Magnetic resonance imaging apparatus and control method for magnetic resonance imaging apparatus

Abstract

To reduce a clock phase shift by phasing and improve accuracy of a reconstruction image while suppressing power consumption of a reception coil unit.SOLUTION: A magnetic resonance imaging apparatus according to an embodiment includes a main unit and a reception coil unit. The main unit includes a clock generation part, a clock reception part, a clock phase control part, and a clock transmission part. The clock generation part generates a first clock signal. The clock reception part receives a clock signal wirelessly transmitted by the reception coil unit and generates a second clock signal. The clock phase control part executes phase control of a third clock signal on the basis of a phase difference between the first clock signal and the second clock signal in a first period based on pulse sequence information, and stops the phase control in a second period based on the pulse sequence information. The clock transmission part wirelessly transmits the third clock signal to the reception coil unit.SELECTED DRAWING: Figure 7

Description

Technical Field

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

Background Art

[0002] A magnetic resonance imaging (MRI) apparatus is an imaging apparatus that excites the nuclear spins of a subject placed in a static magnetic field with an RF (Radio Frequency) signal at the Larmor frequency and reconstructs the MR (Magnetic Resonance) signal generated from the subject upon excitation to generate an image. In an MRI apparatus, an RF pulse is transmitted from the main unit toward the subject. In response to this transmission, the magnetic resonance signal emitted from the subject is received by the receive coil unit. The receive coil unit receives the magnetic resonance signal emitted from the subject at a position close to the subject. The receive coil unit has various types such as for the head, chest, spine, lower limbs, etc., according to the imaging site of the subject.

[0003] Conventionally, wired receiving coil units that transmit received magnetic resonance signals to the main unit via a wire have been widely used. In contrast, a wireless receiving coil unit has been proposed that converts the received magnetic resonance signal from an analog signal to a digital signal using an ADC (Analog to Digital Converter), and then transmits the digitized magnetic resonance signal wirelessly to the main unit. When using a wired receiving coil unit, the magnetic resonance signal sent as an analog signal from the receiving coil unit to the main unit is converted from analog to digital on the main unit side using a sampling clock generated from the system clock on the main unit side. On the other hand, when using a wireless receiving coil unit, a sampling clock for converting the magnetic resonance signal from analog to digital is required on the receiving coil unit side, and a system clock for generating the sampling clock is also required on the receiving coil unit side. Here, the system clock on the receiving coil unit side and the system clock on the main unit side must be synchronized with each other, and if there is a phase difference between these clocks, the accuracy of the reconstructed image may decrease.

[0004] However, in the wireless receiving coil unit system described above, a phase shift may occur between the system clock of the receiving coil unit and the system clock of the main unit due to the effects of fading in the wireless propagation path. Furthermore, since wireless receiving coil units are generally battery-powered, low power consumption is desirable. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2010-29644 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] One of the problems that the embodiments disclosed herein and in the drawings aim to solve is to reduce the power consumption of the receiving coil unit, reduce clock phase shift due to fading, and improve the accuracy of the reconstructed image. However, the problems that the embodiments disclosed herein and in the drawings aim to solve are not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described later can also be positioned as other problems. [Means for solving the problem]

[0007] The MRI apparatus according to the embodiment includes a main unit and a receiving coil unit separate from the main unit. The main unit comprises a clock generation unit, a main unit-side clock receiving unit, a clock phase control unit, a main unit-side clock transmission unit, a main unit-side data communication unit, and an image reconstruction unit. The clock generation unit generates a first clock signal. The main unit-side clock receiving unit receives the clock signal wirelessly transmitted by the receiving coil unit and generates a second clock signal. The clock phase control unit controls the phase of a third clock signal based on the phase difference between the first clock signal and the second clock signal during a first period based on pulse sequence information, and stops the phase control during a second period based on the pulse sequence information. The main unit-side clock transmission unit wirelessly transmits the third clock signal to the receiving coil unit. The main unit-side data communication unit receives the magnetic resonance signal wirelessly transmitted by the receiving coil unit. The image reconstruction unit processes the magnetic resonance signal to reconstruct an image of the subject. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows an example of the configuration of an MRI apparatus according to an embodiment. [Figure 2] Figure 2 is a block diagram showing the functional configuration of the receiving coil unit and wireless unit according to the embodiment. [Figure 3]Figure 3 is a block diagram showing the functional configuration of the receiving coil unit-side clock transmission unit and the main unit-side clock transmission unit according to the embodiment. [Figure 4] Figure 4 is a block diagram showing the functional configuration of the clock transmission unit on the main unit side according to the embodiment. [Figure 5] Figure 5 is a block diagram showing the functional configuration of the clock transmission unit on the receiving coil unit side according to the embodiment. [Figure 6] Figure 6 is a block diagram showing the functional configuration of the clock receiving section on the receiving coil unit side according to the embodiment. [Figure 7] Figure 7 is a timing diagram showing the pulse sequence of the gradient echo method according to the embodiment. [Figure 8] Figure 8 is a flowchart showing an example of the flow of wireless clock signal transmission and reception operation of the main unit according to the embodiment. [Figure 9] Figure 9 is a flowchart showing an example of the flow of wireless clock signal transmission and reception operation of the receiving coil unit according to the embodiment. [Modes for carrying out the invention]

[0009] The following describes in detail embodiments of an MRI apparatus and a control method for the MRI apparatus, with reference to the drawings.

[0010] (Embodiment) Figure 1 shows an example of the configuration of an MRI apparatus according to an embodiment.

[0011] As shown in Figure 1, the MRI apparatus consists of a main unit 101 and a receiving coil unit 102 which is separate from the main unit 101.

[0012] The main unit 101 includes a static magnetic field magnet 103, a gradient magnetic field coil 104, a gradient magnetic field power supply 105, a bed 106, a bed control unit 107, a transmitting coil 108, an RF pulse generation unit 109, an RF pulse / gradient magnetic field control unit 110, a clock generation unit 111, a wireless unit 112, a data analysis unit 113, a storage unit 114, a display unit 115, an input unit 116, and an imaging control unit 117.

[0013] The static magnetic field magnet 103 is a hollow cylinder that generates a uniform static magnetic field in its internal space. For example, a permanent magnet or a superconducting magnet can be used as this static magnetic field magnet 103.

[0014] The gradient magnetic field coil 104 is a hollow cylinder and is placed inside the static magnetic field magnet 103. The gradient magnetic field coil 104 is composed of three types of coils corresponding to the mutually orthogonal X, Y, and Z axes. The gradient magnetic field coil 104 generates gradient magnetic fields in which the magnetic field strength slopes along the X, Y, and Z axes, with the three types of coils receiving current individually from the gradient magnetic field power supply 105. The Z axis direction is, for example, the same direction as the static magnetic field direction. The gradient magnetic fields for the X, Y, and Z axes correspond to, for example, the slice selection gradient magnetic field Gs, the phase encoding gradient magnetic field Ge, and the readout gradient magnetic field Gr, respectively. The slice selection gradient magnetic field Gs is used to arbitrarily determine the imaging cross-section. The phase encoding gradient magnetic field Ge is used to change the phase of the magnetic resonance signal according to the spatial position. The readout gradient magnetic field Gr is used to change the frequency of the magnetic resonance signal according to the spatial position.

