Magnetic resonance imaging device

Abstract

The magnetic resonance imaging apparatus of the embodiment comprises a static magnetic field generating unit, a transceiver system and a collecting unit. The static magnetic field generating unit applies a second static magnetic field in addition to a first static magnetic field serving as a reference. The transceiver system performs transceiver transmission and reception at a single frequency. The collecting unit uses the transceiver system to collect magnetic resonance signals. The transceiver system performs transceiver transmission and reception at the resonance frequency of hydrogen nuclei when the first static magnetic field is applied, and performs transceiver transmission and reception at the resonance frequency of a nuclide different from the hydrogen nuclei when the second static magnetic field is applied in addition to the first static magnetic field.

Description

[0001] Reference to related applications

[0002] This application enjoys the benefit of priority of Japanese patent application No. 2019-201228 filed on November 6, 2019, and the entire contents of the Japanese patent application are cited in this application. Technical Field

[0003] Embodiments relate to magnetic resonance imaging apparatus. Background Art

[0004] Magnetic resonance imaging (MRI) is a device that uses the magnetic resonance phenomenon to visualize the chemical and physical microscopic information of a substance. Here, the magnetic resonance phenomenon refers to the phenomenon that when a group of spins of a target atomic nucleus is placed in a static magnetic field, it resonates with a high-frequency magnetic field rotating at a specific frequency (hereinafter referred to as the resonance frequency) that matches the inherent magnetic moment of the atomic nucleus and the strength of the static magnetic field, and a signal is generated in the relaxation process.

[0005] In such MRI devices, hydrogen nuclei (protons) are usually used to measure the 1 H is used as the subject for shooting, but it is also known to be 1 H is a technique for taking images of different nuclides. Summary of the invention

[0006] The technical problem to be solved by the present invention is to use hydrogen nuclei respectively 1 H and 1 H takes high-quality photos of different nuclides.

[0007] The MRI device of the embodiment comprises a static magnetic field generating unit, a transceiver system and a collecting unit. The static magnetic field generating unit applies a second static magnetic field in addition to a first static magnetic field serving as a reference. The transceiver system performs transceiver transmission and reception at a single frequency. The collecting unit uses the transceiver system to collect magnetic resonance signals. The transceiver system performs transceiver transmission and reception at the resonance frequency of hydrogen nuclei when the first static magnetic field is applied, and performs transceiver transmission and reception at the resonance frequency of a nuclide different from the hydrogen nuclei when the second static magnetic field is applied in addition to the first static magnetic field.

[0008] Effect

[0009] According to the magnetic resonance imaging apparatus of the embodiment, it is possible to convert hydrogen nuclei into 1 H and 1 H Different nuclides are taken as objects and photographed with high quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a diagram showing a configuration example of the MRI apparatus according to the first embodiment.

[0011] Figure 2 This is a flowchart showing the flow of imaging performed by the MRI apparatus according to the first embodiment.

[0012] Figure 3 This is a flowchart showing the flow of imaging performed by the MRI apparatus according to the second embodiment.

[0013] Figure 4 It is a diagram showing a configuration example of an MRI apparatus according to a fifth embodiment. DETAILED DESCRIPTION

[0014] Hereinafter, embodiments of the MRI apparatus of the present application will be described in detail with reference to the accompanying drawings.

[0015] (First Embodiment)

[0016] Figure 1 It is a diagram showing a configuration example of the MRI apparatus according to the first embodiment.

[0017] For example, Figure 1 As shown, the MRI apparatus 100 of the present embodiment includes a first static magnetic field magnet 1, a gradient magnetic field coil 2, a gradient magnetic field power supply 3, a whole-body RF (Radio Frequency) coil 4, a local RF coil 5, a transmitting circuit 6, a receiving circuit 7, a gantry 8, a diagnostic bed 9, an interface 10, a display 11, a storage circuit 12, processing circuits 13 to 16, a second static magnetic field magnet 17, and a static magnetic field power supply 18.

[0018] The first static magnetic field magnet 1 generates a static magnetic field in the imaging space where the subject S is arranged. Specifically, the first static magnetic field magnet 1 is formed into a hollow substantially cylindrical shape (including the case where the shape of the cross section perpendicular to the central axis is an elliptical shape), and generates a static magnetic field in the imaging space formed on the inner circumference thereof. For example, the first static magnetic field magnet 1 is a superconducting magnet, a permanent magnet, or the like.

[0019] The gradient magnetic field coil 2 is arranged on the inner side of the first static magnetic field magnet 1, and generates a gradient magnetic field in the imaging space where the subject S is arranged. Specifically, the gradient magnetic field coil 2 is formed into a hollow, roughly cylindrical shape (including the case where the shape of the cross section orthogonal to the central axis is an ellipse), and has an X-coil, a Y-coil, and a Z-coil corresponding to the mutually orthogonal X-axis, Y-axis, and Z-axis, respectively. The X-coil, the Y-coil, and the Z-coil generate a gradient magnetic field that changes linearly along the directions of each axis in the imaging space based on the current supplied from the gradient magnetic field power supply 3. Here, the Z-axis is set to be along the magnetic flux of the static magnetic field generated by the first static magnetic field magnet 1. In addition, the X-axis is set to be along the horizontal direction orthogonal to the Z-axis, and the Y-axis is set to be along the vertical direction orthogonal to the Z-axis. Thus, the X-axis, the Y-axis, and the Z-axis constitute a device coordinate system inherent to the MRI device 100.

[0020] The gradient magnetic field power supply 3 generates a gradient magnetic field in the imaging space by supplying current to the gradient magnetic field coil 2. Specifically, the gradient magnetic field power supply 3 supplies current to the X coil, Y coil, and Z coil of the gradient magnetic field coil 2, respectively, thereby generating a gradient magnetic field that changes linearly along the mutually orthogonal readout direction, phase encoding direction, and slice direction in the imaging space. In addition, hereinafter, the gradient magnetic field along the readout direction is referred to as the readout gradient magnetic field, the gradient magnetic field along the phase encoding direction is referred to as the phase encoding gradient magnetic field, and the gradient magnetic field along the slice direction is referred to as the slice gradient magnetic field.

