JP7313804B2 - Magnetic resonance imaging system - Google Patents

Description

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

One of the k-space data filling methods is a radial method for filling data radially. Since the radial method collects data along a line passing through the center of k-space each time, it is difficult to suppress fat in the gradient echo method using the radial method. In order to obtain a T1-weighted image, an inversion pulse is applied as a preparation pulse prior to data acquisition, but fat is emphasized when TE is short. In order to obtain a T1-weighted image in which fat is suppressed, there is also a method of applying a fat suppression pulse as a preparation pulse immediately before data acquisition. However, the fat suppression effect decreases over time.

U.S. Patent Application Publication No. 2015/268319 U.S. Patent Application Publication No. 2008/161678 U.S. Patent Application Publication No. 2007/007958

A problem to be solved by the present invention is to provide a pulse sequence based on the gradient echo method capable of suppressing reduction in the effects of preparation pulses.

A magnetic resonance imaging apparatus according to an embodiment is a magnetic resonance imaging apparatus comprising a control circuit that is divided into a number of first segments and that executes a pulse sequence that fills k-space with radial acquisition, wherein the first segment is configured to perform a plurality of second segments after application of a first preparation pulse, and the second segment is configured to acquire at least one line in the k-space after application of a second preparation pulse.

FIG. 1 is a diagram showing the configuration of a magnetic resonance imaging apparatus according to this embodiment. FIG. 2 is a diagram showing an example of a gradient echo-based pulse sequence for obtaining a fat-suppressed T1-weighted image according to the present embodiment. FIG. 3 is a diagram showing an example of a pulse sequence including T2 preparation pulses according to this embodiment. FIG. 4 is a diagram showing an example of a pulse sequence regarding electrocardiographic gated imaging according to this embodiment. FIG. 5 is a diagram showing an example of a standard pulse sequence based on gradient echoes for obtaining a fat-suppressed T1-weighted image.

A magnetic resonance imaging apparatus according to this embodiment will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of a magnetic resonance imaging apparatus 1 according to this embodiment. As shown in FIG. 1, the magnetic resonance imaging apparatus 1 has a pedestal 11, a bed 13, a gradient magnetic field power supply 21, a transmission circuit 23, a reception circuit 25, a bed driving 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 pedestal 11 . A hollow bore is formed in the housing of the pedestal 11 . A transmitting coil 45 and a receiving coil 47 are arranged in the bore of the pedestal 11 .

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

The gradient magnetic field coil 43 is a coil unit attached inside the static magnetic field magnet 41 and formed in a hollow, substantially cylindrical shape. The gradient magnetic field coil 43 receives current supply from the gradient magnetic field power supply 21 and generates a gradient magnetic field. More specifically, the gradient magnetic field coil 43 has three coils corresponding to mutually orthogonal X-, Y-, and Z-axes. The three coils form gradient magnetic fields with magnetic field strengths varying along the X, Y, and Z axes. Gradient magnetic fields along the X, Y, and Z axes are combined to form a slice selection gradient magnetic field Gs, a phase encoding gradient magnetic field Gp, and a readout gradient magnetic field Gr, which are orthogonal to each other, in desired directions. These gradient magnetic fields are applied to the subject P while being superimposed on the static magnetic field. A slice selection gradient magnetic field Gs is used to arbitrarily determine an imaging section. A phase-encoding magnetic field gradient Gp is utilized to vary the phase of the MR signal according to spatial position. The readout magnetic field gradient Gr is used to vary the frequency of the MR signal according to spatial position. In the following description, the direction of gradient of the slice selection gradient magnetic field Gs is the Z axis, the direction of gradient of the phase encoding gradient magnetic field Gp is the Y axis, and the direction of gradient of the readout gradient magnetic field Gr is the X axis.

The gradient magnetic field power supply 21 supplies current to the gradient magnetic field coils 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, the Y-axis, and the Z-axis. 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. FIG.

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

The transmission circuit 23 supplies current to the transmission coil 45 in order to apply an RF magnetic field pulse to the subject P via the transmission coil 45 to excite the target protons present in the subject P. Protons of hydrogen atoms are typically used as target protons. The RF magnetic field pulse oscillates at a resonant frequency characteristic of the protons of interest and excites the protons of interest. Magnetic resonance signals (hereinafter referred to as MR signals) are generated from the excited target protons and detected by the receiving coil 47 . The transmission coil 45 is, for example, a whole-body coil (WB coil). As described below, the whole body coil may be used as a transmit/receive coil.

