A zero-solder point flexible radio frequency coil structure for magnetic resonance imaging

Abstract

The invention discloses a zero-solder-point flexible radio frequency coil structure for magnetic resonance imaging, comprising a flexible part located in an imaging area and a non-flexible part located outside the imaging area, wherein the flexible part comprises a radio frequency resonant circuit, a transmission line and / or a common mode suppression balun located on the same flexible printed circuit board; the non-flexible part comprises at least a preamplifier and a detuned diode of a detuned circuit connected thereto; the flexible printed circuit board comprises a substrate, several sections of upper copper cladding located on the upper surface of the substrate, and several sections of lower copper cladding located on the lower surface of the substrate; the upper copper cladding forms an upper conductor, and the lower copper cladding forms a lower conductor; the overlapping upper and lower conductors and the substrate between the two together form a planar flexible capacitor. The zero-solder-point flexible radio frequency coil structure for magnetic resonance imaging of the invention has no solder joints in the imaging area, further reduces the thickness and weight of the magnetic resonance radio frequency coil, improves the softness and comfort, and greatly improves the reliability.

Description

Technical Field

[0001] The invention relates to a zero-weld-point flexible radio frequency coil structure for magnetic resonance imaging, and belongs to the technical field of magnetic resonance imaging of medical devices. Background Art

[0002] Magnetic resonance imaging is an advanced non-destructive imaging technology for the human body, which is widely used in the diagnosis of diseases in various parts of the human body. The MRI radio frequency coil is an important part of the MRI system, and its performance directly determines the quality of MRI.

[0003] With the development and advancement of magnetic resonance technology, especially in recent years, flexible radio frequency coils have become increasingly popular among doctors and patients due to their advantages such as lightness, ease of use, and high patient comfort.

[0004] See also Figure 1 A traditional flexible RF coil is a resonant circuit made of a flexible printed circuit board 1', in which a discrete ceramic capacitor 2' is welded at intervals. The detuned circuit in the resonant circuit is made of a PIN diode 3', a discrete detuned circuit ceramic capacitor 4', and a discrete detuned circuit solenoid inductor 5'. The resonant circuit and the preamplifier are usually connected by a coaxial line, one section of the coaxial line is wound into a solenoid 6', and a discrete ceramic capacitor 7' is welded in parallel to the shielding layer at both ends. The solenoid 6' and the ceramic capacitor 7' are connected in parallel to form a common-mode suppression balun.

[0005] Patents CN201810888994.3 and CN201821261853.0 disclose a magnetic resonance radio frequency coil structure using distributed capacitors, which changes discrete ceramic capacitors into planar flexible capacitors. However, other components still use discrete electrical components. Since the flexible coil needs to be bent during use, all the aforementioned discrete capacitors, discrete inductors, discrete baluns and other components and assemblies, as well as all solder joints, need to be protected by plastic shells for safety and reliability considerations. Therefore, although such a flexible coil can be bent, its bendability is still very limited, and the thickness and weight of the coil cannot be reduced. In addition, due to the presence of a large number of electronic components and solder joints, its reliability is also greatly reduced. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the prior art and provide a zero-weld-point flexible radio frequency coil structure for magnetic resonance imaging, in which there are no welds in the imaging area, the thickness and weight of the magnetic resonance radio frequency coil are further reduced, the softness and comfort are improved, and the reliability is greatly improved.

[0007] The technical solution to achieve the above object is: a zero-weld-point flexible radio frequency coil structure for magnetic resonance imaging, comprising a flexible portion located within an imaging area and a non-flexible portion located outside the imaging area, wherein:

[0008] The flexible part includes a radio frequency resonant circuit, a transmission line and / or a common mode suppression balun located on the same flexible printed circuit board;

[0009] The non-flexible part comprises at least a preamplifier and a detuning diode of a detuning circuit connected thereto;

