JP2021023674A - Magnetic resonance imaging apparatus - Google Patents

Abstract

To appropriately correct MR data in magnetic resonance imaging using a coil unit having an A/D converter built therein.SOLUTION: A magnetic resonance imaging apparatus comprises a reception circuit 109 that receives a signal output from a coil unit and performs signal processing. The coil unit comprises at least one RF coil element 201 to 216, at least one A/D converter 401 to 416 for converting an analog signal output from the at least one RF coil element 201 to 216 to a digital signal, and a storage unit for storing information on an apparatus characteristic, and outputs the digital signals in association with the information on the apparatus characteristic. Using the information on the apparatus characteristic associated with the digital signals, the reception circuit 109 corrects the digital signals output from the coil unit.SELECTED DRAWING: Figure 7

Description

Embodiments of the present invention relate to a magnetic resonance imaging apparatus.

The magnetic resonance imaging apparatus reduces the number of channels by thinning out the MR signals of a plurality of channels obtained by the coil unit in, for example, an analog switch matrix in the magnetic resonance imaging apparatus main body. The thinned MR signal is converted into MR data via a gain block and an A / D converter. The gain block has a gain adjusting role of amplifying the MR signal so as to withstand the quantization error in the A / D conversion.

Further, in the gain block, a gain error and a phase error occur in the MR data according to the gain set value, and it is necessary to correct these errors. The error correction is corrected, for example, during down conversion when the frequency is lowered from the Larmor frequency band. At the same time as the down conversion, it is possible to perform IQ separation processing that separates MR data into a real part and an imaginary part, and it can be said that error correction is performed when IQ separation processing is performed.

In recent years, a magnetic resonance imaging device in which an A / D converter is built in a coil unit has been developed. Even in such a magnetic resonance imaging device, a technique for appropriately correcting the gain error and the phase error generated in the MR data as the characteristics of each hardware is required.

Japanese Unexamined Patent Publication No. 2011-193989 Japanese Unexamined Patent Publication No. 2014-50712

An object to be solved by the present invention is to appropriately correct MR data in magnetic resonance imaging using a coil unit having a built-in A / D converter.

The magnetic resonance imaging apparatus according to the embodiment includes a receiving circuit that receives a signal output from the coil unit and performs signal processing. The coil unit stores at least one RF coil element, at least one A / D converter that converts an analog signal output from the at least one RF coil element into a digital signal, and information on equipment characteristics. A unit is provided, and the digital signal and information on the equipment characteristics are associated and output. The receiving circuit corrects the digital signal output from the coil unit by using the information about the device characteristics associated with the digital signal.

FIG. 1 is a block diagram showing an example of the configuration of the magnetic resonance imaging apparatus according to the present embodiment. FIG. 2 is a diagram for explaining the configuration of the local RF coil unit. FIG. 3 is a diagram illustrating a gain correction table as correction information stored in the correction information storage unit. FIG. 4 is a diagram illustrating a phase correction table as correction information stored in the correction information storage unit. FIG. 5 is a diagram illustrating a frequency characteristic table as correction information stored in the correction information storage unit. FIG. 6 is a diagram for explaining the configuration of the receiving circuit. FIG. 7 is a diagram for explaining the flow of MR data / correction information in the magnetic resonance imaging apparatus and the correction processing of MR data using the correction information. FIG. 8 is a diagram for explaining a comparative example with the magnetic resonance imaging apparatus according to the embodiment.

Hereinafter, embodiments of the Magnetic Resonance Imaging (MRI) apparatus according to the present embodiment will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an example of the configuration of the magnetic resonance imaging device 1 according to the present embodiment. As shown in FIG. 1, the magnetic resonance imaging device 1 includes a static magnetic field magnet 101, a gradient magnetic field coil 102, a gradient magnetic field power supply 103, a sleeper 104, a sleeper control circuit 105, a whole body RF coil unit 106, a transmission circuit 107, and a local RF. It includes a coil unit C1, a receiving circuit 109, a sequence control circuit 110, a computer system 120, and a high frequency amplification device 100. The magnetic resonance imaging device 1 does not include a subject P such as a human body.

