阅读说明：本技术 一种柔性磁共振成像线圈及其制造方法 (Flexible magnetic resonance imaging coil and manufacturing method thereof ) 是由 刘冉 李豪杰 林荣赞 于 2021-08-12 设计创作，主要内容包括：一种柔性磁共振成像线圈及其制造方法,属于磁共振成像技术领域。柔性磁共振成像线圈,由柔性材料、导电液体、导线和电路板组成；柔性材料构成容纳导电液体的管腔,导电液体充满管腔；导线将导电液体和电路板相连,构成一个完整环路,共同实现核磁共振接收线圈的功能。制造方法包括以下步骤：(1)配制柔性材料溶液；(2)将柔性材料溶液浇筑于模具之上并固化,得到具有流道的柔性材料层；(3)将导电液体灌注并使其完全充满流道内部；(4)利用导线将导电液体和电路板相连接,得到完整的柔性核磁共振线圈。本发明的线圈具备良好的柔性,且性能参数均一,工艺稳定性好；在使用时能够直接放置于待成像部位之上,从而大大提高图像信噪比。(A flexible magnetic resonance imaging coil and a manufacturing method thereof belong to the technical field of magnetic resonance imaging. The flexible magnetic resonance imaging coil consists of a flexible material, conductive liquid, a lead and a circuit board; the flexible material forms a tube cavity for containing the conductive liquid, and the tube cavity is filled with the conductive liquid; the conducting liquid and the circuit board are connected through the conducting wire to form a complete loop, and the function of the nuclear magnetic resonance receiving coil is realized together. The manufacturing method comprises the following steps: (1) preparing a flexible material solution; (2) pouring the flexible material solution on a mould and curing to obtain a flexible material layer with a flow channel; (3) filling the conductive liquid into the flow channel completely; (4) and connecting the conductive liquid with the circuit board by using a lead to obtain the complete flexible nuclear magnetic resonance coil. The coil has good flexibility, uniform performance parameters and good process stability; when in use, the device can be directly placed on a part to be imaged, so that the signal-to-noise ratio of the image is greatly improved.)

1. A flexible magnetic resonance imaging coil is characterized by comprising a flexible material, conductive liquid, a lead and a circuit board; the flexible material forms a tube cavity for containing the conductive liquid, and the tube cavity is filled with the conductive liquid; the conducting wire connects the conducting liquid and the circuit board to form a complete loop.

2. The flexible magnetic resonance imaging coil of claim 1, wherein the flexible material is an elastomer formed by curing a solution, and the flexible material is preferably silicone or polyurethane.

3. Flexible magnetic resonance imaging coil according to claim 1, characterized in that the electrically conductive liquid is a liquid metal, preferably gallium and its alloys.

4. Flexible magnetic resonance imaging coil according to claim 1, characterized in that the flexible material has several layers, preferably two layers.

5. The flexible magnetic resonance imaging coil of claim 1, wherein the flexible material has two layers, wherein the two layers of flexible material are formed by a layer of flexible material having a flow channel structure and a layer of flexible material film, or wherein the two layers of flexible material are formed by two layers of flexible material having a flow channel structure.

6. The flexible magnetic resonance imaging coil of claim 1, wherein the circuit board includes a tuning circuit, a detuning circuit, and a decoupling circuit.

7. The flexible mri coil of claim 1 wherein the electronic components used on the circuit board include resistors, capacitors, inductors, and diodes, and wherein the circuit board and the components thereon have a non-ferromagnetic characteristic.

8. A method of manufacturing a flexible magnetic resonance imaging coil according to any one of claims 1 to 7, comprising the steps of:

(1) preparing a flexible material solution;

(2) pouring the prepared flexible material solution on a mold and curing to obtain a flexible material layer with a flow channel;

(3) filling the conductive liquid into the flow channel completely;

(4) and connecting the conductive liquid with the circuit board by using a lead to obtain the complete flexible nuclear magnetic resonance coil.

