JP6945366B2 - Magnetic resonance imaging device - Google Patents

Description

Embodiments of the present invention relate to a magnetic resonance imaging apparatus.

The contrast of the reconstructed image in MR imaging is determined by the data in the central region of k-space. Data is collected for multiple frames in a time series using the Cartesian method, which collects data for each phase encoding step, or the Radial method, which collects data for each collection line set radially in k-space. In this case, the amount of collected data per frame is reduced to increase the time resolution. Therefore, if the time resolution is increased, the image quality per frame deteriorates.

U.S. Patent Application Publication No. 2015/0077112

The problem to be solved by the invention is to adjust the time resolution without reducing the amount of collected data.

The magnetic resonance imaging apparatus according to the present embodiment is a sequence control unit that executes a pulse sequence in which the collection order of k-space data is different among a plurality of frames in the time series and collects the k-space data related to the plurality of frames in the time series. And an image generation unit that generates a plurality of reconstructed images in a time series based on k-space data related to the plurality of frames.

FIG. 1 is a diagram showing a configuration of a magnetic resonance imaging apparatus according to the present embodiment. FIG. 2 is a diagram showing an example of a three-dimensional k-space related to dynamic imaging according to the present embodiment. FIG. 3 is a diagram schematically showing a transition of the central region collection timing by dynamic imaging using the center first method. FIG. 4 is a diagram schematically showing a transition of the central region acquisition timing in the dynamic boost imaging according to the present embodiment. FIG. 5 is a diagram showing a typical processing flow related to dynamic boost imaging performed under the system control function of the processing circuit according to the present embodiment. FIG. 6 is a diagram schematically showing a storage mode of k-space data by the storage circuit according to the present embodiment. FIG. 7 is a diagram schematically showing a transition of the central region collection timing in the dynamic imaging over a long period of time according to the present embodiment. FIG. 8 is a diagram showing a transition of the contrast phase in the liver contrast dynamic imaging according to the present embodiment. FIG. 9 is a diagram showing an example of a display screen of a user interface for instructing ON and OFF of the boost function, which is displayed by the display circuit according to the present embodiment. FIG. 10 is a diagram schematically showing a transition of the central region collection timing in the multi-slice imaging according to the present embodiment. FIG. 11 is a diagram schematically showing the transition of the central slice acquisition step in the dynamic boost imaging using the three-dimensional stack of stars method according to the present embodiment. FIG. 12 is a diagram schematically showing keyhole imaging according to the present embodiment. FIG. 13 is a diagram schematically showing applied thinning data collection according to the present embodiment.

Hereinafter, the magnetic resonance imaging apparatus according to the present embodiment will be described with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a magnetic resonance imaging device 1 according to the present embodiment. As shown in FIG. 1, the magnetic resonance imaging device 1 includes a gantry 11, a sleeper 13, a gradient magnetic field power supply 21, a transmission circuit 23, a reception circuit 25, a sleeper drive device 27, a sequence control circuit 29, and a host PC 50.

The gantry 11 has a static magnetic field magnet 41 and a gradient magnetic field coil 43. The static magnetic field magnet 41 and the gradient magnetic field coil 43 are housed in the housing of the gantry 11. A hollow bore is formed in the housing of the gantry 11. A transmission coil 45 and a reception coil 47 are arranged in the bore of the gantry 11.

The static magnetic field magnet 41 has a hollow substantially cylindrical shape, and generates a static magnetic field inside the substantially cylindrical shape. As the static magnetic field magnet 41, for example, a permanent magnet, a superconducting magnet, a normal conducting magnet, or the like is used. Here, the central axis of the static magnetic field magnet 41 is defined as the Z axis, the axis perpendicular to the Z axis is defined as the Y axis, and the axis horizontally orthogonal to the Z axis is defined as the X axis. The X-axis, Y-axis and Z-axis form a Cartesian three-dimensional coordinate system.

The gradient magnetic field coil 43 is a coil unit that is attached to the inside of the static magnetic field magnet 41 and is formed in a hollow substantially cylindrical shape. The gradient magnetic field coil 43 generates a gradient magnetic field by receiving a current supply from the gradient magnetic field power supply 21. More specifically, the gradient magnetic field coil 43 has three coils corresponding to the X-axis, Y-axis, and Z-axis that are orthogonal to each other. The three coils form a gradient magnetic field in which the magnetic field strength changes along each of the X-axis, Y-axis, and Z-axis. The gradient magnetic fields along the X-axis, Y-axis, and Z-axis are combined to form slice-selective gradient magnetic fields Gs, phase-encoded gradient magnetic fields Gp, and frequency-encoded gradient magnetic fields Gr that are orthogonal to each other in desired directions. The slice selection gradient magnetic field Gs is arbitrarily used to determine the imaging cross section. The phase-encoded gradient magnetic field Gp is used to change the phase of the MR signal according to the spatial position. The frequency-encoded gradient magnetic field Gr is used to change the frequency of the MR signal depending on the spatial position. In the following description, it is assumed that the inclination direction of the slice selection gradient magnetic field Gs is the Z axis, the inclination direction of the phase-encoded gradient magnetic field Gp is the Y-axis, and the inclination direction of the frequency-encoded gradient magnetic field Gr is the X-axis.

The gradient magnetic field power supply 21 supplies a current to the gradient magnetic field coil 43 according to the sequence control signal from the sequence control circuit 29. The gradient magnetic field power supply 21 supplies a current to the gradient magnetic field coil 43 to generate a gradient magnetic field along each of the X-axis, Y-axis, and Z-axis by the gradient magnetic field coil 43. The gradient magnetic field is superimposed on the static magnetic field formed by the static magnetic field magnet 41 and applied to the subject P.

The transmission coil 45 is arranged inside the gradient magnetic field coil 43, for example, and receives a current supply from the transmission circuit 23 to generate a high-frequency magnetic field pulse (hereinafter, referred to as an RF magnetic field pulse).

The transmission circuit 23 supplies a current to the transmission coil 45 in order to apply an RF magnetic field pulse for exciting the target proton existing in the subject P to the subject P via the transmission coil 45. The RF magnetic field pulse oscillates at a resonance frequency specific to the target proton to excite the target proton. A magnetic resonance signal (hereinafter referred to as MR signal) is generated from the excited target proton and detected by the receiving coil 47. The transmission coil 45 is, for example, a whole body coil (WB coil). The whole body coil may be used as a transmission / reception coil.

