Low-noise amplifier and multi-nuclear magnetic resonance imaging radio frequency coil

Abstract

A low-noise amplifier and a multi-nuclear magnetic resonance imaging radio frequency coil. The low-noise amplifier matches a low-noise impedance with a source impedance by means of a multi-frequency noise matching circuit (131), and transforms input impedances of a plurality of frequency bands to a low pure resistance, so as to suppress a coupling current of a coil array, and then nuclear magnetic resonance signals of the plurality of frequency bands undergo primary amplification and secondary amplification by means of a first-stage amplification circuit (12) and a second-stage amplification circuit (14). After each amplification, impedance matching between a preceding-stage circuit and a subsequent-stage circuit is performed by means of an impedance matching circuit, so as to achieve the purposes of improving the transmission gain of the received nuclear magnetic resonance signals of the plurality of frequency bands and reducing the noise coefficient of the nuclear magnetic resonance signals, thereby solving the technical problem in the prior art where decoupling coil arrays that receive a plurality of frequency bands requires a separate channel for each frequency, resulting in increased size and cost.

Description

A low-noise amplifier and a magnetic resonance multinucleus imaging radio frequency coil Technical Field

[0001] This application relates to the field of low-noise amplifier technology, and in particular to a low-noise amplifier and a magnetic resonance multinuclear imaging radio frequency coil. Background Technology

[0002] Existing magnetic resonance low-noise amplifiers are all single-frequency narrowband (https: / / www.wantcominc.com / WMM_series.htm), and while existing multi-frequency or broadband matching circuits can achieve low-noise, high-gain amplification across multiple frequency bands, existing technologies can be found in the following patents: Saihua Lin; Anup Savla; Mounir Youssef Bohsali, Dual-band low noise amplifier [P]. US: US9692368B2, 2017-06-27; https: / / www.wantcominc.com / WBA_series_LNA.htm. However, the existing technologies disclosed in these patents are geared towards applications outside the field of magnetic resonance, lack low input impedance characteristics, and cannot be used for decoupling of coil arrays.

[0003] The existing dual-tuned or multi-tuned coil arrays use a single-frequency low-input-impedance low-noise amplifier for each channel and each frequency, which results in a significant increase in the number of low-noise amplifiers, as well as increased size and cost.

[0004] Deterioration in isolation between channels necessitates the addition of extra filtering and isolation circuitry, resulting in complex circuit structures, increased losses, and negatively impacting imaging performance.

[0005] Summary of the Invention

[0006] The purpose of this application is to provide a low-noise amplifier to solve the technical problem in the prior art that when decoupling coil arrays that receive multiple frequency bands, it is necessary to use a separate channel for each frequency to achieve decoupling, which leads to increased size and cost.

[0007] In a first aspect, embodiments of this application provide a low-noise amplifier for magnetic resonance multinuclear imaging. The low-noise amplifier includes a signal receiving end, a signal output end, a multi-frequency noise matching circuit, a first-stage amplification branch, and a second-stage amplification branch. The first-stage amplification branch includes a first-stage amplification circuit and a first-stage impedance matching circuit. The second-stage amplification branch includes a second-stage amplification circuit and a second-stage impedance matching circuit.

[0008] The signal receiving end is used to receive nuclear magnetic resonance signals of multiple frequency bands from the coil array;

[0009] The multi-frequency noise matching circuit is used to match the low-noise impedance and the source impedance, and transform the input impedance of multiple frequency bands to a low pure resistance to suppress the coupling current of the coil array. The low-noise impedance is the impedance when the noise figure of the low-noise amplifier is less than 0.5dB, and the source impedance is the signal source impedance in the low-noise amplifier.

[0010] The first-stage amplifier circuit is used to initially amplify the nuclear magnetic resonance signals of multiple frequency bands to obtain a first amplified signal;

[0011] The first-stage impedance matching circuit is used to perform impedance matching between the first-stage amplifier circuit and the second-stage amplifier circuit, so as to improve the transmission gain of the first amplified signal and reduce the noise figure of the first amplified signal.

[0012] The second-stage amplifier circuit is used to amplify the first amplified signal again to obtain a second amplified signal; and,

[0013] The second-stage impedance matching circuit is used to perform impedance matching between the first-stage amplifier circuit and the signal output terminal, so as to improve the transmission gain of the second amplified signal and reduce the noise figure of the second amplified signal.

[0014] In one alternative embodiment, the input terminal of the multi-frequency noise matching circuit is connected to the signal receiving terminal, and the output terminal of the multi-frequency noise matching circuit is connected to the input terminal of the first-stage amplifier circuit; the output terminal of the first-stage amplifier circuit is connected to the input terminal of the first-stage impedance matching circuit, and the output terminal of the first-stage impedance matching circuit is connected to the input terminal of the second-stage amplifier circuit; the output terminal of the second-stage amplifier circuit is connected to the input terminal of the second-stage impedance matching circuit, and the output terminal of the second-stage impedance matching circuit is connected to the signal output terminal.

[0015] In one alternative embodiment, the low-noise amplifier further includes N stages of amplification branches, each stage of which is disposed between the first stage amplification branch and the second stage amplification branch; or,

[0016] Each stage of the amplification branch is positioned between the first stage amplification branch and the multi-frequency noise matching circuit; or...

[0017] Each stage of the amplification branch is located between the second stage amplification branch and the signal output terminal.

[0018] In one alternative, the first-stage impedance matching circuit is a broadband impedance matching circuit or a multi-frequency impedance matching circuit.

[0019] When the first-stage impedance matching circuit is a broadband impedance matching circuit, the second-stage impedance matching circuit is also a broadband impedance matching circuit.

[0020] When the first-stage impedance matching circuit is a multi-frequency impedance matching circuit, the second-stage impedance matching circuit is also a multi-frequency impedance matching circuit.

[0021] In one optional embodiment, the multi-frequency noise matching circuit includes a first capacitor, a second capacitor, a first inductor, and a second inductor. The first terminal of the first capacitor is the input terminal of the multi-frequency noise matching circuit, used to input the nuclear magnetic resonance signals of multiple frequency bands. The second terminal of the first capacitor is connected to the first terminal of the second capacitor and the first terminal of the first inductor, respectively. The first terminal of the second inductor is connected to the second terminal of the second capacitor and the second terminal of the first inductor, respectively, and the connection node is the output terminal of the multi-frequency noise matching circuit. The second terminal of the second inductor is grounded.