9. The manufacturing method according to claim 8, wherein the flexible material layer in the step (2) has two layers, and the cured flexible material layer is subjected to surface treatment and then is integrated by physical or chemical treatment, preferably physical treatment.

10. The manufacturing method according to claim 8, wherein the conductive liquid in the step (3) is filled into the lumen by means of injection, negative pressure suction, preferably injection.

Technical Field

The invention belongs to the technical field of magnetic resonance imaging, and relates to a flexible magnetic resonance imaging coil and a manufacturing method thereof.

Background

Magnetic resonance imaging is a medical imaging technique based on radio frequency and microwave electronics. The method is widely applied to diagnosis of departments of hospitals, and has the advantages of high soft tissue imaging resolution, no ionizing radiation to human bodies and the like. The principle of the magnetic field is that magnetic moments formed by hydrogen proton spins in a human body are changed from random orientation to uniform orientation under the action of an external main magnetic field, and then are uniformly deflected under the action of radio frequency pulses. After the external radio frequency pulse is removed, the magnetic moment can be gradually restored to a uniform orientation, energy can be released outwards in the restoring process, the energy is captured by the receiving coil and then transmitted to a computer at the rear end, and the computer processes the energy and finally generates an image.

In the mri process, the receiver coil has a significant influence on the final imaging quality. To ensure that a higher signal-to-noise ratio can be obtained, it is ensured that the coil receives a better signal. However, if the coil size is increased, more signals are received and more noise is received. Therefore, coil arrays are often used to improve the signal-to-noise ratio, i.e., to reduce the area of a single coil unit, using multiple coils to receive signals simultaneously. However, since the mutual inductance phenomenon exists directly between adjacent coils and the number of channels that can be processed by a computer is limited, the number of coil units in the coil array is not smaller and larger, and the better the number of coil units is. The best imaging quality is obtained only with a coil array of suitable size and number of elements.

In addition, the energy dissipated outwards in the self-selection recovery process of the magnetic moment is weakened along with the increasing divergence distance. Therefore, to ensure that a sufficiently high signal can be received, the closer the coil should be to the surface of the human body, the better. Because most of the surfaces of the human body are not flat surfaces, the coil for imaging the human body does not have a universal structure, and different imaging coils, such as a head coil, a chest coil, a leg coil and the like, correspond to different parts. Taking the neck as an example, because the neck sizes of people with different body types are different, the coils existing on the market at present are all hard/semi-flexible coils, and the coils cannot be matched with different neck sizes well, so that the final imaging quality is often influenced because the body type of a subject is too large or too thin, and certain influence is brought to subsequent disease diagnosis.

Citation 1 discloses a method of manufacturing a nuclear magnetic resonance receiving coil by pouring liquid mercury into a plastic tube. The manufactured coil is directly placed on a part to be imaged to carry out imaging. However, the conductive material used in this method is mercury, which easily generates mercury vapor and is harmful to the human body, and thus this method is not suitable for practical use.

Reference 2 discloses a method of manufacturing a nuclear magnetic resonance receiving coil by coating a gallium-indium alloy on a synthetic foam rubber by means of stencil printing, but due to a problem of surface tension, liquid metal may be accumulated in the pores of the foam after repeated bending, resulting in short-circuiting of the coil, and thus it is not usable.

Citation 3 discloses a method of manufacturing a nuclear magnetic resonance receiving coil by pouring a gallium-indium alloy into a plastic pipe, and a method of manufacturing a nuclear magnetic resonance receiving coil by sewing a plastic pipe to a fabric. The problem of safety existing in citation 1 is solved, but because the plastic pipeline is amorphous, the coil structure design cannot be carried out according to actual requirements, and meanwhile, due to the amorphous shape, performance parameters of each coil are slightly different, and the process stability is poor.

Therefore, it is necessary to invent a flexible neck coil which is completely flexible and can be suitable for people with different body sizes.

Citation list:

cited document 1: american Journal of neurobiology, 1986,7: 246-.

Cited document 2: advanced Materials,2017,29(44):1703744.

Cited document 3: magnetic Resonance in Medicine,2021: mrm.28662.

