Distributed tunable capacitor for magnetic resonance imaging radio-frequency coil

Abstract

A distributed tunable capacitor for a magnetic resonance imaging radio-frequency coil, the distributed tunable capacitor comprising an upper conductor (1), a lower conductor (3), and an insulating dielectric layer (2), wherein the upper conductor (1) is located on the upper surface of the insulating dielectric layer (2), and the lower conductor (3) is located on the lower surface of the insulating dielectric layer (2); and the overlapping portion between the upper conductor (1) and the lower conductor (3) in the vertical direction is an effective capacitor, and the area of the effective capacitor represents an effective capacitance value. Effective capacitors in the distributed tunable capacitor have the same unit area and the same capacitance value, such that when the distributed tunable capacitor is trimmed to reduce the capacitance value, it is only necessary to count a corresponding number of effective capacitors and cut same off, instead of trimming a tiny amount repeatedly through trial and error, thereby greatly reducing the debugging time of a magnetic resonance imaging radio-frequency coil.

Description

Distributed tunable capacitance for magnetic resonance imaging radio frequency coils TECHNICAL FIELD

[0001] The present application relates to the technical field of magnetic resonance imaging system, in particular to a distributed tunable capacitance for magnetic resonance imaging radio frequency coils. BACKGROUND

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

[0003] The traditional magnetic resonance radio frequency coil is formed by a plurality of lumped capacitors (generally ceramic capacitors) and a plurality of conductors which are alternately arranged and connected to form a loop. These capacitors and conductors are usually attached to an insulating medium layer (such as FR4 board or polyimide film). The inductance and capacitance of these conductors form a radio frequency resonant loop, which can most effectively detect the weak magnetic resonance radio frequency signals emitted by the human body when the resonant frequency is equal to the frequency of the magnetic resonance signal. The adjustment of the coil resonant frequency is achieved by changing the number, position and capacitance value of the capacitors.

[0004] The distributed capacitance technology uses several segments of conductors which are not connected to each other to form distributed capacitance. The conductors form inductance on one hand and participate in forming distributed capacitance on the other hand. The resonant frequency can be adjusted by adjusting the length, width, relative position of the conductors, etc. When the resonant frequency is equal to the magnetic resonance signal frequency, the magnetic resonance radio frequency signal can be effectively detected. The structure of the distributed capacitance is an upper conductor, a lower conductor and an insulating medium layer. The upper conductor and the lower conductor are located on the upper surface and the lower surface of the insulating medium. The overlapping area between the upper conductor and the lower conductor in the vertical direction determines the size of the distributed capacitance. The size of the capacitance can be adjusted by adjusting the overlapping area between the upper conductor and the lower conductor in the vertical direction of the capacitance, so as to change the resonant frequency of the coil. Generally, the upper conductor and the lower conductor of the distributed capacitance used in the magnetic resonance radio frequency coil are coincident in the overlapping area in the vertical direction of the capacitance, and the insulating medium layer in the middle is made of flexible material, such as polyimide film. In the actual production process, only the overlapping area of the conductors needs to be cut by scissors to change the resonant frequency of the coil, which is very convenient for production and debugging. However, because the flexible insulating medium layer is relatively thin, the scissors during the cutting process of the conductors are very easy to cause the upper and lower conductors to be connected together, thereby forming a short circuit point, resulting in failure of the entire magnetic resonance radio frequency coil. Moreover, because the flexible insulating medium layer is very thin, it is difficult to find the short circuit point when a short circuit fault occurs. Moreover, the entire conductor of the general distributed capacitance is an integral whole and cannot be precisely cut to size. Only a small amount can be cut each time, and it is necessary to constantly try to reduce the capacitance value of the distributed capacitance to the appropriate size. Otherwise, if too much is cut, the capacitance value is less than the required value and there is no way to increase the capacitance value, and the entire coil may be scrapped.

[0005] Therefore, how to use the distributed capacitance on the magnetic resonance imaging radio frequency coil while avoiding the connection of the upper and lower conductors of the capacitance to form a short circuit point when adjusting the capacitance value is a problem to be solved. SUMMARY

[0006] The present application is to overcome the shortcomings of the prior art and provide a distributed adjustable capacitance for a magnetic resonance imaging radio frequency coil. The unit area of each effective capacitance is the same and has the same capacitance value, so that the required capacitance value can be obtained by cutting once.