The static magnetic field magnet 101 is a magnet formed in a hollow cylindrical shape, and generates a uniform static magnetic field in the internal space. The cylindrical shape includes a cylinder having an elliptical cross section orthogonal to the axis of the cylinder.

The gradient magnetic field coil 102 is a coil formed in a hollow cylindrical shape and generates a gradient magnetic field.

The gradient magnetic field power supply 103 supplies a current to the gradient magnetic field coil 102.

The bed 104 has a top plate 104a on which the subject P is placed and a connector port 104b for connecting the whole body RF coil unit 106. Under the control of the bed control circuit 105, the bed 104 inserts the top plate 104a into the cavity of the gradient magnetic field coil 102 with the subject P placed therein. A local RF coil unit C1 is connected to the connector port 104b.

The sleeper control circuit 105 is a processor that drives the sleeper 104 to move the top plate 104a in the longitudinal direction and the vertical direction under the control of the computer system 120.

The whole body RF coil unit 106 is located inside the gradient magnetic field coil 102 and has at least one RF coil element. The whole body RF coil unit 106 receives a high frequency pulse for transmission from the transmission circuit 107, and generates a high frequency magnetic field from at least one RF coil element. Further, the whole body RF coil unit 106 receives a magnetic resonance signal (hereinafter referred to as MR signal) emitted from the subject P by being excited by a high frequency magnetic field.

The transmission circuit 107 supplies the whole-body RF coil unit 106 with RF pulses corresponding to the Larmor frequency determined by the type of the target nucleus and the strength of the magnetic field.

The local RF coil unit C1 has a shape and size corresponding to the imaging site of the subject P, and is installed at a position corresponding to the imaging site. The local RF coil unit C1 receives the MR signal emitted from the subject P by being excited by a high frequency magnetic field. The local RF coil unit C1 is connected to the connector port 104b of the bed 104 via a cable, and outputs the received MR signal to the receiving circuit 109 via the connector port 104b.

In FIG. 1, a case where the local RF coil unit C1 is a body coil unit installed on the chest or abdomen of the subject P is illustrated. However, there are various types of the local RF coil unit C1, such as a head coil unit installed on the head of the subject P and a spine coil unit installed on the back side of the subject P. The local RF coil unit C1 is not limited to reception only, and can be used for both transmission and reception or for transmission only.

Further, in FIG. 1, a magnetic resonance imaging device 1 including one local RF coil unit C1 is illustrated. However, not limited to this example, the magnetic resonance imaging apparatus 1 can have as many local RF coil units as the number of connector ports 104b. Therefore, for example, when the number of connector ports 104b is eight, the magnetic resonance imaging apparatus 1 can be provided with a maximum of eight (eight types) local RF coil units. The number and type of local RF coil units to be arranged in actual imaging is determined according to the purpose of imaging.

FIG. 2 is a diagram for explaining the configuration of the local RF coil unit C1. The configuration of the local RF coil unit C1 will be described in more detail with reference to FIG.

As shown in FIG. 2, the local RF coil unit C1 includes at least one RF coil element and at least one A / D converter that converts an analog signal output from at least one RF coil element into a digital signal. It is provided with a storage unit that stores information related to device characteristics, and outputs a digital signal in association with information related to device characteristics. That is, the local RF coil unit C1 is, for example, 16 RF coil elements 201 to 216, gain blocks 301 to 216 provided for each RF coil element, and an A / D converter 401 provided for each RF coil element. ~ 416, a coil unit interface circuit 5, and a correction information storage unit 6 are provided.

The RF coil elements 2001 to 216 have a shape and size corresponding to the imaging site, and receive the MR signal emitted from the subject P by being excited by a high frequency magnetic field.

The gain blocks 301 to 216 have a variable amplifier (variable gain amplifier) that amplifies the MR signal received by the RF coil elements 201 to 216. By amplifying the MR signal in the previous stage of the A / D converters 401 to 416 described later, the influence of the quantization error in the A / D conversion is suppressed.

The A / D converters 401 to 416 convert the MR signal as an analog signal output by the gain blocks 301 to 416 into MR data as a digital signal.