Disclosure of Invention

In order to solve the problems, the invention provides a method for manufacturing a patterned flexible nuclear magnetic resonance receiving coil by using a flexible material and a conductive liquid and a flexible coil manufactured by using the method.

The technical scheme of the invention is as follows:

a flexible magnetic resonance imaging coil is composed of a flexible material, conductive liquid, a lead and a circuit board; the flexible material forms a tube cavity for containing the conductive liquid, and the tube cavity is filled with the conductive liquid; the conducting liquid and the circuit board are connected through the conducting wire to form a complete loop, and the function of the nuclear magnetic resonance receiving coil is realized together. The conductive liquid fills the lumen of the flexible material without air or other substances.

Further, the flexible material is an elastomer formed by curing a solution, and the flexible material is preferably silica gel or polyurethane.

Further, the conductive liquid is a liquid metal, preferably gallium and its alloys.

Further, the flexible material has several layers, preferably two layers.

Further, the flexible material has two layers, and the two layers of flexible materials are composed of a layer of flexible material with a flow channel structure and a layer of flexible material film, or the two layers of flexible materials are composed of two layers of flexible materials with a flow channel structure. When the two layers of flexible materials with the flow channel structures are combined, the mutual alignment of the flow channel structures of the two layers needs to be ensured.

Furthermore, the circuit board comprises a tuning circuit, a detuning circuit, a decoupling circuit and the like, which are used for ensuring that the magnetic resonance coil works at a proper resonance frequency and cannot be burnt out due to heating when a radio-frequency signal is transmitted.

Further, the electronic components used on the circuit board include resistors, capacitors, inductors, and diodes. The circuit board and the elements on the circuit board have the characteristic of no ferromagnetism.

A method of manufacturing a flexible magnetic resonance imaging coil, comprising the steps of:

1) preparing a flexible material solution;

2) pouring the prepared flexible material solution on a mold and curing to obtain a flexible material layer with a flow channel;

3) filling the conductive liquid into the flow channel completely;

4) and connecting the conductive liquid with the circuit board by using a lead to obtain the complete flexible nuclear magnetic resonance coil.

Further, the flexible material layer in the step 2) has two layers, the surface of the cured flexible material layer is treated, and then the cured flexible material layer is treated by a physical method or a chemical method to be combined into a whole, preferably a physical method.

Further, the conductive liquid in step 3) fills the lumen by means of injection and negative pressure suction, preferably injection.

The method provided by the invention can be used for manufacturing the nuclear magnetic resonance receiving coil with any two-dimensional shape, the manufactured coil has good flexibility, can be stretched by about 30% in any direction or can be recovered after being bent, is free from damage or plastic deformation, and has uniform performance parameters and good process stability. When the coil manufactured by the method is used, the coil can be directly placed on a part to be imaged, so that the signal-to-noise ratio of an image is greatly improved, the coil and the conventional commercial coil are subjected to an imaging contrast test, and an experimental result shows that the signal-to-noise ratio of the image obtained by the coil is more than 1.25 times that of the conventional coil.

Compared with the prior art, the invention has the following advantages and prominent technical effects:

the coil manufactured by the method is completely flexible, can be bent and folded randomly, and cannot generate plastic deformation;

the method can manufacture the coil and the packaging structure at one time, and the method is not a step-by-step process of manufacturing the coil first and then packaging in the existing manufacturing method, so that the manufacturing time and the process complexity of the coil are greatly reduced;

the weight of the coil manufactured by the method is greatly reduced, which is about one tenth of the weight of the coil manufactured by the existing manufacturing process, and the uncomfortable feeling of a user during use is basically eliminated;

the coil manufactured by the method has good uniformity and excellent process stability, and can be manufactured commercially in large batch.

The method can be used for manufacturing coil units with any two-dimensional shape, and the coil units can be conveniently combined to realize coil structures with different configurations.

Drawings

Fig. 1 is a flowchart of a method for manufacturing a flexible nuclear magnetic resonance receiving coil according to an embodiment of the present invention.

