Flexible coil for magnetic resonance imaging system and manufacturing process thereof

Abstract

The present invention relates to a flexible coil for magnetic resonance imaging systems, comprising a coil conductor having a specific shape, a tuning element connected to the coil conductor, and a flexible outer casing covering the coil conductor and the tuning element. The coil conductor is fabricated using a flexible printed circuit board. The flexible coil for magnetic resonance imaging systems of the present invention and its manufacturing process utilize flexible wires or printed circuit boards to form the coil conductor, enabling movement, bending, and twisting without damaging the wire. The coil conductor can be bent in multiple dimensions during use, allowing it to easily deform and conform to the body part being imaged during magnetic resonance scanning.

Description

Technical Field

[0001] The present invention relates to a radio frequency coil for a magnetic resonance imaging system, and in particular to a flexible coil for a magnetic resonance imaging system and a manufacturing process thereof. Background Art

[0002] Magnetic resonance imaging (MRI) systems are large-scale medical diagnostic equipment widely used in modern hospitals. MRI systems generate two-dimensional or three-dimensional images of samples based on the principles of MRI. Common MRI systems generally include: a main magnet that generates a static uniform magnetic field, B0, large enough to accommodate the imaging area of ​​the patient's body; a radio frequency (RF) system consisting of a RF transmitting coil for exciting the sample to resonate and a RF receiving coil for receiving the resonance signal emitted by the sample; a gradient system for generating gradient magnetic fields within the sample space to facilitate imaging encoding; and a computer imaging system for processing the signals collected by the RF receiving coil into visual images for the doctor to observe.

[0003] In magnetic resonance imaging (MRI), a receiving coil is used to collect radiofrequency signals emitted by the sample. The collected radiofrequency signals are amplified and used to reconstruct the sample image. The electrical structure of the receiving coil primarily consists of a coil body made of conductive material and circuit components such as inductors and capacitors connected to the coil body. In operation, the receiving coil covers the patient's examined area, and the magnetic resonance signals it outputs carry information about the body's tissues, producing images that doctors can use for diagnosis.

[0004] When the receiving coil is in operation, its spatial position relative to the patient's examined part needs to be relatively fixed. Traditionally, the receiving coil has a rigid structure, which is not convenient for examination and diagnosis of pediatrics or small joints. Summary of the Invention

[0005] Therefore, a flexible, agile and lightweight radio frequency receiving coil is needed.

[0006] The present invention discloses a flexible coil for a magnetic resonance imaging system, comprising a coil conductor and a tuning element connected to the coil conductor; and a flexible outer shell covering the coil conductor and the tuning element; the coil conductor is made of a flexible circuit board.

[0007] It also includes more than one enclosed shells, which are distributed in the plane where the coil conductor is located; the tuning elements are respectively wrapped in the enclosed shells.

[0008] The enclosed shell is evenly distributed in the plane where the coil conductor of the flexible coil is located, and protrudes from both side surfaces of the flexible coil.

[0009] The enclosed shell protrudes on the surface of the flexible coil to form hill-like protrusions that are continuously arranged in rows, and the low-lying areas between the hill-like protrusions are also continuously arranged in rows.

[0010] In one embodiment of the present invention, the thickness of the hill-like protrusions in the flexible coil is 1.5 to 5 times the thickness of the low-lying areas.

[0011] The present invention also discloses a manufacturing process for a flexible coil for a magnetic resonance imaging system, comprising the following steps:

[0012] A. A flexible printed circuit board is used to make the coil conductor, and a tuning element is connected therebetween;

[0013] B uses an enclosing shell to wrap the tuning elements respectively.

[0014] In one embodiment of the present invention, step B also includes:

[0015] The enclosed shells are evenly distributed on the plane where the coil conductors of the flexible coil are located.

[0016] In a manufacturing process of the present invention, the following steps are also included:

[0017] C. A flexible outer shell is formed according to the shape of the coil conductor and the position of the enclosing shell, and the flexible outer shell is used to fully cover the coil conductor and the tuning elements and the enclosing shell distributed therebetween.

