequency unique to the target nucleus in the static magnetic field. The phase selection unit selects the phase of the high-frequency signal. The frequency conversion unit converts the frequency of the high-frequency signal output from the phase selection unit. The amplitude modulation unit modulates the amplitude of the high-frequency signal output from the frequency modulation unit according to, for example, a sinc function. The high frequency power amplification unit amplifies the high frequency signal output from the amplitude modulation unit. As a result of the operation of each of these units, the transmission unit 7 transmits a high-frequency pulse corresponding to the Larmor frequency to the transmission RF coil 6.

  The reception RF coil 8 is a coil disposed inside the gradient magnetic field coil 2 and receives a magnetic resonance signal radiated from the subject due to the influence of the high-frequency magnetic field. When receiving the magnetic resonance signal, the reception RF coil 8 outputs the magnetic resonance signal to the receiving unit 9.

  The receiving unit 9 is a device that generates magnetic resonance signal data based on the magnetic resonance signal output from the reception RF coil 8 based on the pulse sequence execution data sent from the computer system 10. When receiving the magnetic resonance signal data, the receiving unit 9 transmits the magnetic resonance signal data to the computer system 10. The receiving unit 9 may be provided on the gantry device side including the static magnetic field magnet 1 and the gradient magnetic field coil 2.

The computer system 10 is a device that performs overall control of the MRI apparatus 100, data collection, image reconstruction, and the like, and includes an interface unit 11, a data collection unit 12, a data processing unit 13, a storage unit 14, a display unit 15, and an input unit. 16 and a control unit 17.
The interface unit 11 is connected to the gradient magnetic field power source 3, the bed control unit 5, the transmission unit 7, and the reception unit 9, and inputs and outputs signals that are exchanged between these connected units and the computer system 10. A processing unit to be controlled.

  The data collection unit 12 is a processing unit that collects magnetic resonance signal data transmitted from the reception unit 9 via the interface unit 11. When collecting the magnetic resonance signal data, the data collecting unit 12 stores the collected magnetic resonance signal data in the storage unit 14.

  The data processing unit 13 performs post-processing, that is, reconstruction processing such as Fourier transform, on the magnetic resonance signal data stored in the storage unit 14, thereby obtaining spectrum data of desired nuclear spins in the subject S or A processing unit that generates image data.

  The storage unit 14 is a storage unit that stores the magnetic resonance signal data collected by the data collection unit 12 and the image data generated by the data processing unit 13 for each subject S. The display unit 15 is a device that displays various information such as spectrum data or image data under the control of the control unit 17. As the display unit 15, a display device such as a liquid crystal display can be used.

  The input unit 16 is a device that receives various operations and information input from an operator. As the input unit 16, a pointing device such as a mouse or a trackball, a selection device such as a mode change switch, or an input device such as a keyboard can be used as appropriate.

  The control unit 17 includes a CPU, a memory, and the like (not shown), and is a processing unit that comprehensively controls the MRI apparatus 100.

  The notification unit 18 notifies the subject of breathing timing. In this embodiment, the alerting | reporting part 18 alert | reports a respiratory timing with an audio | voice. For example, the notification unit 18 sends a pre-recorded voice such as “suck” and “vomit” to the speaker 19 as an electrical signal. The speaker 19 converts an electric signal into vibration and outputs sound.

  The overall configuration of the MRI apparatus 100 according to this embodiment has been described above. Under such a configuration, the MRI apparatus 100 according to the present embodiment notifies the subject of respiratory timing at regular intervals and performs respiratory synchronization imaging. Conventionally, in such synchronized breathing imaging, for example, the timing of breathing and the timing of breathing are notified to the subject by voice, and data for image generation is collected in a state where there is little movement of the abdomen. However, the timing when the abdomen moves less is different depending on the subject, and also differs depending on the interval for reporting the breathing timing. For this reason, conventionally, it has not been known whether or not the interval for informing the breathing timing is appropriate unless the subject is actually imaged.

