CN110895317A - Radio frequency system and radio frequency control method for magnetic resonance imaging and magnetic resonance imaging system - Google Patents
Radio frequency system and radio frequency control method for magnetic resonance imaging and magnetic resonance imaging system Download PDFInfo
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- 238000002595 magnetic resonance imaging Methods 0.000 title claims abstract description 107
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- 238000001514 detection method Methods 0.000 claims abstract description 80
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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
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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
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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
- G01R33/3614—RF power amplifiers
Abstract
The invention provides a radio frequency system and a radio frequency control method for magnetic resonance imaging and a magnetic resonance imaging system. The radio frequency system includes a radio frequency generator, a power amplifier, a transmit coil, and a radio frequency detection component. The radio frequency generator is used for generating a radio frequency pulse signal. The power amplifier is used for amplifying the radio frequency pulse signal and outputting the amplified radio frequency pulse signal. The transmitting coil is used for receiving the amplified radio frequency pulse signal to transmit the radio frequency pulse signal to a detection object. The radio frequency detection component is used for detecting a radio frequency pulse signal transmitted by the transmitting coil, and the radio frequency pulse signal detected by the radio frequency detection component is used for feedback control of the radio frequency pulse signal input to the transmitting coil.
Description
Technical Field
The invention relates to the field of medical imaging, in particular to a radio frequency system and a radio frequency control method for magnetic resonance imaging and a magnetic resonance imaging system.
Background
Magnetic Resonance Imaging (Magnetic Resonance Imaging) has been widely used in the field of medical diagnosis. The magnetic resonance imaging system forms a static magnetic field using a superconducting magnet, places a scanning object to be imaged in an imaging space of the magnetic resonance imaging system, and aligns proton spins in tissue of the scanning object with a direction of the static magnetic field so as to generate a magnetization vector. Then, a radio frequency field is generated by emitting a radio frequency pulse signal with a certain frequency for excitation. The magnetic resonance phenomenon causes the spin direction of the protons to flip, changing the magnetization vector of the protons. When the spins return the protons to their initial state of magnetization vector in the direction of the static magnetic field after the radio frequency pulse is stopped, a magnetic resonance signal is generated. The magnetic resonance signal is received by the coil and processed by the computer to obtain the image of the scanned object.
In a magnetic resonance imaging system, a radio frequency system is an important component of the magnetic resonance system, and a power amplifier is one of the key technologies of a radio frequency signal link in the magnetic resonance imaging system. Generally the better the fidelity/linearity of the power amplifier, the better the resulting image quality. However, the fidelity/linearity of a power amplifier is a closed-loop control circuit that typically forms the power amplifier by its input signal and its output power feedback signal. In other words, the prior art generally guarantees the fidelity or linearity of the rf pulse signal transmitted to the static magnetic field by guaranteeing the fidelity/linearity of the power amplifier.
However, since the body weight of different subjects is generally different, the load applied to the radio frequency coil is different. As the load changes, the fidelity/linearity of the power amplifier is affected and no longer varies linearly. If the output power of the power amplifier is still used as the feedback signal, the power variation of the whole rf signal chain cannot be truly reflected, and therefore, it is impossible to effectively control the fidelity or linearity of the whole rf signal chain. Furthermore, a typical radio frequency coil consists of many electronic diodes, which also affect the fidelity or linearity of the radio frequency signal link. The existing control method for the fidelity or linearity of the radio frequency signal link does not take these influence factors into consideration.
Therefore, it is desirable to provide a new radio frequency system and a new radio frequency control method for magnetic resonance imaging to solve at least one of the above technical problems.
Disclosure of Invention
The invention aims to provide a radio frequency system and a radio frequency control method for magnetic resonance imaging, and a magnetic resonance imaging system.
An exemplary embodiment of the present invention provides a radio frequency system for magnetic resonance imaging, which includes a radio frequency generator, a power amplifier, a transmit coil, and a radio frequency detection component. The radio frequency generator is used for generating a radio frequency pulse signal. The power amplifier is used for amplifying the radio frequency pulse signal and outputting the amplified radio frequency pulse signal. The transmitting coil is used for receiving the amplified radio frequency pulse signal to transmit the radio frequency pulse signal to a detection object. The radio frequency detection component is used for detecting the radio frequency pulse signal transmitted by the transmitting coil. The radio frequency pulse signal detected by the radio frequency detection component is used for feedback control of the radio frequency pulse signal input to the transmitting coil.
An exemplary embodiment of the present invention also provides a radio frequency control method of magnetic resonance imaging, which includes the steps of: detecting a radio frequency pulse signal transmitted by a transmitting coil of a magnetic resonance imaging system; and feedback-controlling the radio-frequency pulse signal input to the transmitting coil based on the detected radio-frequency pulse signal.
Exemplary embodiments of the present invention also provide a magnetic resonance imaging system comprising the above radio frequency system.
Other features and aspects will become apparent from the following detailed description, the accompanying drawings, and the claims.
