Magnetic Resonance Imaging System
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- CANON KK
- Filing Date
- 2022-03-29
- Publication Date
- 2026-08-03
Smart Images
Figure 0007898894000001 
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Abstract
Description
Technical Field
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[0001] Embodiments of the present invention relate to a magnetic resonance imaging apparatus.
Background Art
[0002] Conventionally, a magnetic resonance imaging (MRI) apparatus has been used as a medical diagnostic apparatus for performing diagnosis based on images. A magnetic resonance imaging apparatus (hereinafter referred to as an "MRI apparatus") is an apparatus that captures a tomographic image of a subject by receiving an MR signal excited by an RF (Radio Frequency) pulse irradiated in a strong magnetic field with an RF coil. In recent years, in an MRI apparatus, consideration has been given to making the RF coil attached to the subject wireless.
[0003] By the way, when making the RF coil wireless, in order to synchronize the clock signal in this wireless RF coil with the system clock signal of the main body of the MRI apparatus, it becomes necessary to wirelessly transmit the clock signal from the main body side to the wireless RF coil side. However, in principle, an MRI apparatus irradiates a strong RF pulse. Therefore, it is conceivable that the irradiated RF pulse affects the clock signal transmitted wirelessly, and the synchronization of the clock signal is lost in the wireless RF coil, or the fluctuation (jitter) of the clock signal increases.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0006] The magnetic resonance imaging apparatus of this embodiment includes a transmitting coil, a receiving coil, and a control unit. The transmitting coil irradiates a subject with RF pulses. The receiving coil receives magnetic resonance signals from the subject. The control unit controls the transmitting coil and the receiving coil. The receiving coil includes a clock receiving unit, a phase synchronization unit, and a phase synchronization control unit. The clock receiving unit receives a clock signal transmitted wirelessly by the control unit. The phase synchronization unit performs phase synchronization with the clock signal. The phase synchronization control unit controls the phase synchronization unit. The phase synchronization control unit switches the operating state of the phase synchronization unit according to the irradiation timing of the RF pulses. [Brief explanation of the drawing]
[0007] [Figure 1] A diagram showing an example of the configuration of a magnetic resonance imaging apparatus according to the embodiment. [Figure 2] A diagram showing an example of the configuration and connection of a wireless RF coil according to the embodiment. [Figure 3] This figure shows an example of a first control method for a phase-locking circuit in a sequence execution circuit provided in a wireless RF coil according to an embodiment. [Figure 4] This figure shows an example of a second control method for a phase-locking circuit in a sequence execution circuit provided in a wireless RF coil according to an embodiment. [Figure 5] This figure shows an example of a third control method for the phase-locking circuit in the sequence execution circuit of the wireless RF coil according to the embodiment. [Figure 6]A diagram showing another example of the configuration and connection of the wireless RF coil according to the embodiment. [Modes for carrying out the invention]
[0008] The magnetic resonance imaging apparatus of this embodiment will be described below with reference to the drawings.
[0009] A Magnetic Resonance Imaging (MRI) device (hereinafter referred to as "MRI device") is a medical diagnostic device that applies a strong magnetic field to a subject (e.g., the human body) and irradiates it with RF (Radio Frequency) pulses. Electromagnetic waves generated from hydrogen nuclei within the subject's body due to the nuclear magnetic resonance phenomenon are received by an RF coil. The device then reconstructs the nuclear magnetic resonance signal (hereinafter referred to as "MR signal") based on the received electromagnetic waves to capture a tomographic image (hereinafter referred to as "MR image"). An MRI device can also capture an MR image of a subject by reconstructing the MR signal based on the electromagnetic waves received by a wireless RF coil attached to the subject. By displaying the subject's MR image, the MRI device allows the person performing the MRI examination (such as a doctor or technician) to visually confirm whether or not there are lesions in the subject.
[0010] Figure 1 shows an example of the configuration of a magnetic resonance imaging (MRI) apparatus according to an embodiment. The MRI apparatus 1 comprises, for example, a pedestrian stand 10, a patient bed 20, a control device 30, and a console device 40. In this embodiment, the control device 30 and the console device 40 are described as being separate from the pedestrian stand 10, but the pedestrian stand 10 may include some or all of the components of the control device 30 and the console device 40. The MRI apparatus 1 is an example of a "magnetic resonance imaging apparatus".
[0011] The mounting device 10 includes, for example, a static magnetic field magnet 12, a gradient magnetic field coil 14, and an RF coil 16. Furthermore, the mounting device 10 includes, for example, a wireless RF coil 18 (hereinafter referred to as "wireless RF coil 18") that can be attached to the subject P as a component of the RF coil 16.
[0012] The static magnetic field magnet 12 is a magnet formed in a hollow, approximately cylindrical shape. The static magnetic field magnet 12 generates a uniform static magnetic field in its internal space. The static magnetic field magnet 12 can be, for example, a permanent magnet or a superconducting magnet. If the static magnetic field magnet 12 is a superconducting magnet, it generates a static magnetic field by receiving power from a static magnetic field power source (not shown).
[0013] The gradient coil 14 is a hollow, substantially cylindrical coil. The gradient coil 14 is placed inside the static magnetic field magnet 12. The gradient coil 14 is formed by combining three coils corresponding to the mutually orthogonal X, Y, and Z axes. Each of the three coils corresponding to the direction of each axis receives current individually from the gradient power supply 33, generating a gradient magnetic field in the imaging space of the MRI device 1 into which the subject P is introduced, with the magnetic field strength changing along the X, Y, and Z axes. In this embodiment, the central axis of the rigging device 10 or the longitudinal direction of the top plate 24 of the patient device 20 is defined as the Z-axis direction, the axis horizontal to the floor of the room in which the MRI device 1 is installed is defined as the X-axis direction, the axis perpendicular to the Z-axis direction is defined as the X-axis direction, the axis perpendicular to the Z-axis direction is defined as the X-axis direction, the axis perpendicular to the floor is defined as the Z-axis direction, and the direction perpendicular to the floor is defined as the Y-axis direction. In this embodiment, the Z-axis direction is the same direction as the static magnetic field.
[0014] Here, the gradient magnetic fields generated by the gradient coil 14 along the X, Y, and Z axes correspond to, for example, a slice selection gradient magnetic field, a phase encoding gradient magnetic field, and a readout gradient magnetic field, respectively. The slice selection gradient magnetic field is used to determine an arbitrary imaging cross-section in the MRI device 1. The phase encoding gradient magnetic field is used to change the phase of the MR signal according to the spatial position in the MRI device 1. The readout gradient magnetic field is used to change the frequency of the MR signal according to the spatial position in the MRI device 1.
