Magnetic resonance imaging devices and methods

Abstract

One of the technical problems to be solved by a magnetic resonance imaging (MRI) apparatus and method is to improve the sensitivity of the RF coils when the magnetic field strength of a static magnetic field varies spatially. The MRI apparatus according to the embodiment includes a static magnetic field magnet, multiple high-frequency coils, and a control unit. The static magnetic field magnet generates a static magnetic field whose magnetic field strength varies spatially. The high-frequency coils receive nuclear magnetic resonance (NMR) signals generated from a subject due to the influence of high-frequency pulses transmitted to a subject placed within the static magnetic field whose magnetic field strength varies spatially. The control unit controls each of the multiple high-frequency coils in such a way that it receives the NMR signals at at least at each of a plurality of frequencies adjusted according to the distribution of the static magnetic field.

Description

[0001] Reference to related applications

[0002] This application enjoys the benefit of priority to Japanese Patent Application No. 2021-083898, filed on May 18, 2021, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The embodiments disclosed in this specification and accompanying drawings relate to magnetic resonance imaging apparatus and methods. Background Technology

[0004] Traditionally, magnetic resonance imaging (MRI) devices transmit high-frequency (RF) pulses to a subject placed in a static magnetic field and receive the nuclear magnetic resonance (NMR) signals generated from the subject due to the influence of these RF pulses to generate images. These MRI devices include an RF coil tuned to a predetermined resonance frequency for both transmitting RF pulses and receiving NMR signals. Summary of the Invention

[0005] One of the technical problems to be solved by the embodiments disclosed in this specification and accompanying drawings is to improve the sensitivity of the RF coil when the magnetic field strength of the static magnetic field varies spatially. However, the technical problems to be solved by the embodiments disclosed in this specification and accompanying drawings are not limited to the above-mentioned technical problems. Other technical problems can also be identified as corresponding to the effects of the various structures shown in the embodiments described below.

[0006] The magnetic resonance imaging apparatus according to the embodiment includes a static magnetic field magnet, multiple high-frequency coils, and a control unit. The static magnetic field magnet generates a static magnetic field whose magnetic field strength varies spatially. The high-frequency coils receive nuclear magnetic resonance signals generated from the subject due to the influence of high-frequency pulses transmitted to the subject placed within the static magnetic field whose magnetic field strength varies spatially. The control unit controls each of the multiple high-frequency coils in such a way that it receives the nuclear magnetic resonance signals at least at each of a plurality of frequencies adjusted according to the distribution of the static magnetic field.

[0007] Effect

[0008] According to the embodiment, the medical image processing apparatus can improve the sensitivity of the RF coil when the magnetic field strength of the static magnetic field varies in space. Attached Figure Description

[0009] Figure 1 This is a diagram showing a structural example of the MRI device according to the first embodiment.

[0010] Figure 2 This is a diagram showing the static magnetic field generated by the static magnetic field magnet according to the first embodiment.

[0011] Figure 3 This is a graph used to illustrate the decrease in sensitivity of the RF coil associated with the first embodiment.

[0012] Figure 4 This diagram illustrates an example of the RF coil included in the MRI apparatus according to the first embodiment.

[0013] Figure 5 This diagram illustrates an example of the RF coil included in the MRI apparatus according to the first embodiment.

[0014] Figure 6 This diagram illustrates an example of the RF coil included in the MRI apparatus according to the first embodiment.

[0015] Figure 7 This is a diagram illustrating an example of the structure of the transmission and reception system of the MRI apparatus according to the first embodiment.

[0016] Figure 8 This diagram illustrates an example of video recording performed using the camera control function described in the first embodiment.

[0017] Figure 9 This diagram illustrates an example of the RF coil included in the MRI apparatus according to the second embodiment.

[0018] Figure 10 This is a diagram illustrating an example of the structure of the transmission and reception system of the MRI apparatus according to the second embodiment.

[0019] Figure 11 This is a diagram illustrating an example of the structure of the transmission and reception system of the MRI apparatus according to the third embodiment.

[0020] Figure 12 This is a diagram illustrating an example of the structure of the transmission and reception system of the MRI apparatus according to the fourth embodiment.

[0021] Figure 13 This is a diagram illustrating an example of the structure of the transmission and reception system included in the MRI apparatus according to the fifth embodiment.

[0022] Figure 14 This is a diagram illustrating an example of the structure of the transmission and reception system included in the MRI apparatus according to the sixth embodiment.

[0023] Figure 15This is a diagram illustrating an example of the structure of the transmission and reception system included in the MRI apparatus according to the seventh embodiment.

[0024] Figure 16 This is a diagram illustrating an example of the structure of the transmission and reception system included in the MRI apparatus according to the eighth embodiment.

[0025] Figure 17 This is a diagram illustrating an example of the structure of the transmission and reception system included in the MRI apparatus according to the ninth embodiment. Detailed Implementation

[0026] The magnetic resonance imaging apparatus according to the embodiment includes a static magnetic field magnet, multiple high-frequency coils, and a control unit. The static magnetic field magnet generates a static magnetic field whose magnetic field strength varies spatially. The high-frequency coils receive nuclear magnetic resonance signals generated from the subject due to the influence of high-frequency pulses transmitted to the subject placed within the static magnetic field whose magnetic field strength varies spatially. The control unit controls the multiple high-frequency coils respectively to receive the nuclear magnetic resonance signals at at least each of a plurality of frequencies adjusted according to the distribution of the static magnetic field.

[0027] Hereinafter, with reference to the accompanying drawings, the embodiments of the MRI apparatus and method involved in this application will be described in detail.

[0028] (First Implementation)

[0029] Figure 1 This is a diagram showing a structural example of the MRI device according to the first embodiment.

[0030] For example, such as Figure 1 As shown, the MRI device 100 includes a static magnetic field magnet 1, a gradient magnetic field coil 2, a gradient magnetic field power supply 3, a whole body RF coil 4, a local RF coil 5, a transmitter circuitry 6, a receiver circuitry 7, an RF shield 8, a gantry 9, an examination table 10, an input interface 11, a display 12, a storage circuitry 13, and processing circuitry 14-17.

[0031] The static magnetic field magnet 1 generates a static magnetic field in the imaging space where the subject S is placed. Specifically, the static magnetic field magnet 1 is formed as a hollow, generally cylindrical shape (including those with an elliptical cross-section orthogonal to the central axis), generating a static magnetic field in the imaging space formed on its inner periphery. For example, the static magnetic field magnet 1 is a superconducting magnet, a permanent magnet, etc. The superconducting magnet mentioned here is, for example, composed of a container filled with a coolant such as liquid helium and a superconducting coil immersed in the container.

[0032] A gradient magnetic field coil 2 is positioned inside the static magnetic field magnet 1 to generate a gradient magnetic field in the imaging space where the subject S is placed. Specifically, the gradient magnetic field coil 2 is formed as a hollow, generally cylindrical shape (including those with an elliptical cross-section orthogonal to the central axis), and has an X-coil, a Y-coil, and a Z-coil corresponding to the X-axis, Y-axis, and Z-axis, respectively, which are orthogonal to each other. Based on the current supplied from the gradient magnetic field power supply 3, the X-coil, Y-coil, and Z-coil generate a gradient magnetic field that varies linearly along each axis in the imaging space. Here, the Z-axis is set along the magnetic flux of the static magnetic field generated by the static magnetic field magnet 1. In addition, the X-axis is set along a horizontal direction orthogonal to the Z-axis, and the Y-axis is set along a vertical direction orthogonal to the Z-axis. Here, the X-axis, Y-axis, and Z-axis constitute the inherent device coordinate system of the MRI apparatus 100.

[0033] 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, Y, and Z coils of the gradient magnetic field coil 2, respectively, to generate gradient magnetic fields in the imaging space that vary linearly along mutually orthogonal readout, phase encoding, and slice directions. Here, the axes along the readout direction, the phase encoding direction, and the slice direction constitute a logical coordinate system for defining the slice region or volume region of the object being imaged.