Drawings
The invention may be better understood by describing exemplary embodiments thereof in conjunction with the following drawings, in which:
figure 1 is a schematic block diagram of a magnetic resonance imaging system of one embodiment of the invention;
figure 2 is a schematic block diagram of the radio frequency system and receiver connection of a magnetic resonance imaging system according to an embodiment of the present invention;
figure 3 is a schematic block diagram of the radio frequency system and receiver connection of a magnetic resonance imaging system according to another embodiment of the present invention;
figure 4 is a schematic block diagram of the radio frequency system and receiver connection of a magnetic resonance imaging system according to another embodiment of the present invention;
figure 5 is a schematic block diagram of the radio frequency system and receiver connection of a magnetic resonance imaging system according to another embodiment of the present invention;
FIG. 6 is a flow chart of a RF control method for MRI according to an embodiment of the present invention;
fig. 7 is a schematic flow chart of the rf pulse signal input to the transmitting coil based on the detected rf pulse signal feedback control of the rf control method for magnetic resonance imaging according to an embodiment of the present invention;
fig. 8 is a flowchart illustrating a radio frequency pulse signal feedback control of the rf pulse signal input to the transmitting coil based on the detected rf pulse signal in the rf control method for magnetic resonance imaging according to another embodiment of the present invention.
Detailed Description
While specific embodiments of the invention will be described below, it should be noted that in the course of the detailed description of these embodiments, in order to provide a concise and concise description, all features of an actual implementation may not be described in detail. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions are made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another.
Unless otherwise defined, technical or scientific terms used in the claims and the specification should have the ordinary meaning as understood by those of ordinary skill in the art to which the invention belongs. The use of the words "a" or "an" and the like in the description and claims of the present patent application do not denote a limitation of quantity, but rather denote the presence of at least one. The word "comprise" or "comprises", and the like, means that the element or item listed before "comprises" or "comprising" covers the element or item listed after "comprising" or "comprises" and its equivalent, and does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, nor are they restricted to direct or indirect connections. "coupled" may include various means of magnetic coupling, electrical coupling, electromagnetic coupling, and the like.
Figure 1 shows a schematic block diagram of a magnetic resonance imaging system according to an embodiment of the invention. As shown in fig. 1, the magnetic resonance imaging system 10 includes a radio frequency system 11, a gradient system 12, a control system 13, and a main magnet 14. The hollow portion of the main magnet 14 forms a scanning bore 141, and a carrying bed for carrying the examination object 15 can enter the scanning bore 141 to perform magnetic resonance imaging on the examination object 15 to be scanned. The test object 15 may include a human body or other object to be scanned. The static magnetic field generated by the main magnet 14 causes a longitudinal macroscopic magnetization vector of the examination object 15 located in the scanning bore.
The radio frequency system 11 is configured to transmit radio frequency pulses to cause the magnetized protons in the test object 15 to absorb energy to generate resonance, and to generate and receive magnetic resonance signals during relaxation. The radio frequency system 11 comprises a radio frequency generator 111 and a transmitting coil 112 connected to the radio frequency generator 111.
The gradient system 12 may include gradient coils 121, 122, 123 and a gradient controller 124 respectively arranged in different directions (e.g., up-down, left-right, front-back directions of a human body, a Z-axis, an X-axis, and a Y-axis corresponding to reconstructed coordinates). The gradient controller 124 is used to transmit gradient pulses to the gradient coils 121, 122, 123 to linearly superimpose gradient fields on the static magnetic field to achieve spatial localization of the magnetic resonance signals so that a magnetic resonance image of any slice or volume is produced.
The control system 13 is configured to generate a pulse control sequence, which is sent to the radio frequency generator 111 and the gradient controller 124 via the sequencer 16, so that the radio frequency generator 111 and the gradient controller 124 respectively execute the radio frequency timing and the gradient timing in the pulse control sequence, and acquire magnetic resonance signals at specific time intervals of the timing to perform image reconstruction based on the acquired magnetic resonance signals.
Fig. 2 is a block diagram of a connection between a radio frequency system and a receiver of a magnetic resonance imaging system according to an embodiment of the invention. The radio frequency system 11 comprises a radio frequency generator 111, a power amplifier 114 connected to said radio frequency generator 111, and a transmit coil 112 connected to said power amplifier 114, for example by a transmit/receive switch 115. The radio frequency system 11 further comprises radio frequency detection means electromagnetically coupled to the transmission coil 112.
The transmitting coil 112 may include a large volume body coil and a small volume surface coil, wherein the body coil may be used as the transmitting coil, and the surface coil may be used as the radio frequency receiving coil, and wherein the transmitting coil 112 may also be used as the receiving coil to operate in the receiving mode.
The radio frequency generator 111 is configured to generate a radio frequency pulse signal, and to transmit the radio frequency pulse signal to the detection object 15 to be scanned after being received by the transmission coil 112, so as to excite hydrogen nuclei in the detection object 15 to generate a magnetic resonance signal. The radio frequency pulse signal emitted by the radio frequency generator 111 may generate a radio frequency field for exciting the longitudinal magnetization vector of the detected object 15 to be scanned to flip, thereby generating a transverse magnetization vector. After the excitation of the radio frequency pulse is finished, the transverse magnetization vector performs spiral attenuation around the external magnetic field at a fixed angular frequency to generate a free induction attenuation signal. The transmit coil 112 may generate magnetic resonance signals for imaging a subject by acquiring and analyzing the free induction decay signals. Typically, the rf generator 111 is used to transmit rf pulse signals with low power.
