Magnetic resonance imaging apparatus and magnetic resonance imaging method

Abstract

To collect data by increasing an effective sampling rate.SOLUTION: A magnetic resonance imaging apparatus according to an embodiment comprises a sequence control part and a generation part. The sequence control part collects a plurality of magnetic resonance signals while changing a relative relation between an echo and an acquisition window. The generation part generates a magnetic resonance image on the basis of data acquired by synthesizing the plurality of magnetic resonance signals.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The embodiments disclosed in this specification and the drawings relate to a magnetic resonance imaging apparatus and a magnetic resonance imaging method. [Background technology]

[0002] In magnetic resonance imaging devices, the reception band (bandwidth) is primarily determined by the RF (Radio Frequency) coil and sampling rate (SR). A wider reception band offers advantages such as shorter data acquisition time, shorter Echo Time (TE), and less susceptibility to chemical shifts and motion artifacts. Furthermore, a wider reception band also offers advantages such as a wider FOV, assuming the RF coil has a sufficient reception band.

[0003] Therefore, if the sampling interval can be narrowed and the effective sampling rate can be increased, the reception band can be widened. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2010 / 116782 Summary of the Invention [Problem to be solved by the invention]

[0005] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to collect data by increasing the effective sampling rate. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described below can also be positioned as other problems. [Means for solving the problem]

[0006] A magnetic resonance imaging apparatus according to an embodiment includes a sequence controller and a generator. The sequence controller acquires a plurality of magnetic resonance signals while changing the relative relationship between echoes and an acquisition window. The generator generates a magnetic resonance image based on data obtained by combining the plurality of magnetic resonance signals. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a magnetic resonance imaging apparatus according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an outline of the processing performed by the magnetic resonance imaging apparatus according to the embodiment. [Figure 3A] FIG. 3A is a diagram showing a phantom used for verifying the processing performed by the magnetic resonance imaging apparatus according to the embodiment. [Figure 3B] FIG. 3B is a diagram showing an example of an image obtained by the first pulse sequence in the magnetic resonance imaging apparatus according to the embodiment. [Figure 3C] FIG. 3C is a diagram showing an example of an image obtained by a second pulse sequence in the magnetic resonance imaging apparatus according to the embodiment. [Figure 3D] FIG. 3D is a diagram showing an example of a composite image obtained in the magnetic resonance imaging apparatus according to the embodiment. [Figure 4] FIG. 4 is a flowchart illustrating an example of the flow of processing performed by the magnetic resonance imaging apparatus according to the first embodiment. [Figure 5] FIG. 5 is a diagram illustrating an example of a pulse sequence executed by the magnetic resonance imaging apparatus according to the first embodiment. [Figure 6] FIG. 6 is a diagram illustrating an example of a pulse sequence executed by the magnetic resonance imaging apparatus according to the first embodiment. [Figure 7]FIG. 7 is a flowchart illustrating an example of the flow of processing performed by the magnetic resonance imaging apparatus according to the second embodiment. [Figure 8] FIG. 8 is a diagram illustrating an example of a pulse sequence executed by the magnetic resonance imaging apparatus according to the second embodiment. [Figure 9] FIG. 9 is a diagram illustrating an example of a pulse sequence executed by the magnetic resonance imaging apparatus according to the third embodiment. [Figure 10] FIG. 10 is a diagram illustrating an example of a pulse sequence executed by the magnetic resonance imaging apparatus according to the third embodiment. [Figure 11] FIG. 11 is a diagram illustrating an example of a pulse sequence executed by the magnetic resonance imaging apparatus according to the third embodiment. [Figure 12] FIG. 12 is a diagram illustrating an example of a pulse sequence executed by the magnetic resonance imaging apparatus according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of a magnetic resonance imaging apparatus and a magnetic resonance imaging method will be described in detail with reference to the drawings.

[0009] (First embodiment) FIG. 1 is a block diagram showing a magnetic resonance imaging apparatus 100 according to a first embodiment. As shown in FIG. 1, the magnetic resonance imaging apparatus 100 includes a static magnetic field magnet 101, a static magnetic field power supply (not shown), a gradient magnetic field coil 103, a gradient magnetic field power supply 104, a bed 105, a bed control circuit 106, a transmission coil 107, a transmission circuit 108, a reception coil 109, a reception circuit 110, a sequence control circuit 120 (sequence control unit), and a computer 130 (also referred to as an "image processing device"). Note that the magnetic resonance imaging apparatus 100 does not include a subject P (e.g., a human body). The configuration shown in FIG. 1 is merely an example. For example, the components of the sequence control circuit 120 and the computer 130 may be integrated or separated as appropriate.