[0007] To achieve the above-mentioned purpose, a distributed adjustable capacitance for a magnetic resonance imaging radio frequency coil is designed, which comprises an upper conductor, a lower conductor and an insulating medium layer. The upper conductor is located on the upper surface of the insulating medium layer, and the lower conductor is located on the lower surface of the insulating medium layer. The overlapping part between the upper conductor and the lower conductor in the vertical direction is an effective capacitance. The area of the effective capacitance is the effective capacitance value.

[0008] The upper layer conductor includes a main capacitor upper layer conductor, an effective capacitor upper layer conductor, and capacitor connection upper layers, one side of the main capacitor upper layer conductor is connected to the effective capacitor upper layer conductor, and a plurality of capacitor connection upper layers are uniformly arranged on the effective capacitor upper layer conductor.

[0009] The capacitor connection upper layers are formed by photoetching and etching.

[0010] The lower layer conductor includes a main capacitor lower layer conductor, an effective capacitor lower layer conductor, and capacitor connection lower layers, one side of the main capacitor lower layer conductor is connected to the effective capacitor lower layer conductor, and a plurality of capacitor connection lower layers are uniformly arranged on the effective capacitor lower layer conductor.

[0011] The capacitor connection lower layers are formed by photoetching and etching.

[0012] The effective capacitor upper layer conductor and the effective capacitor lower layer conductor are overlapped to form an effective capacitor, and a gap is arranged between the capacitor connection upper layers and the capacitor connection lower layers.

[0013] The effective capacitor is one of a square, a circle, or other regular shapes.

[0014] A capacitor value adjusting method for the distributed adjustable capacitor for the magnetic resonance imaging radio frequency coil, and the specific method is as follows:

[0015] S1, the upper layer conductor, the insulating medium layer, and the lower layer conductor are sequentially stacked from top to bottom, the main capacitor upper layer conductor of the upper layer conductor and the main capacitor lower layer conductor of the lower layer conductor are overlapped to form a main capacitor, the effective capacitor upper layer conductor of the upper layer conductor and the capacitor connection lower layer of the lower layer conductor are overlapped to form an effective capacitor, and the capacitor value of the entire distributed capacitor = main capacitor + effective capacitor x number of effective capacitors.

[0016] S2, according to the actual situation, the number of effective capacitors is cut.

[0017] Compared with the prior art, the present application provides a distributed adjustable capacitor for the magnetic resonance imaging radio frequency coil, the unit area of the effective capacitor of the distributed adjustable capacitor is the same, and the capacitor value is the same, so when the distributed adjustable capacitor is cut to reduce the capacitor value, only the corresponding number of effective capacitors is counted and cut, without trying many times to reduce a little bit each time, which greatly saves the debugging time of the magnetic resonance radio frequency imaging radio frequency coil. BRIEF DESCRIPTION OF DRAWINGS

[0018] Fig. 1 is a schematic diagram of the overall framework of the present application.

[0019] Fig. 2 is a schematic diagram of the upper layer conductor structure in the present application.

[0020] Fig. 3 is a schematic diagram of the lower conductor structure in the present application.

[0021] Fig. 4 is a schematic diagram of the distributed adjustable capacitor structure in the present application.

[0022] Fig. 5 is a schematic diagram of the trimming process of the distributed adjustable capacitor in the present application.

[0023] Referring to Figs. 1 to 4, 1 is an upper conductor, 1-1 is an upper conductor of a main capacitor, 1-2 is an upper conductor of an effective capacitor, 1-3 is an upper layer of a capacitor connecting conductor, 2 is an insulating medium layer, 3 is a lower conductor, 3-1 is a lower conductor of a main capacitor, 3-2 is a lower conductor of an effective capacitor, 3-3 is a lower layer of a capacitor connecting conductor, and 4 is an effective capacitor. DETAILED DESCRIPTION

[0024] The present application will be further described below with reference to the accompanying drawings.

[0025] As shown in Fig. 1, the upper conductor 1 is located on the upper surface of the insulating medium layer 2, and the lower conductor 3 is located on the lower surface of the insulating medium layer 2; the overlapping part between the upper conductor 1 and the lower conductor 3 in the vertical direction is the effective capacitor 4, and the area of the effective capacitor 4 is the effective capacitance value.