  Therefore, the MRI apparatus 100 according to the present embodiment repeatedly performs a preparatory scan that collects data indicating the amount of movement due to breathing of the subject while informing the subject of breathing timing at a predetermined repetition interval before the main scan. Execute multiple times at different intervals. In addition, the MRI apparatus 100 measures the length of a stationary period that is a period in which the movement amount of the subject due to breathing is smaller than a predetermined amount at a plurality of repetition intervals based on the data collected by the preparation scan. To do. Then, the MRI apparatus 100 specifies the repetition interval in which the length of the stationary period is the longest, and collects data for image generation in the stationary period while notifying the subject of the breathing timing at the identified repeating interval. Set the sequence.

  In other words, the MRI apparatus 100 according to the first embodiment specifies the repetition interval in which the stationary period with the smallest movement of the subject is the longest by changing the repetition interval before the main scan and executing the preparation scan a plurality of times. Then, the sequence for the main scan is set. As a result, the interval for reporting the breathing timing can be appropriately set according to the subject.

  Hereinafter, the MRI apparatus 100 will be described in detail. FIG. 2 is a functional block diagram showing a detailed configuration of the magnetic resonance imaging apparatus 100 according to the present embodiment. 2 illustrates the gradient magnetic field power source 3, the transmission unit 7, the reception unit 9, the computer system 10, the interface unit 11, the data collection unit 12, the storage unit 14, the input unit 16, and the control among the units illustrated in FIG. The part 17 and the alerting | reporting part 18 are shown.

  As illustrated in FIG. 2, the storage unit 14 includes an imaging condition storage unit 14a, a collected data storage unit 14b, and a threshold storage unit 14c. The control unit 17 includes an execution unit 17a, a measurement unit 17b, a sequence setting unit 17c, a threshold setting unit 17d, a detection unit 17e, and a notification control unit 17f.

  The imaging condition storage unit 14a stores imaging conditions. Specifically, the imaging condition storage unit 14a stores various imaging parameter values for defining sequences used in various scans as imaging conditions.

  The collected data storage unit 14b stores data (magnetic resonance signal data) collected by the data collecting unit 12.

  The threshold storage unit 14c stores a threshold for determining that the amount of movement of the subject is small during the main scan. The threshold stored by the threshold storage unit 14c is set by a threshold setting unit 17d described later.

  The execution unit 17a executes various scans. Specifically, the execution unit 17a performs a preparatory scan that collects data indicating the amount of movement due to breathing of the subject while reporting the breathing timing to the subject at a predetermined repetition interval before the main scan. Change and run multiple times. This preparation scan is executed, for example, during a breath holding practice performed by the subject before the main scan.

  Here, for example, each time the preparation scan is executed, the execution unit 17a receives a designation of a repetition interval from the operator, and performs a preparation scan using the received repetition interval. In this case, the execution unit 17a executes the preparation scan as many times as instructed by the operator.

  For example, the execution unit 17a may perform a preparation scan using a plurality of repetition intervals designated in advance by the operator. In this case, for example, a plurality of intervals are set stepwise as the repetition interval. Then, the execution unit 17a executes the preparatory scan for the number of repetition intervals designated by the operator.

  Note that the execution unit 17a may execute the preparatory scan only once or repeatedly for one repetition interval.

  FIG. 3 is a diagram illustrating an example of a preparation scan executed by the execution unit 17a according to the present embodiment. As shown in FIG. 3, for example, the execution unit 17a executes monitor scan Navi in synchronization with the voice guide while repeatedly reporting the voice guides V1 and V2 at the repeat interval Trep as a preparation scan. At this time, the execution unit 17a instructs the notification unit 18 to notify the voice guides V1 and V2 at the repetition interval Trep. At this time, for example, the execution unit 17a instructs the notification unit 18 to generate a “suck” voice as the voice guide V1 and to generate a “vomit” voice as the voice guide V2.

