WO2023092700A1

WO2023092700A1 - Dual-core radio frequency coil system

Info

Publication number: WO2023092700A1
Application number: PCT/CN2021/137165
Authority: WO
Inventors: 李烨; 杜凤; 邹超; 李楠; 袁家文; 郑海荣; 刘新
Original assignee: 深圳先进技术研究院
Priority date: 2021-11-23
Filing date: 2021-12-10
Publication date: 2023-06-01
Also published as: CN114137458A; CN114137458B

Abstract

Disclosed herein is a dual-core radio frequency coil system. The dual-core radio frequency coil system comprises a first coil, a second coil, a first front-end circuit, and a second front-end circuit. The first coil and the second coil jointly surround a coil support frame to form a single-layer nested structure. The first coil is configured to receive a first nuclear magnetic test signal and generate a first induction signal according to the first nuclear magnetic test signal. The second coil comprises a second transmitting coil and a second receiving coil. The second transmitting coil is configured to receive a second nuclear magnetic test signal and generate a second induction signal according to the second nuclear magnetic test signal. The second receiving coil is arranged corresponding to the second transmitting coil and is configured to collect a second induction signal generated by the second transmitting coil. The first front-end circuit is connected to the first coil, and the second front-end circuit is connected to the second coil.

Description

Dual Core RF Coil System

This application claims priority to a Chinese patent application with application number 202111391579.5 filed with the China Patent Office on November 23, 2021, the entire contents of which are incorporated herein by reference.

technical field

The embodiments of the present application relate to nuclear magnetic resonance technology, for example, to a dual-core radio frequency coil system.

Background technique

Ultra-high-field multinuclear magnetic resonance imaging (Magnetic Resonance Imaging, MRI) and magnetic resonance spectroscopy can provide biochemical, physical and functional and structural information. Due to their excellent resolution and anatomical details, they are useful for exploring the morphological features and Biological research such as related physiological or pathological functions is of great value. Due to the dual-nuclide MRI technique can be used to obtain morphological and metabolic information in biological systems, it has been developed rapidly. Due to the linear dependence of weak nuclides on the strength of the main magnetic field, dual-nuclide magnetic resonance imaging or spectral scanning is mainly performed in ultra- Performed in a high-field magnetic resonance system, it can significantly improve the signal-to-noise ratio (Signal Noise Ratio, SNR), reduce scanning time or improve spatial resolution. However, because the acquired signal strength is not only related to the strength of the main magnetic field, but also related to the core component of the radio frequency (Radio Frequency, RF) coil that excites and receives the magnetic resonance signal, and as the magnetic field strength increases, the inhomogeneity of the radio frequency magnetic field becomes more obvious , the interaction between different nuclear channels, the coupling between channels and the complex electromagnetic wave behavior in high-intensity electromagnetic fields, dielectrics and conductive biological samples, etc. will seriously reduce the transmission efficiency and receiving sensitivity of the coil, coupled with weak nuclide physics The low sensitivity of the properties and the limitations of the application of physical techniques seriously affect the image quality, temporal and spatial resolution. Therefore, there is an urgent need for research on the structure of radio frequency coils that can support the excitation and collection of proton and non-proton signals. In the transmission mode, a uniform transmission field is generated, and in the reception mode, a high-sensitivity reception field is formed, so as to have sufficient coverage and improve Signal-to-noise ratio for weak nuclides.

The dual-core coil design mainly includes: dual-core share a coil loop, mainly through a fixed capacitor in the loop and an inductance in parallel, so that the frequency splits to achieve dual-core resonance at high and low frequencies, but this method is more suitable for dual resonance coils with close frequencies. It is difficult to realize the matching circuit on two frequencies with a relatively large difference at the same time, and the loss caused by the insertion of the trap element will lead to the problem of a decrease in the quality of the coil and the signal-to-noise ratio; using two independent coil circuits to achieve dual-core magnetic In addition to the channel interference of different nuclides, there is also the problem of mutual interference between the excitation and reception channels in the way of excitation and acquisition of resonance signals. There is also the problem that the radio frequency magnetic field is not uniform at high frequencies and the available space in the coil is small.

