Radio frequency coil assembly suitable for magnetic resonance system, magnetic resonance system and control method

Abstract

The invention relates to a radio frequency coil assembly suitable for a magnetic resonance system, the magnetic resonance system and a control method. The radio frequency coil assembly comprises a coil body formed by arranging a plurality of coil units, and the mode switching circuit is connected with at least one coil unit and used for controlling the coil unit to be switched from a transmitting mode to a receiving mode or from the receiving mode to the transmitting mode. The mode switching circuit is arranged between the radio frequency power amplifier and the coil unit, the pre-amplifier is used for amplifying magnetic resonance signals received by the coil unit, and the matching circuit is arranged between the mode switching circuit and the pre-amplifier and is used for realizing power matching between the radio frequency power amplifier and the coil unit or realizing noise matching between the coil unit and the pre-amplifier. By adopting the arrangement of the invention, the working mode of the radio frequency coil can be conveniently and quickly switched, and the radio frequency assembly and the receiving coil are used for receiving magnetic resonance signals to obtain richer acquisition information, so that the signal-to-noise ratio of a reconstructed image is improved.

Description

Technical Field

[0001] The present application relates to the technical field of medical devices, and particularly to a radio frequency coil assembly applicable to a magnetic resonance system, a magnetic resonance system, and a control method. Background Art

[0002] Nuclear magnetic resonance imaging (MRI) reconstructs internal structure images by detecting the energy release signals of hydrogen atomic nuclei (1H) in the human body in a strong magnetic field. Its core processes include nuclear precession, radio frequency pulse excitation, relaxation signal acquisition, and image reconstruction. Radio frequency coils are key components in MRI systems. They are used to receive and transmit radio frequency signals and have an important impact on the imaging quality. Radio frequency coils mainly include volume transmit coils and multi-channel receive coil arrays. In existing MRI applications, a volume transmit coil that generates a uniform field is used to excite the magnetic resonance signals in the target area, and a multi-channel receive coil is used to collect the excited signals. Especially as the magnetic field strength increases, in order to improve the uniformity of the transmit field, a multi-channel volume transmit coil is usually used. When collecting magnetic resonance signals, in order to avoid interference between channels, the transmit coil needs to be turned off, and the final MRI scan image is reconstructed from the signals collected by the receive coil. Although in some cases, a volume transmit-receive coil can be used for signal collection, due to factors such as its own size and efficiency, the signal-to-noise ratio of the signals received by the transmit coil is relatively low, and it can only be used as a reference image to correct the uniformity of the signals collected by the multi-channel receive coil.

[0003] Therefore, due to the influence of its own structure, the traditional transmit coil cannot truly participate in the collection of magnetic resonance signals. Summary of the Invention

[0004] Based on this, in view of the problem that the transmit coil cannot truly participate in the collection of magnetic resonance signals due to the influence of its own structure, it is necessary to provide a radio frequency coil assembly, a magnetic resonance system, and a control method that can not only be used for magnetic resonance signal excitation and brightness correction but also participate in the collection of magnetic resonance signals.

[0005] A radio frequency coil assembly applicable to a magnetic resonance system includes:

[0006] A coil body, which includes a plurality of coil units;

[0007] A mode switching circuit, connected to at least one coil unit, for controlling the coil unit to switch from a transmit mode to a receive mode, or from a receive mode to a transmit mode; the coil unit can generate radio frequency pulses in the transmit mode, and the coil unit can receive magnetic resonance signals in the receive mode;

[0008] A preamplifier for amplifying the magnetic resonance signals received by the coil unit;

[0009] A matching circuit is provided between the mode switching circuit and the preamplifier. When the coil unit is in the transmit mode, the matching circuit is used to achieve power matching between the RF power amplifier and the coil unit; when the coil unit is in the receive mode, the matching circuit is used to achieve noise matching between the coil unit and the preamplifier.

[0010] In one embodiment, each coil unit is connected to an RF power amplifier, and each RF power amplifier can independently control the amplitude and phase of the RF pulses generated by the corresponding coil unit.

[0011] In one embodiment, the mode switching circuit includes a first control loop and a second control loop. When the control current is turned on, the first control loop and the second control loop are turned on, and the coil unit switches from the receive mode to the transmit mode. When the control current is turned off, the first control loop and the second control loop are turned off, and the coil unit switches from the transmit mode to the receive mode.

[0012] In one embodiment, the coil unit has a loop structure, and a plurality of loop structures form a single-layer transmit array.

[0013] In another embodiment of the present application, a magnetic resonance system is provided, including:

[0014] A main magnet that surrounds to form a scanning cavity, and the main magnet is used to form a main magnetic field;

[0015] Gradient coils are provided inside the main magnet and are used to form a gradient field;

[0016] A body coil is provided inside the gradient coils, and the body coil can be switched to the transmit mode or the receive mode; the body coil includes:

[0017] A coil body that includes a plurality of coil units;

[0018] A mode switching circuit is connected to at least one coil unit and is used to control the coil unit to switch from the transmit mode to the receive mode, or from the receive mode to the transmit mode; the coil unit can generate RF pulses in the transmit mode and can receive magnetic resonance signals in the receive mode;

[0019] A preamplifier for amplifying the magnetic resonance signals received by the coil unit;

[0020] A matching circuit is provided between the mode switching circuit and the preamplifier. When the coil unit is in the transmit mode, the matching circuit is used to achieve power matching between the RF power amplifier and the coil unit; when the coil unit is in the receive mode, the matching circuit is used to achieve noise matching between the coil unit and the preamplifier.

