A gradient shim device

Abstract

The application relates to a gradient shimming device, which comprises a Z0 coil, a Z shielding coil, an X shielding coil, a Y shielding coil, a Z2 coil, a ZX coil, a ZY coil, an X2-Y2 coil and an XY coil. The Z0 coil, the Z main coil, the Z shielding coil and the Z2 coil are wound by wires to form a solenoid structure, other coils are engraved by copper plates and then bent into arcs by a coiling method, the Z main coil and the Z shielding coil skeleton are used as a skeleton, a passive shimming slot is embedded in the middle, and after all the coil layers are arranged layer by layer, the whole set of gradient shimming device is formed. The coil is corrected and designed by adopting a coil coiling error correction method and a return line control method, structural form deviations caused by stretching or compression in the process of transforming the coil from a plane to an arc can be eliminated, and the problem of difficult return line arrangement of sub-coils of the coil caused by space limitation and dense winding of the coil when the sub-coils are connected into a stringed loop can be solved.

Description

Technical Field

[0001] This invention belongs to the field of electrical engineering theory and new technology, and specifically relates to a gradient shimming device for magnetic resonance imaging detection. Background Technology

[0002] Gradient shimming coils are crucial components in magnetic resonance imaging (MRI) systems. The target magnetic field configuration is typically obtained through spherical harmonic decomposition. Gradient coils, specifically first-order coils with a linear gradient magnetic field configuration, are used to encode the imaging space, thereby identifying the source of the magnetic resonance signal. Coils of other orders, such as zero-order and second-order coils, are generally used as shimming coils and are called active shimming coils. First-order coils can also possess first-order shimming capabilities. Since first-order coils primarily function as gradient encoders, their design requires generating a high-intensity gradient magnetic field. During encoding, the gradient magnetic field needs to be repeatedly switched. To prevent eddy current secondary effects from the alternating magnetic field on surrounding conductors, gradient coils typically require shielding. Furthermore, to suppress Joule heating, a high-performance water-cooling system is needed for coil cooling. To further improve shimming performance, passive shimming rods are usually embedded within the gradient shimming coils, forming a gradient shimming device.

[0003] Chinese invention patent ZL202110565739.7 discloses a parallel gradient coil structure, comprising three sets of gradient coils, employing active shielding to block stray magnetic fields. It does not include shimming coils or passive shimming slots, nor does it disclose methods for correcting coiling errors or controlling lap rotation. Figure 3 and Figure 4 As can be seen from the design case, the gradient coil is relatively large, and its rolling error and lap problem are not prominent. Chinese patent ZL202310178125.2 discloses a gradient coil for magnetic resonance imaging, which includes an actively shielded triaxial gradient coil. The coil is spherical or ellipsoidal in shape, but does not mention the case where the shimming coil is cylindrical. There are also significant differences between the two in terms of design method and spatial structure. Summary of the Invention

[0004] Gradient shimming coils often introduce shape errors during the coiling process. In some coil designs, the coil shape must be adjusted to allow for loop gaps during the construction of the current loop. These introduced shape errors or adjustments are particularly significant in the development of small-aperture coils. In order to eliminate the above-mentioned shape deviations from the design level and construct a high-performance gradient shimming coil engineering solution, this invention proposes a gradient shimming device, including a coil coiling error correction method and a loop control method, and further provides a highly reliable gradient shimming coil engineering solution.

[0005] The technical solution adopted in this invention is as follows:

[0006] A gradient shimming device is cylindrical in shape. The coils are arranged from the inside out as follows: Z main coil, X main coil, Y main coil, Z0 coil, Z2 coil, ZX coil, ZY coil, X2-Y2 coil, XY coil, Z shielding coil, X shielding coil, and Y shielding coil. A passive shimming slot is located between the XY coil and the Z shielding coil. The slotted Z main coil frame and the slotted Z shielding coil frame serve as a support frame. The X main coil is attached to the X main coil with an adhesive ring. On the epoxy board, the Y main coil is attached to the Y main coil adhesive epoxy board, the Z0 coil is wound on the Z0 coil slotted epoxy board, the Z2 coil is wound on the Z2 coil slotted epoxy board, the ZX coil is attached to the ZX coil adhesive epoxy board, the ZY coil is attached to the ZY coil adhesive epoxy board, the X2-Y2 coil is attached to the X2-Y2 coil adhesive epoxy board, the XY coil is attached to the XY coil adhesive epoxy board, the X shielded coil is attached to the X shielded coil adhesive epoxy board, and the Y shielded coil is attached to the Y shielded coil adhesive epoxy board.