The power amplifier 114 is used for receiving the low-power rf pulse signal generated by the rf generator 111, performing amplification processing, and then outputting the amplified rf pulse signal. The power amplifier 114 may perform a series of processing such as analog-to-digital conversion or digital-to-analog conversion, modulation amplification, filtering processing, and the like on the received radio frequency pulse signal to output a high-power radio frequency pulse signal, so as to meet the imaging requirement of the magnetic resonance imaging system.
The transmit coil 112 may be connected to the power amplifier 114 through the transmit/receive switch 115. The transmit coil 112 may also be operated in a receive mode, i.e., may be switched between two different operating modes, transmit and receive, by controlling the transmit/receive switch 115.
The transmit coil 112 may receive the amplified rf pulse signal output by the power amplifier 114 in a transmit mode of operation and transmit the received rf pulse signal to the scan volume 141 of the mri system 10 to generate an rf field. The transmit coil 112 may receive magnetic resonance signals generated by the magnetic resonance imaging system in a receive mode of operation and transmit the magnetic resonance signals to the preamplifier 22 of the magnetic resonance imaging system 10 through the transmit/receive switch 115. The preamplifier 22 amplifies the received magnetic resonance signal and feeds it back to a receiver 23 of the magnetic resonance imaging system 10. The receiver 23 may perform image reconstruction based on the received magnetic resonance signals to form a scan image of the examination object 15.
The radio frequency detection component may be configured to detect a radio frequency pulse signal transmitted to the test object when the transmit coil 112 is in the transmit mode of operation. In other words, the rf detecting component can be used to detect the rf pulse signal actually transmitted by the transmitting coil 112 for generating the rf field, and the rf pulse signal detected by the rf detecting component can be used to feedback control the rf pulse signal input to the transmitting coil 112. For example, the rf detection component may feed back the received rf pulse signal to the rf generator 111 or the power amplifier 114 of the rf system 11 as a feedback control signal.
In one embodiment of the present invention, the radio frequency detection component includes a radio frequency detection antenna 21 that is electromagnetically coupled to the radio frequency system 11. The radio frequency detection antenna 21 may be disposed within a scan room 100 in which the magnetic resonance imaging system 10 is disposed. The radio frequency detection antenna 21 may be disposed at any suitable location within the scan room 100 of the magnetic resonance imaging system 10 as long as it can detect the radio frequency pulse signal transmitted to the static magnetic field. In other words, the radio frequency detection antenna 21 may be provided at a suitable position where the radio frequency pulse signal emitted to the detection object can be detected. In one embodiment of the present invention, the rf detecting antenna 21 is disposed at a position capable of detecting the rf pulse signal transmitted to the detected object when the transmitting coil 112 is in the transmitting operation mode.
In some embodiments of the present invention, the radio frequency detection antenna 21 may be disposed on the magnetic resonance imaging device disposed in the scanning room 100, or may be disposed on a wall of the scanning room 100, or may be disposed on other devices or other locations in the scanning room 100. Generally, in order to better detect and receive the rf pulse signals transmitted from the transmitting coil 112 to the detected object, the rf detecting antenna 21 is generally disposed on or near the mri apparatus disposed in the scan room 100. The magnetic resonance imaging device may comprise components such as the above-mentioned main magnet, transmit coils, gradient coils and coil housings, main magnet housing, a carrying bed for examination of the object, etc.
In particular, the radio frequency detection antenna 21 may be disposed at a different location of the magnetic resonance imaging device, for example, the radio frequency detection antenna 21 may be disposed on a housing of the main magnet 14 of the magnetic resonance imaging device, or the radio frequency detection antenna 21 may be disposed on a housing of the transmitting coil 112 of the magnetic resonance imaging system 10, or the radio frequency detection antenna 21 may be disposed in the scanning bore 141 of the magnetic resonance imaging system. Referring also to fig. 1, in one embodiment of the present invention, the rf detecting antenna 21 may be disposed in the scanning bore 141 of the mri system 10.
The rf detection antenna 21 may be connected to the rf generator 111 by a cable, wire or communication cable. The rf detection antenna 21 may feed back the detected and received rf pulse signal transmitted to the detection object to the rf generator 111 as a feedback control signal. The rf generator 111 may control the rf pulse signal generated by the rf detection antenna 21 based on the rf pulse signal fed back from the rf detection antenna. For example, the rf generator 111 may compare the rf pulse signal fed back from the rf detecting antenna 21 with the rf pulse signal generated by the rf detecting antenna to adjust the voltage of the rf pulse signal generated by the rf detecting antenna for power control, so that the rf pulse signal input to the transmitting coil has proper power along the whole rf link.
