CN114062989B - Magnetic resonance spectrometer and magnetic resonance imaging system - Google Patents
Magnetic resonance spectrometer and magnetic resonance imaging system Download PDFInfo
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Abstract
The application discloses a magnetic resonance spectrometer and a magnetic resonance imaging system. The magnetic resonance spectrometer comprises: the micro control unit is respectively communicated with the gradient signal generating plate, the radio frequency pulse signal generating plate and the receiver, and is used for controlling the operations of the gradient signal generating plate, the radio frequency pulse signal generating plate and the receiver through data sent by the upper computer and sending the magnetic resonance signals acquired by the receiver to the upper computer; the radio frequency pulse signal generation plate is used for sending pulse signals to the radio frequency general coil so as to excite the radio frequency general coil to generate a radio frequency magnetic field, so that a measured object generates a magnetic resonance phenomenon, and is provided with at least two radio frequency emission sources and a detection module for detecting a radio frequency energy deposition value; the receiver is used for receiving magnetic resonance signals of the radio frequency receiving coil. The application solves the problems of poor imaging quality and potential safety hazard of the high-field magnetic resonance imaging system in the related technology.
Description
Technical Field
The application relates to the technical field of magnetic resonance, in particular to a magnetic resonance spectrometer and a magnetic resonance imaging system.
Background
The magnetic resonance signal strength is proportional to the magnetic field strength, so that the improvement of the main magnetic field strength is an effective method for improving the signal-to-noise ratio of a magnetic resonance imaging system in the technical field of magnetic resonance imaging at present, and is also the most commonly used method.
It should be noted that, the 3T and above high-field magnetic resonance imaging system is developed based on the above principle. Research shows that the high field intensity magnetic resonance with the temperature of 3T and above has obvious advantages in signal to noise ratio, and can realize structural imaging with isotropic resolution of 0.1 mm. However, high-field MRI systems have significant advantages in principle, but in practice there are a number of technical problems.
On the one hand, compared with the currently mainstream 1.5T magnetic resonance, the high-field magnetic resonance imaging system often has the problem of insufficient uniformity of a main magnetic field and a radio frequency field, and serious radio frequency artifact and susceptibility effect exist in the process of scanning in a large imaging range, so that the image quality is seriously influenced. On the other hand, high-field magnetic resonance also has serious potential safety hazards, especially risks of exceeding the standard of radio frequency energy deposition (Specific Absorption Rate, SAR) values, and the like, so that the high-field magnetic resonance has more severe safety condition limitations when high-field equipment is used.
The spectrometer is the most critical and core equipment of the magnetic resonance imaging system and is responsible for the work of sequence operation, radio frequency signal generation, space positioning gradient signal generation, radio frequency signal receiving, acquisition data reconstruction and the like. The spectrometer architecture in the related art has significantly advanced in terms of digitization and distribution, as has the reusability, stability and scanning speed of the spectrometer module. However, in order to rapidly push out high-field magnetic resonance with a frequency of 3T or more to the market, current magnetic resonance manufacturers mainly upgrade spectrometers of high-field magnetic resonance with a frequency of 1.5T, wherein the spectrometer technology only adjusts few parameters such as a receiving frequency band of magnetic resonance imaging signals, and meanwhile, the requirements of the high-field magnetic resonance with a frequency of 3T or more on the spectrometers are generally met by patching the low-field magnetic resonance spectrometers for other aspects of the high-field magnetic resonance with a frequency of 3T or more. On the one hand, the problems that the uniformity of a main magnetic field and a radio frequency field is insufficient to influence the image quality and the potential safety hazard exists due to the risks of exceeding the standard of a radio frequency energy deposition value are difficult to solve, and therefore, the high-field magnetic resonance system generated by patching on a low-field magnetic resonance spectrometer is difficult to provide metabolic information; on the other hand, in a magnetic resonance system with low field intensity, magnetic resonance signals of 1H protons are mostly used as imaging nuclides, but from the viewpoint of physiological metabolism of a human body, physiological information carried by protons is little, and any metabolic information is hardly provided.
Aiming at the problems of poor imaging quality and potential safety hazard of a high-field magnetic resonance imaging system in the related technology, no effective solution is proposed at present.
Disclosure of Invention
The application provides a magnetic resonance spectrometer and a magnetic resonance imaging system, which are used for solving the problems that the high-field magnetic resonance imaging system in the related technology is poor in imaging quality and has potential safety hazards.
According to one aspect of the application, a magnetic resonance spectrometer is provided. Comprising the following steps: the micro control unit is respectively communicated with the gradient signal generating plate, the radio frequency pulse signal generating plate and the receiver, and is used for controlling the operations of the gradient signal generating plate, the radio frequency pulse signal generating plate and the receiver through data sent by the upper computer and sending the magnetic resonance signals acquired by the receiver to the upper computer; the gradient signal generating plate is used for sending gradient waveform signals to the gradient coil so as to position a target scanning position of a tested object through the gradient waveform signals, wherein the gradient coil is arranged on the inner wall of the cylindrical magnet, and the tested object is arranged inside the cylindrical magnet; the radio frequency pulse signal generation plate is used for sending pulse signals to the radio frequency general coil so as to excite the radio frequency general coil to generate a radio frequency magnetic field and enable a measured object to generate a magnetic resonance phenomenon, wherein the radio frequency general coil is arranged on the inner wall of the cylindrical magnet, at least two radio frequency emission sources are arranged on the radio frequency pulse signal generation plate, and the at least two radio frequency emission sources are also connected with a detection module for detecting a radio frequency energy deposition value; the receiver is used for receiving magnetic resonance signals of the radio frequency receiving coil, wherein the radio frequency receiving coil is arranged in the cylindrical magnet, and the distance between the radio frequency receiving coil and the target scanning position is smaller than a preset distance.