[0021] Here, the extraction gradient magnetic field, the phase encoding gradient magnetic field, and the slice gradient magnetic field are respectively superimposed on the static magnetic field generated by the first static magnetic field magnet 1, thereby giving spatial position information to the magnetic resonance signal generated from the subject S. Specifically, the extraction gradient magnetic field changes the frequency of the magnetic resonance signal according to the position of the extraction direction, thereby giving the magnetic resonance signal position information along the extraction direction. In addition, the phase encoding gradient magnetic field changes the phase of the magnetic resonance signal along the phase encoding direction, thereby giving the magnetic resonance signal position information along the phase encoding direction. In addition, the slice gradient magnetic field gives the magnetic resonance signal position information along the slice direction. For example, when the imaging region is a slice region (2D imaging). The slice gradient magnetic field is used to determine the direction, thickness, and number of slice regions, and when the imaging region is a body region (3D imaging), the slice gradient magnetic field is used to change the phase of the magnetic resonance signal according to the position of the slice direction. Thus, the axis along the extraction direction, the axis along the phase encoding direction, and the axis along the slice direction constitute a logical coordinate system for defining the slice region or body region to be imaged.

[0022] The whole-body RF coil 4 is arranged on the inner circumference side of the gradient magnetic field coil 2, transmits a high-frequency magnetic field to the subject S arranged in the imaging space, and receives a magnetic resonance signal generated from the subject S due to the influence of the high-frequency magnetic field. Specifically, the whole-body RF coil 4 is formed into a hollow substantially cylindrical shape (including a case where the shape of the cross section orthogonal to the central axis is an ellipse), and transmits a high-frequency magnetic field to the subject S arranged in the imaging space located on the inner circumference side thereof based on a high-frequency pulse signal supplied from the transmission circuit 6. In addition, the whole-body RF coil 4 receives a magnetic resonance signal generated from the subject S due to the influence of the high-frequency magnetic field, and outputs the received magnetic resonance signal to the reception circuit 7.

[0023] The local RF coil 5 receives magnetic resonance signals generated from the subject S. Specifically, a plurality of local RF coils 5 are prepared so as to be applicable to various parts of the subject S, and when the subject S is photographed, the local RF coil 5 is arranged near the surface of the part of the photographed object. Moreover, the local RF coil 5 receives magnetic resonance signals generated from the subject S due to the influence of the high-frequency magnetic field transmitted by the whole-body RF coil 4, and outputs the received magnetic resonance signals to the receiving circuit 7. In addition, the local RF coil 5 may also have a function of transmitting a high-frequency magnetic field to the subject S. In this case, the local RF coil 5 is connected to the transmitting circuit 6, and transmits a high-frequency magnetic field to the subject S based on a high-frequency pulse (plus) signal supplied from the transmitting circuit 6. For example, the local RF coil 5 is a surface coil (surface coil) or a phased array coil (phased array coil) composed of a plurality of surface coils as elements (element).

[0024] The transmission circuit 6 outputs a high-frequency pulse signal corresponding to the resonance frequency (also called Larmor frequency) inherent to the target nucleus placed in the static magnetic field to the whole-body RF coil 4. Specifically, the transmission circuit 6 includes a pulse generator, a high-frequency generator, a modulator, and an amplifier. The pulse generator generates a waveform of a high-frequency pulse signal. The high-frequency generator generates a high-frequency signal of a resonance frequency. The modulator modulates the amplitude of the high-frequency signal generated by the high-frequency generator using the waveform generated by the pulse generator, thereby generating a high-frequency pulse signal. The amplifier amplifies the high-frequency pulse signal generated by the modulator and outputs it to the whole-body RF coil 4.

[0025] The receiving circuit 7 generates magnetic resonance data (data) based on the magnetic resonance signal output from the whole body RF coil 4 or the local RF coil 5, and outputs the generated magnetic resonance data to the processing circuit 14. For example, the receiving circuit 7 includes a selector, a preamplifier, a phase detector, and an A / D (Analog / Digital) converter. The selector selectively inputs the magnetic resonance signal output from the whole body RF coil 4 or the local RF coil 5. The preamplifier performs power amplification on the magnetic resonance signal output from the selector. The phase detector detects the phase of the magnetic resonance signal output from the preamplifier. The A / D converter converts the analog signal output from the phase detector into a digital signal, thereby generating magnetic resonance data, and outputs the generated magnetic resonance data to the processing circuit 14. In addition, each process described here as the process performed by the receiving circuit 7 does not necessarily need to be fully processed by the receiving circuit 7, and a part of the process (for example, the process by the A / D converter, etc.) may be performed by the whole body RF coil 4 and the local RF coil 5.

[0026] The gantry 8 has a hollow bore 8a formed in a substantially cylindrical shape (including a case where the shape of the cross section perpendicular to the central axis is an ellipse), and accommodates the first static magnetic field magnet 1, the gradient magnetic field coil 2, and the whole body RF coil 4. Specifically, the gantry 8 arranges the whole body RF coil 4 on the outer peripheral side of the bore 8a, arranges the gradient magnetic field coil 2 on the outer peripheral side of the whole body RF coil 4, and arranges the first static magnetic field magnet 1 on the outer peripheral side of the gradient magnetic field coil 2, and accommodates the first static magnetic field magnet 1, the gradient magnetic field coil 2, and the whole body RF coil 4. Here, the space in the bore 8a of the gantry 8 becomes an imaging space where the subject S is arranged during imaging.