The detected and received rf pulse signal is fed back to the rf generator 111 through the rf detecting antenna 21, so that a closed-loop control circuit can be formed between the rf generator 111 and the transmitting coil 112. In other words, by providing the radio frequency detection antenna 21, the radio frequency pulse signal actually transmitted to the static magnetic field of the magnetic resonance imaging system can be fed back to the radio frequency generator 111 as a control signal, so that a closed-loop control link from the radio frequency pulse signal generation terminal to the radio frequency pulse signal transmission terminal can be formed. The rf generator 111 may dynamically adjust its output power according to the received feedback signal, that is, the transmit power of the rf generator 111 may be adjusted according to the weight of the detected object to be scanned and the actual receiving condition of the rf pulse signal.
Furthermore, by setting the radio frequency detection antenna 21 to form a closed-loop control circuit from the radio frequency pulse signal generation end to the radio frequency pulse signal transmission end, the radio frequency pulse signal actually transmitted to the static magnetic field of the magnetic resonance imaging system can be used as a feedback control signal, so as to adjust the gain or phase of the magnetic resonance imaging radio frequency pulse signal chain. In other words, the radio frequency system 20 of the present invention can improve the fidelity of the whole radio frequency signal chain from the radio frequency pulse signal generating end to the radio frequency pulse signal transmitting end in the magnetic resonance imaging. Therefore, the scanning image quality of the magnetic resonance imaging system can be improved.
Fig. 3 is a schematic block diagram of a connection between a radio frequency system and a receiver of a magnetic resonance imaging system according to another embodiment of the present invention. The radio frequency system 31 for magnetic resonance imaging shown in fig. 3 is substantially similar in composition, structure, and operation to the radio frequency system 11 for magnetic resonance imaging shown in fig. 2. The radio frequency system 31 also comprises a radio frequency generator 311, a power amplifier 314 connected to said radio frequency generator 311, a transmit coil 312 connected to said power amplifier 314 via a transmit/receive switch 315. The radio frequency system 31 further comprises radio frequency detection means electromagnetically coupled to the transmission coil 312. The radio frequency detection component may also include a radio frequency detection antenna 32.
The transmit coil 312 may be connected to the power amplifier 314 through the transmit/receive switch 315. The transmit coil 312 may also be operated in a receive mode by controlling the transmit/receive switch 315, i.e., the transmit coil 312 may be switched between two different operating modes, transmit and receive.
The transmit coil 312 may receive the amplified rf pulse signal output by the power amplifier 314 and transmit the received rf pulse signal to the scan bore 141 of the mri system 10 to generate an rf field in a transmit mode of operation. The transmit coil 312 may receive magnetic resonance signals generated by magnetic resonance in a receive mode of operation and transmit the magnetic resonance signals to the preamplifier 33 of the magnetic resonance imaging system 10 via the transmit/receive switch 315. The preamplifier 33 amplifies the received magnetic resonance signal and feeds it back to the receiver 34 of the magnetic resonance imaging system. The receiver 34 may perform image reconstruction based on the received magnetic resonance signals to form a scan image of the examination subject.
Since the composition, structure and operation principle of the rf system 31 shown in fig. 3 are substantially the same as those of the rf system 11 shown in fig. 2, the description thereof is omitted here.
The rf system 31 shown in fig. 3 differs from the rf system 11 shown in fig. 2 in that the rf detection component, i.e. the rf detection antenna 32, is connected to the power amplifier 314. The radio frequency detection antenna 32 may be used to detect the pulsed signal actually transmitted by the transmit coil 312 for generating the radio frequency field. The rf pulse signal detected by the rf detecting antenna 32 can be used to feedback control the rf pulse signal input to the transmitting coil 312. For example, the rf detection antenna 32 may feed back the received rf pulse signal to the power amplifier 314 as a feedback control signal. The power amplifier 314 can amplify the rf pulse signal received from the rf generator 311 based on the rf pulse signal fed back from the rf detecting antenna 32, so that the rf pulse signal input to the transmitting coil 312 has a proper power along the whole rf link.
The detected and received rf pulse signal is fed back to the power amplifier 314 through the rf detection antenna 32, so that a closed loop control circuit of the rf signal chain can be formed between the power amplifier 314 and the transmitting coil 312. In other words, the radio frequency pulse signal actually transmitted to the static magnetic field of the magnetic resonance imaging system can be fed back to the power amplifier 314 by the radio frequency detection antenna 32, and the power amplifier 314 amplifies the radio frequency pulse signal received from the radio frequency generator 311 based on the radio frequency pulse signal fed back by the radio frequency detection antenna 32, so that a closed loop radio frequency control link from the power amplifier 314 to the transmission coil 312 can be formed. The power amplifier 314 may dynamically adjust the rf pulse signal output by the power amplifier 312 according to the rf pulse signal fed back by the rf detection antenna 32, in other words, the rf pulse signal output by the power amplifier 312 may be amplified based on the rf pulse signal fed back by the rf detection antenna 32, so that the rf pulse signal input to the transmitting coil 312 has proper power.