[0021] In another embodiment, the present application provides a control method for a magnetic resonance system, where the magnetic resonance system includes: a surface coil for receiving magnetic resonance signals of a detection object; a body coil including a plurality of coil units;

[0022] The control method includes:

[0023] Controlling the coil units of the body coil to operate in a transmission mode to generate radio frequency pulses, which can excite nuclear spins in the detection object's body under the main magnetic field to generate magnetic resonance signals;

[0024] Controlling the coil units of the body coil to operate in a reception mode to obtain a first set of magnetic resonance signals, and controlling the surface coil to be in a resonant state to obtain a second set of magnetic resonance signals;

[0025] Obtaining a target image of the detection object based on the first set of magnetic resonance signals and the second set of magnetic resonance signals.

[0026] In one embodiment, the body coil further includes: a mode switching circuit connected to at least one coil unit for controlling the coil unit to switch from the transmission mode to the reception mode, or from the reception mode to the transmission mode; the coil unit can generate radio frequency pulses in the transmission mode and can receive magnetic resonance signals in the reception mode;

[0027] A preamplifier for amplifying the magnetic resonance signals received by the coil unit;

[0028] A matching circuit is provided between the mode switching circuit and the preamplifier. When the coil unit is in the transmission mode, the matching circuit is used to achieve power matching between the radio frequency power amplifier and the coil unit; when the coil unit is in the reception mode, the matching circuit is used to achieve noise matching between the coil unit and the preamplifier.

[0029] In one embodiment, the first set of magnetic resonance signals corresponds to multiple reception channels, and the second set of magnetic resonance signals corresponds to multiple reception channels;

[0030] Obtaining a target image of the detection object based on the first set of magnetic resonance signals and the second set of magnetic resonance signals includes:

[0031] Performing channel merging and reconstruction on the first set of magnetic resonance signals and the second set of magnetic resonance signals to obtain a target image of the detection object.

[0032] In one embodiment, the magnetic resonance system includes a scanner, the body coil is integrated inside the scanner; the surface coil is placed on the surface of the detection object.

[0033] In one embodiment, the undersampling acceleration factor of the magnetic resonance signal is determined according to the number of receiving channels corresponding to the first group of magnetic resonance signals and the number of receiving channels corresponding to the second group of magnetic resonance signals.

[0034] The above radio frequency coil assembly and magnetic resonance system, through the improvement of the traditional transmission link, enable the transmitting coil to switch between the transmission mode and the reception mode. After the transmitting coil completes the signal excitation, it can also receive the magnetic resonance signal, allowing the transmitting coil to truly participate in the acquisition of the magnetic resonance signal, and while solving the mutual interference between the transmitting coil and the receiving coil channels, enriching the collected signals / information. In the magnetic resonance imaging method corresponding to this radio frequency component, this solution uses the traditional transmitting coil as part of the entire multi-channel receiving coil array to collect magnetic resonance signals, and uses the magnetic resonance signals received by the transmitting coil and the receiving coil for image reconstruction. By using a larger number of receiving channels, the imaging acceleration performance and the signal-to-noise ratio and uniformity of the reconstructed image are improved. Description of the Drawings

[0035] Figure 1 Schematic diagram of the module circuit of the radio frequency coil assembly in one embodiment;

[0036] Figure 2 Schematic diagram of the control circuit of the radio frequency coil assembly in one embodiment;

[0037] Fig. 3(a) is a schematic diagram of a multi-channel loop structure;

[0038] Fig. 3(b) is an equivalent circuit diagram of a multi-channel loop;

[0039] Figure 4 Schematic diagram of a split multi-channel loop structure;

[0040] Figure 5 Schematic diagram of a magnetic resonance system in one embodiment;

[0041] Figure 6 Flowchart of the control method of the magnetic resonance system in one embodiment;

[0042] Figure 7 Flowchart of a method for combining coil channels;

[0043] Figure 8 Schematic diagram of the arrangement of the body coil and the surface coil in one embodiment;

[0044] Figure 9 Schematic diagram of the simulation result in one embodiment.

[0045] Description of the Reference Numerals:

[0046] 100. Coil unit;

[0047] 200. Mode switching circuit;

[0048] 300. Matching circuit;

[0049] 400. Preamplifier (AMP);

[0050] 500. Body coil; 510. Crosspiece portion; 520. End portion; 511. Crosspiece sub-unit; 522. End sub-unit;

[0051] 600. Surface coil;

[0052] 700. Main magnet. Detailed implementation manners

[0053] To make the above objects, features, and advantages of the present application more apparent and understandable, the following will describe the detailed implementation manners of the present application in conjunction with the accompanying drawings. Many specific details are set forth in the following description to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0054] In the description of the present application, it should be understood that if terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, the orientation or positional relationship indicated by these terms is based on the orientation or positional relationship shown in the accompanying drawings. These are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present application.

[0055] In addition, if terms such as "first" and "second" appear, these terms are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present application, if the term "plurality" appears, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0056] In this application, unless otherwise clearly defined and limited, if terms such as "installed", "connected", "linked", "fixed", etc. appear, these terms should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0057] In this application, unless otherwise clearly defined and limited, if there is a description such as a first feature being "on" or "under" a second feature, its meaning can be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over", and "on top of" the second feature can be that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is at a higher horizontal level than the second feature. The first feature being "under", "beneath", and "underneath" the second feature can be that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is at a lower horizontal level than the second feature.

[0058] It should be noted that if an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there can also be an intermediate element. If an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. If so, the terms "vertical", "horizontal", "up", "down", "left", "right", and similar expressions used in this application are only for the purpose of illustration and do not represent the only implementation.

