CN214845725U

CN214845725U - Transmitting coil assembly

Info

Publication number: CN214845725U
Application number: CN202120642097.1U
Authority: CN
Inventors: 车韶
Original assignee: Shanghai United Imaging Healthcare Co Ltd
Current assignee: Shanghai United Imaging Healthcare Co Ltd
Priority date: 2021-03-30
Filing date: 2021-03-30
Publication date: 2021-11-23
Anticipated expiration: 2031-03-30

Abstract

The present application relates to a transmit coil assembly. The transmit coil assembly includes a first end ring, a second end ring, a plurality of legs, a control line, and a first switch assembly. The second end ring is disposed opposite the first end ring at a spacing. A plurality of legs connect the first end ring and the second end ring and are circumferentially distributed. The control wire at least partially surrounds the plurality of legs. The control line is used to send control signals. The first switch assembly is disposed on at least one leg of the plurality of legs. The first switch assembly is used for controlling the on or off of the radio frequency performance of the support leg where the first switch assembly is located according to the control signal. When the radio frequency performance of at least one of the legs is controlled to be on, the first switch component presents low impedance. When the radio frequency performance of at least one supporting leg is controlled to be switched off, the first switch component presents high impedance. When at least one supporting leg is in high impedance, the transmitting coil assembly is in a detuned state, and the influence on the receiving coil is reduced. The quality of the signal received by the receiving coil is improved.

Description

Transmitting coil assembly

Technical Field

The present application relates to the field of magnetic resonance technology, and more particularly, to a transmit coil assembly.

Background

A birdcage coil is a basic form of a magnetic resonance system transmit coil assembly that can be used for both volume and local transmissions. In a typical volume transmit application scenario, the birdcage coil is mounted inside the system aperture and a uniform excitation radio frequency field can be formed throughout the system scan field. One basic procedure for magnetic resonance pulse sequence scanning generally involves gradient encoding and radio frequency excitation, signal relaxation, readout gradient encoding and radio frequency reception.

During the radio frequency excitation of the magnetic resonance system, a radio frequency excitation pulse formed by a radio frequency power amplifier excites a magnetic resonance signal within the scan field of view by a radio frequency transmit coil assembly, which is in a tuned state. During radio frequency reception, magnetic resonance signals need to be received by the local coil. How to improve the signal quality received by the local receiving coil is an urgent problem to be solved.

SUMMERY OF THE UTILITY MODEL

In view of the above, it is necessary to provide a transmitting coil assembly for improving the quality of signals received by local receiving coils.

A transmit coil assembly includes a first end ring, a second end ring, a plurality of legs, a control line, and a first switch assembly. The second end ring is disposed in spaced opposition to the first end ring. The plurality of legs connect the first end ring and the second end ring. A plurality of legs are distributed along a circumference of the first end ring or the second end ring. The control wire at least partially surrounds the plurality of legs. And the control line is used to send control signals. The first switch assembly is disposed on at least one leg of the plurality of legs. The first switch assembly is used for controlling the on or off of the radio frequency performance of the supporting leg where the first switch assembly is located according to the control signal. When the radio frequency performance of the at least one supporting leg is controlled to be switched on, the first switch component presents low impedance. When the radio frequency performance of the at least one supporting leg is controlled to be switched off, the first switch component presents high impedance.

In one embodiment, the first switching assembly includes a first switching tube and a first detuning circuit. The first switch tube is arranged on the at least one supporting leg. The first detuning circuit is connected to two ends of the first switching tube in parallel.

In one embodiment, the first detuning circuit comprises a first inductive device. The first inductive device is connected in parallel to two ends of the first switch tube.

In one embodiment, the first inductive device is an adjustable inductor.

In one embodiment, the first detuning circuit further comprises a first capacitive device. The first capacitive device is connected to two ends of the first switch tube in parallel, and the first capacitive device is connected to the first inductive device in parallel.

In one embodiment, the control wire forms a control loop around the plurality of legs. The first capacitive means and the first inductive means are arranged adjacent to the control loop.

In one embodiment, the first end ring, the second end ring, and the plurality of legs form a birdcage structure. The control ring is arranged in the middle or at two ends of the birdcage structure.