[0010] The static magnetic field magnet 101 is a magnet formed in a hollow, approximately cylindrical shape, and generates a static magnetic field in the internal space. The static magnetic field magnet 101 is, for example, a superconducting magnet. As another example, the static magnetic field magnet 101 may be a permanent magnet.

[0011] The gradient magnetic field coil 103 is a hollow, approximately cylindrical coil and is disposed inside the static magnetic field magnet 101. The gradient magnetic field coil 103 is formed by combining three coils corresponding to the mutually orthogonal X, Y, and Z axes, and these three coils are individually supplied with current from a gradient magnetic field power supply 104 to generate gradient magnetic fields whose magnetic field strengths change along the X, Y, and Z axes. The gradient magnetic fields of the X, Y, and Z axes generated by the gradient magnetic field coil 103 are, for example, a slicing gradient magnetic field Gs, a phase encoding gradient magnetic field Ge, and a readout gradient magnetic field Gr. The gradient magnetic field power supply 104 supplies current to the gradient magnetic field coil 103.

[0012] The bed 105 includes a top plate 105a on which the subject P is placed, and under the control of a bed control circuit 106, the top plate 105a is inserted into the cavity (imaging port) of the gradient magnetic field coil 103 with the subject P placed thereon. The bed 105 is usually installed so that its longitudinal direction is parallel to the central axis of the static magnetic field magnet 101. Under the control of a computer 130, the bed control circuit 106 drives the bed 105 to move the top plate 105a in the longitudinal direction and up and down.

[0013] The transmission coil 107 is disposed inside the gradient magnetic field coil 103, and receives RF pulses from a transmission circuit 108 to generate a high frequency magnetic field.

[0014] The transmission circuit 108 includes a pulse generator, an RF generator, a modulator, and an RF amplifier, and supplies RF pulses corresponding to a Larmor frequency determined by the type of atom of interest and the magnetic field strength to the transmission coil 107. The pulse generator generates a waveform of an RF pulse signal. The RF generator generates an RF signal at a resonance frequency. The modulator generates an RF pulse signal by modulating the amplitude of the RF signal generated by the RF generator with the waveform generated by the pulse generator. The RF amplifier amplifies the RF pulse signal generated by the modulator and outputs it to the transmission coil 107.

[0015] The receiving coil 109 is disposed inside the gradient magnetic field coil 103, and receives magnetic resonance signals (hereinafter referred to as "MR signals" as necessary) emitted from the subject P due to the influence of the high frequency magnetic field. Upon receiving the magnetic resonance signals, the receiving coil 109 outputs the received magnetic resonance signals to the receiving circuit 110.

[0016] The above-described transmitting coil 107 and receiving coil 109 are merely examples. They may be configured by combining one or more of a coil having only a transmitting function, a coil having only a receiving function, or a coil having a transmitting and receiving function.

[0017] The receiving circuit 110 detects magnetic resonance signals output from the receiving coil 109 and generates magnetic resonance data based on the detected magnetic resonance signals. Specifically, the receiving circuit 110 generates magnetic resonance data by digitally converting the magnetic resonance signals output from the receiving coil 109. The receiving circuit 110 also transmits the generated magnetic resonance data to the sequence control circuit 120. The receiving circuit 110 may be provided on the gantry side that includes the static magnetic field magnet 101, the gradient magnetic field coil 103, etc. Furthermore, some of the functions of the receiving circuit 110, for example, digital conversion of magnetic resonance signals, may be provided in the receiving coil 109.

[0018] The sequence control circuit 120 drives the gradient magnetic field power supply 104, the transmission circuit 108, and the reception circuit 110 based on sequence information transmitted from the computer 130, thereby imaging the subject P. Here, the sequence information is information that defines a procedure for performing imaging. The sequence information defines the strength of the current supplied by the gradient magnetic field power supply 104 to the gradient magnetic field coil 103 and the timing of supplying the current, the strength of the RF pulse supplied by the transmission circuit 108 to the transmission coil 107 and the timing of applying the RF pulse, and the timing of detecting a magnetic resonance signal by the reception circuit 110. For example, the sequence control circuit 120 is an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array), or an electronic circuit such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). Details of the pulse sequence executed by the sequence control circuit 120 will be described later.

