CN109001658B - Transmitter, receiver, magnetic resonance apparatus, and radio frequency signal generation method - Google Patents
Transmitter, receiver, magnetic resonance apparatus, and radio frequency signal generation method Download PDFInfo
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- CN109001658B CN109001658B CN201811072888.4A CN201811072888A CN109001658B CN 109001658 B CN109001658 B CN 109001658B CN 201811072888 A CN201811072888 A CN 201811072888A CN 109001658 B CN109001658 B CN 109001658B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
- G01R33/36—Electrical details, e.g. matching or coupling of the coil to the receiver
- G01R33/3607—RF waveform generators, e.g. frequency generators, amplitude-, frequency- or phase modulators or shifters, pulse programmers, digital to analog converters for the RF signal, means for filtering or attenuating of the RF signal
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
- G01R33/36—Electrical details, e.g. matching or coupling of the coil to the receiver
- G01R33/3621—NMR receivers or demodulators, e.g. preamplifiers, means for frequency modulation of the MR signal using a digital down converter, means for analog to digital conversion [ADC] or for filtering or processing of the MR signal such as bandpass filtering, resampling, decimation or interpolation
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Abstract
The application provides a transmitter, a receiver, a magnetic resonance device and a radio frequency signal generation method: a frequency control word generating unit generates a frequency control word; the frequency control word sending unit sends the frequency control word to a frequency control word receiving unit in the receiver; the synchronous trigger unit generates a synchronous signal, and sends the synchronous signal to a synchronous induction unit in the receiver, so that a DDC unit in the receiver generates a digital radio frequency signal according to a frequency control word under the trigger of the synchronous signal; the DDS unit generates a digital radio frequency signal according to the frequency control word under the triggering of the synchronous signal; the DAC unit converts the digital radio frequency signals into analog radio frequency signals; the DAC unit receives the digital radio frequency signal at a first moment, the synchronous induction unit receives the synchronous signal at a second moment, the DDC unit receives the frequency control word at a third moment, and the first moment is the same as the second moment and is later than the third moment. The method and the device can ensure the phase coherence of the transmitter and the receiver.
Description
Technical Field
The present application relates to the field of medical device technology, and in particular, to a transmitter, a receiver, a magnetic resonance device, and a radio frequency signal generation method.
Background
Magnetic Resonance Imaging (MRI) is one of the main Imaging modalities in modern medical Imaging. The basic working principle of magnetic resonance imaging is to use the magnetic resonance phenomenon, excite the hydrogen protons in the examined body by using radio frequency signals, perform position encoding by using a gradient field, subsequently receive the magnetic resonance signals with position information, and finally reconstruct a magnetic resonance image by using Fourier transform.
Since the system needs to frequently weight the compensation factors for the gradient coil eddy currents to the main magnetic field frequency in order to compensate for the main magnetic field after the magnetic field (B0 magnetic field) induced by the eddy currents of the gradient coil in the direction X, Y, Z shifts from the averaged field, this can result in frequent switching of the transmitter frequency. In the currently used magnetic resonance apparatus, a transmitter usually employs a Direct Digital Synthesis (DDS) technique, and a receiver usually employs a DDC (DDC) technique. The DDS unit in the transmitter and the DDC unit in the receiver both have an NCO (Numerically Controlled Oscillator), and the frequency switching between the transmitter and the receiver can be realized quickly by respectively controlling the frequency control words of the NCO.
The magnetic resonance signals are complex signals that include not only amplitude information but also phase information. The phase of the resulting magnetic resonance signal at the receiver is determined by both the transmitter phase and the receiver phase. For effective signal accumulation and phase encoding of imaging, it is necessary to ensure phase coherence between the transmitter and the receiver during execution of the magnetic resonance sequence, i.e. the transmitter and the receiver are required to maintain a fixed phase difference, which requires that the frequency of the analog radio frequency signal output by the transmitter for exciting the subject be switched synchronously with the frequency of the digital radio frequency signal generated by the receiver for magnetic resonance imaging.
Disclosure of Invention
In view of the above, the present application provides a transmitter, a receiver, a magnetic resonance apparatus and a radio frequency signal generation method to ensure phase coherence of the transmitter and the receiver.