[0027] The diagnostic bed 9 has a top plate 9a on which the subject S is placed and a moving mechanism that moves the top plate 9a in the up-down direction and the horizontal direction. Here, the up-down direction is the vertical direction, and the horizontal direction is the direction along the central axis of the first static magnetic field magnet 1. With such a structure, the diagnostic bed 9 can change the height of the top plate 9a by moving the top plate 9a in the up-down direction. In addition, the diagnostic bed 9 can change the position of the top plate 9a between the space outside the gantry 8 and the imaging space in the hole 8a located inside the gantry 8 by moving the top plate 9a in the horizontal direction.

[0028] The interface 10 receives input operations of various instructions and various information from the operator. Specifically, the interface 10 is connected to the processing circuit 16, converts the input operation received from the operator into an electrical signal and outputs it to the processing circuit 16. For example, the interface 10 is implemented by a trackball, a switch button, a mouse, a keyboard, a touch-pad for performing input operations by contacting the operation surface, a touch-screen in which a display screen and a touch-pad are integrated, a non-contact input circuit using an optical sensor, and a sound input circuit. In addition, in this specification, the interface 10 is not limited to an interface including physical operating components such as a mouse and a keyboard. For example, a processing circuit for receiving an electrical signal corresponding to an input operation from an external input device that is separate from the device and outputting the electrical signal to a control circuit is also included in the example of the interface 10.

[0029] The display 11 displays various information and various images. Specifically, the display 11 is connected to the processing circuit 16, and converts the various information and various image data sent from the processing circuit 16 into electrical signals for display and outputs them. For example, the display 11 is implemented by a liquid crystal monitor (monitor), a CRT (Cathode RayTube: cathode ray tube) monitor, a touch panel (touch panel), etc.

[0030] The storage circuit 12 stores various data. Specifically, the storage circuit 12 stores magnetic resonance data and image data. For example, the storage circuit 12 is implemented by a semiconductor memory element such as RAM (Random Access Memory) or flash memory, a hard disk, or an optical disk.

[0031] The processing circuit 13 has a bed control function 13a. The bed control function 13a controls the movement of the bed 9 by outputting an electrical signal for control to the bed 9. For example, the bed control function 13a receives an instruction from the operator to move the top plate 9a in the vertical direction or in the horizontal direction via the interface 10 or the operation panel provided on the gantry 8, and operates the moving mechanism of the bed 9 in accordance with the received instruction to move the top plate 9a. For example, when photographing the subject S, the bed control function 13a moves the top plate 9a on which the subject S is placed to the photographing space in the hole 8a located on the inner side of the gantry 8.

[0032] The processing circuit 14 has a collection function 14a. The collection function 14a collects magnetic resonance data of the subject S by executing various pulse sequences. Specifically, the collection function 14a drives the gradient magnetic field power supply 3, the transmission circuit 6, and the receiving circuit 7 according to the sequence execution data output from the processing circuit 16, thereby executing various pulse sequences. Here, the sequence execution data is data indicating the pulse sequence, and is information that specifies the timing (timing) of the gradient magnetic field power supply 3 supplying current to the gradient magnetic field coil 2 and the intensity of the supplied current, the timing of the transmission circuit 6 supplying high-frequency pulse signals to the whole-body RF coil 4 and the intensity of the supplied high-frequency pulses, the timing of the receiving circuit 7 sampling the magnetic resonance signals, and the like. In addition, the collection function 14a receives the magnetic resonance data output from the receiving circuit 7 as a result of executing the pulse sequence, and stores it in the storage circuit 12. At this time, the magnetic resonance data stored in the storage circuit 12 is stored as data representing two-dimensional or three-dimensional k-space by being given position information along the extraction direction, phase output direction and slice direction by the above-mentioned extraction gradient magnetic field, phase encoding gradient magnetic field and slice gradient magnetic field.

[0033] The processing circuit 15 has an image generation function 15a. The image generation function 15a generates various images based on the magnetic resonance data collected by the processing circuit 14. Specifically, the image generation function 15a reads the magnetic resonance data collected by the processing circuit 14 from the storage circuit 12, and performs reconstruction processing such as Fourier transform on the read magnetic resonance data, thereby generating a two-dimensional or three-dimensional image. Then, the image generation function 15a stores the generated image in the storage circuit 12.

[0034] The processing circuit 16 has an imaging control function 16a. The imaging control function 16a controls the entire MRI device 100 by controlling the various components of the MRI device 100. Specifically, the imaging control function 16a displays a GUI (Graphical User Interface) for accepting input operations of various instructions and various information from the operator on the display 11, and controls the various components of the MRI device 100 according to the input operations accepted via the interface 10. For example, the imaging control function 16a generates sequence execution data based on the imaging conditions input by the operator, and outputs the generated sequence execution data to the processing circuit 14, thereby collecting magnetic resonance data. In addition, for example, the imaging control function 16a generates an image based on the magnetic resonance data collected by the processing circuit 14 by controlling the processing circuit 15. In addition, for example, the imaging control function 16a reads out an image stored in the storage circuit 12 according to a request from the operator, and displays the read image on the display 11.

[0035] Here, each of the above-mentioned processing circuits is implemented by, for example, a processor. In this case, the processing functions of each processing circuit are stored in the storage circuit 12 in the form of a program that can be executed by a computer. And each processing circuit reads out each program from the storage circuit 12 and executes it, thereby implementing the processing function corresponding to each program. In other words, each processing circuit that reads out the status of each program has Figure 1 The functions shown in each processing circuit.

[0036] In addition, here, it is described that each processor is implemented by a single processor, but the implementation is not limited to this. For example, multiple independent processors can also be combined to form each processing circuit, and each processor implements each processing function by executing a program. In addition, the processing functions of each processing circuit can also be appropriately dispersed or combined in a single or multiple processing circuits. Figure 1 In the example shown, a single storage circuit 12 stores programs corresponding to respective processing functions. However, a configuration may be adopted in which a plurality of storage circuits are dispersedly arranged and the processing circuits read corresponding programs from independent storage circuits.