[0026] As shown in Fig. 2, the upper conductor 1 includes an upper conductor of a main capacitor, an upper conductor of an effective capacitor, and an upper layer of a capacitor connecting conductor; one side of the upper conductor of the main capacitor 1-1 is connected to the upper conductor of the effective capacitor 1-2, and a plurality of upper layers of the capacitor connecting conductor 1-3 are uniformly arranged on the upper conductor of the effective capacitor 1-2.

[0027] The upper layer of the capacitor connecting conductor 1-3 is formed by photoetching and etching.

[0028] As shown in Fig. 3, the lower conductor 3 includes a lower conductor of a main capacitor, a lower conductor of an effective capacitor, and a lower layer of a capacitor connecting conductor; one side of the lower conductor of the main capacitor 3-1 is connected to the lower conductor of the effective capacitor 3-2, and a plurality of lower layers of the capacitor connecting conductor 3-3 are uniformly arranged on the lower conductor of the effective capacitor 3-2.

[0029] The lower layer of the capacitor connecting conductor 3-3 is formed by photoetching and etching.

[0030] As shown in Fig. 4, the upper conductor of the effective capacitor 1-2 and the lower conductor of the effective capacitor 3-2 overlap each other to form the effective capacitor 4, and a gap is provided between the upper layer of the capacitor connecting conductor 1-3 and the lower layer of the capacitor connecting conductor 3-3.

[0031] The effective capacitor 4 is one of a square, a circle, or other regular shapes.

[0032] A method for adjusting the capacitance value of a distributed adjustable capacitor for a magnetic resonance imaging radio frequency coil, the method comprising the following steps:

[0033] S1, the upper layer conductor 1, the insulating medium layer 2 and the lower layer conductor 3 are stacked from top to bottom, the upper layer conductor 1-1 of the main capacitor of the upper layer conductor 1 and the lower layer conductor 3-1 of the main capacitor of the lower layer conductor 3 are overlapped to form a main capacitor; the upper layer conductor 1-2 of the effective capacitor of the upper layer conductor 1 and the capacitor connection conductor lower layer 3-3 of the lower layer conductor 3 are overlapped to form an effective capacitor 4; the capacitance value of the whole distributed capacitor = main capacitor + effective capacitor × the number of effective capacitors;

[0034] S2, according to the actual situation, the number of effective capacitors is cut off.

[0035] The application increases a distributed adjustable capacitor beside the normal distributed capacitor (hereinafter referred to as distributed main capacitor). The upper layer conductor 1 and the lower layer conductor 3 of the distributed adjustable capacitor are composed of many small areas (hereinafter referred to as effective capacitors 4) with the same area, and the areas are overlapped in the vertical direction of the capacitor. The small areas on each layer of conductor are connected with the small areas around through thin conductors (hereinafter referred to as capacitor connection conductors), and the conductors for connecting the small areas of the upper and lower layers have a certain distance in the vertical direction of the capacitor and do not overlap each other.

[0036] The magnetic resonance imaging radio frequency coil using the application is very convenient to debug, only a few effective capacitor 4 units are cut off from the whole distributed capacitor, the capacitance value of the capacitor can be reduced, so that the resonant frequency of the coil is changed. Moreover, the capacitor connection conductors between the effective capacitor 4 units of the upper and lower layers have a certain distance in the horizontal direction of the capacitor, so there is no risk of short circuit between the upper and lower layers when the upper and lower layers are cut off.

[0037] As shown in FIG. 4, the upper layer conductor 1 and the lower layer conductor 3 are respectively made according to FIG. 2 and FIG. 3, and the insulating medium layer 2 is inserted between the two, to form the whole distributed adjustable capacitor. The actual operation process is to etch the patterns of FIG. 3 and FIG. 2 on the upper and lower sides of the flexible PCBA board of the upper and lower conductive layers. The upper layer conductor 1-1 of the main capacitor and the lower layer conductor 3-1 of the main capacitor form a distributed main capacitor, and the grid-shaped upper layer conductor 1 and the lower layer conductor 3 form a distributed adjustable capacitor. The distributed adjustable capacitor in FIG. 4 is composed of 5 rows and 6 columns of effective capacitors 4, a total of 30 effective capacitors 4.