[0015] The bed 106 moves its top plate 106a in its longitudinal direction (left-right direction in Figure 1) and vertical direction under the control of the bed control unit 107. Typically, the bed 106 is positioned so that this longitudinal direction is parallel to the central axis of the static magnetic field magnet 103. The subject 118 is placed on the top plate 106a. By moving the top plate 106a, the bed 106 inserts the subject 118 into the space inside the gradient magnetic field coil 104 (imaging space).

[0016] The transmission coil 108 is configured by housing one or more coils in a cylindrical case. The transmission coil 108 is disposed inside the gradient magnetic field coil 104. The transmission coil 108 receives the supply of an RF pulse signal from the RF pulse generation unit 109 and radiates an RF pulse.

[0017] The RF pulse generation unit 109 generates an RF pulse signal.

[0018] The RF pulse and gradient magnetic field control unit 110 controls the gradient magnetic field power supply 105 and the RF pulse generation unit 109 according to the pulse sequence information input from the imaging control unit 117. Here, the pulse sequence information is information that defines the application timing of each gradient magnetic field and RF pulse.

[0019] Here, an example in which the main unit 101 has a so-called tunnel type structure including the static magnetic field magnet 103 having a hollow cylindrical shape, the gradient magnetic field coil 104, and the transmission coil 108 will be described, but the embodiment is not limited to this. For example, the main unit 101 may have a so-called open type structure in which a pair of static magnetic field magnets, a pair of gradient magnetic field coils, and a pair of transmission coils are arranged so as to face each other across the imaging space in which the subject 118 is disposed.

[0020] The reception coil unit 102 is placed on the top plate 106a, built in the top plate 106a, or attached to the subject 118. At the time of imaging, the reception coil unit 102 is inserted into the imaging space together with the subject 118, receives the magnetic resonance signal radiated from the subject 118, and obtains an electrical magnetic resonance signal. The reception coil unit 102 wirelessly transmits the data obtained by digitizing the magnetic resonance signal to the wireless unit 112. Further, the reception coil unit 102 synchronizes the system clocks of each other by transmitting and receiving a wireless clock signal to and from the wireless unit 112.

[0021] The clock generation unit 111 generates a first clock signal of a predetermined frequency. This first clock signal is supplied to the wireless unit 112. The first clock signal is also used as a system clock, which serves as the reference timing for the entire MRI device.

[0022] The data analysis unit 113 processes the obtained data to reconstruct an image of the subject 118. Here, the data analysis unit 113 is an example of an image reconstruction unit.

[0023] The storage unit 114 stores various types of data, such as image data representing the image reconstructed by the data analysis unit 113. The storage unit 114 can appropriately utilize semiconductor memory elements such as RAM (Random Access Memory) and flash memory, as well as storage devices such as hard disks and optical discs.

[0024] The display unit 115 displays various information, such as images reconstructed by the data analysis unit 113 and various operation screens for the user to operate the MRI device, under the control of the imaging control unit 117. The display unit 115 can utilize various display devices as appropriate, including liquid crystal displays, CRT (Cathode-Ray Tube) monitors, and touch panels.

[0025] The input unit 116 receives various commands and information inputs from the operator. The input unit 116 can utilize various input devices as appropriate, such as a pointing device like a mouse or trackball for setting imaging conditions and regions of interest (ROI), a selection device like a mode switch, a keyboard, a touchpad for input operations by touching the operating surface, a touchscreen integrating a display screen and touchpad, a non-contact input circuit using an optical sensor, and an audio input circuit. In this specification, the input unit 116 is not limited to those equipped with physical operating components such as a mouse or keyboard. For example, an electrical signal processing circuit that receives electrical signals corresponding to input operations from an external input device separate from the device and outputs these electrical signals to a control circuit is also included as an example of the input unit 116.

[0026] The imaging control unit 117 performs overall imaging control of the MRI system.

[0027] Here, for example, the bed control unit 107, RF pulse / gradient magnetic field control unit 110, data analysis unit 113, and imaging control unit 117 included in the main unit 101 described above are each implemented by a processor. In this case, the processing functions of each processing unit are stored in the storage unit 114 in the form of a program that can be executed by a computer. Each processing unit then reads and executes the program from the storage unit to realize the processing function corresponding to each program. Furthermore, each processing unit is not limited to being implemented by a single processor. For example, each processing unit may be composed of a combination of multiple independent processors, and each processor may realize each processing function by executing a program. Also, the processing functions of each processing unit may be implemented by integrating or distributing them as appropriate across one or more processors. Furthermore, although a single storage unit 114 is used here to store the programs corresponding to each processing function, the embodiments are not limited to this. For example, multiple storage units may be distributed among the processing units, and each processing unit may read the corresponding program from its individual storage unit.

[0028] Next, the functional configuration of the receiving coil unit 102 and the wireless unit 112 included in the main unit 101 will be described.

[0029] Figure 2 is a block diagram showing the functional configuration of the receiving coil unit 102 and the wireless unit 112 according to the embodiment. In Figure 2, the same parts as in Figure 1 are denoted by the same reference numerals.

[0030] As shown in Figure 2, the receiving coil unit 102 includes an RF receiving coil 201, an RF receiving section 202, an ADC 203, a data communication section 204, a data communication antenna 205, a receiving coil unit-side clock transmission section 206, a clock transmission antenna 207, and a control section 208. Here, the data communication section 204 is an example of a receiving coil unit-side data communication section.

[0031] The RF receiving coil 201 receives the magnetic resonance signal radiated as electromagnetic waves from the subject 118 and outputs an electrical magnetic resonance signal. Here, the RF receiving coil 201 is an example of a magnetic resonance signal detection unit.

[0032] The RF receiver 202 includes a variable amplifier that amplifies the magnetic resonance signal obtained by the RF receiver coil 201, and suppresses the effects of quantization errors by amplifying the magnetic resonance signal to an appropriate level before the ADC 203.

[0033] The ADC203 converts the magnetic resonance signal, which is an analog signal output from the RF receiver 202, to digital based on the sampling clock supplied by the control unit 208, obtaining data as a digital signal. Note that the ADC203 is an example of an analog-to-digital conversion unit.