The coil unit interface circuit 5 is connected to the connector port 104b of the sleeper 104, and sends MR data to the main body of the magnetic resonance imaging device 1 by, for example, 16 independent signal wirings (16 lines). In the present embodiment, the number of RF coil elements 201 to 216 is referred to as the number of channels, and the signal transmission paths corresponding to each of the RF coil elements 201 to 216 are referred to as channels 1 to 16. The signal wiring is also called a line.

The correction information storage unit 6 is a memory that stores information related to device characteristics as correction information used for correcting MR data. Here, the information regarding the equipment characteristics is, for example, characteristics caused by the specifications or manufacturing errors of the hardware equipment existing in the signal transmission path from the RF coil elements 201 to 216 to the receiving circuit 109. The information regarding the equipment characteristics is, for example, the amount of deviation between the set gain value and the actual gain value in each of the gain blocks 301 to 316. Further, for example, it is the amount of phase shift of the MR signal that occurs when passing through the gain block, which is determined for each gain value set in each of the gain blocks 301 to 316. Further, for example, when the correction information storage unit 6 separately provides a filter after the gain blocks 301 to 316, the correction information storage unit 6 may retain the frequency characteristics of the filter as information regarding the equipment characteristics. The frequency characteristic represents the difference in insertion loss depending on the input frequency.

FIG. 3 is a diagram illustrating a gain correction table Ta as information regarding device characteristics (hereinafter, also referred to as “correction information”) stored in the correction information storage unit 6. FIG. 4 is a diagram illustrating a phase correction table Tb as correction information stored in the correction information storage unit 6. FIG. 5 is a diagram illustrating a frequency characteristic table Tc as correction information stored in the correction information storage unit 6. These correction information are measured for each local RF coil unit C1, for example, before shipment from the factory, or newly measured at the time of maintenance, and are stored in advance in the correction information storage unit 6.

In the gain correction table Ta shown in FIG. 3, the amount of deviation between the set gain value and the actual gain value in each of the gain blocks 301 to 316 is registered in advance for each set gain value. ing. With reference to the gain correction table Ta, for example, when the gain value is set to "0 dB", it can be seen that the actual gain value of the gain block 301 corresponding to the channel 1 (CH1) is "+0.3 dB". Further, for example, when the gain value is set to "1 dB", it can be seen that the actual gain value of the gain block 302 corresponding to the channel 2 (CH2) is "−0.3 dB".

In the phase correction table Tb shown in FIG. 4, the amount of phase shift of the MR signal determined for each set gain value generated when passing through the gain blocks in each of the gain blocks 301 to 316 is set as the gain value. Each is registered in advance. With reference to the phase correction table Tb, for example, when the gain value is set to "0 dB", it can be seen that the phase of the MR signal shifts by "+3 degrees" in channel 1 (CH1). Further, for example, when the gain value is set to "1 dB", it can be seen that the phase of the MR signal is shifted by "-2 degrees" in the channel 2 (CH2).

In the frequency characteristic table Tc shown in FIG. 5, the frequency characteristics of the bandpass filter provided after the gain blocks 301 to 316 are registered in advance. With reference to the frequency characteristic table Tc, for example, when the center frequency of the MR signal is set to "123 MHz", it can be seen that the gain of the bandpass filter corresponding to channel 1 (CH1) is deviated by "0.5 dB". Further, for example, when the center frequency of the MR signal is set to "123.001 MHz", it can be seen that the gain of the bandpass filter corresponding to the channel 2 (CH2) is deviated by "0.2 dB".

Returning to FIG. 1, the receiving circuit 109 executes predetermined signal processing such as down conversion processing and detection processing on the MR data output from the local RF coil unit C1. Further, the receiving circuit 109 corrects MR data as a digital signal output from the local RF coil unit C1 by using the information regarding the equipment characteristics.

FIG. 6 is a diagram for explaining the configuration of the receiving circuit 109. As shown in FIG. 6, the receiving circuit 109 includes a digital signal matrix 109a and correction processing units 109b01 to 109b32.