The rf system 31 may use the rf pulse signal actually transmitted to the static magnetic field of the mri system as the feedback control signal of the power amplifier 314 through the rf detection antenna 32 to adjust the gain or phase of the rf pulse signal chain. In other words, the radio frequency system 30 of the present invention can also control the fidelity of the mri radio frequency signal chain, thereby improving the scan image quality of the mri system.
Fig. 4 is a schematic block diagram of a connection between a radio frequency system and a receiver of a magnetic resonance imaging system according to another embodiment of the present invention. The rf system 41 shown in fig. 4 is substantially similar in composition and structure to the rf system shown in fig. 2 or 3. The radio frequency system 41 also comprises a radio frequency generator 411, a power amplifier 414 connected to said radio frequency generator 411, and a transmitting coil 412 connected to said power amplifier 414, for example by means of a transmit/receive switch 415. The radio frequency system 41 further includes a radio frequency detection component electromagnetically coupled to the transmit coil 412. The transmit coil 412 may also be in a receive mode of operation by controlling the transmit/receive switch 415. In other words, the transmit coil 412 may be switched between two different operating modes, transmit and receive.
The transmit coil 412 may receive the amplified rf pulse signal output by the power amplifier 414 and transmit the received rf pulse signal to the scan bore 141 of the mri system 10 to generate an rf field in a transmit mode of operation. The transmit coil 412 may receive magnetic resonance signals generated by magnetic resonance in a receive mode of operation and transmit the magnetic resonance signals through the transmit/receive switch 415 to the preamplifier 43 of the magnetic resonance imaging system 10. The preamplifier 43 amplifies the received magnetic resonance signal and feeds it back to the receiver 44 of the magnetic resonance imaging system. The receiver 44 may perform image reconstruction based on the received magnetic resonance signals to form a scan image of the examination subject.
The structure, composition and operation principle of the rf system 41 shown in fig. 4 are similar to those of the rf systems shown in fig. 2 or fig. 3, and are not described herein again.
The radio frequency system 41 shown in fig. 4 differs from the radio frequency system shown in fig. 2 or 3 in that the radio frequency detecting means includes a surface coil 42 for detecting a radio frequency pulse signal actually transmitted to the test object by the transmitting coil 412. Referring also to fig. 1, the surface coils 42 may be placed directly within the static magnetic field of the magnetic resonance imaging system 10 and may be placed directly at the location or organ of the subject to be scanned.
The surface coil 42 may be connected to a receiving end of a receiver 44 of the magnetic resonance imaging system 10 by a cable, wire or communication cable. The output of the receiver 44 may be connected to the rf generator 411 through a cable, a wire or a communication cable, so that the signal transmission between the receiver 44 and the rf generator 411 is possible. The surface coil 42 is electromagnetically coupled to the transmitting coil 412, and is operable to detect and receive the rf pulse signal transmitted from the transmitting coil 412 to the subject, and transmit the rf pulse signal to the receiver 44. The receiver 44 may transmit the received rf pulse signal to the rf generator 411 as a feedback control signal of the rf generator 411. The rf generator 411 may control the rf pulse signal generated by the rf generator based on the rf pulse signal fed back from the surface coil 42, for example, the rf generator 411 may compare the rf pulse signal fed back from the surface coil 42 with the rf pulse signal generated by the rf generator to adjust the voltage of the rf pulse signal generated by the rf generator to perform power control, so that the rf pulse signal input to the transmitting coil 412 has proper power along the whole rf link.
Further, when the transmit coil 412 is switched to a transmit state by the transmit/receive switch 415, the transmit coil 412 may transmit the radio frequency pulse signal received from the power amplifier 414 to the static magnetic field of the magnetic resonance imaging system, thereby establishing a radio frequency field. During the process of transmitting the rf pulse signal by the transmitting coil 412, the surface coil 42 is in a detuned state, and can detect and receive the rf pulse signal transmitted by the transmitting coil 412, and then feed back to the rf generator 411 through the receiver 44.
The surface coil 42 may feed back its received radio frequency pulse signal to the radio frequency generator 411 as its feedback control signal through the receiver 44 of the magnetic resonance imaging system 10, thereby establishing a closed loop control circuit of the magnetic resonance imaging radio frequency signal chain from the radio frequency generator 411 to the transmit coil 412. The rf generator 411 may compare the rf pulse signal fed back from the surface coil 42 with the rf pulse signal generated by the surface coil to adjust the voltage of the rf pulse signal generated by the surface coil for power control, so as to make the rf pulse signal input to the transmitting coil 412 have proper power along the whole rf link.
Further, the rf pulse signal actually transmitted to the static magnetic field of the mri system by the transmitting coil 412 received by the surface coil 42 is fed back to the rf generator 411, and the rf generator 411 compares the rf pulse signal fed back by the surface coil 42 with the rf pulse signal generated by the rf pulse signal to perform power adjustment, so as to adjust the gain or phase of the mri rf pulse signal chain accordingly. In other words, the rf system 41 of the present invention can improve the fidelity of the whole rf signal chain from the rf pulse signal generating end to the rf pulse signal transmitting end of the mri system. Therefore, the scanning image quality of the magnetic resonance imaging system can be improved.