[0034] The data communication unit 204 is composed of modulation / demodulation circuits, frequency conversion circuits, power amplification circuits, etc. The data communication unit 204 generates a communication frame by adding a header, etc., to the data input from the ADC 203. Then, it generates a wireless communication signal by performing modulation processing, frequency conversion processing, etc., on this communication frame and transmits it to the wireless unit 112 via the data communication antenna 205. The data communication unit 204 also receives the wireless communication signal transmitted from the data communication unit 222 via the data communication antenna 205. Then, it obtains received data by performing frequency conversion processing, demodulation processing, etc., on the received wireless communication signal. The data communication unit 204 may be configured to control wireless communication compliant with the IEEE 802.11 standard. The data communication unit 204 may also be configured to control wireless communication compliant with communication standards such as Bluetooth®, NFC, UWB, Zigbee, MBOA, etc. UWB is an abbreviation for Ultra Wide Band, and MBOA is an abbreviation for Multi Band OFDM Alliance. Here, OFDM is an abbreviation for Orthogonal Frequency Division Multiplexing. NFC is an abbreviation for Near Field Communication. UWB includes wireless USB, wireless 1394, Winet, etc.

[0035] The receiving coil unit-side clock transmission unit 206 mutually transmits and receives wireless clock signals with the main unit-side clock transmission unit 224. Here, the wireless clock signal is a wireless signal for synchronizing the system clocks of the main unit 101 and the receiving coil unit 102, and is transmitted and received via the clock transmission antenna 207. The receiving coil unit-side clock transmission unit 206 also generates a system clock from the wireless clock signal received by the clock transmission antenna 207 and outputs it to the control unit 208.

[0036] The control unit 208 controls the operation of the receiving coil unit 102 based on the system clock output by the receiving coil unit-side clock transmission unit 206. In addition, a PLL (Phase Locked Loop) circuit (not shown) generates a sampling clock from the system clock and outputs it to the ADC 203.

[0037] On the other hand, the wireless unit 112 of the main unit 101 is composed of a control unit 221, a data communication unit 222, a data communication antenna 223, a main unit-side clock transmission unit 224, and a clock transmission antenna 225. Here, the data communication unit 222 is an example of a main unit-side data communication unit.

[0038] The control unit 221 wirelessly transmits pulse sequence information input from the imaging control unit 117 to the receiving coil unit 102 via the data communication unit 222. The control unit 221 also controls the operation of the main unit-side clock transmission unit 224 based on the pulse sequence information.

[0039] The configuration of the data communication unit 222 and the data communication antenna 223 is the same as that of the data communication unit 204 and the data communication antenna 205. The data communication unit 222 receives wireless communication signals transmitted from the data communication unit 204 via the data communication antenna 223. It then acquires data from the received wireless communication signals and outputs it to the data analysis unit 113. The data communication unit 222 also generates wireless communication signals from pulse sequence information input from the control unit 221 and transmits them to the receiving coil unit 102 via the data communication antenna 223.

[0040] Next, the functional configurations of the receiving coil unit-side clock transmission unit 206 and the main unit-side clock transmission unit 224 will be described.

[0041] Figure 3 is a block diagram showing the functional configuration of the receiving coil unit-side clock transmission unit 206 and the main unit-side clock transmission unit 224 according to the embodiment.

[0042] As shown in Figure 3, the main unit-side clock transmission unit 224 is configured to include a clock phase control unit 301, a main unit-side clock transmission unit 302, and a main unit-side clock reception unit 303.

[0043] The clock phase control unit 301 generates a third clock signal Stx based on the first clock signal Sref input from the clock generation unit 111 and the second clock signal Sfb input from the main unit-side clock receiving unit 303. The clock phase control unit 301 then outputs the generated third clock signal Stx to the main unit-side clock transmitting unit 302.

[0044] The main unit's clock transmission unit 302 generates a wireless clock signal Sdl based on a third clock signal Stx input from the clock phase control unit 301 and transmits it from the clock transmission antenna 225a.

[0045] The main unit-side clock receiver 303 receives the wireless clock signal Sul transmitted from the receiving coil unit-side clock transmission unit 206 using the clock transmission antenna 225b. The main unit-side clock receiver 303 then generates a second clock signal Sfb from the received wireless clock signal Sul and outputs it to the clock phase control unit 301.

[0046] On the other hand, the receiving coil unit-side clock transmission unit 206 is configured to include a receiving coil unit-side clock receiving unit 304 and a receiving coil unit-side clock transmitting unit 305.

[0047] The receiving coil unit-side clock receiving unit 304 receives the wireless clock signal Sdl transmitted from the main unit-side clock transmission unit 224 using the clock transmission antenna 207a. It then generates a clock signal Srx as the system clock from this signal and outputs it to the control unit 208 and the receiving coil unit-side clock transmission unit 305, respectively.

[0048] The receiving coil unit-side clock transmitting unit 305 generates a wireless clock signal Sul based on the clock signal Srx input from the receiving coil unit-side clock receiving unit 304 and transmits it from the clock transmission antenna 207b. The transmission timing of the wireless clock signal Sul is controlled by the control unit 208.

[0049] Next, the functional configurations of the main unit-side clock transmission unit 302 and the receiving coil unit-side clock transmission unit 305 will be described.

[0050] Figure 4 is a block diagram showing the functional configuration of the main unit-side clock transmission unit 302 according to the embodiment.

[0051] As shown in Figure 4, the main unit-side clock transmission unit 302 is configured to include a carrier signal generation unit 401, a frequency mixing unit 402, and an amplification unit 403.

[0052] The carrier signal generation unit 401 is composed of a PLL circuit or the like, and multiplies the third clock signal Stx input from the clock phase control unit 301 to generate a carrier signal in the radio frequency band.

[0053] The frequency mixing unit 402 is composed of a DBM (Double Balanced Mixer) circuit or the like, and multiplies the third clock signal Stx with the carrier signal and outputs it to the amplification unit 403. In other words, in this embodiment, the wireless clock signal is an amplitude-modulated signal with the third clock signal Stx as the baseband signal.

[0054] The amplification unit 403 amplifies the signal input from the frequency mixing unit 402 and transmits it as a wireless clock signal Sdl from the clock transmission antenna 225a.

[0055] Figure 5 is a block diagram showing the functional configuration of the receiving coil unit-side clock transmission unit 305 according to the embodiment. In Figure 5, elements identical to those in the main unit-side clock transmission unit 302 are denoted by the same reference numerals, and redundant explanations are omitted.

[0056] As shown in Figure 5, the configuration of the receiving coil unit-side clock transmission unit 305 is the same as that of the main unit-side clock transmission unit 302. However, each component of the receiving coil unit-side clock transmission unit 305 can be temporarily stopped based on the control of the control unit 208 to reduce power consumption.

[0057] Next, the functional configurations of the receiving coil unit-side clock receiving unit 304 and the main unit-side clock receiving unit 303 will be described.

[0058] Figure 6 is a block diagram showing the functional configuration of the clock receiving unit 304 on the receiving coil unit side according to the embodiment.