In one embodiment, the transmit coil assembly further comprises a second switch assembly. The second switch assembly is disposed on another leg of the plurality of legs. The second switch device is used for controlling the on or off of the radio frequency performance of the other supporting leg according to the control signal. When the radio frequency performance of the at least one supporting leg is controlled to be switched off, the second switch component presents high impedance, and the high impedance of the second switch component is different from that of the first switch component.

A transmit coil assembly includes a birdcage coil, a control line, and a first switch assembly. The control wire at least partially surrounds the birdcage coil and is configured to transmit a control signal. The first switch assembly is disposed on the birdcage coil. The first switch assembly is used for controlling the radio frequency performance of the birdcage coil to be switched on or switched off according to the control signal. When the radio frequency performance of the birdcage coil is controlled to be switched on, the first switch component presents low impedance. When the radio frequency performance of the birdcage coil is controlled to be switched off, the first switch component presents high impedance.

In one embodiment, the first switching component comprises a first switching tube, a first inductive device and/or a first capacitive device. The first switch tube is arranged on one supporting leg of the birdcage coil. The first inductive device is connected in parallel to two ends of the first switch tube. The first capacitive device is connected to two ends of the first switch tube in parallel.

A transmit coil assembly comprising:

a first end ring;

a second end ring disposed in spaced opposition to the first end ring;

a plurality of legs connecting the first end ring and the second end ring, the plurality of legs being distributed along a circumferential direction of the first end ring or the second end ring;

the first switch assembly comprises a first switch tube and a first detuning circuit. The first switching tube is arranged on at least one leg or on at least one end ring. The first detuning circuit is connected to two ends of the first switching tube in parallel.

And the control line is electrically connected with the first switch assembly.

In one embodiment, the number of the switch assemblies is two or more, and the switch assemblies are respectively arranged on two or more of the supporting legs;

the first detuning circuit comprises: the first inductive device is connected to two ends of the first switch tube in parallel; and/or the first capacitive device is connected in parallel with two ends of the first switching tube.

The transmit coil assembly provided by the embodiments of the present application includes a first end ring, a second end ring, a plurality of legs, a control line, and a first switch assembly. The second end ring is disposed in spaced opposition to the first end ring. The plurality of legs connect the first end ring and the second end ring. A plurality of legs are distributed along a circumference of the first end ring or the second end ring. The control wire at least partially surrounds the plurality of legs. And the control line is used to send control signals. The first switch assembly is disposed on at least one leg of the plurality of legs. The first switch assembly is used for controlling the on or off of the radio frequency performance of the supporting leg where the first switch assembly is located according to the control signal. When the radio frequency performance of the at least one supporting leg is controlled to be switched on, the first switch component presents low impedance. When the radio frequency performance of the at least one supporting leg is controlled to be switched off, the first switch component presents high impedance. The transmit coil assembly is in resonance when the at least one leg is low impedance. When at least one supporting leg is in high impedance, the transmitting coil assembly is in a detuning state, so that the influence on the receiving coil is reduced, and the quality of signals received by the receiving coil is improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings used in the descriptions of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the following descriptions are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic diagram of the structure of the transmit coil assembly provided in one embodiment of the present application;

fig. 2 is an equivalent circuit diagram of a diode provided in an embodiment of the present application;

FIG. 3 is a schematic structural diagram of the transmitting coil assembly provided in a second embodiment of the present application;

FIG. 4 is a schematic circuit diagram of the transmit coil assembly provided in a second embodiment of the present application;

figure 5 is a position diagram of a first inductive device and a first capacitive device as provided in an embodiment of the present application;

FIG. 6A is a schematic end view of the body of the transmit coil assembly;

fig. 6B is a schematic structural diagram of the transmitting coil assembly provided in the third embodiment of the present application;

fig. 7 is a schematic structural diagram of the transmitting coil assembly provided in the fourth embodiment of the present application.

Reference numerals:

10. a transmit coil assembly; 200. a birdcage coil; 20. a first end ring; 30. a second end ring; 40. a support leg; 400. a control loop; 410. a first connecting member; 420. a first switch tube; 430. a second connecting member; 50. a first detuning circuit; 510. a first inductive device; 520. a first capacitive device; 60. a second capacitor; 70. a second detuning circuit; 710. a second inductive device; 720. a second switching device; 110. a control line; 120. a first switch assembly; 130. the second switch assembly.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present application more comprehensible, embodiments accompanying the present application are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. This application is capable of embodiments in many different forms than those described herein and those skilled in the art will be able to make similar modifications without departing from the spirit of the application and it is therefore not intended to be limited to the embodiments disclosed below.