[0019] Furthermore, the sequence control circuit 120 drives the RF amplifier via the gradient magnetic field power supply 104 and the transmission circuit 108, and also drives the reception circuit 110 to image the subject P, and when it receives magnetic resonance data from the reception circuit 110, it transfers the received magnetic resonance data to the computer 130. As an example, the sequence control circuit 120 arranges the magnetic resonance data received from the reception circuit 110 two-dimensionally or three-dimensionally according to position information given by the readout gradient magnetic field, the phase encoding gradient magnetic field, and the slice gradient magnetic field, and stores the data constituting k-space in a memory 132 serving as a storage unit.

[0020] The computer 130 performs overall control of the magnetic resonance imaging apparatus 100 and generates images. The computer 130 includes a memory 132, an input device 134, a display 135, and a processing circuit 150. The processing circuit 150 includes an interface function 131, a control function 133, and a generation function 136.

[0021] In the first embodiment, the processing functions performed by the interface function 131, the control function 133, and the generation function 136 are stored in the memory 132 in the form of computer-executable programs. The processing circuit 150 is a processor that reads and executes the programs from the memory 132 to realize the functions corresponding to the programs. In other words, the processing circuit 150, after reading the programs, has the functions shown in the processing circuit 150 in FIG. 1 . Note that FIG. 1 illustrates the processing functions performed by the interface function 131, the control function 133, and the generation function 136 being realized by a single processing circuit 150. However, the processing circuit 150 may be configured by combining multiple independent processors, and each processor may execute a program to realize the functions. In other words, each of the above functions may be configured as a program, and a single processing circuit 150 may execute each program. As another example, a specific function may be implemented in a dedicated, independent program execution circuit. Note that in FIG. 1, the interface function 131, the control function 133, and the generation function 136 are examples of a reception unit, a control unit, and a generation unit, respectively. The sequence control circuit 120 is an example of a sequence control unit.

[0022] The term "processor" used in the above description refers to circuits such as a CPU (Central Processing Unit), a GPU (Graphical Processing Unit), an Application Specific Integrated Circuit (ASIC), a programmable logic device (e.g., a Simple Programmable Logic Device (SPLD), a Complex Programmable Logic Device (CPLD), and a Field Programmable Gate Array (FPGA)). The processor realizes its functions by reading and executing programs stored in memory 132.

[0023] Furthermore, instead of storing the program in the memory 132, the program may be directly embedded in the processor circuitry. In this case, the processor performs its functions by reading and executing the program embedded in the circuitry. The bed control circuitry 106, the transmission circuitry 108, the reception circuitry 110, etc. are also similarly configured using electronic circuits such as the processor.

[0024] The processing circuitry 150 transmits sequence information to the sequence control circuitry 120 via the interface function 131, and receives magnetic resonance data from the sequence control circuitry 120. Furthermore, upon receiving the magnetic resonance data, the processing circuitry 150 having the interface function 131 stores the received magnetic resonance data in the memory 132.

[0025] The magnetic resonance data stored in the memory 132 is arranged in k-space by the control function 133. As a result, the memory 132 stores the k-space data.

[0026] The memory 132 stores magnetic resonance data received by the processing circuitry 150 having the interface function 131, k-space data arranged in k-space by the processing circuitry 150 having the control function 133, image data generated by the processing circuitry 150 having the generation function 136, etc. For example, the memory 132 is a semiconductor memory element such as a RAM (Random Access Memory), a flash memory, a hard disk, an optical disk, etc.

[0027] The input device 134 accepts various instructions and information input from an operator. The input device 134 is, for example, a pointing device such as a mouse or a trackball, a selection device such as a mode switch, or an input device such as a keyboard. The display 135, under the control of the processing circuit 150 having the control function 133, displays a GUI (Graphical User Interface) for accepting input of imaging conditions, an image generated by the processing circuit 150 having the generation function 136, and the like. The display 135 is, for example, a display device such as a liquid crystal display.

[0028] The processing circuitry 150 performs overall control of the magnetic resonance imaging apparatus 100 using the control function 133, and controls imaging, image generation, image display, etc. For example, the processing circuitry 150 having the control function 133 accepts input of imaging conditions (imaging parameters, etc.) on a GUI and generates sequence information according to the accepted imaging conditions. The processing circuitry 150 having the control function 133 also transmits the generated sequence information to the sequence control circuit 120. The processing circuitry 150 uses the generation function 136 to read k-space data from the memory 132 and perform reconstruction processing such as Fourier transform on the read k-space data to generate an image.