[0059] As shown in Figure 6, the receiving coil unit-side clock receiving section 304 is configured to include a variable gain amplifier section 601, a detection section 602, and a waveform shaping section 603.

[0060] The variable gain amplifier 601 adjusts the level of the wireless clock signal Sdl received by the clock transmission antenna 207a.

[0061] The detection unit 602 is composed of a diode detection circuit or a square detection circuit and an LPF (Low Pass Filter), and performs envelope detection on the wireless clock signal Sdl to extract the clock signal component.

[0062] The waveform shaping unit 603 is composed of a hysteresis comparator circuit, a PLL circuit, etc., and generates a clock signal Srx by shaping the output signal of the detection unit 602. The waveform shaping unit 603 then outputs the generated clock signal Srx as the system clock to the control unit 208 and the receiving coil unit side clock transmission unit 305, respectively.

[0063] The configuration of the clock receiver 303 on the main unit side is the same as that of the clock receiver 304 on the receiving coil unit side. The clock receiver 303 on the main unit side generates a second clock signal Sfb from the wireless clock signal Sul and outputs the generated second clock signal Sfb to the clock phase control unit 301.

[0064] Next, we will explain the detailed operation of the clock phase control unit 301.

[0065] If the phases of the second clock signal Sfb, the third clock signal Stx, and the clock signal Srx generated by the receiving coil unit-side clock receiving section 304 are θsfb, θstx, and θsrx, respectively, then the phase relationship of each clock signal can be expressed by the following equations 1 and 2.

[0066] θsrx = θstx - (θdtx + θdl + θdrx)...Equation 1 θsfb = θsrx - (θutx + θul + θurx)...Equation 2

[0067] Here, θdtx and θdrx are phase differences caused by the circuit operation of the main unit-side clock transmitter 302 and the receiving coil unit-side clock receiver 304, respectively, and θdl is a phase difference caused by the wireless propagation path. Similarly, θutx and θurx are phase differences caused by the circuit operation of the receiving coil unit-side clock transmitter 305 and the main unit-side clock receiver 303, respectively, and θul is a phase difference caused by the wireless propagation path.

[0068] Furthermore, if the main unit-side clock transmitter 302 and the receiving coil unit-side clock transmitter 305 have the same configuration, and the main unit-side clock receiver 303 and the receiving coil unit-side clock receiver 304 have the same configuration, the resulting phase difference θcirciut can be expressed as shown in Equation 3 below. Also, since the wireless propagation path is symmetrical, the resulting phase difference θlink can be expressed as shown in Equation 4 below. Note that the phase difference θlink caused by the wireless propagation path also includes phase fluctuations due to fading, for example, caused by the movement of the subject 118.

[0069] θdtx + θdrx = θutx + θurx = θcirciut...Equation 3 θdl = θul = θlink...Equation 4

[0070] Furthermore, from equations 1 and 2, θsrx can be expressed by the following equation 5.

[0071] θsrx = (θstx + θsfb) / 2...Equation 5

[0072] Here, if we let θsref be the phase of the first clock signal Sref, and assume that θstx is expressed by the following equation 6, then θsrx = θsref, and the clock signal on the receiving coil unit side can be synchronized with the clock signal on the main unit side without being affected by fading due to the wireless propagation path.

[0073] θstx = 2×θsref - θsfb...Equation 6

[0074] The clock phase control unit 301 operates to satisfy the conditions of Equation 6 and generates a third clock signal Stx based on the first clock signal Sref and the second clock signal Sfb.

[0075] More specifically, the clock phase control unit 301 detects the phase difference Δθ = θsref - θsfb between Sref and Sfb, and generates a clock signal Stx (θstx = θsref + Δθ = 2×θsref - θsfb) by advancing the phase of Sref by Δθ.

[0076] Furthermore, the clock phase control unit 301 operates based on the control of the control unit 221, and detects Δθ only during the period when the wireless clock signal Sul is being received, and during other periods it retains the value of Δθ that was detected immediately before. In other words, the clock phase control unit 301 controls the phase of Stx to suppress the effects of fading only during the period when the wireless clock signal Sul is being received, and stops controlling the phase of Stx during other periods.

[0077] Here, for example, the RF pulse generation unit 109, clock generation unit 111 and wireless unit 112 included in the main unit 101, the control unit 221, data communication unit 222 and main unit side clock transmission unit 224 included in the wireless unit 112, the RF receiving unit 202, ADC 203, data communication unit 204, receiving coil unit side clock transmission unit 206 and control unit 208 included in the receiving coil unit 102, the clock phase control unit 301 included in the main unit side clock transmission unit 224, the main unit side clock transmission unit 302 and main unit side clock receiving unit 303, receiving The receiving coil unit side clock receiving unit 304 and receiving coil unit side clock transmitting unit 305 included in the coil unit side clock transmission unit 206, the carrier signal generation unit 401, frequency mixing unit 402 and amplification unit 403 included in the main unit side clock transmitting unit 302 and the receiving coil unit side clock transmitting unit 305, and the variable gain amplification unit 601, detection unit 602 and waveform shaping unit 603 included in the main unit side clock receiving unit 303 and the receiving coil unit side clock receiving unit 304 are each implemented by processing circuits having the processing functions described above. In this case, the processing circuit means, for example, an application-specific integrated circuit (ASIC), a programmable logic device (e.g., a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA)). For example, if the processing circuit is an ASIC, the processing functions are directly incorporated into the processing circuit as logic circuits. Note that the processing circuit is not limited to being configured as a single circuit for each processing unit; it may also be configured as a single processing circuit by combining multiple independent circuits to realize its processing functions. Furthermore, the multiple components shown in Figure 4 may be integrated into a single processing circuit to realize its processing functions.

[0078] The operation of the main unit 101 and the receiving coil unit 102 in the MRI apparatus according to this embodiment, which has the above configuration, will now be described.

[0079] Figure 7 is a timing diagram showing the pulse sequence of the gradient echo method according to the embodiment. In Figure 7, the top row shows the RF pulse, the second row from the top shows the gradient magnetic field Gs for slice selection, the third row from the top shows the gradient magnetic field Ge for phase encoding, the fourth row from the top shows the gradient magnetic field Gr for readout, the fifth row from the top shows the magnetic resonance signal, the sixth row from the top shows the wireless clock signal Sdl, and the bottom row shows the wireless clock signal Sul.