The receiving coil 47 receives MR signals emitted from target protons present in the subject P under the action of RF magnetic field pulses. 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 receive coil 47 has a plurality of receive channels implemented in parallel. The receive channel has a receive coil element for receiving the MR signal, an amplifier for amplifying the MR signal, and the like. An MR signal is output for each reception channel. The total number of reception channels and the total number of reception coil elements may be the same, or the total number of reception channels may be larger or smaller than the total number of reception coil elements.

The receiving circuit 25 receives MR signals generated from the excited target protons via the receiving coil 47 . The receiving circuit 25 processes the received MR signal to generate a digital MR signal. A digital MR signal is called raw data. Raw data is supplied to the host PC 50 via wire or wireless.

Note that the transmission coil 45 and the reception coil 47 described above 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. Also, the transmission coil 45, the reception coil 47, and the transmission/reception coil may be combined.

A bed 13 is installed adjacent to the gantry 11 . The bed 13 has a top board 131 and a base 133 . A subject P is placed on the top plate 131 . The base 133 supports the top plate 131 so as to be slidable along each of the X-axis, Y-axis, and Z-axis. The bed driving device 27 is accommodated in the base 133 . The bed driving device 27 moves the top plate 131 under the control of the sequence control circuit 29 . Any motor such as a servo motor or a stepping motor may be used as the bed driving device 27, for example.

The sequence control circuit 29 has a CPU (Central Processing Unit) or MPU (Micro Processing Unit) processor and memories such as ROM (Read Only Memory) and 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 IF 61, and performs data acquisition on the subject P with a pulse sequence according to the pulse sequence information.

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

The processing circuit 51 has, as hardware resources, processors such as a CPU, a GPU (Graphical Processing Unit), and an MPU, and memories such as a ROM and a RAM. The processing circuit 51 has a reconstruction function 511, an image processing function 513, and a system control function 515 by executing various programs. Note that the reconfiguration function 511, the image processing function 513, and the system control function 515 may be realized by an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), another complex programmable logic device (CPLD), or a simple programmable logic device (SPLD). The reconstruction function 511, the image processing function 513 and the system control function 515 may be implemented on a single board or distributed over multiple boards.

In the reconstruction function 511, the processing circuitry 51 performs reconstruction processing on the raw data to reconstruct an image. Specifically, FFT (Fast Fourier Transform) or the like is used as the reconstruction processing.

In the image processing function 513, the processing circuit 51 performs various image processing on the 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.

The processing circuit 51 in the system control function 515 controls the entire magnetic resonance imaging apparatus 1 according to this 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. Also, the storage circuit 53 may be a driving device or the like that reads and writes various information from/to a portable storage medium such as a CD-ROM drive, a DVD drive, or a flash memory. For example, the storage circuit 53 stores raw data, programs, and the like collected by various scans.

The display circuit 55 displays various information. For example, the display circuit 55 displays an image generated by the reconstruction function 511, an image processed by the image processing function 513, or the like. The display circuit 55 has a display interface and a display device. A display interface converts data representing a display object into a video signal. A video signal is supplied to a display device. A display device displays a video signal representing an object to be displayed. 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 used as appropriate.

The input circuit 57 specifically has an input device and an input interface. The input device receives various commands from the user. A keyboard, a mouse, various switches, a touch screen, a touch pad, etc. can be used as input devices. The input interface supplies output signals from the input device to the processing circuit 51 via the bus. It should be noted that the input circuit 57 is not limited to having physical operation parts such as a mouse and keyboard. For example, the input circuit includes an electrical signal processing circuit that receives an electrical signal corresponding to an input operation from an external input device provided separately from the magnetic resonance imaging apparatus 1 and outputs the received electrical signal to various circuits.

The network IF 59 is an interface that connects the magnetic resonance imaging apparatus 1, workstations, PACS (Picture Archiving and Communication System), HIS (Hospital Information System), RIS (Radiology Information System), etc. via a LAN (Local Area Network) or the like. The network IF transmits and receives various information to and from connected workstations, PACS, HIS and RIS.

The communication IF 61 is an interface that connects the sequence control circuit 29 and the receiving circuit 25 to the host PC 50 via wire or radio. For example, the communication IF 61 transmits pulse sequence information to the sequence control circuit 29 . Also, the communication IF 61 receives raw data from the receiving circuit 25 .