The receiving coil 47 receives the MR signal emitted from the target proton existing in the subject P under the action of the RF magnetic field pulse. The receiving coil 47 has a plurality of receiving coil elements capable of receiving MR signals. The received MR signal is supplied to the receiving circuit 25 via wire or wireless. Although not shown in FIG. 1, the receiving coil 47 has a plurality of receiving channels mounted in parallel. The receiving channel includes a receiving coil element that receives the MR signal, an amplifier that amplifies the MR signal, and the like. The MR signal is output for each reception channel. The total number of receiving channels and the total number of receiving coil elements may be the same, and the total number of receiving channels may be larger or smaller than the total number of receiving coil elements.

The receiving circuit 25 receives the MR signal generated from the excited target proton via the receiving coil 47. The receiving circuit 25 processes the received MR signal to generate a digital MR signal. The digital MR signal can be expressed in k-space defined by the spatial frequency. Therefore, hereinafter, the digital MR signal will be referred to as k-space data. The k-space data is supplied to the host PC 50 via wire or wireless.

The transmission coil 45 and the reception coil 47 are merely examples. Instead of the transmitting coil 45 and the receiving coil 47, a transmitting / receiving coil having a transmitting function and a receiving function may be used. Further, the transmission coil 45, the reception coil 47, and the transmission / reception coil may be combined.

A sleeper 13 is installed adjacent to the gantry 11. The sleeper 13 has a top plate 131 and a base 133. The subject P is placed on the top plate 131. The base 133 slidably supports the top plate 131 along each of the X-axis, Y-axis, and Z-axis. The sleeper drive device 27 is housed in the base 133. The sleeper drive device 27 moves the top plate 131 under the control of the sequence control circuit 29. The sleeper drive device 27 may include, for example, any motor such as a servo motor or a stepping motor.

The sequence control circuit 29 has a processor of a CPU (Central Processing Unit) or an MPU (Micro Processing Unit) and a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory) as hardware resources. The sequence control circuit 29 synchronously controls the gradient magnetic field power supply 21, the transmission circuit 23, and the reception circuit 25 based on the pulse sequence information supplied from the host PC 50 via the communication IF61, and the pulse corresponding to the pulse sequence information. The sequence is executed to take an MR image of the subject P, and k-space data regarding the subject P is collected.

As shown in FIG. 1, the host PC 50 is a computer device having a processing circuit 51, a storage circuit 53, a display circuit 55, an input circuit 57, a network IF 59, and a communication IF 61.

The processing circuit 51 has a processor such as a CPU, GPU (Graphics Processing Unit), or MPU, and a memory such as a ROM or RAM as hardware resources. The processing circuit 51 has a reconstruction function 511, an image processing function 513, a pulse sequence generation function 515, and a system control function 517 by executing various programs. An application specific integrated circuit (ASIC) or a field programmable gate array that realizes a reconstruction function 511, an image processing function 513, a pulse sequence generation function 515, and a system control function 517. : FPGA), other complex programmable logic device (CPLD), simple programmable logic device (Simple Programmable Logic Device: SPLD) may be realized. The reconstruction function 511, the image processing function 513, the pulse sequence generation function 515, and the system control function 517 may be mounted on a single substrate or may be distributed on a plurality of substrates.

In the reconstruction function 511, the processing circuit 51 executes a reconstruction process on the k-space data to generate a reconstruction image. Specifically, FFT (Fast Fourier Transfer) or the like is used as the reconstruction process.

In the image processing function 513, the processing circuit 51 performs various image processing on the reconstructed image. For example, the processing circuit 51 performs image processing such as volume rendering, surface rendering, pixel value projection processing, MPR (Multi-Planer Reconstruction) processing, and CPR (Curved MPR) processing.

In the pulse sequence generation function 515, the processing circuit 51 generates pulse sequence information based on various imaging parameters and the like. The generated pulse sequence information is supplied to the sequence control circuit 29, and a pulse sequence based on the pulse sequence information is executed. Further, the pulse sequence information is stored in the storage circuit 53.

In the system control function 517, the processing circuit 51 controls the entire magnetic resonance imaging device 1 according to the present embodiment. For example, the processing circuit 51 controls each unit according to the control program stored in the storage circuit 53 to execute MR imaging according to the present embodiment.

The storage circuit 53 is a storage device such as an HDD (Hard Disk Drive), an SSD (Solid State Drive), or an integrated circuit storage device that stores various information. Further, the storage circuit 53 may be a drive device or the like that reads and writes various information to and from a portable storage medium such as a CD-ROM drive, a DVD drive, and a flash memory. For example, the storage circuit 53 stores various programs such as k-space data and control programs.

The display circuit 55 displays various information. For example, the display circuit 55 displays a reconstructed image generated by the reconstructing function 511, an image processed by the image processing function 513, and the like. The display circuit 55 has a display interface and a display device. The display interface converts data representing a display target into a video signal. The video signal is supplied to the display device. The display device displays a video signal representing a display target. As the display device, for example, a CRT display, a liquid crystal display, an organic EL display, an LED display, a plasma display, or any other display known in the art can be appropriately used.

Specifically, the input circuit 57 has an input device and an input interface. The input device receives various commands from the user. As input devices, keyboards, mice, various switches, touch screens, touch pads, etc. can be used. The input interface supplies the output signal from the input device to the processing circuit 51 via the bus. The input circuit 57 is not limited to the one provided with physical operating parts such as a mouse and a keyboard. For example, an electric signal processing circuit that receives an electric signal corresponding to an input operation from an external input device provided separately from the magnetic resonance imaging device 1 and outputs the received electric signal to various circuits is also input. Included in the circuit example.

The network IF59 connects the magnetic resonance imaging device 1 to a workstation, PACS (Picture Archiving and Communication System), HIS (Hospital Information System), RIS (Radiology Information System), etc. via a LAN (Local Area Network) or the like. Interface. The network IF sends and receives various information to and from the workstation, PACS, HIS, and RIS to which it is connected.

The communication IF61 is an interface for connecting the sequence control circuit 29 and the reception circuit 25 to the host PC 50 via wire or wireless. For example, the communication IF61 transmits pulse sequence information to the sequence control circuit 29. Further, the communication IF61 receives k-space data from the receiving circuit 25.

The above configuration is an example, and the present invention is not limited to this. For example, the sequence control circuit 29 may be incorporated in the host PC 50. Further, the sequence control circuit 29 and the processing circuit 51 may be mounted on the same board. The sequence control circuit 29, the gradient magnetic field power supply 21, the transmission circuit 23, and the reception circuit 25 may be mounted in a single control device different from the host PC 50, or may be mounted in a plurality of devices in a distributed manner.