[0018] In a manufacturing process of the present invention, the step C further comprises the following steps:

[0019] C. A first piece of the flexible jacket is formed according to the shape of the coil conductor and the position of the enclosing shell, and the surface is raised at the position of the enclosing shell to create an internal accommodation space; a second piece of the flexible jacket is formed according to the shape of the coil conductor and the position of the enclosing shell, and the surface is also raised at the position of the enclosing shell to create an internal accommodation space; the first piece of the flexible jacket, the coil conductor, the tuning element and the enclosing shell distributed therebetween, and the second piece of the flexible jacket are then aligned and stacked, and hot-pressed.

[0020] In a manufacturing process of the present invention, the surface layer of the flexible jacket is made of polyurethane cloth as a raw material, and the inner layer of the flexible jacket is made of EVA sheet material as a raw material.

[0021] The flexible coil for an MRI system and its manufacturing process of the present invention utilize flexible wires or flexible circuit boards to form the coil conductor, thereby enabling movement, bending, and twisting without damaging the wire. Furthermore, the tuning function circuit in the coil is broken down into smaller units, which are protected by a small-sized enclosing shell, which is then evenly distributed on the plane where the coil conductor is located. This allows the flexible coil to have uniform small protrusions on both surfaces, enabling it to bend in multiple dimensions during use. Furthermore, because it is wrapped and packaged with a flexible material, the flexible coil can be easily deformed and fitted to the body part being examined and imaged during MRI scanning. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the shape of a toroidal coil conductor.

[0023] Figure 2 It is a schematic diagram of the internal circuit structure of a flexible coil of the present invention.

[0024] Figure 3 It is a schematic diagram of the internal structure of a flexible coil of the present invention.

[0025] Figure 4 It is a schematic diagram of the three-dimensional shape of a flexible coil of the present invention.

[0026] Figure 5 The figure is a flow chart of a manufacturing process of a flexible coil for a magnetic resonance imaging system according to the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below with reference to the accompanying drawings. The present invention is not limited to the embodiments described below, but can be implemented in many different forms. The purpose of providing the following embodiments is to facilitate a more thorough and comprehensive understanding of the contents disclosed in the present invention.

[0028] It should be noted that, when this specification describes an original being "fixed" to another original, it means that the original is directly on the other original, or there are other intermediate originals in between; when this specification describes an element being "connected" to another element, it means that the original is directly connected to the other element, or there are intermediate elements in between.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. The terms used herein are only for describing specific embodiments and are not intended to limit the present invention.

[0030] The present invention discloses a flexible coil for magnetic resonance imaging systems and its manufacturing process. For radio frequency coil devices themselves, the most important factor affecting their performance is their electrical structure. The coil that adheres to the surface of the subject's body during magnetic resonance imaging is called a surface coil. Currently, the most commonly used coil conductor structure in surface coils is a ring coil. This coil conductor structure has the advantage of allowing for multiple overlapping structures, which is quite advantageous for imaging tissues and organs close to the human surface. Furthermore, it does not place high demands on the shape of the magnet. Although ring coils have poor uniformity, resulting in bright imaging of sample tissue close to the coil, various new technologies in the field of magnetic resonance imaging have expanded the application of surface coils, such as suppressing skin and fat tissue signals during imaging. To enable the surface coil to better conform to the human body during magnetic resonance scanning, we provide a flexible coil.

[0031] like Figure 1 The figure shows a ring-shaped coil conductor. The coil conductor is made of conductive material into a ring shape. Electrical components such as inductors and / or capacitors can be connected in series in the coil conductor. Figure 1 (not shown) The values ​​of the inductor and capacitor connected in series are adjusted according to the resonant frequency and electromagnetic coupling requirements, and the shape of the coil conductor is also adjusted. The RF coil of an MRI system also requires other functional circuits, such as tuning and detuning circuits; and electrical signal extraction devices, such as connecting signal cables through impedance matching circuits. Herein, the aforementioned electrical components and various functional circuits that need to be integrated with the coil conductor to implement the RF coil function are collectively referred to as tuning elements.

[0032] The flexible coil of the present invention may include a plurality of coil conductors, which may be Figure 1 The ring conductor shown may also be in other shapes or a combination of multiple shapes.

[0033] In the present invention, the coil conductor is made of a flexible wire or implemented on a flexible circuit board. Such a coil conductor can be bent to fit the scanning part of the human body during magnetic resonance imaging, thereby obtaining better magnetic resonance scanning images.