In addition, 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 PC50. Also, the sequence control circuit 29 and the processing circuit 51 may be mounted on the same substrate. 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 distributed and mounted in a plurality of devices.

The pulse sequence according to this embodiment executed by the sequence control circuit 29 will be described below. Assume that the pulse sequence according to the present embodiment is a pulse sequence based on the gradient echo (GRE) method. A clinical example is the acquisition of fat-suppressed T1-weighted images.

FIG. 5 is a diagram showing an example of a standard pulse sequence based on gradient echoes for obtaining a fat-suppressed T1-weighted image. The pulse sequence of FIG. 5 is divided into multiple segments 100 . In each segment 100, first an inversion recovery (IR) pulse 101 is applied. The inversion pulse 101 is a 180° pulse. Application of the inversion pulse 101 inverts the spins of the tissue. After application of the reversal pulse 101, recovery of longitudinal magnetization begins. After a predetermined inversion time TI elapses, a fat saturation pulse 102 is applied. The fat saturation pulse 102 is specifically a frequency-selective 90° pulse tuned to the resonance frequency of fat protons. The application of the fat saturation pulse 102 causes the magnetization of fat protons to fall further 90° from the XY plane (90°) and become longitudinal magnetization (180°). After application of the fat saturation pulse 102, multiple data acquisitions 103 are performed. One data acquisition 103 corresponds to acquiring raw data along one acquisition line in k-space. Since the fat saturation pulse 102 is applied prior to data acquisition 103, MR signals from fat are suppressed. However, since the recovery of the magnetization of fat protons starts immediately after the application of the fat saturation pulse 102, the fat suppression effect is high immediately after the application of the fat saturation pulse 102, but the fat suppression effect decreases as time passes.

Now assume that each data acquisition 103 is a radial method. In the radial method, data acquisition is performed along a plurality of acquisition lines (spokes) arranged radially through the center of k-space. The raw data at the center of k-space are low frequency components and thus contribute greatly to the image. That is, in the case of the data acquisition 103 by the radial method, since raw data at the center of the k-space is acquired for each data acquisition 103, the reduction in the fat suppression effect becomes remarkable as time elapses after the application of the fat saturation pulse 102.

Radial methods also include UTE (Ultrashort TE) sequences or zero TE (Zero TE) sequences. Radial methods include data acquisition along acquisition lines from one end of k-space through the center to the other, but an example of a radial method is acquisition along acquisition lines from the center of k-space to one end, such as those used in UTE or zero TE sequences.

The sequence control circuit 29 according to the present embodiment executes a pulse sequence based on the gradient echo method, which can suppress reduction in the fat saturation effect due to the fat saturation pulse.

FIG. 2 is a diagram showing an example of a gradient echo-based pulse sequence for obtaining a fat-suppressed T1-weighted image according to the present embodiment. As shown in FIG. 2, the pulse sequence according to this embodiment is divided into multiple first segments 70 . We will refer to the first segment 70 as the outer segment. In each outer segment 70, first an inversion pulse 71 is applied as a first preparation pulse. A plurality of second segments 72 are executed after a predetermined inversion time TI from the application of the inversion pulse 71 . We will refer to the second segment 72 as the inner segment. In each inner segment 72 first a fat saturation pulse 73 is applied as a second preparation pulse. After application of the fat saturation pulse 73, multiple data acquisitions 74 are performed. One data acquisition 74 corresponds to acquiring raw data along one acquisition line in k-space. Each data acquisition 74 may be a Cartesian method as a k-space filling method, but a radial method is preferred. For the radial method, one data acquisition 74 corresponds to acquiring raw data along one acquisition line in k-space. TE is set to a relatively short value to emphasize T1 values between tissues of the subject.

The pulse sequence according to this embodiment can be applied to either two-dimensional data acquisition for one two-dimensional slice or three-dimensional data acquisition for one three-dimensional volume. For two-dimensional data acquisition, hundreds of acquisition lines of data acquisition are performed to fill k-space. For example, if there are 900 acquisition lines, the pulse sequence is divided into 3 or so outer segments and each outer segment is divided into 30 or so inner segments. In this case, one inversion pulse application and 30 or so inner segments are performed in each outer segment, and one fat saturation pulse 73 application and 10 data acquisitions are performed in each inner segment. That is, according to the pulse sequence according to this embodiment, a plurality of fat saturation pulses 73 are applied while raw data for one slice is being acquired.