[0010] The flexible printed circuit board comprises a substrate, a plurality of sections of upper copper clad layers located on the upper surface of the substrate, and a plurality of sections of lower copper clad layers located on the lower surface of the substrate; the upper copper clad layers form an upper conductor, and the lower copper clad layers form a lower conductor; the upper and lower conductors are staggered, and the adjacent upper and lower conductors overlap, and the overlapping upper and lower conductors and the substrate between the two together form a planar flexible capacitor;

[0011] The radio frequency resonant circuit includes a plurality of tuning capacitors, detuning circuit capacitors and signal feeding point capacitors connected in series through a plurality of conductor segments;

[0012] All tuning capacitors, detuning circuit capacitors and signal feed point capacitors are planar flexible capacitors;

[0013] All conductors are upper conductors or lower conductors on the flexible printed circuit board;

[0014] The radio frequency resonant circuit and the non-flexible part are connected via the transmission line;

[0015] The transmission line uses an upper conductor and / or a lower conductor on a flexible printed circuit board;

[0016] The common-mode suppression balun is arranged on the transmission line, and the common-mode suppression balun is composed of a planar flexible capacitor connected in parallel at two ends of a section of the transmission line through a connecting line.

[0017] The above-mentioned zero-solder point flexible radio frequency coil structure for magnetic resonance imaging, wherein the detuning circuit capacitor and the signal feeding point capacitor are mutually independent planar flexible capacitors, and one end of the detuning circuit capacitor and one end of the signal feeding point capacitor are connected via an upper conductor or a lower conductor on a flexible printed circuit board;

[0018] The transmission line includes three conductors, namely a first conductor, a second conductor and a third conductor. One end of the first conductor is connected to a conductor between the signal feeding point capacitor and the detuning circuit capacitor, and the other end is connected to the ground wire of the preamplifier; one end of the second conductor is connected to the other end of the signal feeding point capacitor, and the other end is connected to the input end of the preamplifier; one end of the third conductor is connected to the other end of the detuning circuit capacitor, and the other end is connected to the detuning diode of the detuning circuit.

[0019] The above-mentioned zero-solder-point flexible radio frequency coil structure for magnetic resonance imaging, wherein the first conductor of the transmission line is made of a lower conductor on a flexible planar printed circuit board, and the second conductor and the third conductor of the transmission line are made of two upper conductors arranged parallel to each other on the flexible printed circuit board in a one-to-one correspondence;

[0020] Two ends of one section of the first conductive line are connected in parallel with a planar flexible capacitor through a connecting line to form a common-mode suppression balun, and the connecting line is made of a lower conductor and a via located on a flexible printed circuit board.

[0021] In the above-mentioned zero-solder-point flexible radio frequency coil structure for magnetic resonance imaging, a phase shifter is arranged between the preamplifier and the transmission line.

[0022] The above-mentioned zero-solder point flexible radio frequency coil structure for magnetic resonance imaging, wherein the detuning circuit capacitor and the signal feeding point capacitor share a planar flexible capacitor, and this planar flexible capacitor is connected to the non-flexible part through a transmission line, and the transmission line includes two conductors, and the two conductors are formed by an upper conductor and a lower conductor on a flexible planar printed circuit board in a one-to-one correspondence.

[0023] The above-mentioned zero-solder point flexible radio frequency coil structure for magnetic resonance imaging, wherein the two ends of one section of a conductor of the transmission line are connected in parallel with a planar flexible capacitor through a connecting line to form a common-mode suppression balun, and the connecting line is made of a conductor and a via on a flexible printed circuit board.

[0024] In the above-mentioned zero-solder point flexible radio frequency coil structure for magnetic resonance imaging, a phase shifting and impedance matching circuit is arranged between the preamplifier and the detuning diode.

[0025] In the above-mentioned zero-weld-point flexible radio frequency coil structure for magnetic resonance imaging, a single-channel radio frequency coil is formed after one of the flexible parts and one of the non-flexible parts are connected.