[0059] Refer to Figure 1 , which is the module circuit of the radio frequency coil assembly in an embodiment of this application. This radio frequency assembly is applied in a magnetic resonance system and is used to cooperate with the magnetic resonance system to image a patient. The radio frequency coil assembly is composed of a coil body, a mode switching circuit, a preamplifier, and a matching circuit.

[0060] Specifically, the geometric shape of the coil body can be cylindrical, rectangular, saddle-shaped, or an irregular shape, etc., as long as it ensures sufficient signal reception coverage and transmission uniformity. The coil body includes a plurality of coil units 100, and the coil body is arranged by a plurality of coil units 100. These coil units 100 can be arranged adjacent to each other in the circumferential direction to form a cylindrical structure. Between each coil unit 100, they can be arranged with a common side, or overlapped, or separated. The material of the coil unit 100 can be copper skin or conducting wire, and the number of coil units 100 can be four, six, eight, sixteen, or more.

[0061] Each coil unit 100 is respectively connected with an RF power amplifier, and each RF power amplifier can independently control the amplitude and phase of the radio frequency pulses generated by the corresponding coil unit 100. Multiple coil units 100 can form a multi-channel loop structure, a multi-channel birdcage structure, a multi-channel transverse electromagnetic (TEM) structure, a multi-channel dipole structure, etc.

[0062] The mode switching circuit 200 is electrically connected to at least one coil unit 100 and is used to control the coil unit 100 to switch between the transmitting mode and the receiving mode. When the mode switching circuit 200 switches the coil unit 100 to the transmitting mode, the coil unit 100 can generate radio frequency pulses to excite signals in the region of interest. When the mode switching circuit 200 switches the coil unit 100 to the receiving mode, the coil unit 100 can receive magnetic resonance signals. When the mode switching circuit is connected to the matching circuit 300 and the coil unit 100 is in the transmitting mode, the matching circuit 300 is used to achieve power matching between the RF power amplifier and the coil unit 100; when the coil unit 100 is in the receiving mode, the matching circuit 300 is used to achieve noise matching between the coil unit 100 and the preamplifier 400. The matching circuit is connected to the preamplifier 400, that is, the matching circuit 300, which is arranged between the mode switching circuit 200 and the preamplifier 400, and the matching circuit 300 is used to amplify the magnetic resonance signals received by the coil unit 100. It can be understood that in the transmitting mode, the coil unit 100, the mode switching circuit 200 and the matching circuit 300 are connected in series to form a transmitting link. After the matching circuit 300 achieves signal power matching between the RF power amplifier and the coil unit 100, the radio frequency signals generated by the signal transmitter are sequentially passed through the matching circuit 300, the mode switching circuit 200 and the coil unit 100 to excite signals in the region of interest; in the receiving mode, the coil unit 100, the mode switching circuit 200, the matching circuit 300 and the preamplifier 400 are sequentially connected in series to form a receiving link. The matching circuit 300 matches the noise with the preamplifier 400. After the signal is received by the coil unit 100, it passes through the mode switching circuit 200, the matching circuit 300, the preamplifier 400 and finally reaches the signal receiver.

[0063] In this embodiment, the mode switching circuit 200 is used to control the RF components to switch between the transmitting mode and the receiving mode. The matching circuit 300 achieves impedance matching in different modes, and by setting the preamplifier 400 and adopting the preamplifier decoupling technology, it is ensured that there is no interference between each channel of the RF components in the receiving mode, improving the working efficiency and signal quality of the RF coil components.

[0064] Refer to Figure 2, which is a schematic structural diagram of the control circuit of a radio frequency coil assembly according to an embodiment of the present application. In one embodiment, each coil unit 100 is respectively connected to an RF power amplifier, and each RF power amplifier can independently control the amplitude and phase of the radio frequency pulse generated by the corresponding coil unit 100. In the figure, Loop represents a loop of the coil unit 100, and the TRcontrol terminal is the control signal terminal, and a DC control signal can be accessed through this control terminal. The TX terminal can be connected to the RF power amplifier. In this embodiment, each loop is connected to an RF power amplifier, and each RF power amplifier can independently control the amplitude and phase of the radio frequency pulse generated by the corresponding coil unit 100. The control circuit may include a mode switching circuit 200 (TR swith), a preamplifier 400 (AMP), and a matching circuit 300 (matching circuit).

[0065] Taking the example where Loop represents a loop of the coil unit 100, the coil unit 100 is connected to the mode switching circuit 200, and the TR control terminal of the mode switching circuit 200 is the control signal terminal, and a DC control signal can be accessed through this control terminal; a matching circuit 300 (matchingcircuit) is provided between the mode switching circuit 200 and the preamplifier 400 (AMP), and the output terminal of the preamplifier 400 (AMP) can be connected to the loop receiving port (RX) to output the received magnetic resonance signal in the loop receiving mode; the matching circuit 300 can also be connected to the loop power amplifier port (TX), and an external RF power amplifier can provide a radio frequency power source through this loop power amplifier port in the loop transmitting mode.

[0066] In another embodiment, the mode switching circuit includes a first control loop and a second control loop. When the control current is turned on, the first control loop and the second control loop are conducted, and the coil unit switches from the receiving mode to the transmitting mode. When the control current is turned off, the first control loop and the second control loop are turned off, and the coil unit switches from the transmitting mode to the receiving mode. Specifically, the mode switching circuit 200 includes a DC blocking unit composed of a capacitor C1; a first phase shift unit composed of an inductor L1, a capacitor C2, and a capacitor C3; a second phase shift unit composed of an inductor L3, a capacitor C5, and a capacitor C6, a first filtering unit composed of C9; a second filtering unit composed of C10. The first phase shift unit and the second phase shift unit are provided between the coil unit 100 and the matching circuit 300; the first filtering unit and the second filtering unit are provided between the control signal terminal and the matching circuit 300; the DC blocking unit is provided between the coil unit 100 and the matching circuit 300.