[0029] Up to this point, the magnetic resonance imaging apparatus 100 of the embodiment has been described as having a configuration with two magnets sandwiching the subject or a configuration with a cylindrical magnet, as illustrated in FIG. 1 . However, the magnetic resonance imaging apparatus 100 of the embodiment is not limited to such a configuration. While these magnetic resonance imaging apparatuses 100 are intended to perform imaging in a region with a uniform static magnetic field, they may also be used in a technology in which an imaging region is a region with a distribution in the static magnetic field. An example of a configuration with a distribution in the static magnetic field is a configuration in which only one of the two magnets sandwiching the subject is included. Furthermore, even in the case of a cylindrical magnet, an imaging region in which the distribution of the static magnetic field is non-uniform near the opening of the bore can also be used.

[0030] Next, the background of the embodiment will be briefly described.

[0031] In magnetic resonance imaging systems, the reception band (bandwidth) is primarily determined by the RF coil and sampling rate (SR). A wider reception band offers advantages such as shorter data acquisition time, shorter TE, and less susceptibility to chemical shifts and motion artifacts. Furthermore, a wider reception band offers advantages such as a wider FOV, assuming the RF coil has a sufficient reception band. The reception band can be widened by narrowing the sampling interval and increasing the effective sampling rate.

[0032] In view of this background, a magnetic resonance imaging apparatus according to an embodiment includes a sequence controller and a generator. The sequence controller acquires multiple magnetic resonance signals while changing the relative relationship between echoes and acquisition windows. The generator generates a magnetic resonance image based on data obtained by combining the multiple magnetic resonance signals.

[0033] In addition, the magnetic resonance imaging method according to the embodiment acquires multiple magnetic resonance signals while changing the relative relationship between the echo and the acquisition window, and generates a magnetic resonance image based on data obtained by combining the multiple magnetic resonance signals.

[0034] FIG. 2 illustrates an outline of such an idea. A sequence control circuit 120 executes a pulse sequence multiple times. In FIG. 2, the sequence control circuit 120 executes a first pulse sequence 10a corresponding to a first acquisition AD1 and a second pulse sequence 10b corresponding to a second acquisition AD2. Acquisition periods 15 and 16 are data acquisition periods corresponding to the first pulse sequence 10a and the second pulse sequence 10b, respectively. Sampling points 1a, 1b, 1c, and 1d represent data points acquired during the acquisition period 15 of the first pulse sequence 10a. Sampling points 2a, 2b, 2c, and 2d represent data points acquired during the acquisition period 16 of the second pulse sequence 10b. Each sampling point corresponds to data for one point in k-space, for example. A sampling interval SR13 indicates the time interval for sampling; the smaller the sampling interval SR13, the higher the sampling rate.

[0035] Here, the sequence control circuit 120 performs acquisition by relatively shifting the echo and the acquisition window (AW) during the multiple pulse sequences it executes. For example, the sequence control circuit 120 performs acquisition by shifting the timing of the acquisition window AW between the first pulse sequence 10a and the second pulse sequence 10b by an interval 14, which is half the sampling interval SR13. Subsequently, after data acquisition, as shown in the lower part of FIG. 2, the data acquired by the first pulse sequence 10a and the data acquired by the second pulse sequence 10b are synthesized in k-space to generate synthesized data 17, and image reconstruction is performed based on this synthesized data.

[0036] In this way, the sequence control circuit 120 can improve the sampling rate artificially by shifting the echoes by a time interval smaller than the sampling interval SR. For example, by shifting the timing of the acquisition window AW by 1 / N of the sampling interval SR, the acquisition bandwidth can be widened by N times.

[0037] 3A to 3D show examples of images obtained by the method according to the embodiment. FIG. 3A shows a phantom imaged, with region 29 representing the FOV (Field of View). The sequence control circuit 120 acquired data twice by shifting the timing of the echo and the acquisition window AW. Image 26 in FIG. 3B is an image reconstructed from data acquired by the first pulse sequence 10a. Image 27 in FIG. 3C is an image reconstructed from data acquired by the second pulse sequence 10b. Image 28 in FIG. 3D is an image obtained by combining data acquired by the first pulse sequence 10a and data acquired by the second pulse sequence 10b and then reconstructing the data. By performing acquisition multiple times by shifting the timing of the echo and the acquisition window AW in this way, the sampling rate can be effectively extended and the sampling interval can be effectively halved, thereby increasing the bandwidth and enabling imaging of a wider FOV.

[0038] The embodiment will be described in more detail below with reference to Figures 4 to 6. Figure 4 is a flowchart illustrating the flow of processing executed by the magnetic resonance imaging apparatus 100 according to the first embodiment.