[0015] The RF coil 16 is a whole-body coil housed within the rigging device 10 and configured to surround the subject P in the imaging space. The RF coil 16 receives RF pulses from the transmitting circuit 34 and generates a high-frequency magnetic field. The RF coil 16 receives MR signals emitted from the subject P due to the influence of the high-frequency magnetic field. Upon receiving an MR signal, the RF coil 16 outputs the received MR signal to the receiving circuit 35. The RF coil 16 may transmit RF pulses and receive MR signals using different RF coil configurations, or it may use the same RF coil configuration, i.e., a configuration for both transmission and reception. The RF coil 16 may be, for example, a coil array composed of multiple coil elements. The RF coil 16 is an example of a "transmitting coil".
[0016] The wireless RF coil 18 is a wireless local coil attached to the subject P. The wireless RF coil 18 comes in various shapes depending on the imaging area of the subject P. Figure 1 shows an example of a wireless RF coil 18 attached to the torso of the subject P. The wireless RF coil 18 receives the MR signal emitted from the subject P due to the influence of the high-frequency magnetic field generated by the RF coil 16, and transmits data representing the received MR signal (hereinafter referred to as "MR data") to the transmitting / receiving circuit 36. The wireless RF coil 18 may also be, for example, a coil array composed of multiple coil elements. The wireless RF coil 18 is an example of a "receiving coil".
[0017] The patient bed device 20 is a device that places and moves the subject P to be photographed and introduces it into the interior of the pedestal device 10 (into the cavity of the static magnetic field magnet 12, gradient magnetic field coil 14, and RF coil 16, i.e., inside the imaging port). The patient bed device 20 comprises, for example, a base 22 and a top plate 24.
[0018] The base 22 moves the top plate 24 on which the subject P is placed in the vertical direction (Y-axis direction) or the longitudinal direction (Z-axis direction) of the top plate 24 by the operation of a bed driving device (not shown) that operates according to the control signal output by the bed control circuit 37. The base 22 includes a housing that supports the top plate 24 movably. The bed driving device (not shown) includes, for example, a motor and an actuator. The bed driving device (not shown) may move not only the top plate 24 but also the base 22 itself in the longitudinal direction of the top plate 24. When the gantry device 10 is configured to be movable in the Z-axis direction, the bed driving device (not shown) may operate to move the gantry device 10 so that the subject P is introduced into the gantry device 10. When both the gantry device 10 and the top plate 24 and the base 22 are configured to be movable, the bed driving device (not shown) may operate to move each of the gantry device 10, the top plate 24, and the base 22 so that the subject P is introduced into the gantry device 10. The top plate 24 is a plate-like member on which the subject P is placed.
[0019] The control device 30 controls the operations of the gantry device 10 and the bed device 20 according to the control from the console device 40. The control device 30 includes, for example, a clock generation circuit 31, a sequence control circuit 32, an inclination magnetic field power supply 33, a transmission circuit 34, a reception circuit 35, a transmission / reception circuit 36, and a bed control circuit 37. The control device 30 may be provided inside the gantry device 10 or may be provided inside the console device 40. The control device 30 is an example of a "control unit".
[0020] The clock generation circuit 31 generates a clock signal that serves as a reference for the operation of imaging the subject P in the MRI apparatus 1. The clock generation circuit 31 includes, for example, a clock oscillator. The clock generation circuit 31 outputs the generated clock signal to each component.
[0021] The sequence control circuit 32 is a sequencer that performs imaging of the subject P by driving the gradient magnetic field power supply 33, the transmission circuit 34, and the reception circuit 35 based on the sequence information set by the console device 40. The sequence control circuit 32 may be a processing circuit having a processor such as a CPU (Central Processing Unit), for example. The sequence information is information in which procedures for performing imaging processing for imaging the subject P in the MRI apparatus 1 are predefined. In the sequence information, for example, operations of the gradient magnetic field power supply 33, the transmission circuit 34, and the reception circuit 35 and their operation timings (hereinafter referred to as "events") when imaging the subject P are shown in time series. More specifically, the sequence information shows, as events, the magnitude of the current supplied to the gradient magnetic field coil 14 by the gradient magnetic field power supply 33 and the timing of supplying the current, the strength of the RF pulse transmitted (supplied) to the RF coil 16 by the transmission circuit 34 and the timing of supplying the RF pulse, the timing of receiving (detecting) the MR signal output by the RF coil 16 by the reception circuit 35, and the like. The sequence control circuit 32 sequentially executes the events shown in the sequence information to drive the gradient magnetic field power supply 33, the transmission circuit 34, and the reception circuit 35. When the reception circuit 35 receives an MR signal, the received MR signal (more specifically, the MR data output by the reception circuit 35) is transferred to the console device 40.
[0022] Furthermore, the sequence control circuit 32 causes the clock signal generated by the clock generation circuit 31 and the sequence data for driving the wireless RF coil 18 to be transmitted to the transmit / receive circuit 36. The clock signal is the clock signal that the sequence control circuit 32 uses (as a reference) when driving the gradient power supply 33, the transmit circuit 34, and the receive circuit 35. By operating the wireless RF coil 18 based on the transmitted clock signal, the wireless RF coil 18 also operates in synchronization with the gradient power supply 33, the transmit circuit 34, and the receive circuit 35. In other words, the sequence data is a timetable showing the time information for causing the wireless RF coil 18 to image the subject P. The sequence data shows the time information for the wireless RF coil 18 to image the subject P in synchronization with the events shown in the sequence information, in chronological order with reference to the time when the MRI device 1 starts imaging the subject P, that is, the time when the sequence control circuit 32 starts driving the gradient power supply 33, the transmit circuit 34, and the receive circuit 35. More specifically, the sequence data includes the time when the RF coil 16 starts irradiating RF pulses, the duration of the RF pulse irradiation, the intensity of the irradiated RF pulses, and the time and duration when the wireless RF coil 18 starts detecting the MR signal, with the time when the subject P starts imaging as the reference time (time=0). The sequence control circuit 32 drives the gradient power supply 33, the transmitting circuit 34, and the receiving circuit 35 based on the sequence information. That is, before imaging of subject P is started in the MRI device 1, the sequence control circuit 32 starts transmitting a clock signal to the transmitting / receiving circuit 36 and causes the event data to be transmitted to the wireless RF coil 18. When the transmitting / receiving circuit 36 receives the MR data, the sequence control circuit 32 transfers the received MR data to the console device 40.
[0023] The gradient power supply 33 supplies current individually to each of the three coils in the gradient coil 14, corresponding to the direction of each axis.
[0024] The transmitting circuit 34 supplies RF pulses to the RF coil 16. The RF pulses supplied by the transmitting circuit 34 to the RF coil 16 are pulses corresponding to the Larmor frequency, which is determined by the type of atomic nucleus being targeted and the strength of the magnetic field.