Contents of the invention

The present application provides a dual-nuclear radio frequency coil system to achieve uniform excitation of dual-nuclear signals in the region of interest and high-sensitivity acquisition of weak nuclide signals.

The application provides a dual-core radio frequency coil system, including: a first coil, a second coil, a first front-end circuit and a second front-end circuit;

The first coil and the second coil are wound together on a coil support frame to form a single-layer nested structure;

The first coil is configured to receive a first nuclear magnetic test signal and generate a first induction signal according to the first nuclear magnetic test signal;

The second coil includes a second transmitting coil and a second receiving coil, and the second transmitting coil is configured to receive a second nuclear magnetic test signal and generate a second induction signal according to the second nuclear magnetic test signal; the second receiving coil The coil is arranged corresponding to the second transmitting coil, and is configured to collect a second induction signal generated by the second transmitting coil;

The first front-end circuit is connected to the first coil and is configured to generate the first NMR test signal and collect the first induction signal; the second front-end circuit is connected to the second coil and is configured to generate The second NMR test signal.

Description of drawings

FIG. 1 is a schematic structural diagram of a dual-core radio frequency coil system provided in Embodiment 1 of the present application;

2A is a schematic structural diagram of a first coil and a second transmitting coil of a dual-core radio frequency coil system provided in Embodiment 1 of the present application;

2B is a schematic structural diagram of the first coil and the second transmitting coil of another dual-core radio frequency coil system provided in Embodiment 1 of the present application;

3 is a schematic circuit diagram of a first coil and a first front-end circuit of a dual-core radio frequency coil system provided in Embodiment 2 of the present application;

4 is a schematic circuit diagram of a second transmitting coil and a second front-end circuit of a dual-core radio frequency coil system provided in Embodiment 2 of the present application;

FIG. 5 is a schematic circuit diagram of a second receiving coil of a dual-core radio frequency coil system provided in Embodiment 2 of the present application.

Detailed ways

The application will be described below in conjunction with the accompanying drawings and embodiments. The specific embodiments described herein are for illustration of the application only. For ease of description, only parts relevant to the present application are shown in the drawings.

Embodiment one

Fig. 1 is a schematic structural diagram of a dual-core radio frequency coil system provided in Embodiment 1 of the present application; Fig. 2A is a schematic structural diagram of the first coil and the second transmitting coil of a dual-core radio frequency coil system provided in Embodiment 1 of the present application; Fig. 2B is a schematic structural diagram of the first coil and the second transmitting coil of another dual-core radio frequency coil system provided in Embodiment 1 of the present application.

As shown in Figure 1, a dual-core radio frequency coil system includes: a first coil 110, a second coil 210, a first front-end circuit 120 and a second front-end circuit 220; the first coil 110 and the second coil 210 Together around a coil support frame to form a single-layer nested structure; the first coil 110 is set to receive a first nuclear magnetic test signal and generate a first induction signal according to the first nuclear magnetic test signal; the second The coil 210 includes a second transmitting coil 211 and a second receiving coil 212, the second transmitting coil 211 is configured to receive a second nuclear magnetic test signal and generate a second induction signal according to the second nuclear magnetic test signal; The coil 212 is arranged corresponding to the second transmitting coil 211, and is configured to collect the second induction signal generated by the second transmitting coil 211; the first front-end circuit 120 is connected to the first coil 110, and is configured to generate the second induction signal generated by the second transmitting coil 211; The first nuclear magnetic test signal and collect the first induction signal; the second front-end circuit 220 is connected to the second coil 210 and configured to generate the second nuclear magnetic test signal.

Optionally, the axis of the first coil 110 coincides with the axis of the second transmitting coil 211, the central point of the axis of the first coil 110 coincides with the central point of the axis of the second transmitting coil 211, and the The first coil 110 is offset by a preset angle relative to the second transmitting coil 211 along the azimuth direction.

Optionally, the length of the legs of the first coil 110 is greater than the length of the legs of the second transmitting coil 211 , and the second transmitting coil 211 is sleeved outside the first coil 110 .