[0080] As shown in Figure 7, in the pulse sequence of the gradient echo method, first, an excitation RF pulse 702 with a flip angle of, for example, 90° is transmitted to the imaging area simultaneously with the application of a slice selection gradient magnetic field pulse Gs701 with, for example, a positive polarity. Next, as the transmission of the excitation RF pulse 702 stops, a slice selection gradient magnetic field pulse Gs703 with reversed polarity is applied. The slice selection gradient magnetic field pulse Gs703 is called a rephasing lobe, and its application period is approximately half the application period of the slice selection gradient magnetic field pulse Gs701 before polarity reversal. Next, a phase encoding gradient magnetic field Ge704 and a readout gradient magnetic field Gr705 with, for example, a negative polarity are applied. Next, a readout gradient magnetic field Gr706 with reversed polarity is applied. Then, a magnetic resonance signal 707 is emitted from the subject 118 around the timing of the echo time TE, and the magnetic resonance signal 707 is detected by the RF receiving coil 201 under the application of the readout gradient magnetic field Gr706. Next, after the application of the readout gradient magnetic field Gr706 is complete, a phase encoding gradient magnetic field Ge708 is applied, which has the opposite polarity to the phase encoding gradient magnetic field Ge704 that was applied earlier. This eliminates the influence of the phase encoding gradient magnetic field Ge704 that was applied before the detection of the magnetic resonance signal 707, before the acquisition of the magnetic resonance signal in the next phase encoding step. This completes the acquisition of the magnetic resonance signal for one phase encoding step (1 cycle), which is the processing within one repetition time TR in Figure 7. This 1 cycle is repeated the same number of times as the number of phase encoding steps, thereby acquiring the magnetic resonance signal for one image.

[0081] For example, in the pulse sequence described above, the main unit's clock transmission unit 224 continuously transmits the wireless clock signal Sdl709. Meanwhile, the receiving coil unit 102 generates a system clock from the wireless clock signal Sdl709 and converts the magnetic resonance signal from analog to digital based on the sampling clock obtained from the system clock. In this environment, where fading due to the wireless propagation path does not occur, the receiving coil unit 102 can obtain a system clock synchronized with the system clock of the main unit 101.

[0082] However, in an MRI system, phase shifts can occur in these clocks if fading occurs, for example, due to the movement of the subject 118. If this clock phase shift occurs during the period in which the magnetic resonance signal 707 is converted from analog to digital (i.e., the period during which the readout gradient magnetic field Gr706 is applied), it will lead to a decrease in the accuracy of the reconstructed image.

[0083] This clock phase shift due to fading can be suppressed by the operation of the aforementioned clock phase control unit 301. However, the power consumption of the receiving coil unit 102 increases due to the transmission of the wireless clock signal Sul, and this increase in power consumption is undesirable for the battery-powered receiving coil unit 102.

[0084] Therefore, in this embodiment, the receiving coil unit 102 operates to intermittently transmit the wireless clock signal Sul710. This suppresses the clock phase shift during the analog-to-digital conversion of the magnetic resonance signal 707 while keeping the power consumption of the receiving coil unit 102 low. Note that the clock phase shift due to fading is suppressed after the operation response time of the main unit-side clock transmitter 302, the main unit-side clock receiver 303, the receiving coil unit-side clock transmitter 305, and the receiving coil unit-side clock receiver 304, as well as the wireless signal propagation time, has elapsed since the start of transmission of the wireless clock signal Sul. For this reason, it is desirable to start transmitting the wireless clock signal Sul710 before starting the analog-to-digital conversion of the magnetic resonance signal 707, taking these factors into consideration.

[0085] Therefore, Figure 7 shows an example in which the transmission of the wireless clock signal Sul710 is started a predetermined time ΔT before the timing of starting the analog-to-digital conversion of the magnetic resonance signal 707. Here, ΔT is set to a value greater than or equal to the sum of the operating response time of each part and the wireless signal propagation time.

[0086] In this embodiment, for the sake of simplicity, a pulse sequence of the gradient echo method was used for explanation. However, the intermittent transmission operation of the wireless clock signal Sul described above is similarly applicable to other pulse sequences such as the spin echo method.

[0087] Figure 8 is a flowchart illustrating an example of the wireless clock signal transmission and reception operation of the main unit 101 according to this embodiment. This flowchart is executed after the subject 118, equipped with the receiving coil unit 102, is inserted into the imaging space.

[0088] As shown in Figure 8, in step S801, the imaging control unit 117 determines the pulse sequence to be used for imaging and a predetermined time ΔT, and notifies the control unit 221 of the determined pulse sequence information and predetermined time ΔT.

[0089] In step S802, the control unit 221 starts transmitting the wireless clock signal Sdl from the main unit-side clock transmission unit 302. The control unit 221 also transmits data indicating a request to transmit the wireless clock signal Sul from the data communication unit 222 to the receiving coil unit 102, and enables clock phase control by the clock phase control unit 301.

[0090] In step S803, the control unit 221 transmits pulse sequence information and a predetermined time ΔT from the data communication unit 222 to the receiving coil unit 102, and then starts pulse sequence operation based on these to begin capturing magnetic resonance images.

[0091] In step S804, the control unit 221 determines whether or not it is the ON period for transmitting the wireless clock signal Sul, based on the pulse sequence and a predetermined time ΔT.

[0092] Specifically, the control unit 221 sets the transmission ON period and the transmission OFF period of the wireless clock signal Sul based on pulse sequence information and a predetermined time ΔT. Here, the control unit 221 is an example of a period setting unit on the main unit side. The transmission ON period of the wireless clock signal Sul is an example of a first period, and the transmission OFF period of the wireless clock signal Sul is an example of a second period.

[0093] In this embodiment, the control unit 221 sets a predetermined time ΔT added before the period for converting the magnetic resonance signal 707 included in the pulse sequence information from analog to digital as the ON period for transmitting the wireless clock signal Sul, and sets the other period as the OFF period for transmitting the wireless clock signal Sul.

[0094] Then, the control unit 221 proceeds to step S805 if it is the ON period for transmitting the wireless clock signal Sul, and to step S806 if it is the OFF period for transmitting the wireless clock signal Sul.

[0095] In step S805, during the ON period for transmitting the wireless clock signal Sul, the control unit 221 enables phase control by the clock phase control unit 301.

[0096] In step S806, during the transmission OFF period of the wireless clock signal Sul, the control unit 221 disables the phase control by the clock phase control unit 301.

[0097] In step S807, the control unit 221 determines whether the acquisition of magnetic resonance signals for all phase encoding steps has been completed. If the control unit 221 determines that the acquisition of magnetic resonance signals for all phase encoding steps has not been completed, it returns to step S804 and continues the pulse sequence operation. If the control unit 221 determines that the acquisition of magnetic resonance signals for all phase encoding steps has been completed, it terminates the pulse sequence operation.

[0098] Figure 9 is a flowchart showing an example of the flow of wireless clock signal transmission and reception operation of the receiving coil unit 102 according to this embodiment.

[0099] As shown in Figure 9, in step S901, the control unit 208 waits until it receives a request from the main unit 101 to transmit the wireless clock signal Sul.