[0025] The receiving circuit 35 detects the MR signal output by the RF coil 16 and generates MR data representing the detected MR signal. The receiving circuit 35 generates the MR data, for example, by converting the MR signal into digital data. The receiving circuit 35 outputs the generated MR data to the sequence control circuit 32. The sequence control circuit 32 transfers the MR data output by the receiving circuit 35 to the console device 40.
[0026] The transmitting / receiving circuit 36 transmits the clock signal generated by the clock generation circuit 31 and the sequence data output by the sequence control circuit 32 to the wireless RF coil 18 in response to control from the sequence control circuit 32. The transmitting / receiving circuit 36 receives the MR data transmitted by the wireless RF coil 18. The transmitting / receiving circuit 36 outputs the received MR data to the sequence control circuit 32. The transmitting / receiving circuit 36 uses a wireless communication standard such as Wi-Fi to transmit the clock signal and sequence data and to receive the MR data. The transmitting / receiving circuit 36 includes, for example, an antenna (not shown) that corresponds to the wireless communication standard.
[0027] The bed control circuit 37 outputs a control signal to a bed drive device (not shown) provided in the bed device 20 that moves the base 22 and the top plate 24 on which the subject P is placed, in response to control from the console device 40. The bed control circuit 37 may be located in the cradle device 10 or in the bed device 20. In this case, the bed control circuit 37 outputs a control signal to a bed drive device (not shown) provided in the bed device 20 in response to an input signal input from an input interface (not shown) provided in the device in which the bed control circuit 37 is located, when the operator of the MRI device 1 (such as a doctor or technician) operates the input interface.
[0028] The console device 40 controls the entire MRI device 1 and collects MR data. The console device 40 includes, for example, a memory 41, a display 42, an input interface 43, and a processing circuit 50.
[0029] Memory 41 can be implemented using semiconductor memory elements such as ROM (Read Only Memory), RAM (Random Access Memory), or flash memory, or a hard disk drive (HDD), or an optical disc. Memory 41 stores data such as MR data output by the sequence control circuit 32, and reconstructed images (MRI images) generated based on the MR data. This data may be stored in an external memory that the MRI device 1 can communicate with, rather than in memory 41 (or in addition to memory 41). The external memory may be a NAS (Network Attached Storage) or a cloud server that manages the external memory and accepts read / write requests, thereby being controlled by the cloud server. The external memory can be implemented using a system called PACS (Picture Archiving and Communication Systems). PACS is a medical image management system that systematically stores images taken by various diagnostic imaging devices.
[0030] The display 42 displays various types of information. For example, the display 42 displays images generated by the processing circuit 50, or GUI (Graphical User Interface) images that accept various operations from the operator of the MRI device 1. The display 42 may be, for example, a liquid crystal display (LCD), a CRT (Cathode Ray Tube) display, or an organic EL (Electroluminescence) display. The display 42 may be provided on the rigging device 10. The display 42 may be a desktop type, or it may be a display device (for example, a tablet terminal) that can communicate wirelessly with the main body of the console device 40.
[0031] The input interface 43 receives various input operations from the operator of the MRI device 1 and outputs an electrical signal indicating the content of the received input operation to the processing circuit 50. For example, the input interface 43 receives input operations such as acquisition conditions when acquiring MR data, generation conditions when generating MR data, reconstruction conditions when reconstructing reconstructed images, and image processing conditions when generating post-processed images from reconstructed images. The input interface 43 can be implemented by, for example, a mouse, keyboard, touch panel, trackball, switch, button, joystick, camera, infrared sensor, microphone, etc. If the input interface 43 is a touch panel, the display 42 may be formed integrally with the input interface 43. The input interface 43 may be provided on the gantry device 10. The input interface 43 may also be implemented by a display device (for example, a tablet terminal) that can communicate wirelessly with the main body of the console device 40. In this specification, the input interface 43 is not limited to those equipped with physical operating components such as the mouse and keyboard described above. For example, an electrical signal processing circuit that receives an electrical signal corresponding to an input operation from an external input device provided separately from the console device 40 and outputs this electrical signal to the processing circuit 50 is also an example of an input interface 43.
[0032] The processing circuit 50 controls the overall operation of the MRI device 1. The processing circuit 50 sets sequence information in the sequence control circuit 32. The processing circuit 50 performs functions such as acquisition 51, reconstruction processing 52, image processing 53, and output control 54. The processing circuit 50 realizes these functions, for example, by having a hardware processor provided in a computer device execute a program (software) stored in the memory 41, which is a memory device (storage circuit).
[0033] A hardware processor refers to circuits such as CPUs, GPUs (Graphics Processing Units), Application Specific Integrated Circuits (ASICs), and programmable logic devices (e.g., Simple Programmable Logic Devices (SPLDs), Complex Programmable Logic Devices (CPLDs), and Field Programmable Gate Arrays (FPGAs)). Instead of storing the program in memory 41, the program may be directly embedded within the hardware processor's circuitry. In this case, the hardware processor performs its functions by reading and executing the program embedded within the circuitry. A hardware processor is not limited to being configured as a single circuit; it may be configured as a single hardware processor by combining multiple independent circuits to perform each function. Multiple components may be integrated into a single hardware processor to perform each function. Multiple components may be incorporated into a single dedicated LSI to perform each function. Here, the program (software) may be stored in advance in a storage device that constitutes memory 41, such as ROM, RAM, HDD, or flash memory (a storage device equipped with a non-transient storage medium), or it may be stored in a removable storage medium (a non-transient storage medium) such as a DVD or CD-ROM, and installed in the storage device of the console device 40 when the storage medium is inserted into a drive device provided in the console device 40. The program (software) may also be downloaded in advance from another computer device via a network and installed in the storage device of the console device 40.
[0034] Each component of the console device 40 or the processing circuit 50 may be distributed and implemented by multiple hardware components. The processing circuit 50 may not be implemented in the configuration of the console device 40, but rather by a processing unit that can communicate with the console device 40. The processing unit may be, for example, a workstation connected to one MRI device, or a device (e.g., a cloud server) connected to multiple MRI devices that performs processing equivalent to that of the processing circuit 50 described below in a batch. In other words, the configuration of this embodiment can also be implemented as an MRI examination system (medical diagnostic system) in which an MRI device and other processing units are connected via a network.
[0035] The acquisition function 51 acquires the MR data transferred by the sequence control circuit 32. The MR data is either the MR signal converted into digital data by the receiving circuit 35, or the data received by the transmitting / receiving circuit 36 from the wireless RF coil 18.
[0036] The reconstruction processing function 52 generates a reconstructed image by performing a predetermined reconstruction process on the MR data acquired by the acquisition function 51. For example, the reconstruction processing function 52 arranges the MR data in two or three dimensions corresponding to the gradient magnetic field for slice selection, the gradient magnetic field for phase encoding, and the gradient magnetic field for readout, and then generates a reconstructed image by performing a reconstruction process using Fourier transform or the like. The reconstruction processing function 52 stores the generated reconstructed image in the memory 41.