The first coil 110 is an orthogonal birdcage structure for transmitting and receiving. The first coil 110 includes a plurality of parallel leg segments. 210 adopts a separate design, and the second coil 210 includes a second transmitting coil 211 and a second receiving coil 212, wherein the second transmitting coil 212 is a birdcage structure, and the second receiving coil 212 is composed of a two-channel loop coil; the transmitting coil adopts a bird cage structure. Cage structure, which effectively produces a uniform B1+ field across the head of the transmitting coil. As shown in FIG. 2A, the first coil 110 and the second coil 210 are co-wrapped on a coil support frame to form a single-layer nested structure, and the central axis of the second transmitting coil 211 coincides with the central axis of the first coil 110. And the center points of the axes coincide with each other, and the first coil 110 is offset by a preset angle relative to the second transmitting coil 211 in the azimuth direction. As shown in FIG. 2B , the first coil 110 is offset by 22.5° relative to the second transmitting coil 211 , through the offset of the first coil 110 relative to the second transmitting coil 211, the problem of mutual interference between the inner and outer coil arrays is solved, the two coils are independently tuned and matched, and a uniform transmitting field of two frequencies is realized; wherein, the first coil The leg length of 110 is longer than the leg length of the second transmitting coil 211 , and the second transmitting coil 211 is sleeved on the outside of the first coil 110 .

In this implementation, the first coil is a 1H nuclide coil, and the second transmitting coil is a 2H nuclide coil. The two nuclide coils are independently tuned and matched to achieve a uniform emission field of two frequencies. The first coil receives the first NMR test signal and generates the first induction signal according to the first NMR test signal, and the second transmitting coil receives the second NMR test signal. test the signal and generate a second induction signal according to the second NMR test signal, and the second receiving coil receives the second induction signal generated by the second transmitting coil. When the first coil is working, the DC bias current is input into the second transmitting coil so that the second transmitting coil is in a detuned state, and the quadrature channel of the first coil is connected in series with the filter to reduce the pair The influence of the second transmitting coil avoids mutual interference between different coils. Through the combination of two different coil structures and signal excitation acquisition methods, the signal excitation acquisition chain covering the frequency required for imaging, the body coil has a large spatial distribution, can generate a uniform B1 field in a specific area, and the surface coil is more close Combined with the surface of the measured object, it has the advantage of higher SNR.

In the technical solution of this embodiment, a dual-core radio frequency coil system includes: a first coil, a second coil, a first front-end circuit and a second front-end circuit; the first coil and the second coil are jointly surrounded on a coil support frame, A single-layer nested structure is formed; the first coil is configured to receive the first nuclear magnetic test signal and generate a first induction signal according to the first nuclear magnetic test signal; the second coil includes a second transmitting coil and a second receiving coil, and the second transmitting coil Set to receive the second nuclear magnetic test signal and generate a second induction signal according to the second nuclear magnetic test signal; the second receiving coil is set correspondingly to the second transmitting coil, and is set to collect the second induction signal generated by the second transmitting coil; the first front end The circuit is connected to the first coil, and is set to generate the first nuclear magnetic test signal and collect the first induction signal; the second front-end circuit is connected to the second coil, and is set to generate the second nuclear magnetic test signal, so as to solve the difference between the two coil circuits. Nuclide channel interference, mutual interference between excitation and receiving channels, and uneven radio frequency magnetic field, to achieve uniform excitation of dual-nuclei signals in the region of interest and high-sensitivity acquisition of weak nuclide signals.

Embodiment two

Figure 3 is a schematic circuit diagram of the first coil and the first front-end circuit of a dual-core radio frequency coil system provided in Embodiment 2 of the present application; Figure 4 is a second transmitting coil of a dual-core radio frequency coil system provided in Embodiment 2 of the present application and a schematic circuit diagram of a second front-end circuit; FIG. 5 is a schematic circuit diagram of a second receiving coil of a dual-core radio frequency coil system provided in Embodiment 2 of the present application.