FIG. 2 is a side perspective view of a flexible nuclear magnetic resonance coil.

Figure 3 is a top perspective view of a flexible nuclear magnetic resonance coil.

In the figure: 1-a conductive liquid; 2-a flexible material; 3-a wire; 4-circuit board.

Detailed Description

The technical scheme of the invention is clearly and completely described below by combining the attached drawings of the specification. It is to be understood that the described embodiments are merely exemplary of some, and not necessarily all, embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without making creative efforts based on the embodiments of the present invention, belong to the protection scope of the present invention.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or quantity or location.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

The embodiment of the invention provides a method for manufacturing a flexible nuclear magnetic resonance receiving coil, which comprises the steps 1) to 5) shown in figure 1.

In step 1), a flexible material solution is prepared.

The present invention is limited to flexible materials that can be formulated as solutions and cured to elastomers under certain conditions. The material is preferably silica gel or polyurethane.

In the step 2), the prepared flexible material solution is poured on a mold and cured to obtain the flexible material layer with the flow channel.

In the present invention, the manner of making the mold is not limited, and may be additive manufacturing, machining, laser cutting, or a combination thereof. Preferably laser cutting. The invention limits the material of the mould, and requires that the material used by the mould is not combined with the flexible material into a whole in the whole process of curing the flexible material solution, and can bear the curing conditions of the flexible material, such as temperature, humidity, ultraviolet illumination and the like. The shape and size of the mold in the present invention are determined by the shape of the coil to be produced. The thickness of the mold determines the thickness of the conductor in the coil to be produced, and is preferably 0.05 mm.

In the present invention, the curing conditions of the flexible material solution are not limited, and may be solvent evaporation, thermal curing, ultraviolet curing, or a combination thereof. The specific curing conditions are determined by the flexible material solution selected. In the present invention, for the above-described preferable rubber or polyurethane material, the curing conditions are preferably thermal curing, and the heating temperature for thermal curing is preferably 80 ℃.

In the present invention, it is required that the flexible material and the mold are separated after curing in such a manner that the flexible material is not damaged, and it is preferable to peel the flexible material by hand.

In step 3), the flexible material with the flow channel and the other layer of flexible material are subjected to surface treatment and are combined into a whole with the complete flow channel.

The invention has no limitation on the surface treatment mode of the flexible material, and can be a physical method such as flowing water flushing, high-pressure gas cleaning and plasma treatment; chemical methods such as surface modification, surfactant treatment are also possible. The purpose of the surface treatment is to integrate the two layers of flexible material into one piece. In this embodiment, a combination of water flushing, high-pressure gas cleaning, and plasma treatment is preferable.

The present invention is not limited to the number of flexible material combinations, and may be a combination of two or more layers of flexible material. In this embodiment, a combination of two layers of flexible material is preferred.

The invention has no limit on the combination mode of the flexible materials, and physical methods such as pressing and hot pressing can be used among the flexible materials of each layer; chemical means such as adhesive bonding may also be used. In the embodiment, the lamination is preferred, and after the material subjected to the plasma treatment is laminated, the interface where different layers of materials contact generates molecular crosslinking, so that the materials of each layer can be firmly combined.

In step 4), the conductive liquid is poured and completely filled inside the flow channel. The conductive liquid material of the present invention is required not to generate a nuclear magnetic resonance signal. The conductive liquid material is preferably a liquid metal in this embodiment.

The invention has no limitation on the filling mode of the conductive liquid, and can use injection or negative pressure suction and other modes. Injection is preferred in this embodiment.

In the step 5), the conductive liquid is connected with the circuit board by using a lead to obtain the complete flexible nuclear magnetic resonance coil.

The present invention is not limited to the connection of the conductive wire and the conductive liquid, and preferably, the insertion contact is performed. The connection mode of the wires and the circuit board is not limited, and the connection mode can be welding or plugging by using an interface. In the present embodiment, welding is preferable. The circuit board has the functions of coil tuning, coil detuning and coil decoupling, and the functions are realized by a circuit formed by various electronic elements, and the various electronic elements have no ferromagnetism.