[0067] When a DC control signal is input to the control signal terminal, the DC control signal forms a first control loop in sequence through inductor L4, inductor L5, diode PIN1, inductor L6, diode PIN2 and then grounded; the DC control signal forms a second control loop in sequence through inductor L4, inductor L5, diode PIN1, inductor L6, diode PIN2, inductor L7, inductor L8, diode PIN3, inductor L2 and then grounded. When the first control loop and the second control loop are connected, the first phase-shifting unit, capacitor C4, diode PIN1, and capacitor C10 are grounded to form a high-impedance loop (open circuit), and the second phase-shifting unit, capacitor C7, and diode PIN2 are grounded to also form a high-impedance loop. At this time, the second control loop can make the mode switching circuit 200 switch to the transmitting state. At the same time, an external RF power amplifier is connected to the coil unit 100 through capacitor C11, diode PIN3, and capacitor C1 of the matching circuit 300, and the coil unit 100 is excited to generate a radio frequency pulse.

[0068] When there is no input at the control signal terminal, the mode switching circuit 200 is in the receiving state. The received magnetic resonance signal of the coil unit 100 passes through L1 of the first phase-shifting unit, the second phase-shifting unit 3, and C12 of the matching circuit 300 in sequence, and then reaches the loop receiving port after being amplified by the preamplifier.

[0069] Referring to FIG. 3(a), it is a schematic diagram of the radio frequency coil structure according to an embodiment of the present application. The coil body of the radio frequency coil includes a plurality of coil units 100, and the plurality of coil units 100 surround to form a multi-channel loop structure. Each coil unit 100 can be designed to have the same geometric size and electrical characteristics to ensure the uniformity of the electromagnetic field distribution of the entire coil body, or different geometric sizes can be set according to the characteristics of the imaging object. In this specific embodiment, the radio frequency coil includes a plurality of cross bars 510 and two end portions 520. The cross bars 510 are provided with cross-end antennas, and the end portions 520 are provided with end-loop antennas. The end portions 520 are arranged at both ends of the cross bars 510 and at both ends between adjacent two cross bars 510, and the cross bars 510 are respectively connected to the end portions 520 at both ends thereof. The plurality of cross bars 510 are arranged at intervals (preferably evenly spaced) along the circumferential direction of the radio frequency coil, and the cross bars 510 extend along the axial direction of the radio frequency coil. Among them, the cross bar 510 includes a plurality of cross bar sub-units 511 arranged adjacent to each other in sequence along the axial direction of the radio frequency coil. Adjacent two cross bar sub-units 511 are connected by a capacitor. Generally, the two adjacent cross bar sub-units 511 located at the middle position of the cross bar 510 are connected by a fixed capacitor, while between the two cross bar sub-units 210 close to the end portion 520 on the cross bar 510, or the cross bar sub-unit 511 on the cross bar 510 for connecting to the end portion 520, are all connected by an adjustable capacitor (that is, the capacitance value of the capacitor can be adjusted). With such a setting, the error of each fixed capacitor can be adjusted by the adjustable capacitor, so as to achieve accurate transmission frequency calibration. In addition, each end portion 520 includes a plurality of end sub-units 521, and the plurality of end sub-units 521 are arranged at intervals along the circumferential direction of the radio frequency coil, so as to form an annular end portion 520.

[0070] In this embodiment, two adjacent cross bars 510 and a plurality of end sub-units 521 located between these two cross bars 510 form a loop LOOP. It can be seen from this that the radio frequency coil includes a plurality of loops LOOP arranged along the circumferential direction, and the number of loops LOOP is equal to the number of cross bars 510 of the radio frequency coil. Further, it can be known that the number of feed ports in this embodiment is equal to the number of loops LOOP, that is, one feed port acts on one loop LOOP. Optionally, the position of the feed port can be set on the end portion 520. For example, in this embodiment, a plurality of feed ports are arranged at intervals along the circumferential direction of the radio frequency coil on the same end portion 520, that is, the feed ports are located on the end sub-units 521. As shown in FIG. 3(b), it is an equivalent circuit diagram of the radio frequency coil in FIG. 3(a). The current flow directions of the plurality of loops LOOP can be the same as each other or different from each other, specifically depending on the amplitude and phase of the supply current of each loop LOOP.

[0071] Further, two adjacent crossbar units 210 can be connected by a fixed capacitor or a tunable capacitor. In this embodiment, considering that the position accuracy between each loop LOOP is different when the radio frequency coil 20 is installed on the cylinder 10, and there are deviations in the fixed capacitors connected between the crossbar units 210, this embodiment preferably configures the connection between two adjacent crossbar units 210 through a tunable capacitor to adjust the resonant frequencies of different loops LOOP, so as to achieve precise adjustment of the resonant frequency of the radio frequency coil 20.

[0072] In another embodiment, the coil unit 100 can be wound into a separated multi-channel loop structure. Taking a volume transmit coil (VTC) as an example, the volume transmit coil is fixed around the scanning cavity inside the gradient coil and integrated in the magnet unit. When a patient lies on the examination bed and enters the magnet bore, the body is located inside the coil body, and the coil body can be used to transmit radio frequency pulses and receive magnetic resonance signals. As Figure 4 shown, the volume transmit coil is composed of multiple coil units 100, and these coil units 100 are arranged with gaps in the circumferential direction, and each coil unit can have a separate RF power amplifier. Additionally, in the axial direction of the scanning bore, multiple coil units 100 can also be arranged, and these coil units 100 are arranged with gaps and do not overlap each other. Such a design can effectively reduce the coupling interference between the coils, and each coil unit can independently receive signals, facilitating parallel imaging to improve the imaging speed.