[0026] The above-mentioned zero-weld-point flexible radio frequency coil structure for magnetic resonance imaging, wherein a plurality of said single-channel radio frequency coils are combined together to form a multi-channel phased array radio frequency coil;

[0027] The flexible part of each channel is made on an independent flexible printed circuit board, all the flexible printed circuit boards of multiple channels are staggered and stacked together, and all the transmission lines are gathered together and connected to the non-flexible part;

[0028] Alternatively, all flexible parts of multiple channels are combined and fabricated on a single flexible printed circuit board.

[0029] The above-mentioned zero-solder point flexible radio frequency coil structure for magnetic resonance imaging, wherein all flexible printed circuit boards in the imaging area and part of the transmission line outside the imaging area are encapsulated in a flexible cover, and all non-flexible parts outside the imaging area are encapsulated in a plastic box, and the flexible cover and the plastic box are pressed together.

[0030] Compared with the prior art, the zero-weld-point flexible radio frequency coil structure for magnetic resonance imaging of the present invention has the following advantages:

[0031] (1) There are no discrete electronic components, no solder joints, and therefore no protective plastic casing in the imaging area, so the coil can be extremely thin;

[0032] (2) The thickness and weight of the magnetic resonance radio frequency coil can be further reduced, and the softness and comfort can be improved;

[0033] (3) There are no solder joints in the imaging area, which greatly improves reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the structure of a traditional flexible radio frequency coil;

[0035] Figure 2 is a schematic structural diagram of the flexible portion located in the imaging area in the first embodiment;

[0036] Figure 3 for Figure 2 A partial enlarged schematic diagram of the transmission line and common-mode suppression balun;

[0037] Figure 4 is a circuit structure diagram of the non-flexible portion located outside the imaging area in the first embodiment;

[0038] Figure 5 is a schematic structural diagram of the flexible portion located within the imaging area in the second embodiment;

[0039] Figure 6is a circuit structure diagram of the non-flexible portion located outside the imaging area in the second embodiment;

[0040] Figure 7 This is a schematic diagram of the structure of a single-channel radio frequency coil in Embodiment 3;

[0041] Figure 8 This is a schematic diagram of the structure of a six-channel phased array RF coil in Example 3. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the technical solution of the present invention, the specific implementation methods thereof are described in detail below in conjunction with the accompanying drawings:

[0043] Embodiment 1:

[0044] See also Figure 2 , Figure 3 and Figure 4 A zero-weld-point flexible radio frequency coil structure for magnetic resonance imaging comprises a flexible portion 100 located within an imaging region and a non-flexible portion 200 located outside the imaging region.

[0045] The flexible part 100 includes a radio frequency resonant circuit 2, a transmission line 3 and a common mode suppression balun 4 (in special cases, the common mode suppression balun 4 may not be provided) located on the same flexible printed circuit board; the non-flexible part 200 includes a series-connected preamplifier 6, a detuned diode 51 of a detuned circuit 5 and a detuned circuit inductor 52, and a phase shifter 7 is provided between the transmission line 3 and the preamplifier 6.

[0046] The flexible printed circuit board includes a substrate, several sections of upper copper cladding located on the upper surface of the substrate, and several sections of lower copper cladding located on the lower surface of the substrate; the upper copper cladding forms an upper conductor 11, and the lower copper cladding forms a lower conductor 12; the adjacent upper and lower conductors overlap, and the overlapping upper and lower conductors and the substrate between them form a planar flexible capacitor. The capacitance of the planar flexible capacitor is determined by the following formula:

[0047] C=ε0*ε r *A / d (1)

[0048] In formula (1), C is the capacitance value, ε0 is the vacuum dielectric constant, and ε r is the relative dielectric constant of the substrate, A is the overlap area, and d is the thickness of the substrate. In this embodiment, a commonly used 25 micron thick polyimide is used as the substrate, and its relative dielectric constant is 3.3. Using formula (1), it can be calculated that each square millimeter of overlap area can produce a capacitance of about 1.1 pF, so it is very easy to design and manufacture a capacitance in the range of 1-100 pF commonly used in magnetic resonance radio frequency coils.