For three-dimensional data acquisition, thousands to tens of thousands of acquisition lines of data acquisition are performed to fill k-space. For example, if there are 30,000 acquisition lines, the pulse sequence is divided into 100 or so outer segments and each outer segment is divided into 30 or so inner segments. In this case, one inversion pulse application and about 30 inner segments are performed in each outer segment, and one fat saturation pulse 73 application and 10 data acquisitions are sequentially performed in each inner segment. That is, according to the pulse sequence according to this embodiment, a plurality of fat saturation pulses 73 are applied while one volume of raw data is acquired. Note that the three-dimensional data acquisition according to the present embodiment is not multi-slice data acquisition in which data is acquired sequentially for a plurality of slices, but volume data acquisition in which data is acquired for one volume by applying encode pulses in three axial directions.

One of the three-dimensional gradient echo methods incorporating IR pulse application is MPRAGE (Magnetization Prepared Rapid Acquired Gradient Echo) or IR-SPGR (Inversion Recovery Spoiled Gradient Recalled Acquisition In Steady State). MPRAGE or IR-SPGR may be used as three-dimensional data acquisition according to this embodiment.

The operation of the sequence control circuit 29 in MR imaging according to the pulse sequence will be described. First, the sequence control circuit 29 controls the gradient magnetic field power supply 21 and the transmission circuit 23 to apply the inversion pulse 71 together with the slice selection gradient magnetic field. When the elapsed time from the application of the inversion pulse 71 exceeds the inversion time TI, the sequence control circuit 29 controls the transmission circuit 23 to apply the fat saturation pulse 73, and controls the gradient magnetic field power supply 21 to apply the spoiler gradient magnetic field pulse. After applying the fat saturation pulse 73 , the sequence control circuit 29 synchronously controls the gradient magnetic field power supply 21 , the transmission circuit 23 and the reception circuit 25 to perform data acquisition 74 for a predetermined number of times. The predetermined number of times (hereinafter referred to as the number of times of data collection) is the number of times of data collection 74 included in the inner segment 72, and is determined in advance. The number of times of data acquisition is determined to be the number of times that the fat saturation effect due to the application of the fat saturation pulse 73 to each inner segment 72 can be maintained at a predetermined level. The number of data acquisitions is assumed to be the same for all inner segments.

For data acquisition 74 according to the radial method, the sequence control circuit 29 synchronously controls the gradient power supply 21, the transmission circuit 23 and the reception circuit 25 in each data acquisition 74 to acquire raw data along the acquired acquisition line. Specifically, first, the sequence control circuit 29 controls the transmission circuit 23 to apply an RF pulse with a predetermined flip angle, and controls the gradient magnetic field power supply 21 to apply a slice selection gradient magnetic field. Next, the sequence control circuit 29 controls the gradient magnetic field power supply 21 to simultaneously apply a phase-encoding gradient magnetic field and a frequency-encoding gradient magnetic field having a magnetic field strength corresponding to the acquisition line to be acquired, in order to form a readout gradient magnetic field corresponding to the acquisition line to be acquired. An MR signal is generated within a predetermined time frame including the TE time from the application of the RF pulse. The sequence control circuit 29 controls the receiving circuit 25 to receive the MR signal within the time frame. The receiving circuit 25 converts the received MR signal into raw data, and the storage circuit 53 stores the raw data.

In this way, when the data acquisition 74 is performed for the number of times of data acquisition, the sequence control circuit 29 determines whether or not the inner segments 72 have been executed the number of times of the inner segments 72 included in the outer segment 70 (hereinafter referred to as the number of inner segments). If it is determined that the inner segments 72 have not been executed for the number of inner segments, the sequence control circuit 29 applies the fat saturation pulse 73 again and performs data acquisition 74 for the number of times of data acquisition.

After executing the number of inner segments 72, the sequence control circuit 29 determines whether the number of outer segments 70 included in the pulse sequence (hereinafter referred to as the number of outer segments) has been executed. If the sequence control circuit 29 determines that the outer segments 70 have not been executed for the number of outer segments, the sequence control circuit 29 applies the inversion pulse 71 again and executes the inner segments 72 for the number of inner segments. Then, when the outer segments 70 of the number of outer segments are executed, the sequence control circuit 29 ends execution of MR imaging according to the present embodiment.