[0034] Specifically, gradient magnetic fields along the readout direction, phase encoding direction, and slicing direction overlap with the static magnetic field generated by the static magnetic field magnet 1, thereby imparting spatial positional information to the NMR signal generated from the subject S. Specifically, the gradient magnetic field along the readout direction causes a frequency change in the NMR signal based on the position of the readout direction, thus imparting positional information about the readout direction to the NMR signal. Similarly, the gradient magnetic field along the phase encoding direction causes a phase change in the NMR signal based on the position of the phase encoding direction, thereby imparting positional information about the phase encoding direction to the NMR signal. Furthermore, the gradient magnetic field along the slicing direction imparts positional information about the slicing direction to the NMR signal. For example, the gradient magnetic field along the slicing direction is used to determine the orientation, thickness, and number of slices in the case where the imaging area is a sliced ​​area (2D imaging), and to cause a phase change in the NMR signal based on the position of the slicing direction in the case where the imaging area is a volumetric area (3D imaging).

[0035] A whole-body RF coil 4 is disposed on the inner periphery of the gradient magnetic field coil 2, transmitting RF pulses to a subject S disposed in the imaging space and receiving the NMR signal generated from the subject S due to the influence of the RF pulses. Specifically, the whole-body RF coil 4 is formed as a hollow, generally cylindrical shape (including those with an elliptical cross-section orthogonal to the central axis), applying an RF magnetic field to the subject S disposed in the imaging space located on its inner periphery based on the RF pulses supplied from the transmitting circuit 6. Furthermore, the whole-body RF coil 4 receives the NMR signal generated from the subject S due to the influence of the RF magnetic field and outputs the received NMR signal to the receiving circuit 7. For example, the whole-body RF coil 4 is a birdcage-type coil or a TEM (Transverse Electromagnetic) coil. In addition, the whole-body RF coil 4 may not necessarily have both transmitting and receiving functions, or may only have a transmitting function.

[0036] A local RF coil 5 is positioned near the subject S during imaging, transmitting RF pulses to the subject S positioned in the imaging space and receiving the NMR signal generated from the subject S due to the influence of the RF pulses. Specifically, the local RF coil 5 is prepared for each part of the subject S and is positioned near the part of the subject being imaged during imaging. Based on the RF pulses supplied from the transmitting circuit 6, it applies an RF magnetic field to the subject S. Furthermore, the local RF coil 5 receives the NMR signal generated from the subject S due to the influence of the RF magnetic field and outputs the received NMR signal to the receiving circuit 7. For example, the local RF coil 5 is a surface coil, or a phased array coil composed of multiple surface coils as coil elements. Alternatively, the local RF coil 5 may not necessarily have both transmitting and receiving functions, but only a receiving function.

[0037] The transmitting circuit 6 outputs an RF pulse corresponding to the inherent resonance frequency (Larmor frequency) of the atomic nucleus of the object placed in the static magnetic field to the whole-body RF coil 4 or the local RF coil 5.

[0038] The receiving circuit 7 generates NMR data based on the NMR signal output from the whole-body RF coil 4 or the local RF coil 5, and outputs the generated NMR data to the processing circuit 15.

[0039] An RF shield 8 is disposed between the gradient magnetic field coil 2 and the whole-body RF coil 4 to shield the gradient magnetic field coil 2 from the RF magnetic field generated by the whole-body RF coil 4. Specifically, the RF shield 8 is formed as a hollow, generally cylindrical shape (including those with an elliptical cross-section orthogonal to the central axis of the cylinder), and is disposed in the space on the inner periphery of the gradient magnetic field coil 2 in such a way as to cover the outer periphery of the whole-body RF coil 4.

[0040] The mounting platform 9 has a hollow bore 9a that is generally cylindrical (including those with an elliptical cross-section orthogonal to the central axis), housing a static magnetic field magnet 1, a gradient magnetic field coil 2, a whole-body RF coil 4, and an RF shield 8. Specifically, the mounting platform 9 houses the whole-body RF coil 4 on the outer periphery of the bore 9a, the RF shield 8 on the outer periphery of the whole-body RF coil 4, the gradient magnetic field coil 2 on the outer periphery of the RF shield 8, and the static magnetic field magnet 1 on the outer periphery of the gradient magnetic field coil 2. Here, the space within the bore 9a of the mounting platform 9 becomes the imaging space for arranging the subject S during imaging.

[0041] The examination bed 10 has a top plate 10a on which a subject S is placed. When imaging the subject S, the top plate 10a on which the subject S is placed is moved into the imaging space. For example, the examination bed 10 is arranged such that the length direction of the top plate 10a is parallel to the central axis of the static magnetic field magnet 1.

[0042] Input interface 11 receives various instructions and information input operations from the operator. Specifically, input interface 11 is connected to processing circuit 17, converting the input operations received by the operator into electrical signals and outputting them to processing circuit 17. For example, input interface 11 can be implemented using a trackball for setting camera conditions, region of interest (ROI), a switch button, a mouse, a keyboard, a touchpad for input operations via touch operation surface, a touch screen integrating the display screen and touchpad, a contactless input circuit using an optical sensor, and a voice input circuit. Furthermore, in this specification, input interface 11 is not limited to interfaces with physical operating components such as a mouse and keyboard. For example, a processing circuit that receives electrical signals corresponding to input operations from an external input device separate from the device and outputs such electrical signals to the control circuit is also included in the example of input interface 11.

[0043] The display 12 displays various information. Specifically, the display 12 is connected to the processing circuit 17, which converts the data of various information sent from the processing circuit 17 into electrical signals for display and outputs them. For example, the display 12 can be implemented as a liquid crystal monitor, a CRT (cathode ray tube) monitor, a touch panel, etc.

[0044] Storage circuit 13 stores various types of data. Specifically, storage circuit 13 is connected to processing circuits 14-17 and stores various types of data input and output by each processing circuit. For example, storage circuit 13 is implemented using semiconductor memory elements such as RAM (Random Access Memory), flash memory, hard disk, optical disk, etc.

[0045] The processing circuit 14 has a bed control function 14a. The bed control function 14a controls the operation of the bed 10 by outputting control electrical signals to the bed 10. For example, the bed control function 14a receives instructions from the operator via the input interface 11 to move the top plate 10a along the length direction, the up and down direction, or the left and right direction, and actuates the moving mechanism of the top plate 10a on the bed 10 to move the top plate 10a according to the received instructions.

[0046] The processing circuit 15 has a collection function 15a. The collection function 15a collects k-space data by executing various pulse sequences. Specifically, the collection function 15a drives the gradient magnetic field power supply 3, the transmitting circuit 6, and the receiving circuit 7 to execute various pulse sequences based on the sequence execution data output from the processing circuit 17. Here, the sequence execution data is data representing the pulse sequence, specifying the timing and intensity of the current supplied by the gradient magnetic field power supply 3 to the gradient magnetic field coil 2, the timing and intensity of the RF pulses supplied by the transmitting circuit 6 to the whole-body RF coil 4, and the timing of the sampling of the NMR signal by the receiving circuit 7. Furthermore, the collection function 15a receives the NMR data output from the receiving circuit 7 as a result of executing the pulse sequences and stores it in the storage circuit 13. At this time, the NMR data stored in the storage circuit 13 is stored as k-space data representing 2D or 3D k-space by being endowed with positional information along the readout direction, phase encoding direction, and slice direction by the aforementioned gradient magnetic fields.

[0047] The processing circuit 16 has a generation function 16a. The generation function 16a generates an image based on the k-space data collected by the processing circuit 15. Specifically, the generation function 16a reads the k-space data collected by the processing circuit 15 from the storage circuit 13, performs reconstruction processing such as Fourier transform on the read k-space data, thereby generating a 2D or 3D image. Then, the generation function 16a stores the generated image in the storage circuit 13.

[0048] The processing circuit 17 has a camera control function 17a. The camera control function 17a performs various imaging operations by controlling the various components of the MRI apparatus 100. Specifically, the camera control function 17a displays a GUI (Graphical User Interface) on the display 12 for receiving various instructions and information input from the operator, and controls the various components of the MRI apparatus 100 based on the input operations received via the input interface 11. For example, the camera control function 17a generates sequence execution data based on imaging conditions input by the operator and outputs the generated sequence execution data to the processing circuit 15, thereby collecting k-space data. Additionally, for example, the camera control function 17a reconstructs an image based on the k-space data collected by the processing circuit 15 by controlling the processing circuit 16. Furthermore, for example, the camera control function 17a reads an image from the storage circuit 13 according to a request from the operator and displays the read image on the display 12.

[0049] Here, the aforementioned processing circuits 14 to 17 are implemented, for example, by a processor. In this case, the processing functions of each processing circuit are stored in the storage circuit 13, for example, as programs executable by a computer. Furthermore, each processing circuit implements the processing function corresponding to each program by reading it from the storage circuit 13 and executing it. In other words, each processing circuit, after reading its program, has... Figure 1 The functions shown in each processing circuit.