Hereinafter, an operation example of the magnetic resonance imaging apparatus 1 according to the present embodiment will be described. The MR imaging according to the present embodiment is intended for dynamic imaging in which a slice in a two-dimensional space or a volume in a three-dimensional space is MR-imaged in a time series to collect k-space data related to a plurality of frames in the time series. It is assumed that the k-space filling method according to the present embodiment is the Cartesian method. However, the k-space filling method according to the present embodiment is not limited to this, and may be a radial method, a spiral method, or any other method.

In the case of two-dimensional imaging, the k space is defined as an orthogonal two-dimensional space of the spatial frequency ky corresponding to the phase encoding by the phase-encoded gradient magnetic field Gp and the spatial frequency kx corresponding to the frequency encoding by the frequency-encoded gradient magnetic field Gr. In the case of three-dimensional imaging, the k space is defined as a three-dimensional space orthogonal to the space axis ky, the space axis kx, and the space axis kz corresponding to slice encoding by the slice selection gradient magnetic field Gs. The frame according to the present embodiment refers to a set of k-space data required to generate one reconstructed image. Hereinafter, for the sake of specific description, it is assumed that the MR imaging according to the present embodiment is a three-dimensional imaging targeting a volume. Further, it is assumed that the k-space filling method related to the three-dimensional MR imaging according to the present embodiment is a Cartesian method in which data is collected for each combination of the phase encoding step and the slice encoding step.

FIG. 2 is a diagram showing an example of a three-dimensional k-space according to the present embodiment. As shown in FIG. 2, the three-dimensional k-space is defined by the kx axis, the ky axis, and the kz axis. The sampling points of k-space data are divided into a plurality of k-space subregions. The plurality of k-space subregions are divided into a cylindrical central region RC and an edge region RE having the origin PO (ky = kz = 0) of the ky−kz plane on a common central axis. The central region RC is a local k-space subregion including the origin PO of the k-space. The central region RC is dominant over the contrast of the entire reconstructed image. For example, the central region RC is set to a region that affects approximately 90% of the contrast of the reconstructed image. The marginal region RE is a k-space partial region other than the central region RC of the k-space. The edge region RE is dominant with respect to the edge portion of the reconstructed image. For example, the marginal region RC is set to a region that affects the remaining approximately 10% of the contrast of the reconstructed image. The edge region RE is further divided into a plurality of edge portion regions REn. Here, n is a natural number indicating the number of marginal regions. In FIG. 2, the marginal region RE is divided into three marginal region regions RE1, RE2, and RE3, but the number of marginal region regions REn is not limited to three, and may be any number as long as it is one or more.

As described above, since the central region RC is dominant with respect to the contrast of the entire reconstructed image, the time for giving the contrast of the reconstructed image in MR imaging is, for example, one sampling in the central region RC in k-space. It can be associated with the time when k-space data of a point or a plurality of predetermined sampling points is collected (hereinafter, referred to as a data collection time). When associating a plurality of sampling points with the time at which they were collected, for example, they are associated with their average time. The data collection time of the k-space subregion may be defined as the time at which the k-space data of any sampling point among the plurality of sampling points constituting the k-space subregion is collected. More specifically, the data collection time may be defined as the time at which k-spatial data relating to sampling points in arbitrary order such as first, middle, or last in time is collected, or may be positioned at the center, end, or the like. It may be specified at the time when the k-space data related to the sampling point at an arbitrary position is collected, or may be specified at the data collection time of any other sampling point. For example, the data collection time of the central region RC is defined as the time at which the origin PO of the ky-kz plane, that is, the k-space data relating to ky = kz = 0 is collected. Hereinafter, the order of collecting k-space data related to the k-space subregion in each frame will be referred to as a collection timing, and in particular, the order of collecting k-space data relating to the central region RC will be referred to as a central region collection timing.

The central region collection timing is usually fixed between a plurality of frames in the time series. In the case of FIG. 2, the k-space is divided into four regions, the central region RC, the marginal region RE1, the marginal region RE2, and the marginal region RE3. The collection timing is usually fixed at a predetermined order. In each frame, the collection order in which the k-space data related to the central region RC is collected last is the center-Last, and the collection order in which the k-space data related to the central region RC is collected first is the book. In the embodiment, it will be referred to as Center-First.

FIG. 3 is a diagram schematically showing the transition of the central region collection timing TC by dynamic imaging using the center first method. As shown in FIG. 3, k-space data relating to a plurality of frame FRs in a time series is collected by dynamic imaging. In the center-first method, k-space data regarding the central region is collected at the beginning of each frame FR. Here, the time interval TIC between the temporally adjacent central region collection timing TCs is referred to as a contrast time resolution, and the time interval TIF between the temporally adjacent frame center time TFCs is referred to as a frame time resolution. The frame center time TFC indicates the center time in the data collection period of each frame FR. When the central region collection timing TC in each frame FR is the same over a plurality of frame FRs as in the center-first method, the contrast time resolution and the frame time resolution are the same. For example, in the center-first method, when the imaging time of 4 frames is 14 seconds, the frame time resolution and the contrast time resolution are the same 3.5 seconds / frame.

The sequence control circuit 29 according to the present embodiment executes a pulse sequence in which the collection order of k-space data is different between a plurality of frames in a time series. As a result, the contrast time resolution can be intentionally made earlier or later than the frame time resolution without reducing the amount of k-space data collected, and the contrast time resolution can be freely adjusted. Hereinafter, dynamic imaging that accelerates the contrast time resolution will be referred to as dynamic boost imaging.

FIG. 4 is a diagram schematically showing a transition of the central region acquisition timing TC in the dynamic boost imaging according to the present embodiment. As shown in FIG. 4, the sequence control circuit 29 synchronously controls the gradient magnetic field power supply 21, the transmission circuit 23, and the reception circuit 25 to execute dynamic boost imaging, and k-space data regarding a plurality of frame FRs in a time series. To collect. In the dynamic boost imaging, the sequence control circuit 29 advances the central region acquisition timing SC stepwise without changing the amount of acquired data between the plurality of frame FRs in the time series. For example, as shown in FIG. 4, the time interval in which the dynamic boost imaging is performed is 4 frames. Further, it is assumed that the k-space is divided into four regions, a central region RC, an edge portion region RE1, a margin portion region RE2, and a margin portion region RE3, as shown in FIG. In this case, the central area collection timing TC of the first (first) frame FR1 is the fourth, the central area collection timing TC of the second frame FR2 is the third, and the central area collection timing TC of the third frame FR3 is the second. , The central region collection timing TC of the fourth (last) frame FR4 is set to the first. At this time, in all frames FR1, FR2, FR3 and FR4, data is collected for all four regions of the central region RC, the marginal region RE1, the marginal region RE2 and the marginal region RE3. By gradually advancing the central region collection timing SC while collecting k-space data for the entire k-space subregion between the plurality of frame FRs in this way, the contrast time resolution without reducing the amount of k-space data collected. Can be shorter than the frame time resolution.