On the basis of the above technical solution, as shown in FIG. 3, optionally, the first coil 110 includes a plurality of first coil units, and the plurality of first coil units are connected in sequence, and adjacent to the first coil unit The tail end of the first first coil unit is connected to the head end of the second first coil unit; the first coil 110 also includes two channels, and each channel includes a first balun BN1, so The first balun BN1 includes a capacitor C1 and a balun B1, the balun B1 and the capacitor C1 are connected in series, the capacitor C1 is connected to the first coil unit, and the balun B1 is connected to The first front-end circuit 120, the first balun BN adjusts the capacitor C1 to match the resonant frequency to the corresponding operating frequency.

The first coil 110 comprises 8 loops (the first coil unit), and the first coil 110 adopts the structure of 8 leg segments, and each leg segment uses a width of 6 mm and a copper strip of 0.1 mm in thickness as a conductor, as shown in Figure 3, Taking two of the loops as an example for illustration, the first loop 111 includes the first leg segment S1, the second leg segment S2, capacitor C11A and capacitor C11B, and the second loop 112 includes the second leg segment S2, the third leg segment S3, Capacitor C12A and capacitor C12B, the first loop 111 and the second loop 112 share the second leg segment S2; the first end of the first leg segment S1 is connected in series with the capacitor C11A to the first end of the second leg segment S2, the first leg segment S1 The second end of the second leg series capacitor C11B to the second end of the second leg segment S2, the first end of the second leg segment S2 series capacitor C12A to the first end of the third leg segment S3, the second end of the second leg segment S2 A capacitor C12B is connected in series to the second end of the third leg segment S3. The first coil 110 is also grounded through two capacitors C, the tuning and matching of the first coil 110 is realized by adjusting the capacitance on the end ring and the matching capacitance of the two channels, and a non-magnetic variable capacitor is connected in parallel on the end ring as a balancing capacitor , used to compensate the structural difference in the coil manufacturing process and the asymmetry caused by the capacitance error.

The first coil 110 also includes two channels, and each channel includes a first balun BN1. The first coil 110 is connected to the first front-end circuit 120 through two channels. The circuit 120 receives the first nuclear magnetic test signal and generates a first induction signal according to the first nuclear magnetic test signal, and transmits the first induction signal back to the first front-end circuit 120 through two channels, and the first balanced-unbalanced converter BN1 is controlled by the capacitor C1 Composed with Balun B1, for example: use non-magnetic semi-steel coaxial cable to wind 2 turns of Balun B1, use capacitor C1 in series on the back, adjust the capacitor C1 to match the resonant frequency to the corresponding operating frequency, due to the shielding layer of the coaxial line The common mode current will be induced on the circuit board, which will easily cause interference to the signal, cause the deresonance of the coil, and even cause burns to the imaging living body in severe cases. The first balun BN can minimize the outer shielding of the coaxial cable layer common-mode current.

Optionally, the first front-end module 120 includes: a first power divider S1, two amplifiers (P1 and P2), two TR switching switches K and two filters LB, and the first power divider S1 Set to split the nuclear magnetic test signal input into the first power divider S1 into two first nuclear magnetic test signals, the first power divider S1 is connected to the two TR switch K, and the two TR switch K Connect with two filter LBs respectively, the first NMR test signal of two roads passes respectively in the described first coil 110 by described two TR switching switches K, described two filters LB; Two described amplifiers (P1 and P2) respectively receive the two first induction signals generated by the first coil 110 to amplify and output.

As shown in Figure 3, during the test, the two TR switches K are automatically connected to the first power divider S1, and the first power divider S1 splits the nuclear magnetic test signal input into the first power divider S1 into two first power dividers. A nuclear magnetic test signal is input into the first coil 110 through the two TR switches K and the two filters LB; when receiving the induction signal, the two TR switches K are automatically connected to the two amplifiers (P1 and P2), the two amplifiers (P1 and P2) amplify the received two first sensing signals and output them.

As shown in Figure 4 and Figure 5, optionally, the second transmitting coil 211 includes a plurality of second transmitting coil units 211A; the second receiving coil 212 includes two ring-shaped second coil receiving units (212A and 212B ), the second coil receiving unit uses a copper strip as a conductor.