In addition, the invention directly receives the radio frequency pulse signal transmitted to the static magnetic field by the transmitting coil 412 through the surface coil 42 without arranging other components, thereby saving the manufacturing cost of the whole magnetic resonance system.
Fig. 5 is a schematic block diagram of the connection between the radio frequency system and the receiver of the magnetic resonance imaging system according to another embodiment of the present invention. The radio frequency system 51 shown in fig. 5 is substantially the same in composition and structure as the radio frequency system shown in fig. 4. The radio frequency system 51 also comprises a radio frequency generator 511, a power amplifier 514 connected to said radio frequency generator 511, a transmit coil 512 connectable to said power amplifier 514 via, for example, a transmit/receive switch 515. The radio frequency system 51 further comprises radio frequency detection components electromagnetically coupled to the transmit coil 512, the radio frequency detection components including a surface coil 52. The transmit coil 512 can be switched between two different operating modes, transmit and receive, by controlling the transmit/receive switch 515.
The transmit coil 512 may receive the amplified rf pulse signal output by the power amplifier 514 during a transmit mode of operation and transmit the received rf pulse signal to the scan volume 141 of the mri system 10 to generate an rf field. The transmit coil 512 may receive magnetic resonance signals generated by magnetic resonance in a receive mode of operation and transmit the magnetic resonance signals to the preamplifier 53 of the magnetic resonance imaging system 10 via the transmit/receive switch 515. The preamplifier 53 amplifies the received magnetic resonance signal and feeds it back to a receiver 54 of the magnetic resonance imaging system. The receiver 54 may perform image reconstruction based on the received magnetic resonance signals to form a scan image of the examination subject.
The structure, composition and operation principle of the rf system 51 shown in fig. 5 are similar to those of the rf system shown in fig. 4, and are not described herein again.
The radio frequency system shown in fig. 5 is different from the radio frequency system shown in fig. 4 in that the surface coil 52 is connected to a receiving end of the receiver 54, and an output end of the receiver 54 is connected to the power amplifier 514 through a cable, a wire, or a communication cable, whereby signal transmission between the receiver 54 and the power amplifier 514 is possible. In other words, the surface coil 52 feeds back the radio frequency pulse signal transmitted by the transmitting coil 512, which it receives, to the power amplifier 514 through the receiver 54.
The surface coil 52 is electromagnetically coupled to the transmitting coil 512, and can be used for detecting and receiving the radio frequency pulse signal transmitted from the transmitting coil 512 to the detected object, and transmitting the radio frequency pulse signal to the receiver 54. The receiver 54 may transmit the received rf pulse signal to the power amplifier 514 as a feedback control signal for the power amplifier 514. The power amplifier 514 can amplify the rf pulse signal received from the rf generator 514 based on the rf pulse signal fed back from the surface coil 52, so that the rf pulse signal input to the transmitting coil 512 along the rf link has a suitable power.
The surface coil 52 feeds back the rf pulse signal it receives to the power amplifier 514 through the receiver 54 as its feedback control signal, thereby establishing a closed loop control circuit of the rf signal chain from the power amplifier 514 to the transmit coil 512.
Further, the rf pulse signal actually transmitted to the static magnetic field of the magnetic resonance imaging system is transmitted to the power amplifier 514 by the surface coil 52 as a feedback control signal, and the power amplifier 514 may amplify the rf pulse signal received from the rf generator 511 based on the rf pulse signal fed back by the surface coil 52, so as to adjust the gain or phase of the rf pulse signal chain for magnetic resonance imaging accordingly. In other words, the rf system 51 of the present invention forms a closed loop control circuit from the power amplifier 514 to the transmitting coil 512 through the surface coil 52, and the fidelity of the rf signal chain of the mri system can be further improved through the closed loop control circuit. Therefore, the scanning image quality of the magnetic resonance imaging system can be improved.
The radio frequency system detects and receives the radio frequency pulse signal transmitted to a detection object by the transmitting coil of the radio frequency system through the radio frequency detecting antenna or the surface coil, and feeds the received radio frequency pulse signal back to the radio frequency generator or the power amplifier to be used as a feedback control signal, so that closed-loop control is performed. The radio frequency system can improve the fidelity of the whole radio frequency signal chain of the magnetic resonance imaging system, thereby improving the scanning image quality of the magnetic resonance imaging system.
In addition, the radio frequency system of the invention utilizes the existing radio frequency signal chain to form closed-loop control from the sending end of the radio frequency pulse signal to the sending end of the radio frequency pulse signal, thereby saving a large number of components and correspondingly saving the occupied space of the magnetic resonance imaging system. Moreover, the radio frequency system of the invention has simple design, and the manufacturing cost of the magnetic resonance imaging system is reduced by arranging the radio frequency detection antenna or utilizing the existing surface coil to detect and receive the radio frequency pulse signal transmitted by the transmitting coil. In addition, by transmitting the radio frequency pulse signal actually transmitted to the static magnetic field to the radio frequency generator or the power amplifier as a feedback control signal, power adjustment can be performed dynamically according to the conditions of the changing body weight of the scanning object, the loss of the radio frequency pulse signal link, and the like, a pulse signal satisfying the establishment of the radio frequency field can be generated better, and the radio frequency signal link can be compensated appropriately to satisfy the requirement of the establishment of the radio frequency field.