[0100] In step S902, when the control unit 208 receives a request from the main unit 101 to transmit the wireless clock signal Sul, it starts transmitting the wireless clock signal Sul.

[0101] In step S903, the control unit 208 waits until it receives pulse sequence information and ΔT from the main unit 101, and when it receives them, it starts the pulse sequence operation.

[0102] In step S904, the control unit 208 determines whether or not it is the ON period for transmitting the wireless clock signal Sul, based on the pulse sequence and a predetermined time ΔT.

[0103] Specifically, the control unit 208 sets the transmission ON period and the transmission OFF period of the wireless clock signal Sul based on pulse sequence information and a predetermined time ΔT. Here, the control unit 208 is an example of a period setting unit on the receiving coil unit side. The transmission ON period of the wireless clock signal Sul is an example of the first period, and the transmission OFF period of the wireless clock signal Sul is an example of the second period.

[0104] In this embodiment, the control unit 208 sets a predetermined time ΔT added before the period for converting the magnetic resonance signal 707 included in the pulse sequence information from analog to digital as the ON period for transmitting the wireless clock signal Sul, and sets the other period as the OFF period for transmitting the wireless clock signal Sul.

[0105] Then, the control unit 208 proceeds to step S905 if it is the ON period for transmitting the wireless clock signal Sul, and to step S906 if it is the OFF period for transmitting the wireless clock signal Sul.

[0106] In step S905, during the ON period for transmitting the wireless clock signal Sul, the control unit 208 enables the receiving coil unit-side clock transmission unit 305 and transmits the wireless clock signal Sul.

[0107] In step S906, during the period when the transmission of the wireless clock signal Sul is OFF, the control unit 208 disables the receiving coil unit side clock transmission unit 305 and stops the transmission of the wireless clock signal Sul.

[0108] In step S907, the control unit 208 determines whether the acquisition of magnetic resonance signals for all phase encoding steps has been completed. If the control unit 208 determines that the acquisition of magnetic resonance signals for all phase encoding steps has not been completed, it returns to step S904 and continues the pulse sequence operation. If the control unit 208 determines that the acquisition of magnetic resonance signals for all phase encoding steps has been completed, it terminates the pulse sequence operation.

[0109] The operation of the main unit 101 and the receiving coil unit 102 described above enables the transmission and reception of the wireless clock signal at the timing illustrated in Figure 7. This makes it possible to suppress the clock phase shift during the period in which the magnetic resonance signal 707 is converted from analog to digital, while keeping the power consumption of the receiving coil unit 102 low.

[0110] (Modified version of the embodiment) In this embodiment, the main unit 101 notifies the receiving coil unit 102 of pulse sequence information and ΔT, but the embodiment is not limited to this. For example, the receiving coil unit 102 may be equipped with a UI (User Interface), and the operator may set the pulse sequence information and ΔT using this UI.

[0111] Furthermore, in this embodiment, wireless signals are transmitted and received via three links: between the data communication unit 204 and the data communication unit 222, between the main unit-side clock transmission unit 302 and the receiving coil unit-side clock reception unit 304, and between the receiving coil unit-side clock transmission unit 305 and the main unit-side clock reception unit 303. However, it is desirable that the wireless signals of each link be isolated so as not to affect each other. For example, it is possible to use the FDM (Frequency Division Multiplexing) method, which ensures isolation by using different carrier frequencies for each link. Alternatively, the SDM (Space Division Multiplexing) method may be used to ensure isolation by the antenna directivity of each link. In addition, when isolating each link using the FDM method, the antennas of each link may be shared by using filter elements such as diplexers or triplexers.

[0112] Furthermore, although this embodiment has been described assuming that the wireless clock signal is an amplitude-modulated signal, the embodiment is not limited to this, and a frequency-modulated signal may also be used. In this case, for example, the clock transmission unit is configured to generate a frequency-modulated baseband signal using the third clock signal Stx as the signal wave and input this to the frequency mixing unit 402. In addition, the detection unit 602 is configured with a PLL circuit or the like, and the clock signal component is extracted by PLL detection.

[0113] Furthermore, in this embodiment, the clock signal is generated by the detection process of the detection unit 602, but the embodiment is not limited to this, and the clock signal may be generated from the carrier signal. In this case, the detection unit 602 is changed to a clock regeneration unit consisting of, for example, a Costas loop circuit and a frequency divider circuit. This makes it possible to regenerate the carrier signal from the wireless clock signal and generate a clock signal with the same frequency as the system clock by dividing it.

[0114] Furthermore, in this embodiment, a predetermined time ΔT is set to a value greater than or equal to the sum of the operating response time and wireless signal propagation time of the main unit-side clock transmitter 302, the main unit-side clock receiver 303, the receiving coil unit-side clock transmitter 305, and the receiving coil unit-side clock receiver 304. However, the embodiment is not limited to this. For example, a ΔT setting step may be added after step S802 in Figure 8 to determine the time to be set as ΔT by measurement. In this case, for example, in the ΔT setting step, the control unit 221 instructs the clock phase control unit 301 to change the phase of the third clock signal Stx. This phase change will appear in the second clock signal Sfb after the operating response time and wireless signal propagation time in each unit have elapsed. Using this, the control unit 221 measures the operation response time and wireless signal propagation time from the time the phase control of the third clock signal Stx is started by the clock phase control unit 301 until the phase control appears as a phase change of the second clock signal Sfb, and determines a predetermined time ΔT based on the measurement results of the operation response time and wireless signal propagation time. Here, the control unit 221 is an example of a time measurement unit.

[0115] In this embodiment, ΔT is set to a value greater than or equal to the sum of the operation response time and wireless signal propagation time of the main unit-side clock transmitter 302, the main unit-side clock receiver 303, the receiving coil unit-side clock transmitter 305, and the receiving coil unit-side clock receiver 304. The control unit 221 of the main unit 101 and the control unit 208 of the receiving coil unit 102 set the period obtained by adding a predetermined time ΔT before the period for analog-to-digital conversion of the magnetic resonance signal 707 included in the pulse sequence information as the transmission ON period for the wireless clock signal Sul. However, the embodiment is not limited to this. For example, ΔT may be set to a value greater than or equal to the operation response time of each part, or to a value greater than or equal to the wireless signal propagation time. Also, for example, the control unit 221 and the control unit 208 may set the period obtained by analog-to-digital conversion of the magnetic resonance signal 707 included in the pulse sequence information, or the period obtained by adding a preparation period of a predetermined length before said period, as the transmission ON period for the wireless clock signal Sul. In other words, the control unit 221 and the control unit 208 only need to determine the first period based on the period for converting the magnetic resonance signal included in the pulse sequence information from analog to digital, the operational response time of the main unit-side clock transmitter 302, the main unit-side clock receiver 303, the receiving coil unit-side clock transmitter 305, and the receiving coil unit-side clock receiver 304, and the radio signal propagation time.