In this embodiment, only one method for manufacturing a flexible mri receive coil is described, and in actual implementation, a plurality of mri receive coil units can be manufactured to form an array by repeatedly using this method according to the size of a desired imaging region, so as to perform mri.

Examples

For a better understanding of the present invention, the present invention will be described in further detail with reference to the following examples. However, the scope of protection of the invention is not limited to the scope expressed in the examples.

The experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials are commercially available, unless otherwise specified.

1. And (3) sticking the mold on the heat release adhesive tape, and pressing for 2-3 times by using a film laminating machine to ensure that the mold is tightly stuck on the heat release adhesive tape. The applied tape and mold are then placed in a container.

2. The formulated silicone rubber liquid (typically PDMS) was poured into the above-described container to ensure complete coverage of the entire coil mold. The thickness of the runner layer can be adjusted by the amount of liquid poured in. The liquid is then subjected to a vacuum to ensure that there is no residual gas in the solution.

3. And (3) placing the container on a 80 ℃ hot table for precuring for 1h (ensuring the liquid level), and placing the container in an 80 ℃ oven for 4-8 h after precuring to completely cure the container.

4. And after the upper runner layer is completely cured, taking the upper runner layer out of the container, and placing the upper runner layer on a heating table for heating so as to release the upper runner layer from the heat release adhesive tape. The heat stage temperature depends on the phase transition temperature of the thermal release tape.

5. After the released runner layer is obtained, the mold is removed from the cured runner layer. There may be some liquid seeping into the gaps between the mold and the thermal release tape before curing, resulting in burrs at the edges of the flow channel, which can be removed by tweezers and then the flow channel can be trimmed.

6. And cleaning the trimmed runner layer by using a cleaning agent, and then drying by using nitrogen.

7. Cutting a PDMS film with a proper size, carrying out plasma treatment on the PDMS film and the cleaned and dried runner layer respectively, and then covering the runner layer on the PDMS film to bond the PDMS film and the runner layer into a whole. After covering, the bonding strength between the two can be enhanced by a film coating machine, but it should be noted that the upper and lower interfaces at the runner cannot be bonded. Then placing the mixture into an oven with the temperature of 80 ℃ to heat for 30 min-1 h to ensure the bonding strength.

8. Preparing a needle head and an injector with the needle head, and pricking the needle head into the pin of the runner at one side to ensure the air pressure balance in the runner when injecting the liquid metal. 0.9-1 ml of liquid metal is sucked into the injector, and the liquid metal is injected by pricking the pin at the other side, wherein the injection principle is based on completely filling the flow channel, and the liquid metal can be slightly excessive.

9. After the liquid metal is completely filled in the flow passage, the two needles are pulled out, and if the excessive liquid metal is injected, a little liquid metal overflows along the needle hole. After the overflowing liquid metal can be sucked by a syringe, the surface of PDMS is cleaned by wiping with an alcohol cotton sheet.

10. And then placing the coil after the injection into a freezing layer of a refrigerator to solidify the liquid metal. The liquid metal becomes more voluminous when it changes from the liquid state to the solid state, where a further part of the excess liquid metal can be excluded.

11. And taking out the frozen liquid metal coil, and cutting the liquid metal coil by using a cutting die and a die cutting machine to obtain a single coil unit.

12. And inserting the metal wire into the liquid metal along the pinhole, testing and conducting by using a universal meter, additionally configuring silicon rubber liquid to encapsulate the interface, and then placing the silicon rubber liquid into an oven for curing. The obtained flexible nuclear magnetic resonance receiving coil is shown in fig. 2 and 3 and consists of conductive liquid 1, flexible materials 2, a lead 3 and a circuit board 4; the flexible material 2 forms a tube cavity for containing the conductive liquid 1, and the tube cavity is filled with the conductive liquid 1; the conducting wire 3 connects the conducting liquid 1 and the circuit board 4 to form a complete loop.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention. The scope of the invention is defined by the claims and their equivalents.