As shown in FIG. 4, when the imaging time of 4 frames is 14 seconds, the frame time resolution is 3.5 seconds / frame, whereas the contrast time resolution is about 2.5 seconds / frame. By performing dynamic boost imaging in this way, it is possible to image moving objects such as blood flow and heart with high time resolution, so it is possible to reduce motion-induced artifacts included in time-series reconstructed images. Can be done.

Hereinafter, an operation example of the magnetic resonance imaging apparatus 1 relating to the dynamic boost imaging according to the present embodiment will be described. In the following description of the operation example, it is assumed that the pulse sequence is a three-dimensional Cartesian method.

FIG. 5 is a diagram showing a typical processing flow related to dynamic boost imaging performed under the system control function 517 of the processing circuit 51. As shown in FIG. 5, the processing circuit 51 first executes the pulse sequence generation function 515 (steps S1 and S2).

In the pulse sequence generation function 515, the processing circuit 51 first sets a time interval (hereinafter, referred to as a boost interval) for performing dynamic boost imaging (step S1). For example, the processing circuit 51 accepts the user to specify the boost section via the input circuit 57. The boost section may be specified by a time length such as 14 seconds (hereinafter referred to as a boost time), a number of frames such as 4 frames, or 24 seconds from 10 seconds after the start of imaging. It may be specified by a period such as until later, or from 9:10:00 to 9:10:14, or may be specified in other embodiments. When the value of the boost section is specified via the input circuit 57, the processing circuit 51 sets the specified value in the boost section. The processing circuit 51 may automatically determine the boost section according to the imaging site, contrast conditions, and the like. Further, the boost section may be predetermined.

When step S1 is performed, the processing circuit 51 generates pulse sequence information that realizes the contrast time resolution corresponding to the boost section set in step S1 (step S2). The pulse sequence according to the present embodiment can be applied to both a gradient echo (GRE) sequence and a spin echo (SE: Spin Echo) sequence. Further, a preparation pulse such as an inversion recovery (IR) pulse or a fat saturation pulse may be inserted into any pulse sequence. Further, as a k-space filling method, not only a method of filling for each phase encoding but also an echo planar (EPI: Echo Planar Imaging) may be used.

In step S2, the processing circuit 51 determines, for example, the collection order of k-space data in each frame based on the number of frames in the boost section and the number of k-space subregions. Specifically, the processing circuit 51 is used for each of the plurality of frames of the time series belonging to the boost section so that the central region collection timing of the central region is stepwise advanced among the plurality of frames of the time series belonging to the boost section. Determine the collection timing of the k-space subregion of. Hereinafter, the process of step S2 will be described in detail.

Specifically, first, the processing circuit 51 determines the central region collection timing for a plurality of time-series frames belonging to the boost section. More specifically, the central region collection timing of each frame is determined so that the central region collection timing is positioned forward in time as the frame collection time (time phase) is later in time. For example, when the number of frames is 4 and the k-space subregion is 4, the central region collection timing is the 4th in the first frame and the 3rd in the second frame, as shown in FIG. , The third frame is set to the second, and the fourth frame is set to the first.

Next, the processing circuit 51 determines the collection timing of each edge portion region for each frame. The collection timing of each marginal region may be determined according to an arbitrary rule. For example, each k-space portion of each frame so that the collection timing of each of the central region, the first rim region, the second rim region, and the third rim region circulates over a plurality of frames. It suffices if the collection timing of the area is determined. By determining the collection timing of each k-space subregion in this way, the processing circuit 51 sets the collection order of the k-space data of each frame so that the center collection timing is stepwise advanced over a plurality of frames in the time series. It will be possible to decide.

In the above example, it is assumed that the central region collection timing is determined with the k-space subregion as one unit. However, this embodiment is not limited to this. In the processing circuit 51, the central region collection timing may be determined for each encoding step (collection line). In this case, the processing circuit 51 determines the collection order of k-space data in each frame based on the number of frames and the number of encoding steps (the number of slice encoding steps and the number of phase encoding steps).

The center area collection timing of each frame is the value obtained by dividing the difference between the center area collection timing of the first frame and the center area collection timing of the last frame by the number of frames, and is ahead in time from the first frame to the last frame. Is shifted to. The timing of collecting the central region of the first frame is not particularly limited, but it is possible to increase the contrast resolution as the time goes back. For example, when the number of frames is 4, the number of slice encoding steps is 256, and the number of phase encoding steps is 512, there are 256 × 512 = 131072 steps. Assuming that the central area collection timing of the first frame is 131072nd and the central area collection timing of the last frame is the first, for example, in the second frame, the central area collection timing is 87381th and the third. In the frame, the central region collection timing is set to 43690th.

Encoding steps other than the central region collection timing can be set in any order (number). For example, it is preferable that the order of the encoding steps is set so that the collecting timing of the encoding steps whose spatial frequency is closer to the origin is closer to the central region collecting timing. Since the encoding step in which either one of kz and ky is 0 and the other is non-zero contributes relatively large to the contrast of the reconstructed image, it is preferable to set them in an order close to the central region collection timing. By determining the order of each encoding step in this way, it is possible to set the central area collection timing of each frame so that the central area collection timing is stepwise advanced over a plurality of time-series frames.

A method of determining the central region collection timing in units of k-space subregions and a method of determining the central region collection timing in units of encoding steps may be combined. For example, the processing circuit 51 may first determine the collection timing of the k-space subregion of each frame, and then determine the order of the encoding steps for filling each k-space subregion.

As described above, the preparation pulse may be incorporated in the pulse sequence of the dynamic boost imaging. In order to obtain the effect of the preparation pulse, it is necessary to collect k-space data regarding the central region after a lapse of a predetermined time from the application of the preparation pulse. The processing circuit 51 determines the collection order of k-space data for each frame within this constraint.

For example, the collection order considering the preparation pulse constraint is determined as follows. First, as described above, the processing circuit 51 determines the central region acquisition timing (referred to as the ideal central region acquisition timing) without restriction by the preparation pulse based on the number of frames in the boost section and the number of encoding steps.