[0022] In one optional embodiment, the first-stage amplifier circuit includes a first amplifier tube operating state control circuit and a first amplifier tube. The first amplifier tube operating state control circuit includes a first control branch and a second control branch. The first amplifier tube has an input terminal, an output terminal, a first control terminal, and a second control terminal. The first control terminal of the first amplifier tube is connected to a first terminal of the first control branch, and the second control terminal of the first amplifier tube is connected to a second terminal of the first control branch. The input terminal of the first amplifier tube is the input terminal of the first-stage amplifier circuit, and the output terminal of the first amplifier tube is connected to the input terminal of the second control branch. The output terminal of the second control branch is the output terminal of the first-stage amplifier circuit.

[0023] The first control branch is used to adjust the stability coefficient of the first amplifying tube;

[0024] The second control branch is used to adjust the noise figure and gain of the first amplifier tube;

[0025] The first amplifying tube is used to initially amplify the nuclear magnetic resonance signals of multiple frequency bands to obtain the first amplified signal under the control of the first control branch and the second control branch.

[0026] In one optional embodiment, the first control branch includes a third capacitor, a fourth capacitor, and a first resistor. The first terminal of the third capacitor is connected to the first terminal of the first resistor, with the connection point being the first terminal of the first control branch. The second terminals of the third capacitor, the fourth capacitor, and the first resistor are all grounded. The second terminal of the fourth capacitor is the second terminal of the first control branch. The second control branch includes a second resistor, a third resistor, a fifth capacitor, and a sixth capacitor. The first terminal of the second resistor is the input terminal of the second control branch. The second terminal of the second resistor is connected to the first terminals of both the fifth and third capacitors, with the connection point being the output terminal of the second control branch. The second terminal of the third resistor is connected to the first terminal of the sixth capacitor, and the second terminals of both the fifth and sixth capacitors are grounded.

[0027] In one alternative embodiment, the first-stage impedance matching circuit includes a third inductor, a fourth inductor, a seventh capacitor, and an eighth capacitor. The first terminal of the third inductor is the input terminal of the first-stage impedance matching circuit. The second terminal of the third inductor is connected to the first terminal of the fourth inductor, the first terminal of the seventh capacitor, and the first terminal of the eighth capacitor, respectively. The second terminal of the seventh inductor is grounded. The second terminal of the eighth inductor is connected to the second terminal of the fourth inductor, and the connection node is the output terminal of the first-stage impedance matching circuit.

[0028] In one optional embodiment, the second-stage amplifier circuit includes a second amplifier tube operating state control circuit and a second amplifier tube; the second amplifier tube includes a first terminal, a second terminal, and a third terminal; the second amplifier tube operating state control circuit includes a first control terminal, a second control terminal, and an output terminal; the first terminal of the second amplifier tube is the input terminal of the second-stage amplifier circuit; the second terminal of the second amplifier tube is connected to the first control terminal of the second amplifier tube operating state control circuit; the third terminal of the second amplifier tube is connected to the second control terminal of the second amplifier tube operating state control circuit; the output terminal of the second amplifier tube operating state control circuit is the output terminal of the second-stage amplifier circuit.

[0029] The second amplifier transistor operating state control circuit is used to adjust the operating state of the second amplifier transistor to improve the gain.

[0030] The second amplifying transistor is used to amplify the first amplified signal again to obtain the second amplified signal under the control of the second amplifying transistor operating state control circuit.

[0031] In one optional embodiment, the second amplifier tube operating state control circuit includes a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a ninth capacitor, a tenth capacitor, and an eleventh capacitor. The first terminal of the fourth resistor is connected to the first terminal of the fifth resistor and the first terminal of the ninth capacitor, and the connection node is the first control terminal of the second amplifier tube operating state control circuit. The second terminals of the fourth resistor, the tenth capacitor, and the eleventh capacitor are all grounded. The first terminal of the sixth resistor is connected to the second terminal of the ninth capacitor, and the connection node is the second control terminal of the second amplifier tube operating state control circuit. The second terminal of the sixth resistor is connected to the second terminal of the tenth capacitor and the first terminal of the seventh resistor, and the connection node is the output terminal of the second amplifier tube operating state control circuit. The second terminal of the seventh resistor is connected to the second terminal of the eleventh capacitor.

[0032] In one alternative embodiment, the second-stage impedance matching circuit includes a power supply, a fifth inductor, a sixth inductor, a seventh inductor, an eighth inductor, a twelfth capacitor, and a thirteenth capacitor. The first terminal of the fifth inductor is the input terminal of the second-stage impedance matching circuit, and the second terminal of the fifth inductor is connected to the first terminals of the sixth inductor, the twelfth capacitor, and the thirteenth capacitor, respectively. The first terminal of the seventh inductor is connected to the second terminals of the sixth inductor and the thirteenth capacitor, respectively, and the second terminal of the seventh inductor is connected to the first terminal of the eighth inductor. The connection node is the output terminal of the second-stage impedance matching circuit. The second terminal of the eighth inductor is connected to the positive terminal of the power supply, and the negative terminal of the power supply is grounded.

[0033] Secondly, this application provides a magnetic resonance multi-core imaging radio frequency coil, which includes N nuclear magnetic resonance signal receiving terminals, N dual-tuning units, and corresponding N low-noise amplifiers as described above, where N is an integer greater than or equal to 1. Each dual-tuning unit includes a first dual-tuning circuit, a dual-frequency matching circuit, a first tuning capacitor, and a second tuning capacitor. The first terminal of the first dual-tuning circuit is connected to the first terminal of the first tuning capacitor, and the first terminal of the first dual-tuning circuit is connected to the first terminal of the second tuning capacitor. The first terminal of the dual-frequency matching circuit is connected to the second terminal of the first tuning capacitor, and the second terminal of the dual-frequency matching circuit is connected to the second terminal of the second tuning capacitor. The output terminal of the dual-frequency matching circuit is connected to the input terminal of the low-noise amplifier, and the output terminal of the low-noise amplifier is connected to the nuclear magnetic resonance signal receiving terminals.