[0073] The radio frequency coil assembly provided in this embodiment realizes the switching of the coil unit 100 between the transmit mode and the receive mode through the mode switching circuit 200, and realizes impedance or noise matching in different modes through the matching circuit 300, improving the working efficiency and signal quality of the radio frequency coil assembly.

[0074] This application also provides a magnetic resonance system, as Figure 5 shown, the magnetic resonance system includes the main magnet 700, the gradient coil, and the body coil 500.

[0075] The main magnet 700 surrounds to form a scanning cavity for accommodating a target scanning object. The main magnet 700 is used to form a main magnetic field and can be made of a superconducting magnet. A liquid helium cooling system is equipped outside it to maintain the superconducting coil working in the superconducting state. The gradient coil is arranged inside the main magnet 700 and is used to form a gradient field. The gradient coil includes an X-axis gradient coil, a Y-axis gradient coil, and a Z-axis gradient coil, which are respectively used to generate a linearly varying gradient magnetic field in the X, Y, and Z directions to locate the region of interest. The body coil 500 can be placed inside the gradient coil, and the body coil 500 can be switched to the transmit mode or the receive mode. Specifically, the body coil 500 includes a coil body, and the coil body includes a plurality of coil units 100. For example, the plurality of coil units 100 are arranged adjacent to each other in sequence along the circumference of the scanning cavity to form a cylindrical shape. At least one coil unit 100 is connected to the mode switching circuit 200. The mode switching circuit 200 can be used to control the coil unit 100 to switch from the transmit mode to the receive mode, or from the receive mode to the transmit mode. The coil unit 100 can generate radio frequency pulses in the transmit mode, and the coil unit 100 can receive magnetic resonance signals in the receive mode. A preamplifier 400 is provided to decouple between the coil units and amplify the magnetic resonance signals received by the coil unit 100. A matching circuit 300 is also provided between the mode switching circuit 200 and the preamplifier 400. When the coil unit 100 is in the transmit mode, the matching circuit 300 can achieve power matching between the radio frequency power amplifier and the coil unit 100. In the receive mode, the matching circuit 300 is used to achieve noise matching between the coil unit 100 and the preamplifier 400.

[0076] In this embodiment, the magnetic resonance system works in cooperation with the main magnet 700, gradient coils, and body coil 500. When transmitting signals, the gradient coils generate a specific gradient magnetic field according to the requirements of the imaging sequence. The body coil 500 enters the transmission mode under the control of the mode switching circuit 200, receives the radio frequency pulse signal generated by the radio frequency power amplifier, and converts the pulse signal into a radio frequency magnetic field and transmits it to the region of interest. When it is necessary to receive imaging data for image reconstruction, the mode switching circuit 200 is adjusted to make the body coil 500 in the receiving mode. The body coil 500 can receive the magnetic resonance signal together with the receiving coil, and the signal enters the preamplifier 400 for processing after passing through the receiving channel. By using the above body coil 500, richer magnetic resonance signals can be obtained, the channels for signal reception are increased, and high-quality magnetic resonance images can be obtained. The body coil can switch between the transmission mode and the receiving mode, can generate a uniform radio frequency magnetic field, and can sensitively receive magnetic resonance signals, improving the working efficiency and image quality of the system. It can be understood that the magnetic resonance system further includes a control system and an image reconstruction system. The control system is used to control the operation of the entire magnetic resonance system, including gradient field control, radio frequency pulse control, and data acquisition control. The image reconstruction system can be used to obtain a magnetic resonance image by performing Fourier transform on the received magnetic resonance signal. Specifically, the magnetic resonance signal for image reconstruction can be a fully sampled k-space data set or an undersampled k-space data set. For the undersampled k-space data, image reconstruction can be performed based on sensitivity encoding (SENSE), simultaneous acquisition of spatial harmonics (SMASH), generalized autocalibrating partially parallel acquisitions (GRAPPA), AUTO-SMASH, variable density AUTO-SMASH (VD-AUTO-SMASH), and compressed sensing method (CS). In addition, in order to improve the image reconstruction efficiency, parallel imaging techniques can be used to reconstruct the magnetic resonance signal, such as simultaneous acquisition of spatial harmonics (SMASH), sensitivity encoding parallel acquisition techniques (SENSE), and generalized autocalibrating partially parallel acquisitions (GRAPPA).

[0077] In this application, a control method for a resonance system is also provided, where the magnetic resonance system includes a surface coil 600 and a body coil 500 for receiving the magnetic resonance signal of a detection object. The body coil 500 includes a plurality of coil units 100 arranged along the circumferential direction. As Figure 6 shown, the control method includes the following steps:

[0078] Step S610: Control the coil unit 100 of the body coil 500 to operate in the transmission mode to generate radio frequency pulses, where the radio frequency pulses can excite nuclear spins in the object to be detected in the main magnetic field to generate magnetic resonance signals.