Optionally, the magnetic resonance spectrometer further comprises a spectrometer scanning control platform, wherein the spectrometer scanning control platform is connected with the micro-control unit and is used for sending data sent by the upper computer to the micro-control unit and sending data received by the micro-control unit to the upper computer.
Optionally, the values of the configuration parameters of each of the at least two radio frequency emission sources are independently configured, wherein the configuration parameters include at least one of: amplitude, phase and frequency.
Optionally, the detection module includes a detection circuit and a control circuit that are connected, where the detection circuit is connected to a forward port of a radio frequency power amplifier and a feedback port of the radio frequency power amplifier in each radio frequency emission source, and a forward port of a quadrature coupler and a feedback port of the quadrature coupler, and is used to detect radio frequency energy deposition at a target scanning location, where an input end of the quadrature coupler is connected to each radio frequency power amplifier, an output end of the quadrature coupler is connected to a radio frequency general coil, and the control circuit is used to control the radio frequency emission source to stop working when a radio frequency energy deposition value at the target scanning location is greater than a preset value.
Optionally, the gradient signal generating board further receives a gradient waveform parameter and a zero-order eddy current compensation parameter sent by the upper computer, calculates a carrier frequency compensation amount according to the gradient waveform parameter and the zero-order eddy current compensation parameter, and sends the carrier frequency compensation amount to the radio frequency pulse signal generating board and the receiver so as to superimpose the carrier frequency compensation amount on the carrier frequency of the radio frequency pulse signal generating board and the carrier frequency of the receiver, wherein the zero-order eddy current compensation parameter comprises a time parameter and an amplitude parameter corresponding to a zero-order item of eddy current.
Optionally, the gradient signal generating board further receives a first-order shimming parameter sent by the upper computer, and the first-order shimming parameter is added to the gradient waveform signal, wherein the first-order shimming parameter is bias voltage.
Optionally, the gradient signal generating board further receives parameters of the higher order shimming sent by the upper computer, and transmits the parameters of the higher order shimming to the shimming power supply, wherein the parameters of the higher order shimming are bias currents.
Optionally, a plurality of first band-pass filters are respectively arranged at the output end of each radio frequency emission source, wherein the center frequency of each first band-pass filter is the frequency required by one type of nuclide imaging; a plurality of second band-pass filters are correspondingly arranged at the input end of a receiving channel of the receiver respectively, wherein the center frequency of each second band-pass filter is the same as the center frequency of one first band-pass filter.
Optionally, a first modulation module is further arranged between the output end of each radio frequency emission source and the plurality of first band-pass filters, and is used for modulating the amplitude of the pulse signal output by the radio frequency emission source, wherein the modulation module stores a plurality of first local oscillation frequencies, and each first local oscillation frequency is the frequency required by one type of nuclide imaging; and a second modulation module is further arranged between the output ends of the plurality of first band-pass filters and the input end of the receiving channel of the receiver and is used for carrying out amplitude demodulation on the received magnetic resonance signals, wherein the second modulation module stores a plurality of second local oscillation frequencies, and each second local oscillation frequency is identical to one first local oscillation frequency.
According to one aspect of the application, a magnetic resonance imaging system is provided. Comprising the following steps: a magnetic resonance spectrometer as in any one of the above; the imaging module is connected with the magnetic resonance spectrometer and is used for receiving data acquired by the magnetic resonance spectrometer and generating an image according to the acquired data; the upper computer is connected with the magnetic resonance spectrometer through the network switch and is used for sending a control instruction to the magnetic resonance spectrometer and receiving data acquired by the magnetic resonance spectrometer; and the imaging module is also connected with the network switch and used for sending a control instruction to the imaging module and receiving the image generated by the imaging module.