[0034] The first dual-tuning circuit and the dual-frequency matching circuit of the Nth dual-tuning unit are used to form a resonant high impedance with the Nth low-noise amplifier to suppress coupling current.

[0035] In one alternative, when N is greater than or equal to 2, the Nth dual-tuning unit is arranged to overlap with the (N-1)th dual-tuning unit structure.

[0036] When N equals 2, the two dual-tuned units form a dual-tuned coil array unit.

[0037] This application embodiment uses a multi-frequency noise matching circuit to match the low-noise impedance and the source impedance, and transforms the input impedance of multiple frequency bands to low pure resistance to suppress the coupling current of the coil array. Then, the input NMR signals of multiple frequency bands are initially amplified and further amplified through a first-stage amplifier circuit and a second-stage amplifier circuit. After each amplification, an impedance matching circuit is used to match the impedance between the output of the previous stage circuit and the input of the next stage circuit. This aims to improve the transmission gain of the received NMR signals of multiple frequency bands and reduce the noise figure of the NMR signals. This solves the technical problem in the prior art where decoupling of coil arrays receiving multiple frequency bands requires a separate channel for each frequency, resulting in increased volume and cost.

[0038] The above description is merely an overview of the technical solutions of the embodiments of this application. In order to better understand the technical means of the embodiments of this application and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of this application more obvious and understandable, specific implementation methods of this application are described below. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 shows a schematic diagram of a first embodiment of the low-noise amplifier provided in this application;

[0041] Figure 2 shows a circuit diagram of the low-noise amplifier provided in this application;

[0042] Figure 3 shows a schematic diagram of the simulation effect of the gain and output matching frequency of the low-noise amplifier provided in this application;

[0043] Figure 4 shows a schematic diagram of the noise figure-frequency simulation effect of the low-noise amplifier provided in this application;

[0044] Figure 5 shows a schematic diagram of the simulation effect of the input impedance-frequency of the low-noise amplifier provided in this application;

[0045] Figure 6 shows a schematic diagram of the stability coefficient-frequency simulation effect of the low-noise amplifier provided in this application;

[0046] Figure 7 shows a schematic diagram of a module of an embodiment of the magnetic resonance multinuclear imaging radio frequency coil provided in this application;

[0047] Figure 8 shows a schematic diagram of another embodiment of the magnetic resonance multinuclear imaging radio frequency coil provided in this application;

[0048] Figure 9 shows a schematic diagram of the common side decoupling structure of another embodiment of the magnetic resonance multi-core imaging radio frequency coil provided by the present invention. Detailed Implementation

[0049] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0050] The following describes the existing technology of multinuclear magnetic resonance imaging:

[0051] Multinuclear magnetic resonance imaging (MRI) has a wide range of functions. First, it can provide high-resolution anatomical images, helping doctors to accurately diagnose diseases. Second, by observing the metabolism of different nuclides, it can assess the functional status of tissues or organs, such as the brain, heart, and liver. This is crucial for the early diagnosis and treatment of diseases. For example, sodium magnetic resonance imaging (23Na-MRI) offers a non-invasive way to quantify sodium content in tissues, with applications covering almost the entire human body, providing assistance in the clinical diagnosis and treatment of tumors, neurological diseases, and degenerative diseases. (Zaric, O., Juras, V., Szomolanyi, P., Schreiner, M., Raudner, M., Giraudo, C., & Trattnig, S. Frontiers of Sodium MRI Revisited: From Cartilage to Brain Imaging. Journal of Magnetic Resonance Imaging 2020). Due to the minimal endogenous interference and wide chemical shift range of fluorine nuclei, fluorine magnetic resonance imaging (19F-MRI) has significant advantages in soft tissue resolution and tissue penetration. (Li Y, Cui J, Li C, Zhou H, Chang J, Aras O, An F. 19 F MRI Nanotheranostics for Cancer Management: Progress and Prospects. Chem Med Chem. 2022 Feb 16; 17(4):e202100701). Currently, multinucleus magnetic resonance imaging systems can use dual-tuned or multi-tuned coil arrays to achieve simultaneous reception of hydrogen nuclei and one or more non-hydrogen nuclei using only one coil structure.The method to implement a dual-tuned coil is to add a "frequency divider notch filter". The "frequency divider notch filter" is usually a series-parallel combination circuit of inductor and capacitor. It can be added to the loop of a single-frequency coil to split a single resonant frequency in two. By adjusting the inductance and capacitance of the "frequency divider notch filter", the two resonant frequencies can be made to cover the frequencies of hydrogen nuclei and one non-hydrogen nuclei, so that two nuclear magnetic resonance signals can be received simultaneously (Shen GX, Boada FE, Thulborn KR. Dual-frequency, dual-quadrature, birdcage RF coil design with identical B1 pattern for sodium and proton imaging of the human brain at 1.5 T. Magn Reson Med 1997; 38:717–25; Rowland BC, Driver ID, Tachrount M, et al. Whole brain 31P MRSI at 7T with a dual-tuned receive array. Magn Reson Med 2020; 83:765–75.).

[0052] The low-noise amplifier (LNA) is a key component in a magnetic resonance imaging (MRI) system. Its main function is to amplify the nuclear magnetic resonance (NMR) signal received from the receiving coil to improve the signal strength and quality, thereby obtaining a more accurate and clearer image. The NMR signal received at the coil end is very weak, only on the order of microvolts, and requires a low-noise amplifier to amplify it to the order of millivolts. Therefore, the LNA typically requires a gain of over 25 dB and a noise figure of less than 0.5. In addition, the LNA also requires a low input impedance, which, combined with the matching circuit at the coil end, forms a resonant high impedance, thereby decoupling the coil array units and improving imaging performance (Roemer PB, Edelstein WA, Hayes CE, Souza SP, Mueller OM. The NMR phased array. Magn Reson Med. 1990 Nov; 16(2):192-225.).

[0053] Current dual-tuned or multi-tuned coil arrays use a single-frequency low-input-impedance low-noise amplifier for each channel and each frequency. This results in a significant increase in the number of low-noise amplifiers, leading to increased size and cost. It also worsens the isolation between channels, requiring additional filtering and isolation circuits. This results in a complex circuit structure, increased losses, and negatively impacts imaging performance.