The digital signal matrix 109a selects necessary 32 lines of MR data from 128 lines of MR data output from the local RF coil unit C1 via the connector port 104b of the sleeper top plate 104a. For example, the digital signal matrix 109a selects a necessary line from the MR signals output by a plurality of RF coil elements, synthesizes MR data as necessary, and outputs MR data for 32 lines. In this embodiment, a case where a line and a channel have a one-to-one correspondence is taken as an example. Therefore, the digital signal matrix 109a thins out 128 channels of MR data output from the local RF coil unit C1 to 32 channels of MR data.

The correction processing units 109b01 to 109b32 receive MR data and correction information for the corresponding channels from the digital signal matrix 109a, respectively. The correction processing units 109b01 to 109b32 use the received correction information to correct the MR data of the corresponding channel.

Specifically, the correction processing units 109b01 to 109b32 have Direct Digital Synthesizer (DDS) 109b01-1 to 109b32-1, and detectors 109b01-2 to 109b32-2, respectively.

The DDS109b01-1 to 109b32-1 play a basic role, for example, to generate a digital signal based on a clock and a phase value synchronized with the clock when the RF pulse of the Ramora frequency is generated. The generated digital signal is used as a local signal when performing the down conversion process. Further, for example, quadrature detection is performed by separating the generated digital signal into two digital signals having quadrature phases and multiplying the MR data sent from the local RF coil unit C1 via the digital signal matrix 109a. I do. The process of orthogonal detection is also called IQ (In-phase Quadrature) separation. As a result of orthogonal detection, MR data is separated into a real part and an imaginary part.

The DDS109b01-1 to 109b32-1 change the generated digital signal by using the correction information sent from the local RF coil unit C1. For example, when a phase shift amount is acquired as correction information, the DDS109b01-1 to 109b32-1 generates a digital signal by using a phase value that corrects the phase shift amount. Further, for example, when the amount of gain deviation is acquired as correction information, DDS109b01-1 to 109b32-1 changes the amplitude of the output digital signal. As the amplitude of the digital signal changes, the output of the result of multiplication by the detectors 109b01-2 to 109b32-2, which will be described later, changes, and as a result, the amount of gain deviation is corrected.

The detectors 109b01-2 to 109b32-2 multiply the MR data output from the digital signal matrix 109a and the digital signal generated by the DDS109b01-1 to 109b32-1 for the corresponding channels, and the computer interface circuit 121 Send to.

In addition to the down conversion processing, the detection processing, and the frequency filter processing, the receiving circuit 109 can perform arbitrary signal processing as needed.

Returning to FIG. 1, the sequence control circuit 110 controls the high-frequency amplification device 100, the gradient magnetic field power supply 103, the transmission circuit 107, and the reception circuit 109 based on the sequence information transmitted from the computer system 120. To take an image of. The sequence control circuit 110 may be realized by a processor or may be realized by a mixture of software and hardware.

The sequence information is information that defines a pulse sequence executed in the inspection by the magnetic resonance imaging apparatus 1. The sequence information includes the strength of the current supplied by the gradient magnetic field power supply 103 to the gradient magnetic field coil 102, the timing of supplying the current, and the RF transmitted by the transmission circuit 107 to the whole body RF coil unit 106 or the local RF coil units C1 to C8. The strength of the pulse, the timing of applying the RF pulse, the timing of the receiving circuit 109 detecting the MR signal, and the like are defined.

The sequence information includes imaging conditions specified by the operator, such as TR (repetition time), TE (echo time), number of slices, slice thickness, and FOV (field of view). Etc., it is assumed that the computer system 120 generates information based on a large number of imaging parameters.

The high frequency amplification device 100 is connected to the computer system 120, the sequence control circuit 110, the transmission circuit 107, and the like, and generates a high frequency signal based on the instruction received from the computer system 120 or the sequence information received from the sequence control circuit 110.

The computer system 120 performs overall control of the magnetic resonance imaging device 1, data acquisition, image reconstruction, and the like. More specifically, the computer system 120 controls the sequence control circuit 110, the high frequency amplification device 100, and the bed control circuit 105. The computer system 120 includes a computer interface circuit 121, a storage circuit 122, a processing circuit 123, an input interface 124, and a display 125. The computer system 120 is an example of the control system of the magnetic resonance imaging device 1 in the present embodiment.