The numbering of the components as such, e.g., "first", "second", etc., is used herein for the purpose of describing the objects only, and does not have any sequential or technical meaning. The term "connected" and "coupled" when used in this application, unless otherwise indicated, includes both direct and indirect connections (couplings). In the description of the present application, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present application and for simplicity in description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be considered as limiting the present application.

In this application, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through intervening media. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

Referring to fig. 1, an embodiment of the present application provides a transmit coil assembly 10 including a birdcage coil 200 and a first switch assembly 120. The first switching assembly 120 includes a first switching tube 420 and a first detuning circuit 50. The first switch tube 420 is connected to the birdcage coil 200. When the first switch tube 420 is turned off, the birdcage coil 200 is detuned. The first detuning circuit 50 is connected in parallel to two ends of the first switching tube 420. The first detuning circuit 50 is used to suppress or even cancel the parasitic capacitance generated when the first switching tube 420 is turned off.

When the first switch tube 420 is turned off, the birdcage coil 200 is detuned, and a parasitic capacitance exists in the first switch tube 420. The parasitic capacitance causes signal leakage of the transmit coil assembly 10. The amount of signal leakage of the transmit coil assembly 10 increases with increasing frequency. In a high frequency application scenario, the parasitic capacitance may cause the cut-off characteristic of the first switching tube 420 to deteriorate rapidly. The first detuning circuit 50 of the transmitting coil assembly 10 provided by the embodiment of the present application is connected in parallel to two ends of the first switching tube 420. The first detuning circuit 50 is used for suppressing or even canceling a parasitic capacitance generated when the first switching tube 420 is turned off, and improving a cut-off characteristic of the first switching tube 420, thereby improving the detuning isolation of the transmitting coil assembly 10. The higher the isolation of the detuning of the transmit coil assembly 10, the better the signal quality received by the local coil.

When the first switch device 420 is turned on, the transmitting coil assembly 10 is configured to receive a driving signal sent by the rf power amplifier to transmit an rf pulse to the outside, and the rf pulse excites nuclear spins in the detection object within the scanning range, while the transmitting coil assembly 10 is in a tuning state. During radio frequency reception, magnetic resonance signals need to be received by the local coil while the transmit coil assembly 10 is in a detuned state.

The first switch tube 420 is used to control the birdcage coil 200 to be in a tuned state or a detuned state. When the transmitting coil assembly 10 needs to excite the detected object to generate the magnetic resonance signal, the first switch tube 420 is in the closed/conducting state. When the local coil is required to receive the magnetic resonance signal, the first switch tube 420 is in an off state, and the transmitting coil assembly 10 is in a detuned state, that is, the transmitting coil assembly 10 does not operate.

In one embodiment, the birdcage coil 200 includes a first end ring 20, a second end ring 30, and a plurality of legs 40. The second end ring 30 is disposed in spaced relation opposite the first end ring 20. One end of a plurality of the legs 40 is connected to the first end ring 20. The other end of the plurality of legs 40 is connected to the second end ring 30. A plurality of the legs 40 are distributed along the circumferential direction of the first end ring 20 or the second end ring 30.

In one embodiment, the transmit coil assembly 10 further includes a control line 110. At least partially surrounding the plurality of legs 40, and the control line 110 is used to send control signals. The first switch assembly 120 is disposed on at least one leg 40 of the plurality of legs 40, and the first switch assembly 120 is configured to control on or off of the radio frequency performance of the leg 40 on which the first switch assembly 120 is located according to the control signal. When the rf performance of the at least one leg is controlled on, the first switch assembly 120 presents a low impedance. When the rf performance of the at least one leg is controlled to be turned off, the first switch assembly 120 presents a high impedance. The transmit coil assembly is in resonance when the at least one leg is low impedance. When at least one supporting leg is in high impedance, the transmitting coil assembly is in a detuning state, so that the influence on the receiving coil is reduced, and the quality of signals received by the receiving coil is improved.