[0049] Figure 2 In order to facilitate intuitive display and understanding, the width of the lower conductor is greater than that of the upper conductor, but this is not necessarily the case in practical applications.

[0050] The RF resonant circuit 2 includes a plurality of tuning capacitors 21, detuning circuit capacitors 22 and signal feeding point capacitors 23 connected in series through a plurality of conductor segments; all tuning capacitors 21, detuning circuit capacitors 22 and signal feeding point capacitors 23 are planar flexible capacitors; all conductor connecting lines are made of upper conductors 11 or lower conductors 12 on a flexible printed circuit board; the RF resonant circuit 2 and the non-flexible part 200 are connected via a transmission line 3.

[0051] The transmission line 3 is a planar flexible transmission line, which uses an upper conductor and / or a lower conductor on a flexible printed circuit board; the common-mode suppression balun 4 is arranged on the transmission line 3, and the common-mode suppression balun 4 is composed of a planar flexible capacitor 42 connected in parallel at both ends of a section of the transmission line 3 through a connecting line 41.

[0052] In this embodiment, there are five capacitors in total on the RF resonant circuit 2 , which are three tuning capacitors 21 , one detuning circuit capacitor 22 and one signal feeding point capacitor 23 .

[0053] The detuning circuit capacitor 22 and the signal feeding point capacitor 23 are mutually independent planar flexible capacitors, and one end of the detuning circuit capacitor 22 and one end of the signal feeding point capacitor 23 are connected via a lower conductor on the flexible printed circuit board.

[0054] Please see again Figure 3 The transmission line 3 includes three conductors, namely a first conductor 31, a second conductor 32 and a third conductor 33. The first conductor 31 is made of a lower conductor on a flexible planar printed circuit board and is a reference ground wire; the second conductor 32 and the third conductor 33 of the transmission line are made of two upper conductors arranged parallel to each other on the flexible printed circuit board in a one-to-one correspondence.

[0055] Since the components such as the preamplifier 6 and the detuning circuit inductor 52 and the detuning diode 51 of the detuning circuit 5 need to be placed outside the imaging area, the transmission line 3 is relatively long, and a common-mode suppression balun 4 is usually required to be added to the transmission line 3. The two ends of one section of the first conductor 31 are connected in parallel with a planar flexible capacitor 42 through a connecting line 41 to form a common-mode suppression balun 4. The connecting line 41 is made of an upper or lower conductor and a via 44 located on a flexible printed circuit board. The inductance formed by the connecting lines 41 at both ends of the first conductor 31 resonates with the parallel planar flexible capacitor 42 to form a parallel resonant circuit, which can effectively suppress the common-mode current on the transmission line.

[0056] Please see again Figure 4One end of the first wire 31 is connected to the lower conductor between the signal feeding point capacitor 23 and the detuning circuit capacitor 22, and the other end is connected to the ground wire of the preamplifier 6, which functions similarly to the shielding wire of the coaxial line; one end of the second wire 32 is connected to the other end of the signal feeding point capacitor 23, and the other end is connected to the input end of the preamplifier 6, which functions equivalent to the RF signal line of the coaxial line; the third wire 33 functions equivalent to the detuning circuit connecting line, one end of the third wire 33 is connected to the other end of the detuning circuit capacitor 22, and the other end is connected to one end of the detuning circuit inductor 52 of the detuning circuit 5, and the other end of the detuning circuit inductor 52 is connected to the positive electrode of the detuning diode 51, and the negative electrode of the detuning diode 51 is connected to the ground wire of the preamplifier.

[0057] If the transmission line connecting the flexible resonant circuit 2 and the preamplifier 6 is relatively long, a phase shifter 7 (see FIG. Figure 4 ), the second wire 32 is connected to the input end of the phase shifter 7, and the output end of the phase shifter 7 is connected to the input end of the preamplifier 6. The first wire 31 connects the ground wires of the phase shifter 7 and the preamplifier 6.