Next, the processing circuit 51 sets the application time of a plurality of preparation pulses in the pulse sequence of each frame according to a predetermined rule. The processing circuit 51 sets a predetermined time frame after a predetermined time has elapsed from the application time of each preparation pulse. In order to enhance the effect of the preparation pulse, it is necessary to set the central region collection timing within the time frame corresponding to any of the preparation pulses. The processing circuit 51 determines whether or not the ideal central region collection timing is included in any one of the set time frames. When the ideal central region collection timing is included in the time frame, the processing circuit 51 sets the ideal central region collection timing as the final central region collection timing. When the ideal central region collection timing is not included in any one of the plurality of time frames, the processing circuit 51 finalizes an arbitrary position in the time frame closest to the ideal central region collection timing. Set to the central area collection timing. In other words, the processing circuit 51 limits the central region collection timing within a predetermined time frame after a predetermined time has elapsed from the application time of the preparation pulse, and gradually sets the central region collection timing among a plurality of time-series frames. Shift forward.

When the final central region collection timing is set, the processing circuit 51 sets the collection timing of another k-space partial region in the pulse sequence of each frame. In this way, the collection order of k-space data for each frame is determined. As a result, it is possible to generate a pulse sequence in which the contrast time resolution is enhanced while maintaining the effect of the preparation pulse.

When step S2 is performed, the processing circuit 51 causes the sequence control circuit 29 to perform dynamic boost imaging (step S3). In step S3, the sequence control circuit 29 synchronously controls the gradient magnetic field power supply 21, the transmission circuit 23, and the reception circuit 25 based on the pulse sequence information generated in step S2, and performs dynamic boost imaging by the pulse sequence. .. The receiving circuit 25 collects k-space data related to a plurality of time-series frames by dynamic boost imaging. The k-space data is stored in the storage circuit 53 for each frame.

FIG. 6 is a diagram schematically showing a storage mode of k-space data by the storage circuit 53. As shown in FIG. 6, the storage circuit 53 stores the k-space data, the central region collection timing, and the central region collection time in association with each of the plurality of frames in the time series. The central area collection timing is defined by, for example, the number of the encoding step corresponding to the central area collection timing. As the central region collection time, for example, a DICOM (Digital Imaging and Communications in Medicine) time stamp used by the sequence control circuit 29 is used. The sequence control circuit 29 uses, for example, a DICOM time stamp when an encode pulse corresponding to the central region collection timing is applied or a DICOM time stamp when an MR signal corresponding to the central region collection timing is received at the central region collection timing. Record as a time stamp of. The recorded time stamp is transmitted to the receiving circuit 25 together with the corresponding central region collection timing and frame number. The reception circuit 25 transmits the transmitted central region collection timing, time stamp, and frame number to the storage circuit 53 in association with k-space data based on the received MR signal. The storage circuit 53 stores the central region collection timing, the time stamp, and the frame number in association with the k-space data transmitted from the reception circuit 25. For example, the display circuit 55 can display the central region collection timing and the central region collection time for each frame according to the display instruction from the user via the input circuit 57.

When step S3 is performed, the processing circuit 51 executes the reconstruction function 511 (step S4). In the reconstruction function 511, the processing circuit 51 generates a plurality of time-series reconstructed images based on k-space data related to the plurality of time-series frames collected in step S3. The storage circuit 53 stores the reconstructed image of each frame in association with the order of the central region collection timing of the frame and the central region collection time.

When step S4 is performed, the processing circuit 51 displays a plurality of time-series reconstructed images generated in step S4 on the display circuit 55 (step S5). The display circuit 55 may display a plurality of time-series reconstructed images in order as moving images, or may display them side by side as still images. Further, for example, the display circuit 55 may display the order of the central region collection timing and the central region collection time for the frame together with the reconstructed image for each frame according to the display instruction from the user via the input circuit 57. ..

This completes the typical process related to dynamic boost imaging.

In the dynamic boost imaging according to the present embodiment, the contrast time resolution is improved by gradually shifting the central region acquisition timing between a plurality of frames. Therefore, when the boost section extends for a long time, the number of frames increases as the boost section becomes longer, so that the degree of improvement in the contrast time resolution weakens. Therefore, when the MR imaging time is long, the boost section may be set only in a part of the time section.

FIG. 7 is a diagram schematically showing a transition of the central region collection timing in the dynamic imaging over a long period of time according to the present embodiment. As shown in FIG. 7, in the pulse sequence generation function 515, the processing circuit 51, for example, according to a user's instruction via the input circuit 57 or automatically, has a boost section and a first fixed section preceding the boost section. And a second fixed section following the boost section are set. The first and second fixed intervals are time intervals in which the collection order of k-space data is fixed among a plurality of frames. The collection order of the k-space between the first fixed section and the second fixed section can be arbitrarily set. For example, since the central region collection timing smoothly shifts from the first fixed section to the second fixed section via the boost section, the center last method is set in the first fixed section and the second fixed section is set. The center first method is set in the section, and the center shift method is set in the boost section. In the center shift method, as described above, the central region collection timing is gradually shifted from the final step to the start step at equal intervals.

The start timing of the boost section may be predetermined. For example, the imaging time of each of the first fixed section, the boost section, and the second fixed section may be predetermined by the pulse sequence generation function 515 of the processing circuit 51. The imaging time of each of the first fixed section, the boost section, and the second fixed section can be set to an arbitrary value according to an instruction by the user via the input circuit 57.

The display circuit 55 may display a user interface instructing ON and OFF of the boost function. Hereinafter, MR contrast imaging using the user interface will be described with reference to clinical examples of liver contrast dynamic imaging. The boost function refers to a function of stepwisely advancing the central region collection timing between a plurality of frames in the boost section as described above.

FIG. 8 is a diagram showing the transition of the contrast phase in the liver contrast dynamic imaging. As shown in FIG. 8, in the liver contrast dynamic imaging, a contrast agent is injected to image the liver exhibiting a lesion such as cancer cells. The contrast medium is not particularly limited, and for example, an extracellular fluid contrast medium containing gadolinium and a chelating agent is used. As the chelating agent for the extracellular fluid contrast agent, DTPA (diethylenetriamine pentaacetic acid) for chelating gadolinium or the like is used. Further, the contrast medium is not limited to the extracellular fluid contrast medium, and for example, a liver-specific contrast medium may be used. The liver-specific contrast medium is a contrast medium containing gadolinium, DTPA, and EOB (ethoxybenzyl), which is excellent in uptake into hepatocytes.

The contrast phase according to the present embodiment is a time phase in which the time after the contrast agent is injected into the subject P is shown in association with the human body part where the contrast contrast due to the contrast agent flowing in the subject P is remarkable. be. For example, when a contrast medium is injected from a vein, the contrast medium transitions in order from the injection of the contrast medium to the arterial dominant phase, the portal vein dominant phase, the equilibrium phase, and the hepatocyte phase after waiting for a delay time. In the present embodiment, the boost section is set in all or a part of the period between the arterial dominant phase and the portal vein dominant phase in which the rapid inflow of the contrast medium occurs.