  Further, for example, the execution unit 17a executes a scan for collecting magnetic resonance signals called navigator signals from an area set near the diaphragm of the subject as the monitor scan Navi. The amount of movement of the abdomen can be detected by detecting the boundary between the liver and lungs using the navigator signal collected by this scan and measuring the displacement of the diaphragm. A detection method using such a magnetic resonance signal is disclosed in, for example, Wang et. al “Navigate-Echo-based Real-Time Respiratory Gating and Triggering for Reduction of Respiration Effects in Three-dimensional Coronary MR Angiography, 198”.

  As illustrated in FIG. 3, the execution unit 17a instructs the notification control unit 17f to repeatedly execute the above-described preparation scan while changing the repetition interval Trep. The data collected by the preparation scan is stored in the collected data storage unit 14b at every repetition interval.

  The preparation scan executed by the execution unit 17a has been described above. However, the execution unit 17a also executes the main scan based on the main scan sequence set by the sequence setting unit 17c described later. The main scan sequence set by the sequence setting unit 17c will be described in detail later.

  Returning to FIG. 2, the measurement unit 17 b is based on the data collected by the preparation scan, and is in a stationary period in which the movement amount due to breathing of the subject continues to be smaller than a predetermined amount at a plurality of repetition intervals. Measure the length.

  Specifically, when the execution scan is executed by the execution unit 17a, the measurement unit 17b reads the data collected by the preparation scan from the collected data storage unit 14b. Then, the measurement unit 17b uses the read data for each repetition interval, the time from the end of the breathing timing notification until the amount of movement of the subject due to breathing becomes smaller than a predetermined amount, and the breathing of the subject. The length of the stationary period in which the movement amount due to is continued to be smaller than the predetermined amount is measured.

  For example, in the example shown in FIG. 3, the measurement unit 17b determines that the amount of movement of the abdomen per unit time is within a predetermined range after the voice guide V2 ends based on the data collected by the monitor scan Navi. Time Tx until it falls within is measured. Furthermore, the measurement unit 17b determines that the amount of movement of the abdomen per unit time is within a predetermined range from the time when the voice guide V2 ends and the time Tx has elapsed based on the data collected by the monitor scan Navi. The period during which the current state continues is detected as a stationary period. And the measurement part 17b measures the length Ty of the detected stationary period.

  When the preparation scan is executed a plurality of times for one repetition interval by the execution unit 17a, the lengths of a plurality of still periods are measured for one repetition interval. In that case, for example, the measurement unit 17b may adopt the longest stationary period or the shortest stationary period for each repetition interval. Or the measurement part 17b may calculate the average value of the length of a stationary period for every repetition interval.

  Returning to FIG. 2, the sequence setting unit 17 c identifies the repetition interval in which the length of the stationary period measured by the measuring unit 17 b is the longest, and informs the subject of the breathing timing at the identified repetition interval. To set the sequence for the main scan to collect data for image generation. Note that the sequence setting unit 17c divides the k space into a plurality of regions, and when a sequence for collecting data for each divided region is executed in the main scan, the length of the stationary period corresponding to the specified repetition interval A sequence is set by deriving the k-space division number according to the above.

  Specifically, the sequence setting unit 17c uses the measurement unit 17b to measure the time Tx and the rest period until the movement amount due to breathing of the subject becomes smaller than a predetermined amount after the notification of the breathing timing is completed at each repetition interval. When the length Ty is measured, the repetition interval in which the length of the stationary period is the longest among the plurality of repetition intervals is specified. Then, the sequence setting unit 17c sets the sequence for the main scan by using the specified repetition interval and Tx and Ty corresponding to the repetition interval.

  FIG. 4 is a diagram showing an example of a sequence for the main scan set by the sequence setting unit 17c according to the present embodiment. FIG. 4 shows an example of a FFE (Fast Field Echo) 3D (Dimensional) -SSFP (Steady State Free Precession) sequence. In this sequence, the k space is divided into a plurality of regions. Data is collected every time.

  As shown in FIG. 4, for example, the sequence setting unit 17c sets a sequence for collecting data while notifying the voice guides V1 (“suck”) and V2 (“suck”) at a repetition interval Trep. At this time, the sequence setting unit 17c sets, as Trep, the repetition time specified as the one having the longest stationary period.