[0007] Furthermore, the coils that need to be rolled outwards include the X main coil, Y main coil, ZX coil, ZY coil, X2-Y2 coil, and XY coil; the coils that need to be rolled inwards in the gradient shimming coil include the X shielding coil and the Y shielding coil.

[0008] The correction of coil rolling error is divided into two cases: external rolling and internal rolling. The coil to be rolled is pasted on an epoxy board with adhesive. When rolling externally, the coil is on top and the epoxy board is on the bottom, thus forming an arc-shaped structure of an outer coil and an inner epoxy board. When rolling internally, the epoxy board is on top and the coil is on the bottom, thus forming an arc-shaped structure of an outer epoxy board and an inner coil. The coil rolling error correction method is as follows:

[0009] Assuming the coil thickness is t and the radial position of the coil center plane is r, then the position of the cylindrical surface of the outer coil wire is corrected to rt / 2, and the position of the cylindrical surface of the inner coil wire is corrected to r+t / 2.

[0010] Furthermore, the 360-degree fully enclosed structure of the coil's conductor cylindrical surface is separated into two non-fully enclosed structures, with a reserved loop gap width of w and the position of the conductor cylindrical surface being r1. Then, the angle of the interlayer space of the non-fully enclosed structure is w / r1 / π×180, and the angle occupied by each part of the two non-fully enclosed structures is 180-w / r1 / π×180. Then, a mathematical model is performed based on the conductor cylindrical surface of the non-fully enclosed structure, and the coil conductor distribution is obtained by reverse solving.

[0011] Furthermore, the coil pairing method allows the interlayer space of adjacent coil layers to be utilized by each other. The paired coils are X main coil and Y main coil, ZX coil and ZY coil, X2-Y2 coil and XY coil, X shielding coil and Y shielding coil; wherein the return line of the first paired coil is embedded in the interlayer space of the second paired coil, and the return line of the second paired coil is embedded in the interlayer space of the first paired coil.

[0012] Furthermore, the Z0 coil is a zero-order frequency modulation coil, the Z shielding coil, the X shielding coil, and the Y shielding coil are first-order active shielding gradient coils, and the Z2 coil, ZX coil, ZY coil, X2-Y2 coil, and XY coil are second-order shimming coils. The Z0 coil, Z main coil, Z shielding coil, and Z2 coil are wound with wire to form a solenoid structure, while the other coils are engraved with copper plates and bent into arc shapes by rolling. The Z main coil and Z shielding coil skeletons serve as the overall support skeleton, with a passive shimming slot embedded in the middle. All the coils are arranged in layers to form a complete gradient shimming device.

[0013] Furthermore, the Z main coil and Z shield coil are wound with hollow copper tubes, while the Z0 coil and Z2 coil are wound with solid copper wire.

[0014] The present invention has the following beneficial technical effects:

[0015] The gradient shimming device involved in this invention includes a gradient coil, a shimming coil, and a passive shimming slot. Especially with small apertures, the proposed coiling error correction method and loop control method are highly effective. This gradient shimming device eliminates the morphological deviation caused by coil coiling and rationally arranges the coil current loop. Based on this, a highly reliable gradient coil engineering scheme is provided, effectively integrating multiple components such as the gradient coil, shimming coil, water-cooling path, and passive shimming to form a high-performance gradient device. Attached Figure Description

[0016] Figure 1 This is the overall structure of the gradient homogenizing device of the present invention;

[0017] Figure 2 This is a schematic diagram of a coil being rolled into a circle;

[0018] Figure 3 A schematic diagram showing the reserved return line gap and coil pairing;

[0019] Figure 4 It is a gradient uniform field coil.

[0020] Explanation of reference numerals in the attached diagram: 1 is the Z main coil frame, 2 is the Z shielded coil frame, 3a is the Z main coil, 3b is the Z shielded coil, 4a is the X main coil with epoxy board, 4b is the X shielded coil with epoxy board, 5a is the X main coil, 5b is the X shielded coil, 6a is the Y main coil with epoxy board, 6b is the Y shielded coil with epoxy board, 7a is the Y main coil, 7b is the Y shielded coil, 8 is the Z0 coil with slotted epoxy board, 9 is the Z0 coil, 10 is the Z2 coil with slotted epoxy board, 11 is the Z2 coil, 12 is the ZX coil with epoxy board, 13 is the ZX coil, 14 is the ZY coil with epoxy board, 15 is the ZY coil, 16 is the X2-Y2 coil with epoxy board, 17 is the X2-Y2 coil, 18 is the XY coil with epoxy board, 19 is the XY coil, 20 is the passive shimming slot. Detailed Implementation

[0021] The technical solutions of the present invention will now be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention.