[0050] Furthermore, this description assumes that each processing circuit is implemented using a single processor, but the implementation is not limited to this. Multiple independent processors can also be combined to form each processing circuit, with each processor executing a program to perform its respective processing function. Additionally, the processing functions of each processing circuit can be appropriately distributed or combined within one or more processing circuits. Figure 1 In the example shown, it is assumed that a single storage circuit 13 stores the program corresponding to each processing function. However, it can also be configured with multiple storage circuits distributed, and the processing circuit reads the corresponding program from the independent storage circuit.

[0051] The above describes a structural example of the MRI apparatus 100 according to this embodiment. Based on this structure, in this embodiment, the static magnetic field magnet 1 generates a static magnetic field with spatially varying magnetic field strength in at least a portion of the area within the aperture 9a that forms the imaging space.

[0052] Figure 2 This is a diagram showing the static magnetic field generated by the static magnetic field magnet 1 according to the first embodiment.

[0053] For example, such as Figure 2 As shown, the static magnetic field generated by the cylindrical static magnetic field magnet 1 has a uniform magnetic field strength in the region RC (hereinafter the uniform region) near the center of the hole 9a, but is not uniform in the surrounding region RP, and the magnetic field strength varies in space.

[0054] In this embodiment, a static magnetic field whose magnetic field strength varies spatially can also be defined as: a static magnetic field that governs a region where the magnetic field strength decreases with distance from the static magnetic field magnet 1, a region outside a uniform region where the magnetic field strength is uniform, a region where the magnetic field strength is non-uniform, or a region where the magnetic field strength varies by 30 mT per meter. That is, a static magnetic field whose magnetic field strength varies spatially can also be described as a static magnetic field that stably forms a region with non-uniform magnetic field strength regardless of whether a uniform region of static magnetic field is formed.

[0055] In contrast, RF coils for receiving NMR signals are generally tuned to a specific resonant frequency corresponding to the magnetic field strength in a uniform region, assuming a uniform magnetic field strength. Therefore, the sensitivity of the RF coil may decrease in regions where the magnetic field strength varies spatially.

[0056] Figure 3 This is a graph used to illustrate the decrease in sensitivity of the RF coil associated with the first embodiment.

[0057] Here, Figure 3 A static magnetic field is conceptually represented as a region where the magnetic field strength varies in space. The distribution of the static magnetic field is represented by shaded patterns, and the darker the shaded patterns, the stronger the magnetic field strength.

[0058] For example, such as Figure 3 As shown, when the magnetic field strength decreases as the distribution of the static magnetic field expands, the resonant frequency also decreases.

[0059] In contrast, generally speaking, RF coil 20, such as Figure 3 As shown by the curve SD, it has the following sensitivity distribution and is tuned to receive signals in a certain frequency band Δf centered at the resonant frequency. This sensitivity distribution has maximum sensitivity at a specific resonant frequency and decreases as the frequency moves away from the resonant frequency. Therefore, as... Figure 3 As shown, the region R in which the RF coil 20 can receive NMR signals is limited to the range where the resonant frequency enters the frequency band Δf. At the position where the resonant frequency deviates from the frequency band Δf, the sensitivity of the RF coil 20 decreases.

[0060] Therefore, the MRI device 100 according to this embodiment is configured to improve the sensitivity of the RF coil when the magnetic field strength of the static magnetic field changes in space.

[0061] Specifically, the MRI device 100 includes an RF coil that transmits RF pulses to a subject placed within a static magnetic field whose magnetic field strength varies spatially due to the static magnetic field magnet 1, and receives the NMR signal generated from the subject due to the influence of the RF pulses. Here, the RF coil can be a whole-body RF coil 4 or a local RF coil 5. Alternatively, the RF coil can be a combination of the transmitting function of the whole-body RF coil 4 and the receiving function of the local RF coil 5.

[0062] Furthermore, the camera control function 17a of the processing circuit 17 controls the RF coil to receive NMR signals at various frequencies of multiple frequencies adjusted according to the distribution of the static magnetic field generated by the static magnetic field magnet 1. Here, the camera control function 17a is an example of a control unit.

[0063] In this embodiment, the MRI apparatus 100 includes multiple RF coils, each individually adjustable to a multiple frequency. Furthermore, the camera control function 17a controls the multiple RF coils to receive NMR signals at each of the multiple frequencies.

[0064] Figures 4-6 This diagram shows an example of the RF coil included in the MRI apparatus 100 according to the first embodiment.

[0065] Here, Figures 4-6 and Figure 3 Similarly, an example is shown where the magnetic field strength decreases as the distribution of the static magnetic field expands.

[0066] For example, such as Figure 4 As shown, the MRI apparatus 100 includes a first RF coil 120a adjusted to frequency A and a second RF coil 120b adjusted to frequency B. Here, the frequency A of the first RF coil 120a is adjusted to a resonant frequency corresponding to the magnetic field strength of the static magnetic field in a first region Ra included in the range of the static magnetic field distribution. On the other hand, the frequency B of the second RF coil 120b is adjusted to a resonant frequency corresponding to the magnetic field strength of the static magnetic field in a second region Rb included in a range where the magnetic field strength of the static magnetic field is lower than that of the first region Ra.

[0067] In this case, the first RF coil 120a is positioned to receive the NMR signal generated in the first region Ra, and the second RF coil 120b is positioned to receive the NMR signal generated in the second region Rb. For example, as Figure 4 As shown, for the first RF coil 120a and the second RF coil 120b, the detection surface of the first RF coil 120a is configured orthogonally to the direction of the static magnetic field distribution, and the detection surface of the second RF coil 120b is configured parallel to the direction of the static magnetic field distribution. Alternatively, for example, as... Figure 5 As shown, the first RF coil 120a and the second RF coil 120b can also be stacked in a manner in which their respective detection surfaces are orthogonal to the direction of the distribution and expansion of the static magnetic field.

[0068] Furthermore, the camera control function 17a controls the first RF coil 120a in a manner that receives NMR signals at frequency A, and controls the second RF coil 120b in a manner that receives NMR signals at frequency B.

[0069] Based on this structure, by using two RF coils 120a and 120b, which are adjusted to two frequencies A and B in a state where each coil is independent or electromagnetically coupled, for example, Figure 6As shown, NMR signals can be received from two regions, Ra and Rb, along the direction of the static magnetic field distribution. Therefore, the range of NMR signals that can be received along the direction of the static magnetic field distribution can be expanded, thus improving the sensitivity of the RF coil.

[0070] Furthermore, an example of using two RF coils to receive NMR signals at two frequencies has been described here, but the number of RF coils and frequencies is not limited to two; there can also be three or more. Therefore, it is possible to receive NMR signals from more than three regions along the direction of the static magnetic field distribution, further expanding the range of NMR signal reception.

[0071] For example, in this embodiment, the MRI apparatus 100 includes, as described above, a plurality of transmitting coils for transmitting RF pulses and a plurality of receiving coils for receiving NMR signals.

[0072] Figure 7 This is a diagram illustrating an example of the structure of the transmission and reception system included in the MRI apparatus 100 according to the first embodiment.

[0073] For example, such as Figure 7 As shown, the MRI device 100 has a first transmitting coil 121a and a first receiving coil 122a adjusted to frequency A, and a second transmitting coil 121b and a second receiving coil 122b adjusted to frequency B.

[0074] The first transmitting coil 121a transmits an RF signal of frequency A to the subject according to a control signal sent from the camera control function 17a of the processing circuit 17 via the processing circuit 15. The first receiving coil 122a receives the NMR signal of frequency A generated from the subject according to the control signal sent from the camera control function 17a of the processing circuit 17 via the processing circuit 15. The second transmitting coil 121b transmits an RF signal of frequency B to the subject according to a control signal sent from the camera control function 17a of the processing circuit 17 via the processing circuit 15. The second receiving coil 122b receives the NMR signal of frequency B generated from the subject according to the control signal sent from the camera control function 17a of the processing circuit 17 via the processing circuit 15.

[0075] Additionally, the MRI apparatus 100 includes: a pulse generator 161, a DAC (Digital to Analog Converter) 162, a switching switch 163, a synthesizer 164, a first modulator 165a, a second modulator 165b, a first RF amplifier 166a, and a second RF amplifier 166b. For example, these devices are included in... Figure 1 The transmitting circuit 6 is shown.