Specifically, the method is realized through the following technical scheme:
in a first aspect, the present application provides a transmitter comprising:
a frequency control word generating unit for generating a frequency control word for controlling generation of the radio frequency signal;
a frequency control word transmitting unit for transmitting the frequency control word to a frequency control word receiving unit in a receiver;
the synchronous trigger unit is used for generating a synchronous signal and sending the synchronous signal to a synchronous induction unit in the receiver so that a digital down-conversion DDC unit in the receiver generates a digital radio-frequency signal according to the frequency control word under the trigger of the synchronous signal;
the direct digital frequency synthesis DDS unit is used for generating a digital radio frequency signal according to the frequency control word under the triggering of the synchronous signal;
the digital-to-analog conversion DAC unit is used for converting the digital radio frequency signal into an analog radio frequency signal;
the time when the DAC unit receives the digital radio frequency signal is a first time, the time when the synchronous sensing unit receives the synchronous signal is a second time, the time when the DDC unit receives the frequency control word is a third time, the second time is the same as the first time, and the third time is earlier than the first time.
In a second aspect, the present application provides a receiver comprising:
the synchronous induction unit is used for receiving a synchronous signal sent by a synchronous trigger unit in a transmitter, and the synchronous signal is generated by the synchronous trigger unit;
a frequency control word receiving unit, configured to receive a frequency control word sent by a frequency control word sending unit in the transmitter, where the frequency control word is generated by the frequency control word sending unit;
the DDC unit is used for generating a digital radio frequency signal according to the frequency control word under the triggering of the synchronous signal;
the time when the DAC unit in the transmitter receives the digital radio frequency signal is a first time, the time when the synchronous sensing unit receives the synchronous signal is a second time, the time when the DDC unit receives the frequency control word is a third time, the second time is the same as the first time, and the third time is earlier than the first time.
In a third aspect, the present application provides a magnetic resonance apparatus comprising: the transmitter described above, and the receiver described above.
In a fourth aspect, the present application provides a radio frequency signal generating method, which is applied to a transmitter, and includes:
generating a frequency control word for controlling generation of the radio frequency signal;
transmitting the frequency control word to a receiver;
generating a synchronous signal, and sending the synchronous signal to the receiver, so that the receiver generates a digital radio frequency signal according to the frequency control word under the triggering of the synchronous signal;
under the trigger of the synchronous signal, generating a digital radio frequency signal according to the frequency control word;
converting the digital radio frequency signal into an analog radio frequency signal;
the moment when the transmitter starts to convert the digital radio frequency signal into the analog radio frequency signal is a first moment, the moment when the receiver receives the synchronous signal is a second moment, the moment when the receiver receives the frequency control word is a third moment, the second moment is the same as the first moment, and the third moment is earlier than the first moment.
In a fifth aspect, the present application provides a radio frequency signal generating method, which is applied to a receiver, and includes:
receiving main magnetic field frequency parameters sent by an upper computer, and generating first frequency control words according to the main magnetic field frequency parameters;
updating a B0 compensation value according to the gradient coil eddy current at preset intervals, and generating a second frequency control word according to the updated B0 compensation value and a preset weighting coefficient;
the generating a frequency control word that controls the generation of the radio frequency signal includes:
and adding the first frequency control word and the second frequency control word, and determining the frequency control word obtained by adding as a frequency control word for controlling the generation of the radio frequency signal.
As can be seen from the above embodiments, since the first time is the same as the second time, it can be ensured that the transmitter outputs the analog rf signal for exciting the subject and keeps synchronizing with the digital rf signal generated by the receiver for performing the magnetic resonance imaging; since the third time is earlier than the first time, it is ensured that the analog rf signal output by the transmitter and the digital rf signal generated by the receiver originate from the same frequency control word. Therefore, when the frequency control word for controlling the generation of the radio frequency signal is updated, the synchronous switching of the frequency of the analog radio frequency signal output by the transmitter and the frequency of the digital radio frequency signal generated by the receiver can be ensured, so that the transmitter and the receiver keep a fixed phase difference, and the phase coherence of the transmitter and the receiver is ensured.