[0037] The overall structure of the MRI apparatus 100 of this embodiment has been described above. Based on this structure, the MRI apparatus 100 of this embodiment can detect hydrogen nuclei. 1 H and 1 H Different nuclides are imaged as targets.

[0038] Here, the atomic nuclei have different resonance frequencies for each nuclide according to the difference in their respective nuclear magnetic rotation ratios. Therefore, when multiple nuclides are taken as the object for imaging, for example, the following methods are considered: a dedicated transceiver system is provided for each nuclide, the transceiver system is configured to be capable of transmitting and receiving at multiple resonance frequencies (DualTune), the frequency band of the transceiver system is set to a wide band, and a dedicated RF coil matching the nuclide of the object is changed at each imaging.

[0039] However, in these methods, the quality of the image obtained by shooting may be reduced. For example, when a dedicated transceiver system is provided for each nuclide, or when the transceiver system is configured to be able to transmit and receive at multiple resonance frequencies, 1In the structure of the object H, unnecessary circuits and components are added to the transceiver system, so the electrical noise increases, and the image quality may be reduced. In addition, for example, when the frequency band of the transceiver system is set to a wide band, more noise is detected in the amount of the widened frequency band, and the image quality may be reduced. In addition, for example, when the RF coil is changed to a dedicated one matching the target nuclide every time the image is taken, the subject may move while the RF coil is being changed, and the image of another nuclide may be superimposed on the object. 1 When evaluating the images of H, the image quality of the superimposed image may be degraded due to the positional shift between the images.

[0040] Thus, the MRI apparatus 100 of this embodiment is configured to be able to 1 H and 1 H Different nuclides are taken as objects and photographed with high quality.

[0041] Specifically, the MRI apparatus 100 includes: a static magnetic field generating unit that applies a second static magnetic field in addition to a first static magnetic field that serves as a reference; a transceiver system that performs transceiver transmission at a single frequency; and a collection unit that uses the transceiver system to collect magnetic resonance signals. 1 H resonant frequency, and in a state where a second static magnetic field is applied in addition to the first static magnetic field, 1 H transmits and receives the resonance frequencies of different nuclides.

[0042] In this embodiment, the static magnetic field generating unit is implemented by the first static magnetic field magnet 1, the second static magnetic field magnet 17, and the static magnetic field power supply 18. In addition, the transceiver system is implemented by the above-mentioned whole body RF coil 4, local RF coil 5, transmission circuit 6, and reception circuit 7. In addition, the collection unit is implemented by the collection function 14a of the above-mentioned processing circuit 14.

[0043] The first static magnetic field magnet 1 generates a first static magnetic field of a constant magnitude serving as a reference in the imaging space.

[0044] The second static magnetic field magnet 17 generates a second static magnetic field of a constant magnitude corresponding to the nuclide to be imaged in the static magnetic field space by the current supplied from the static magnetic field power supply 18. Specifically, the second static magnetic field magnet 17 is an electromagnet realized by a coil or the like formed into a hollow substantially cylindrical shape, and is arranged in a manner that the magnetic field center of the first static magnetic field is built-in.

[0045] The static magnetic field power supply 18 supplies a current for causing the second static magnetic field magnet 17 to generate a second static magnetic field under the control of the collecting function 14 a .

[0046] The collection function 14 a collects magnetic resonance signals by controlling the static magnetic field generating unit and the transceiver system.

[0047] Specifically, the collection function 14a is when the object being photographed is 1 In the case of H, the static magnetic field power supply 18 is controlled so that no current is supplied to the second static magnetic field magnet 17, thereby achieving a state where only the first static magnetic field is applied. In this case, the magnitude of the second static magnetic field is zero. In addition, when the object to be photographed is 1 In the case of a nuclide of a different type, the static magnetic field power supply 18 is controlled so as to supply current to the second static magnetic field magnet 17, thereby applying the second static magnetic field in addition to the first static magnetic field. In this case, the magnitude of the second static magnetic field becomes a constant magnitude corresponding to the nuclide to be imaged.

[0048] In addition, the collection function 14a controls the transceiver system according to the nuclide as the imaging object. 1 The transceiver system transmits and receives at a first frequency that matches the resonance frequency of H. Furthermore, the transceiver system transmits and receives at the first frequency when the first static magnetic field is applied, and transmits and receives at the first frequency when the second static magnetic field is applied in addition to the first static magnetic field. 1 H transmits and receives in a state where the resonance frequency of the different nuclides matches the first frequency.

[0049] Here, the size of the second static magnetic field and the first frequency are set according to the size of the first static magnetic field and the nuclide that is the object of the shooting. In addition, the direction of the second static magnetic field can be the same as the direction of the first static magnetic field, or it can be the opposite direction. When the direction of the second static magnetic field is the same as the direction of the first static magnetic field, the size of the static magnetic field applied during shooting becomes larger, and when the direction of the second static magnetic field is opposite to the direction of the first static magnetic field, the size of the static magnetic field applied to the shooting space becomes smaller.

[0050] For example, suppose the magnitude of the first static magnetic field is 1.5 T (Tesla), and the nuclides to be imaged are 1 H and 19 F.

[0051] Here, in a static magnetic field of 1.5T, 1 The resonant frequency of H is about 64MHz. 19 The resonant frequency of F is about 60MHz. Therefore, for example, when the frequency of transmission and reception is set to 64MHz, it is possible to collect 1 H magnetic resonance signal, but it is not possible to collect 19 F magnetic resonance signal. In contrast, in a static magnetic field of 1.6 T, 19The resonant frequency of F is about 64MHz, which is consistent with the static magnetic field of 1.5T. 1 The resonant frequencies of H are roughly the same.

[0052] Therefore, for example, when the magnitude of the first static magnetic field is 1.5 T and the nuclide to be imaged is 1 H and 19 In the case of F, the magnitude of the second static magnetic field is set to 0.1 T, and the first frequency is set to 64 MHz.