Referring also to fig. 1, a magnetic resonance imaging system 10 of the present invention includes the rf system of the above-mentioned embodiment. The magnetic resonance imaging system 10 of the embodiment of the present invention can well control the fidelity of the radio frequency signal chain because it uses the radio frequency system with the above-mentioned features. The magnetic resonance imaging system 10 of the present invention can be better dynamically adjusted according to the changing weight of the detected object, the loss of the radio frequency pulse signal link, etc., can better generate the pulse signal satisfying the establishment of the radio frequency field, and properly compensate the radio frequency signal link to satisfy the requirement of the establishment of the radio frequency field. Thus, the magnetic resonance imaging system 10 of the present invention can improve the quality of the scanned image, resulting in an image with a better signal-to-noise ratio.
Referring to fig. 6, a flow chart of a method 60 for rf control in mri according to an embodiment of the present invention is shown. As shown in fig. 6, the rf control method 60 includes the following steps:
in step 61, radio frequency pulse signals transmitted by a transmit coil of a magnetic resonance imaging system are detected. In one embodiment of the invention, in step 61, the radio frequency pulse signal transmitted by the transmit coil of the magnetic resonance imaging system may be detected by a radio frequency detection component electromagnetically coupled to the transmit coil of the radio frequency system. The radio frequency detection means may comprise a radio frequency detection antenna or a surface coil. In step 61, the configuration, connection relationship, setting position, working principle, etc. of the rf detecting antenna are similar to those of the rf detecting antenna of the rf system discussed above in the present invention, and are not described herein again. The surface coil is similar to the surface coil of the rf system discussed above in terms of structure, connection relationship, installation position, operation principle, etc., and will not be described herein again.
In step 62, the radio frequency pulse signal input to the transmitting coil is feedback controlled based on the detected radio frequency pulse signal.
Referring to fig. 6 and 7, in one embodiment of the present invention, step 62: the feedback control of the radio frequency pulse signal input to the transmitting coil based on the detected radio frequency pulse signal further comprises the steps of:
in step 621, feeding back the detected radio frequency pulse signal to a radio frequency generator of a magnetic resonance imaging system;
in step 622, the rf generator adjusts the power of the rf pulse signal generated by the rf generator based on the fed-back rf detection signal.
In step 621, the detected rf pulse signal may be fed back to the rf generator of the magnetic resonance imaging system through the rf detection antenna directly connected to the rf generator, or the detected rf pulse signal may be fed back to the rf generator of the magnetic resonance imaging system through the receiver of the magnetic resonance imaging system through the surface coil.
In step 622, the rf generator may adjust the power of the rf pulse signal generated by the rf generator based on the rf detection signal fed back from the rf detection antenna or the surface coil. In step 622, the rf generator may compare the rf detection signal fed back from the rf detection antenna or the surface coil with the rf pulse signal generated by the rf detection antenna or the surface coil to adjust the voltage of the rf pulse signal generated by the rf detection antenna or the surface coil for power control, so as to make the rf pulse signal input to the transmitting coil have a proper power along the whole rf link.
Further, the radio frequency control method of the present invention may feed back the received radio frequency pulse signal to the radio frequency generator through a radio frequency detection antenna or a surface coil electromagnetically coupled to the transmitting coil, so that a closed loop control circuit from the radio frequency generator to the transmitting coil may be formed. Therefore, the radio frequency control method of the invention can dynamically adjust the power of the radio frequency pulse signal generated by the radio frequency generator according to the received radio frequency detection signal fed back by the radio frequency generator, namely, the transmission power of the radio frequency generator can be dynamically adjusted according to the weight of the detected object to be scanned and the actually received radio frequency pulse signal, so that the radio frequency pulse signal input to the transmission coil has proper power.
Referring now to fig. 6 in conjunction with fig. 8, in another embodiment of the present invention, step 72: the feedback control of the rf pulse signal input to the transmitting coil based on the detected rf pulse signal may further include the steps of:
feeding back the detected radio frequency pulse signal to a power amplifier of a magnetic resonance imaging system in step 721;
in step 722, the power amplifier amplifies the rf pulse signal received by the power amplifier from the rf generator of the mri system based on the fed back rf detection signal.
In step 721, in an embodiment of the present invention, the rf pulse signal transmitted by the transmitting coil may be detected by an rf detecting antenna directly connected to the power amplifier, and the rf detecting antenna feeds the detected rf pulse signal back to the power amplifier of the magnetic resonance imaging system. In another embodiment of the invention, the radio frequency pulse signal transmitted by the transmitting coil may be detected by a surface coil, which feeds back the detected radio frequency pulse signal to a power amplifier of the magnetic resonance imaging system through a receiver of the magnetic resonance imaging system.
In step 722, the power amplifier may amplify the received rf pulse signal from the rf generator of the mri system based on the rf detection signal fed back from the rf detection antenna or the surface coil, so that the rf pulse signal input to the transmitting coil has a proper power.