As shown in FIG. 2, in the pulse sequence according to this embodiment, the data acquisition sequence portion of the outer segment 70 is further divided into a plurality of inner segments 72, and a fat saturation pulse 73 is applied to each inner segment 72. In the pulse sequence according to the present embodiment, the fat saturation pulse 73 is applied more frequently between the inversion pulses 71 than in the pulse sequence of FIG.

When execution of the pulse sequence is finished, processing circuit 51 executes reconstruction function 511 . In the reconstruction function 511, the processing circuit 51 reconstructs a T1-weighted image by performing reconstruction processing such as FFT on the raw data acquired by executing the pulse sequence. A T1 weighted image is displayed on the display circuit 55 . As described above, even if each data acquisition 74 is the radial method, the reduction in the fat saturation effect of the fat saturation pulse 73 is suppressed in each data acquisition 74, so that the processing circuit 51 is able to reconstruct a T1-weighted image in which fat is well suppressed.

In the above pulse sequence, the number of times of data acquisition is assumed to be the same for all inner segments. However, this embodiment is not limited to this and may vary depending on the inner segment. For example, if the data acquisition 74 is the Cartesian method, the inner segments to which the data acquisition 74 does not belong may have more data acquisitions than the inner segments to which the data acquisition 74 belongs for the acquisition line through the center of k-space. For example, in the case of the Cartesian method that collects raw data from the central phase encode, it is preferable to increase the number of data acquisitions of the inner segment as time elapses from the first fat saturation pulse 73 of the inner segment, in other words, to decrease the frequency of application of the fat saturation pulse 73.

Moreover, the above pulse sequence is based on a frequency selective fat suppression method such as the CHESS (Chemical Shift Selective Excitation) method, which is one of techniques for suppressing MR signals from fat. That is, a frequency-selective RF pulse was applied as the fat saturation pulse 73 for suppressing MR signals from fat. However, this embodiment is not limited to this. For example, as a technique for suppressing MR signals from fat, a pulse sequence premised on a non-selective fat suppression method such as STIR (Short TI Inversion Recovery) may be used.

In the above description, it is assumed that the inversion pulse for T1 emphasis is applied as the first preparation pulse. However, this embodiment is not limited to this. For example, a T2 preparation pulse for T2 enhancement may be applied as the first preparation pulse.

FIG. 3 is a diagram showing an example of a pulse sequence including the T2 preparation pulse 75 according to this embodiment. As shown in FIG. 3, the pulse sequence is divided into an outer segment number of outer segments 70 . At each outer segment 70, first a T2 preparation pulse 75 is applied. The T2 preparation pulse 75 is a group of RF pulses for obtaining T2 contrast using the difference in T2 between tissues. The T2 preparation pulse includes, for example, three RF pulses of 90° pulse, 180° pulse, and -90° pulse. A 180° pulse is applied after a lapse of TE/2 from the application of the 90° pulse, and a -90° pulse is applied after a lapse of TE/2 from the application of the 180° pulse. After application of the T2 preparation pulse 75, the number of inner segments 72 are executed. The pulse sequence for inner segment 72 is similar to FIG.

The operation of the sequence control circuit 29 in MR imaging according to the pulse sequence will be described. First, the sequence control circuit 29 controls the transmission circuit 23 to sequentially apply T2 preparation pulses 75 consisting of a 90° pulse, a 180° pulse and a -90° pulse at intervals of TE/2. By applying the T2 preparation pulse 75, the longitudinal magnetization of fat protons with short T2 becomes smaller than the longitudinal magnetization of protons of other tissues with long T2. After applying the T2 preparation pulse 75, the sequence control circuit 29 controls the transmission circuit 23 to apply the fat saturation pulse 73, and controls the gradient magnetic field power supply 21 to apply the spoiler gradient magnetic field pulse. After applying the fat saturation pulse 73, the sequence control circuit 29 synchronously controls the gradient magnetic field power supply 21, the transmission circuit 23, and the reception circuit 25 to perform data collection 74 for the number of times of data collection. The k-space filling method of data acquisition 74 is typically the radial method, but is not limited to this, and may be the Cartesian method.