[0053] Therefore, in 1 When H is the object to be photographed, the transceiver system transmits and receives at the first frequency in a state where only the first static magnetic field is applied, thereby collecting 1 On the other hand, in 19 When F is the object to be photographed, the transceiver system transmits and receives at the first frequency in a state where the second static magnetic field is applied in addition to the first static magnetic field, thereby being able to collect 19 The magnetic resonance signal of F.

[0054] That is, by switching between a state in which only the first static magnetic field is applied and a state in which the second static magnetic field is applied in addition to the first static magnetic field, it is possible to 1 The resonant frequency of H matches the frequency of a single collector 1 H and 19 F respective magnetic resonance signal.

[0055] Thus, in this embodiment, the transceiver system is applied with the second static magnetic field in addition to the first static magnetic field, and the first static magnetic field and the second static magnetic field are used to generate a signal in the transceiver system. 1 H transmits and receives in a state where the resonance frequency of the different nuclides matches the first frequency.

[0056] Here, with 1 The state in which the resonance frequency of the different nuclear species matches the first frequency refers to a state in which the resonance frequency of the nuclear species matches so as to be included in the frequency band of the transmission and reception system and the frequency band of the image.

[0057] For example, with 1 The resonance frequencies of the different nuclear species are matched so as to be included in the narrowest frequency band among the frequency bands of the whole-body RF coil 4 , the local RF coil 5 , the transmission circuit 6 , the reception circuit 7 , and the image.

[0058] Furthermore, the transceiver system is in contact with the subject 1 H Different nuclides have different spin directions relative to 1 In the case of a nuclide with the opposite H, the phase of the high frequency used for transmission and reception is reversed in the state where the second static magnetic field is applied in addition to the first static magnetic field, so that1 The resonance frequency of the different nuclide H matches the first frequency.

[0059] For example, when the whole-body RF coil 4 is a QD (Quadrature Detection) coil that generates a high-frequency magnetic field by inputting high-frequency currents whose phases are shifted by 90 degrees from each other from two power supply points, the transceiver system inverts the phase (IQ) of the high-frequency current supplied to the whole-body RF coil 4 to make the high-frequency magnetic field 1 The resonance frequency of the different nuclide H matches the first frequency.

[0060] Thus, for example, it is possible to 3 Like He, 129Xe, etc., the direction of spin rotation is relative to 1 The nuclide opposite to H is used as the object for imaging.

[0061] In addition, the transceiver system will be in the state where the second static magnetic field is applied in addition to the first static magnetic field. 1 The receiving gain of the magnetic resonance signal of different nuclides is set to 1 The receiving gain of the magnetic resonance signal of H is large.

[0062] Usually, from 1 The magnetic resonance signals produced by nuclides other than H are similar to those produced by 1 Compared with the magnetic resonance signal generated by H, the signal size becomes smaller, but by adjusting the receiving gain in this way, the sensitivity to 1 H Image quality when shooting with different nuclides.

[0063] Figure 2 This is a flowchart showing the flow of imaging performed by the MRI apparatus according to the first embodiment.

[0064] Here, as in the above example, the magnitude of the first static magnetic field is 1.5 T, and the nuclides to be imaged are 1H and 19 The example of the case of F is described below, where the magnitude of the second static magnetic field is set to 0.1 T and the first frequency is set to 64 MHz.

[0065] For example, Figure 2 As shown, in this embodiment, the imaging control function 16a receives an instruction to start imaging from the operator (step S101, Yes). At this time, for example, the imaging control function 16a receives the instruction to start imaging and receives the designation of a nuclide to be imaged as one of the imaging conditions.

[0066] Here, when the target nuclide is 1If H (step S102, YES), the collection function 14a controls the static magnetic field power supply 18 so as not to supply current to the second static magnetic field magnet 17, thereby achieving a state where only the first static magnetic field is applied (step S103).

[0067] Next, the collection function 14a controls the transceiver system in a manner of transmitting and receiving at the first frequency, thereby collecting 1 Then, the image generation function 15a generates a magnetic resonance signal of H based on the collected magnetic resonance signal. 1 H image (step S105).

[0068] On the other hand, when the target nuclide is 19 F (step S102, No, step S106, Yes), the collection function 14a controls the static magnetic field power supply 18 in a manner to supply current to the second static magnetic field magnet 17, thereby achieving a state where the second static magnetic field is applied in addition to the first static magnetic field (step S107).

[0069] Next, the collection function 14a controls the transceiver system in a manner of transmitting and receiving at the first frequency, thereby collecting 19 Then, the image generation function 15a generates a magnetic resonance signal of F based on the collected magnetic resonance signal. 19 F image (step S109).

[0070] In addition, the nuclide of the object specified by the operator is neither 1 Neither is H 19 In the case of F (step S102, No, step S106, No), the collection function 14a does not collect magnetic resonance signals and ends the processing.

[0071] Here, in the above-mentioned processing procedure, the processing of step S101 is realized, for example, by the processing circuit 16 reading out a prescribed program corresponding to the shooting control function 16a from the storage circuit 12 and executing it. In addition, the processing of steps S102 to S104 and S106 to S108 is realized, for example, by the processing circuit 14 reading out a prescribed program corresponding to the collection function 14a from the storage circuit 12 and executing it. In addition, the processing of steps S105 and S109 is realized, for example, by the processing circuit 15 reading out a prescribed program corresponding to the image generation function 15a from the storage circuit 12 and executing it.

[0072] By executing the above-described processing, the following 1 H and 19 F is the image taken with these two nuclides as the object.

[0073] In addition, here, it is explained that the nuclides to be imaged are 1 H and19 F is an example, but the implementation is not limited to this, and it is also possible to 1 H and 19 In this case, the target nuclide is selected based on the resonance frequency of the target nuclide and the resonance frequency of the first static magnetic field. 1 The magnitude of the second static magnetic field is set so as to be substantially the same as the resonant frequency of H.