[0058] In the first embodiment, a transmission line made of a conductor on the same flexible printed circuit board as the RF resonant circuit is used to connect not only the signal feed point capacitor 23 of the RF resonant circuit 2 and the preamplifier 6 placed outside the imaging area, but also the detuned circuit capacitor 22 located in the imaging area and the detuned circuit inductor 52 and detuned diode 51 and other components located outside the imaging area.

[0059] In order to achieve the effect of the detuned circuit, it is necessary to adjust the detuned circuit capacitor 22, the transmission line 3, and the detuned circuit inductor 52 to the frequency of the magnetic resonance system, such as 3.0T, which is usually 127.7MHz, when the detuned diode 51 is short-circuited. In this way, during the transmission of the magnetic resonance system, a high resistance is formed at both ends of the detuned circuit capacitor 22 to prevent a large radio frequency current from being generated in the resonant circuit, thereby ensuring the safety of the radio frequency coil and the patient.

[0060] For a multi-channel phased array RF coil, in order to achieve the effect of the preamplifier 6 improving the isolation between the RF coil channels, it is also necessary to adjust the signal feed point capacitor 23, the transmission line 3, the phase shifter 7 and the preamplifier 6 to the frequency of the magnetic resonance system, thereby forming a high impedance at both ends of the signal feed point capacitor 23 to reduce the coupling between the channels.

[0061] Embodiment 2:

[0062] See also Figure 5 and Figure 6A zero-solder point flexible radio frequency coil structure for magnetic resonance imaging. Different from the first embodiment, in this embodiment, the signal feeding capacitor 23 and the detuning circuit capacitor 22 share a planar flexible capacitor 20. The planar flexible capacitor 20 has both the detuning function and the signal feeding function. The planar flexible capacitor 20 is connected to the non-flexible part through a transmission line 3. In this way, the transmission line 3 only needs two conductors, one of which is made of an upper conductor on a flexible printed circuit board, and the other is made of a lower conductor on the flexible printed circuit board.

[0063] The principle is the same as that in the first embodiment. If the transmission line 3 is long, a planar flexible capacitor is connected in parallel at both ends of a lower conductor of a certain section of the transmission line 3 through two sections of connecting wires, thereby forming a common-mode suppression balun.

[0064] The other end of the transmission line 3 is connected to the detuning circuit outside the imaging area, wherein the wire made of the upper conductor is connected to one end of the detuning circuit inductor 52 of the detuning circuit, and the wire made of the lower conductor is connected to the cathode of the detuning diode 51. The principle is the same as that in the first embodiment, and when the detuning diode 51 is short-circuited, the signal feed capacitor and the detuning circuit capacitor are resonated with the transmission line and the detuning circuit inductor at the magnetic resonance system frequency.

[0065] Please see again Figure 6 Since the capacitance values ​​required by the detuning function and the signal feeding function are usually different, and since the transmission line is usually long, a phase shift and impedance matching circuit 7' needs to be added between the detuning circuit 5 and the preamplifier 6. In addition, as in the first embodiment, the planar flexible capacitor 20 that performs both the detuning function and the signal feeding function, the transmission line, the detuning circuit inductor 52, the phase shift and impedance matching circuit 7' and the preamplifier 6 should also be adjusted to the frequency of the magnetic resonance system, thereby increasing the channel isolation.

[0066] Embodiment three:

[0067] Embodiment 1 and Embodiment 2 mainly demonstrate different structures and implementations of a single RF channel of a magnetic resonance coil. Currently, a magnetic resonance RF coil is usually composed of many independent channels. This embodiment mainly demonstrates how the concept of the present invention is used to form a phased array RF coil with multiple channels.

[0068] See also Figure 7 A flexible part 100 and a non-flexible part 200 are connected to form a single-channel RF coil. Similar to the second embodiment, the signal feed capacitor 23 and the detuning circuit capacitor 23 are combined into one capacitor, and connected to the outside of the imaging area through a planar flexible transmission line and a common mode suppression balun. All connecting conductors, all capacitors, and all transmission lines on this channel are made on an independent flexible printed circuit board.