[0116] Furthermore, in this embodiment, the control unit 208 of the receiving coil unit 102 sets the transmission ON period and transmission OFF period of the wireless clock signal Sul based on the pulse sequence information and predetermined time ΔT transmitted from the control unit 221 of the main unit 101, but the embodiment is not limited to this. For example, the control unit 221 of the main unit 101 may transmit the transmission ON period and transmission OFF period of the wireless clock signal Sul set on the main unit 101 side to the receiving coil unit 102. In this case, the control unit 208 of the receiving coil unit 102 controls the transmission of the wireless clock signal Sul by the clock transmission unit 305 on the receiving coil unit side using the transmission ON period and transmission OFF period transmitted from the control unit 221 of the main unit 101.

[0117] Furthermore, in this embodiment, the period including the time for analog-to-digital conversion of the magnetic resonance signal 707 is set as the transmission ON period for the wireless clock signal Sul, but the embodiment is not limited to this. For example, the transmission ON period for the wireless clock signal Sul may be set to include a period other than the time for analog-to-digital conversion of the magnetic resonance signal 707, as long as it is possible to improve the accuracy of the reconstructed image by reducing the clock phase shift during that period.

[0118] Furthermore, although this embodiment describes an example where the receiving coil unit communicates data and clock wirelessly, wireless and wired receiving coil units may coexist. In this wired receiving coil unit, the magnetic resonance signal is sent from the receiving coil unit to the main unit as an analog signal, and the main unit performs analog-to-digital conversion using a sampling clock generated from the system clock on the main unit side. For example, when imaging a body part, a wired receiving unit may be used as the coil unit placed on the back side, and a wireless type may be used as the coil unit placed on the front side. This is because placing a wireless receiving coil unit on the front side is more effective in terms of clinical usability. Such cases where wireless and wired types coexist may exist as a transition period in which MRI systems as products are being replaced from conventional types that use wired receiving coil units to devices that use wireless receiving coil units. Also, when considering the overall system cost, it may be cheaper to manufacture by using a mix of types.

[0119] Furthermore, although this embodiment assumes that the receiving coil unit 102 is battery-powered, the embodiment is not limited to this. For example, the configuration of the receiving coil unit 102 described in this embodiment can be similarly applied even when the receiving coil unit 102 is configured to be powered by a power supply provided by the main unit 101. In that case, the requirement for low power consumption is considered to be lower compared to battery power, but as described above, by performing phase control of the clock signal only for a specific period based on pulse sequence information, it is possible to expect at least the effect of suppressing heat generation in the receiving coil unit 102.

[0120] Furthermore, while the above description illustrates an example in which the "processor" reads and executes programs corresponding to each processing function from the memory unit, the embodiments are not limited to this. The term "processor" refers to circuits such as a CPU (Central Processing Unit), GPU (Graphics Processing Unit), ASIC, and programmable logic device (e.g., SPLD, CPLD, and FPGA). When the processor is a CPU, for example, it realizes each processing function by reading and executing programs stored in the memory unit. On the other hand, when the processor is an ASIC, instead of storing programs in the memory unit, the processing function is directly incorporated as a logic circuit within the processor's circuit. In this embodiment, each processor is not limited to being configured as a single circuit; multiple independent circuits may be combined to form a single processor and realize its processing function. Furthermore, the multiple components shown in Figure 1 may be integrated into a single processor to realize its processing function.

[0121] Here, the program executed by the processor is provided pre-loaded into ROM (Read Only Memory) or a storage unit. This program may also be provided as a file in an installable or executable format on a computer-readable storage medium such as a CD (Compact Disk)-ROM, FD (Flexible Disk), CD-R (Recordable), or DVD (Digital Versatile Disk). Alternatively, this program may be stored on a computer connected to a network such as the Internet and provided or distributed by downloading it via the network. For example, this program consists of modules containing the various functional units described above. In actual hardware, the CPU reads the program from a storage medium such as ROM and executes it, loading each module onto the main memory and generating it in the main memory.

[0122] According to at least one embodiment described above, it is possible to reduce the power consumption of the receiving coil unit, reduce clock phase shift due to fading, and improve the accuracy of the reconstructed image.

[0123] While several embodiments 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, modifications, and combinations of embodiments 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. [Explanation of Symbols]

[0124] 101 Main Unit 111 Clock generation unit 113 Data Analysis Department (Image Reconstruction Department) 221 Control Unit (Main Unit Side Period Setting Unit, Time Measurement Unit) 222 Data communication section (Main unit side data communication section) 301 Clock Phase Control Unit 302 Main unit side clock transmission section 303 Main unit side clock receiver 102 Receiving Coil Unit 201 RF receiving coil (magnetic resonance signal detection unit) 203 ADC (Analog-to-Digital Converter) 204 Data communication section (receiving coil unit side data communication section) 208 Control Unit (Receiver Coil Unit Side Period Setting Unit) 304 Receiving coil unit side clock receiving section 305 Receiver coil unit side clock transmission section

Claims

1. A magnetic resonance imaging apparatus including a main unit and a receiving coil unit separate from the main unit, The aforementioned main unit is A clock generation unit that generates the first clock signal, The main unit-side clock receiving unit receives a clock signal wirelessly transmitted by the receiving coil unit and generates a second clock signal, A clock phase control unit that, in a first period based on pulse sequence information, controls the phase of a third clock signal based on the phase difference between the first clock signal and the second clock signal, and stops the phase control in a second period based on the pulse sequence information, The main unit side clock transmission unit wirelessly transmits the third clock signal to the receiving coil unit, The main unit side data communication unit receives the magnetic resonance signal wirelessly transmitted by the receiving coil unit, An image reconstruction unit that processes the magnetic resonance signal to reconstruct an image of the subject. A magnetic resonance imaging system equipped with the following features.

2. A magnetic resonance imaging apparatus including a main unit and a receiving coil unit separate from the main unit, The receiving coil unit is The receiving coil unit side clock receiving section receives the clock signal wirelessly transmitted by the main unit, A magnetic resonance signal detection unit receives a magnetic resonance signal emitted as electromagnetic waves from a subject and outputs an electrical magnetic resonance signal, An analog-to-digital conversion unit that digitizes the magnetic resonance signal in synchronization with a clock signal wirelessly transmitted by the main unit, A receiving coil unit side data communication unit that wirelessly transmits the digitized magnetic resonance signal to the main unit, A clock transmission unit on the receiving coil unit side wirelessly transmits a clock signal wirelessly transmitted by the main unit to the main unit during a first period based on pulse sequence information, receives a third clock signal wirelessly transmitted from the main unit with phase control performed based on the phase difference between the first clock signal generated by the main unit and a second clock signal generated based on the clock signal wirelessly transmitted by the receiving coil unit, digitizes the magnetic resonance signal in synchronization with the third clock signal, and stops wirelessly transmitting the clock signal wirelessly transmitted by the main unit during a second period based on pulse sequence information. A magnetic resonance imaging system equipped with the following features.