[0074] In addition, here, an example of changing the second static magnetic field to two sizes, zero and a certain size corresponding to the nuclide to be imaged, is described, but the embodiment is not limited to this, and it can also be changed to zero and a plurality of sizes other than zero. 1 H and one other nuclide can be used as the target. 1 H and other multiple nuclides are imaged.

[0075] As described above, in the first embodiment, the static magnetic field generating unit applies the second static magnetic field in addition to the first static magnetic field serving as the reference, and the transceiver system performs transceiver transmission and reception at a single frequency. In addition, the collection function 14a uses the transceiver system to collect magnetic resonance signals. In addition, the transceiver system performs transceiver transmission and reception at a single frequency in a state where the first static magnetic field is applied. 1 H resonant frequency, and in a state where a second static magnetic field is applied in addition to the first static magnetic field, 1 H transmits and receives the resonance frequencies of different nuclides.

[0076] According to this structure, 1H and 1 H Different nuclides are taken as objects and photographed with high quality.

[0077] For example, compared with the case where a dedicated transceiver system is provided for each nuclide, or the transceiver system is configured to be capable of transmitting and receiving at a plurality of resonance frequencies, unnecessary circuits and components are not added to the transceiver system, and thus degradation of image quality due to electrical noise can be suppressed. In addition, for example, it is not necessary to set the frequency band of the transceiver system to a wide band, and thus degradation of image quality due to increased detection noise can be prevented. In addition, for example, it is not necessary to change the RF coil for each shot, and thus it is not necessary to prepare a dedicated RF coil for each nuclide, and even when the image of another nuclide is superimposed on the image, the image quality of the nuclide can be reduced. 1 Even when evaluating the images of H, it is possible to prevent degradation in the quality of the superimposed image due to positional shift between the images.

[0078] Compared with the case where a dedicated transceiver system is provided for each nuclide, or the case where the transceiver system is configured to be capable of transmitting and receiving at a plurality of resonance frequencies, the resonant frequency can be used as it is. 1The conventional transmission and reception system for H is used to image multiple nuclides, so it is also advantageous in terms of cost.

[0079] In addition, the above-described embodiment can be implemented in various different forms by modifying a part of the structure of the MRI apparatus 100. Therefore, several modified examples of the above-described embodiment will be described below as other embodiments.

[0080] (Second Embodiment)

[0081] For example, as a second embodiment, the transceiver system may also be configured to include 1 In addition to the first frequency that matches the resonance frequency of H, it is also possible to 1 In this case, the transceiver system performs transmission and reception at any one of the first frequency and the second frequency in a state where the first static magnetic field is applied, and in a state where the second static magnetic field is applied in addition to the first static magnetic field, the first static magnetic field and the second static magnetic field are used to transmit and receive the radio frequency of the radionuclides in the same frequency as the first radionuclides. 1 Transmission and reception are performed in a state where the resonance frequency of the second nuclear species that is different from either H or the first nuclear species matches the first frequency.

[0082] Figure 3 This is a flowchart showing the flow of imaging performed by the MRI apparatus according to the second embodiment.

[0083] Here, as in the above example, the magnitude of the first static magnetic field is 1.5 T and the nuclide to be imaged is 1 H and 19 The example of the case of F is described, the magnitude of the second static magnetic field is set to 0.1T, and the first frequency is set to 64MHz. In addition, here, the transceiver system is configured to be able to use the same frequency as the first frequency in addition to the first frequency. 13 An example of a case where transmission and reception are performed at a second frequency that matches the resonant frequency of C will be described.

[0084] For example, Figure 3 As shown, in this embodiment, the imaging control function 16a receives an instruction to start imaging from the operator (step S101, Yes). At this time, for example, the imaging control function 16a receives the instruction to start imaging and receives the designation of a nuclide to be imaged as one of the imaging conditions.

[0085] Here, the target nuclide is 1 H (step S102, yes) and the processing (steps S103 to S105) when the target nuclide is 19 F (step S102, No, step S106, Yes) processing (steps S107 to S109), respectively Figure 2 The processes of steps S103 to S105 and steps S107 to S109 are the same, and thus their description is omitted here.

[0086] Furthermore, in this embodiment, the target nuclide designated by the operator is neither 1 Neither is H 19 F (step S102, no, step S106, no), but 13 C (step S210, YES), the collection function 14a controls the static magnetic field power supply 18 so as not to supply current to the second static magnetic field magnet 17, thereby achieving a state where only the first static magnetic field is applied (step S211).

[0087] Next, the collection function 14a controls the transceiver system in a manner of transmitting and receiving at the second frequency, thereby collecting 13 Then, the image generation function 15a generates a magnetic resonance signal of C based on the collected magnetic resonance signal. 13 C's image (step S213).

[0088] In addition, the nuclide specified by the operator is not 1 H. 19 F and 13 In any of C (No in step S102, No in step S106, No in step S210), the collection function 14a does not collect magnetic resonance signals and ends the processing.

[0089] Here, in the above-mentioned processing procedure, the processing of step S101 is realized, for example, by the processing circuit 16 reading out a prescribed program corresponding to the shooting control function 16a from the storage circuit 12 and executing it. In addition, the processing of steps S102 to S104, S106 to S108, and S210 to S213 is realized, for example, by the processing circuit 14 reading out a prescribed program corresponding to the collection function 14a from the storage circuit 12 and executing it. In addition, the processing of steps S105, S109, and S213 is realized, for example, by the processing circuit 15 reading out a prescribed program corresponding to the image generation function 15a from the storage circuit 12 and executing it.

[0090] By executing the above-described processing, the following 1 H. 19 F and 13 C is the shooting object of these three nuclides.

[0091] In addition, here, the second frequency and 13 The second frequency may also be matched with the resonance frequency of C. 13The resonance frequencies of the nuclides other than C are matched.