After the data collection 74 is performed for the number of data collection times, the sequence control circuit 29 determines whether or not the inner segments 72 have been executed for the number of inner segments. If it is determined that the inner segments 72 have not been executed for the number of inner segments, the sequence control circuit 29 applies the fat saturation pulse 73 again and performs data acquisition 74 for the number of data acquisitions. After executing the number of inner segments 72, the sequence control circuit 29 determines whether or not the number of outer segments 70 has been executed. If the sequence control circuit 29 determines that the outer segments 70 have not been executed for the number of outer segments, the sequence control circuit 29 applies the inversion pulse 71 again and executes the inner segments 72 for the number of inner segments. Then, when the number of outer segments 70 is executed, the sequence control circuit 29 terminates execution of MR imaging.

Performing MR imaging following the pulse sequence for T2 weighting of FIG. The processing circuit 51 can reconstruct a T2-weighted image in which fat is appropriately suppressed by performing reconstruction processing on the collected raw data.

According to at least one embodiment described above, the magnetic resonance imaging apparatus 1 has a sequence control circuit 29 . A sequence control circuit 29 executes a pulse sequence based on the gradient echo method that includes a plurality of outer segments. Here, the sequence control circuit 29 executes the inner segments after applying the first preparation pulse in each of the outer segments. Sequence control circuit 29 performs data acquisition for at least one acquisition line in k-space after applying the second preparation pulse in each of the plurality of inner segments.

With the above configuration, since a plurality of second preparation pulses are applied between application of the first preparation pulses, it is possible to suppress reduction in the effect of the second preparation pulses.

In the above description, it was assumed that the first preparation pulse was applied in the outer segment 70 . However, this embodiment is not limited to this. For example, instead of the first preparation pulse, a synchronizing signal in the synchronous imaging method may be used. As the synchronizing signal, in the case of electrocardiographic gated imaging, for example, an electrocardiographic gated signal output from the electrocardiograph upon detection of a predetermined heartbeat phase is used, and in the case of respiratory gated imaging, for example, a respiratory gated signal output from the respirometer upon detection of a predetermined respiratory phase is used. A pulse sequence for synchronized imaging will be described below as an example of ECG synchronized imaging.

FIG. 4 is a diagram showing an example of a pulse sequence for electrocardiographic gated imaging according to this embodiment. As shown in FIG. 4, the pulse sequence according to this embodiment is divided into the number of outer segments 70 . In each outer segment 70 , an electrocardiographic gating signal is first input from the electrocardiograph to the sequence control circuit 29 . After a predetermined delay time TD has elapsed from the input of the ECG gating signal, the inner segments of the number of inner segments are executed. The inner segment pulse sequence is similar to FIG.

The operation of the sequence control circuit 29 in electrocardiographic gated imaging according to the pulse sequence will be described. First, the sequence control circuit 29 waits for the input of the electrocardiographic synchronization signal 76 from the electrocardiograph. When the electrocardiographic synchronous signal 76 is input, the sequence control circuit 29 measures the elapsed time from the input of the electrocardiographic synchronous signal 76 and waits for the elapsed time to pass the delay time TD. When the elapsed time exceeds the delay time TD, the sequence control circuit 29 controls the transmission circuit 23 to apply the fat saturation pulse 73, and controls the gradient magnetic field power supply 21 to apply the spoiler gradient magnetic field pulse. After applying the fat saturation pulse 73, the sequence control circuit 29 synchronously controls the gradient magnetic field power supply 21, the transmission circuit 23, and the reception circuit 25 to perform data collection 74 for the number of times of data collection. The k-space filling method of data acquisition 74 is typically the radial method, but is not limited to this, and may be the Cartesian method.

After the data collection 74 is performed for the number of data collection times, the sequence control circuit 29 determines whether or not the inner segments 72 have been executed for the number of inner segments. If it is determined that the inner segments 72 have not been executed for the number of inner segments, the sequence control circuit 29 applies the fat saturation pulse 73 again and performs data acquisition 74 for the number of times of data acquisition. After executing the number of inner segments 72, the sequence control circuit 29 determines whether or not the number of outer segments 70 has been executed. If it is determined that the number of outer segments 70 has not been executed, the sequence control circuit 29 again executes the number of inner segments 72 after receiving the electrocardiographic synchronization signal 69 . Then, when the outer segments 70 of the number of outer segments are executed, the sequence control circuit 29 ends the execution of the electrocardiographic gated imaging according to this embodiment.

Performing ECG-gated imaging according to the pulse sequence of FIG. The processing circuit 51 can reconstruct an image in which fat is appropriately suppressed by performing reconstruction processing on the collected raw data.