[0054] This application provides a low-noise amplifier to solve the technical problem in the prior art that the need to use a separate channel for each frequency to achieve decoupling when decoupling coil arrays that receive multiple frequency bands leads to increased size and cost.

[0055] Figure 1 shows a block diagram of a first embodiment of the low-noise amplifier of this application. The low-noise amplifier includes a signal receiving terminal 20, a signal output terminal 21, a multi-frequency noise matching circuit 131, a first-stage amplification branch, and a second-stage amplification branch. The first-stage amplification branch includes a first-stage amplification circuit 12 and a first-stage impedance matching circuit 133; the second-stage amplification branch includes a second-stage amplification circuit 14 and a second-stage impedance matching circuit 135.

[0056] The signal receiving end 20 receives NMR signals from multiple frequency bands from the coil array. The multi-frequency noise matching circuit 131 matches the low-noise impedance and source impedance, and transforms the input impedance of the multiple frequency bands to low pure resistance to suppress coupling current in the coil array. The low-noise impedance is the impedance when the noise figure of the low-noise amplifier is less than 0.5 dB, and the source impedance is the signal source impedance in the low-noise amplifier. The first-stage amplifier circuit 12 initially amplifies the NMR signals from multiple frequency bands to obtain a first amplified signal. The first-stage impedance matching circuit 133 performs impedance matching between the first-stage amplifier circuit 12 and the second-stage amplifier circuit 14 to improve the transmission gain of the first amplified signal and reduce its noise figure. The second-stage amplifier circuit 14 further amplifies the first amplified signal to obtain a second amplified signal. The second-stage impedance matching circuit 135 performs impedance matching between the first-stage amplifier circuit 12 and the signal output end 21 to improve the transmission gain of the second amplified signal and reduce its noise figure. The above solution improves the transmission gain of received NMR signals across multiple frequency bands and reduces the noise figure of the NMR signals by using an impedance matching circuit after each amplification to match the impedance between the preceding and following stages. This solves the technical problem in the prior art where decoupling coil arrays that receive multiple frequency bands requires a separate channel for each frequency, resulting in increased size and cost.

[0057] In particular, the aforementioned low-noise amplifier offers superior technical performance for multi-nuclear magnetic resonance imaging (MMRI). The circuit design reduces the size and cost of the low-noise amplifier, and by increasing transmission gain and lowering the signal noise figure, it avoids the losses and interference associated with complex filtering and isolation circuits, thereby improving the imaging performance of MMRI. Specifically, it can simultaneously achieve low-noise reception and high-gain amplification across multiple frequency bands, such as low-noise reception and high-gain amplification of hydrogen nuclei and multiple non-hydrogen nuclei.

[0058] In the above embodiments, referring to FIG1, the following connection relationship can be adopted to achieve the above technical solution:

[0059] The input terminal of the multi-frequency noise matching circuit 131 is connected to the signal receiving terminal 20, and the output terminal of the multi-frequency noise matching circuit 131 is connected to the input terminal of the first-stage amplifier circuit 12; the output terminal of the first-stage amplifier circuit 12 is connected to the input terminal of the first-stage impedance matching circuit 133, and the output terminal of the first-stage impedance matching circuit 133 is connected to the input terminal of the second-stage amplifier circuit 14; the output terminal of the second-stage amplifier circuit 14 is connected to the input terminal of the second-stage impedance matching circuit 135, and the output terminal of the second-stage impedance matching circuit 135 is connected to the signal output terminal 21.

[0060] In an optional embodiment, the low-noise amplifier further includes N amplification branches, each amplification branch being disposed between the first amplification branch and the second amplification branch.

[0061] In an optional embodiment, each amplification branch is disposed between the first amplification branch and the multi-frequency noise matching circuit 131.

[0062] In an optional embodiment, each amplification branch is disposed between the second amplification branch and the signal output terminal 21.

[0063] According to the above three embodiments, the added amplification branch can be set between any amplification branch, or between the signal output terminal 21 and the amplification branch, or between the signal output terminal 21 and the amplification branch, so that the amplification branch can be set as needed to obtain a sufficiently high transmission gain.

[0064] In an optional embodiment, the first-stage impedance matching circuit 133 is a broadband impedance matching circuit or a multi-frequency impedance matching circuit.

[0065] When the first-stage impedance matching circuit 133 is a broadband impedance matching circuit, the second-stage impedance matching circuit 135 is also a broadband impedance matching circuit.

[0066] When the first-stage impedance matching circuit 133 is a multi-frequency impedance matching circuit, the second-stage impedance matching circuit 135 is also a multi-frequency impedance matching circuit.

[0067] The multi-frequency noise matching circuit 131 can match the low-noise impedance and source impedance of the amplifier in multiple frequency bands to achieve multi-frequency low-noise reception, and can also achieve low input impedance characteristics at multiple frequencies, thereby improving the transmission gain of the received NMR signals in multiple frequency bands. The impedance matching circuit is used for impedance matching between the preceding amplifier tubes and between the amplifier tubes and the output terminal. This improves the transmission gain of the received NMR signals in multiple frequency bands.

[0068] In an optional embodiment, referring to FIG2, the multi-frequency noise matching circuit 131 includes a first capacitor C1, a second capacitor C2, a first inductor L1, and a second inductor L2. The first terminal of the first capacitor C1 is the input terminal of the multi-frequency noise matching circuit 131, used to input nuclear magnetic resonance signals of multiple frequency bands. The second terminal of the first capacitor C1 is connected to the first terminal of the second capacitor C2 and the first terminal of the first inductor L1, respectively. The first terminal of the second inductor is connected to the second terminal of the second capacitor C2 and the second terminal of the first inductor L1, respectively. The connection node is the output terminal of the multi-frequency noise matching circuit 131, and the second terminal of the second inductor is grounded.

[0069] In this circuit, a parallel circuit of the second capacitor C2 and the first inductor L1 is inserted in the middle of the L-shaped single-frequency matching circuit composed of the first capacitor C1 and the second inductor L2. This achieves multi-frequency impedance matching. This circuit can match the low-noise impedance and source impedance of the amplifier in two frequency bands, enabling multi-frequency low-noise reception. It can also transform the input impedance of the two frequency bands to very low pure resistance, directly connecting it to the tuning circuit in the dual-tuned or multi-tuned coil array of the magnetic resonance multi-core imaging RF coil. This, in conjunction with the generation of resonant high impedance, suppresses the coupling current in the coil circuit, achieving decoupling of the dual-tuned coil array.