[0037] The image processing function 53 converts the reconstructed image stored in the memory 41 into a three-dimensional image or cross-sectional image data of an arbitrary cross-section using a known method, based on the input operation received by the input interface 43. The image processing function 53 stores the converted cross-sectional image data in the memory 41 as an MR image.
[0038] The output control function 54 controls, for example, the display mode on the display 42. The output control function 54 outputs and displays the MR image generated by the image processing function 53 and stored in the memory 41 on the display 42. This allows the person performing the MRI examination (such as a doctor or technician) to visually confirm the MR image displayed on the display 42 and diagnose whether or not there is a lesion in the subject P. The output control function 54 may also transmit the MR image to, for example, a tablet terminal connected to the main unit of the console device 40 via a network, and display it on the display device. The output control function 54 may also display a GUI image or the like to accept various operations from the operator of the MRI device 1.
[0039] Next, the configuration of the wireless RF coil 18 will be described. Figure 2 is a diagram showing an example of the configuration and connection of the wireless RF coil 18 according to the embodiment. Figure 2 also shows a more detailed example of the configuration of the receiving circuit 35 that transmits and receives clock signals and sequence data to and from the wireless RF coil 18.
[0040] The transmitting / receiving circuit 36 includes, for example, a data transmission circuit 361, a clock transmission circuit 362, and a data receiving circuit 363. The data transmission circuit 361 transmits sequence data output by the sequence control circuit 32 to the wireless RF coil 18. The clock transmission circuit 362 transmits the clock signal generated by the clock generation circuit 31 to the wireless RF coil 18. The data receiving circuit 363 receives MR data transmitted by the wireless RF coil 18. The data receiving circuit 363 outputs the received MR data to the sequence control circuit 32. Each of the data transmission circuit 361, the clock transmission circuit 362, and the data receiving circuit 363 may individually be equipped with an antenna (not shown).
[0041] The wireless RF coil 18 includes, for example, a coil section 180, a data receiving circuit 181, a clock receiving circuit 182, a data transmission circuit 183, a sequence execution circuit 184, a phase synchronization circuit 185, and an AD converter 186. The phase synchronization circuit 185 includes, for example, a VCO (Voltage Controlled Oscillator) 1851, a frequency divider 1852, a phase comparator 1853, and a loop filter 1854. The wireless RF coil 18 includes a battery (secondary battery) not shown, such as a nickel-metal hydride battery, as a power source for each of its components. Furthermore, the wireless RF coil 18 includes, for example, an antenna not shown for wireless communication with the transmitting / receiving circuit 36.
[0042] The coil section 180 is a coil element attached to the subject P, or a coil array composed of multiple coil elements. The coil section 180 outputs an MR signal (analog signal) emitted from the subject P due to the influence of the high-frequency magnetic field generated by the RF coil 16 to the AD converter 186.
[0043] The data receiving circuit 181 receives sequence data transmitted by the data transmitting circuit 361. The data receiving circuit 181 outputs the received sequence data to the sequence execution circuit 184. The data receiving circuit 181 may, for example, be equipped with an antenna not shown separately.
[0044] The clock receiving circuit 182 receives the clock signal transmitted by the clock transmitting circuit 362. The clock receiving circuit 182 outputs the received clock signal (hereinafter referred to as "received clock signal RCLK") to the phase synchronization circuit 185 (more specifically, the phase comparator 1853 provided in the phase synchronization circuit 185). The clock receiving circuit 182 may also be equipped with an antenna not shown, for example. The clock receiving circuit 182 is an example of a "clock receiving unit".
[0045] The data transmission circuit 183 transmits the MR data output by the AD converter 186 to the transmit / receive circuit 36 (more specifically, the data receiving circuit 363 provided by the transmit / receive circuit 36). The data transmission circuit 183 may, for example, be equipped with an antenna not shown separately.
[0046] The sequence execution circuit 184 performs imaging operations on the subject P in synchronization with the events indicated in the sequence information executed by the sequence control circuit 32, based on the sequence data output by the data reception circuit 181. More specifically, the sequence execution circuit 184 operates the phase synchronization circuit 185 and the AD converter 186 at each time based on the time information indicated in the sequence data. The sequence execution circuit 184 may be, for example, a sequencer or a processing circuit having a processor such as a CPU. The sequence execution circuit 184 is an example of a "phase synchronization control unit".
[0047] The phase-locked circuit 185 is a PLL (Phase Locked Loop) that generates a clock signal CLK for the operation of the components of the wireless RF coil 18. The phase-locked circuit 185 generates a clock signal CLK that is synchronized (phase-locked) with the received clock signal RCLK output by the clock receiving circuit 182. Figure 2 shows the case where the clock signal CLK generated by the phase-locked circuit 185 is output to the AD converter 186. The phase-locked circuit 185 is an example of a "phase-locked section".
[0048] The VCO1851 is a voltage-controlled oscillator that generates a clock signal (hereinafter referred to as "internal clock signal ICLK") with a frequency corresponding to the voltage. The VCO1851 generates an internal clock signal ICLK with a variable frequency according to the voltage control from the loop filter 1854. The VCO1851 outputs the generated internal clock signal ICLK to the frequency divider 1852. The VCO1851 is an example of a "clock generation unit".
[0049] The frequency divider 1852 divides the internal clock signal ICLK output by the VCO 1851 to the same frequency as the received clock signal RCLK. The frequency divider 1852 outputs the divided clock signal to the phase comparator 1853. The frequency divider 1852 is not limited to a configuration that divides the internal clock signal ICLK, but may also be configured to output a clock signal to the phase comparator 1853 that has the same frequency as the received clock signal RCLK by multiplying the internal clock signal ICLK.
[0050] The phase comparator 1853 compares the phase of the received clock signal RCLK output by the clock receiving circuit 182 with the phase of the clock signal output by the frequency divider 1852, in response to control from the sequence execution circuit 184. The phase comparator 1853 outputs a signal representing the result of the phase comparison (hereinafter referred to as the "phase comparison signal") to the loop filter 1854. The phase comparison signal is a signal that indicates whether the phase of the clock signal output by the frequency divider 1852 is leading or lagging behind the phase of the received clock signal RCLK. For example, the phase comparison signal is at a "High" level when the phase of the clock signal output by the frequency divider 1852 is leading the phase of the received clock signal RCLK, and at a "Low" level when it is lagging behind.