[0038] As shown in Fig. 5, the method for adjusting the distributed capacitance of the present application, along the dotted line in the left part of Fig. 5, the first row of three effective capacitors 4 can be cut off, and the distributed capacitance as shown in the right part of Fig. 5 is obtained. The capacitance value of the whole distributed capacitance changes from the capacitance value of the distributed main body capacitance plus the capacitance value of 30 effective capacitors 4 to the capacitance value of the distributed main body capacitance plus the capacitance value of 27 effective capacitors 4. Since the upper layer of capacitive connecting conductors 1-3 and the lower layer of capacitive connecting conductors 3-3 do not overlap in the vertical direction of the capacitive plane, the cutting of the effective capacitors 4 will not cause a short circuit between the upper layer of capacitive connecting conductors 1-3 and the lower layer of capacitive connecting conductors 3-3.

[0039] In summary, the adjustment of the magnetic resonance imaging radio frequency coil of the present application is very convenient. By cutting some effective capacitors from the whole distributed capacitance, the capacitance value can be reduced, and the resonant frequency of the coil can be changed. Moreover, the capacitance value of each effective capacitor is equal, and the resonant frequency can be adjusted very accurately. At the same time, since the upper layer of capacitive connecting conductors and the lower layer of capacitive connecting conductors have a certain distance in the vertical direction, there is no risk of short circuit between the upper and lower layers of conductors when cutting.

Claims

1. A distributed tunable capacitance for a magnetic resonance imaging radio frequency coil comprising an upper layer of conductors, a lower layer of conductors, an insulating dielectric layer, characterized in that: The upper layer conductor (1) is located on the upper surface of the insulating medium layer (2), and the lower layer conductor (3) is located on the lower surface of the insulating medium layer (2); the overlapping part between the upper layer conductor (1) and the lower layer conductor (3) in the vertical direction is an effective capacitor (4), and the area of the effective capacitor (4) is an effective capacitor value.

2. A distributed tunable capacitance for a magnetic resonance imaging radio frequency coil according to claim 1, characterized in that: The upper layer conductor (1) comprises an upper layer conductor of a main capacitor, an upper layer conductor of an effective capacitor, and an upper layer capacitor connection conductor, and the upper layer conductor of the main capacitor (1-1) is connected to the upper layer conductor of the effective capacitor (1-2) on one side, and a plurality of upper layer capacitor connection conductors (1-3) are uniformly arranged on the upper layer conductor of the effective capacitor (1-2).

3. A distributed tunable capacitance for a magnetic resonance imaging radio frequency coil according to claim 2, wherein: The upper layer capacitor connection conductor (1-3) is formed by photoetching.

4. A distributed tunable capacitance for a magnetic resonance imaging radio frequency coil according to claim 1, wherein: The lower layer conductor (3) comprises a lower layer conductor of a main capacitor, a lower layer conductor of an effective capacitor, and a lower layer capacitor connection conductor, and the lower layer conductor of the main capacitor (3-1) is connected to the lower layer conductor of the effective capacitor (3-2) on one side, and a plurality of lower layer capacitor connection conductors (3-3) are uniformly arranged on the lower layer conductor of the effective capacitor (3-2).

5. A distributed tunable capacitance for a magnetic resonance imaging radio frequency coil according to claim 4, wherein: The lower layer capacitor connection conductor (3-3) is formed by photoetching.

6. A distributed tunable capacitance for a magnetic resonance imaging radio frequency coil according to claim 2, wherein: The upper layer conductor of the effective capacitor (1-2) and the lower layer conductor of the effective capacitor (3-2) are overlapped to form the effective capacitor (4), and a gap is arranged between the upper layer capacitor connection conductor (1-3) and the lower layer capacitor connection conductor (3-3).

7. A distributed tunable capacitance for a magnetic resonance imaging radio frequency coil according to claim 1 or 6, characterized in that: The effective capacitor (4) is one of a square, a circle, or other regular shapes.

8. A method of adjusting the capacitance value of the distributed tunable capacitance for a magnetic resonance imaging radio frequency coil of claim 1, characterized by, The specific method is as follows: S1, the upper layer conductor (1), the insulating medium layer (2), and the lower layer conductor (3) are sequentially stacked from top to bottom, the upper layer conductor of the main capacitor (1-1) of the upper layer conductor (1) and the lower layer conductor of the main capacitor (3-1) of the lower layer conductor (3) are overlapped to form a main capacitor; the upper layer conductor of the effective capacitor (1-2) of the upper layer conductor (1) and the lower layer conductor of the capacitor connection conductor (3-3) of the lower layer conductor (3) are overlapped to form an effective capacitor (4); the capacitor value of the entire distributed capacitor = main capacitor + effective capacitor x number of effective capacitors; S2, according to the actual situation, the number of effective capacitors is cut off.

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