  Also, the sequence setting unit 17c notifies the voice guide V1 when the time Tv has elapsed from the start of the sequence, and then completes the notification of the voice guide V2 when the time Tvoice has elapsed. The notification timing is set. Tv and Tvoice are set in advance by the operator.

  Then, the sequence setting unit 17c sets the data collection timing so that data collection is performed during the time Tacq after the time Td has elapsed since the notification of the voice guide V2 has been completed. At this time, the sequence setting unit 17c sets the time Tx measured by the measurement unit 17b as Td, and sets the time Ty measured by the measurement unit 17b as Tacq. Note that the sequence setting unit 17c sets the sequence so that after the time Tacq has elapsed, the next voice guide V1 is notified when the time Trec determined in advance by the operator has elapsed.

  For example, as shown in FIG. 4, after applying an inversion pulse TAG for labeling, a monitor scan refProbe for detecting the movement of the subject is performed, and then a fat suppression pulse FatSat and a signal suppression pulse for artifact reduction After applying PreSat, data collection is performed by applying an excitation RF pulse at each of a plurality of repetition times TR after the time TI has elapsed. Note that the time TI from the application of TAG to the application of the first excitation pulse and the time Tref from the start of the monitor scan to the application of the first excitation pulse are respectively determined in advance by the operator. The imaging condition is set and stored in the imaging condition storage unit 14a.

  In this case, the sequence setting unit 17c sets the timing of the monitor scan refProbe and the data collection so that the monitor scan refProbe and the data collection are performed during the time Tacq. For example, the sequence setting unit 17c sets the sequence so that the monitor scan refProbe starts when the time Td elapses after the notification of the voice guide V2 is completed.

  Here, as described above, since Tref is set as an imaging condition, the length is fixed. For this reason, the time Tssfp from when the first excitation pulse is applied until data collection is performed for each TR varies depending on the length of Tacq. Since Tacq is set to the time Ty measured by the measurement unit 17b, it changes according to the result of the preparation scan.

  Therefore, the sequence setting unit 17c divides the k space into a plurality of regions as in the FFE3D-SSFP exemplified here, and when data is collected for each divided region, the sequence setting unit 17c sets the specified repetition interval Trep. The number of divisions of the k space is derived according to the corresponding length Tacq of the stationary period. For example, if the number of lines required for image generation is 256, the number of segments is set to 8 when data collection for 32 lines is possible during Tacq. In this case, the sequence shown in FIG. 4 is repeated eight times.

  As described above, when a sequence in which the sequence setting unit 17c collects data by dividing the k space into a plurality of regions is executed in the main scan, according to the length of the stationary period corresponding to the specified repetition interval. By deriving the k-space division number, it is possible to set an appropriate number of segments according to the subject.

  Returning to FIG. 2, the threshold setting unit 17 d sets a threshold for determining that the amount of movement of the subject is small based on the data collected by the preparation scan. For example, the threshold setting unit 17d sets the threshold by adding or subtracting a certain value to a predetermined amount used when the stationary period is detected by the measuring unit 17b.

  The detector 17e detects the amount of movement of the subject due to respiration during the main scan. Specifically, the detection unit 17e detects the amount of movement of the subject due to respiration based on data collected by the monitor scan executed during the main scan. For example, the detection unit 17e detects the amount of movement of the subject due to respiration based on the data collected by the monitor scan refProbe shown in FIG. 4 during the main scan. The method for detecting the amount of movement of the subject by the monitor scan performed in the main scan is the same as the method by the monitor scan performed in the preparation scan.

  The notification control unit 17f controls the notification of the breathing timing by the notification unit 18 based on the movement amount detected by the detection unit 17e during the main scan.

  Specifically, the notification control unit 17f determines the breathing timing when the movement amount detected by the detection unit 17e exceeds the threshold set by the threshold setting unit 17d for a predetermined number of times during the main scan. The notification unit 18 is controlled so that the notification is stopped and the notification of the breathing timing is restarted after being stopped a predetermined number of times.