The computer interface circuit 121 transmits sequence information to the sequence control circuit 110, and receives MR data from the sequence control circuit 110. Further, when the computer interface circuit 121 receives the MR data, the computer interface circuit 121 stores the received MR data in the storage circuit 122.

The storage circuit 122 stores various programs. The storage circuit 122 is realized by, for example, a RAM (Random Access Memory), a semiconductor memory element such as a flash memory, a hard disk, an optical disk, or the like. The storage circuit 122 is also used as a non-transient storage medium by hardware.

The input interface 124 receives various instructions and information inputs from operators such as doctors and radiological technologists. The input interface 124 is realized by, for example, a trackball, a switch button, a mouse, a keyboard, or the like. The input interface 124 is connected to the processing circuit 123, converts the input operation received from the operator into an electric signal, and outputs the input operation to the processing circuit 123.

The display 125 displays various GUI (Graphical User Interface), MR (Magnetic Resonance) images, and the like under the control of the processing circuit 123.

The processing circuit 123 controls the entire magnetic resonance imaging device 1. Specifically, the processing circuit 123 generates sequence information based on the imaging conditions input from the operator via the input interface 124, and controls imaging by transmitting the generated sequence information to the sequence control circuit 110. To do. Further, the processing circuit 123 arranges the MR data sent from the sequence control circuit 110 as a result of imaging according to the phase encoding amount and the frequency encoding amount given by the gradient magnetic field described above. The arranged MR data is referred to as k-space data, and the k-space data is subjected to reconstruction processing such as Fourier transform to generate an MR image. The processing circuit 123 controls the display 125 to display the generated MR image.

Each function realized by the processing circuit 123 is realized by the processing circuit 123 as a CPU executing a control program. However, the present invention is not limited to this, and a part or all of each function realized by the processing circuit 123 is a dedicated hardware designed to execute each of the same functions, for example, an ASIC (Application Specific Integrated Circuit). , DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array) and other semiconductor integrated circuits, and conventional circuit modules may be used.

(Flow of MR data / correction information and correction processing)
Next, the flow of MR data / correction information of the magnetic resonance imaging apparatus 1 according to the present embodiment and the correction processing of MR data using the correction information will be described. In the following, the case of correcting the gain shift and the phase shift for the MR data of each channel will be taken as an example. However, which item to correct, the gain shift or the phase shift, can be selected by setting.

FIG. 7 is a diagram for explaining the flow of MR data / correction information in the magnetic resonance imaging apparatus 1 and the correction processing of MR data using the correction information.

In FIG. 7, for the sake of specific explanation, a case where local RF coil units C1 to C8 are connected to each of the eight connector ports 104b of the bed 104 is illustrated. However, it is not always necessary that the local RF coil unit is connected to all the connector ports. Further, if one local RF coil unit has a plurality of coil unit interface circuits, one local RF coil unit may be connected to a plurality of connector ports. Further, although the number of RF coil elements 201 to 216 of the local RF coil unit C1 is 16, the number of RF coil elements of each local RF coil unit may be any number.

As shown in FIG. 7, for example, the MR signal received by each of the RF coil elements 201 to 216 of the local RF coil unit C1 is amplified by the gain blocks 301 to 216 in each channel. The MR signals received by each of the RF coil elements 2001 to 216 are MR signals corresponding to channels 1 to 16. The MR signal amplified by the gain blocks 301 to 316 is converted into MR data as a digital signal by the A / D converters 401 to 416 in each channel. The MR data for 16 channels corresponding to channels 1 to 16 are received by 16 lines via the coil unit interface circuit 5 and the connector port 104b together with the correction information stored in the correction information storage unit 6, respectively. It is sent to 109.

For the other local RF coil units C2 to C8, MR data and correction information are sent to the receiving circuit 109 by the same processing. As a result, a total of 128 channels of MR data and correction information are sent to the receiving circuit 109.

The MR data and correction information for 128 channels are thinned out to the MR data and correction information for 32 channels in the digital signal matrix 109a. The MR data and correction information for 32 channels are sent to the correction processing units 109b01 to 109b32. That is, the MR data and correction information for 32 channels are sent from the local RF coil unit C1 to the correction processing units 109b01 to 109b32 by the same route.