FIG. 9 is a diagram showing an example of a display screen I1 of a user interface for instructing ON and OFF of the boost function, which is displayed by the display circuit 55 according to the present embodiment. The display screen I1 is displayed by the display circuit 55, for example, during a period in which dynamic imaging is being executed by the sequence control circuit 29. As shown in FIG. 9, the display screen I1 includes a contrast medium injection elapsed time display column R1, a boost time display column R2, a boost ON button R3, and a boost OFF button R4. In the display column R1, the elapsed time from the contrast medium injection start time is displayed by the display circuit 55. In the display field R2, the preset boost time is displayed by the display circuit 55. The boost ON button R3 is a button for instructing the start of the boost function. The boost OFF button R4 is a button for instructing the forced termination of the boost function when the boost function is executed.

For example, the sequence control circuit 29 executes dynamic imaging in which the collection order of k-space data is fixed, triggered by the elapse of a delay time from the start of injection of the contrast medium. The user listens to the start timing of the boost function while observing the time-series reconstructed image obtained by the dynamic imaging and the elapsed time of the contrast medium injection displayed in the display column R1. When the boost ON button is pressed by a user or the like, the sequence control circuit 29 synchronously controls the gradient magnetic field power supply 21, the transmission circuit 23, and the reception circuit 25, and performs dynamic boost imaging over the boost time. The time-series reconstructed image obtained by the dynamic boost imaging is displayed by the display circuit 55. In this way, for example, by setting the boost time in the time interval in which the rapid inflow of the contrast medium occurs, the flow of the contrast medium can be observed with the contrast time resolution.

When the boost time elapses, the sequence control circuit 29 synchronously controls the gradient magnetic field power supply 21, the transmission circuit 23, and the reception circuit 25 to end the dynamic boost imaging. After the dynamic boost imaging is completed, the sequence control circuit 29 synchronously controls the gradient magnetic field power supply 21, the transmitting circuit 23, and the receiving circuit 25, and executes dynamic imaging in which the collection order of k-space data is fixed. The time-series reconstructed image obtained by the dynamic imaging is also displayed by the display circuit 55.

When the boost OFF button R4 is pressed by a user or the like during execution of dynamic boost imaging, the sequence control circuit 29 synchronously controls the gradient magnetic field power supply 21, the transmission circuit 23, and the reception circuit 25, and terminates the boost function. , K Performs dynamic imaging with a fixed collection order of spatial data. At this time, the sequence control circuit 29 may end the MR imaging without executing the dynamic imaging after the boost function is terminated.

In the above description, dynamic imaging is defined as volume imaging for a volume composed of a plurality of voxels arranged in a three-dimensional manner. However, this embodiment is not limited to this. For example, the dynamic boost imaging according to the present embodiment may be a multi-slice imaging targeting a volume composed of a plurality of slices.

FIG. 10 is a diagram schematically showing a transition of the central region collection timing in the multi-slice imaging according to the present embodiment. FIG. 10A is a diagram showing multi-slices in k-space. FIG. 10B is a diagram schematically showing the central region collection timing in each frame. As shown in FIG. 10, in the pulse sequence generation function 515, the processing circuit 51 has a central region for all slices of each frame so that the central region collection timing shifts forward in time as the frame is later in time. Set the collection timing. Such multi-slice imaging can be used, for example, for contrast-enhanced multi-slice imaging of the heart.

Specifically, the processing circuit 51 determines the collection order between the plurality of k-space subregions and the collection order between the plurality of slices for each frame. For example, the collection order between a plurality of k-space subregions for each frame is set so that the central region collection timing shifts from the center last to the center last for the central region, and circulates for the plurality of marginal subregions. It is good to set it as a target. The collection order between the plurality of slices may be fixed over a plurality of frames or may be arbitrarily changed. Next, the processing circuit 51 collects data in the k-space subregion of the first collection order for all slices in the specified collection order, and collects the k-space subregion of the second collection order for all slices in the specified collection order. Data is collected in the k-space subregion of the third collection order for all slices in the specified collection order, and the k-space subregion of the fourth collection order is data for all slices in the specified collection order. The k-space subregion collection order is determined for all slices of all frames so that they are collected. The determined pulse sequence information is stored in the storage circuit 53.

For example, the k-space partial region is the central region (abbreviated as "center"), the first marginal region (abbreviated as "edge 1"), and the second marginal region (abbreviated as "edge 2"). It is divided into a third edge portion region (abbreviated as "edge 3"), and the volume is composed of five slices. It is assumed that the collection order between the plurality of slices is fixed over a plurality of frames, and the first slice, the second slice, the third slice, the fourth slice, and the fifth slice are collected in this order. In this case, for frame 1, edge 3 (1st to 5th slices) → edge 2 (1st to 5th slices) → edge 1 (1st to 5th slices) → center (third) Data is collected in the order of 1 slice to 5th slice). For frame 2, edge 2 (1st slice to 5th slice) → edge 1 (1st slice to 5th slice) → center (1st slice to 5th slice) → edge 3 (from 1st slice) Data is collected in the order of (fifth slice). For frame 3, edge 1 (1st to 5th slices) → center (1st to 5th slices) → edge 3 (1st to 5th slices) → edge 2 (from 1st slice) Data is collected in the order of (fifth slice). For frame 4, center (1st to 5th slices) → edge 3 (1st to 5th slices) → edge 2 (1st to 5th slices) → edge 1 (from 1st slice) Data is collected in the order of (fifth slice).

The sequence control circuit 29 synchronously controls the gradient magnetic field power supply 21, the transmission circuit 23, and the reception circuit 25 according to the set pulse sequence information, so that the contrast time resolution is improved as compared with the frame time resolution. Becomes possible to execute. Specifically, the sequence control circuit 29 executes data acquisition for all slices of each frame so that the central region collection timing shifts forward in time as the frame is later in time.

In the above description, the processing circuit 51 sets the central region collection timing for all slices of each frame so that the central region collection timing shifts forward in time as the frame is later in time. However, this embodiment is not limited to this. That is, the processing circuit 51 can also set the central region collection timing for all slices of each frame so that the central region collection timing shifts backward in time as the frame is later in time. As a result, the contrast time resolution can be intentionally reduced even in multi-slice dynamic imaging.