By the application, the following steps are adopted: the micro control unit is respectively communicated with the gradient signal generating plate, the radio frequency pulse signal generating plate and the receiver, and is used for controlling the operations of the gradient signal generating plate, the radio frequency pulse signal generating plate and the receiver through data sent by the upper computer and sending the magnetic resonance signals acquired by the receiver to the upper computer; the gradient signal generating plate is used for sending gradient waveform signals to the gradient coil so as to position a target scanning position of a tested object through the gradient waveform signals, wherein the gradient coil is arranged on the inner wall of the cylindrical magnet, and the tested object is arranged inside the cylindrical magnet; the radio frequency pulse signal generation plate is used for sending pulse signals to the radio frequency general coil so as to excite the radio frequency general coil to generate a radio frequency magnetic field and enable a measured object to generate a magnetic resonance phenomenon, wherein the radio frequency general coil is arranged on the inner wall of the cylindrical magnet, at least two radio frequency emission sources are arranged on the radio frequency pulse signal generation plate, and the at least two radio frequency emission sources are also connected with a detection module for detecting a radio frequency energy deposition value; the receiver is used for receiving magnetic resonance signals of the radio frequency receiving coil, wherein the radio frequency receiving coil is arranged in the cylindrical magnet, the distance between the radio frequency receiving coil and the target scanning position is smaller than a preset distance, and the problems that the high-field magnetic resonance imaging system in the related technology is poor in imaging quality and has potential safety hazards are solved. The radio frequency pulse signal generation board is provided with at least two radio frequency emission sources and the detection module for detecting the radio frequency energy deposition value, so that multi-source emission and SAR value monitoring are realized in one unit, the product integration level is improved, the software control process is simplified, the SAR value detection module is convenient for timely reporting abnormal information to the control circuit, the control circuit can timely enable the radio frequency emission function, and the effects of improving the imaging quality of a high-field magnetic resonance imaging system and reducing potential safety hazards are achieved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:
FIG. 1 is a schematic diagram of a magnetic resonance spectrometer provided in accordance with an embodiment of the present application;
FIG. 2 is a schematic diagram of a detection module in a magnetic resonance spectrometer provided in accordance with an embodiment of the present application;
FIG. 3 is a schematic diagram of calculating a carrier frequency compensation amount from gradient waveform parameters and zero-order eddy current compensation parameters, provided in accordance with an embodiment of the application;
FIG. 4 is a first order shimming schematic provided in accordance with an embodiment of the present application;
FIG. 5 is a schematic diagram of an alternative RF pulse signal generator board provided in accordance with an embodiment of the present application;
fig. 6 is a schematic diagram of an alternative receiver provided in accordance with an embodiment of the present application;
fig. 7 is a schematic diagram of a magnetic resonance imaging system provided according to an embodiment of the present application.
Detailed Description
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The application will be described in detail below with reference to the drawings in connection with embodiments.
In order that those skilled in the art will better understand the present application, a technical solution in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present application without making any inventive effort, shall fall within the scope of the present application.
It should be noted that the terms "first," "second," and the like in the description and the claims of the present application and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate in order to describe the embodiments of the application herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
According to an embodiment of the present application, a magnetic resonance spectrometer is provided.
Figure 1 is a schematic diagram of a magnetic resonance spectrometer according to an embodiment of the present application. As shown in fig. 1, the magnetic resonance spectrometer includes:
the micro control unit 10 is respectively in communication with the gradient signal generating board 20, the radio frequency pulse signal generating board 30 and the receiver 40, and is used for controlling the operations of the gradient signal generating board 20, the radio frequency pulse signal generating board 30 and the receiver 40 through data sent by the upper computer, and sending magnetic resonance signals acquired by the receiver 40 to the upper computer.
The micro control unit 10, abbreviated as MCU (Main Control Unit, MCU), the hardware composition of the MCU itself includes: the system comprises a plurality of high-speed optical fiber ports, a high-precision clock source generation module, a self-checking and debugging module, a temperature monitoring module, an FPGA module, a board information storage module, a power supply monitoring module and the like. The MCU can be connected with each hardware terminal of the magnetic resonance spectrometer based on a star-shaped topological structure, and manages each hardware terminal, so that all hardware terminals are formed into a whole, and meanwhile, each hardware terminal exchanges information through the MCU to realize information synchronization.
Optionally, in the magnetic resonance spectrometer provided by the embodiment of the present application, the magnetic resonance spectrometer further includes a spectrometer scanning control platform 50, where the spectrometer scanning control platform 50 is connected to the micro-control unit 10, and is configured to send data sent by the upper computer to the micro-control unit 10, and send data received by the micro-control unit 10 to the upper computer.
Specifically, the spectrometer scan control platform 50 is used for exchanging information, and it receives a high-order instruction of the upper computer, compiles the high-order instruction into data identifiable by the hardware MCU, and also receives data sent by the MCU, compiles the data identifiable by the upper computer.
In addition, the magnetic resonance spectrometer further comprises a monitoring unit 60 connected with the MCU for monitoring the operation of each terminal module connected with the MCU.
Wherein the gradient signal generating plate 20 is used for transmitting gradient waveform signals to gradient coils so as to locate a target scanning position of a measured object through the gradient waveform signals, wherein the gradient coils are arranged on the inner wall of the cylindrical magnet, and the measured object is arranged inside the cylindrical magnet.
Specifically, the hardware composition of the gradient signal generating board 20 itself includes: the system comprises a gradient output module, a gradient amplifier reference clock module, a gradient optical fiber communication module, a gate control module, an upper computer optical fiber communication module, a shimming power supply communication module, a self-checking and debugging module, a temperature monitoring module, an FPGA module, a gradient board information storage module, a power supply and power supply monitoring module and the like. The gradient signal generating board 20 analyzes the gradient event under the control of the spectrometer scanning control platform 50, thereby completing the generation of the three-axis high-precision gradient waveform.
The rf pulse signal generating board 30 is configured to send a pulse signal to the rf general coil to excite the rf general coil to generate an rf magnetic field, so that the measured object generates a magnetic resonance phenomenon, where the rf general coil is disposed on an inner wall of the cylindrical magnet, at least two rf emission sources are disposed on the rf pulse signal generating board, and the at least two rf emission sources are further connected with a detection module for detecting a deposition value of rf energy.