Drawings
FIG. 1 is a schematic diagram of a transmitter shown in an exemplary embodiment of the present application;
FIG. 2 is a schematic diagram of a receiver shown in an exemplary embodiment of the present application;
figure 3 is a schematic diagram of a magnetic resonance apparatus shown in an exemplary embodiment of the present application;
figure 4 is a schematic diagram of another magnetic resonance apparatus shown in an exemplary embodiment of the present application;
FIG. 5 is a flow chart illustrating a method of radio frequency signal generation according to an exemplary embodiment of the present application;
fig. 6 is a flow chart illustrating another method of generating a radio frequency signal according to an exemplary embodiment of the present application.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.
It is to be understood that although the terms first, second, third, etc. may be used herein to describe various information, such information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present application. The word "if" as used herein may be interpreted as "at … …" or "when … …" or "in response to a determination", depending on the context.
In the related art, in order to ensure phase coherence of the transmitter and the receiver, a rewinding (Rewind) technique may be generally used even if the transmitter and the receiver maintain a fixed phase difference.
For example, assume that the frequency of the receiver remains ω0Unchanged, further assume that during time period T1At the beginning the phase difference between transmitter and receiver is gamma0If the frequency of the transmitter is switched to (ω) at this time0+ δ ω), then at T1At the end, the phase difference between the transmitter and the receiver becomes (γ)0+δω×T1). If during the time period T2Initially, the transmitter frequency is switched to (ω)0δ ω'), then at T2At the end, the phase difference between the transmitter and the receiver becomes (γ)0+δω×T1-δω′×T2). In this case, if the condition is satisfied: delta omega x T1＝δω′×T2Then at T2At the end, the phase difference between the transmitter and the receiver can be recovered to be gamma0At this time T2I.e. the wrap-around delay.
Therefore, although the transmitter and the receiver can maintain a fixed phase difference to a certain extent by adopting the wrap-around technology, the wrap-around delay needs to be introduced, that is, the phase difference between the transmitter and the receiver can be recovered after the wrap-around delay, so that the echo time of a magnetic resonance sequence for scanning is prolonged, and the design complexity of the magnetic resonance sequence is increased.
In order to solve the above problems, the present application provides a transmitter, a receiver, a magnetic resonance apparatus, and a radio frequency signal generation method to ensure phase coherence between the transmitter and the receiver without increasing algorithm complexity.
Referring to fig. 1, a schematic diagram of a transmitter according to an exemplary embodiment of the present application is shown; referring to fig. 2, a schematic diagram of a receiver according to an exemplary embodiment of the present application is shown; referring to fig. 3, a schematic diagram of a magnetic resonance apparatus according to an exemplary embodiment of the present application is shown. As shown in fig. 3, the magnetic resonance apparatus 1 may include the transmitter 10 shown in fig. 1 and the receiver 20 shown in fig. 2.
The transmitter 10 may include: a frequency control word generating unit 101, a frequency control word transmitting unit 102, a synchronous trigger unit 103, a DDS unit 104, and a DAC (Digital to Analog Converter) unit 105; the receiver 20 may include: a synchronous sensing unit 201, a frequency control word receiving unit 202 and a DDC unit 203.
In the transmitter 10, the frequency control word generating unit 101 may be connected to the frequency control word transmitting unit 102, the synchronization triggering unit 103, and the DDS unit 104, respectively, and the DDS unit 104 may be connected to the synchronization triggering unit 103 and the DAC unit 105.
In the receiver 20, the DDC unit 203 may be connected to the synchronous sensing unit 201 and the frequency control word receiving unit 202, respectively.
In addition, the frequency control word sending unit 102 in the transmitter 10 may be connected to the frequency control word receiving unit 202 in the receiver 20, and the synchronization triggering unit 103 in the transmitter 10 may be connected to the synchronization sensing unit 201 in the receiver 20.
In the present embodiment, the frequency control word generation unit 101 may generate a frequency control word. Wherein the frequency control word may be used to control the generation of the radio frequency signal, which may be used to generate a magnetic resonance sequence for performing a magnetic resonance scan of the object.
On the one hand, frequency control word generation unit 101 may output the frequency control word to DDS unit 104 after generating the frequency control word.
On the other hand, after generating the frequency control word, frequency control word generating section 101 may output the frequency control word to frequency control word transmitting section 102, and frequency control word transmitting section 102 may transmit the frequency control word to frequency control word receiving section 202.