  Further, the notification control unit 17f detects the actual respiration timing of the subject based on the movement amount detected by the detection unit 17e during the main scan, and changes the sound reproduction speed according to the detected respiration timing. Thus, the notification unit 18 is controlled.

  For example, the notification control unit 17f detects the breathing cycle of the subject based on the movement amount detected by the detection unit 17e during the main scan. Then, the notification control unit 17f instructs the notification unit 18 to instruct the voice when there is a deviation between the detected respiratory cycle length and the length of the respiration timing repetition interval notified during the main scan. Change the playback speed.

  As a specific example, the notification control unit 17f instructs the notification unit 18 to reduce the sound reproduction speed when the detected length of the respiratory cycle is shorter than the respiration interval. On the other hand, the notification control unit 17f instructs the notification unit 18 to increase the sound reproduction speed when the detected length of the respiratory cycle becomes longer than the respiration timing repetition interval.

  In this way, the notification control unit 17f can adjust the breathing interval of the subject to match the breathing timing notification interval by changing the playback speed of the voice that reports the breathing timing during the main scan. Become.

  Next, a description will be given of a processing procedure of respiratory synchronization imaging by the MRI apparatus 100 according to the present embodiment. FIG. 5 is a flowchart showing a processing procedure of respiratory synchronization imaging by the MRI apparatus 100 according to the present embodiment.

  As shown in FIG. 5, in the MRI apparatus 100, when the execution unit 17 a receives an instruction to start a preparation scan from the operator via the input unit 16 (Yes in step S <b> 101), breathing is performed on the subject at a predetermined repetition interval. A monitor scan is executed while notifying the timing (step S102). Further, the measurement unit 17b measures the length of a stationary period, which is a period in which the movement amount due to breathing of the subject is smaller than a predetermined amount, based on the data collected by the monitor scan (step S103).

  Subsequently, the execution unit 17a determines whether or not the monitor scan has been performed a predetermined number of times (step S104). If not, the execution unit 17a changes the repetition interval (step S104, No). (S105) The monitor scan is executed again (step S102). When the execution unit 17a performs the monitor scan a predetermined number of times (step S104, Yes), the measurement unit 17b determines the subject at a plurality of repetition intervals based on the data collected by the preparation scan. The length of a stationary period, which is a period in which the amount of movement due to breathing continues below a predetermined amount, is measured.

  Subsequently, the sequence setting unit 17c specifies a repetition interval in which the length of the stationary period measured by the measurement unit 17b is the longest (Step S106). Then, the sequence setting unit 17c sets a main scan sequence for collecting data for image generation in a stationary period while notifying the subject of the breathing timing at the specified repetition interval (step S107).

  Thereafter, when the execution unit 17a receives an instruction to start a main scan from the operator via the input unit 16 (Yes in step S108), the main scan is executed using the sequence set by the sequence setting unit 17c ( Step S109). When the execution unit 17a collects all data (step S110, Yes), the data processing unit 13 reconstructs an image from the collected data (step S111).

  As described above, the MRI apparatus 100 according to the present embodiment changes the repetition interval before the main scan and executes the preparation scan a plurality of times, so that the repetition interval in which the stationary period in which the movement of the subject is small becomes the longest is obtained. Specify the actual scan sequence. Therefore, according to the present embodiment, it is possible to appropriately set the interval for notifying the breathing timing according to the subject.

  In the above embodiment, an example has been described in which the notification control unit 17f controls the notification of the breathing timing using the threshold set by the threshold setting unit 17d. However, the movement amount due to respiration may change depending on the state of the subject, for example, when the subject has fallen asleep during the main imaging. Therefore, for example, the notification control unit 17f may change the threshold value based on the movement amount detected by the detection unit 17e during the main scan.