[0070] It should be noted that the above embodiment of the multi-frequency noise matching circuit 131 is a dual-band multi-frequency noise matching circuit 131, used to illustrate the effect. In actual use, a multi-frequency noise matching circuit can be selected as needed.

[0071] In an optional embodiment, referring to FIG2, the first-stage amplifier circuit 12 includes a first amplifier tube operating state control circuit and a first amplifier tube 132. The first amplifier tube operating state control circuit includes a first control branch 121 and a second control branch 122. The first amplifier tube 132 has an input terminal, an output terminal, a first control terminal, and a second control terminal. The first control terminal of the first amplifier tube 132 is connected to the first terminal of the first control branch 121, and the second control terminal of the first amplifier tube 132 is connected to the second terminal of the first control branch 121. The input terminal of the first amplifier tube 132 is the input terminal of the first-stage amplifier circuit 12, and the output terminal of the first amplifier tube 132 is connected to the input terminal of the second control branch 122. The output terminal of the second control branch 122 is the output terminal of the first-stage amplifier circuit 12.

[0072] Specifically, the first control branch 121 adjusts the operating state of the first amplifying tube 132 to reduce the noise figure and increase the gain. The second control branch 122 adjusts the operating state of the first amplifying tube 132 to reduce the noise figure and increase the gain. Under the control of the first control branch 121 and the second control branch 122, the first amplifying tube 132 initially amplifies the nuclear magnetic resonance signals of multiple frequency bands to obtain the first amplified signal. At this time, the controlled first amplifying tube 132 has low noise, high gain, and good stability.

[0073] Optionally, the first amplifying tube 132 is a low-noise, stable-performance amplifying tube to initially amplify the very weak multi-frequency nuclear magnetic resonance signals received by the coil terminal connected to the signal receiving terminal 20.

[0074] In an optional embodiment, referring to FIG2, the first control branch 121 includes a third capacitor C3, a fourth capacitor C4, and a first resistor R1. The first end of the third capacitor C3 is connected to the first end of the first resistor, and the connection node is the first end of the first control branch 121. The second ends of the third capacitor C3, the fourth capacitor C4, and the first resistor are all grounded. The second end of the fourth capacitor C4 is the second end of the first control branch 121. The second control branch 122 includes a second resistor R2, a third resistor R3, a fifth capacitor C5, and a sixth capacitor C6. The first end of the second resistor R2 is the input end of the second control branch 122. The second end of the second resistor R2 is connected to the first end of the fifth capacitor C5 and the first end of the third resistor R3, and the connection node is the output end of the second control branch 122. The second end of the third resistor R3 is connected to the first end of the sixth capacitor C6. The second ends of the fifth capacitor C5 and the sixth capacitor C6 are both grounded.

[0075] In the above scheme, the third capacitor C3, the fourth capacitor C4, and the first resistor R1 are used as a negative feedback circuit to adjust the stability coefficient of the first amplifier tube.

[0076] In an optional embodiment, referring to FIG2, the first-stage impedance matching circuit 133 includes a third inductor L3, a fourth inductor L4, a seventh capacitor C7, and an eighth capacitor C8. The first terminal of the third inductor L3 is the input terminal of the first-stage impedance matching circuit 133. The second terminal of the third inductor L3 is connected to the first terminal of the fourth inductor L4, the first terminal of the seventh capacitor C7, and the first terminal of the eighth capacitor, respectively. The second terminal of the seventh inductor is grounded. The second terminal of the eighth inductor is connected to the second terminal of the fourth inductor L4, and the connection node is the output terminal of the first-stage impedance matching circuit 133.

[0077] In the above scheme, a parallel circuit consisting of an eighth capacitor C8 and a fourth inductor L4 is connected in series after an L-shaped single-frequency matching circuit composed of the third inductor L3 and the seventh capacitor C7 to achieve the function of multi-frequency impedance matching. This allows for dual-frequency impedance matching of the output terminal of the first-stage amplifier and the input terminal of the second-stage amplifier, thereby ensuring the gain of the first-stage amplifier and reducing transmission loss.

[0078] In an optional embodiment, referring to FIG2, the second-stage amplifier circuit 14 includes a second amplifier tube operating state control circuit and a second amplifier tube 134; the second amplifier tube 134 includes a first terminal, a second terminal, and a third terminal; the second amplifier tube operating state control circuit includes a first control terminal, a second control terminal, and an output terminal; the first terminal of the second amplifier tube 134 is the input terminal of the second-stage amplifier circuit 14; the second terminal of the second amplifier tube 134 is connected to the first control terminal of the second amplifier tube operating state control circuit; the third terminal of the second amplifier tube 134 is connected to the second control terminal of the second amplifier tube operating state control circuit; the output terminal of the second amplifier tube operating state control circuit is the output terminal of the second-stage amplifier circuit 14.

[0079] The second amplifier tube operating state control circuit adjusts the operating state of the second amplifier tube 134 to increase the gain. Under the control of the second amplifier tube operating state control circuit, the second amplifier tube 134 amplifies the first amplified signal again to obtain the second amplified signal.

[0080] In an optional embodiment, referring to FIG2, the second amplifier tube operating state control circuit includes a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, a ninth capacitor C9, a tenth capacitor C10, and an eleventh capacitor C11. The first end of the fourth resistor R4 is connected to the first end of the fifth resistor R5 and the first end of the ninth capacitor C9, and the connection node is the first control terminal of the second amplifier tube operating state control circuit. The second end of the fourth resistor R4, the first end of the tenth capacitor C10, and the first end of the eleventh capacitor are all grounded. The first end of the sixth resistor R6 is connected to the second end of the ninth capacitor C9, and the connection node is the second control terminal of the second amplifier tube operating state control circuit. The second end of the sixth resistor R6 is connected to the second end of the tenth capacitor C10 and the first end of the seventh resistor R7, and the connection node is the output terminal of the second amplifier tube operating state control circuit. The second end of the seventh resistor R7 is connected to the second end of the eleventh capacitor.