[0039] First, in step S100A, the sequence control circuit 120 acquires a plurality of magnetic resonance signals while changing the relative relationship between the echo and the acquisition window AW. The sequence control circuit 120 acquires a plurality of magnetic resonance signals while changing the relative relationship between the echo and the acquisition window AW by shifting the acquisition window AW by an amount smaller than the sampling interval SR.

[0040] 5 shows an example in which the pulse sequence executed by the sequence control circuit 120 is a spin echo (SE) pulse sequence. In step S100A, the first pulse sequence 10a executed by the sequence control circuit 120 is composed of a 90-degree pulse 20, a 180-degree pulse 21, and an acquisition window AW23a. An echo 25 is generated when TE22 has elapsed since the application of the 90-degree pulse 20. The second pulse sequence 10b executed by the sequence control circuit 120 is composed of a 90-degree pulse 20, a 180-degree pulse 21, and an acquisition window AW23b. An echo 25 is generated when TE22 has elapsed since the application of the 90-degree pulse 20. Here, the sequence control circuit 120 shifts the acquisition window AW23b from the acquisition window AW23a by a period 24 corresponding to ½ of the sampling interval SR. In this way, the sequence control circuit 120 acquires a plurality of magnetic resonance signals while changing the relative relationship between the echo and the acquisition window.

[0041] 6 shows an example in which the pulse sequence executed by the sequence control circuit 120 is a field echo (FE) pulse sequence. In step S100A, the first pulse sequence 10a executed by the sequence control circuit 120 is composed of a 90-degree pulse 20 and an acquisition window AW23a, and an echo 25 is generated when TE22 has elapsed since the application of the 90-degree pulse 20. The second pulse sequence 10b executed by the sequence control circuit 120 is composed of a 90-degree pulse 20 and an acquisition window AW23b, and an echo 25 is generated when TE22 has elapsed since the application of the 90-degree pulse 20. Here, the sequence control circuit 120 shifts the acquisition window AW23b from the acquisition window AW23a by a period 24 corresponding to ½ of the sampling interval SR. As a result, the sequence control circuit 120 acquires a plurality of magnetic resonance signals while changing the relative relationship between the echo and the acquisition window.

[0042] Returning to FIG. 4, in step S200, the processing circuitry 150 causes the generation function 136 to generate a magnetic resonance image based on data obtained by combining a plurality of magnetic resonance signals.

[0043] 5 and 6, the sequence control circuit 120 acquires multiple magnetic resonance signals twice while changing the relative relationship between the echo and the acquisition window, but the embodiment is not limited to this. The sequence control circuit 120 may acquire multiple magnetic resonance signals while shifting the acquisition window AW24 by 1 / N of the sampling interval, where N is a natural number. This allows the sequence control circuit 120 to acquire multiple magnetic resonance signals while widening the bandwidth of the magnetic resonance signal acquisition by N times compared to when the magnetic resonance signals are acquired only once.

[0044] As described above, in the first embodiment, the sequence control circuit 120 acquires a plurality of magnetic resonance signals while changing the relative relationship between the echo and the acquisition window AW by shifting the acquisition window AW. This effectively increases the sampling rate and shortens the sampling interval, thereby increasing the bandwidth and enabling imaging over a wider FOV.

[0045] (Second embodiment) In the first embodiment, a case has been described in which the sequence control circuit 120 acquires multiple magnetic resonance signals while changing the relative relationship between the echo and the acquisition window by shifting the acquisition window by a width smaller than the sampling interval. In the second embodiment, a case will be described in which the relative relationship between the echo and the acquisition window is changed by shifting the application timing of a 180-degree pulse by a width smaller than the sampling interval in a spin echo pulse sequence. Fig. 7 is a flowchart illustrating the flow of processing performed by the magnetic resonance imaging apparatus 00 according to the second embodiment.

[0046] First, in step S100B, the sequence control circuit 120 acquires a plurality of magnetic resonance signals while changing the relative relationship between the echo and the acquisition window AW. In the second embodiment, the sequence control circuit 120 executes a pulse sequence that generates a spin echo, and acquires the plurality of magnetic resonance signals while changing the relative relationship between the echo and the acquisition window AW by shifting the application timing of a 180-degree pulse in the pulse sequence by an amount smaller than the sampling interval.