The synchronization triggering unit 103 may generate a synchronization signal. The synchronization signal may be a high-level enabled electrical signal.
On the one hand, after generating the synchronization signal, the synchronization trigger unit 103 may output the synchronization signal to the DDS unit 104.
On the other hand, after generating the synchronization signal, the synchronization triggering unit 103 may also transmit the synchronization signal to the synchronization sensing unit 201.
The DDS unit 104 is a unit that performs a direct digital frequency synthesis function, and may include an NCO. The DDS unit 104 can generate a digital rf signal according to the frequency control word output by the frequency control word generating unit 101 under the trigger of the synchronization signal output by the synchronization triggering unit 103. Specifically, a digital radio frequency signal may be generated by the NCO in DDS unit 104 from the frequency control word.
After generating the digital rf signal, the DDS unit 104 may output the digital rf signal to the DAC unit 105. The DAC unit 105 may convert the digital rf signal output by the DDS unit into an analog rf signal. The time when the DAC unit 105 receives the digital rf signal is a first time.
Subsequently, a magnetic resonance sequence may be generated using the analog radio frequency signal, so that a magnetic resonance scan of the object may be performed in accordance with the magnetic resonance sequence.
In this embodiment, the synchronization sensing unit 201 may receive the synchronization signal output by the synchronization triggering unit 103 when the first time is reached. Specifically, since the synchronization signal output by the synchronization triggering unit 103 may be a high-level enabled electrical signal, the synchronization sensing unit 201 may be considered to receive the synchronization signal when detecting the high-level enabled electrical signal. The time when the synchronization sensing unit 201 receives the synchronization signal is the second time.
Upon receiving the synchronization signal, the synchronization sensing unit 201 may output the synchronization signal to the DDC unit 203.
Since the frequency control word sending unit 102 can convert the frequency control word into serial data and bundle the serial data with other related data according to the data transmission protocol to be sent to the frequency control word receiving unit 202, the frequency control word receiving unit 202 needs to parse the data sent by the frequency control word sending unit 102 to obtain the frequency control word after receiving the data. After the frequency control word receiving unit 202 parses the frequency control word from the data, it can be regarded that the frequency control word receiving unit 202 completes receiving the frequency control word.
After the frequency control word receiving unit 202 finishes receiving the frequency control word output by the frequency control word generating unit 101, that is, after the frequency control word receiving unit 202 parses the frequency control word from the data transmitted by the frequency control word transmitting unit 102, the frequency control word may be output to the DDC unit 203. The time when the DDC unit 203 receives the frequency control word is the third time.
Subsequently, magnetic resonance imaging for the subject can be performed using the digital radio frequency signal and a magnetic resonance signal acquired after performing a magnetic resonance scan of the subject according to the magnetic resonance sequence.
In this embodiment, it should be noted that the second time when the synchronization sensing unit 201 receives the synchronization signal is the same as the first time when the DAC unit 105 receives the digital rf signal; and the third time instant when the frequency control word is received by the DDC unit 203 is earlier than the first time instant when the digital rf signal is received by the DAC unit 105.
As can be seen from the above embodiments, since the first time is the same as the second time, it can be ensured that the transmitter outputs the analog radio frequency signal for exciting the object to be examined, and the analog radio frequency signal is synchronized with the digital radio frequency signal generated by the receiver for performing the magnetic resonance imaging; since the third time is earlier than the first time, it is ensured that the analog rf signal output by the transmitter and the digital rf signal generated by the receiver originate from the same frequency control word. Therefore, when the frequency control word for controlling the generation of the radio frequency signal is updated, the synchronous switching of the frequency of the analog radio frequency signal output by the transmitter and the frequency of the digital radio frequency signal generated by the receiver can be ensured, so that the transmitter and the receiver keep a fixed phase difference, and the phase coherence of the transmitter and the receiver is ensured.
In practical applications, for convenience of implementation, after the frequency control word generation unit 101 finishes generating the frequency control word, the first timer may be started. The synchronization triggering unit 103 may generate the synchronization signal after the timing time of the first timer reaches the first delay time duration. Alternatively, after a computing chip such as a CPU (Central Processing Unit) in the transmitter reaches the first delay time period, the synchronization triggering Unit 103 may be controlled to generate the synchronization signal, which is not limited in this application.