[0092] In addition, the transceiver system may also transmit and receive at a second frequency in a state where a second static magnetic field is applied in addition to the first static magnetic field, thereby further collecting magnetic resonance signals of other nuclides. 1 In addition to any three nuclides including H, another nuclide can be imaged as a target.

[0093] According to the above structure, it is possible to include 1 It can capture images of three or more nuclides including H with high quality.

[0094] (Third Embodiment)

[0095] In addition, for example, as a third embodiment, the collection function 14a may be configured to collect magnetic resonance signals for image generation in a plurality of times at intervals of a repetition time (TR). 1 H as the subject and 1 In the case of imaging with different nuclides as the target, the first static magnetic field is applied alternately for each TR to collect 1 The data of the magnetic resonance signal of H is collected, and a second static magnetic field is applied in addition to the first static magnetic field to collect the data related to 1 H Data collection of magnetic resonance signals of different nuclear species.

[0096] For example, as described in the first embodiment, the nuclide to be imaged is 1 H and 19 In the case of F, the collection function 14a collects alternately for each TR 1 Data collection and collection of H magnetic resonance signals 19 In addition, for example, when the nuclide to be imaged is 1 H. 19 F and 13 In the case of C, the collection function 14a collects each TR in sequence. 1 Data collection of H magnetic resonance signals, collection 19 Data collection of F magnetic resonance signals, collection 13 Data collection of magnetic resonance signals of C.

[0097] According to the above structure, it is possible to perform 1 The images of H and other nuclides are overlapped with each other. 1When evaluating the images of H, the positional deviation between the images can be reduced, and the image quality of the superimposed image can be improved.

[0098] (Fourth Embodiment)

[0099] In addition, for example, as a fourth embodiment, in the collection function 14a, 1 In the case of shooting with different nuclides as the object, 1 Compared with imaging with H as the target, magnetic resonance signals can be collected even in a narrow range in k-space.

[0100] For example, the collection function 14a is in the form of 1 In imaging with different nuclides as the target, magnetic resonance signals are collected from a region with many low-frequency components located in the center of k-space.

[0101] According to the above structure, 1 When imaging with nuclides of different H as the target, the amount of magnetic resonance signals to be collected can be reduced, and the imaging time can be shortened.

[0102] (Fifth Embodiment)

[0103] For example, as a fifth embodiment, the static magnetic field generating means may be realized by a static magnetic field magnet capable of generating a first static magnetic field and a static magnetic field having a magnitude obtained by adding a second static magnetic field to the first static magnetic field.

[0104] Figure 4 It is a diagram showing a configuration example of an MRI apparatus according to a fifth embodiment.

[0105] For example, Figure 4 As shown, the MRI apparatus 200 of the present embodiment includes a static magnetic field magnet 201, a static magnetic field power supply 218, a gradient magnetic field coil 2, a gradient magnetic field power supply 3, a whole-body RF (Radio Frequency) coil 4, a local RF coil 5, a transmitting circuit 6, a receiving circuit 7, a gantry 8, a diagnostic bed 9, an interface 10, a display 11, a storage circuit 12, and processing circuits 13 to 16.

[0106] Here, the configuration other than the static magnetic field magnet 201 , the static magnetic field power supply 218 , and the collection function 14 a is the same as that of the first embodiment.

[0107] Furthermore, in the present embodiment, the static magnetic field generating unit is implemented by the static magnetic field magnet 201 and the static magnetic field power supply 218 .

[0108] The static magnetic field magnet 201 generates a static magnetic field in the imaging space where the subject S is arranged. Specifically, the first static magnetic field magnet 1 is formed into a hollow substantially cylindrical shape (including the case where the shape of the cross section perpendicular to the central axis is an ellipse), and generates a static magnetic field in the imaging space formed on the inner circumference thereof. In the present embodiment, the first static magnetic field magnet 1 is an electromagnet realized by a coil formed into a hollow substantially cylindrical shape, and generates static magnetic fields of various sizes according to the size of the current supplied from the static magnetic field power supply 218.

[0109] The static magnetic field power supply 218 supplies a current for causing the static magnetic field magnet 201 to generate a static magnetic field under the control of the collection function 14 a .

[0110] Furthermore, in this embodiment, when the object to be photographed is 1H, the collection function 14a controls the static magnetic field power supply 218 so that only the first static magnetic field is applied. 1 In the case of nuclides of different species H, the static magnetic field power supply 218 is controlled so that a static magnetic field having a magnitude obtained by adding the second static magnetic field to the first static magnetic field is applied.

[0111] In addition, the collection function 14a controls the transceiver system according to the nuclide to be imaged, similarly to the first embodiment. 1 The transceiver system transmits and receives at a first frequency that matches the resonance frequency of H. Furthermore, the transceiver system transmits and receives at the first frequency when the first static magnetic field is applied, and transmits and receives at the first frequency when the second static magnetic field is applied in addition to the first static magnetic field. 1 H transmits and receives in a state where the resonance frequency of the different nuclides matches the first frequency.

[0112] According to the above configuration, similarly to the first embodiment, 1 H and 1 H takes different nuclides as the object and shoots with high image quality.

[0113] In addition, in the above-mentioned embodiment, an example is described in which the MRI apparatus has a so-called tunnel-type structure in which the static magnetic field magnet, the gradient magnetic field coil, and the whole body RF coil are respectively formed in a roughly cylindrical shape, but the embodiment is not limited to this. For example, the MRI apparatus may also have a so-called open-type structure in which a pair of static magnetic field magnets, a pair of gradient magnetic field coils, and a pair of RF coils are arranged in a manner opposite to each other with the imaging space for the subject being arranged sandwiched therebetween. In such an open-type structure, the space sandwiched by the pair of static magnetic field magnets, the pair of gradient magnetic field coils, and the pair of RF coils is equivalent to a hole in the tunnel-type structure.