[0079] It can be understood that in this solution, the body coil 500 has two operating modes, namely the transmission mode and the reception mode. When the magnetic resonance system receives a scanning instruction, the coil unit 100 of the body coil 500 is controlled to operate in the transmission mode to generate radio frequency pulses, and the radio frequency pulses can excite nuclear spins in the object to be detected in the main magnetic field to generate magnetic resonance signals. Among them, the coil unit 100 can be circular, square or other shapes, and the body coil 500 composed of the coil unit 100 can be circular, rectangular or irregular in shape to adapt to different imaging requirements and human body parts. For example, multiple coil units 100 are sequentially spliced into a cylindrical body coil 500, and multiple adjacent coil units 100 can be overlapped to remove coupling, or adjustable capacitors can be set on the common side for decoupling. The body coil 500 can be a multi-channel coil and is arranged in the magnetic resonance imaging cavity. For a general magnetic resonance imaging system, the body coil 500 can be a birdcage coil, which can cover most parts of the human body, such as the head, chest, abdomen and limbs, etc. For a magnetic resonance system for imaging specific parts, such as a dedicated head magnetic resonance, the body coil 500 will be designed into a structure suitable for the shape of the head to fit the head more closely to improve the imaging resolution and signal-to-noise ratio. The radio frequency pulses can be set by comprehensively considering the imaging sequence, tissue characteristics of the region of interest, etc., and can selectively excite nuclear spins within a specific frequency range.

[0080] Step S620: Control the coil unit 100 of the body coil 500 to operate in the reception mode to obtain a first set of magnetic resonance signals, and control the surface coil 600 to be in a resonant state to obtain a second set of magnetic resonance signals.

[0081] After the radio frequency pulse excites the nuclear spins in the detection object to generate magnetic resonance signals, the body coil 500 is switched to the receiving mode, so that the body coil 500 and the surface coil 600 jointly receive the magnetic resonance signals. The coil unit of the body coil 100 is controlled to operate in the receiving mode to obtain the first set of magnetic resonance signals, and the surface coil 600 is controlled to be in the resonant state to obtain the second set of magnetic resonance signals. The surface coil 600 is specifically used to receive the magnetic resonance signals of the detection object. The surface coil 600 can be composed of multiple overlapping coil units, and is generally arranged on the surface of the region of interest in the scanning cavity. It can adopt a flexible design to fit the surface of the detection object, thereby improving the sensitivity of signal reception. When receiving the magnetic resonance signals, the surface coil 600 is adjusted to the resonant state through a tuning circuit, corresponding to the main magnetic field strength and the gyromagnetic ratio of the hydrogen nucleus. The signal acquisition methods of the body coil 500 and the surface coil 600 can be synchronous acquisition or delayed acquisition. Among them, synchronous acquisition means that when the surface coil 600 resonantly receives signals, the body coil 500 is also controlled to be in the receiving mode, that is, the two coils can receive signals simultaneously; in delayed acquisition, the body coil 500 is first controlled to the receiving mode, and after a period of time, the surface coil 600 is controlled to resonantly receive signals. By operating the acquisition of the surface coil 600 after the body coil 500 is in the receiving mode, the influence of the coil coupling between the body coil 500 and the surface coil 600 on the received signals can be reduced.

[0082] Step S630, obtain the target image of the detection object based on the first set of magnetic resonance signals and the second set of magnetic resonance signals.

[0083] After obtaining the first set of magnetic resonance signals collected by the body coil 500 and the second set of magnetic resonance signals collected by the surface coil 600, the two sets of magnetic resonance signals are used together for the reconstruction of the imaging image to obtain the target image. During reconstruction, the weight of the signals collected by each unit can be allocated according to the sensitivity of each coil unit 100 of the collected signals, which can improve the image uniformity of the final imaging. In this embodiment, the transmitting coil and the receiving coil are used to receive the magnetic resonance signals simultaneously, abandoning the traditional logic of mutually exclusive use of the transmitting coil and the receiving coil. The collected magnetic resonance signals not only come from the receiving coil, but the transmitting coil also plays a contributing role. Therefore, this method expands the number of channels of the receiving coil during acquisition, and the richness of the collected signals is also much higher than the traditional method, thereby improving the signal-to-noise ratio of the magnetic resonance image and the acceleration performance during image reconstruction.

[0084] In one embodiment, a mode switching circuit 200 is used to switch the operating mode of the coil unit 100 in the body coil 500. The control circuit of the coil unit 100 is divided into a transmitting link and a receiving link. When the operating mode is switched to the receiving mode, the receiving link is turned on and the transmitting link is turned off. When the operating mode is in the transmitting mode, the transmitting link is turned on and the receiving link is turned off. Specifically, the mode switching circuit 200 is connected to at least one coil unit 100 and is used to control the coil unit 100 to switch from the transmitting mode to the receiving mode, or from the receiving mode to the transmitting mode. The coil unit 100 can generate radio frequency pulses in the transmitting mode, and the coil unit 100 can receive magnetic resonance signals in the receiving mode. The mode switching circuit 200 is also connected to a matching circuit 300. When the coil unit 100 is in the transmitting mode, the matching circuit 300 is used to achieve power matching between the radio frequency power amplifier and the coil unit 100. When the coil unit 100 is in the receiving mode, the matching circuit 300 is used to achieve noise matching between the coil unit 100 and the preamplifier 400, where the preamplifier 400 is connected to the matching circuit.

[0085] With this setting, in the receiving mode, affected by the control current in the mode switching circuit 200 being turned on, the coil unit 100, the mode switching circuit 200, the matching circuit 300, and the preamplifier 400 are connected in series in sequence to form a receiving link. The signal received by the coil unit 100 passes through the mode switching circuit 200, the matching circuit 300, and the preamplifier 400 in sequence through the receiving channel and is then received by the signal receiver. In the transmitting mode, the coil unit 100, the mode switching circuit 200, and the matching circuit 300 are connected in series in sequence to form a transmitting link. The radio frequency pulses generated by the radio frequency amplifier reach the coil unit 100 after passing through the matching circuit 300 and the mode switching circuit 200. Through the above circuit design, the body coil 500 can be conveniently and quickly switched between the two operating modes, and the preamplifier decoupling technology for the receiving coil array is used in the receiving mode, which can effectively remove the mutual interference between multiple channels during signal reception.