According to the above embodiment, the magnetic resonance imaging apparatus 1 has the sequence control circuit 29 . A sequence control circuit 29 executes a pulse sequence based on the gradient echo method that includes a plurality of outer segments. A sequence control circuit 29 executes a plurality of inner segments after input of a synchronization signal in each of a plurality of outer segments. Sequence control circuit 29 performs data acquisition for at least one acquisition line in k-space after applying the second preparation pulse in each of the plurality of inner segments.

With the above configuration, since a plurality of second preparation pulses are applied between inputs of the synchronization signal, it is possible to suppress reduction in the effect of the second preparation pulses.

The sequence control circuit 29 according to the embodiment described above executes a pulse sequence based on the gradient echo method. The pulse sequence according to this embodiment can also be applied to a combination of a gradient echo method and an echo planar (EPI: Echo Planar Imaging) method. In the case of the EPI method, one data acquisition 74 includes application of a 90° RF pulse followed by alternating polarity reversal application of gradient magnetic field pulses and data acquisition. EPI methods to be combined may be either single-shot EPI or multi-shot EPI. With single-shot EPI, one data acquisition 74 fills one k-space. That is, at least one data acquisition 74 needs to be performed in the inner segment 72 . With multi-shot EPI, multiple data acquisitions 74 fill a single k-space. For example, if four data acquisitions 74 fill one k-space and one data acquisition 74 occurs in the inner segment 72, the fat saturation pulse 73 followed by the data acquisition 74 is repeated four times to fill the one k-space.

While several embodiments of the invention have been described, these embodiments have been 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 modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

Reference Signs List 1 magnetic resonance imaging apparatus 11 pedestal 13 bed 21 gradient magnetic field power supply 23 transmission circuit 25 reception circuit 27 bed driving device 29 sequence control circuit 41 static magnetic field magnet 43 gradient magnetic field coil 45 transmission coil 47 reception coil 50 host PC 51 processing circuit 53 storage circuit 55 display circuit 57 input circuit 70 first segment (outer segment), 71... inversion pulse (first preparation pulse), 72... second segment (inner segment), 73... fat saturation pulse (second preparation pulse), 74... data acquisition, 100... segment, 101... inversion pulse, 102... fat saturation pulse, 103... data acquisition, 131... top plate, 133... base, 511... reconstruction function, 513... image processing function, 515... system control function.

Claims (7)

1. A magnetic resonance imaging apparatus comprising control circuitry that is divided into a plurality of first segments and that executes a pulse sequence that fills k-space with radial acquisitions, comprising:
The first segment has a configuration for executing a plurality of second segments after application of the first preparation pulse,
the second segment is configured to acquire at least one line in the k-space after application of a second preparation pulse;
The control circuit collects data necessary for reconstructing the one volume in three- dimensional data acquisition targeting one three -dimensional volume, and executes the pulse sequence in which a short TE is set to emphasize the T1 value ,
The three-dimensional data acquisition is volume data acquisition in which encoding pulses are applied in three axial directions to acquire data for the one volume.
Magnetic resonance imaging equipment. 2. The magnetic resonance imaging apparatus according to claim 1, wherein said control circuit applies an inversion pulse as said first preparation pulse. 2. The magnetic resonance imaging apparatus according to claim 1, wherein said control circuit applies a fat saturation pulse as said second preparation pulse. 2. A magnetic resonance imaging apparatus according to claim 1, further comprising a processing circuit for reconstructing a T1-weighted image based on data acquired by executing said pulse sequence. 1. A magnetic resonance imaging apparatus comprising control circuitry that is divided into a plurality of first segments and that executes a pulse sequence that fills k-space with radial acquisitions, comprising:
The first segment has a configuration for executing a plurality of second segments after inputting a synchronization signal,
the second segment is configured to acquire at least one line in the k-space after application of a second preparation pulse;
The control circuit collects data necessary for reconstructing the one volume in three- dimensional data acquisition targeting one three -dimensional volume, and executes the pulse sequence in which a short TE is set to emphasize the T1 value ,
The three-dimensional data acquisition is volume data acquisition in which encoding pulses are applied in three axial directions to acquire data for the one volume.
Magnetic resonance imaging equipment. 6. The magnetic resonance imaging apparatus according to claim 5 , wherein said control circuit applies a fat saturation pulse as said second preparation pulse. 6. The magnetic resonance imaging apparatus according to claim 5 , further comprising processing circuitry for reconstructing a T1-weighted image based on data acquired by executing said pulse sequence.