[0051] The loop filter 1854 is a filter whose operating bandwidth during filtering can be changed. The loop filter 1854 is, for example, a low-pass filter (LPF). The operating bandwidth of the loop filter 1854 can be changed to at least two bandwidths: a wideband and a narrowband. The operating bandwidth of the loop filter 1854 is switched by the sequence execution circuit 184. The loop filter 1854 filters the phase comparison signal output by the phase comparator 1853 within the operating bandwidth switched by control from the sequence execution circuit 184, converting the phase comparison signal into a roughly DC voltage signal. The loop filter 1854 outputs the converted voltage signal to the VCO 1851. In other words, the loop filter 1854 feeds back the result of the phase comparison in the phase comparator 1853 to the VCO 1851. As a result, the VCO 1851 generates an internal clock signal ICLK with a frequency corresponding to the voltage signal output by the loop filter 1854. The VCO1851 outputs the internally generated clock signal ICLK as a phase-synchronized clock signal CLK by the phase-synchronization circuit 185 to the components of the wireless RF coil 18 (AD converter 186 in Figure 2). The loop filter 1854 is an example of a "loop filter".
[0052] The AD converter 186 converts the analog MR signal output by the coil section 180 into digital MR data by sampling it based on the clock signal CLK output by the phase-lock circuit 185. The AD converter 186 outputs the converted MR data to the data transmission circuit 183. The data transmission circuit 183 then transmits the MR data to the data receiving circuit 363.
[0053] With this configuration, the MRI device 1 receives the MR signal emitted from the subject P using the RF coil 16 and / or wireless RF coil 18, and acquires an MR image of the subject P. At this time, the MRI device 1 uses a sequence control circuit 32 to transmit a clock signal generated by the clock generation circuit 31 to the wireless RF coil 18 via the transmit / receive circuit 36, thereby synchronizing the wireless RF coil 18 with the gradient magnetic field power supply 33, the transmit circuit 34, and the receive circuit 35, enabling the acquisition of a localized MR image of the subject P. However, the RF pulse irradiated onto the subject P in the MRI device 1 to acquire an MR image (more specifically, the high-frequency magnetic field generated by the RF coil 16 in response to the RF pulse) is high-frequency, although it is different from the frequency used in wireless communication standards such as Wi-Fi, which the transmit / receive circuit 36 uses to transmit and receive between the wireless RF coil 18 and the wireless RF coil 18. For this reason, it is conceivable that the irradiation of the RF pulse may have some effect on the wireless communication between the wireless RF coil 18 and the transmit / receive circuit 36. In particular, the clock signal transmitted during the period when the gradient magnetic field power supply 33, the transmitting circuit 34, and the receiving circuit 35 are driven in order to synchronize the operation of the wireless RF coil 18 is likely to be greatly affected by the RF pulse.
[0054] Therefore, the sequence execution circuit 184 of the wireless RF coil 18 controls the generation of the clock signal CLK that controls the operation of each component of the wireless RF coil 18, based on the sequence data. In other words, the sequence execution circuit 184 controls the operation of the phase-locking circuit 185.
[0055] [An example of a first control method for a phase-locked circuit] Here, an example of a control method for the phase-synchronous circuit 185 by the sequence execution circuit 184 will be described. Figure 3 is a diagram showing an example of a first control method for the phase-synchronous circuit 185 in the sequence execution circuit 184 provided in the wireless RF coil 18 according to this embodiment. Figure 3 shows the phase-synchronous circuit 185 related to the generation of the clock signal CLK in the wireless RF coil 18, together with the control timing by the sequence execution circuit 184.
[0056] The sequence execution circuit 184 is assumed to have sequence data input that indicates, for example, the time t1 at which the RF coil 16 starts irradiating an RF pulse and the duration of the RF pulse irradiation (the period from time t1 to time t2 at which the RF pulse irradiation ends). In Figure 3, the duration of the RF pulse irradiation is shown as the period during which the RF gate signal is at a "High" level, schematically illustrating an example of the state in which the RF pulse is actually irradiated. The duration of the RF pulse irradiation is, for example, 200 [μs] to 1 [ms].
[0057] In this case, the sequence execution circuit 184 causes the phase comparator 1853 to perform a phase comparison during the period prior to time t1. As a result, the phase synchronization circuit 185 outputs the internal clock signal ICLK, which is synchronized in phase with the received clock signal RCLK, i.e., the clock signal generated by the clock generation circuit 31, as the clock signal CLK. Then, at time t1, the sequence execution circuit 184 stops the phase comparison of the phase comparator 1853. As a result, the loop filter 1854 outputs a fixed voltage signal to the VCO 1851, and the internal clock signal ICLK generated (self-propelled) by the VCO 1851 is output as the clock signal CLK from the phase synchronization circuit 185. Subsequently, at time t2, the sequence execution circuit 184 causes the phase comparator 1853 to perform a phase comparison again. In other words, the sequence execution circuit 184 restores the PLL operation of the phase synchronization circuit 185 from its stopped state. As a result, the phase-locking circuit 185 outputs the internal clock signal ICLK, which is in phase-locked with the received clock signal RCLK, as the clock signal CLK.
[0058] In this way, the sequence execution circuit 184 stops the phase comparison operation in the phase comparator 1853 during the RF pulse irradiation period (the period during which the RF gate signal is at a "High" level). As a result, the phase synchronization circuit 185 can output a clock signal CLK that is unaffected by the RF pulse irradiation in the RF coil 16, without having to perform phase synchronization with the received clock signal RCLK, which may have its period disrupted (increased jitter) due to some influence on the wireless communication between the wireless RF coil 18 and the transceiver circuit 36 during the period when the RF coil 16 is irradiating with RF pulses.
[0059] Figure 3 shows the control method when an RF pulse is irradiated once. However, in imaging of subject P in MRI device 1, RF pulses are irradiated multiple times. Therefore, the sequence execution circuit 184 controls the operation of the phase-locked circuit 185 by repeating the first control method shown in Figure 3 for each RF pulse irradiation period (RF gate signal).
[0060] Incidentally, the phase of the clock signal CLK output by the phase-locking circuit 185 (the internal clock signal ICLK generated by the VCO 1851 through self-propulsion) may gradually shift from the clock signal generated by the clock generation circuit 31 during the period when the phase comparator 1853 has stopped phase locking, that is, during the period when the phase-locking circuit 185 is not operating the PLL. However, the sequence execution circuit 184 causes the phase comparator 1853 to perform a phase comparison again at time t2, when the period during which the RF coil 16 irradiates RF pulses ends. Therefore, even if the phase of the clock signal CLK gradually shifts from the phase of the clock signal generated by the clock generation circuit 31, the result of the phase comparison is fed back to the VCO 1851 from the moment the sequence execution circuit 184 performs the phase comparison, the phase discrepancy is resolved in a short period of time, and the phase-locking circuit 185 will once again output a phase-locked (phase-synchronized) clock signal CLK.