The second transmitting coil 211 adopts a birdcage coil structure, and the second receiving coil 212 adopts a loop structure, which is composed of two ring-shaped second coil receiving units, and each second coil receiving unit uses a copper strip with a width of 5mm and a thickness of 0.15mm As a conductor, each second coil receiving unit is matched to 50 ohms and tuned to the corresponding operating frequency. The components in each second coil receiving unit circuit are evenly distributed to generate a uniform current in the coil circuit. The second receiving coil 212 By adjusting the geometric spacing between the two second coil receiving units, thereby adjusting the overlapping geometric area, the coupling between the two second coil receiving units can be minimized. The working state of the second coil is controlled by the input current of the leg section and the diode of the detuning circuit of the receiving part, so as to realize the conversion of transmitting and receiving.

Optionally, the second transmitting coil 211 further includes two channels, each channel includes a second balun BN2, and the second balun BN2 includes a capacitor C2 and a balun B2, The balun B2 is connected in series with the capacitor C2, the capacitor C2 is connected to the second transmitting coil unit 211A, the balun B2 is connected to the second front-end circuit 220, and the second balun BN2 matches the resonant frequency to the corresponding operating frequency by adjusting the capacitor C2; the second front-end circuit 220 includes a second power divider S2, which is configured to split the nuclear magnetic test signal input into the second power divider S2 into two first Two NMR test signals.

The second transmitting coil 211 also includes two channels, each channel includes a second balun BN2, the second transmitting coil 211 is connected to the second front-end circuit 220 through two channels, and the second front-end circuit 220 includes a second The power divider S2, the second front-end circuit 220 splits the nuclear magnetic test signal input into the second power divider S2 into two second nuclear magnetic magnetic test signals and transmits them to the second transmitting coil 211 for testing, and the second transmitting coil 211 according to the first The second nuclear magnetic test signal generates the second induction signal. The second balanced-unbalanced converter BN2 is composed of capacitor C2 and balun B2. For example: use non-magnetic semi-steel coaxial cable to wind 2 turns of balun B2, and use capacitor C2 in series on the back , by adjusting the capacitor C2 to match the resonant frequency to the corresponding working frequency, since the common mode current will be induced on the shielding layer of the coaxial line, it is easy to cause interference to the signal, causing the de-resonance of the coil, and in severe cases, it will also affect the imaging living body To cause burnout, the balun BN2 minimizes common-mode currents in the outer shield of the coaxial cable.

Optionally, the second transmitting coil 211 includes N transmitting loops, where N is greater than or equal to 2; the transmitting loop 211A includes four leg segments, an inductor L1, an inductor L2, a diode D1, a diode D2, a capacitor C3 and a capacitor C4 The first end of the first leg segment S1 is connected to the anode of the diode D1, the second end of the first leg segment S1 is connected to the second end of the capacitor C3; the cathode of the diode D1 is connected to the second leg segment The first end of S2, the second end of the second leg segment S2 is connected to the first end of the capacitor C4; the second end of the capacitor C4 is connected to the first end of the third leg segment S3, the third leg segment S3 The second end of the leg segment S3 is connected to the cathode of the diode D2; the anode of the diode D2 is connected to the first end of the fourth leg segment S4; the second end of the fourth leg segment S4 is connected to the first end of the capacitor C3 One end; the first end a1 and the second end a2 of the inductance L1 are connected in parallel to the first leg segment S1, the first end b1 and the second end b2 of the inductance L2 are connected in parallel to the second On the leg segment S2: the first ends of the N inductors L1 of the N transmitting loops are commonly connected to the bias circuit, and the first ends of the N inductors L2 of the N transmitting loops are commonly grounded.