Specifically, the hardware components of the rf pulse signal generating board 30 itself include: the system comprises a power supply module, an FPGA module, an SAR value real-time detection module, a board card information storage module, a power supply monitoring module, a LED (Light Emitting Diode) indication unit and the like. In one aspect, the arrangement of at least two rf emission sources enables the rf pulse signal generating board 30 to generate rf pulse signals of multiple physical channels and output the rf pulse signals to the rf power amplifier, thereby significantly reducing the non-uniformity of the rf field to reduce a large amount of deposition of local SAR values. On the other hand, the detection module is arranged, and the radio frequency pulse signal generation board 30 detects local radio frequency energy deposition values (Specific Absorption Rate, SAR) so as to avoid potential safety hazards caused by the radio frequency energy deposition in the working process of the magnetic resonance spectrometer. In addition, multisource emission and SAR value monitoring are integrated into one unit to achieve, product integration level is improved, software control flow is simplified, abnormal information is conveniently reported to a control circuit by an SAR value detection module in time, and therefore the control circuit can timely enable a radio frequency emission function, and further the effects of improving imaging quality of a high-field magnetic resonance imaging system and reducing potential safety hazards are achieved.
Optionally, in the magnetic resonance spectrometer provided by the embodiment of the present application, values of configuration parameters of each of the at least two radio frequency emission sources are configured independently, where the configuration parameters include at least one of the following: amplitude, phase and frequency.
Specifically, the radio frequency pulse envelope waveform, amplitude value, frequency and phase of each radio frequency emission source can be independently controlled and can be adjusted according to different scanning objects, on one hand, the non-uniformity of an MRI radio frequency field can be obviously reduced, so that an imaging image achieves better uniformity and contrast, and higher imaging spatial resolution is realized; on the other hand, the radio frequency energy deposition distribution in the imaging area is more uniform, the local SAR value is reduced, and the safety of scanning patients is improved.
For example, for magnetic resonance with 3T field strength, two completely independent rf emission sources may be designed on the rf pulse emission board. For another example, for magnetic resonance with field strengths above 7T, the radio frequency transmit channels may be increased to 8 channels, further improving the uniformity of the radio frequency field on the basis of 3T magnetic resonance, while reducing the local SAR value.
The receiver 40 is configured to receive a magnetic resonance signal of a radio frequency receiving coil, where the radio frequency receiving coil is disposed inside the cylindrical magnet, and a distance between the radio frequency receiving coil and a target scanning location is smaller than a preset distance.
Specifically, the receiver 40 hardware components include: at least one high-speed optical fiber port, an analog-to-digital converter (ADC, A nalog-to-Digital Converter), a programmable digital control gain device, an acoustic surface band-pass filter, a clock generation module with low phase noise, a self-checking and debugging module, a temperature monitoring module, an FPGA module, a board information storage module, a power supply monitoring module and the like.
In order to facilitate the layout and expansion of the receivers 40, it should be noted that the receivers 40 may include a plurality of receivers 40, each provided with a plurality of signal receiving channels, and receive the weak magnetic resonance signals from the rf receiving coil, and perform low noise amplification, sample quantization, quadrature demodulation, decimation filtering, and the like on the signals. Alternatively, each receiver 40 is designed as 16 receiving channels, and 8 receivers 40 are laid out simultaneously on the side of the magnet, thereby expanding to 128 receiving channels.
The magnetic resonance spectrometer provided by the embodiment of the application is respectively communicated with the gradient signal generating board 20, the radio frequency pulse signal generating board 30 and the receiver 40 through the micro control unit 10, and is used for controlling the operations of the gradient signal generating board 20, the radio frequency pulse signal generating board 30 and the receiver 40 through data sent by an upper computer and sending magnetic resonance signals acquired by the receiver 40 to the upper computer; wherein the gradient signal generating board 20 is used for sending gradient waveform signals to the gradient coils so as to locate a target scanning position of a measured object through the gradient waveform signals, wherein the gradient coils are arranged on the inner wall of the cylindrical magnet, and the measured object is arranged inside the cylindrical magnet; the rf pulse signal generating plate 30 is configured to send a pulse signal to the rf general coil to excite the rf general coil to generate an rf magnetic field, so that the measured object generates a magnetic resonance phenomenon, where the rf general coil is disposed on an inner wall of the cylindrical magnet, at least two rf emission sources are disposed on the rf pulse signal generating plate, and the at least two rf emission sources are further connected with a detection module for detecting a deposition value of rf energy; the receiver 40 is configured to receive a magnetic resonance signal of a radio frequency receiving coil, where the radio frequency receiving coil is disposed inside the cylindrical magnet, and a distance between the radio frequency receiving coil and a target scanning location is smaller than a preset distance, so as to solve the problems of poor imaging quality and potential safety hazard of the high-field magnetic resonance imaging system in the related art. The radio frequency pulse signal generation board is provided with at least two radio frequency emission sources and the detection module for detecting the radio frequency energy deposition value, so that multi-source emission and SAR value monitoring are realized in one unit, the product integration level is improved, the software control process is simplified, the SAR value detection module is convenient for timely reporting abnormal information to the control circuit, the control circuit can timely enable the radio frequency emission function, and the effects of improving the imaging quality of a high-field magnetic resonance imaging system and reducing potential safety hazards are achieved.