[0022] like Figure 1 As shown, the gradient shimming device of the present invention is cylindrical in shape, and its coils are arranged in the following order from the inside to the outside: Z main coil 3a, X main coil 5a, Y main coil 7a, Z0 coil 9, Z2 coil 11, ZX coil 13, ZY coil 15, X2-Y2 coil 17, XY coil 19, Z shielding coil 3b, X shielding coil 5b, and Y shielding coil 7b. The passive shimming slot 20 is located between the XY coil 19 and the Z shielding coil 3b. The slotted Z main coil frame 1 of the Z main coil 3a and the slotted Z shielding coil frame 2 of the Z shielding coil 3b serve as the overall support frame. The X main coil 5a is attached to the X main coil adhesive epoxy board 4a; the Y main coil 7a is attached to the Y main coil adhesive epoxy board 6a; the Z0 coil 9 is wound on the Z0 coil slotted epoxy board 8; the Z2 coil 11 is wound on the Z2 coil slotted epoxy board 10; the ZX coil 13 is attached to the ZX coil adhesive epoxy board 12; the ZY coil 15 is attached to the ZY coil adhesive epoxy board 14; the X2-Y2 coil 17 is attached to the X2-Y2 coil adhesive epoxy board 16; the XY coil 19 is attached to the XY coil adhesive epoxy board 18; the X shielding coil 5b is attached to the X shielding coil adhesive epoxy board 4b; and the Y shielding coil 7b is attached to the Y shielding coil adhesive epoxy board 6b.

[0023] like Figure 2As shown, the coiling error correction method is divided into two cases: external coiling and internal coiling. The coil to be coiled is pasted on an epoxy board with adhesive. When coiling externally, the coil is on top and the epoxy board is on the bottom, thus forming an arc-shaped structure of an outer coil and an inner epoxy board. When coiling internally, the epoxy board is on top and the coil is on the bottom, thus forming an arc-shaped structure of an outer epoxy board and an inner coil. The coiling error correction method is used to eliminate the structural shape deviation caused by the stretching of the external coiling or the compression of the internal coiling during the transformation of the coil from a plane to an arc.

[0024] The coils that need to be rolled outwards in the gradient shimming coil include X main coil 5a, Y main coil 7a, ZX coil 13, ZY coil 15, X2-Y2 coil 17, and XY coil 19. The coils that need to be rolled inwards in the gradient shimming coil include X shielding coil 5b and Y shielding coil 7b.

[0025] The method for correcting coil roundness error is as follows:

[0026] Assuming the coil thickness is t and the radial position of the coil center plane is r, then the position of the conductor cylindrical surface of the outer coil is corrected to rt / 2 during design, and the position of the conductor cylindrical surface of the inner coil is corrected to r+t / 2 during design.

[0027] like Figure 3 As shown, the loop control method involves reserving a specified width of interlayer space through a non-fully enclosed coil structure during coil design. The coil obtained through reverse optimization design has no wire distribution in the interlayer space, thus forming a dedicated wiring channel for the coil. This method is used to solve the problem of loop arrangement difficulties caused by space constraints and tight coil winding when the sub-coils of the coil are connected into a series circuit.

[0028] The loopback control method is as follows:

[0029] The 360-degree fully enclosed structure of the coil conductor cylindrical surface is separated into two non-fully enclosed structures. Assuming the reserved loop gap width is w, and the position of the modified conductor cylindrical surface is r1, then the angle of the interlayer space of the non-fully enclosed structure is w / r1 / π×180, and the angle occupied by each part of the two non-fully enclosed structures is 180-w / r1 / π×180. Then, a mathematical model is performed based on the conductor cylindrical surface of the non-fully enclosed structure, and the coil conductor distribution is obtained by reverse solving.

[0030] The coil pairing method allows for the utilization of the interlayer space between adjacent coil layers. The paired coils are X main coil 5a and Y main coil 7a, ZX coil 13 and ZY coil 15, X2-Y2 coil 17 and XY coil 19, X shielding coil 5b and Y shielding coil 7b. The return line of the first paired coil is embedded in the interlayer space of the second coil, and the return line of the second coil is embedded in the interlayer space of the first coil.