3. A magnetic resonance imaging apparatus including a main unit and a receiving coil unit separate from the main unit, The aforementioned main unit is A clock generation unit that generates the first clock signal, The main unit-side clock receiving unit receives a clock signal wirelessly transmitted by the receiving coil unit and generates a second clock signal, A clock phase control unit that, in a first period based on pulse sequence information, controls the phase of a third clock signal based on the phase difference between the first clock signal and the second clock signal, and stops the phase control in a second period based on the pulse sequence information, The main unit side clock transmission unit wirelessly transmits the third clock signal to the receiving coil unit, The main unit side data communication unit receives the magnetic resonance signal wirelessly transmitted by the receiving coil unit, An image reconstruction unit that processes the magnetic resonance signal to reconstruct an image of the subject. Equipped with, The receiving coil unit is The receiving coil unit side clock receiving section receives the clock signal wirelessly transmitted by the main unit, A magnetic resonance signal detection unit receives a magnetic resonance signal emitted as electromagnetic waves from the subject and outputs an electrical magnetic resonance signal. An analog-to-digital conversion unit that digitizes the magnetic resonance signal in synchronization with a clock signal wirelessly transmitted by the main unit, A receiving coil unit side data communication unit that wirelessly transmits the digitized magnetic resonance signal to the main unit, A receiving coil unit-side clock transmission unit that, during the first period, wirelessly transmits the clock signal wirelessly transmitted by the main unit to the main unit, and during the second period, stops wirelessly transmitting the clock signal wirelessly transmitted by the main unit. A magnetic resonance imaging system equipped with the following features.

4. The main unit's data communication unit wirelessly transmits the pulse sequence information to the receiving coil unit before the start of magnetic resonance image acquisition. The receiving coil unit side data communication unit receives the pulse sequence information wirelessly transmitted by the main unit. The magnetic resonance imaging apparatus according to claim 3.

5. The main unit further includes a main unit-side period setting unit that sets the first period and the second period based on the pulse sequence information. A magnetic resonance imaging apparatus according to any one of claims 1 to 4.

6. The receiving coil unit further includes a receiving coil unit-side period setting unit that sets the first period and the second period based on the pulse sequence information. A magnetic resonance imaging apparatus according to any one of claims 1 to 4.

7. The main unit further comprises a main unit-side period setting unit that sets the first period and the second period based on the pulse sequence information. The receiving coil unit further includes a receiving coil unit-side period setting unit that sets the first period and the second period based on the pulse sequence information. The magnetic resonance imaging apparatus according to claim 3 or 4.

8. The main unit-side period setting unit and the receiving coil unit-side period setting unit set the first period based on at least one of the following: the period for converting the magnetic resonance signal included in the pulse sequence information from analog to digital; the operating response time of the main unit-side clock transmission unit, the main unit-side clock reception unit, the receiving coil unit-side clock transmission unit, and the receiving coil unit-side clock reception unit; and the radio signal propagation time. The magnetic resonance imaging apparatus according to claim 7.

9. The main unit further includes a time measurement unit that measures the operation response time and wireless signal propagation time from the start of the phase control until the phase control appears as a phase change of the second clock signal. The main unit's data communication unit wirelessly transmits the measurement results of the operation response time and the wireless signal propagation time to the receiving coil unit before the start of magnetic resonance image acquisition. The receiving coil unit side data communication unit receives the measurement result wirelessly transmitted by the main unit, The main unit-side period setting unit and the receiving coil unit-side period setting unit set the first period based on the period for converting the magnetic resonance signal included in the pulse sequence information from analog to digital and the measurement result. The magnetic resonance imaging apparatus according to claim 7.

10. A control method for a magnetic resonance imaging apparatus including a main unit and a receiving coil unit separate from the main unit, The aforementioned main unit, Generate the first clock signal, The receiving coil unit receives the clock signal transmitted wirelessly and generates a second clock signal. During a first period based on pulse sequence information, the phase control of the third clock signal is performed based on the phase difference between the first clock signal and the second clock signal, and during a second period based on pulse sequence information, the phase control is stopped. The third clock signal is wirelessly transmitted to the receiving coil unit. The receiving coil unit receives the magnetic resonance signal transmitted wirelessly, The magnetic resonance signal is processed to reconstruct an image of the subject. A method for controlling a magnetic resonance imaging apparatus, including the following.

11. A control method for a magnetic resonance imaging apparatus including a main unit and a receiving coil unit separate from the main unit, The receiving coil unit, The main unit receives the clock signal transmitted wirelessly, It receives magnetic resonance signals emitted as electromagnetic waves from the subject and outputs an electrical magnetic resonance signal. The magnetic resonance signal is digitized in synchronization with the clock signal wirelessly transmitted by the main unit. The digitized magnetic resonance signal is wirelessly transmitted to the main unit. During a first period based on pulse sequence information, the clock signal transmitted wirelessly by the main unit is wirelessly transmitted to the main unit, a third clock signal is received from the main unit after phase control is performed based on the phase difference between the first clock signal generated by the main unit and the second clock signal generated based on the clock signal wirelessly transmitted by the receiving coil unit, the magnetic resonance signal is digitized in synchronization with the third clock signal, and during a second period based on pulse sequence information, the wireless transmission of the clock signal wirelessly transmitted by the main unit is stopped. A method for controlling a magnetic resonance imaging apparatus, including the following.

12. A control method for a magnetic resonance imaging apparatus including a main unit and a receiving coil unit separate from the main unit, The receiving coil unit, During a first period based on pulse sequence information, the clock signal transmitted wirelessly by the main unit is transmitted wirelessly to the main unit, and during a second period based on pulse sequence information, the wireless transmission of the clock signal transmitted wirelessly by the main unit is stopped. The aforementioned main unit, Generate the first clock signal, The receiving coil unit receives the clock signal transmitted wirelessly and generates a second clock signal. During the first period, the phase control of the third clock signal is performed based on the phase difference between the first clock signal and the second clock signal, and during the second period, the phase control is stopped. The third clock signal is wirelessly transmitted to the receiving coil unit. The receiving coil unit, The main unit receives the clock signal transmitted wirelessly, It receives magnetic resonance signals emitted as electromagnetic waves from the subject and outputs an electrical magnetic resonance signal. The magnetic resonance signal is digitized in synchronization with the clock signal wirelessly transmitted by the main unit. The digitized magnetic resonance signal is wirelessly transmitted to the main unit. The aforementioned main unit, The receiving coil unit receives the magnetic resonance signal transmitted wirelessly, The magnetic resonance signal is processed to reconstruct an image of the subject. A method for controlling a magnetic resonance imaging apparatus, including the following.

Images