[0081] In this circuit, the fourth resistor R4, the fifth resistor R5, and the ninth capacitor C9 serve as negative feedback to adjust the stability coefficient of the second amplifier transistor. The sixth resistor R6, the seventh resistor R7, the tenth capacitor C10, and the eleventh capacitor C11 are used to adjust the DC operating point of the second amplifier transistor, maintaining low noise and high gain at both frequencies. The second amplifier transistor operating state control circuit regulates the operating state of the second-stage amplifier transistor, stably amplifying the received signal again to obtain a sufficiently high gain.

[0082] In an optional embodiment, referring to FIG2, the low noise amplifier further includes an RF choke L8 and a power supply V_DC. The first end of the RF choke L8 is connected to the output of the second-stage impedance matching circuit 135, the second end of the RF choke L8 is connected to the positive terminal of the power supply V_DC, and the negative terminal of the power supply V_DC is grounded.

[0083] In an optional embodiment, referring to FIG2, the second-stage impedance matching circuit 135 includes a fifth inductor L5, a sixth inductor L6, a seventh inductor L7, a twelfth capacitor C12, and a thirteenth capacitor C13. The first terminal of the fifth inductor L5 is the input terminal of the second-stage impedance matching circuit 135, and the second terminal of the fifth inductor L5 is connected to the first terminal of the sixth inductor L6, the first terminal of the twelfth capacitor C12, and the first terminal of the thirteenth capacitor, respectively. The first terminal of the seventh inductor L7 is connected to the second terminal of the sixth inductor L6 and the second terminal of the thirteenth capacitor, respectively, and the second terminal of the seventh inductor L7 is the output terminal of the second-stage impedance matching circuit 135.

[0084] The power supply V_DC simultaneously powers both the first and second amplifier transistors 134. The eighth inductor L8 acts as a radio frequency choke, blocking radio frequency signals and protecting the power supply V_DC. The second-stage impedance matching circuit 135 includes the fifth inductor L5, the sixth inductor L6, the seventh inductor L7, the twelfth capacitor C12, and the thirteenth capacitor C13.

[0085] Based on the above implementation scheme, signal simulation was performed using the circuit diagram shown in Figure 2 as a reference, and the simulation results of the low-noise amplifier on the Advanced Design System (ADS) software were obtained. This dual-frequency low-noise amplifier operates simultaneously at two frequencies, 33.8MHz and 123MHz, which correspond to the frequencies of the hydrogen nuclei and sodium nuclei in the 3T magnetic resonance system, respectively. As shown in Figure 3, where S(2,1) represents reflection, m4 has a frequency of 33.80MHz and a reflection of -15.915dB, m14 has a frequency of 123.0MHz and a reflection of -16.382dB, and S(2,2) represents the gain ratio, m13 has a frequency of 33.80MHz and a gain ratio of 29.312dB; m3 has a frequency of 123.0MHz and a gain ratio of 30.029dB. The output of this dual-frequency low-noise amplifier is well matched at both frequencies, with reflections less than -15.9dB. In addition, this dual-frequency low-noise amplifier achieves high gains of 29.3dB and 30dB at the two frequencies, respectively.

[0086] Figure 4 shows the noise figure of the dual-frequency amplifier. The frequency of m11 is 33.80MHz and the noise figure is 0.484; the frequency of m12 is 123.0MHz and the noise figure is 0.043. The noise figure of 33.8MHz is 0.484 and the noise figure of 123MHz is 0.043.

[0087] The Smith chart of the input impedance of this dual-frequency low-noise amplifier is shown in Figure 5. The frequency of m9 is 33.80MHz, with an impedance of 50*(2.738E-4+j6.929E-4)Ω; the frequency of m10 is 123.0MHz, with an impedance of 50*(0.040+j2.197E-4)Ω. The real part of the input impedance at both frequencies is less than 2Ω, and the imaginary part is close to zero.

[0088] Figure 6 shows the simulation results of the stability coefficient of the dual-frequency low-noise amplifier. The frequency of m1 is 33.80MHz, and the stability coefficient is 1.319; the frequency of m2 is 123.0MHz, and the stability coefficient is 149.085. The results show that the stability coefficients of both frequencies are greater than 1, indicating that the dual-frequency low-noise amplifier is operating in a stable state.

[0089] This application also proposes a magnetic resonance multinuclear imaging radio frequency coil. Referring to FIG7, the magnetic resonance multinuclear imaging radio frequency coil includes N dual-tuning units, N nuclear magnetic resonance signal receiving terminals 20, and corresponding N low-noise amplifiers as described above, where N is an integer greater than or equal to 1. Each dual-tuning unit includes a first dual-tuning circuit 10A, a dual-frequency matching circuit 10B, a first tuning capacitor 111A, and a second tuning capacitor 111B. The first terminal of the first dual-tuning circuit 10A is connected to the first terminal of the first tuning capacitor 111A, and the first terminal of the first dual-tuning circuit 10A is connected to the first terminal of the second tuning capacitor 111B. The first terminal of the dual-frequency matching circuit 10B is connected to the second terminal of the first tuning capacitor 111A, and the second terminal of the dual-frequency matching circuit 10B is connected to the second terminal of the second tuning capacitor 111B. The output terminal of the dual-frequency matching circuit 10B is connected to the input terminal of the low-noise amplifier, and the output terminal of the low-noise amplifier is connected to the nuclear magnetic resonance signal receiving terminal 20. The nuclear magnetic resonance signal can be connected to a magnetic resonance spectrometer or other signal processing equipment.

[0090] In this circuit, the dual-frequency matching circuit 10B of the Nth dual-tuned unit forms a resonant high impedance with the Nth low-noise amplifier to suppress coupling current. This achieves decoupling.

[0091] It should be noted that, since the magnetic resonance multinuclear imaging radio frequency coil of this application can implement all embodiments of the low noise amplifier, the magnetic resonance multinuclear imaging radio frequency coil of this application has all the beneficial effects of the low noise amplifier, which will not be elaborated here.

[0092] In an optional embodiment, referring to FIG8, when N is greater than or equal to 2, the Nth dual-tuning unit and the (N-1)th dual-tuning unit are structurally overlapped;

[0093] When N is greater than or equal to 2, two or more dual-tuned units form a dual-tuned coil array.