The MR data for each channel is down-converted by the correction processing units 109b01 to 109b32, and at least one of the gain shift and the phase shift is corrected by using the correction information. The correction information means a gain correction table Ta, a phase correction table Tb, and a frequency characteristic table Tc.

For example, the gain value of the gain block 301 is set to 0 dB, the center frequency of the filter provided after the gain block 301 is set to 123 MHz, the MR data of the channel 1 and the correction information are sent to the correction processing unit 109b01, and the channel concerned. It is assumed that gain correction and phase correction are performed on the MR data of 1. In such a case, the amount of deviation of the gain of the channel 1 in the gain block 301 when the gain value is set to “0 dB” as shown in FIG. 3 is “0.3 dB”. Further, as shown in FIG. 4, the amount of phase shift of the channel 1 in the gain block 301 when the gain value is set to “0 dB” is “+3 degrees”. Further, as shown in FIG. 5, the amount of gain deviation of channel 1 in the filter provided after the gain block 301 is “0.5 dB”. Therefore, a digital signal corresponding to these three correction amounts is generated in the DDS109b01-1. The processing procedure is the same for other channels.

(effect)
As described above, the magnetic resonance imaging apparatus 1 according to the present embodiment includes a receiving circuit 109 that receives a signal output from the local RF coil unit C1 and performs signal processing. The local RF coil unit C1 includes at least one RF coil element 201-216 and at least one A / D converter 401-that converts an analog signal output from at least one RF coil element 201-216 into a digital signal. A 416 and a correction information storage unit 6 for storing information related to device characteristics as correction information are provided, and a digital signal and information related to device characteristics are associated and output. The receiving circuit 109 corrects the digital signal output from the local RF coil unit C1 by using the information regarding the equipment characteristics.

That is, for example, the gain correction table Ta, the phase correction table Tb, and the frequency characteristic table Tc are used as correction information for correcting the gain and phase shift, which are characteristics caused by specifications or manufacturing errors, for example, before shipment from the factory. It is stored in the correction information storage unit 6. In the magnetic resonance imaging device 1, the correction information unique to the local RF coil unit C1 connected to the connector port 104b of the sleeper 104 is MR as a digital signal output from the local RF coil unit C1 at the time of imaging, for example. It is sent out to the receiving circuit 109 in association with the data. The receiving circuit 109 can execute at least one of gain correction and phase correction on the MR data by using the correction information received from the local RF coil unit C1.

Therefore, since it is not necessary to store the correction information for each local RF coil unit in the magnetic resonance imaging apparatus main body in advance, the phase and gain characteristics of the digital signal output by the connected local RF coil unit have changed. Even so, it is not necessary to modify the receiving circuit 109 of the magnetic resonance imaging device 1.

Further, the correction information associated with the MR data is sent to the receiving circuit 109 by the same route as the MR data. Therefore, the correction information can be sent to the receiving circuit 109 regardless of the selected route.

(Comparison example)
FIG. 8 is a diagram for explaining a comparative example with the magnetic resonance imaging device 1 according to the present embodiment. With reference to FIG. 8, a correction process using correction information in a magnetic resonance imaging apparatus as a comparative example will be described.

In the magnetic resonance imaging apparatus as a comparative example shown in FIG. 8, a correction information storage unit 6 for storing correction information is provided in the receiving circuit 109 ′ of the main body of the magnetic resonance imaging apparatus. Further, the local RF coil units C1'to C8' do not have a correction information storage unit 6 for storing correction information. In the case of such a configuration, the correction information storage unit 6 needs to store the correction information of all types of local RF coil units C1'to C8' connected to the connector port 104b, for example, before shipment from the factory. .. However, the correction information of the local RF coil units C1'to C8' is unique information of the coil unit, and is information about characteristics caused by, for example, specifications or manufacturing errors. Therefore, it is practically difficult to store the correction information of all the local RF coil units that may be connected to the magnetic resonance imaging apparatus main body in the correction information storage unit 6 in advance. Further, when a new local RF coil unit is connected to the connector port 104b, it is troublesome and inefficient to store the correction information regarding the local RF coil unit in the correction information storage unit 6.