Wherein, the first delay time length is equal to the time difference between the time when the frequency control word receiving unit 202 finishes receiving the frequency control word and the time when the frequency control word generating unit 101 finishes generating the frequency control word; alternatively, the first delay time may also be equal to the sum of the time difference and a preset fine tuning time, which may be set by the user according to the actual operating condition of the magnetic resonance apparatus. Thus, when the synchronization triggering unit 103 generates the synchronization signal, the frequency control word receiving unit 202 has completed receiving the frequency control word.
The synchronization trigger unit 103 may output the synchronization signal to the DDS unit 104 immediately after generating the synchronization signal.
In this case, after receiving the frequency control word output by the frequency control word generating unit 101, the DDS unit 104 does not generate a digital rf signal according to the frequency control word immediately, but generates a digital rf signal according to the frequency control word only under the trigger of the synchronization signal output by the synchronization triggering unit 103.
After the DDS unit 104 finishes generating the digital rf signal, a second timer may be started. The synchronization triggering unit 103 may send the previously generated synchronization signal to the synchronization sensing unit 201 after the timing time of the second timer reaches the second delay time duration. Similarly, after the first delay time period is reached, a computing chip such as a CPU in the transmitter may control the synchronization triggering unit 103 to send the previously generated synchronization signal to the synchronization sensing unit 201, which is not limited in this application.
The second delay time is equal to a time difference between a time when the DAC unit 105 finishes receiving the digital rf signal and a time when the DDS unit 104 finishes generating the digital rf signal.
The synchronization sensing unit 201 can output the synchronization signal to the DDC unit 203 immediately after receiving the synchronization signal sent by the synchronization triggering unit 103.
In this case, after receiving the frequency control word output by the frequency control word receiving unit 202, the DDC unit 203 does not generate a digital rf signal according to the frequency control word immediately, but generates a digital rf signal according to the frequency control word only under the trigger of the synchronization update signal received by the synchronization sensing unit 201.
In summary, after the frequency control word generating unit 101 finishes generating the frequency control word and a first delay time period elapses, the frequency control word receiving unit 202 finishes receiving the frequency control word; after the sum of the first delay time and the second delay time, the DAC unit 105 completes receiving the digital radio frequency signal and starts to convert the digital radio frequency signal into an analog radio frequency signal; at the same time, the synchronization sensing unit 201 also completes receiving the synchronization signal, and since the dcp word receiving unit 202 has completed receiving the dcp word at this time, the DDC unit 203 can immediately start generating the same digital rf signal.
Therefore, the analog radio frequency signal for exciting the detected body is always synchronous with the digital radio frequency signal generated by the receiver for magnetic resonance imaging, and the analog radio frequency signal output by the transmitter and the digital radio frequency signal generated by the receiver are derived from the same frequency control word. Therefore, when the frequency control word for controlling the generation of the radio frequency signal is updated, the synchronous switching of the frequency of the analog radio frequency signal output by the transmitter and the frequency of the digital radio frequency signal generated by the receiver can be ensured, so that the transmitter and the receiver keep a fixed phase difference, and the phase coherence of the transmitter and the receiver is ensured.
Fig. 4 is a schematic diagram of another magnetic resonance apparatus according to an exemplary embodiment of the present application. As shown in fig. 4, the magnetic resonance apparatus 2 may include a transmitter 30 and a receiver 40.
Compared with the transmitter 10, the transmitter 30 may further include: a photoelectric conversion unit 106; the receiver 40 may further include, in comparison with the receiver 20: an electro-optical conversion unit 204.
In the transmitter 30, the photoelectric conversion unit 106 may be connected with the synchronization triggering unit 103; in the receiver 40, the electrical-to-optical conversion unit 204 may be connected to the synchronization sensing unit 201.
It should be noted that, at this time, the synchronization triggering unit 103 in the transmitter 30 and the synchronization sensing unit 201 in the receiver 40 are no longer connected, but are connected by the photoelectric conversion unit 106 in the transmitter 30 and the electro-optical conversion unit 204 in the receiver 40.