The first switch transistor 420 may be a diode, a transistor, a MOS transistor, or the like. In a typical volume transmit application scenario, the birdcage coil 200 is mounted inside the system aperture and a uniform excitation radio frequency field can be formed throughout the system scan range. The first switch tube 420 is a diode. The on and off states of the diode are influenced by the thickness of the intrinsic layer (I layer) of the diode and parasitic parameters, and the like, and ideal open and short circuit states cannot be achieved. When the diode is conducting, there is usually a certain insertion loss, typically around a few tenths of a dB. When the diode is turned off, there is still some power leakage, reflecting an isolation of about minus ten to tens of dB. At higher frequencies, the off-state isolation of the diodes typically decreases, resulting in a decrease in the overall detuning effect of the birdcage coil.

Referring to fig. 2, an equivalent model of the diode in the off state is:

the first capacitor Cj is connected in parallel with two ends of the first resistor Rp and then connected in series with the first inductor Lp to form a first circuit. The parasitic capacitance Cp is connected in parallel to both ends of the first circuit. Wherein the resistance value of the first resistor Rp is in the kilo-ohm level. The capacitance value of the parasitic capacitance Cp is on the picofarad order.

The first capacitor Cj, the first inductor Lp, the first resistor Rp and the parasitic capacitor Cp respectively represent parasitic parameters of the internal structure of the diode and belong to the attributes of the diode. The equivalent circuit shown in fig. 2 can be used as a circuit model of the diode for analyzing the operating characteristics of the diode. The power leaked by the first resistor Rp is not affected by the frequency of the rf signal. The power of the parasitic capacitance Cp leakage increases with increasing frequency of the rf signal.

Illustratively, the equivalent impedance of the capacitive device is:

wherein, X_cThe capacitance impedance is represented by j, an imaginary number, ω an angular frequency (corresponding to the larmor frequency or precession frequency of the magnetic resonance system), and C a capacitance. In general, in a low frequency range, the parasitic parallel capacitance Cp of the diode has a small value and a corresponding impedance value is large. The parasitic parallel capacitance Cp has a small influence on the impedance of the equivalent circuit of the diode in the OFF state. However, as the frequency ω increases, the equivalent parallel impedance Xp of the parasitic parallel capacitance Cp of the diode decreases, resulting in a decrease in the total impedance of the entire circuit (equivalent circuit with the diode in the off state). The total impedance of the diode decreases, causing leakage of the radio frequency signal from the side of the parallel capacitor Cp, so that the cut-off performance of the diode is degraded.

The first detuning circuit 50 is connected in parallel to the first switching tube 420, and is used for suppressing or removing the influence of parasitic capacitance on the cut-off performance of the diode.

Referring also to fig. 3, in one embodiment, the first detuning circuit 50 includes a first inductive device 510. The first inductive device 510 is connected in parallel to two ends of the first switching tube 420 to form a parallel resonant circuit.

The first inductive device 510 forms a parallel resonance with a parasitic capacitance in the first switching tube 420. The equivalent impedance of the parallel resonant circuit is:

where Zp is the equivalent impedance of the parallel resonant circuit, L is the inductance of the first inductive device 510, and r is the total resistance in the parallel resonant circuit. By selecting the first inductive device 510 with a larger inductance, a larger equivalent impedance of the parallel resonant circuit can be obtained, so that the total impedance value of the equivalent circuit of the first switching tube 420 in the off state is larger, and the off performance of the first switching tube 420 is improved.

The first inductive device 510 includes an inductance. The first inductive device 510 may be one or several in series. The first inductive device 510 includes an adjustable inductance. By adjusting the first inductive device 510, the resonance properties of the transmit coil assembly 10 can be changed, making the transmit coil assembly 10 suitable for different magnetic resonance systems.

In one embodiment, the first detuning circuit 50 further comprises a first capacitive device 520. The first capacitive device 520 is connected in parallel to both ends of the first switching tube 420, and the first capacitive device 520 is connected in parallel to the first inductive device 510. The first capacitive device 520 comprises an adjustable capacitance. The first capacitive element 520 may be one or several in series.

The first capacitive device 520 is connected in parallel with a parasitic capacitor for adjusting the total capacitance value at both ends of the first switch tube 420. The kind of the first switch tube 420 and the frequency of the rf signal are related to the magnitude of the parasitic capacitance.

Referring to fig. 4, when the type of the first switch tube 420 is different or the frequency of the rf signal is changed, the impedance value of the parasitic capacitor is changed. If only one first inductive device 510 is connected in parallel to two ends of the first switch tube 420, and the size of the first inductive device 510 is fixed, the total impedance of the circuit in which the first switch tube 420 and the first inductive device 510 are connected in parallel changes with the frequency of the radio frequency signal, and the cut-off performance of the first switch tube 420 is unstable.