Optionally, in the magnetic resonance spectrometer provided by the embodiment of the present application, the detection module includes a detection circuit and a control circuit that are connected, where the detection circuit is connected to a forward port of a radio frequency power amplifier and a feedback port of the radio frequency power amplifier in each radio frequency emission source, and a forward port of a quadrature coupler and a feedback port of the quadrature coupler, and is used to detect radio frequency energy deposition at a scan site of a measured object, where an input end of the quadrature coupler is connected to each radio frequency power amplifier, an output end of the quadrature coupler is connected to a radio frequency general coil, and the control circuit is used to control the radio frequency emission source to stop working when a radio frequency energy deposition value at a target scan site is greater than a preset value.
As shown in fig. 2, for a radio frequency signal generating board provided with 2 radio frequency emission sources, a detection circuit in a detection module detects SAR values of a forward port and a backward port of a dual-channel radio frequency power amplifier, a forward port and a backward port of a quadrature coupler in real time, and detection of SAR values of each monitoring point on a radio frequency emission link is realized. The detection module further comprises an SAR value calculation unit, and radio frequency deposition energy effectively loaded to the target scanning position is obtained through calculation according to SAR values of all the monitoring points. If the radio frequency deposition energy exceeds the standard, the radio frequency emission source is disabled through a scanning object safety protection mechanism of the control circuit, the radio frequency pulse signal output by the radio frequency emission source to the radio frequency power amplifier is cut off, the hardware real-time interruption is realized, specifically, the real-time response speed can reach the us level, the further increase of the radio frequency deposition energy is effectively avoided, and the potential safety hazard is reduced.
In order to improve the detection accuracy of the nmr signal, optionally, in the magnetic resonance spectrometer provided in the embodiment of the present application, the gradient signal generating board 20 further receives a gradient waveform parameter and a zero-order eddy current compensation parameter sent by the host computer, calculates a carrier frequency compensation amount according to the gradient waveform parameter and the zero-order eddy current compensation parameter, and sends the carrier frequency compensation amount to the rf pulse signal generating board 30 and the receiver 40, so as to superimpose the carrier frequency compensation amount on the carrier frequency of the rf pulse signal generating board 30 and the carrier frequency of the receiver 40, where the zero-order eddy current compensation parameter includes a time parameter and an amplitude parameter corresponding to a zero-order term of the eddy current.
It should be noted that, the gradient waveform generated by the gradient signal generating board 20 may cause a frequency drift of the B0 field generated by the large magnet, and the frequency of the B0 field is the frequency of the carrier signal of the rf pulse signal generating board 30 and the receiver 40, and the frequency drift of the B0 field changes the frequency of the carrier signal, thereby affecting the detection accuracy of the nmr signal, so that the carrier frequency needs to be compensated.
It should be noted that, the gradient waveform parameters include three-axis (X, Y, Z) gradient waveform parameters, specifically include parameters for determining the shape of the gradient waveform, such as the slope, duty cycle, frequency, and effective value of the rising edge and the falling edge, and the zero-order eddy current compensation parameters include three-axis (X, Y, Z) zero-order eddy current compensation parameters, specifically include time parameters and amplitude parameters corresponding to the zero-order term of the eddy current.
Specifically, as shown in fig. 3, an X-axis B0 main frequency compensation amount b0_pre-emp X is calculated by an X-axis gradient waveform parameter and an X-axis zero-order eddy current compensation parameter; calculating to obtain a Y-axis B0 main frequency compensation quantity B0_pre-emp Y through a Y-axis gradient waveform parameter and a Y-axis zero-order eddy current compensation parameter; and calculating to obtain a Z-axis B0 main frequency compensation quantity B0_pre-emp Z through the Z-axis gradient waveform parameter and the Z-axis zero-order vortex compensation parameter. Then, B0_pre-emp X, B0_pre-emp Y and B0_pre-emp Z are accumulated together to obtain B0_pre-emp, and B0_pre-emp is the carrier frequency compensation quantity. Further, the carrier frequency compensation is simultaneously transmitted to the rf pulse signal generating board 30 and the receiver 40, and the carrier frequency compensation is respectively superimposed on the digital local oscillators of the rf pulse signal generating board 30 and the receiver 40. Specifically, the time accuracy of controlling the compensation amount may be compensated for every 1us, and the frequency compensation amount accuracy may reach 1Hz.
It should be noted that, in this embodiment, only one message channel is reserved from the gradient signal generating board 20 to the rf pulse signal generating board 30 and the receiver 40, so that the carrier frequency compensation amount can be sent to the rf pulse transmitting board 30 and the receiver 40 in real time, and the architecture of the magnetic resonance spectrometer is not changed while the carrier frequency compensation is implemented, so that the maintenance and the upgrade of the magnetic resonance spectrometer are facilitated.
In the high-field magnetic resonance system, the uniformity of the magnetic field at different positions inside the cavity of the cylindrical magnet may deviate to a certain extent, and in order to obtain a magnetic resonance image with uniform gray scale, the gradient field needs to be compensated.