[0034] A flexible circuit board is formed by hot-pressing a metal foil conductor and an intermediate layer of adhesive. The intermediate layer can be a polyimide or polyester film substrate, and the metal foil conductor is typically made of copper foil, aluminum foil, or copper-beryllium alloy foil. Flexible circuit boards can be bent and twisted without damaging the conductors. They are lightweight and thin, and also have excellent dielectric properties, chemical resistance, and low moisture absorption, making them particularly suitable for relatively simple circuits. In one embodiment, the thickness of the flexible circuit board is 0.3 mm.

[0035] like Figure 2The figure shows a schematic diagram of the internal circuit structure of a flexible coil of the present invention. This is part of a printed circuit board of a surface coil, including the first unit coil CH1. The darker and wider lines constitute the coil conductor, and the thinner darker lines are the loop conductors that form the loop and transmit signals. There is a position for connecting tuning elements between the coil conductor and the loop conductor. For example, DC1, DC5, DC9, C1, L1, R1, R5 and VC1 in the figure are all positions where various tuning elements need to be connected. Figure 2 There are also some marking lines, prompts and installation holes required by the production process.

[0036] like Figure 3 The figure shows the internal structure of a flexible coil of the present invention, which is similar to Figure 2 The top view of the surface coil printed circuit board after the casing protecting the tuning element is installed is a part of the internal structure of a flexible coil, including the first unit coil CH1 and part of the fifth unit coil CH5. The rounded square is a small three-dimensional box ( Figure 3 (There are also other shaped small boxes in the box.) Each small box is an independent housing for the tuning element in the coil. This housing has a certain degree of hardness and protects the tuning element. It is rigid and insulated, protecting the tuning element and its connection to the coil conductor from damage caused by compression. The independent housing can also be of other shapes, as long as it can enclose and protect the tuning element. In this article, regardless of the shape, it is collectively referred to as an enclosing housing.

[0037] The size of this enclosed shell is relatively small relative to the flexible coil, is evenly distributed in the flexible coil, and evenly protrudes from the upper and lower surfaces. In order to fit the small-sized enclosed shell, the electrical components and various functional circuits of the flexible coil are separated into smaller sizes and connected with flexible wires. Please note that although each tuning element is placed in the enclosed shell, not every enclosed shell has a tuning element inside. Some enclosed shells are empty inside. This design ensures that the flexible coil can be bent and deformed equally in all directions, making it convenient to use. The present invention not only uses the enclosed shell to protect the tuning element, but also uses the enclosed shell to adjust the shape of the flexible coil. The hill-like protrusions evenly distributed on the surface of the flexible coil make the flexible coil feel smoother and softer to the touch, and can be freely bent and deformed in multiple dimensions of the plane to better fit the shape of the human body.

[0038] As an embodiment of the present invention, Figure 3The enclosed housing shown in the figure consists of two separable parts: a cubic upper shell and a mating lower shell. The upper shell has four protruding columns on its mating surface, while the lower shell has four internal holes. The tuning element is placed between the upper and lower shells. The four columns of the upper shell are then inserted through the printed circuit board and into the four internal holes of the lower shell, where they are then secured with glue.

[0039] See also Figure 3 In the same flexible coil, there can be a variety of enclosing shells of different specifications and shapes.

[0040] In one embodiment, a mounting through hole suitable for the enclosed housing is reserved on the flexible circuit board, and the four protruding columns of the upper shell pass through the mounting through hole through the flexible circuit board, are embedded in the four inner holes of the lower shell, and are then fixed with solidifying glue.

[0041] In one embodiment, the enclosed housing is independently molded and made of amorphous thermoplastic material, which has heat resistance, impact resistance, and flame retardancy, and has good mechanical properties within normal operating temperatures. It can be made of polycarbonate (abbreviated as PC) material by hot pressing.

[0042] The flexible coil of the present invention uses a flexible jacket to wrap the coil conductor and the enclosing shell distributed therebetween. One embodiment is to use a mold to separately form the upper and lower pieces of the flexible jacket, and the outer surfaces of the upper and lower pieces of the flexible jacket include raised pits for accommodating the enclosing shells of the coil conductors distributed on the flexible printed circuit board. The coil conductors and the enclosing shells distributed therebetween are then sandwiched together, hot-pressed, and then the edges are trimmed. In one embodiment, an independent mold is used, first placing the pre-formed lower piece of the flexible jacket, then placing the printed circuit board (coil conductor and enclosing shell), and finally placing the previously pressed upper part. The mold is heated, pressed, and sealed, and finally the edges are cut out with a die cutter or scissors.