In contrast to the embodiment shown in fig. 3, at this time, the synchronization triggering unit 103 may transmit the generated synchronization signal to the photoelectric conversion unit 106. The photoelectric conversion unit 106 may convert the synchronization signal from an electrical signal to an optical signal and transmit the optical signal to the electro-optical conversion unit 204 through a high-speed optical fiber.
The electrical-to-optical conversion unit 204 can convert the optical signal into an electrical signal again and output the electrical signal to the synchronization sensing unit 201, so that the synchronization sensing unit 201 can receive the synchronization signal.
Therefore, when the distance between the positions of the transmitter and the receiver is long, the transmission speed of the synchronous signals between the transmitter and the receiver can be increased, the transmission time of the synchronous signals between the transmitter and the receiver approaches to 0, and the phase deviation of the transmitter and the receiver caused by the transmission time of the synchronous signals is avoided.
In an alternative embodiment, with continued reference to fig. 4, the transmitter 30 may further include: the main magnetic field adjusting unit 107 and B0 compensate the calculating unit 108.
The main magnetic field adjusting unit 107 may receive a main magnetic field frequency parameter sent by an upper computer, and generate a first frequency control word according to the main magnetic field frequency parameter, and the B0 compensation calculating unit 108 may update a B0 compensation value according to an influence factor of a gradient coil eddy current at regular intervals, and generate a second frequency control word according to the updated B0 compensation value and a preset weighting coefficient. The interval time may be preset by the user or may be a default value.
At this time, the frequency control word generating unit 101 may add the first frequency control word and the second frequency control word, and use the added frequency control word as a frequency control word for controlling the generation of the radio frequency signal.
Alternatively, the upper computer may transmit different frequency parameters to the frequency control word generating unit 101 at regular intervals, so that the frequency control word generating unit 101 generates a frequency control word for controlling generation of the radio frequency signal.
Referring to fig. 5, a flowchart of a radio frequency signal generating method according to an exemplary embodiment of the present application is shown. The method can be applied to the transmitter shown in fig. 1, and comprises the following steps:
step 501: a frequency control word is generated that controls the generation of the radio frequency signal.
Step 502: the frequency control word is sent to a receiver.
Step 503: and generating a synchronous signal and sending the synchronous signal to the receiver so that the receiver generates a digital radio frequency signal according to the frequency control word under the triggering of the synchronous signal.
Step 504: and under the triggering of the synchronous signal, generating a digital radio frequency signal according to the frequency control word.
Step 505: converting the digital radio frequency signal into an analog radio frequency signal; the moment when the transmitter starts to convert the digital radio frequency signal into the analog radio frequency signal is a first moment, the moment when the receiver receives the synchronous signal is a second moment, the moment when the receiver receives the frequency control word is a third moment, the second moment is the same as the first moment, and the third moment is earlier than the first moment.
In this embodiment, the transmitter may transmit the frequency control word to the receiver after generating the frequency control word. Wherein the frequency control word may be used to control the generation of the radio frequency signal, which may be used to generate a magnetic resonance sequence for performing a magnetic resonance scan of the object.
Subsequently, the transmitter may generate a synchronization signal. On one hand, the transmitter can generate a digital radio frequency signal according to the frequency control word under the triggering of the synchronous signal; on the other hand, the transmitter may transmit the synchronization signal to the receiver, so that the receiver may generate a digital radio frequency signal according to the previously received frequency control word under the trigger of the received synchronization signal.
The transmitter, after generating the digital radio frequency signal, may convert the digital radio frequency signal to an analog radio frequency signal.
In this embodiment, a time when the transmitter starts to convert the digital rf signal into the analog rf signal may be referred to as a first time, a time when the receiver receives the synchronization signal may be referred to as a second time, and a time when the receiver receives the frequency control word may be referred to as a third time.
In an alternative embodiment, after the transmitter generates the synchronization signal in step 503, the transmitter may first convert the synchronization signal from an electrical signal form to an optical signal form, and then transmit the synchronization signal in the optical signal form obtained by conversion to the receiver through the high-speed optical fiber. And the receiver can convert the optical signal form of the synchronization signal into an electrical signal form of the synchronization signal after receiving the optical signal form of the synchronization signal.