[0061] [An example of a second control method for a phase-locked circuit] Here, we will describe an example of a control method in which the sequence execution circuit 184 controls the phase synchronization circuit 185, assuming that, for example, the sequence execution circuit 184 has the phase comparator 1853 perform a phase comparison again, but the phase misalignment is not resolved in a short period of time. Figure 4 is a diagram showing an example of a second control method for the phase synchronization circuit in the sequence execution circuit 184 provided in the wireless RF coil 18 according to the embodiment. Figure 4 also shows the phase synchronization circuit 185 related to the generation of the clock signal CLK in the wireless RF coil 18, and the control timing by the sequence execution circuit 184. In the second control method shown in Figure 4, in addition to the first control method shown in Figure 3, the sequence execution circuit 184 also switches the operating bandwidth of the loop filter 1854. In other words, in the second control method shown in Figure 4, the method by which the sequence execution circuit 184 controls the phase comparator 1853 is the same as the first control method shown in Figure 3. Therefore, a further explanation of the method by which the sequence execution circuit 184 controls the phase comparator 1853 will be omitted.
[0062] In this case, the sequence execution circuit 184 narrows the operating bandwidth of the loop filter 1854 during the period prior to time t2. As a result, in the phase-locking circuit 185, the internal clock signal ICLK, in which the phase of the received clock signal RCLK and the phase of the internal clock signal ICLK are synchronized with higher precision, is output as the clock signal CLK. Then, at time t2, the sequence execution circuit 184 widens the operating bandwidth of the loop filter 1854. As a result, even if the phase of the clock signal CLK shifts slightly between time t1 and time t2 due to the phase comparison of the phase comparator 1853 being stopped in the phase-locking circuit 185, widening the operating bandwidth of the loop filter 1854 allows the PLL operation state to approach a state equivalent to a state where the phases are synchronized more quickly, although the precision is lower compared to when the operating bandwidth is narrowed. In other words, widening the operating bandwidth of the loop filter 1854 shortens the time required for the phase-locking circuit 185 to reach a predetermined phase difference. Subsequently, the sequence execution circuit 184 narrows the operating bandwidth of the loop filter 1854 again at time t3. As a result, the phase-locking circuit 185 outputs the internal clock signal ICLK of the PLL operation, which is synchronized with the phase of the received clock signal RCLK with higher precision, as the clock signal CLK. The period from time t2 to time t3 during which the operating bandwidth of the loop filter 1854 is widened may be a predetermined period, for example, the time required from when the phase-locking circuit 185 starts phase-locking operation (PLL operation) until the phase lock converges (the phase locks). The period from time t2 to time t3 during which the operating bandwidth of the loop filter 1854 is widened may be determined by detecting the amount of phase difference between the phase of the received clock signal RCLK and the internal clock signal ICLK, and setting time t3 to when the difference falls below a predetermined amount. The phase difference between the received clock signal RCLK and the internal clock signal ICLK may be detected, for example, by determining the phase comparison signal output by the phase comparator 1853, or based on the voltage signal output by the loop filter 1854.
[0063] In this way, if the sequence execution circuit 184 anticipates that the phase difference between the received clock signal RCLK and the internal clock signal ICLK will not be resolved in a short period of time, it will widen the operating bandwidth of the loop filter 1854 for a predetermined period (the period between time t2 and time t3) when it restores the PLL operation of the phase synchronization circuit 185. As a result, the phase synchronization circuit 185 can approach a state where the phase is synchronized within a predetermined phase difference more quickly than if the operating bandwidth of the loop filter 1854 were not changed (if it remained narrow).
[0064] Figure 4 also shows the control method when an RF pulse is irradiated once. The sequence execution circuit 184 controls the operation of the phase-locked circuit 185 by repeating the second control method shown in Figure 4 for each irradiation period (RF gate signal) of each RF pulse that is irradiated multiple times when the subject P is imaged in the MRI device 1.
[0065] Incidentally, as mentioned above, considering that the phase of the internal clock signal ICLK gradually shifts from the phase of the clock signal generated by the clock generation circuit 31, it is desirable that the period during which the phase synchronization circuit 185 is not operating the PLL (the period during which the phase comparator 1853 has stopped phase synchronization) be as short as possible. For this reason, the sequence execution circuit 184 may adjust the timing and duration of the phase synchronization circuit 185 stopping the PLL operation.
[0066] [An example of a third control method for a phase-locked circuit] Here, an example of a control method for shortening the period during which the phase comparator 1853 has stopped phase synchronization will be described. Figure 5 is a diagram showing an example of a third control method for the phase synchronization circuit 185 in the sequence execution circuit 184 provided in the wireless RF coil 18 according to the embodiment. Figure 5 also shows the phase synchronization circuit 185 related to the generation of the clock signal CLK in the wireless RF coil 18, and the control timing by the sequence execution circuit 184 together. In the third control method shown in Figure 5, the control method of the sequence execution circuit 184 for causing the phase synchronization circuit 185 to perform PLL operation or to stop PLL operation is the same as the first control method shown in Figure 3. Therefore, a further explanation of how the sequence execution circuit 184 controls the phase synchronization circuit 185 will be omitted.
[0067] The sequence execution circuit 184 is assumed to have sequence data input that includes, for example, the time t1 at which the RF coil 16 begins irradiating RF pulses, time t2 representing the duration of RF pulse irradiation, time t4 at which the irradiated RF pulses exceed a certain intensity (RF pulse intensity threshold) that could potentially affect wireless communication between the wireless RF coil 18 and the transceiver circuit 36, and time t5 at which RF pulses exceeding the RF pulse intensity threshold are irradiated. The RF pulse intensity threshold is the intensity of the RF pulse determined by whether or not it affects wireless communication, but the timing of time t4 and time t5 is determined, for example, by the results of pre-imaging to determine the intensity of the irradiated RF pulses, which is performed as a preliminary step before starting imaging (diagnosis) of subject P, or by the physique of subject P. Therefore, when diagnosing subject P, if it is possible to acquire the MR images necessary for diagnosis without irradiating RF pulses of an intensity exceeding the RF pulse intensity threshold, the timing of time t4 and time t5 does not need to be determined. Time t4 is an example of the "first elapsed time," and time t5 is an example of the "second elapsed time."
[0068] The sequence execution circuit 184 causes the phase-locking circuit 185 to operate in a PLL manner during the period prior to time t4, outputting an internal clock signal ICLK, which is in phase with the received clock signal RCLK, as the clock signal CLK. Then, at time t4, the sequence execution circuit 184 stops the PLL operation of the phase-locking circuit 185, causing the internal clock signal ICLK generated by the VCO 1851's self-propelled operation to output as the clock signal CLK. Subsequently, at time t5, the sequence execution circuit 184 restores the phase-locking circuit 185 from the state in which the PLL operation was stopped.