[0043] In one embodiment, the outer surface of the flexible coat is made of polyurethane cloth (poly urethane), which is an organic polymer material. It has good physical properties, is resistant to twists and turns, has good softness, high tensile strength, and is breathable. The flexible coil using this flexible coat has a good soft and comfortable touch. EVA sheets (EVA is ethylene-vinyl acetate copolymer, such as EV30) are bonded to the inside of the PU cloth, and then a mold is used to hot-press the flexible coat. Because the polyurethane cloth is resistant to twists and turns and has high tensile strength, and the EVA sheet has fluidity after heating, the formed flexible coat is soft, smooth, and wrinkle-free, and is very durable and beautiful.

[0044] The coil conductor and tuning element of the present invention include small cables for interconnection. These small cables are connected between the enclosed housings and can be protected by heat shrink tubing. The output wires of the coil conductors are finally connected to an enclosed housing and connected to the output cable.

[0045] In this article, the coil conductor, loop conductor, and small cable in the internal circuit structure of the flexible coil are collectively referred to as coil conductors.

[0046] like Figure 4 Shown are schematic diagrams of the three-dimensional shape of a flexible coil according to the present invention, including a three-dimensional view of the coil curved in two different dimensions and a three-dimensional view without curvature. This invention breaks down the coil's tuning circuitry into smaller units, protecting them with a small, enclosing shell. This shell is then evenly distributed within the coil, creating uniform small protrusions on both surfaces of the flexible coil, facilitating multi-dimensional curvature and allowing it to easily conform to the body part being imaged during MRI scanning.

[0047] During operation, this flexible coil conforms to the body part and bends and deforms according to the shape of the body part. This shape can be maintained in this operating state using external straps. In one embodiment, the straps attached to the patient's bed are attached to the surface of the flexible coil using commercially available Velcro, and the position of the straps on the bed can be adjusted by sliding.

[0048] The flexible outer shell of the flexible coil of this invention is molded using a combination of PU cloth and EVA. Its hardness is precisely tailored to the needs of MRI imaging, neither too soft to deform nor too hard to bend. Traditional surface coils, which use sponge as the outer packaging material, are soft to the touch and provide a pleasant user experience, but they are fragile and lack the strength to use flexible circuit boards or flexible conductors for the internal coil conductors.

[0049] The flexible coil of the present invention has hillock-like protrusions on the upper and lower planes. The positions of the hillock-like protrusions on the upper and lower planes are one-to-one corresponding, and the hillock-like protrusions on the upper surface also protrude on the lower surface. In addition, the hillock-like protrusions are arranged in rows on the plane, and there is a low-lying groove between the two rows of hillock-like protrusions. The thickness of the flexible coil at the position of the hillock-like protrusions is between 15 mm and 25 mm, and the thickness of the flexible coil at the position of the low-lying groove is between 5 mm and 10 mm. The thickness of the hillock-like protrusion is 1.5 to 5 times the thickness of the low-lying groove. The hillock-like protrusion is rigid and does not deform, and is used to protect the built-in tuning elements. The shape of the hillock-like protrusion is the same as the shape of the enclosed shell.

[0050] like Figure 4The flexible coil of the present invention shown can be appropriately bent in two dimensions of the plane to adapt to the surface of the human body being scanned. When the flexible coil covers or surrounds the surface of the human body, it can be bent or even surrounded to fit the surfaces of different parts of the human body. The hill-like protrusions on the surface of the flexible coil can be other shapes, such as a rounded cube, or a part of a sphere. In this case, the flexible coil can be appropriately bent in more dimensions. When the flexible coil is in a bent state, the low-lying grooves on its upper surface are unfolded, and the low-lying grooves on its lower surface are squeezed. At this time, the shape of the flexible coil becomes an arc, and any dimension of the surface of the flexible coil can be bent. Applying external force can maintain this bent state of the flexible coil. When the external force is removed, the flexible coil can restore its flat shape.

[0051] Traditional surface coils use a rigid hard case to protect the tuning element, which is then padded with soft sponge to create a flat surface on both sides. The entire surface coil is approximately 20 mm thick, making it difficult to bend significantly even without the rigid case.