[0086] In another embodiment, the first group of magnetic resonance signals obtained by the body coil 500 corresponds to multiple receiving channels, and the second group of magnetic resonance signals obtained by the surface coil 600 corresponds to multiple receiving channels. Obtaining a target image of the detection object based on the first group of magnetic resonance signals and the second group of magnetic resonance signals includes: performing channel merging and reconstruction on the first group of magnetic resonance signals and the second group of magnetic resonance signals to obtain a target image of the detection object. During reconstruction, allocating the weights of the signals collected by each channel according to the sensitivities of the respective coil units 100 of the collected signals can improve the image uniformity of the final imaging. The specific coil channel merging process is as Figure 7 shown and includes the following steps:

[0087] Step S710: The excitation coil 500 emits radio frequency pulses based on the imaging sequence to excite the target area of the subject, and uses the surface coil 600 and the body coil 500 to collect the magnetic resonance signals generated by the target area, and obtains the K-space data collected by multiple channels. Among them, both the surface coil 600 and the body coil 500 have multiple channels, and each channel has a corresponding coil sensitivity or noise parameter for the magnetic resonance signal.

[0088] Step S720: Perform Fourier transform on the K-space data to obtain the multi-channel images of the surface coil 600 and the body coil 500.

[0089] Exemplarily, the surface coil 600 includes M channels, the body coil 500 includes N channels, M+N K-spaces can be obtained through the filling of the phase encoding lines, and M+N images can be obtained through Fourier transform of the M+N K-spaces, where each image corresponds to a signal acquisition channel respectively. It should be noted that the "Fourier transform" involved in this application can also be called "inverse Fourier transform", which refers to the transformation from the K-space data domain to the image domain. The signal of the multi-channel image has the following relationship with the K-space data:

[0090]

[0091] Among them, represents the K-space data of the i-th channel at in the K-space, and the K-space data can be fully sampled, undersampled, or filtered; represents the image signal of the i-th channel at the image domain position (x, y).

[0092] Step S730: Calculate the characteristic parameters corresponding to each channel according to the multi-channel images.

[0093] Specifically, the characteristic parameters can be parameters that can reflect the contribution of each channel to the overall image, such as sensitivity and noise parameters. Taking the characteristic parameter as sensitivity as an example, calculate the sensitivity of the coil corresponding to each channel according to the multi-channel images. The sensitivities of the coils of multiple channels can form a sensitivity map of the coil, and the characteristic parameters of multiple channels can form a characteristic parameter map of the coil, that is, obtain the sensitivity of each channel coil according to the intensity of the frequency domain signal collected by each channel coil. More specifically, the sensitivity calculation formula for each channel is:

[0094]

[0095] Among them, represents the sensitivity information corresponding to the i-th channel RF coil at the image space position (x, y); represents the image signal of the i-th channel RF coil at the image space position (x, y); M+N is the total number of channels, and M+N≥2.

[0096] Step S740: Perform weighted processing on the multi-channel image according to the characteristic parameters of each channel after weighted processing, and then merge the multi-channel images after weighted processing.

[0097] Exemplarily, taking the characteristic parameter as sensitivity, perform weighted processing on the multi-channel image according to the sensitivity corresponding to each channel after weighted processing, that is, assign weights to the images corresponding to each channel according to the sensitivity map, and then merge the multi-channel images after weighted processing.

[0098] In one embodiment, the magnetic resonance system includes a scanner, the body coil 500 is integrated inside the scanner, and the surface coil 600 is placed on the surface of the detection object. Specifically, as Figure 8 shown, the body coil 500 can be a birdcage coil inside the scanner. The birdcage coil is formed by splicing a plurality of coil units 100 along the axial direction of the scanning cavity, which can cover the entire detection object, and the surface coil 600 is a layout coil covering the surface of the detection object. As Figure 9 shown, the left side respectively shows the signal-to-noise ratios of the images in the Z-X and X-Y planes under the traditional signal acquisition method, and the right side shows the signal-to-noise ratios of the images when the body coil 500 and the surface coil 600 are simultaneously acquired in the Z-X and X-Y planes. It can be known through simulation that compared with the traditional signal acquisition, using the body coil 500 and the surface coil 600 to receive signals together, the uniformity of the images in all directions is better, the geometric factor obtained by simulation is closer to 1, and its signal-to-noise ratio is higher.

[0099] In some embodiments, determine the undersampling acceleration factor of the magnetic resonance signal according to the number of receiving channels corresponding to the first group of magnetic resonance signals and the number of receiving channels corresponding to the second group of magnetic resonance signals. That is, determine the acceleration multiple according to the number of channels of the body coil 500 and the surface coil 600 and their corresponding positional relationships. For example, in the Y direction of the birdcage coil, the number of coil units 100 of the body coil 500 for the same field of view is 3, and the number of coil units of the surface coil 600 along the X direction is 4. Each coil unit corresponds to an independent channel. When the body coil 500 and the surface coil 600 are simultaneously acquired, the acceleration multiple increases from 4 to 7. With such a setting, the acceleration multiples in the X, Y, and Z directions are increased when receiving signals. Compared with the traditional acquisition method, the acceleration performance of the coil array is increased. Specifically, the acceleration multiple can also be determined first according to the imaging requirements, and then the channels can be merged according to the acceleration multiple and the imaging requirements.