In another alternative embodiment, the transmitter may receive the primary magnetic field frequency parameters transmitted by the upper computer and generate the first frequency control word according to the primary magnetic field frequency parameters. In addition, the transmitter may update the B0 compensation value according to the gradient coil eddy current at preset intervals, and generate the second frequency control word according to the updated B0 compensation value and a preset weighting coefficient. In this case, the transmitter may add the first frequency control word and the second frequency control word, and determine the added frequency control word as a frequency control word controlling the generation of the radio frequency signal.
Referring to fig. 6, a flowchart of another radio frequency signal generating method according to an exemplary embodiment of the present application is shown. The method can be applied to the receiver shown in fig. 2, and comprises the following steps:
step 601: receiving a synchronization signal transmitted by a transmitter, the synchronization signal being generated by the transmitter.
Step 602: and receiving the frequency control word sent by the transmitter, wherein the frequency control word is generated by the transmitter.
Step 603: under the trigger of the synchronous signal, generating a digital radio frequency signal according to the frequency control word; the moment when the transmitter starts to convert the digital radio frequency signal into the analog radio frequency signal is a first moment, the moment when the receiver receives the synchronous signal is a second moment, the moment when the receiver receives the frequency control word is a third moment, the second moment is the same as the first moment, and the third moment is earlier than the first moment.
In this embodiment, the receiver may receive the frequency control word and the synchronization signal transmitted by the transmitter. Wherein the frequency control word and the synchronization signal are both generated by the transmitter.
Subsequently, the receiver can generate a digital radio frequency signal according to the frequency control word under the trigger of the synchronization signal.
On the other hand, the transmitter may also generate a digital frequency signal according to the frequency control word generated by the transmitter under the trigger of the synchronization signal generated by the transmitter, and convert the generated digital frequency signal into an analog digital signal.
In this embodiment, a time when the transmitter starts to convert the digital rf signal into the analog rf signal may be referred to as a first time, a time when the receiver receives the synchronization signal may be referred to as a second time, and a time when the receiver receives the frequency control word may be referred to as a third time.
In an alternative embodiment, the transmitter may convert the generated synchronization signal from an electrical signal form to an optical signal form, and then transmit the converted synchronization signal in the optical signal form to the receiver through the high-speed optical fiber. After receiving the synchronization signal in the form of the optical signal in the foregoing step 601, the receiver may convert the synchronization signal in the form of the optical signal into the synchronization signal in the form of an electrical signal.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the scope of protection of the present application.
Claims (11)
1. A transmitter, characterized in that the transmitter comprises:
a frequency control word generating unit for generating a frequency control word for controlling generation of the radio frequency signal;
a frequency control word transmitting unit for transmitting the frequency control word to a frequency control word receiving unit in a receiver;
the synchronous trigger unit is used for generating a synchronous signal and sending the synchronous signal to a synchronous induction unit in the receiver so that a digital down-conversion DDC unit in the receiver generates a digital radio-frequency signal according to the frequency control word under the trigger of the synchronous signal;
the direct digital frequency synthesis DDS unit is used for generating a digital radio frequency signal according to the frequency control word under the triggering of the synchronous signal;
the digital-to-analog conversion DAC unit is used for converting the digital radio frequency signal into an analog radio frequency signal;
the time when the DAC unit receives the digital radio frequency signal is a first time, the time when the synchronous sensing unit receives the synchronous signal is a second time, the time when the DDC unit receives the frequency control word is a third time, the second time is the same as the first time, and the third time is earlier than the first time.
2. The transmitter of claim 1, wherein the transmitter further comprises:
and the photoelectric conversion unit is used for converting the synchronous signal from an electric signal form to an optical signal form, and sending the synchronous signal in the optical signal form obtained by conversion to the electro-optical conversion unit in the receiver through a high-speed optical fiber so that the electro-optical conversion unit converts the synchronous signal in the optical signal form received into the synchronous signal in the electric signal form.
3. The transmitter of claim 1, wherein the transmitter further comprises:
the main magnetic field adjusting unit is used for receiving main magnetic field frequency parameters sent by an upper computer and generating first frequency control words according to the main magnetic field frequency parameters;
the B0 compensation calculation unit is used for updating a B0 compensation value according to the gradient coil eddy current at preset intervals, and generating a second frequency control word according to the updated B0 compensation value and a preset weighting coefficient;
the frequency control word sending unit is specifically configured to:
and adding the first frequency control word and the second frequency control word, and determining the frequency control word obtained by adding as a frequency control word for controlling the generation of the radio frequency signal.