When the first switching tube 420 is connected in parallel with the first capacitive element 520 and the first inductive element 510, the first capacitive element 520 is connected in parallel with the parasitic capacitance. Adjusting the first capacitive element 520 may adjust the total capacitance of the first capacitive element 520 and the parasitic capacitance.

The capacitance of the first capacitive element 520 is adjusted to be much larger than the capacitance of the parasitic capacitance, so as to reduce the influence of the change of the parasitic capacitance on the total capacitance of the first capacitive element 520 and the parasitic capacitance. The total capacitance of the first capacitive device 520 and the parasitic capacitor is relatively stable, and the total impedance value of the first switching tube 420, the first capacitive device 520 and the first inductive device 510 connected in parallel is stable, so that the blocking performance of the first switching tube 420 is improved.

In one embodiment, the control wire 110 forms a control loop around the plurality of legs 40. The first capacitive device 520 and the first inductive device 510 are arranged adjacent to the control loop to reduce the distribution of control lines and to reduce wire coupling.

The first end ring 20, the second end ring 30 and the plurality of support legs 40 form a birdcage structure, and the control ring is disposed at a middle position or at two end positions of the birdcage structure.

In one embodiment, the leg 40 includes a first connector 410 and a second connector 430 connected in series. The first connector 410 is connected to the first end ring 20. The second connector 430 is connected to the second end ring 30. The first switching tube 420 is connected between the first connector 410 and the second connector 430.

When the first switch tube 420 is turned on, the first connection member 410 and the second connection member 430 are turned on, and the first end ring 20, the second end ring 30 and the leg 40 form the generating coil in a resonant state. When the first switch tube 420 is opened, the first connector 410 and the second connector 430 are disconnected, and the first end ring 20, the second end ring 30 and the leg 40 form the generating coil in a detuned state.

The first capacitive element 520 and the first inductive element 510 may be disposed on the first connector 410 or the second connector 430.

Referring to fig. 5, in one embodiment, the first capacitive device 520 and the first inductive device 510 are disposed at one end of the first connecting element 410 close to the first switch tube 420.

If the first capacitive device 520 and the first inductive device 510 are far away from the first switch tube 420, the first capacitive device 520 needs to be connected in parallel with two ends of the first switch tube 420 through a line. The first inductive device 510 is also connected in parallel to both ends of the first switching tube 420 through a line.

The first capacitive device 520, the line and the first switching tube 420 form a closed loop, and a new induced current is formed under the action of a radio frequency signal, so that the blocking performance of the first switching tube 420 is reduced. The first inductive device 510, the line and the first switch tube 420 form a closed loop, and a new induced current is also formed under the action of the radio frequency signal, so that the cut-off performance of the first switch tube 420 is reduced.

Therefore, the first capacitive device 520 and the first inductive device 510 are disposed close to the first switch tube 420, so as to avoid generation of new induced current and improve the blocking performance of the first switch tube 420. In addition, the first capacitive device 520 and the first inductive device 510 are disposed close to the first switch tube 420, which is compact and facilitates reducing the overall volume of the transmitting coil assembly 10.

When the first switch tube 420 is in the conducting state, the first detuning circuit 50 is bypassed and the transmitting coil assembly 10 is in the resonant state because the resistance of the first switch tube 420 is much smaller than the impedance of the first detuning circuit 50.

In one embodiment, the leg 40 is plural. The first detuning circuit 50 is connected in parallel to the leg 40 with the largest current.

The number of the supporting legs 40 is multiple, and the center lines of the supporting legs 40 are parallel to each other. A plurality of the legs 40 are arranged in a ring shape at equal intervals.

The current on the birdcage coil 200 is distributed in a discrete form, and the current on the corresponding nth leg is approximately:

wherein, J_leg(n) is the current on the nth leg; n is the total number of legs. For example: when N is 12, the 1 st leg to the 12 th leg are counted clockwise. The current is greatest in the 1 st and 6 th legs. The first detuning circuit 50 is connected in parallel to the first switch tube 420 of the 1 st leg or the first switch tube 420 of the 6 th leg, and can cut off the current of the 1 st leg or the 6 th leg, thereby detuning the transmitting coil assembly 10.