[0100] It should be understood that although Figure 6 、 7Each step in the flowchart in [reference] is displayed sequentially according to the indication of the arrow, but these steps are not necessarily executed sequentially in the order indicated by the arrow. Unless otherwise clearly stated in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 6 and 7 at least some of the steps in [reference] may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be executed alternately or in turn with at least some of the steps or stages in other steps or other steps.

[0101] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, storage, database, or other medium used in the embodiments provided in this application can include at least one of non-volatile and volatile memories. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, or optical memory, etc. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0102] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0103] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A radio frequency coil assembly suitable for a magnetic resonance system, characterized in that, The radio frequency coil assembly includes: A coil body, the coil body including a plurality of coil units (100); A mode switching circuit (200), connected to at least one of the coil units (100), for controlling the coil unit to switch from a transmit mode to a receive mode, or from a receive mode to a transmit mode; the coil unit (100) is capable of generating radio frequency pulses in the transmit mode, and the coil unit (100) is capable of receiving magnetic resonance signals in the receive mode; A preamplifier (400), for amplifying the magnetic resonance signals received by the coil unit; A matching circuit (300), disposed between the mode switching circuit (200) and the preamplifier (400), when the coil unit (100) is in the transmit mode, the matching circuit (300) is used to achieve power matching between the radio frequency power amplifier and the coil unit (100); when the coil unit (100) is in the receive mode, the matching circuit is used to achieve noise matching between the coil unit (100) and the preamplifier (400).

2. The radio frequency coil assembly according to claim 1, wherein Each of the coil units (100) is connected to an RF power amplifier, and each RF power amplifier can independently control the amplitude and phase of the radio frequency pulses generated by the corresponding coil unit (100).

3. The RF coil assembly according to claim 1, wherein The mode switching circuit (200) includes a first control loop and a second control loop. When the control current is turned on, the first control loop and the second control loop are turned on, and the coil unit (100) switches from the receive mode to the transmit mode. When the control current is turned off, the first control loop and the second control loop are turned off, and the coil unit (100) switches from the transmit mode to the receive mode.

4. The radio frequency coil assembly according to claim 1, characterized in that The coil unit (100) is of a loop structure, and a plurality of loop structures form a single-layer transmit array.

5. A magnetic resonance system, the magnetic resonance system including: A main magnet (700), surrounding to form a scanning cavity, the main magnet (700) being used to form a main magnetic field; Gradient coils, disposed inside the main magnet (700), for forming a gradient field; A body coil (500) is disposed inside the gradient coil (500), and the body coil (500) can be switched to a transmit mode or a receive mode; the body coil (500) includes: A coil body, the coil body including a plurality of coil units (100); A mode switching circuit (200), connected to at least one of the coil units (100), for controlling the coil unit (100) to switch from a transmit mode to a receive mode, or from a receive mode to a transmit mode; the coil unit (100) is capable of generating radio frequency pulses in the transmit mode, and the coil unit (100) is capable of receiving magnetic resonance signals in the receive mode; A preamplifier (400), for amplifying the magnetic resonance signals received by the coil unit (100); A matching circuit (300) is provided between the mode switching circuit (200) and the preamplifier (400). When the coil unit (100) is in the transmit mode, the matching circuit (300) is used to achieve power matching between the RF power amplifier and the coil unit (100); when the coil unit (100) is in the receive mode, the matching circuit (300) is used to achieve noise matching between the coil unit (100) and the preamplifier (400).

6. A control method for a magnetic resonance system, the magnetic resonance system comprising: A surface coil (600) for receiving magnetic resonance signals of a detection object; A body coil (500) comprising a plurality of coil units (100); The control method comprises: Controlling the coil unit (100) of the body coil (500) to operate in the transmit mode to generate RF pulses, which can excite nuclear spins in the body of the detection object under the main magnetic field to generate magnetic resonance signals; Controlling the coil unit (100) of the body coil (500) to operate in the receive mode to obtain a first set of magnetic resonance signals, and controlling the surface coil (600) to be in a resonant state to obtain a second set of magnetic resonance signals; Obtaining a target image of the detection object based on the first set of magnetic resonance signals and the second set of magnetic resonance signals.

7. The control method according to claim 6, wherein The body coil (500) further comprises: A mode switching circuit (200) connected to at least one of the coil units (100) for controlling the coil unit (100) to switch from the transmit mode to the receive mode, or from the receive mode to the transmit mode; the coil unit (100) can generate RF pulses in the transmit mode, and the coil unit (100) can receive magnetic resonance signals in the receive mode; A preamplifier (400) for amplifying the magnetic resonance signals received by the coil unit (100); A matching circuit (300) is provided between the mode switching circuit (200) and the preamplifier (400). When the coil unit (100) is in the transmit mode, the matching circuit (300) is used to achieve power matching between the RF power amplifier and the coil unit (100); when the coil unit (100) is in the receive mode, the matching circuit (300) is used to achieve noise matching between the coil unit (100) and the preamplifier (400).

8. The control method according to claim 6, characterized in that The first set of magnetic resonance signals corresponds to multiple receive channels, and the second set of magnetic resonance signals corresponds to multiple receive channels; Obtaining a target image of the detection object based on the first set of magnetic resonance signals and the second set of magnetic resonance signals includes: Performing channel merging reconstruction on the first set of magnetic resonance signals and the second set of magnetic resonance signals to obtain a target image of the detection object.

9. The control method according to claim 6, characterized in that The magnetic resonance system includes a scanner, the body coil (500) is integrated inside the scanner; the surface coil is placed on the surface of the detection object.

10. The control method according to claim 6, characterized in that, Determine the undersampling acceleration factor of the magnetic resonance signal according to the number of receiving channels corresponding to the first group of magnetic resonance signals and the number of receiving channels corresponding to the second group of magnetic resonance signals.

Images