Further, the radio frequency control method of the present invention may detect the radio frequency pulse signal transmitted by the transmitting coil through the radio frequency detecting antenna or the surface coil, and feed back the detected and received radio frequency pulse signal to the power amplifier of the magnetic resonance imaging system, thereby forming a closed loop control circuit from the power amplifier to the transmitting coil. The closed-loop control circuit can feed back the radio frequency pulse signal actually transmitted by the transmitting coil to the power amplifier, so that the power amplifier can amplify the received radio frequency pulse signal based on the fed-back radio frequency detection signal, the fidelity of a radio frequency signal chain of the magnetic resonance imaging system can be improved, and the scanning image quality of the magnetic resonance imaging system can be improved.
The radio frequency control method of the magnetic resonance imaging detects the radio frequency pulse signal transmitted to the detection object by the transmitting coil through the radio frequency detection antenna or the surface coil, and feeds back the received radio frequency pulse signal to the radio frequency generator or the power amplifier of the radio frequency system to be used as a feedback control signal. Therefore, a closed power control circuit of the magnetic resonance imaging system radio frequency signal chain can be formed, and the fidelity of the magnetic resonance imaging radio frequency signal chain can be better controlled. The radio frequency control method of the magnetic resonance imaging can dynamically adjust the power according to the conditions of the change weight of the detected object, the loss of a radio frequency pulse signal link and the like, can better generate a pulse signal meeting the requirement of establishing a radio frequency field, and properly compensates a radio frequency signal chain so as to meet the requirement of establishing the radio frequency field. Therefore, the radio frequency control method of the magnetic resonance imaging can improve the quality of the scanned image and generate an image with better signal-to-noise ratio.
Some exemplary embodiments have been described above, however, it should be understood that various modifications may be made. For example, suitable results may be achieved if the described techniques are performed in a different order and/or if components in the described systems, architectures, devices, or circuits are combined in a different manner and/or replaced or supplemented by additional components or their equivalents. Accordingly, other embodiments are within the scope of the following claims.
Claims (10)
1. A radio frequency system for magnetic resonance imaging, comprising:
a radio frequency generator for generating a radio frequency pulse signal;
the power amplifier is used for amplifying the radio frequency pulse signal and outputting the amplified radio frequency pulse signal;
a transmitting coil for receiving the amplified radio frequency pulse signal to transmit the radio frequency pulse signal to a detection object; and
and the radio frequency detection component is used for detecting the radio frequency pulse signal transmitted by the transmitting coil, and the radio frequency pulse signal detected by the radio frequency detection component is used for feedback control of the radio frequency pulse signal input to the transmitting coil.
2. The radio frequency system according to claim 1, wherein the radio frequency detection component is configured to feed back the detected radio frequency pulse signal to the radio frequency generator or the power amplifier, wherein the radio frequency generator adjusts the power of the radio frequency pulse signal generated by the radio frequency generator based on the radio frequency pulse signal fed back by the radio frequency detection component, or the power amplifier amplifies the radio frequency pulse signal received by the power amplifier from the radio frequency generator based on the radio frequency pulse signal fed back by the radio frequency detection component.
3. The radio frequency system of claim 2, wherein the radio frequency detection component comprises a radio frequency detection antenna disposed between scans in which the magnetic resonance imaging device is disposed and coupled to the transmit coil.
4. The radio frequency system of claim 3, wherein the radio frequency detection antenna is disposed on the magnetic resonance imaging device.
5. The radio frequency system of claim 2, wherein the radio frequency detection component comprises a surface coil for receiving the radio frequency pulse signal transmitted by the transmit coil and feeding the signal back to the radio frequency generator or the power amplifier through a receiver of a magnetic resonance imaging system.
6. The radio frequency system of claim 5, wherein the surface coil receives a radio frequency pulsed signal transmitted by the transmit coil when in a detuned state.
7. A magnetic resonance imaging system comprising a radio frequency system as claimed in any one of claims 1 to 6.
8. A radio frequency control method of magnetic resonance imaging, comprising the steps of:
detecting a radio frequency pulse signal transmitted by a transmitting coil of a magnetic resonance imaging system;
and feedback-controlling the radio-frequency pulse signal input to the transmitting coil based on the detected radio-frequency pulse signal.
9. The radio frequency control method of claim 8, wherein feedback controlling the radio frequency pulse signal input to the transmitting coil based on the detected radio frequency pulse signal comprises:
feeding back the detected radio frequency pulse signal to a radio frequency generator of a magnetic resonance imaging system;
the radio frequency generator adjusts the power of the radio frequency pulse signal generated by the radio frequency generator based on the fed back radio frequency detection signal.
10. The radio frequency control method of claim 8, wherein feedback controlling the radio frequency pulse signal input to the transmitting coil based on the detected radio frequency pulse signal comprises:
feeding back the detected radio frequency pulse signal to a power amplifier of a magnetic resonance imaging system;
the power amplifier amplifies the radio frequency pulse signal received by the power amplifier from the radio frequency generator of the magnetic resonance imaging system based on the fed back radio frequency detection signal.
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