[0114] Furthermore, the above-described embodiments may be implemented individually or in combination with one or more other embodiments as appropriate.

[0115] In addition, in the above-mentioned embodiment, an example of a case where the collection unit in this specification is implemented by the collection function 14a of the processing circuit 14 is described, but the embodiment is not limited to this. For example, in addition to being implemented by the collection function 14a described in the embodiment, the collection unit in this specification may also implement the same function only by hardware, only by software, or by a combination of hardware and software.

[0116] In addition, the term "processor" used in the above description refers to circuits such as CPU (Central Processing Unit), GPU (Graphics Processing Unit), or Application Specific Integrated Circuit (ASIC), programmable logic device (for example, Simple Programmable Logic Device (SPLD), Complex Programmable Logic Device (CPLD), and Field Programmable Gate Array (FPGA)). The processor implements its functions by reading and executing the program stored in the storage circuit. In addition, it can also be configured to directly load the program into the circuit of the processor instead of storing the program in the storage circuit. In this case, the processor implements its functions by reading and executing the program loaded into the circuit. In addition, the processor of this embodiment is not limited to the case of being configured as a single circuit, and multiple independent circuits can also be combined to form one processor to implement its functions.

[0117] Here, the program executed by the processor is provided by pre-loading it into a ROM (Read Only Memory) or a storage circuit, etc. In addition, the program can also be provided in a form that can be installed in these devices or in an executable form, recorded in a computer-readable storage medium such as a CD (Compact Disk)-ROM, FD (Flexible Disk), CD-R (Recordable), DVD (Digital Versatile Disk), etc. In addition, the program can also be stored in a computer connected to a network such as the Internet, and provided or distributed by downloading it through the network. For example, the program is composed of modules including the above-mentioned functional units. As actual hardware, the CPU reads out the program from a storage medium such as a ROM and executes it, thereby loading each module onto the main storage device and generating it on the main storage device.

[0118] According to at least one embodiment described above, it is possible to convert hydrogen nuclei 1 H and 1 H Different nuclides are taken as objects and photographed with high quality.

[0119] Several embodiments of the present invention are described above, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, changes, etc. can be made without departing from the scope of the subject matter of the invention. These embodiments and their variations are included in the scope and subject matter of the invention, and are also included in the invention described in the claims and their equivalents.

Claims

1. A magnetic resonance imaging device comprising: A first static magnetic field magnet generates a first static magnetic field serving as a reference; A second static magnetic field magnet applies a second static magnetic field on the basis of the first static magnetic field; a transceiver system for transceiving at a first frequency; and A collecting unit uses the transceiver system to collect magnetic resonance signals, The transceiver system, When the target nuclide is a hydrogen nucleus, transmitting and receiving are performed at the first frequency matching the resonance frequency of the hydrogen nucleus in a state where the first static magnetic field is applied. When the target nuclide is a nuclide different from the hydrogen nucleus, the second static magnetic field is applied in addition to the first static magnetic field, thereby performing transmission and reception in a state where the resonance frequency of the nuclide different from the hydrogen nucleus matches the first frequency.

2. The magnetic resonance imaging apparatus according to claim 1, wherein: The transceiver system sets the reception gain of the magnetic resonance signal of a nuclide different from the hydrogen nucleus to be larger than the reception gain of the magnetic resonance signal of the hydrogen nucleus when the second static magnetic field is applied in addition to the first static magnetic field.

3. The magnetic resonance imaging apparatus according to claim 1, wherein: The collection unit, when performing a shooting method of collecting magnetic resonance signals used in image generation multiple times at intervals of a repetition time to perform shooting with the hydrogen nuclei as the object and shooting with a nuclide different from the hydrogen nuclei as the object, alternately applies the first static magnetic field according to the repetition time to collect data of the magnetic resonance signals of the hydrogen nuclei, and applies the second static magnetic field in addition to the first static magnetic field to collect data of the magnetic resonance signals of the nuclide different from the hydrogen nuclei.

4. The magnetic resonance imaging apparatus according to claim 3, wherein: The acquisition unit acquires magnetic resonance signals for a narrower range in k-space than for the imaging targeting the hydrogen nuclei in the imaging targeting the nuclear species different from the hydrogen nuclei.

5. A magnetic resonance imaging apparatus, wherein: have: A first static magnetic field magnet generates a first static magnetic field serving as a reference; A second static magnetic field magnet applies a second static magnetic field on the basis of the first static magnetic field; A transceiver system for transmitting and receiving at a first frequency or a second frequency; as well as A collecting unit uses the transceiver system to collect magnetic resonance signals, The transceiver system, When the target nuclide is a hydrogen nucleus, transmitting and receiving are performed at the first frequency matching the resonance frequency of the hydrogen nucleus in a state where the first static magnetic field is applied. When the target nuclide is a first nuclide different from the hydrogen nucleus, transmitting and receiving are performed at the second frequency matching the resonance frequency of the first nuclide in a state where the first static magnetic field is applied. When the target nuclide is a second nuclide different from either the hydrogen nucleus or the first nuclide, the second static magnetic field is applied in addition to the first static magnetic field, so that transmission and reception are performed at the first frequency in a state where the resonance frequency of the second nuclide matches the first frequency.

6. The magnetic resonance imaging apparatus according to claim 5, wherein: The state in which the resonance frequency of the second nuclear species matches the first frequency is a state in which the resonance frequency of the nuclear species matches so as to be included in the frequency band of the transmission and reception system and the frequency band of the image.

7. The magnetic resonance imaging apparatus according to claim 5, wherein: The transceiver system, when the second nuclear species is a nuclear species whose spin rotation direction is opposite to that of the hydrogen nucleus, in a state where the second static magnetic field is applied in addition to the first static magnetic field, reverses the phase of the high frequency used in the transceiver, thereby matching the resonance frequency of the second nuclear species with the first frequency.

Images