Exemplarily, the second transmitting coil 211 includes 8 transmitting loops, each loop is composed of 4 leg segments, and each loop uses a copper strip with a width of 5 mm and a thickness of 0.15 mm as a conductor, as shown in FIG. 4 , with One of the loops is taken as an example for illustration. The first loop 211A includes the first leg segment S1, the second leg segment S2, the third leg segment S3, the fourth leg segment S4, the capacitor C3, and the capacitor C4; the inductance L1 of the 8 transmitting loops The first ends a1 of the inductance L2 of the eight transmitting loops are commonly connected to the bias circuit, and the first ends b1 of the inductors L2 of the eight transmitting loops are commonly grounded. The second transmitting coil 211 is also grounded through two capacitors C, the tuning and matching of the second transmitting coil 211 is realized by adjusting the capacitance on the end ring and the matching capacitance of the two channels, and the nonmagnetic variable capacitor is connected in parallel on the end ring as The balance capacitor is used to compensate the structural difference in the coil manufacturing process and the asymmetry caused by the capacitance error.

Optionally, the second coil receiving unit includes a preamplifier P3, a first parallel resonance trap circuit, a second parallel resonance trap circuit and a receiving coil L5, and the preamplifier P3 is placed at a distance from the receiving coil A quarter wavelength of L5 is used to receive the second induction signal, and the first parallel resonance trap circuit and the second parallel resonance trap circuit are set to protect the preamplifier P3; the first The parallel resonance trap circuit includes: an inductor L3, an inductor L4, a capacitor C5, and a diode D3. The cathode of the diode D3 is connected to the preamplifier P3, and the anode of the diode D3 is connected to the first end of the inductor L3 and the The first end of the L4, the second end of the inductance L3 is connected to the receiving coil L5 through the capacitor C5, and the second end of the inductance L4 is connected to the receiving coil L5; the second parallel resonance trap The circuit includes: a capacitor C5 and a coaxial cable, the first end of the coaxial cable is connected to the preamplifier, and the second end of the coaxial cable is connected to the receiving coil L5 through the capacitor C5.

As shown in FIG. 5 , the second receiving coil 212 includes two second coil receiving units ( 212A and 212B ), and the two second coil receiving units have the same configuration. This embodiment takes one second coil receiving unit as an example for illustration. The second coil receiving unit 212A includes a preamplifier P3, a first parallel resonant trap circuit, a second parallel resonant trap circuit, and a receiving coil L5. The preamplifier P3 is placed at a quarter wavelength away from the receiving coil L5 to receive the second induction signal, and a first parallel resonant trap circuit and a second parallel resonant circuit are set between the receiving coil L5 and the preamplifier P3 A trap circuit to suppress unbalanced currents on the coaxial cable to protect the preamplifier P3. The first parallel resonance trap circuit includes: inductor L3, inductor L4, capacitor C5, and diode D3, the first parallel resonance trap circuit corresponds to the operating frequency of the receiving coil L5; the first parallel resonance trap circuit is relative to the second parallel resonance The trap circuit is set close to the receiving coil L5, and the second parallel resonance trap circuit includes: a capacitor C5 and a coaxial cable, the first end h of the coaxial cable is connected to the preamplifier, and the second end g of the coaxial cable is connected in series with the capacitor C5 Connected to the receiving coil L5, the third end i of the coaxial cable is commonly grounded with the cathode of the diode D3 and the inverting input end of the amplifier. In the project, the coaxial cable is wound, which is equivalent to an inductor, and capacitors are connected in parallel at both ends. The outer shielding layer and the capacitor are equivalent to a parallel resonant circuit. The trap is realized at the frequency corresponding to the resonance, and the resonant frequency is matched by adjusting the capacitor C5. To the corresponding operating frequency, the common mode current of different frequencies is suppressed. In the actual test, in order to reduce the interference of the magnetic field generated by the radio frequency trap inductance on the radio frequency coil magnetic field, and to prevent the external environment from affecting the radio frequency trap inductance, it is necessary to assemble the radio frequency trap on the receiving coil in a shielding box.

The receiving coil L5 is composed of four sections of wires and four capacitors in series, wire c, capacitor C6, wire d, capacitor C9, wire e, capacitor C7, wire f and capacitor C8 are connected in series in sequence, capacitor C8 is connected with wire c to form a ring Receive coil L5.