[0094] In the above embodiments, the overlapping arrangement means that the first dual-tuning unit encloses a first tuning region and the second dual-tuning unit encloses a second tuning region. When arranging the circuit structure, the first dual-tuning unit and the second dual-tuning unit partially overlap at adjacent locations, so that the magnetic flux passing through and returning to the overlapping region cancels each other out. Thus, mutual inductance can be suppressed by structurally overlapping each other, thereby achieving decoupling.

[0095] In addition to the above solutions, mutual inductance can also be suppressed and decoupling achieved by setting decoupling structures on the common side or by using capacitor and inductor decoupling structures. Here, the common side refers to the two adjacent sides. Referring to Figure 9, the common side means that two units share a conductor at an adjacent point, and coupling is suppressed by adjusting the capacitance value on the common side. Capacitor and inductor decoupling structures are implemented by adding capacitors or inductors between the two units.

[0096] It is understood that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, 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, they should be considered to be within the scope of this specification.

[0097] The above are merely preferred embodiments of this application, and only specifically describe the technical principles of this application. These descriptions are only for explaining the principles of this application and should not be construed as limiting the scope of protection of this application in any way. Based on this interpretation, any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, as well as other specific embodiments of this application that can be conceived by those skilled in the art without creative effort, should be included within the scope of protection of this application.

[0098] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of this application may be practiced without these specific details. Similarly, for the sake of brevity and to aid in understanding one or more aspects of the application, in the above description of exemplary embodiments of this application, various features of the embodiments are sometimes grouped together in a single embodiment, figure, or description thereof. The claims, which follow the detailed description, are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the application.

[0099] Those skilled in the art will understand that the modules in the device of the embodiment can be adaptively changed and placed in one or more devices different from that embodiment. Modules, units, or components in the embodiment can be combined into a single module, unit, or component, and further, they can be divided into multiple sub-modules, sub-units, or sub-components, except that at least some of such features and / or processes or units are mutually exclusive.

[0100] It should be noted that the above embodiments are illustrative of this application and not restrictive, and those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word “” does not exclude the presence of elements or steps not listed in the claims. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. This application can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names. The steps in the above embodiments, unless otherwise specified, should not be construed as limiting the order of execution.

Claims

1. A low-noise amplifier, characterized in that, For magnetic resonance multinuclear imaging, the low-noise amplifier includes a signal receiving end, a signal output end, a multi-frequency noise matching circuit, a first-stage amplification branch, and a second-stage amplification branch; the first-stage amplification branch includes a first-stage amplification circuit and a first-stage impedance matching circuit; the second-stage amplification branch includes a second-stage amplification circuit and a second-stage impedance matching circuit. The signal receiving end is used to receive nuclear magnetic resonance signals of multiple frequency bands from the coil array; The multi-frequency noise matching circuit is used to match the low-noise impedance and the source impedance, and transform the input impedance of multiple frequency bands to a low pure resistance to suppress the coupling current of the coil array. The low-noise impedance is the impedance when the noise figure of the low-noise amplifier is less than 0.5dB, and the source impedance is the signal source impedance in the low-noise amplifier. The first-stage amplifier circuit is used to initially amplify the nuclear magnetic resonance signals of multiple frequency bands to obtain a first amplified signal; The first-stage impedance matching circuit is used to perform impedance matching between the first-stage amplifier circuit and the second-stage amplifier circuit, so as to improve the transmission gain of the first amplified signal and reduce the noise figure of the first amplified signal. The second-stage amplifier circuit is used to amplify the first amplified signal again to obtain a second amplified signal; and, The second-stage impedance matching circuit is used to perform impedance matching between the first-stage amplifier circuit and the signal output terminal, so as to improve the transmission gain of the second amplified signal and reduce the noise figure of the second amplified signal.

2. The low-noise amplifier according to claim 1, characterized in that, The input terminal of the multi-frequency noise matching circuit is connected to the signal receiving terminal, and the output terminal of the multi-frequency noise matching circuit is connected to the input terminal of the first-stage amplifier circuit; the output terminal of the first-stage amplifier circuit is connected to the input terminal of the first-stage impedance matching circuit, and the output terminal of the first-stage impedance matching circuit is connected to the input terminal of the second-stage amplifier circuit; the output terminal of the second-stage amplifier circuit is connected to the input terminal of the second-stage impedance matching circuit, and the output terminal of the second-stage impedance matching circuit is connected to the signal output terminal.

3. The low-noise amplifier according to claim 2, characterized in that, The low-noise amplifier further includes N stages of amplification branches, each stage of which is disposed between the first stage amplification branch and the second stage amplification branch; or, Each stage of the amplification branch is positioned between the first stage amplification branch and the multi-frequency noise matching circuit; or... Each stage of the amplification branch is located between the second stage amplification branch and the signal output terminal.

4. The low-noise amplifier according to claim 1, characterized in that, The first-stage impedance matching circuit is a broadband impedance matching circuit or a multi-frequency impedance matching circuit. When the first-stage impedance matching circuit is a broadband impedance matching circuit, the second-stage impedance matching circuit is also a broadband impedance matching circuit. When the first-stage impedance matching circuit is a multi-frequency impedance matching circuit, the second-stage impedance matching circuit is also a multi-frequency impedance matching circuit.

5. The low-noise amplifier according to claim 2, characterized in that, The multi-frequency noise matching circuit includes a first capacitor, a second capacitor, a first inductor, and a second inductor. The first terminal of the first capacitor is the input terminal of the multi-frequency noise matching circuit, used to input the nuclear magnetic resonance signals of multiple frequency bands. The second terminal of the first capacitor is connected to the first terminal of the second capacitor and the first terminal of the first inductor, respectively. The first terminal of the second inductor is connected to the second terminal of the second capacitor and the second terminal of the first inductor, respectively. The connection node is the output terminal of the multi-frequency noise matching circuit. The second terminal of the second inductor is grounded.