[0069] In this way, the sequence execution circuit 184 stops the PLL operation in the phase-lock circuit 185 only during the period when RF pulses exceeding an RF pulse intensity threshold, which could potentially affect wireless communication between the wireless RF coil 18 and the transceiver circuit 36, are irradiated during the RF pulse irradiation period (the period when the RF gate signal is at a "High" level). This shortens the period during which the internal clock signal ICLK, which is automatically generated by the VCO 1851 from the phase-lock circuit 185, is output as the clock signal CLK.
[0070] Figure 5 also shows the control method when an RF pulse is irradiated once. The sequence execution circuit 184 controls the operation of the phase-locked circuit 185 by repeating the third control method shown in Figure 5 for each irradiation period (RF gate signal) of each RF pulse that is irradiated multiple times when the subject P is imaged in the MRI device 1.
[0071] In the third control method shown in Figure 5, the sequence execution circuit 184 stops the PLL operation of the phase-locked circuit 185 based on the strength of the RF pulse, that is, the peak height of the RF pulse. However, the adjustment of the period during which the sequence execution circuit 184 outputs the self-propelled internal clock signal ICLK as the clock signal CLK is not limited to the strength of the RF pulse. For example, the sequence execution circuit 184 may perform control to stop the PLL operation of the phase-locked circuit 185 when the duration of irradiation with the RF pulse exceeds a predetermined length, that is, based on the width of the irradiated RF pulse.
[0072] In the third control method shown in Figure 5, an example is shown in which the sequence execution circuit 184 stops or resumes the PLL operation in the phase-locking circuit 185 based on the time t4 and time t5, which are indicated in the sequence data transmitted by the control device 30 via wireless communication, when the RF pulse is equal to or greater than the RF pulse intensity threshold. However, the wireless RF coil 18 can also be configured to detect whether or not the RF pulse is equal to or greater than the RF pulse intensity threshold.
[0073] Here, we will describe an example of a wireless RF coil 18 configured to detect the intensity of an RF pulse. Figure 6 shows another example of a configuration and connection of the wireless RF coil 18 according to the embodiment. Figure 6 also shows a more detailed example of the configuration of the receiving circuit 35 that transmits and receives clock signals and sequence data with the wireless RF coil 18 of the other configuration (hereinafter referred to as "wireless RF coil 18a"), but since the configuration of the receiving circuit 35 is the same as the configuration for transmitting and receiving with the wireless RF coil 18, a further detailed explanation will be omitted.
[0074] The wireless RF coil 18a includes, for example, a coil section 180, a data receiving circuit 181, a clock receiving circuit 182, a data transmission circuit 183, a sequence execution circuit 184, a phase synchronization circuit 185, an AD converter 186, and an RF intensity detection circuit 187. The wireless RF coil 18a is configured with the addition of the RF intensity detection circuit 187 to the wireless RF coil 18. In the wireless RF coil 18a, components that are the same as those in the wireless RF coil 18 are given the same reference numerals. Therefore, a further detailed explanation of components in the wireless RF coil 18a that have the same configuration and operation as those in the wireless RF coil 18 will be omitted, and only the different configurations and operations will be explained.
[0075] The RF intensity detection circuit 187 detects the strength of the RF pulses (more specifically, the high-frequency magnetic field generated by the RF coil 16 in response to the RF pulses) irradiated onto the subject P in order to acquire MR images in the MRI device 1. The RF intensity detection circuit 187 has, for example, a preset RF pulse intensity threshold, and when it detects an RF pulse that is equal to or greater than the RF pulse intensity threshold, it outputs a detection signal to the sequence execution circuit 184 indicating this. As a result, the sequence execution circuit 184 performs the same control on the phase-locking circuit 185 as shown at times t4 and t5 in Figure 5, based on the detection signal output by the RF intensity detection circuit 187. In other words, the sequence execution circuit 184 stops the PLL operation of the phase-locking circuit 185 while the RF intensity detection circuit 187 is outputting a detection signal indicating that an RF pulse equal to or greater than the RF pulse intensity threshold has been detected. The RF intensity detection circuit 187 is an example of an "RF intensity detection unit".
[0076] This allows the wireless RF coil 18a to adjust the period during which the internal clock signal ICLK, which is automatically generated by the VCO 1851 from the phase-locking circuit 185, is output as the clock signal CLK, based on the intensity of the RF pulse it detects, to a suitable period that matches the period during which it is actually greatly affected by the RF pulse.
[0077] As described above, in the MRI apparatus 1, which is a magnetic resonance imaging apparatus of the embodiment, a clock signal and sequence data are transmitted wirelessly to a wireless RF coil 18, which is a wireless local coil, and the wireless RF coil 18 receives the MR data transmitted wirelessly. Then, in the MRI apparatus 1 of the embodiment, the wireless RF coil 18 performs imaging of the subject P in synchronization with the imaging performed in the main body of the MRI apparatus 1, based on the sequence data transmitted wirelessly. At this time, in the MRI apparatus 1 of the embodiment, if the RF pulse irradiated by the RF coil 16 to image the subject P may affect the clock signal transmitted wirelessly to the wireless RF coil 18, the phase-locked operation (PLL operation) between the received clock signal RCLK and the internal clock signal ICLK that operates within the wireless RF coil 18 is stopped for that period. As a result, the clock signal CLK on which the wireless RF coil 18 operates becomes a stable clock signal that is not affected by the irradiation of RF pulses in the RF coil 16. As a result, in the MRI apparatus 1 of the embodiment, a more suitable MR image can be acquired by the wireless RF coil 18.
[0078] According to at least one embodiment described above, the apparatus includes a transmitting coil (16) that irradiates a subject (P) with RF pulses, a receiving coil (18) that receives a magnetic resonance signal from the subject, and a control unit (30) that controls the transmitting coil and the receiving coil. The receiving coil includes a clock receiving unit (182) that receives a clock signal transmitted wirelessly by the control unit, a phase synchronization unit (185) that performs phase synchronization with the clock signal, and a phase synchronization control unit (184) that controls the phase synchronization unit. The phase synchronization control unit switches the operating state of the phase synchronization unit according to the irradiation timing of the RF pulses, thereby reducing the influence of RF pulses on the clock signal in the wireless RF coil (18) when the RF coil (16) of the magnetic resonance imaging apparatus is made wireless.
[0079] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.
[0080] With respect to the above embodiments, the following additional notes are disclosed as aspects of the invention and selective features. (Note 1) A transmitting coil that irradiates the subject with RF pulses, A receiving coil that receives magnetic resonance signals from the subject, A control unit that controls the transmitting coil and the receiving coil, Equipped with, The receiving coil is A clock receiving unit that receives a clock signal transmitted wirelessly by the control unit, A phase synchronization unit that performs phase synchronization with the aforementioned clock signal, A phase synchronization control unit that controls the phase synchronization unit, Equipped with, The phase-synchronization control unit switches the operating state of the phase-synchronization unit according to the irradiation timing of the RF pulse. Magnetic resonance imaging (MRI) device.