[0076] Pulse generator 161 generates an RF pulse waveform. DAC 162 converts the RF pulse waveform generated by pulse generator 161 from an analog signal to a digital signal and outputs it. Switch 163, based on a control signal sent from camera control function 17a of processing circuit 17 via processing circuit 15, outputs the digital signal from DAC 162 to one of first modulator 165a and second modulator 165b. Synthesizer 164 generates and outputs an RF signal. First modulator 165a, after converting the frequency of the RF signal output from synthesizer 164 to frequency A, modulates the RF signal with the waveform of the digital signal output from switch 163, thereby generating an RF pulse of frequency A. Second modulator 165b, after converting the frequency of the RF signal output from synthesizer 164 to frequency B, modulates the RF signal with the waveform of the digital signal output from switch 163, thereby generating an RF pulse of frequency B. The first RF amplifier 166a amplifies the RF pulse of frequency A generated by the first modulator 165a and outputs it to the first transmitting coil 121a. The second RF amplifier 166b amplifies the RF pulse of frequency B generated by the second modulator 165b and outputs it to the second transmitting coil 121b.

[0077] Additionally, the MRI apparatus 100 includes a first preamplifier 171a, a second preamplifier 171b, a first detector 172a, a second detector 172b, a first ADC (Analog to Digital Converter) 173a, and a second ADC 173b. For example, these devices are included in... Figure 1 The receiving circuit 7 is shown.

[0078] The first preamplifier 171a amplifies and outputs the NMR signal at frequency A received by the first receiving coil 122a. The second preamplifier 171b amplifies and outputs the NMR signal at frequency B received by the second receiving coil 122b. After converting the frequency of the RF signal output from the synthesizer 164 to frequency A, the first detector 172a uses the RF signal to detect the NMR signal output from the first preamplifier 171a and outputs it to the first ADC 173a. After converting the frequency of the RF signal output from the synthesizer 164 to frequency B, the second detector 172b uses the RF signal to detect the NMR signal output from the second preamplifier 171b and outputs it to the second ADC 173b. The first ADC 173a generates NMR data by converting the NMR signal output from the first detector 172a from an analog signal to a digital signal, and outputs the generated NMR data to the processing circuit 15. The second ADC173b generates NMR data by converting the NMR signal output from the second detector 172b from an analog signal to a digital signal, and outputs the generated NMR data to the processing circuit 15.

[0079] Furthermore, the camera control function 17a controls the first transmitting coil 121a by transmitting RF pulses at frequency A, and controls the first receiving coil 122a by receiving NMR signals at frequency A. Additionally, the camera control function 17a controls the second transmitting coil 121b by transmitting RF pulses at frequency B, and controls the second receiving coil 122b by receiving NMR signals at frequency B.

[0080] At this time, when one of the first transmitting coil 121a and the second transmitting coil 121b transmits an RF pulse, the camera control function 17a controls the other transmitting coil to be in a decoupled state. Additionally, at this time, the camera control function 17a controls the image so that either the first receiving coil 122a or the second receiving coil 122b is in a decoupled state.

[0081] Furthermore, when the first receiving coil 122a and the second receiving coil 122b receive NMR signals, the camera control function 17a controls them to ensure that each receiving coil can receive simultaneously. Additionally, at this time, the camera control function 17a controls both the first transmitting coil 121a and the second transmitting coil 121b to be in a decoupled state.

[0082] For example, the camera control function 17a controls each RF coil to transmit or receive at a desired frequency by controlling components such as PIN diodes provided in each RF coil. Alternatively, for example, the camera control function 17a controls the RF coil by controlling components such as PIN diodes provided in each RF coil to shift the adjusted frequency from the desired frequency, thereby decoupling each RF coil.

[0083] With this structure, the camera control function 17a controls multiple RF coils to receive NMR signals at various frequencies and performs various camera operations.

[0084] In this case, the camera control function 17a controls the RF coil based on the frequency when transmitting RF pulses to switch the frequency when receiving NMR signals.

[0085] Specifically, the camera control function 17a controls the RF coil based on the position of the camera slice to switch the frequency when receiving NMR signals.

[0086] For example, camera control function 17a controls the RF coil by sequentially sending RF pulses at various frequencies of multiple frequencies and sequentially receiving NMR signals at various frequencies of multiple frequencies.

[0087] Figure 8 This diagram illustrates an example of video recording performed by the camera control function 17a according to the first embodiment.

[0088] For example, such as Figure 8 As shown in (a), when multiple image slices A to D are imaged, the magnetic field strength of the static magnetic field generated by the static magnetic field magnet 1 is assumed to vary along the slice direction. In this case, the image control function 17a controls each transmitting coil and each receiving coil to transmit RF pulses and receive NMR at different frequencies according to each image slice.

[0089] For example, such as Figure 8 As shown in (b), the camera control function 17a controls the RF coil (transmitting coil) in the following manner: For each image slice, at intervals of TR (Repetition Time), it sequentially transmits RF pulses (90° pulses) at a resonant frequency corresponding to the magnetic field strength of the static magnetic field at the location of each image slice. Furthermore, the camera control function 17a controls the RF coil (receiving coil) in the following manner: It changes the magnetic field strength of the gradient magnetic field in the phase encoding direction according to each TR, while simultaneously receiving NMR signals sequentially at the same frequency as the RF pulses.

[0090] In this case, for example, if the change in magnetic field strength of the static magnetic field along the slice direction has a sufficient gradient, the gradient magnetic field along the slice direction may not be used. Alternatively, the gradient magnetic field along the slice direction may be used as an auxiliary method to correct the linearity of the change in magnetic field strength of the static magnetic field. In this case, the camera control function 17a controls the RF coil to transmit and receive at various frequencies of multiple frequencies adjusted according to the distribution of the static magnetic field and the gradient magnetic field.

[0091] As described above, in the first embodiment, the static magnetic field magnet 1 generates a static magnetic field whose magnetic field strength varies spatially. Furthermore, the RF coil sends RF pulses to a subject placed within the static magnetic field generated by the static magnetic field magnet 1, and receives the NMR signal generated from the subject due to the influence of the RF pulses. Moreover, the camera control function 17a controls the RF coil to receive the NMR signal at least at each of a plurality of frequencies adjusted according to the distribution of the static magnetic field.

[0092] Specifically, in the first embodiment, the MRI apparatus 100 includes multiple RF coils, each individually adjustable to a multiple frequency. Furthermore, the camera control function 17a controls the multiple RF coils separately to receive NMR signals at each of the multiple frequencies.

[0093] Based on this structure, when the magnetic field strength of the static magnetic field varies in space, the range of NMR signals that can be received can be expanded by using multiple frequencies, and the sensitivity of the RF coil can be improved.

[0094] The first embodiment has been described above, but the embodiments of the MRI device 100 according to this application are not limited to this. Therefore, other embodiments of the MRI device 100 according to this application will be described below. In addition, in the following embodiments, the description will focus on the points that are different from the first embodiment, and the description of the contents that are common to the first embodiment will be omitted.

[0095] (Second Implementation)

[0096] For example, in the first embodiment described above, an example was given where the MRI apparatus 100 has multiple RF coils, each individually adjustable to a multiple frequency, but the embodiments are not limited to this. For example, the MRI apparatus 100 may also have RF coils configured to be individually adjustable to multiple frequencies. Hereinafter, such an example will be described as a second embodiment.

[0097] In this embodiment, the MRI apparatus 100 includes an RF coil configured to be adjustable to multiple frequencies. Furthermore, the camera control function 17a switches the frequency of the RF coil to receive NMR signals at each of the multiple frequencies.

[0098] For example, an RF coil configured to be adjustable to multiple frequencies may be a dual-tuned coil. For instance, camera control function 17a switches the frequency of the RF coil by controlling components such as PIN diodes provided in the RF coil to change the pattern of the coil elements included in the RF coil. Alternatively, for example, camera control function 17a switches the frequency of the RF coil by changing the capacitance of a trimmer capacitor provided in the RF coil to shift the adjusted frequency.

[0099] Figure 9 This diagram illustrates an example of the RF coil included in the MRI apparatus 100 according to the second embodiment.

[0100] in addition, Figure 9 and Figure 3 Similarly, an example is shown where the magnetic field strength decreases as the distribution of the static magnetic field expands.