In contrast to the above comparative example, the magnetic resonance imaging apparatus 1 according to the present embodiment has a correction information storage unit 6 for storing correction information on the local RF coil unit side. Then, the correction information peculiar to the local RF coil unit C1 connected to the connector port 104b of the sleeper 104 is received in association with the MR data as a digital signal output from the local RF coil unit C1 at the time of imaging, for example. It is sent to the circuit 109. Therefore, it is not necessary to store the correction information of all types of local RF coil units connected to the connector port 104b in advance on the magnetic resonance imaging apparatus main body side. Further, even when a new local RF coil unit is connected to the connector port 104b, it is also necessary to store the correction information regarding the local RF coil unit in the correction information storage unit 6 on the magnetic resonance imaging apparatus main body side. Absent.

(Modification example 1)
In the above embodiment, 16 lines as transmission paths drawn from the local RF coil unit C1 and connected to the connector port 104b of the sleeper 104 are the 16 RF coil elements of the local RF coil unit C1. The case of one-to-one correspondence has been described as an example. In such an example, one line corresponds to one channel.

However, for example, if the local RF coil unit has 64 RF coil elements, the number of lines that the connector port 104b can accept will be exceeded. In such a case, 16 lines are obtained by multiplexing the MR data for 64 channels acquired by using the 64 RF coil elements by frequency modulation or adding signals for a plurality of channels. Aggregate to.

For example, it is assumed that the MR data for 64 channels acquired by using 64 RF coil elements is multiplexed by frequency modulation in units of 4 channels. In such a case, the MR data for 64 channels processed by the gain block and A / D conversion is frequency-modulated by a modulator provided in the local RF coil unit, and is multiplexed in units of 4 channels, for example, 16 Generate synthetic data and assign it to 16 lines. The receiving circuit 109 demodulates the composite data for 16 lines received from the local RF coil unit and separates it into MR data corresponding to 64 channels. The receiving circuit 109 executes correction processing using the correction information on the MR data corresponding to each separated channel.

Further, for example, it is assumed that the MR data for 64 channels acquired by using 64 RF coil elements is combined by addition in units of 4 channels. In such a case, the adder provided in the local RF coil unit adds the MR data before amplification by the gain block, for example, in units of 4 channels to generate 16 composite data, each of which has 16 lines. Assign to. Then, the 16 composite data are processed by the gain blocks 301 to 316 and the A / D converters 401 to 416, respectively, and then output to the receiving circuit 109 together with the correction information as 16 MR data. The receiving circuit 109 executes correction processing using the correction information on the composite data for 16 lines received from the local RF coil unit.

(Modification 2)
In the above embodiment, a case where the correction information is sent to the receiving circuit 109 at the same timing as the MR data acquired at the time of imaging is illustrated. However, the timing at which the receiving circuit 109 side acquires the correction information is not limited to this example.

For example, the local RF coil unit C1 may be configured to send correction information to the receiving circuit 109 before imaging at the timing when it is connected to the connector port 104b.

Further, the correction information may be managed on the magnetic resonance imaging apparatus 1 main body side in association with the information (coil ID) for identifying the local RF coil unit C1. In such a configuration, if the correction information used in the past includes the correction information that matches the coil ID of the currently connected local RF coil unit C1, the correction information from the local RF coil unit C1 is used. The reception may be omitted and the correction information on the main body side of the magnetic resonance imaging device 1 may be used.

In addition, information on the created date and time is attached to the correction information, and the creation date and time of the correction information on the magnetic resonance imaging device 1 main body side is the correction information stored in the correction information storage unit 6 of the local RF coil unit C1. If it is older than the creation date and time, new correction information may be received from the local RF coil unit C1 and the correction information may be updated.

(Modification 3)
In the above embodiment, the case where the correction information is the gain correction table Ta, the phase correction table Tb, and the frequency characteristic table Tc has been illustrated. However, the correction information stored in the correction information storage unit 6 of the local RF coil unit C1 is not limited to the above example. For example, when the local RF coil unit C1 has at least one log amplifier, a table in which correction values for returning the non-linearity generated in each log amplifier to linearity may be defined may be included.