[0081] (Note 2) The phase synchronization unit includes a clock generation unit that generates an internal clock signal, The phase synchronization control unit may stop the phase synchronization in the phase synchronization unit in accordance with the irradiation timing of the RF pulse, and output the internal clock signal generated by the clock generation unit from the phase synchronization unit.
[0082] (Note 3) The phase-synchronization unit includes a loop filter with a changeable operating bandwidth, The phase synchronization control unit may widen the operating bandwidth of the loop filter when restoring the phase synchronization in the phase synchronization unit from a stopped state.
[0083] (Note 4) The phase synchronization control unit may, after widening the operating bandwidth of the loop filter, narrow the operating bandwidth of the loop filter when the time required for the phase synchronization to converge in the phase synchronization unit has elapsed.
[0084] (Note 5) The phase-synchronization control unit may adjust the period for which the phase-synchronization in the phase-synchronization unit is stopped based on the intensity of the irradiated RF pulse.
[0085] (Note 6) The phase synchronization control unit, Based on a first elapsed time from the start of irradiation of the RF pulse, the phase synchronization in the phase synchronization unit is stopped. Based on a second elapsed time, which is a further time elapsed since the first elapsed time, the phase synchronization may be restored from the stopped state.
[0086] (Note 7) The receiving coil includes an RF intensity detection unit that detects the intensity of the irradiated RF pulse, The phase synchronization control unit, When the RF intensity detection unit detects an RF pulse intensity above a threshold, it stops the phase synchronization in the phase synchronization unit. When the RF intensity detection unit detects an RF pulse intensity weaker than the threshold, the phase synchronization may be restored from its stopped state.
[0087] (Note 8) The phase-synchronization control unit may control the operating state of the phase-synchronization unit based on time information transmitted wirelessly by the control unit before the start of shooting the subject, which indicates the irradiation timing of the RF pulses in chronological order with respect to the start time of shooting the subject. [Explanation of Symbols]
[0088] 1...MRI device, 10...Stand device, 12...Static magnetic field magnet, 14...Gradient field coil, 16...RF coil, 18,18a...Wireless RF coil, 180...Coil section, 181...Data receiving circuit, 182...Clock receiving circuit, 183...Data transmission circuit, 184...Sequence execution circuit, 185...Phase synchronization circuit, 1851...VCO, 1852...Frequency divider, 1853...Phase comparator, 1854...Loop filter, 186...AD converter, 187...RF intensity detection circuit, 20...Patient table device, 22...Base, 24...Top panel, 30...Control device, 31...Clock generation circuit, 32...Sequence control circuit, 33...Gradient field power supply, 34...Transmitting circuit, 35...Receiving circuit, 36...Transmitting and receiving circuit, 361...Data transmission circuit, 362...Clock transmission circuit, 363...Data receiving circuit, 37...Bed control circuit, 40...Console device, 41...Memory, 42...Display, 43...Input interface, 50...Processing circuit, 51...Acquisition function, 52...Reconstruction processing function, 53...Image processing function, 54...Output control function
Claims
1. A control device having a first generation unit that generates a first clock signal, and a control unit that controls an RF coil that outputs RF pulses to be irradiated onto a subject based on the first clock signal, A receiving coil unit including a detection unit that detects a magnetic resonance signal generated from the subject by the RF pulse, Equipped with, The control device is A transmitting unit that transmits the wireless signal of the first clock signal regardless of whether the RF pulse is output from the RF coil. Equipped with, The receiving coil unit is A receiving unit that receives the wireless signal of the first clock signal, A second generation unit generates a second clock signal, compares the lead or lag between the generated second clock signal or the generated second clock signal's phase and the phase of the first clock signal represented by the wireless signal, and outputs a third clock signal with synchronized phases as a fourth clock signal. A conversion unit converts the magnetic resonance signal of the analog signal detected by the detection unit into magnetic resonance data of the digital signal based on the fourth clock signal. An output unit that outputs the magnetic resonance data of the digital signal converted by the conversion unit via wireless communication, Equipped with, The second generation unit is, During the first period when the RF pulse is not output from the RF coil, the receiver outputs the third clock signal, whose phase is synchronized with the phase of the second clock signal relative to the phase of the first clock signal represented by the radio signal received by the receiver, as the fourth clock signal to the converter. During at least a portion of the second period in which the RF pulse is output from the RF coil, the second clock signal, whose phase is not synchronized, is output to the conversion unit as the fourth clock signal. Magnetic resonance imaging (MRI) device.
2. The second generation unit is, During the second period, the receiving unit stops the operation of comparing the phase advance or delay of the second clock signal with respect to the phase of the first clock signal represented by the received wireless signal. During the first period, the receiving unit performs an operation to compare the phase advance or delay of the second clock signal with respect to the phase of the first clock signal represented by the received wireless signal. The magnetic resonance imaging apparatus according to claim 1.
3. The second generation unit is, During the third period in the second period in which the intensity of the RF pulse is greater than a predetermined value, the second clock signal is output to the conversion unit as the fourth clock signal. During the fourth period in the second period in which the intensity of the RF pulse is less than the predetermined value, the receiver outputs the third clock signal, whose phase is synchronized with the phase of the second clock signal relative to the phase of the first clock signal represented by the radio signal received by the receiver, as the fourth clock signal to the converter. The magnetic resonance imaging apparatus according to claim 1.
4. The second generation unit is, During the third period, the receiving unit stops the operation of comparing the phase advance or delay of the second clock signal with respect to the phase of the first clock signal represented by the received wireless signal. During the fourth period, the receiving unit performs an operation to compare the phase advance or delay of the second clock signal with respect to the phase of the first clock signal represented by the received wireless signal. The magnetic resonance imaging apparatus according to claim 3.
5. The second generation unit is, It features a loop filter with a changeable operating bandwidth, From the end of the second period described above until a predetermined fifth period, the operating bandwidth of the loop filter is widened. The magnetic resonance imaging apparatus according to claim 1.
6. The second generation unit is, During at least a portion of the second period, at the last moment before the RF coil switches from a state where no RF pulse is output to a state where it is output, the third clock signal output to the conversion unit as the fourth clock signal is switched to the second clock signal. The magnetic resonance imaging apparatus according to claim 1.
7. The magnetic resonance imaging apparatus includes a fourth generation unit that generates an image based on the magnetic resonance data transmitted from the output unit via wireless communication. The magnetic resonance imaging apparatus according to claim 1.