Specifically, as shown in fig. 4, in the process of generating the gradient waveform digital signal through the gradient waveform parameters, during the switching of the radio frequency selective layer in the sequence operation, the calculated parameters (x_shimming, y_shimming, z_shimming) of the first-order shimming of the corresponding radio frequency selective layer, that is, the bias voltages of the respective axes, are transmitted to the X, Y, Z-axis gradient waveform digital channel of the gradient signal generating board 20, superimposed on the gradient waveform digital signal of the respective axes, the gradient waveform digital signal superimposed with the parameters of the first-order shimming is output to the analog-to-digital conversion unit, and then converted into the gradient analog waveform signal, so as to realize the first-order shimming, thereby improving the uniformity of the gradient magnetic field distribution.
In order to improve the uniformity of each magnetic field and thus improve the imaging quality, optionally, in the magnetic resonance spectrometer provided in the embodiment of the present application, the gradient signal generating board 20 further receives the parameters of the higher order shimming sent by the host computer, and transmits the parameters of the higher order shimming to the shimming power supply, where the parameters of the higher order shimming are bias currents.
Specifically, during the switching of the repetition time (Time of Repetition, abbreviated as TR) in the sequence operation, the parameters of the higher order shimming are transmitted to the interface of the shimming power supply of the gradient signal generating plate 20, and then the parameters of the higher order shimming are transmitted to the shimming power supply according to the communication protocol specified by the shimming power supply, so that the shimming power supply is improved to supply power to the shimming coils, and the uniformity of each magnetic field is improved.
According to the embodiment, a first-order slice shimming technology and a high-order dynamic shimming technology are adopted, so that the dynamic magnetic field shimming effect is improved, the imaging uniformity is improved, the image geometric deformation is reduced, particularly, the dispersed image with larger susceptibility image is reduced, the whole-body dispersed imaging quality can be greatly improved under the condition that extra time is hardly increased, the splicing artifacts among different scanning sections are reduced, and the imaging quality of a conventional dispersed challenge part is remarkably improved.
In a low-field magnetic resonance system, a magnetic resonance signal of a 1H proton is generally used as an imaging nuclide, but from the viewpoint of physiological metabolism of a human body, physiological information carried by the proton is very small, and any metabolic information is hardly provided. Some aprotic nuclides, such as 23Na sodium, 31P phosphorus and the like, reflect the electrolyte equilibrium concentration inside and outside cells and tissues, carry more physiological and metabolic information of human bodies, and can provide magnetic resonance signals, but the content of the aprotic nuclides in the living body is reduced by thousands times compared with that of water molecules, so that the obtained magnetic resonance image has very low signal-to-noise ratio (SNR), and has no practical significance in a low-field-intensity magnetic resonance imaging system. Thus, current spectrometers generally only consider the frequencies required for 1H imaging, and do not consider the frequencies required for 23Na, 31P imaging.
With popularization and application of an ultra-high field strength (7T, 9.4T) magnetic resonance imaging system, because the signal-to-noise ratio of a magnetic resonance image is enhanced along with the enhancement of the magnetic field strength, the imaging of aprotic heteronuclear nuclides such as 23Na, 31P and the like becomes possible, optionally, in the magnetic resonance spectrometer provided by the embodiment of the application, a plurality of first band-pass filters are respectively arranged at the output end of each radio frequency emission source, wherein the center frequency of each first band-pass filter is the frequency required by one type of nuclide imaging; a plurality of second band-pass filters are respectively and correspondingly arranged at the input end of the receiving channel of the receiver 40, wherein the center frequency of each second band-pass filter is the same as the center frequency of one first filter.
Optionally, in the magnetic resonance spectrometer provided by the embodiment of the present application, a first modulation module is further disposed between an output end of each radio frequency emission source and the plurality of first band pass filters, and is configured to perform amplitude modulation on a pulse signal output by the radio frequency emission source, where the modulation module stores a plurality of first local oscillation frequencies, and each first local oscillation frequency is a frequency required for imaging a type of nuclide; a second modulation module is further disposed between the output ends of the plurality of first band pass filters and the input end of the receiving channel of the receiver 40, and is configured to perform amplitude demodulation on the received magnetic resonance signal, where the second modulation module stores a plurality of second local oscillation frequencies, and each second local oscillation frequency is the same as one of the first local oscillation frequencies.
Specifically, multiple sets of bandpass filters and local oscillation frequencies are respectively arranged on the rf pulse signal generating board 30 and the receiver 40, and when 1H, 23Na and 31P are imaged, one radio frequency switch with one-to-three switching is used, the switching speed can be completed within 1us, and the bandpass filters and local oscillation frequencies of the rf pulse signal generating board 30 and the receiver 40 can be rapidly switched to the center frequencies required by 1H, 23Na and 31P imaging.
In an alternative embodiment, as shown in fig. 5, taking 3T magnetic resonance imaging as an example, in digital logic of each physical transmission channel of the radio frequency pulse signal generating board 30, amplitude modulation of each nuclide signal shares a quadrature modulation module, but each nuclide signal has an independent local oscillation control word, and for 1H signal, a local oscillation register 1 is used, and its value is set to 127.5MHz; for the 23Na signal, a local oscillation register 2 is used, the value of which is set to 33.83MHz; for the 31P signal, a local oscillation register 3 is used, the value of which is set to 51.73MHz.