Optionally, the dual-core radio frequency coil system also includes: an electromagnetic shielding device; the electromagnetic shielding device is covered by a layer of copper foil on the acrylic, and the copper foil is evenly divided into two parts along the direction of the main magnetic field, and the adjacent copper foil A plurality of patch capacitors are welded on the gap, and the electromagnetic shielding device is placed at a preset distance above the first coil and the second coil; the electromagnetic shielding device is connected to the first coil and the second coil The second coil is set to pass through the stationary main magnetic field and the gradient field at the audio frequency to prevent the passage of the radio frequency field.

In order to avoid electromagnetic interference from other hardware components of the MRI scanner such as gradient coils and shim coils, and to maintain the tuning conditions of the inner coils of the magnet, the dual-core radio frequency coil system also includes: an electromagnetic shielding device connected to the first coil and the second coil Second coil. The electromagnetic shielding device is equivalent to a low-pass filter, which can pass the static main magnetic field and the gradient field at the audio frequency, and prevent the passage of the radio frequency field. The electromagnetic shielding device is composed of a layer of copper foil covered on acrylic and multiple chip capacitors welded on the adjacent copper foil gap, and multiple 1nF chip capacitors with large values are welded on the adjacent copper foil gap Supported RF shielding placed 2cm above the first and second coil arrays reduces radiation losses and minimizes eddy currents without increasing the geometric overall height of the coil housing and without damaging loop components field distribution.

The influence of the high-frequency coil on the low-frequency coil and the working state of weak nuclides are respectively controlled by filters and detuning circuits, which avoids electromagnetic interference between different nuclides, and solves the problem of uneven radio frequency magnetic field at high frequencies and different nuclides. Interaction and electromagnetic interference problems. On the basis of current control tuning detuning, high-sensitivity acquisition of binuclear signal excitation and weak nuclide signals in the region of interest can be realized.

Claims

A dual-core radio frequency coil system, comprising: a first coil, a second coil, a first front-end circuit and a second front-end circuit;

The first coil and the second coil are wound together on a coil support frame to form a single-layer nested structure;

The first coil is configured to receive a first nuclear magnetic test signal and generate a first induction signal according to the first nuclear magnetic test signal;

The second coil includes a second transmitting coil and a second receiving coil, and the second transmitting coil is configured to receive a second nuclear magnetic test signal and generate a second induction signal according to the second nuclear magnetic test signal; the second receiving coil The coil is arranged corresponding to the second transmitting coil, and is configured to collect a second induction signal generated by the second transmitting coil;

The first front-end circuit is connected to the first coil and is configured to generate the first NMR test signal and collect the first induction signal; the second front-end circuit is connected to the second coil and is configured to generate The second NMR test signal.
The dual-core radio frequency coil system according to claim 1, wherein the axis of the first coil coincides with the axis of the second transmitting coil, and the center point of the axis of the first coil coincides with the axis of the second transmitting coil The center points coincide, and the first coil is offset by a preset angle in the azimuth direction relative to the second transmitting coil.
The dual-core radio frequency coil system according to claim 1, wherein the length of the legs of the first coil is greater than the length of the legs of the second transmitting coil, and the second transmitting coil is sheathed outside the first coil .
The dual-core radio frequency coil system according to claim 1, wherein the first coil includes a plurality of first coil units, and the plurality of first coil units are connected in sequence, and the first coil unit adjacent to the first coil unit The tail end of a coil unit is connected to the head end of the second first coil unit;