[0047] Such an example is shown in FIG. 8. In step S100B, the first pulse sequence 10a executed by the sequence control circuit 120 is composed of a 90-degree pulse 20, a 180-degree pulse 21a, and an acquisition window AW23. When TE22 has elapsed since the application of the 90-degree pulse 20, an echo 25a is generated. The second pulse sequence 10b executed by the sequence control circuit 120 is composed of a 90-degree pulse 20, a 180-degree pulse 21b, and an acquisition window AW23. When TE has elapsed since the application of the 90-degree pulse 20, an echo 25b is generated. Here, the sequence control circuit 120 shifts the application timing of the 180-degree pulse 21b from the application timing of the 180-degree pulse 21a by a period 30 corresponding to half the sampling interval SR. Due to the shift in application timing between the 180-degree pulses 21a and 21b, a shift 31 also occurs between the time when the echo 25a and the echo 25b are generated. As a result, the sequence control circuit 120 acquires a plurality of magnetic resonance signals while changing the relative relationship between the echo and the acquisition window.

[0048] Returning to FIG. 7, in step S200, the processing circuitry 150 causes the generation function 136 to generate a magnetic resonance image based on data obtained by combining a plurality of magnetic resonance signals.

[0049] 7, the sequence control circuit 120 acquires multiple magnetic resonance signals in two separate acquisitions while changing the relative relationship between the echo and the acquisition window, but the embodiment is not limited to this. The sequence control circuit 120 may acquire multiple magnetic resonance signals while shifting the application timing of the 180-degree pulse by 1 / N of the sampling interval, where N is a natural number. This allows the sequence control circuit 120 to acquire multiple magnetic resonance signals while widening the acquisition bandwidth of the magnetic resonance signals by N times compared to when the magnetic resonance signals are acquired only once.

[0050] As described above, in the second embodiment, the sequence control circuit 120 acquires a plurality of magnetic resonance signals while changing the relative relationship between the echo and the acquisition window AW by shifting the application timing of the 180-degree pulse by an amount smaller than the sampling interval SR. As a result, as in the first embodiment, the sampling rate can be effectively increased and the sampling interval can be effectively shortened, which increases the bandwidth and enables imaging of a wider FOV.

[0051] In the first embodiment, the sequence control circuit 120 shifts the acquisition window by a width smaller than the sampling interval to acquire multiple magnetic resonance signals while changing the relative relationship between the echo and the acquisition window, while in the second embodiment, the sequence control circuit 120 shifts the application timing of a 180-degree pulse by a width smaller than the sampling interval to change the relative relationship between the echo and the acquisition window in a spin echo pulse sequence. However, it is also possible to combine these two embodiments.

[0052] That is, the sequence control circuit 120 may shift the acquisition window by a width smaller than the sampling interval, and further shift the application timing of the 180-degree pulse in the pulse sequence by a width smaller than the sampling interval, thereby acquiring multiple magnetic resonance signals while changing the relative relationship between the echo and the acquisition window. As an example, the sequence control circuit 120 performs acquisition by shifting the acquisition window AW by ¼ of the sampling interval SR, and shifting the application timing of the 180-degree pulse by ¼ of the sampling interval SR. In this way, by shifting both the acquisition window AW and the application timing of the 180-degree pulse, the sampling interval can be effectively shortened while keeping the shift amounts of the acquisition window AW and the application timing of the 180-degree pulse small.

[0053] (Third embodiment) In the first and second embodiments, the case where the sequence control circuit 120 executes a single-echo pulse sequence has been described. However, the embodiments are not limited to this, and the sequence control circuit 120 may execute a multi-echo pulse sequence.

[0054] 9 shows an example of a pulse sequence in which multiple magnetic resonance signals are generated by shifting the acquisition window AW by a width smaller than the sampling interval. Pulse sequence 10 illustrates the configuration of one of the pulse sequences executed multiple times. Pulse sequence 10 is a pulse sequence in which multiple 180-degree pulses, i.e., 180-degree pulses 40a, 40b, 40c, and 40d, are applied to one 90-degree pulse 20, and is a multi-echo pulse sequence in which multiple echoes, i.e., echoes 50a, 50b, 50c, and 50d, are generated accordingly. Acquisition windows AW51a, 51b, 51c, and 51d are acquisition windows corresponding to these echoes.

[0055] In step S100A, the sequence control circuit 120 executes multiple pulse sequences while simultaneously shifting the acquisition windows AW51a, 51b, 51c, and 51d in each pulse sequence by a period 52 shorter than the sampling interval SR. As an example, the sequence control circuit 120 executes N pulse sequences while simultaneously shifting the acquisition windows AW51a, 51b, 51c, and 51d in each pulse sequence by a period 52 that is 1 / N of the sampling interval SR. As a result, the sequence control circuit 120 collects multiple magnetic resonance signals while changing the relative relationship between the echo and the acquisition window. In step S200, the processing circuitry 150 generates a magnetic resonance image using the generation function 136 based on data obtained by combining the multiple magnetic resonance signals.