Meanwhile, a group of band-pass filters 1 with the center frequency of 127.5MHz and the-3 dB bandwidth of 1MHz are arranged in the analog circuits of all physical transmission channels of the radio frequency pulse signal generating board 30 for 1H signals; for 23Na signals, a group of band-pass filters 2 with the center frequency of 33.83MHz and the bandwidth of-3 dB of 1MHz are arranged; for 31P signals, a group of band-pass filters 3 with center frequency of 51.73MHz and 3dB bandwidth of 1MHz are arranged, and the band-pass filters are switched by using a radio frequency switch with one to three.
As shown in fig. 6, for example, in the case of 3T MRI, a set of bandpass filters is designed for each nuclear species imaging in the analog circuits of each physical receive channel of the receiver 40. As shown in the following diagram, for a 1H signal, a set of band-pass filters 1 with a center frequency of 127.5MHz and a 3dB bandwidth of 1MHz are provided; for 23Na signals, a group of band-pass filters 2 with the center frequency of 33.83MHz and the bandwidth of-3 dB of 1MHz are arranged; for 31P signals, a set of band pass filters 3 with a center frequency of 51.73MHz and a 3dB bandwidth of 1MHz is provided. The bandpass filter switches are switched using a radio frequency switch of one-to-three.
Meanwhile, in the digital logic of each physical receiving channel of the receiver 40, the amplitude demodulation of each nuclide signal shares one quadrature demodulation module, but each nuclide signal has an independent local oscillation control word, and for the 1H signal, a local oscillation register 1 is used, and the value of the local oscillation register 1 is set to 127.5MHz; for the 23Na signal, a local oscillation register 2 is used, the value of which is set to 33.83MHz; for the 31P signal, a local oscillation register 3 is used, the value of which is set to 51.73MHz.
Through the embodiment, a plurality of groups of band-pass filters and local oscillation frequencies are respectively arranged on the radio frequency pulse signal generating board 30 and the receiver 40, and the center frequencies required by imaging different nuclides can be obtained through switching, so that multi-core imaging is realized, and compared with single 1H imaging, the magnetic resonance imaging can obtain more abundant physiological and metabolic information of human bodies.
According to another embodiment of the present application, a magnetic resonance imaging system is provided.
Figure 7 is a schematic diagram of a magnetic resonance imaging system according to an embodiment of the present application. As shown in fig. 7, the magnetic resonance imaging system includes:
the magnetic resonance spectrometer 11 of any one of the above.
An imaging module 13, connected to the magnetic resonance spectrometer 11, for receiving the data acquired by the magnetic resonance spectrometer 11 and generating an image based on the acquired data.
The upper computer 12 is connected with the magnetic resonance spectrometer 11 through a network switch and is used for sending a control instruction to the magnetic resonance spectrometer 11 and receiving data acquired by the magnetic resonance spectrometer 11; and is also connected with the imaging module 13 through a network switch, and is used for sending a control instruction to the imaging module 13 and receiving an image generated by the imaging module 13.
Specifically, the upper computer 12 may be a scanning workbench, the upper computer 12 sends a start instruction to the magnetic resonance spectrometer 11, and sends parameters required by the work to the magnetic resonance spectrometer 11, specifically, the instruction or the data is sent to the MCU of the magnetic resonance spectrometer 11, and then the MCU of the magnetic resonance spectrometer 11 controls each connected terminal module.
The object to be measured is located in the cylindrical magnet, the gradient coil and the radio frequency general coil are arranged on the inner wall of the cylindrical magnet, the radio frequency receiving coil is also arranged in the cylindrical magnet, and the radio frequency receiving coil is located near the target scanning position of the object to be measured. After the magnetic resonance spectrometer 11 is started, the spectrometer scanning control platform controls the gradient signal generating plate to send gradient waveform signals to the gradient coil, and the target scanning position of the measured object is positioned. Further, the spectrometer scanning control platform is used for controlling the radio frequency signal generating plate to generate radio frequency signals, and pulse signals are sent to the radio frequency general coil so as to excite the radio frequency general coil to generate a radio frequency magnetic field, so that a magnetic resonance phenomenon is generated at a target scanning position of a measured object. At the same time, the receiver receives the magnetic resonance signals of the radio frequency receiving coil inside the cylindrical magnet.
After receiving the magnetic resonance signals, the receiver sends the magnetic resonance signals to the MCU of the magnetic resonance spectrometer 11, the MCU sends the magnetic resonance signals to the imaging module 13, the imaging module 13 generates images through the magnetic resonance signals and sends the generated images to the upper computer 12, an operator can check the images on the upper computer 12 and can further send data to the MCU of the magnetic resonance spectrometer 11 according to the condition of the images, and therefore imaging results are adjusted.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article or apparatus that comprises an element.
The foregoing is merely exemplary of the present application and is not intended to limit the present application. Various modifications and variations of the present application will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the application are to be included in the scope of the claims of the present application.