In the above description, the Cartesian method is used for the dynamic boost imaging. However, this embodiment is not limited to this. For example, the dynamic boost imaging according to the present embodiment may be a three-dimensional Stack-of-Stars method in which the Cartesian method and the radial method are used in combination. In the 3D stack of stars method, slice encoding is performed in the same way as in the Cartesian method for the slice direction, and for slices defined by the phase direction and frequency direction, radial collection lines (spokes) are used in the same way as in the radial method. Combine phase encoding and frequency encoding to collect data along the way. The sequence control circuit 29 according to the present embodiment executes a pulse sequence of the three-dimensional stack of stars method so that the collection timing of the central slice differs between a plurality of frames in the time series.

FIG. 11 is a diagram schematically showing a transition of the acquisition timing of the central slice in the dynamic boost imaging using the three-dimensional stack of stars method according to the present embodiment. In FIG. 11, one frame is assumed to be a k-space data set of a volume VO composed of five slices SL1, SL2, SL3, SL4 and SL5. The numbers assigned to each slice SL1, SL2, SL3, SL4 and SL5 indicate the slice encoding step numbers of each slice SL1, SL2, SL3, SL4 and SL5. As shown in FIG. 11, the slice encoding step number of the central slice SL3 changes stepwise from 5 to 1, that is, the slice encoding step number of the central slice SL3 is time-advanced between the plurality of frames. As a result, the contrast resolution in the slice direction is improved as compared with the frame resolution.

In addition, other imaging techniques may be used in combination with the boost section to further improve the time resolution. For example, the sequence control circuit 29 may collect thinned data in the boost section. Thinning data collection is a technique for collecting data only for some sampling points, instead of collecting data for all sampling points in k-space. As the thinning data collection method according to the present embodiment, a view-sharing method, a parallel imaging method, a partial Fourier method, and a compressed sensing method can be applied. The sequence control circuit 29 executes data acquisition so as to increase the acceleration rate of the view sharing method, the parallel imaging method, the partial Fourier method, and the compressed sensing method in the boost section with respect to the acceleration rate in the fixed section. As a result, the contrast time resolution and the frame time resolution in the boost section can be further improved as compared with the fixed section.

Hereinafter, a case where the view sharing method is used as the thinning data collection method will be described. The view sharing method is a method of sharing k-space data between a plurality of frames. In the present embodiment, keyhole imaging can be applied as one of the view sharing methods.

FIG. 12 is a diagram schematically showing keyhole imaging according to the present embodiment. In FIG. 12, the k space has five k space subregions from the origin toward the edge, that is, the central region RC, the first marginal region RE1, the second marginal region RE2, and the third side. It is divided into an edge portion region RE3 and a fourth edge portion region RE4. The central region RC and the first marginal region RE1 belong to the low frequency region, and the second marginal region RE2, the third marginal region RE3, and the fourth marginal region RE4 belong to the high frequency region. Belongs to. That is, the low frequency region is set in a wider range than the central region RC. The low frequency region and the high frequency region are preset. "○" indicates that data collection is performed, "x" indicates that data collection is not performed, and "Δ" indicates duplication of k-space data. Although only the ky direction is shown in FIG. 12 for the sake of clarity, it is assumed that the low frequency region and the high frequency region are similarly set in the kx direction as well.

As shown in FIG. 12, it is assumed that the frame 1 is a frame in front of the boost section in time, and the frames 2, the frame 3 and the frame 4 are frames in the boost section. In the stage before the boost section, the sequence control circuit 29 synchronously controls the gradient magnetic field power supply 21, the transmission circuit 23, and the reception circuit 25, and the entire k-space partial region RC including the low frequency region and the high frequency region for the frame 1. Data are collected for RE1, RE2, RE3, and RE4. In the boost section, the sequence control circuit 29 applies keyhole imaging to dynamic boost imaging. Specifically, in the boost section, only the central region RC belonging to the low frequency region and the first marginal region RE1 are collected, and the second marginal region RE2 and the third side belonging to the high frequency region are collected. Data is not collected for the edge region RE3 and the fourth edge region RE4. At this time, the k-space data in the low frequency region between the frames 2, 3 and 4 of the boost section is shifted forward with the passage of time so that the collection order of the k-space data in the central region RC belonging to the low frequency region shifts forward with the passage of time. The collection order of is changed.

When performing image reconstruction for frame 2, frame 3 and frame 4 in the boost section, the processing circuit 51 performs view sharing in which k-space data in the high frequency region of frame 1 is shared in frame 2, frame 3 and frame 4. conduct. That is, the processing circuit 51 duplicates (copies) the actually measured k-space data in the high frequency region of the frame 1, and fills the high frequency regions of the frames 2, 3 and 4 with the duplicated k-space data. Generate a k-space data set for the frame. After that, the processing circuit 51 generates a reconstructed image based on the k-space data set of the frame.

In the above description, it is assumed that the data is collected in the first stage of the boost section in the frame 1 in which the data is collected for the entire k-space subregion. However, this embodiment is not limited to this. In the frame 1, data collection may be performed after the boost section, or data collection may be performed within the boost section.

In this way, in keyhole imaging, data is collected only in the low frequency region. Therefore, by applying keyhole imaging to dynamic boost imaging, data is collected not only in the low frequency region but also in the high frequency region. Therefore, the frame time resolution and the contrast time resolution can be further improved.

The thinned-out data collection described above is based on keyhole imaging in which data is not collected in the high frequency region. However, the thinning data collection according to the present embodiment is not limited to this. For example, in the thinning data collection according to the present embodiment, data collection may be performed in a high frequency region. As such an applied thinning data collection method, various methods such as TRICKS (time-resolved imaging with contrast kinetics), DISCO (differential subsampling with cartesian ordering), and TWIST (time-resolved imaging with stochastic trajectories) can be used. be.

FIG. 13 is a diagram schematically showing applied thinning data collection according to the present embodiment. In FIG. 13, it is assumed that the frame 1, the frame 2 and the frame 3 belong to the boost section. The sequence control circuit 29 synchronously controls the gradient magnetic field power supply 21, the transmission circuit 23, and the reception circuit 25, and collects data between the frames 1, the frame 2, and the frame 3 over each frame in the low frequency region. Thinning data is collected in the high frequency region. Data is sequentially collected in the second marginal region RE2, the third marginal region RE3, and the fourth marginal region RE4, which belong to the high frequency region over the frame 1, the frame 2, and the frame 3.