[0101] For example, such as Figure 9 As shown, the MRI apparatus 100 includes an RF coil 220 configured to be adjustable to two frequencies, A and B. Then, the camera control function 17a switches the frequency of the RF coil 220 to receive NMR signals at frequencies A and B respectively.

[0102] In this embodiment, frequency A is also set to the resonant frequency corresponding to the magnetic field strength of the static magnetic field in the first region Ra, which is included in the range of static magnetic field distribution. Furthermore, frequency B is set to the resonant frequency corresponding to the magnetic field strength of the static magnetic field in the second region Rb, which is included in a range where the magnetic field strength of the static magnetic field is lower than that of the first region Ra.

[0103] Based on this structure, by using an RF coil 220 that can be adjusted to two frequencies, A and B, NMR signals can be received from two regions, Ra and Rb, along the direction of the static magnetic field distribution. This expands the range of NMR signals that can be received along the direction of the static magnetic field distribution, and improves the sensitivity of the RF coil.

[0104] Furthermore, an example is given here of using an RF coil that can be adjusted to two frequencies to receive NMR signals at each frequency, but the number of frequencies is not limited to two; it can also be three or more. Therefore, it is possible to receive NMR signals from more than three regions along the direction of the static magnetic field distribution, further expanding the range of NMR signal reception.

[0105] For example, in this embodiment, the MRI apparatus 100 includes a transmitting coil configured to be adjustable to multiple frequencies and a receiving coil configured to be adjustable to multiple frequencies, as described above as the RF coil.

[0106] Figure 10 This is a diagram illustrating an example of the structure of the transmission and reception system included in the MRI apparatus 100 according to the second embodiment.

[0107] For example, such as Figure 10 As shown, the MRI device 100 includes: a transmitting coil 221 configured to be adjustable to frequencies A and B; and a receiving coil 222 configured to be adjustable to frequencies A and B.

[0108] The transmitting coil 221 transmits an RF signal of frequency A or B to the subject according to a control signal sent from the camera control function 17a of the processing circuit 17 via the processing circuit 15. The receiving coil 222 receives an NMR signal of frequency A or B generated from the subject according to a control signal sent from the camera control function 17a of the processing circuit 17 via the processing circuit 15.

[0109] Additionally, the MRI apparatus 100 includes a pulse generator 161, a DAC 162, a switching switch 163, a synthesizer 164, a first modulator 165a, a second modulator 165b, a first RF amplifier 266a, and a second RF amplifier 266b. For example, these devices are included in... Figure 1 The transmitting circuit 6 is shown.

[0110] The pulse generator 161, DAC 162, switching switch 163, synthesizer 164, first modulator 165a, and second modulator 165b are the same as in the first embodiment. The first RF amplifier 266a amplifies the RF pulse of frequency A generated by the first modulator 165a and outputs it to the transmitting coil 221. The second RF amplifier 266b amplifies the RF pulse of frequency B generated by the second modulator 165b and outputs it to the transmitting coil 221.

[0111] Additionally, the MRI apparatus 100 includes a first preamplifier 271a, a second preamplifier 271b, a first detector 172a, a second detector 172b, a first ADC 173a, and a second ADC 173b. For example, these devices are included in... Figure 1 The receiving circuit 7 is shown.

[0112] The first preamplifier 271a amplifies and outputs the NMR signal at frequency A received by the receiving coil 222. The second preamplifier 271b amplifies and outputs the NMR signal at frequency B received by the receiving coil 222. The first detector 172a, the second detector 172b, the first ADC 173a, and the second ADC 173b are the same as in the first embodiment.

[0113] Furthermore, the camera control function 17a controls the transmitting coil 221 by transmitting RF pulses at frequency A, and controls the receiving coil 222 by receiving NMR signals at frequency A. Additionally, the camera control function 17a controls the transmitting coil 221 by transmitting RF pulses at frequency B, and controls the receiving coil 222 by receiving NMR signals at frequency B.

[0114] With this structure, the camera control function 17a switches the frequency of the RF coil in a manner that receives NMR signals at various frequencies of multiple frequencies, and performs various camera operations.

[0115] In this case, the camera control function 17a controls the RF coil in the same way as in the first embodiment, switching the frequency when receiving NMR signals based on the frequency when transmitting RF pulses.

[0116] Specifically, the camera control function 17a controls the RF coil in the same way as in the first embodiment, switching the frequency when receiving NMR signals based on the position of the camera slice.

[0117] For example, the camera control function 17a, similar to the first embodiment, controls the RF coil by sequentially transmitting RF pulses at each of the multiple frequencies and sequentially receiving NMR signals at each of the multiple frequencies.

[0118] As described above, in the second embodiment, the MRI apparatus 100 includes an RF coil configured to be adjustable to multiple frequencies, and the camera control function 17a switches the frequency of the RF coil in a manner that receives NMR signals at each of the multiple frequencies.

[0119] Based on this structure, similar to the first embodiment, when the magnetic field strength of the static magnetic field varies in space, the range of NMR signals that can be received can be expanded by using multiple frequencies, and the sensitivity of the RF coil can be improved.

[0120] (Third Implementation)

[0121] Furthermore, in the first embodiment described above, an example was given in which the camera control function 17a controls the RF coil by sequentially transmitting RF pulses at various frequencies and sequentially receiving NMR signals at various frequencies, but the embodiment is not limited to this. For example, the camera control function 17a may also transmit RF pulses in a wide bandwidth including multiple frequencies. Hereinafter, such an example will be described as a third embodiment.

[0122] In this embodiment, the camera control function 17a controls the RF coil in such a way that it transmits RF pulses in a frequency band that includes multiple frequencies and simultaneously receives NMR signals at each of the multiple frequencies.

[0123] For example, in this embodiment, the MRI apparatus 100 includes a transmitting coil for transmitting RF pulses and a plurality of receiving coils for receiving NMR signals, as described above, the RF coil.

[0124] Figure 11 This is a diagram illustrating an example of the structure of the transmission and reception system included in the MRI apparatus 100 according to the third embodiment.

[0125] For example, such as Figure 11 As shown, the MRI device 100 has a transmitting coil 321 that is adjusted to include a frequency band including frequencies A and B, a first receiving coil 122a that is adjusted to frequency A, and a second receiving coil 122b that is adjusted to frequency B.

[0126] The transmitting coil 321 transmits an RF signal to the subject in a frequency band including frequencies A and B, according to a control signal sent from the camera control function 17a of the processing circuit 17 via the processing circuit 15. The first receiving coil 122a and the second transmitting coil 121b are the same as in the first embodiment.

[0127] Additionally, the MRI apparatus 100 includes a pulse generator 161, a DAC 162, a modulator 365, and an RF amplifier 366. For example, these devices are included in... Figure 1 The transmitting circuit 6 is shown.

[0128] The pulse generator 161, DAC 162, and synthesizer 164 are the same as in the first embodiment. After converting the frequency of the RF signal output from synthesizer 164 to frequency A, modulator 365 modulates the RF signal with the waveform of the digital signal output from DAC 162, thereby generating an RF pulse in a frequency band including frequencies A and B. RF amplifier 366 amplifies the RF pulse in the frequency band including frequencies A and B generated by modulator 365 and outputs it to transmitting coil 321.

[0129] Additionally, the MRI apparatus 100 includes a first preamplifier 171a, a second preamplifier 171b, a first detector 172a, a second detector 172b, a first ADC 173a, and a second ADC 173b. For example, these devices are included in... Figure 1 The receiving circuit 7 is shown.

[0130] The first preamplifier 171a, the second preamplifier 171b, the first detector 172a, the second detector 172b, the first ADC 173a, and the second ADC 173b are the same as in the first embodiment.

[0131] Furthermore, the camera control function 17a controls the transmitting coil 321 to transmit RF pulses in a frequency band including frequencies A and B. Additionally, the camera control function 17a controls the first receiving coil 122a to receive NMR signals at frequency A, and controls the second receiving coil 122b to receive NMR signals at frequency B.

[0132] At this time, the camera control function 17a controls the transmission coil 321 to transmit RF pulses, so that both the first receiving coil 122a and the second receiving coil 122b are in a decoupled state.

[0133] Furthermore, when the first receiving coil 122a and the second receiving coil 122b receive NMR signals, the camera control function 17a controls them to ensure that each receiving coil can receive signals simultaneously. Additionally, at this time, the camera control function 17a controls both the first transmitting coil 121a and the second transmitting coil 121b to be in a decoupled state.