Claims (9)
1. A magnetic resonance spectrometer, comprising:
the micro control unit is respectively communicated with the gradient signal generating plate, the radio frequency pulse signal generating plate and the receiver, and is used for controlling the operations of the gradient signal generating plate, the radio frequency pulse signal generating plate and the receiver through data sent by the upper computer and sending magnetic resonance signals acquired by the receiver to the upper computer;
the gradient signal generating plate is used for sending gradient waveform signals to the gradient coil so as to position a target scanning position of a tested object through the gradient waveform signals, wherein the gradient coil is arranged on the inner wall of the cylindrical magnet, and the tested object is arranged inside the cylindrical magnet;
the radio frequency pulse signal generation plate is used for sending pulse signals to the radio frequency general coil so as to excite the radio frequency general coil to generate a radio frequency magnetic field and enable the tested object to generate a magnetic resonance phenomenon, wherein the radio frequency general coil is arranged on the inner wall of the cylindrical magnet, at least two radio frequency emission sources are arranged on the radio frequency pulse signal generation plate, and the at least two radio frequency emission sources are also connected with a detection module for detecting a radio frequency energy deposition value;
the detection module comprises a detection circuit and a control circuit which are connected, wherein the detection circuit is connected with a forward port of a radio frequency power amplifier in each radio frequency emission source and a backward port of the radio frequency power amplifier, and a forward port of a quadrature coupler and a backward port of the quadrature coupler, and is used for detecting radio frequency energy deposition of the target scanning position, an input end of the quadrature coupler is connected with each radio frequency power amplifier, an output end of the quadrature coupler is connected with the radio frequency general coil, and the control circuit is used for controlling the radio frequency emission source to stop working under the condition that the radio frequency energy deposition value of the target scanning position is larger than a preset value;
the receiver is used for receiving magnetic resonance signals of a radio frequency receiving coil, wherein the radio frequency receiving coil is arranged inside the cylindrical magnet, and the distance between the radio frequency receiving coil and the target scanning position is smaller than a preset distance.
2. The magnetic resonance spectrometer of claim 1, further comprising a spectrometer scan control platform, wherein the spectrometer scan control platform is coupled to the micro-control unit for transmitting data transmitted by the host computer to the micro-control unit and transmitting data received by the micro-control unit to the host computer.
3. The magnetic resonance spectrometer of claim 1, wherein the values of the configuration parameters of each of the at least two radio frequency emission sources are independently configured, wherein the configuration parameters comprise at least one of: amplitude, phase and frequency.
4. The magnetic resonance spectrometer of claim 1, wherein the gradient signal generating board further receives a gradient waveform parameter and a zero-order eddy current compensation parameter transmitted by the host computer, calculates a carrier frequency compensation amount from the gradient waveform parameter and the zero-order eddy current compensation parameter, and transmits the carrier frequency compensation amount to the radio frequency pulse signal generating board and the receiver to superimpose the carrier frequency compensation amount on a carrier frequency of the radio frequency pulse signal generating board and a carrier frequency of the receiver, wherein the zero-order eddy current compensation parameter includes a time parameter and an amplitude parameter corresponding to a zero-order term of eddy current.
5. The magnetic resonance spectrometer of claim 1, wherein the gradient signal generating board further receives parameters of a first order shimming transmitted by the host computer, and superimposes the parameters of the first order shimming onto the gradient waveform signal, wherein the parameters of the first order shimming are bias voltages.
6. The magnetic resonance spectrometer of claim 1, wherein the gradient signal generating board further receives parameters of the higher order shimming transmitted by the host computer and transmits the parameters of the higher order shimming to a shimming power supply, wherein the parameters of the higher order shimming are bias currents.
7. The magnetic resonance spectrometer as claimed in claim 1, wherein,
a plurality of first band-pass filters are respectively arranged at the output end of each radio frequency emission source, wherein the center frequency of each first band-pass filter is the frequency required by one type of nuclide imaging;
and a plurality of second band-pass filters are correspondingly arranged at the input end of a receiving channel of the receiver respectively, wherein the center frequency of each second band-pass filter is the same as the center frequency of one first band-pass filter.
8. The magnetic resonance spectrometer according to claim 7, wherein,
a first modulation module is further arranged between the output end of each radio frequency emission source and the plurality of first band-pass filters and used for carrying out amplitude modulation on pulse signals output by the radio frequency emission sources, wherein the modulation module stores a plurality of first local oscillation frequencies, and each first local oscillation frequency is a frequency required by one type of nuclide imaging;
and a second modulation module is further arranged between the output ends of the plurality of first band-pass filters and the input end of the receiving channel of the receiver and is used for carrying out amplitude demodulation on the received magnetic resonance signals, wherein the second modulation module stores a plurality of second local oscillation frequencies, and each second local oscillation frequency is identical to one first local oscillation frequency.
9. A magnetic resonance imaging system, comprising:
the magnetic resonance spectrometer of any one of claims 1 to 8;
the imaging module is connected with the magnetic resonance spectrometer and is used for receiving data acquired by the magnetic resonance spectrometer and generating an image according to the acquired data;
the upper computer is connected with the magnetic resonance spectrometer through a network switch, and is used for sending a control instruction to the magnetic resonance spectrometer and receiving data acquired by the magnetic resonance spectrometer; and the imaging module is also connected with the network switch and is used for sending a control instruction to the imaging module and receiving an image generated by the imaging module.
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