  For example, when the subject's breathing gradually becomes shallower or deeper, it is desirable to change the threshold accordingly. Therefore, for example, the notification control unit 17f increases the threshold value by a predetermined value when the movement amount when the subject exhales continuously increases over a predetermined number of cycles. On the other hand, the detection unit 17e decreases the threshold value by a predetermined value when the movement amount when the subject exhales continuously decreases over a predetermined number of cycles.

  In the above-described embodiment, the execution unit 17a has been described with respect to an example in which the preparation scan is executed a plurality of times at different repetition intervals. However, for example, the execution unit 17a not only changes the repetition interval, but also changes the interval between the voice guide V1 and the voice guide V2 and the reproduction speed of each of the voice guides V1 and V2, and executes the preparation scan a plurality of times. Also good. In that case, not only the repetition interval in which the length of the stationary period is the longest, but also the interval between the voice guide V1 and the voice guide V2 in which the length of the stationary period is the longest and / or the length of the stationary period is Based on the reproduction speeds of the longest voice guides V1 and V2, the sequence for the main scan is set.

  Moreover, in the said embodiment, the alerting | reporting part 18 demonstrated the example which alert | reports a respiratory timing with an audio | voice. However, for example, the notification unit 18 may notify the subject of breathing timing using information other than voice. For example, the notification unit 18 may output an image indicating the breathing timing to a monitor that can be viewed by the subject. As a specific example, for example, the notification unit 18 represents the timing of expiration and inspiration with a wavy curve, and dynamically outputs the curve to the monitor.

  In the above-described embodiment, the example in which the detection unit 17e detects the movement amount due to the respiration of the subject based on the data collected by the monitor scan executed during the main scan has been described. However, the detection unit 17e may detect the amount of movement of the subject due to respiration based on, for example, a respiration signal detected by a respiration sensor. The respiration sensor here detects, for example, movement due to respiration as air pressure, converts the detected air pressure into an electric signal, and outputs it as a respiration signal.

  According to the embodiment described above, it is possible to appropriately set the interval for notifying the breathing timing according to the subject.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

17a execution unit 17b measurement unit 17c sequence setting unit

Claims (5)

An execution unit that executes a preparation scan that collects data indicating the amount of movement of the subject due to respiration while notifying the subject at a predetermined repetition interval a plurality of times before the main scan while changing the repetition interval. When,
Based on the data collected by the preparation scan, a measurement unit that measures the length of a stationary period that is a period in which a movement amount due to breathing of the subject is smaller than a predetermined amount at a plurality of repetition intervals;
Specify the repetition interval for which the length of the stationary period is the longest, and set a sequence for main scan that collects data for image generation during the stationary period while notifying the subject of breathing timing at the identified repeating interval A magnetic resonance imaging apparatus comprising: a sequence setting unit configured to:   The sequence setting unit divides the k space into a plurality of regions, and when a sequence for collecting data for each divided region is executed in the main scan, according to the length of the stationary period corresponding to the specified repetition interval. The magnetic resonance imaging apparatus according to claim 1, wherein the sequence is set by deriving a division number of the k space. An informing unit for informing the subject of the respiration timing;
A detector that detects the amount of movement of the subject during respiration during the main scan;
The information control unit according to claim 1, further comprising: a notification control unit that controls notification of breathing timing by the notification unit based on a movement amount detected by the detection unit during a main scan. Magnetic resonance imaging device. A threshold setting unit configured to set a threshold for determining that the amount of movement of the subject is small based on data collected by the preparation scan;
When the movement detected by the detection unit exceeds the threshold value a predetermined number of times during the main scan, the notification control unit pauses the breathing timing and pauses the predetermined number of times. The magnetic resonance imaging apparatus according to claim 3, wherein the notification unit is controlled to restart notification of the breathing timing later. The notification unit notifies the breathing timing by voice,
The notification control unit detects an actual respiration timing of the subject based on a movement amount detected by the detection unit during a main scan, and changes the reproduction speed of the sound according to the detected respiration timing. The magnetic resonance imaging apparatus according to claim 3, wherein the notification unit is controlled as described above.

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