[0134] With this structure, the camera control function 17a controls the RF coil and performs various imaging operations in the following manner: transmitting RF pulses in a frequency band that includes multiple frequencies, and simultaneously receiving NMR signals at each of the multiple frequencies.

[0135] For example, camera control function 17a uses multiple receiving coils tuned to different frequencies to perform parallel imaging. Here, for example, the multiple receiving coils are multiple coil elements included in a phased array coil.

[0136] In this case, the frequency of each receiving coil is adjusted to a resonant frequency corresponding to the magnetic field strength of the static magnetic field at the location of each coil. Furthermore, the camera control function 17a controls the transmitting coil to transmit RF pulses in a frequency band encompassing the frequencies of each receiving coil, and controls multiple receiving coils to simultaneously receive NMR signals at various frequencies.

[0137] In parallel imaging, an image is generated by combining NMR signals received from multiple receiving coils, and then unfolding this image to produce an image without reflections. Typically, the SNR (Signal-to-Noise Ratio) is used in parallel imaging. parallel It is represented by the following formula.

[0138]

[0139] Here, SNR refers to the SNR without parallel imaging, g is the g-factor, and R is the rate multiplier. Among these parameters, the g-factor is a factor that affects image quality. The higher the independence of the sensitivity distribution of each receiving coil, the smaller the g-factor, and consequently, the higher the image quality.

[0140] In this embodiment, by receiving NMR signals at various frequencies across multiple frequencies, a frequency-dependent sensitivity distribution is generated in addition to the usual sensitivity distribution of the receiving coils, thus further enhancing the independence of the sensitivity distribution of each receiving coil. As a result, the value of the g-factor decreases, improving the image quality generated by parallel imaging.

[0141] As described above, in the third embodiment, the camera control function 17a controls the RF coil to transmit RF pulses in a frequency band that includes multiple frequencies, and simultaneously receive NMR signals at each of the multiple frequencies.

[0142] Based on this structure, similar to the first embodiment, when the magnetic field strength of the static magnetic field varies in space, the range of NMR signals that can be received can be expanded by using multiple frequencies, and the sensitivity of the RF coil can be improved.

[0143] Furthermore, in the third embodiment, the image quality of the image generated by parallel imaging can be improved.

[0144] (Fourth Implementation)

[0145] Furthermore, the second embodiment described above illustrates an example using multiple modulators and multiple detectors, but the implementation is not limited to this. For example, it is also possible to... Figure 10 In the structure of the transmission and reception system shown, the modulator and detector are common by using a modulator and detector that can be switched to multiple frequencies. Hereinafter, such an example will be described as a fourth embodiment.

[0146] Figure 12 This is a diagram illustrating an example of the structure of the transmission and reception system included in the MRI apparatus 100 according to the fourth embodiment.

[0147] For example, such as Figure 12 As shown, the MRI device 100 includes: a transmitting coil 221 configured to be adjustable to frequencies A and B; and a receiving coil 222 configured to be adjustable to frequencies A and B.

[0148] The transmitting coil 221 and the receiving coil 222 are the same as in the second embodiment.

[0149] Additionally, the MRI apparatus 100 includes a pulse generator 161, a DAC 162, a synthesizer 164, a modulator 465, a switching switch 467, a first RF amplifier 266a, and a second RF amplifier 266b. For example, these devices are included in... Figure 1 The transmitting circuit 6 is shown.

[0150] The pulse generator 161, DAC 162, and synthesizer 164 are the same as in the first embodiment. After the modulator 465 converts the frequency of the RF signal output from the synthesizer 164 to frequencies A and B respectively, it modulates the RF signal using the waveform of the digital signal output from the DAC 162, thereby generating RF pulses of frequency A and frequency B. The switch 467, according to the control signal sent from the camera control function 17a of the processing circuit 17 via the processing circuit 15, outputs the RF pulse of frequency A generated by the modulator 465 to the first RF amplifier 266a, or outputs the RF pulse of frequency B generated by the modulator 465 to the second RF amplifier 266b. The first RF amplifier 266a and the second RF amplifier 266b are the same as in the second embodiment.

[0151] Additionally, the MRI device 100 includes a first preamplifier 271a, a second preamplifier 271b, a switching switch 474, a detector 472, and an ADC 473. For example, these devices are included in... Figure 1 The receiving circuit 7 is shown.

[0152] The first preamplifier 271a and the second preamplifier 271b are the same as in the second embodiment. The switch 474 outputs an NMR signal at frequency A from the first preamplifier 271a or an NMR signal at frequency B from the second preamplifier 271b to the detector 472 based on a control signal sent from the camera control function 17a of the processing circuit 17 via the processing circuit 15. The detector 472, after converting the frequency of the RF signal output from the synthesizer 164 to frequencies A and B respectively, uses this RF signal to detect and output the NMR signal output from the switch 474. The ADC 473 converts the NMR signal output from the detector 472 from an analog signal to a digital signal, thereby generating NMR data, and outputs the generated NMR data to the processing circuit 15.

[0153] Furthermore, the camera control function 17a controls the transmitting coil 221 and the receiving coil 222 in the same manner as in the second embodiment.

[0154] (Fifth Implementation)

[0155] Furthermore, the first embodiment described above illustrates an example where multiple modulators and multiple detectors are used in the same manner as in the second embodiment, but the embodiment is not limited to this. For example, it is also possible to... Figure 7 In the structure of the transmission and reception system shown, a modulator and detector capable of switching to multiple frequencies are used in the same way as in the fourth embodiment, thereby making the modulator and detector common. Hereinafter, such an example will be described as the fifth embodiment.

[0156] Figure 13 This is a diagram illustrating an example of the structure of the transmission and reception system included in the MRI apparatus 100 according to the fifth embodiment.

[0157] For example, such as Figure 13 As shown, the MRI device 100 has a first transmitting coil 121a and a first receiving coil 122a adjusted to frequency A, and a second transmitting coil 121b and a second receiving coil 122b adjusted to frequency B.

[0158] The first transmitting coil 121a, the first receiving coil 122a, the second transmitting coil 121b, and the second receiving coil 122b are the same as in the first embodiment.

[0159] Additionally, the MRI apparatus 100 includes a pulse generator 161, a DAC 162, a synthesizer 164, a modulator 465, a switching switch 467, a first RF amplifier 166a, and a second RF amplifier 166b. For example, these devices are included in... Figure 1 The transmitting circuit 6 is shown.

[0160] The pulse generator 161, DAC 162, synthesizer 164, first RF amplifier 166a, and second RF amplifier 166b are the same as in the first embodiment. The modulator 465 and the switching switch 467 are the same as in the fourth embodiment.

[0161] Additionally, the MRI device 100 includes a first preamplifier 171a, a second preamplifier 171b, a switching switch 474, a detector 472, and an ADC 473. For example, these devices are included in... Figure 1 The receiving circuit 7 is shown.

[0162] The first preamplifier 171a and the second preamplifier 171b are the same as in the first embodiment. The switching switch 474, the detector 472, and the ADC 473 are the same as in the fourth embodiment.

[0163] Furthermore, the camera control function 17a controls the first transmitting coil 121a, the second transmitting coil 121b, the first receiving coil 122a, and the second receiving coil 122b in the same manner as in the first embodiment.

[0164] (Sixth Implementation Method)

[0165] Furthermore, while the first embodiment described above illustrates an example using multiple transmitting coils and multiple receiving coils, the implementation is not limited to this. For example, it is also possible to... Figure 7 In the structure of the transmission and reception system shown, multiple transmission and reception coils are used instead of multiple transmission coils and multiple reception coils. Hereinafter, such an example will be described as the sixth embodiment.

[0166] Figure 14 This is a diagram illustrating an example of the structure of the transmission and reception system included in the MRI apparatus 100 according to the sixth embodiment.

[0167] For example, such as Figure 14 As shown, the MRI apparatus 100 has a first transmit / receive coil 623a adjusted to frequency A and a second transmit / receive coil 623b adjusted to frequency B.

[0168] The first transmitting / receiving coil 623a transmits an RF signal of frequency A to the subject and receives an NMR signal of frequency A generated by the subject, based on a control signal sent from the camera control function 17a of the processing circuit 17 via the processing circuit 15. The second transmitting / receiving coil 623b transmits an RF signal of frequency B to the subject and receives an NMR signal of frequency B generated by the subject, based on a control signal sent from the camera control function 17a of the processing circuit 17 via the processing circuit 15.