[0069] See also Figure 8 , consisting of 6 Figure 7 The single-channel RF coil shown is composed of a 6-channel phased array RF coil, which is specifically formed by combining 6 flexible parts 100 and 6 non-flexible parts 200; the flexible part of each channel is made on an independent flexible printed circuit board, and the 6 flexible printed circuit boards of the 6 channels are staggered and stacked together. In order to place all the phase shifters, detuning circuits and preamplifier components placed in the non-flexible part outside the imaging area together, it is necessary to properly adjust the transmission line routing direction and common-mode suppression balun position of each channel so that all the transmission lines are finally converged and connected to the components located in the non-flexible part outside the imaging area.

[0070] Finally, the flexible printed circuit board in the imaging area and the transmission line outside the imaging area are encapsulated in a flexible cover 300, and all the non-flexible components outside the imaging area, such as the phase shifter, the detuning circuit and the preamplifier, are encapsulated in a plastic box 400, and the flexible cover and the plastic box are pressed together. Then, the preamplifier and the detuning circuit in the plastic box are connected to the magnetic resonance system using a cable, and magnetic resonance imaging scanning can be performed.

[0071] In this way, in the entire imaging area, there is only a flexible printed circuit board, without any discrete electronic components and welding points, and the entire coil can be made extremely thin, extremely light, and extremely soft. In addition, since there are no discrete electronic components and welding points in the imaging area, there will be no magnetic problems, no active heating problems, and the safety and reliability are greatly improved.

[0072] Of course, based on the above ideas, the RF resonant circuit of the magnetic resonance RF coil can be made into various shapes and sizes to adapt to different application scenarios of different RF coils. Flexible planar transmission lines can also be made in different ways, such as two or three wires can be routed side by side on a copper layer, or can be partially overlapped, or made into a grid-like copper layer. The common-mode suppression balun on the transmission line can also be made into different shapes, such as the transmission line can be wound into an 8-shape to increase its inductance and improve the common-mode suppression effect.

[0073] In addition, the detuning circuit, phase shifter and preamplifier located outside the imaging area can also have many different designs. For example, in some cases, the inductor of the detuning circuit may need to be replaced by a capacitor; in some cases, a phase shifter is not required; in some cases, an impedance matching circuit is not required, and only the preamplifier needs to be redesigned.

[0074] For flexible printed circuit boards, each channel can be made on a separate flexible printed circuit board, or multiple channels can be combined and made on a printed circuit board. Double-sided flexible printed circuit boards can be used, and in some cases, 4 or more layers of flexible printed circuit boards can also be used.

[0075] In summary, in the zero-solder-point flexible RF coil structure for magnetic resonance imaging of the present invention, all circuits, capacitors, transmission lines, and baluns of each RF channel in the entire imaging area are made of a flexible printed circuit board, and do not require any discrete electronic components or solder points. The thickness and weight can be greatly reduced, and the softness, comfort, and reliability can be greatly improved.