[0031] The Z main coil 3a and Z shielding coil 3b are wound with hollow copper tubes, and the Z0 coil 9 and Z2 coil 11 are wound with solid copper wires to form a single-layer solenoid structure. When the solenoid is wound from one end to the other, it returns through the gap between the passive shimming slots.

[0032] like Figure 4 As shown, the coil structure in the gradient shimming device includes a zero-order frequency-modulated Z0 coil 9, a first-order actively shielded Z gradient coil (with an inner Z main coil and an outer Z shield coil), an X gradient coil (with an inner X main coil and an outer X shield coil), a Y gradient coil (with an inner Y main coil and an outer Y shield coil), and a second-order shimming coil, Z2 coil, ZX coil, ZY coil, X2-Y2 coil, and XY coil.

[0033] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A gradient shimming device, characterized in that: The device is cylindrical in shape. The coils are arranged from the inside out as follows: Z main coil, X main coil, Y main coil, Z0 coil, Z2 coil, ZX coil, ZY coil, X2-Y2 coil, XY coil, Z shielded coil. X-shielded coil, Y-shielded coil, passive shimming slot located between XY coil and Z-shielded coil; the slotted Z-main coil skeleton and the slotted Z-shielded coil skeleton of Z-main coil serve as supporting skeletons; X-main coil is pasted on X-main coil adhesive epoxy board, Y-main coil is pasted on Y-main coil adhesive epoxy board, Z0 coil is wound on Z0 coil slotted epoxy board, Z2 coil is wound on Z2 coil slotted epoxy board, ZX coil is pasted on ZX coil adhesive epoxy board, ZY coil is pasted on ZY coil adhesive epoxy board, X2-Y2 coil is pasted on X2-Y2 coil adhesive epoxy board, XY coil is pasted on XY coil adhesive epoxy board, X-shielded coil is pasted on X-shielded coil adhesive epoxy board, Y-shielded coil is pasted on Y-shielded coil adhesive epoxy board; The coils that need to be rolled outwards include the X main coil, Y main coil, ZX coil, ZY coil, X2-Y2 coil, and XY coil. The coils that need to be rolled inwards in the gradient shimming coil include the X shielding coil and the Y shielding coil. The correction of coil rolling error is divided into two cases: external rolling and internal rolling. The coil to be rolled is pasted on an epoxy board with adhesive. When rolling externally, the coil is on top and the epoxy board is on the bottom, thus forming an arc-shaped structure of an outer coil and an inner epoxy board. When rolling internally, the epoxy board is on top and the coil is on the bottom, thus forming an arc-shaped structure of an outer epoxy board and an inner coil. The coil rolling error correction method is as follows: Assuming the coil thickness is t and the radial position of the coil's center plane is r, then the position of the cylindrical surface of the outer coil conductor is corrected to be... The position of the cylindrical surface of the inwardly rolled circular coil wire is corrected to ; The 360-degree fully enclosed structure of the coil's conductor cylindrical surface is separated into two non-fully enclosed structures, with a reserved loop gap width of [missing information]. The position of the cylindrical surface of the conductor is Then the angle of the interlayer space in the non-fully enclosed structure is The angle occupied by each part in the two-part non-fully enclosed structure is Then, based on the non-fully enclosed cylindrical surface of the conductor, a mathematical model is created, and the coil conductor distribution is obtained by reverse solving. The coil pairing method allows the interlayer space between adjacent coil layers to be utilized by each other. The paired coils are X main coil and Y main coil, ZX coil and ZY coil, X2-Y2 coil and XY coil, X shielded coil and Y shielded coil. The return line of the first paired coil is embedded in the interlayer space of the second paired coil, and the return line of the second paired coil is embedded in the interlayer space of the first paired coil.

2. The gradient shimming device according to claim 1, characterized in that: The Z0 coil is a zero-order frequency modulation coil. The Z shielded coil, X shielded coil, and Y shielded coil are first-order active shielded gradient coils. The Z2 coil, ZX coil, ZY coil, X2-Y2 coil, and XY coil are second-order shimming coils. The Z0 coil, Z main coil, Z shielded coil, and Z2 coil are wound with wire to form a solenoid structure. The other coils are engraved with copper plates and bent into arc shapes by rolling. The Z main coil and Z shielded coil skeletons serve as the overall support skeleton, with a passive shimming slot embedded in the middle. All the coils are arranged in layers to form a complete gradient shimming device.

3. The gradient shimming device according to claim 2, characterized in that: The Z main coil and Z shield coil are wound with hollow copper tubes, while the Z0 coil and Z2 coil are wound with solid copper wire.

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