[0169] Additionally, the MRI apparatus 100 includes a pulse generator 161, a DAC 162, a switching switch 163, a synthesizer 164, a first modulator 165a, a second modulator 165b, a first RF amplifier 666a, and a second RF amplifier 666b. For example, these devices are included in... Figure 1 The transmitting circuit 6 is shown.

[0170] The pulse generator 161, DAC 162, switch 163, synthesizer 164, first modulator 165a, and second modulator 165b are the same as in the first embodiment. The first RF amplifier 666a amplifies the RF pulse of frequency A generated by the first modulator 165a and outputs it to the first transmit / receive coil 623a. The second RF amplifier 666b amplifies the RF pulse of frequency B generated by the second modulator 165b and outputs it to the second transmit / receive coil 623b.

[0171] Additionally, the MRI device 100 includes a first preamplifier 671a, a second preamplifier 671b, a first detector 172a, a second detector 172b, a first ADC 173a, and a second ADC 173b. For example, these devices are included in... Figure 1 The receiving circuit 7 is shown.

[0172] The first preamplifier 671a amplifies and outputs the NMR signal at frequency A received by the first transmit / receive coil 623a. The second preamplifier 671b amplifies and outputs the NMR signal at frequency B received by the second transmit / receive coil 623b. The first detector 172a, the second detector 172b, the first ADC 173a, and the second ADC 173b are the same as in the first embodiment.

[0173] Furthermore, the camera control function 17a controls the first transmitting / receiving coil 623a by transmitting RF pulses at frequency A, and also controls the first transmitting / receiving coil 623a by receiving NMR signals at frequency A. Additionally, the camera control function 17a controls the second transmitting / receiving coil 623b by transmitting RF pulses at frequency B, and also controls the second transmitting / receiving coil 623b by receiving NMR signals at frequency B.

[0174] At this time, when one of the first transmitting / receiving coils 623a and the second transmitting / receiving coil 623b transmits an RF pulse, the camera control function 17a controls the other transmitting / receiving coil in a decoupled state.

[0175] In addition, when the first transmitting and receiving coil 623a and the second transmitting and receiving coil 623b receive NMR signals, the camera control function 17a controls the signal so that each transmitting and receiving coil can receive simultaneously.

[0176] (Seventh Implementation)

[0177] Furthermore, in the sixth embodiment described above, an example was given in which multiple modulators and multiple detectors were used in the same manner as in the first embodiment, but the embodiments are not limited to this. For example, it is also possible to... Figure 14In the structure of the transmission and reception system shown, a modulator and detector capable of switching to multiple frequencies are used in the same way as in the fourth embodiment, thereby making the modulator and detector common. Hereinafter, such an example will be described as the seventh embodiment.

[0178] Figure 15 This is a diagram illustrating an example of the structure of the transmission and reception system included in the MRI apparatus 100 according to the seventh embodiment.

[0179] For example, such as Figure 15 As shown, the MRI apparatus 100 has a first transmit / receive coil 623a adjusted to frequency A and a second transmit / receive coil 623b adjusted to frequency B.

[0180] The first transmitting / receiving coil 623a and the second transmitting / receiving coil 623b are the same as in the sixth embodiment.

[0181] Additionally, the MRI apparatus 100 includes a pulse generator 161, a DAC 162, a synthesizer 164, a modulator 465, a switching switch 467, a first RF amplifier 666a, and a second RF amplifier 666b. For example, these devices are included in... Figure 1 The transmitting circuit 6 is shown.

[0182] The pulse generator 161, DAC 162, and synthesizer 164 are the same as in the first embodiment. The modulator 465 and switch 467 are the same as in the fourth embodiment. The first RF amplifier 666a and the second RF amplifier 666b are the same as in the sixth embodiment.

[0183] Additionally, the MRI device 100 includes a first preamplifier 671a, a second preamplifier 671b, a switching switch 474, a detector 472, and an ADC 473. For example, these devices are included in... Figure 1 The receiving circuit 7 is shown.

[0184] The first preamplifier 671a and the second preamplifier 671b are the same as in the sixth embodiment. The switch 474, detector 472, and ADC 473 are the same as in the fourth embodiment.

[0185] Furthermore, the camera control function 17a controls the first transmitting / receiving coil 623a and the second transmitting / receiving coil 623b in the same manner as in the sixth embodiment.

[0186] (Eighth Implementation Method)

[0187] Furthermore, in the second embodiment described above, an example was given using a transmitting coil configured to be adjustable to multiple frequencies and a receiving coil configured to be adjustable to multiple frequencies, but the embodiments are not limited to this. For example, it is also possible to... Figure 10 In the structure of the transmission and reception system shown, a single transmission and reception coil, configured to be adjustable to multiple frequencies, is used instead of a single transmission coil and a single reception coil. Hereinafter, such an example will be described as the eighth embodiment.

[0188] Figure 16 This is a diagram illustrating an example of the structure of the transmission and reception system included in the MRI apparatus 100 according to the eighth embodiment.

[0189] For example, such as Figure 16 As shown, the MRI device 100 has a transmitting and receiving coil 823 configured to be adjustable to frequencies A and B.

[0190] The transceiver coil 823 transmits an RF signal of frequency A or B to the subject according to a control signal sent from the camera control function 17a of the processing circuit 17 via the processing circuit 15. Additionally, the transceiver coil 823 receives an NMR signal of frequency A or B generated from the subject according to a control signal sent from the camera control function 17a of the processing circuit 17 via the processing circuit 15.

[0191] Additionally, the MRI apparatus 100 includes a pulse generator 161, a DAC 162, a switching switch 163, a synthesizer 164, a first modulator 165a, a second modulator 165b, a first RF amplifier 866a, and a second RF amplifier 866b. For example, these devices are included in... Figure 1 The transmitting circuit 6 is shown.

[0192] The pulse generator 161, DAC 162, switch 163, synthesizer 164, first modulator 165a, and second modulator 165b are the same as in the first embodiment. The first RF amplifier 866a amplifies the RF pulse of frequency A generated by the first modulator 165a and outputs it to the transmit / receive coil 823. The second RF amplifier 866b amplifies the RF pulse of frequency B generated by the second modulator 165b and outputs it to the transmit / receive coil 823.

[0193] Additionally, the MRI device 100 includes a first preamplifier 871a, a second preamplifier 871b, a first detector 172a, a second detector 172b, a first ADC 173a, and a second ADC 173b. For example, these devices are included in... Figure 1 The receiving circuit 7 is shown.

[0194] The first preamplifier 871a amplifies and outputs the NMR signal at frequency A received by the transmit / receive coil 823. The second preamplifier 871b amplifies and outputs the NMR signal at frequency B received by the transmit / receive coil 823. The first detector 172a, the second detector 172b, the first ADC 173a, and the second ADC 173b are the same as in the first embodiment.

[0195] Furthermore, the camera control function 17a controls the transmit / receive coil 823 by transmitting RF pulses at frequency A and by receiving NMR signals at frequency A. Additionally, the camera control function 17a controls the transmit / receive coil 823 by transmitting RF pulses at frequency B and by receiving NMR signals at frequency B.

[0196] (Ninth Implementation)

[0197] Furthermore, in the eighth embodiment described above, an example was given in which multiple modulators and multiple detectors were used in the same manner as in the first embodiment, but the embodiments are not limited to this. For example, in Figure 16 In the structure of the transmission and reception system shown, a modulator and detector capable of switching to multiple frequencies can also be used in the same way as in the fourth embodiment, thereby making the modulator and detector common. Hereinafter, such an example will be described as the ninth embodiment.

[0198] Figure 17 This is a diagram illustrating an example of the structure of the transmission and reception system included in the MRI apparatus 100 according to the ninth embodiment.

[0199] For example, such as Figure 17 As shown, the MRI device 100 has a transmitting and receiving coil 823 configured to be adjustable to frequencies A and B.

[0200] The transmitting and receiving coil 823 is the same as in the eighth embodiment.

[0201] Additionally, the MRI apparatus 100 includes a pulse generator 161, a DAC 162, a synthesizer 164, a modulator 465, a switching switch 467, a first RF amplifier 866a, and a second RF amplifier 866b. For example, these devices are included in... Figure 1 The transmitting circuit 6 is shown.