The first coil also includes two channels, each channel includes a first balun, the first balun includes a capacitor C1 and a balun B1, and the balun B1 and the The capacitor C1 is connected in series, the capacitor C1 is connected to the first coil unit, the balun B1 is connected to the first front-end circuit, and the first balun is configured to adjust the capacitor C1 so that The resonant frequency is matched to the corresponding operating frequency.
The dual-core radio frequency coil system according to claim 4, wherein the first front-end module comprises: a first power divider, two amplifiers, two TR switches and two filters, the first power divider It is connected with the two TR switches, the two TR switches are respectively connected with the two filters, and the first power divider is set to split the nuclear magnetic test signal input into the first power divider. Divided into two first nuclear magnetic test signals, the two first nuclear magnetic test signals are respectively input into the first coil through the two TR switches and the two filters; the two amplifiers are set amplifying and outputting the two channels of first induction signals generated by the first coil respectively.
The dual-core radio frequency coil system according to claim 1, wherein the second transmitting coil comprises a plurality of second transmitting coil units; the second receiving coil comprises two annular second coil receiving units, and the second coil The receiving unit uses copper strips as conductors.
The dual-core radio frequency coil system according to claim 6, wherein the second transmitting coil further includes two channels, each channel includes a second balun, and the second balun includes Capacitor C2 and balun B2, the balun B2 and the capacitor C2 are connected in series, the capacitor C2 is connected to the second transmitting coil unit, the balun B2 is connected to the second front-end circuit, and the first Two balanced-unbalanced converters are configured to match the resonant frequency to the corresponding operating frequency by adjusting the capacitor C2;

The second front-end circuit includes a second power divider configured to split the nuclear magnetic test signal input into the second power divider into two second nuclear magnetic test signals.
The dual-core radio frequency coil system according to claim 6, wherein the plurality of second transmitting coil units are N transmitting loops, and N is greater than or equal to 2; the transmitting loop includes four leg sections, an inductor L1, an inductor L2, Diode D1, diode D2, capacitor C3 and capacitor C4;

The first end of the first leg segment among the four leg segments is connected to the anode of the diode D1, and the second end of the first leg segment is connected to the second end of the capacitor C3;

The cathode of the diode D1 is connected to the first end of the second leg segment of the four leg segments, and the second end of the second leg segment is connected to the first end of the capacitor C4;

The second end of the capacitor C4 is connected to the first end of the third leg segment among the four leg segments, and the second end of the third leg segment is connected to the cathode of the diode D2;

The anode of the diode D2 is connected to the first end of the fourth leg segment among the four leg segments; the second end of the fourth leg segment is connected to the first end of the capacitor C3;

The first end and the second end of the inductor L1 are connected in parallel to the first leg segment, and the first end and the second end of the inductor L2 are connected in parallel to the second leg segment;

The first ends of the N inductors L1 of the N transmitting loops are commonly connected to the bias circuit, and the first ends of the N inductors L2 of the N transmitting loops are commonly grounded.
The dual-core radio frequency coil system according to claim 6, wherein the second coil receiving unit includes a preamplifier, a first parallel resonance trap circuit, a second parallel resonance trap circuit and a receiving coil, and the preamplifier Placed at a quarter wavelength away from the receiving coil, set to receive the second induction signal, the first parallel resonant trap circuit and the second parallel resonant trap circuit are set to protect the front amplifier;

The first parallel resonant trap circuit includes: an inductor L3, an inductor L4, a capacitor C5, and a diode D3. The cathode of the diode D3 is connected to the preamplifier, and the anode of the diode D3 is connected to the first electrode of the inductor L3. One end and the first end of the L4, the second end of the inductance L3 is connected to the receiving coil through the capacitor C5, and the second end of the inductance L4 is connected to the receiving coil;

The second parallel resonance trap circuit includes: the capacitor C5 and a coaxial cable, the first end of the coaxial cable is connected to the preamplifier, and the second end of the coaxial cable passes through the capacitor C5 Connect the receiving coil.
The dual-core radio frequency coil system according to claim 1, wherein the dual-core radio frequency coil system further comprises: an electromagnetic shielding device;

The electromagnetic shielding device is covered by a layer of copper foil on the acrylic, and the layer of copper foil is evenly divided into two parts along the main magnetic field direction of the dual-core radio frequency coil system, and a plurality of patches are welded on the copper foil gap Composed of capacitors, the electromagnetic shielding device is placed at a preset distance above the first coil and the second coil;

The electromagnetic shielding device is connected to the first coil and the second coil, and is configured to prevent the radio frequency field from passing through the static main magnetic field and the gradient field at the audio frequency.