Referring to fig. 6A, which is a partial end view of the body 200, a second capacitor 60 is disposed on a side surface of the first end ring 20, and the second capacitor 60 is connected to the first end ring 20, specifically, a tuning capacitor of the first end ring 20.

Referring also to fig. 6B, in one embodiment, the transmit coil assembly 10 further includes a second detuning circuit 70. Illustratively, the second capacitor 60 is disposed on the first end ring 20 and connected to the first end ring 20. The second detuning circuit 70 is connected in parallel across the second capacitance 60.

The second capacitor 60, the first end ring 20, the second end ring 30 and the leg 40 together form a resonant circuit to ensure that the transmit coil assembly 10 receives the rf excitation pulse from the rf power amplifier and excites the magnetic resonance signal within the scan range. When the second detuning circuit 70 is connected in parallel with the second capacitor 60, the second detuning circuit 70 forms a high impedance circuit with the second capacitor 60, so that the first end ring 20 is open-circuited and detuned.

The second detuning circuit 70 comprises a switching device, an inductive or capacitive device, etc.

Referring also to fig. 7, in one embodiment, the second detuning circuit 70 further includes a second inductive device 710 and a second switching device 720. The second inductive device 710 is connected in parallel across the second capacitor 60. The second switching device 720 is connected in parallel to the two ends of the second capacitor 60 and is connected in parallel to the second inductive device 710. When the second switch device 720 is turned on, the second capacitor 60, the first end ring 20, the second end ring 30 and the leg 40 together form a resonant circuit and are in a resonant state. When the second switching device 720 is open, the transmit coil assembly 10 is in a detuned state. In this case, in order to avoid that the parasitic capacitance in the second switching device 720 varies greatly with the radio frequency signal, the second capacitance 60 and the second inductive device 710 form a detuning circuit, and by adjusting the size of the second inductive device 710, a high impedance circuit formed by the second switching device 720, the second capacitance 60 and the second inductive device 710 in parallel can be formed.

In one embodiment, the second detuning circuit 70 further comprises a second capacitive device. The second capacitive element is connected in parallel to both ends of the second capacitor 60, and the second capacitive element is connected in parallel to both ends of the second switching device 720.

The second inductive means 710 comprises an inductance. The second inductive means 710 may be one or several in series. The second capacitive device comprises a capacitor. The second capacitive element may be one or several in series.

When the second switching means 720 is connected in parallel with the second capacitive device, the second capacitance 60 and the second inductive device 710 at the same time, the second capacitive device is connected in parallel with the parasitic capacitance of the second switching means 720. Adjusting said second capacitive element may adjust the total capacitance value of said second capacitive element, said parasitic capacitance of said second switching means 720 and said second capacitance 60.

The capacitance of the second capacitive device is adjusted to be much larger than the capacitance of the parasitic capacitance of the second switching means 720 to reduce the effect of the variation of the heating parasitic capacitance of the second switching means 720 on the total capacitance (the total capacitance of the second capacitive device, the second capacitor 60 and the second inductive device 710). The total capacitance value (the total capacitance value of the second capacitive device, the second capacitor 60 and the second inductive device 710) is relatively stable, and the total impedance value of the second switching device 720, the second capacitor 60, the second capacitive device and the second inductive device 710 connected in parallel is stable, so that the chopping performance of the second switching device 720 is improved.

When the second switching device 720 is in the on state, the second detuning circuit 70 is bypassed and the transmitting coil assembly 10 is in the resonant state because the resistance of the second switching device 720 is much smaller than the impedance of the second detuning circuit 70.

In one embodiment, the legs 40 are circumferentially spaced apart. The second capacitors 60 are plural, and each second capacitor 60 is disposed between two adjacent legs 40. The second detuning circuit 70 is plural. One of the second detuning circuits 70 is arranged corresponding to one of the second capacitors 60.

By providing a plurality of the second detuning circuits 70 such that any two adjacent legs 40 are in a high-impedance state when the second switching device 720 is turned off, the detuning performance of the transmitting coil assembly 10 is further improved, and power leakage is avoided.

In order to ensure the consistency of the on and off of a plurality of said second switching means 720. The plurality of second switching devices 720 are identical in model, lot number, and manufacturer. The components of the second detuning circuits 70 are the same, so as to ensure that the second switching devices 720 are turned on and off at the same time, thereby improving the detuning isolation of the transmitting coil assembly.