Specifically, as shown in FIG. 13, data is collected from the central region RC, the first marginal region RE1 and the fourth marginal region RE4 with respect to the frame 1. Of the three regions of the central region RC, the first marginal region RE1 and the fourth marginal region RE4, the central region RC is finally collected. With respect to the frame 2, data is collected from the central region RC, the first marginal region RE1 and the third marginal region RE3. Of the three regions of the central region RC, the first marginal region RE1 and the third marginal region RE3, the central region RC collects data in the middle. With respect to the frame 3, data is collected from the central region RC, the first marginal region RE1 and the second marginal region RE2. Of the three regions of the central region RC, the first marginal region RE1 and the second marginal region RE2, the central region RC is first collected.

When performing image reconstruction for each frame, the processing circuit 51 reconstructs the image by diverting the k-space data of the k-space subregion for which data has not been collected from the same k-space subregion of the other frame for which data has been collected. I do. For example, in the case of frame 1, data is collected in the marginal region RE4, and data is not collected in the marginal regions RE3 and RE2. The marginal region RE3 collects data in frame 2, and the marginal region RE2 collects data in frame 3. The processing circuit 51 duplicates the k-space data of the marginal region RE3 of the frame 2 and fills the marginal region RE3 of the frame 1, and duplicates the k-space data of the marginal region RE2 of the frame 3 to frame. The marginal region RE3 of 1 is filled, and the k-space data of the entire k-space partial region of the frame 1 is aligned. Then, the processing circuit 51 applies a reconstruction method such as FFT to the k-space data of the entire k-space partial region of the frame 1 to generate a reconstructed image.

In this way, the contrast time resolution can be further accelerated by gradually advancing the data collection timing in the central region between a plurality of frames while collecting the thinned data. Further, by using the thinning data acquisition and the view sharing method together, it is possible to perform imaging with high contrast time resolution while maintaining the image quality in the high frequency region. Further, unlike the above-mentioned keyhole imaging, since the k-space data of the k-space subregion of the frames that are close in time is diverted, the temporal discrepancy of the diverted data can be reduced.

Refers to the order in which the strength of the encoding step is changed. For example, in the case of the Cartesian method in which two-dimensional data is collected for each phase encoding step, the order of changing the intensity of the phase encoding step corresponds to the collecting order according to the present embodiment. For example, in the case of the Cartesian method in which three-dimensional data collection is performed for each phase encoding step and slice encoding step, the order of changing the intensities of the phase encoding step and the slice encoding step corresponds to the collection order according to the present embodiment.

As described above, the magnetic resonance imaging apparatus according to the present embodiment includes a sequence control circuit 29 and a processing circuit 51. The sequence control circuit 29 executes a pulse sequence in which the collection order of k-space data is different among a plurality of frames in the time series, and collects the k-space data related to the plurality of frames in the time series. The processing circuit 51 generates a plurality of time-series reconstructed images based on k-space data related to the plurality of frames.

According to the above configuration, the contrast time resolution can be freely adjusted only by changing the collection order of k-space data between frames.

Thus, according to at least one or more embodiments described above, it is possible to adjust the time resolution without reducing the amount of data collected.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... Magnetic resonance imaging device, 11 ... Stand, 13 ... Sleeper, 21 ... Diagonal magnetic field power supply, 23 ... Transmission circuit, 25 ... Reception circuit, 27 ... Sleep drive device, 29 ... Sequence control circuit, 41 ... Static magnetic field magnet, 43 ... gradient magnetic field coil, 45 ... transmit coil, 47 ... receive coil, 50 ... host PC, 51 ... processing circuit, 53 ... storage circuit, 55 ... display circuit, 57 ... input circuit, 59 ... network IF, 61 ... communication IF, 131 ... Top plate, 133 ... Base, 511 ... Reconstruction function, 513 ... Image processing function, 515 ... Pulse sequence generation function, 517 ... System control function.

Claims (10)

A sequence control unit that executes a pulse sequence in which the collection order of k-space data is different among a plurality of frames in a time series and collects k-space data related to the plurality of frames in a time series.
An image generation unit that generates a plurality of time-series reconstructed images based on k-space data related to the plurality of frames, and an image generation unit.
The magnetic resonance imaging apparatus comprising,
The sequence control unit advances the collection timing of the central region of the k-space data in terms of time as the frame is later in time among the plurality of frames.
Magnetic resonance imaging device . Said sequence control unit, said changing the acquisition timing of the center region at regular intervals over a plurality of frames, a magnetic resonance imaging apparatus according to claim 1. Further comprising, a magnetic resonance imaging apparatus according to claim 1, wherein a storage unit for storing the k-space data for the plurality of frames each associated with a collection timing of the central region. The k-space filling method of the pulse sequence is the Cartesian method.
The sequence control unit makes the order of changing the intensities of the phase encoding step and the slice encoding step different as the collection order of the k-space data among the plurality of frames.
The magnetic resonance imaging apparatus according to claim 1. The magnetic resonance imaging apparatus according to claim 1, wherein the sequence control unit applies keyhole imaging in a specific time interval in which the collection order of the k-space data is different between the plurality of frames. The sequence control unit has a specific time interval in which the collection order of the k-space data is different among the plurality of frames and another time interval in which the collection order of the k-space data is fixed among the plurality of frames. The magnetic resonance imaging apparatus according to claim 1, wherein the number of sampling points of k-space data in the specific time interval is reduced as compared with the number of sampling points of k-space data in the other time interval. Further, a designation unit for designating a specific time interval that causes the collection order of the k-space data to be different over the plurality of frames is provided.
Said sequence controller, said at a particular time interval to execute the pulse sequence collection order is different of the k-space data, perform other pulse sequence acquisition order of the k-space data is fixed in the other time interval do,
The magnetic resonance imaging apparatus according to claim 1. The other time interval includes a first section preceding the specific time section and a second section following the specific time section.
The k-space data includes a central region and a plurality of marginal regions.
The sequence control unit collects the central region last in the first section, and collects the central region by changing the collection timing of the central region stepwise from the end to the beginning in the specific time section. In the second section, the central region is collected first.
The magnetic resonance imaging apparatus according to claim 7. Further comprising a designation unit whether to execute the pulse sequence to vary the acquisition order of the k-space data between said plurality of frames is specified,
The sequence control unit executes the pulse sequence when execution is specified by the designated unit, and executes another pulse sequence for fixing the collection order of k-space data when execution is not specified by the designated unit. ,
The magnetic resonance imaging apparatus according to claim 1. The k-space filling method of the pulse sequence is a radial method.
When imaging a volume containing a plurality of slices having different positions in real space, the sequence control unit executes the pulse sequence so that the collection order of k-space data is different among a plurality of frames in a time series relating to the same slice. do,
The magnetic resonance imaging apparatus according to claim 1.

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