[0056] 10 shows an example of a sequence in which multiple magnetic resonance signals are generated by shifting the application timing of 180-degree pulses by a width smaller than the sampling interval SR. Similar to FIG. 9, pulse sequence 10 illustrates the configuration of one of the pulse sequences executed multiple times. Pulse sequence 10 is a pulse sequence in which multiple 180-degree pulses, i.e., 180-degree pulses 41a, 41b, 41c, and 41d, are applied to a single 90-degree pulse 20, and is a multi-echo pulse sequence in which multiple echoes, i.e., echoes 60a, 60b, 60c, and 60d, are generated accordingly. Acquisition windows AW51a, 51b, 51c, and 51d correspond to these echoes.

[0057] In step S100A, the sequence control circuit 120 executes multiple pulse sequences while simultaneously shifting the application timing of the 180-degree pulse in each pulse sequence by a period 53 shorter than the sampling interval SR. As an example, the sequence control circuit 120 executes N pulse sequences while simultaneously shifting the application timing of the 180-degree pulse in each pulse sequence by a period 53 that is 1 / N of the sampling interval SR. By shifting the application timing of the 180-degree pulse by the period 53, the timing of the generated echo is shifted by a period 54. In this way, the sequence control circuit 120 acquires multiple magnetic resonance signals while changing the relative relationship between the echo and the acquisition window AW. In step S200, the processing circuitry 150 generates a magnetic resonance image using the generation function 136 based on data obtained by combining the multiple magnetic resonance signals.

[0058] 9 and 10, a case has been described in which the relative relationship between the echo and the acquisition window AW does not change within one pulse sequence, but the embodiment is not limited to this. The sequence control circuit 120 may generate multiple magnetic resonance signals while changing the relative relationship between the echo and the acquisition window AW for each echo constituting the multi-echo.

[0059] Such an example is shown in Fig. 11. In the example of Fig. 11, the relative relationship between the echoes and the acquisition window AW changes within one pulse sequence 70. The pulse sequence 70 is a pulse sequence in which multiple 180-degree pulses 40a, 40b, and 40c are applied to one 90-degree pulse 20, and is a multi-echo pulse sequence in which multiple echoes 50a, 50b, and 50c are generated accordingly. Furthermore, acquisition windows AW70, 71, and 72 are acquisition windows corresponding to these echoes.

[0060] In step S100A, the sequence control circuit 120 executes the pulse sequence 70 while shifting the acquisition windows AW71 and AW72 from the acquisition window AW by periods 81 and 82 shorter than the sampling interval SR. As a result, the positions in k-space where data is acquired in the acquisition windows AW71 and AW72 are shifted from the positions in k-space where data is acquired in the acquisition window AW70. As an example, if the data points of the k-space data acquired in the acquisition window AW70 are points 74a, 74b, and 74c, the data points of the k-space data acquired in the acquisition window AW71 are points 73a, 73b, and 73c, and the data points of the k-space data acquired in the acquisition window AW72 are points 75a, 75b, and 75c. The processing circuitry 150 can generate a magnetic resonance image based on data obtained by combining these magnetic resonance signals using the generation function 136.

[0061] As described above, in the third embodiment, a case where a multi-echo pulse sequence is executed has been described. As a result, even in the multi-echo pulse sequence, the sampling rate can be effectively extended and the sampling interval can be effectively shortened, so that the bandwidth becomes larger and imaging can be performed over a wider FOV.

[0062] (Fourth embodiment) In the fourth embodiment, a case will be described in which, in a field echo pulse sequence, the sequence control circuit 120 changes the relative positional relationship between the echo and the acquisition window by shifting the application timing of the readout gradient magnetic field by a width smaller than the sampling interval.

[0063] 12 shows an example in which the relative position change between the echo and the acquisition window AW is changed by shifting the application timing of the readout gradient magnetic field when the pulse sequence executed by the sequence control circuit 120 is a field echo (FE) pulse sequence. In step S100A, the first pulse sequence 90a executed by the sequence control circuit 120 is composed of an α-degree pulse 91 and an acquisition window AW95a. When TE22 has elapsed since the application of the α-degree pulse 91, an echo 94a is generated due to the influence of readout gradient magnetic fields 92a and 92b. The second pulse sequence 90b executed by the sequence control circuit 120 is composed of an α-degree pulse 91 and an acquisition window AW95b. An echo 94b is generated due to the influence of readout gradient magnetic fields 93a and 93b. Here, the sequence control circuit 120 acquires multiple magnetic resonance signals while changing the relative relationship between the echo and the acquisition window AW by shifting the application timing of the readout gradient magnetic field 93b by an amount smaller than the sampling interval. In step S200, the processing circuitry 150 causes the generation function 136 to generate a magnetic resonance image based on data obtained by combining a plurality of magnetic resonance signals.