In one embodiment, the birdcage coil 200 includes a first end ring 20 and a second capacitor 60. The second capacitor 60 is disposed on the first end ring 20 and connected to the first end ring 20. The first switch tube 420 is connected in parallel to two ends of the second capacitor 60.

When the first switch tube 420 is turned off, the first end ring 20 is turned off, the birdcage coil 200 is detuned, and the first switch tube 420 has a parasitic capacitance. The parasitic capacitance causes signal leakage of the transmit coil assembly 10. As the frequency increases, the amount of signal leakage from the transmit coil assembly 10 increases. In a high frequency application scenario, the parasitic capacitance of the first switching tube 420 may cause the cut-off characteristic of the first switching tube 420 to deteriorate rapidly. The first detuning circuit 50 is connected in parallel to two ends of the first switching tube 420. The first detuning circuit 50 is configured to cancel a parasitic capacitance generated when the first switching tube 420 is turned off, so as to improve a cut-off characteristic of the first switching tube 420, and further improve detuning isolation of the transmitting coil assembly 10. The higher the isolation of the detuning of the transmit coil assembly 10, the better the signal quality received by the local coil.

When the first switch tube 420 is in the closed state, the transmit coil assembly 10 is in the resonant state for exciting magnetic resonance signals.

In one embodiment, the first switching tube 420 and the first detuning circuit 50 are disposed at an end ring. The first switch tube 420 is disposed at intervals of two second capacitors 60, so as to reduce the number of devices and simplify the structure.

In one embodiment, the birdcage coil includes three forms: the self resonance capacitor is arranged on the leg; the self resonance capacitor is arranged on the end ring; self-resonant capacitors are provided at the legs and end-rings.

The first switch tube 420 and the first detuning circuit 50 have the following forms:

the first switch tube 420 is arranged on the leg, and the first detuning circuit 50 is arranged on the leg; the first switch tube 420 is disposed on an end ring, and the first detuning circuit 50 is disposed on the end ring; the first switch tube 420 is disposed at a leg and an end ring, and the first detuning circuit 50 is disposed at a leg and an end ring.

In one embodiment, the transmit coil assembly 10 further includes a second switching assembly 130. The second switch assembly 130 is disposed on another leg of the plurality of legs 40, and the second switch device is configured to control the radio frequency performance of the another leg to be turned on or off according to the control signal. When the radio frequency performance of the leg 40 where the second switch element 130 is located is controlled to be turned off, the second switch element 130 presents a high impedance, and the high impedance of the second switch element 130 is different from the high impedance of the first switch element 120. As mentioned above, each leg of the birdcage coil has a set current value, and the larger the current value flowing through the leg is, the more difficult the first switch device 420 is to be switched; conversely, the smaller the value of the current flowing through the leg, the easier it is to turn on the first switch device 420. In this embodiment, the high impedance value of the switch assembly is set in positive correlation with the current flowing through the corresponding leg.

The present embodiment provides a transmit coil assembly 10 that includes a birdcage coil 200, a control line 110, and a first switch assembly 120. The control wire 110 at least partially surrounds the birdcage coil 200, and the control wire 110 is used to transmit control signals. The first switch assembly 120 is disposed on the birdcage coil 200. The first switch assembly 120 is used to control the radio frequency performance of the birdcage coil 200 to be turned on or off according to the control signal. When the radio frequency performance of the birdcage coil 200 is controlled on, the first switch element 120 presents a low impedance. When the radio frequency performance of the birdcage coil 200 is controlled to be turned off, the first switch element 120 presents a high impedance.

The present application provides a magnetic resonance system comprising a transmit coil assembly 10 as described in any of the above embodiments. The transmit coil assembly 10 includes a birdcage coil 200, a first switching tube 420, and a first detuning circuit 50. The first switch tube 420 is connected to the birdcage coil 200. When the first switch tube 420 is turned off, the birdcage coil 200 is detuned. The first detuning circuit 50 is connected in parallel to two ends of the first switching tube 420. The first detuning circuit 50 is used to cancel the parasitic capacitance generated when the first switching tube 420 is turned off.