6. The low-noise amplifier according to claim 2, characterized in that, The first-stage amplifier circuit includes a first amplifier tube operating state control circuit and a first amplifier tube. The first amplifier tube operating state control circuit includes a first control branch and a second control branch. The first amplifier tube has an input terminal, an output terminal, a first control terminal, and a second control terminal. The first control terminal of the first amplifier tube is connected to the first terminal of the first control branch, and the second control terminal of the first amplifier tube is connected to the second terminal of the first control branch. The input terminal of the first amplifier tube is the input terminal of the first-stage amplifier circuit, and the output terminal of the first amplifier tube is connected to the input terminal of the second control branch. The output terminal of the second control branch is the output terminal of the first stage amplifier circuit; The first control branch is used to adjust the stability coefficient of the first amplifying tube; The second control branch is used to adjust the noise figure and gain of the first amplifier tube; The first amplifying tube is used to initially amplify the nuclear magnetic resonance signals of multiple frequency bands to obtain the first amplified signal under the control of the first control branch and the second control branch.

7. The low-noise amplifier according to claim 6, characterized in that, The first control branch includes a third capacitor, a fourth capacitor, and a first resistor. The first terminal of the third capacitor is connected to the first terminal of the first resistor, and the connection node is the first terminal of the first control branch. The second terminals of the third capacitor, the fourth capacitor, and the first resistor are all grounded. The second terminal of the fourth capacitor is the second terminal of the first control branch. The second control branch includes a second resistor, a third resistor, a fifth capacitor, and a sixth capacitor. The first terminal of the second resistor is the input terminal of the second control branch. The second terminal of the second resistor is connected to the first terminals of the fifth capacitor and the third resistor, respectively, and the connection node is the output terminal of the second control branch. The second terminal of the third resistor is connected to the first terminal of the sixth capacitor. The second terminals of the fifth capacitor and the sixth capacitor are both grounded.

8. The low-noise amplifier according to claim 2, characterized in that, The first-stage impedance matching circuit includes a third inductor, a fourth inductor, a seventh capacitor, and an eighth capacitor. The first terminal of the third inductor is the input terminal of the first-stage impedance matching circuit. The second terminal of the third inductor is connected to the first terminal of the fourth inductor, the first terminal of the seventh capacitor, and the first terminal of the eighth capacitor. The second terminal of the seventh inductor is grounded. The second terminal of the eighth inductor is connected to the second terminal of the fourth inductor, and the connection node is the output terminal of the first-stage impedance matching circuit.

9. The low-noise amplifier according to claim 2, characterized in that, The second-stage amplifier circuit includes a second amplifier tube operating state control circuit and a second amplifier tube. The second amplifier tube includes a first terminal, a second terminal, and a third terminal. The second amplifier tube operating state control circuit includes a first control terminal, a second control terminal, and an output terminal. The first terminal of the second amplifier tube is the input terminal of the second-stage amplifier circuit. The second terminal of the second amplifier tube is connected to the first control terminal of the second amplifier tube operating state control circuit. The third terminal of the second amplifier tube is connected to the second control terminal of the second amplifier tube operating state control circuit. The output terminal of the second amplifier tube operating state control circuit is the output terminal of the second-stage amplifier circuit. The second amplifier transistor operating state control circuit is used to adjust the operating state of the second amplifier transistor to improve the gain. The second amplifying transistor is used to amplify the first amplified signal again to obtain the second amplified signal under the control of the second amplifying transistor operating state control circuit.

10. The low-noise amplifier according to claim 9, characterized in that, The second amplifier tube operating state control circuit includes a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a ninth capacitor, a tenth capacitor, and an eleventh capacitor. The first end of the fourth resistor is connected to the first end of the fifth resistor and the first end of the ninth capacitor, and the connection node is the first control terminal of the second amplifier tube operating state control circuit. The second end of the fourth resistor, the first end of the tenth capacitor, and the first end of the eleventh capacitor are all grounded. The first end of the sixth resistor is connected to the second end of the ninth capacitor, and the connection node is the second control terminal of the second amplifier tube operating state control circuit. The second end of the sixth resistor is connected to the second end of the tenth capacitor and the first end of the seventh resistor, and the connection node is the output terminal of the second amplifier tube operating state control circuit. The second end of the seventh resistor is connected to the second end of the eleventh capacitor.

11. The low-noise amplifier according to claim 2, characterized in that, The second-stage impedance matching circuit includes a power supply, a fifth inductor, a sixth inductor, a seventh inductor, an eighth inductor, a twelfth capacitor, and a thirteenth capacitor. The first terminal of the fifth inductor is the input terminal of the second-stage impedance matching circuit. The second terminal of the fifth inductor is connected to the first terminals of the sixth inductor, the twelfth capacitor, and the thirteenth capacitor, respectively. The first terminal of the seventh inductor is connected to the second terminals of the sixth inductor and the thirteenth capacitor, respectively. The second terminal of the seventh inductor is connected to the first terminal of the eighth inductor, and their connection node is the output terminal of the second-stage impedance matching circuit. The second terminal of the eighth inductor is connected to the positive terminal of the power supply, and the negative terminal of the power supply is grounded.

12. A magnetic resonance multinuclear imaging radio frequency coil, characterized in that, The magnetic resonance multinuclear imaging radio frequency coil includes N nuclear magnetic resonance signal receiving terminals, N dual-tuning units, and corresponding N low-noise amplifiers as described in any one of claims 1-11, where N is an integer greater than or equal to 1. Each dual-tuning unit includes a first dual-tuning circuit, a dual-frequency matching circuit, a first tuning capacitor, and a second tuning capacitor. The first terminal of the first dual-tuning circuit is connected to the first terminal of the first tuning capacitor, and the first terminal of the first dual-tuning circuit is connected to the first terminal of the second tuning capacitor. The first terminal of the dual-frequency matching circuit is connected to the second terminal of the first tuning capacitor, and the second terminal of the dual-frequency matching circuit is connected to the second terminal of the second tuning capacitor. The output terminal of the dual-frequency matching circuit is connected to the input terminal of the low-noise amplifier, and the output terminal of the low-noise amplifier is connected to the nuclear magnetic resonance signal receiving terminal. The first dual-tuning circuit and the dual-frequency matching circuit of the Nth dual-tuning unit are used to form a resonant high impedance with the Nth low-noise amplifier to suppress coupling current.

13. The magnetic resonance multinuclear imaging radio frequency coil according to claim 12, characterized in that, When N is greater than or equal to 2, the Nth dual-tuning unit and the (N-1)th dual-tuning unit are arranged in an overlapping manner. When N equals 2, the two dual-tuned units form a dual-tuned coil array unit.

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