[0052] Figure 5 FIG. 1 is a flow chart of a manufacturing process of a flexible coil for a magnetic resonance imaging system according to the present invention. In one embodiment of the present invention, the manufacturing process includes the following steps:

[0053] 101 A coil conductor is made of a flexible circuit board or a flexible wire, and a tuning element is connected therebetween;

[0054] 102 wrapping the tuning element with an enclosing shell, and evenly distributing the enclosing shell on the plane where the coil conductor is located;

[0055] 103 forming a first piece of the flexible outer shell, and making a surface of the flexible outer shell have convexities so as to form an accommodating space of the enclosed shell;

[0056] 104 is a second piece of the flexible outer cover formed in the same manner, and also has a raised outer surface to form a receiving space for the enclosed shell;

[0057] 105 Align the coil conductor, the tuning elements distributed therebetween, and the enclosing shell and stack them between the two flexible jackets, and then perform heat-pressing bonding.

[0058] In another embodiment of the present invention, after step 102, the following steps are included:

[0059] 203 forming a flexible outer shell, in which a space for accommodating the enclosed shell is reserved;

[0060] 204 uses a flexible outer jacket to cover the coil conductor and the enclosing shell distributed therebetween.

[0061] In one manufacturing process, in step 103, step 104, and step 203, PU cloth and EVA are combined and formed by hot pressing in a mold.

[0062] The technical features of the above-mentioned embodiments can also be combined in other ways. For the sake of brevity, all possible combinations of technical features are not fully described here. It is hereby declared that as long as there is no contradiction in the combination of these technical features, they all fall within the scope of this specification.

[0063] The above embodiments specifically and in detail describe several implementation methods of the present invention, which is not intended to limit the scope of the invention patent. For those skilled in the art, several variations and improvements can be made without departing from the concept of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention fall within the scope of protection of the present invention, and the scope of protection of the patent of the present invention shall be based on its claims.

Claims

1. A flexible coil for a magnetic resonance imaging system, comprising a coil conductor and a tuning element connected to the coil conductor; and a flexible outer shell covering the coil conductor and the tuning element; characterized in that: The coil conductor is made of a flexible circuit board; It also includes one or more enclosing shells, which are distributed in the plane where the coil conductor is located; the tuning elements are respectively wrapped in the enclosing shells; The enclosed shell is evenly distributed in the plane where the coil conductor of the flexible coil is located, and protrudes from both side surfaces of the flexible coil.

2. The flexible coil for a magnetic resonance imaging system according to claim 1, wherein The enclosed shell protrudes on the surface of the flexible coil to form hill-like protrusions that are continuously arranged in rows, and the low-lying areas between the hill-like protrusions are also continuously arranged in rows.

3. The flexible coil for a magnetic resonance imaging system according to claim 2, wherein: The thickness of the hill-shaped protrusions in the flexible coil is 1.5 to 5 times the thickness of the low-lying areas.

4. A manufacturing process for a flexible coil for a magnetic resonance imaging system, characterized in that: The steps include: A. A flexible printed circuit board is used to make the coil conductor, and a tuning element is connected therebetween; B. wrapping the tuning elements respectively with an enclosing shell; and C. A flexible outer shell is formed according to the shape of the coil conductor and the position of the enclosing shell, and the flexible outer shell is used to fully cover the coil conductor and the tuning elements and the enclosing shell distributed therebetween.

5. The manufacturing process of the flexible coil for magnetic resonance imaging system according to claim 4, characterized in that: Step B also includes: The enclosed shells are evenly distributed on the plane where the coil conductors of the flexible coil are located.

6. The manufacturing process of the flexible coil for magnetic resonance imaging system according to claim 5, characterized in that: The step C further comprises the following steps: C. forming a first piece of the flexible outer shell according to the shape of the coil conductor and the position of the enclosing shell, and making the surface convex at the position of the enclosing shell to form an internal accommodation space; Then, forming a second piece of the flexible outer shell according to the shape of the coil conductor and the position of the enclosing shell, and also making the surface convex at the position of the enclosing shell to form an internal accommodation space; Then, the first sheet of the flexible jacket, the coil conductor, the tuning element and the enclosing shell distributed therebetween, and the second sheet of the flexible jacket are aligned and stacked, and then heat-pressed and bonded.

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