[0202] The pulse generator 161, DAC 162, and synthesizer 164 are the same as in the first embodiment. The modulator 465 and switch 467 are the same as in the fourth embodiment. The first RF amplifier 866a and the second RF amplifier 866b are the same as in the eighth embodiment.

[0203] Additionally, the MRI device 100 includes a first preamplifier 871a, a second preamplifier 871b, a switching switch 474, a detector 472, and an ADC 473. For example, these devices are included in... Figure 1 The receiving circuit 7 is shown.

[0204] The first preamplifier 871a and the second preamplifier 871b are the same as in the eighth embodiment. The switch 474, detector 472, and ADC 473 are the same as in the fourth embodiment.

[0205] Furthermore, the camera control function 17a controls the transmitting and receiving coil 823 in the same way as in the eighth embodiment.

[0206] The first to ninth embodiments have been described above.

[0207] In the above embodiments, in the first, third, fifth to seventh embodiments, as a structure for receiving NMR signals at each of the multiple frequencies, multiple RF coils (receiving coils or transmitting / receiving coils) are used, each of the multiple frequencies individually adjusted to its respective frequency.

[0208] With this structure, each RF coil receives the NMR signal within a narrow frequency band centered on a predetermined frequency. Therefore, compared to using RF coils (receiving coils or transmitting / receiving coils) configured to be adjustable to multiple frequencies, noise mixed into the NMR signal can be reduced. Consequently, compared to using RF coils configured to be adjustable to multiple frequencies, the image quality of the captured image can be improved. Furthermore, compared to using RF coils configured to be adjustable to multiple frequencies, the receiving system can be implemented with a simpler circuit structure.

[0209] (Other implementation methods)

[0210] Furthermore, in the above embodiments, an MRI apparatus 100 with a so-called tunnel-type structure was described, but the embodiments are not limited thereto. The so-called tunnel-type structure refers to the static magnetic field magnet 1, the gradient magnetic field coil 2, and the whole-body RF coil 4 each being formed in a generally cylindrical shape. For example, the technology disclosed in this application can also be similarly applied to an MRI apparatus with 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 opposite each other, separated by the imaging space where the subject S is positioned. That is, regarding the technology disclosed in this application, any MRI apparatus having a static magnetic field magnet that generates a static magnetic field with spatially varying magnetic field strength can be applied to various MRI apparatuses, where the static magnetic field magnet generates a static magnetic field with spatially varying magnetic field strength in at least a portion of the imaging space where the subject is positioned.

[0211] Furthermore, in the above embodiments, examples have been described in which the control unit in this specification is implemented by the camera control function 17a of the processing circuit 17, but the embodiments are not limited to this. For example, in addition to being implemented by the camera control function 17a described in the embodiments, the control unit in this specification may also be implemented by hardware only, by software only, or by a combination of hardware and software to achieve the same function.

[0212] Furthermore, while the above description illustrates an example of a "processor" reading and executing programs corresponding to each processing function from a storage circuit, the implementation is not limited to this. The term "processor" refers to circuits such as CPU (Central Processing Unit), GPU (Graphics Processing Unit), Application Specific Integrated Circuit (ASIC), and programmable logic devices (e.g., Light Programmable Logic Device (SPLD), Complex Programmable Logic Device (CPLD), and Field Programmable Gate Array (FPGA)). In the case of a CPU, the processor reads and executes the program stored in the storage circuit, thereby implementing each processing function. On the other hand, in the case of an ASIC, instead of storing the program in the storage circuit, the processing function is directly loaded as logic circuitry into the processor's circuitry. Furthermore, the processors in this embodiment are not limited to being configured as a single circuit for each processor; multiple independent circuits can be combined to form a single processor to implement its processing functions. Moreover, it is also possible to... Figure 1 Multiple components are integrated into a single processor to perform its processing functions.

[0213] Here, the program executed by the processor is provided pre-assembled in ROM (Read Only Memory) or storage circuitry. The program can also be provided as a file, stored on computer-readable storage media such as CD-ROM, FD (Flexible Disk), CD-R (Recordable), or DVD (Digital Versatile Disk), capable of being installed or executed on these devices. Alternatively, the program can be stored on a computer connected to a network such as the Internet and provided or distributed via network download. For example, the program consists of modules containing the aforementioned functional units. As actual hardware, the CPU reads the program from the storage medium such as ROM and executes it, thereby loading the modules onto the main storage device, where they are generated.

[0214] According to at least one embodiment described above, the sensitivity of the RF coil can be improved when the magnetic field strength of the static magnetic field varies in space.

[0215] Several embodiments have been described, but these embodiments are given by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, modifications, and combinations of embodiments are possible within the scope of the invention as defined in the appended claims.

Claims

1. A magnetic resonance imaging device, comprising: A static magnetic field magnet produces a static magnetic field whose magnetic field strength varies in space. Multiple transmitting coils are individually adjusted to each of multiple frequencies, which are adjusted at least according to the distribution of the static magnetic field, and high-frequency pulses are transmitted to the subject placed in the static magnetic field where the magnetic field strength varies in space. A receiving coil receives the nuclear magnetic resonance signal generated from the subject due to the influence of the high-frequency pulse; as well as The control unit controls each of the plurality of transmitting coils in a manner that transmits the high-frequency pulses at each of the plurality of frequencies, and controls the receiving coil in a manner that receives the nuclear magnetic resonance signal at each of the plurality of frequencies.

2. The magnetic resonance imaging device according to claim 1, The magnetic resonance imaging apparatus includes multiple receiving coils that are tuned to various frequencies of the plurality of frequencies.

3. The magnetic resonance imaging device according to claim 1 or 2, The control unit controls the receiving coil by switching the frequency of receiving the nuclear magnetic resonance signal based on the frequency when transmitting the high-frequency pulse.

4. The magnetic resonance imaging device according to claim 1 or 2, The control unit controls the receiving coil by switching the frequency of receiving the nuclear magnetic resonance signal based on the position of the image slice.

5. The magnetic resonance imaging apparatus according to claim 1 or 2, The control unit controls each of the plurality of transmitting coils to transmit the high-frequency pulses sequentially at each of the plurality of frequencies, and controls the receiving coil to receive the nuclear magnetic resonance signal sequentially at each of the plurality of frequencies.

6. The magnetic resonance imaging apparatus according to claim 1 or 2, The control unit controls each of the plurality of transmitting coils in a manner that transmits the high-frequency pulses in a frequency band that includes the plurality of frequencies, and controls the receiving coil in a manner that simultaneously receives the nuclear magnetic resonance signal at each of the plurality of frequencies.

7. The magnetic resonance imaging apparatus according to claim 1 or 2, The control unit controls the transmission in such a way that when one of the plurality of transmitting coils transmits the high-frequency pulse, the other transmitting coils are in a decoupled state.

8. The magnetic resonance imaging device according to claim 2, The control unit controls the multiple receiving coils to be in a decoupled state when the multiple transmitting coils transmit the high-frequency pulses respectively.

9. The magnetic resonance imaging apparatus according to claim 2 or 8, The control unit controls the system so that each receiving coil is capable of receiving the nuclear magnetic resonance signal simultaneously when the plurality of receiving coils receive the signal.

10. The magnetic resonance imaging apparatus according to claim 1 or 2, The static magnetic field whose magnetic field strength varies in space is a static magnetic field that governs the region where the magnetic field strength decreases as one moves away from the static magnetic field magnet.

11. The magnetic resonance imaging apparatus according to claim 1 or 2, The static magnetic field whose magnetic field strength varies in space is a static magnetic field that governs the region outside the uniform region where the magnetic field strength is uniform.

12. The magnetic resonance imaging apparatus according to claim 1 or 2, The static magnetic field whose magnetic field strength varies in space is a static magnetic field that stably forms a region with uneven magnetic field strength.

13. A magnetic resonance imaging method, comprising the following steps: A static magnetic field magnet generates a static magnetic field whose magnetic field strength varies in space. Multiple transmitting coils are individually adjusted to each of multiple frequencies, at least according to the distribution of the static magnetic field, and high-frequency pulses are transmitted to the subject placed within the static magnetic field in which the magnetic field strength varies spatially. The receiving coil receives the nuclear magnetic resonance signal generated from the subject due to the influence of the high-frequency pulse; as well as The control unit controls each of the plurality of transmitting coils in a manner that transmits the high-frequency pulses at each of the plurality of frequencies, and controls the receiving coil in a manner that receives the nuclear magnetic resonance signal at each of the plurality of frequencies.

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