[0076] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A zero-weld-point flexible radio frequency coil structure for magnetic resonance imaging, characterized in that: The method comprises a flexible portion located within an imaging region and a non-flexible portion located outside the imaging region, wherein: The flexible part includes a radio frequency resonant circuit, a transmission line and / or a common mode suppression balun located on the same flexible printed circuit board; The non-flexible part comprises at least a preamplifier and a detuning diode of a detuning circuit connected thereto; The flexible printed circuit board comprises a substrate, a plurality of sections of upper copper clad layers located on the upper surface of the substrate, and a plurality of sections of lower copper clad layers located on the lower surface of the substrate; the upper copper clad layers form an upper conductor, and the lower copper clad layers form a lower conductor; the upper and lower conductors are staggered, and the adjacent upper and lower conductors overlap, and the overlapping upper and lower conductors and the substrate between the two together form a planar flexible capacitor; The radio frequency resonant circuit includes a plurality of tuning capacitors, detuning circuit capacitors and signal feeding point capacitors connected in series through a plurality of conductor segments; All tuning capacitors, detuning circuit capacitors and signal feed point capacitors are planar flexible capacitors; All conductors are upper conductors or lower conductors on the flexible printed circuit board; The radio frequency resonant circuit and the non-flexible part are connected via the transmission line; The transmission line uses an upper conductor and / or a lower conductor on a flexible printed circuit board; The common-mode suppression balun is arranged on the transmission line, and the common-mode suppression balun is composed of a planar flexible capacitor connected in parallel at both ends of a transmission line through a connecting line. The detuned circuit capacitor and the signal feed point capacitor are mutually independent planar flexible capacitors, and one end of the detuned circuit capacitor and one end of the signal feed point capacitor are connected via an upper conductor or a lower conductor on a flexible printed circuit board; The transmission line includes three conductors, namely a first conductor, a second conductor and a third conductor. One end of the first conductor is connected to a conductor between the signal feeding point capacitor and the detuning circuit capacitor, and the other end is connected to the ground wire of the preamplifier; one end of the second conductor is connected to the other end of the signal feeding point capacitor, and the other end is connected to the input end of the preamplifier; one end of the third conductor is connected to the other end of the detuning circuit capacitor, and the other end is connected to the detuning diode of the detuning circuit.

2. The zero-weld-point flexible radio frequency coil structure for magnetic resonance imaging according to claim 1, characterized in that: The first conductor of the transmission line is made of a lower conductor on a flexible planar printed circuit board, and the second conductor and the third conductor of the transmission line are made of two upper conductors arranged parallel to each other on the flexible printed circuit board in a one-to-one correspondence; Two ends of one section of the first conductive line are connected in parallel with a planar flexible capacitor through a connecting line to form a common-mode suppression balun, and the connecting line is made of a lower conductor and a via located on a flexible printed circuit board.

3. The zero-weld-point flexible radio frequency coil structure for magnetic resonance imaging according to claim 1, characterized in that: A phase shifter is arranged between the preamplifier and the transmission line.

4. The zero-weld-point flexible radio frequency coil structure for magnetic resonance imaging according to claim 1, characterized in that: The detuned circuit capacitor and the signal feed point capacitor share a planar flexible capacitor, which is connected to the non-flexible part via a transmission line. The transmission line includes two conductors, which are formed one-to-one by an upper conductor and a lower conductor on a flexible planar printed circuit board.

5. The zero-weld-point flexible radio frequency coil structure for magnetic resonance imaging according to claim 4, characterized in that: Two ends of one section of a conductor of the transmission line are connected in parallel with a planar flexible capacitor through a connecting line to form a common-mode suppression balun, and the connecting line is made of a conductor and a via on a flexible printed circuit board.

6. The zero-weld-point flexible radio frequency coil structure for magnetic resonance imaging according to claim 4, characterized in that: A phase shift and impedance matching circuit is arranged between the preamplifier and the detuning diode.

7. The zero-weld-point flexible radio frequency coil structure for magnetic resonance imaging according to claim 1, characterized in that: A single-channel radio frequency coil is formed after the flexible part and the non-flexible part are connected.

8. The zero-weld-point flexible radio frequency coil structure for magnetic resonance imaging according to claim 7, characterized in that: A plurality of the single-channel radio frequency coils are combined together to form a multi-channel phased array radio frequency coil; The flexible part of each channel is made on an independent flexible printed circuit board, all the flexible printed circuit boards of multiple channels are staggered and stacked together, and all the transmission lines are gathered together and connected to the non-flexible part; Alternatively, all flexible parts of multiple channels are combined and fabricated on a single flexible printed circuit board.

9. The zero-weld-point flexible radio frequency coil structure for magnetic resonance imaging according to claim 8, characterized in that: All flexible printed circuit boards in the imaging area and part of the transmission lines outside the imaging area are packaged in a flexible cover, and all non-flexible parts outside the imaging area are packaged in a plastic box, and the flexible cover and the plastic box are pressed together.

Images