(Modification example 4)
In the above embodiment, a case where the transfer of MR data and correction information from the local RF coil unit C1 to the receiving circuit 109 is realized by wire is illustrated. However, the present invention is not limited to this, and the transfer of MR data and correction information from the local RF coil unit C1 to the receiving circuit 109 may be realized wirelessly.

The word "processor" used in the description in the present embodiment means, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an integrated circuit for a specific application (ASIC), or a programmable logic. It means a circuit such as a device (for example, a Simple Programmable Logic Device (SPLD), a Complex Programmable Logic Device (CPLD), and a Field Programmable Gate Array (FPGA)). .. The processor realizes the function by reading and executing the program stored in the storage circuit. Instead of storing the program in the storage circuit, the program may be directly embedded in the circuit of the processor. In this case, the processor realizes the function by reading and executing the program embedded in the circuit. It should be noted that each processor of the present embodiment is not limited to the case where each processor is configured as a single circuit, and a plurality of independent circuits may be combined to form one processor to realize its function. Good.

According to at least one embodiment described above, MR data can be appropriately corrected in magnetic resonance imaging using a coil unit incorporating an A / D converter.

In addition, although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

1 Magnetic resonance imaging device 5 Coil unit interface circuit 6 Correction information storage unit 100 High frequency amplification device 101 Static magnetic field magnet 102 Tilt magnetic field coil 103 Tilt magnetic field power supply 104 Sleeper 104a Sleeper top plate 104b Connector port 105 Sleeper control circuit 106 Whole body RF coil unit 107 Transmission circuit 109 Reception circuit 109a Digital signal matrix 109b01 to 109b32 Correction processing unit 109b01-1 to 109b32-1 DDS
109b01-2 to 109b32-2 Detector 110 Sequence control circuit 120 Computer system 201-216 RF coil element 301-316 Gain block 401-416 A / D converter C1-C8 Local RF coil unit

Claims (9)

A magnetic resonance imaging apparatus including a receiving circuit that receives a signal output from a coil unit and performs signal processing.
The coil unit stores at least one RF coil element, at least one A / D converter that converts an analog signal output from the at least one RF coil element into a digital signal, and information on equipment characteristics. A unit is provided, and the digital signal is associated with information about the device characteristics and output.
The receiving circuit corrects the digital signal output from the coil unit by using the information about the device characteristics associated with the digital signal.
Magnetic resonance imaging device. The magnetic resonance imaging apparatus according to claim 1, wherein the storage unit stores information on characteristics due to specifications or manufacturing errors as information on the equipment characteristics. The magnetic resonance imaging apparatus according to claim 1, wherein the storage unit stores a correction value for at least one of a gain value and a phase shift as information regarding the equipment characteristics. The magnetic resonance imaging apparatus according to any one of claims 1 to 3, wherein the receiving circuit uses a direct digital synthesizer to correct the digital signal. The magnetic resonance imaging apparatus according to any one of claims 1 to 4, wherein the receiving circuit receives the digital signal and information on the equipment characteristics via the same path. The coil unit further comprises at least one variable gain amplifier.
The storage unit stores information on the equipment characteristics corresponding to each of the at least one variable gain amplifier.
The magnetic resonance imaging apparatus according to any one of claims 1 to 5. The coil unit further comprises at least one log amplifier.
The storage unit stores information on the device characteristics corresponding to each of the at least one log amplifier.
The magnetic resonance imaging apparatus according to any one of claims 1 to 5. The magnetic resonance imaging device according to any one of claims 1 to 7, wherein the coil unit transmits the digital signal and information on the equipment characteristics to the receiving circuit wirelessly or by wire. A magnetic resonance imaging apparatus including a receiving circuit that receives a signal output from a coil unit and performs signal processing.
The coil unit includes at least one RF coil element, at least one A / D converter that converts an analog signal output from the at least one RF coil element into a digital signal, and at least one of a gain value and a phase. A storage unit for storing information related to one correction is provided, and the digital signal and the information related to the correction are associated and output to the receiving circuit.
The receiving circuit corrects the digital signal output from the coil unit by using the information about the correction associated with the digital signal.
Magnetic resonance imaging device.

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