[0064] 12, for simplicity, the readout gradient magnetic field 93b is depicted as rising straight up, but the waveform of the actual readout gradient magnetic field 93b may have rounding or overshoot. That is, in the embodiment, shifting the application timing of the readout gradient magnetic field 93b does not necessarily mean changing the rising timing of the gradient magnetic field 93b. The time of the center of the echo 94b is determined by the integral of the readout gradient magnetic fields 93a and 93b applied up to that point. The echo 94b is generated when the integral of the negative intensity of the readout gradient magnetic field 93a is equal to the integral of the positive intensity of the readout gradient magnetic field 93b. Therefore, the sequence control circuit 120 actually controls the time of the echo 94b by controlling not only the rising time of the readout gradient magnetic field 93b but also the entire waveforms of the readout gradient magnetic field 93a and the readout gradient magnetic field 93b.

[0065] As described above, in the fourth embodiment, the case where the application timing of the readout gradient magnetic field is controlled has been described. By controlling the application timing of the readout gradient magnetic field, the sampling rate can also be effectively increased.

[0066] In the fourth embodiment, the sampling rate is effectively increased by controlling the timing of application of the readout gradient magnetic field. However, the fourth embodiment can be combined with the first and second embodiments, and the sampling rate can be effectively increased by further controlling, for example, the collection window or the timing of application of the 180-degree pulse.

[0067] According to at least one of the embodiments described above, data can be collected with an increased effective sampling rate.

[0068] Although several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations of embodiments can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0069] 120 Sequence control circuit 130 Computers 132 memory 134 Input Device 135 Display

Claims

1. a sequence control unit that acquires a plurality of magnetic resonance signals while changing the relative relationship between the echo and the acquisition window; a generating unit that generates a magnetic resonance image based on data obtained by combining the plurality of magnetic resonance signals.

2. The magnetic resonance imaging apparatus according to claim 1 , wherein the sequence control unit acquires the plurality of magnetic resonance signals while changing the relative relationship by shifting an acquisition window by a width smaller than a sampling interval.

3. The magnetic resonance imaging apparatus according to claim 2 , wherein the sequence control unit executes a spin echo or field echo pulse sequence.

4. 3. The magnetic resonance imaging apparatus according to claim 2, wherein the sequence control unit acquires the plurality of magnetic resonance signals while shifting an acquisition window by 1 / N of a sampling interval, where N is a natural number, thereby acquiring the plurality of magnetic resonance signals while widening a bandwidth of acquisition of the magnetic resonance signals by N times compared to a case where the magnetic resonance signals are acquired only once.

5. the sequence controller executes a pulse sequence for generating a spin echo; 2. The magnetic resonance imaging apparatus according to claim 1, wherein the application timing of the 180-degree pulse in the pulse sequence is shifted by an amount smaller than a sampling interval, thereby acquiring the plurality of magnetic resonance signals while changing the relative relationship.

6. 6. The magnetic resonance imaging apparatus according to claim 5, wherein the sequence control unit acquires the plurality of magnetic resonance signals while shifting the application timing of the 180-degree pulse by 1 / N of a sampling interval, where N is a natural number, thereby widening the bandwidth of the acquisition of magnetic resonance signals by N times compared to when the acquisition of magnetic resonance signals is performed only once.

7. 6. The magnetic resonance imaging apparatus according to claim 5, wherein the sequence control unit further shifts an acquisition window by a width smaller than the sampling interval, thereby acquiring the plurality of magnetic resonance signals while changing the relative relationship.

8. 2. The magnetic resonance imaging apparatus according to claim 1, wherein the sequence control unit acquires the plurality of magnetic resonance signals while changing the relative relationship by shifting the application timing of a readout gradient magnetic field by an amount smaller than a sampling interval.

9. The magnetic resonance imaging apparatus according to claim 1 , wherein the sequence control unit executes a multi-echo pulse sequence.

10. The magnetic resonance imaging apparatus according to claim 9 , wherein the sequence control unit generates the plurality of magnetic resonance signals while changing the relative relationship for each echo constituting the multi-echo.

11. A magnetic resonance imaging method comprising acquiring a plurality of magnetic resonance signals while varying the relative relationship between an echo and an acquisition window, and generating a magnetic resonance image based on data obtained by combining the plurality of magnetic resonance signals.

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