When the first switch tube 420 is turned off, the birdcage coil 200 is detuned, and a parasitic capacitance exists in the first switch tube 420. The parasitic capacitance causes signal leakage of the transmit coil assembly 10. The amount of signal leakage of the transmit coil assembly 10 increases with increasing frequency. In a high frequency application scenario, the parasitic capacitance may cause the cut-off characteristic of the first switching tube 420 to deteriorate rapidly. In the magnetic resonance system provided by the embodiment of the present application, the first detuning circuit 50 is connected in parallel to two ends of the first switching tube 420. The first detuning circuit 50 is used for suppressing or even canceling a parasitic capacitance generated when the first switching tube 420 is turned off, and improving a cut-off characteristic of the first switching tube 420, thereby improving the detuning isolation of the transmitting coil assembly 10. The higher the isolation of the detuning of the transmit coil assembly 10, the better the signal quality received by the local coil.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-described examples merely represent several embodiments of the present application and are not to be construed as limiting the scope of the claims. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A transmit coil assembly, comprising:

a first end ring;

a second end ring disposed in spaced opposition to the first end ring;

a control wire at least partially surrounding the plurality of legs, the control wire for transmitting a control signal;

the first switch assembly is arranged on at least one of the support legs and is used for controlling the on or off of the radio frequency performance of the support leg where the first switch assembly is located according to the control signal;

when the radio frequency performance of the at least one supporting leg is controlled to be switched on, the first switch component presents low impedance;

when the radio frequency performance of the at least one supporting leg is controlled to be switched off, the first switch component presents high impedance.

2. The transmit coil assembly of claim 1, wherein the first switch assembly comprises:

the first switch tube is arranged on the at least one supporting leg;

and the first detuning circuit is connected to two ends of the first switching tube in parallel.

3. The transmit coil assembly of claim 2 wherein the first detuning circuit comprises:

and the first inductive device is connected to two ends of the first switching tube in parallel.

4. The transmit coil assembly of claim 3, wherein the first inductive device is an adjustable inductor.

5. The transmit coil assembly of claim 3 or 4, wherein the first detuning circuit further comprises:

and the first capacitive device is connected to two ends of the first switching tube in parallel, and the first capacitive device and the first inductive device are connected in parallel.

6. The transmit coil assembly as claimed in claim 5, wherein the control wire forms a control loop around the plurality of legs, the first capacitive means and the first inductive means being disposed adjacent the control loop.

7. The transmit coil assembly of claim 6, wherein the first end ring, the second end ring, and the plurality of legs form a birdcage structure, the control ring being disposed at a middle position or at both end positions of the birdcage structure.

8. The transmit coil assembly of any one of claims 1 to 7, further comprising:

the second switch assembly is arranged on the other supporting leg of the plurality of supporting legs and is used for controlling the on or off of the radio frequency performance of the other supporting leg according to the control signal;

when the radio frequency performance of the at least one supporting leg is controlled to be switched off, the second switch component presents high impedance, and the high impedance of the second switch component is different from that of the first switch component.

9. A transmit coil assembly, comprising:

a birdcage coil;

a control line at least partially encircling the birdcage coil, the control line configured to transmit a control signal;

the first switch assembly is arranged on the birdcage coil and is used for controlling the radio frequency performance of the birdcage coil to be switched on or switched off according to the control signal;

when the radio frequency performance of the birdcage coil is controlled to be switched on, the first switch component presents low impedance;

when the radio frequency performance of the birdcage coil is controlled to be switched off, the first switch component presents high impedance.

10. The transmit coil assembly of claim 9, wherein the first switch assembly comprises:

the first switching tube is arranged on one supporting leg of the birdcage coil;

the first inductive device is connected to two ends of the first switch tube in parallel; and/or the presence of a gas in the gas,

and the first capacitive device is connected to two ends of the first switching tube in parallel.

11. A transmit coil assembly, comprising:

a first end ring;

a second end ring disposed in spaced opposition to the first end ring;

a first switch assembly comprising:

a first switching tube disposed on at least one of the legs or at least one end ring;

the first detuning circuit is connected to two ends of the first switching tube in parallel;

a control line electrically connected to the first switching tube in the first switching assembly.

12. The transmit coil assembly of claim 11 wherein the number of the first switch assemblies is two or more, disposed on two or more of the legs, respectively;

the first detuning circuit comprises:

the first inductive device is connected to two ends of the first switch tube in parallel;

and/or the first capacitive device is connected in parallel with two ends of the first switching tube.