4. A receiver, characterized in that the receiver comprises:
the synchronous induction unit is used for receiving a synchronous signal sent by a synchronous trigger unit in a transmitter, and the synchronous signal is generated by the synchronous trigger unit;
a frequency control word receiving unit, configured to receive a frequency control word sent by a frequency control word sending unit in the transmitter, where the frequency control word is generated by the frequency control word sending unit;
the DDC unit is used for generating a digital radio frequency signal according to the frequency control word under the triggering of the synchronous signal;
the time when the DAC unit in the transmitter receives the digital radio frequency signal is a first time, the time when the synchronous sensing unit receives the synchronous signal is a second time, the time when the DDC unit receives the frequency control word is a third time, the second time is the same as the first time, and the third time is earlier than the first time.
5. The receiver of claim 4, further comprising:
and the electro-optical conversion unit is used for receiving the synchronous signal in the form of an optical signal sent by the photoelectric conversion unit in the transmitter through a high-speed optical fiber and converting the synchronous signal in the form of the optical signal into the synchronous signal in the form of an electric signal, wherein the synchronous signal in the form of the optical signal is obtained by converting the synchronous signal in the form of the electric signal by the photoelectric conversion unit.
6. A magnetic resonance apparatus, characterized in that the magnetic resonance apparatus comprises: a transmitter as claimed in any one of claims 1 to 3, and a receiver as claimed in any one of claims 4 to 5.
7. A method for generating a radio frequency signal, the method being applied to a transmitter, the method comprising:
generating a frequency control word for controlling generation of the radio frequency signal;
transmitting the frequency control word to a receiver;
generating a synchronous signal, and sending the synchronous signal to the receiver, so that the receiver generates a digital radio frequency signal according to the frequency control word under the triggering of the synchronous signal;
under the trigger of the synchronous signal, generating a digital radio frequency signal according to the frequency control word;
converting the digital radio frequency signal into an analog radio frequency signal;
the moment when the transmitter starts to convert the digital radio frequency signal into the analog radio frequency signal is a first moment, the moment when the receiver receives the synchronous signal is a second moment, the moment when the receiver receives the frequency control word is a third moment, the second moment is the same as the first moment, and the third moment is earlier than the first moment.
8. The method of claim 7, further comprising:
and converting the synchronous signal from an electric signal form to an optical signal form, and sending the synchronous signal in the optical signal form obtained by conversion to the receiver through a high-speed optical fiber, so that the receiver converts the received synchronous signal in the optical signal form into the synchronous signal in the electric signal form.
9. The method of claim 7, further comprising:
receiving main magnetic field frequency parameters sent by an upper computer, and generating first frequency control words according to the main magnetic field frequency parameters;
updating a B0 compensation value according to the gradient coil eddy current at preset intervals, and generating a second frequency control word according to the updated B0 compensation value and a preset weighting coefficient;
the generating a frequency control word that controls the generation of the radio frequency signal includes:
and adding the first frequency control word and the second frequency control word, and determining the frequency control word obtained by adding as a frequency control word for controlling the generation of the radio frequency signal.
10. A method for generating a radio frequency signal, the method being applied to a receiver, the method comprising:
receiving a synchronization signal transmitted by a transmitter, wherein the synchronization signal is generated by the transmitter;
receiving a frequency control word sent by the transmitter, wherein the frequency control word is generated by the transmitter;
under the trigger of the synchronous signal, generating a digital radio frequency signal according to the frequency control word;
the moment when the transmitter starts to convert the digital radio frequency signal into the analog radio frequency signal is a first moment, the moment when the receiver receives the synchronous signal is a second moment, the moment when the receiver receives the frequency control word is a third moment, the second moment is the same as the first moment, and the third moment is earlier than the first moment.
11. The method of claim 10, further comprising:
and receiving the synchronous signal in the form of the optical signal sent by the transmitter through the high-speed optical fiber, and converting the synchronous signal in the form of the optical signal into the synchronous signal in the form of the electric signal, wherein the synchronous signal in the form of the optical signal is obtained by converting the synchronous signal in the form of the electric signal by the transmitter.
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