Distributed adjustable capacitor for magnetic resonance imaging radio frequency coil
By designing distributed adjustable capacitors on magnetic resonance radio frequency coils and forming effective capacitance units by lithography corrosion, the problems of short circuit and inaccurate cropping in traditional coil capacitance adjustment are solved, and the precise adjustment of capacitance value and coil resonance frequency are achieved. Flexible adjustments improve the efficiency and image quality of magnetic resonance imaging.
Patent Information
- Application Number
- CN202411307564.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-19
- Publication Date
- 2024-12-06
AI Technical Summary
Traditional magnetic resonance radio frequency coils are prone to short-circuit points when adjusting the capacitance value, and the flexible insulating dielectric layer has a small thickness and is not accurate in cutting, which makes it difficult to accurately adjust the capacitance value and affects the image quality.
Design a distributed adjustable capacitor to form effective capacitance units in the overlapping area of the upper conductor and the lower conductor on the insulating dielectric layer, and use photolithography corrosion to form capacitor connecting conductors to ensure that each effective capacitance unit is the same area and facilitate cutting Adjust the capacitance value to avoid the risk of short circuit.
The precise adjustment of the capacitance value of the magnetic resonance radio frequency coil is achieved, which reduces debugging time, avoids short circuit faults, and improves the stability and image quality of the coil.
Smart Images
Figure CN119092299A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of magnetic resonance imaging systems, in particular to a distributed adjustable capacitor for a radio frequency coil of magnetic resonance imaging. Background Art
[0002] Magnetic resonance imaging is an advanced non-destructive imaging technology for the human body, which is widely used in medical imaging diagnosis of diseases in various parts of the human body. The MRI radio frequency coil is an important part of the MRI system, and its performance directly determines the quality of the MRI image.
[0003] The traditional magnetic resonance radio frequency coil is composed of several lumped capacitors (usually ceramic capacitors) and several conductors that are alternately arranged and connected in sequence to form a loop. These capacitors and conductors are usually attached to an insulating dielectric layer (such as an FR4 board or a polyimide film). The inductance and capacitance of these conductors themselves form an RF resonant loop. When the resonant frequency is equal to the frequency of the magnetic resonance signal, it can most effectively detect the weak magnetic resonance radio frequency signal emitted by the human body. The adjustment of the coil resonant frequency is achieved by changing the number, position and capacitance value of the capacitors.
[0004] Distributed capacitance technology uses several sections of unconnected conductors to form distributed capacitance. These conductors form inductance on the one hand, and also participate in the formation of distributed capacitance at the same time. By adjusting the length, width, relative position, etc. of these conductors, their resonant frequency can be adjusted. When the resonant frequency is equal to the frequency of the magnetic resonance signal, the magnetic resonance radio frequency signal can be effectively detected. The structure of the distributed capacitor is an upper conductor, a lower conductor and an insulating medium layer, and the upper conductor and the lower conductor are located on the upper surface and the lower surface of the insulating medium. The overlap area between the upper conductor and the lower conductor in the vertical direction determines the size of the distributed capacitance. By adjusting the overlap area between the upper conductor and the lower conductor in the vertical direction of the capacitance, the capacitance can be adjusted, thereby changing the resonant frequency of the coil. In general, the upper conductor and the lower conductor of the distributed capacitor used in the magnetic resonance radio frequency coil overlap in the vertical direction of the capacitance in the overlap area, and the middle insulating medium layer uses a flexible material, such as a polyimide film. In the actual production process, the resonant frequency of the coil can be changed by simply cutting the overlapping area of the conductor with scissors, which is very convenient for production debugging. However, because the flexible insulating dielectric layer is relatively thin, it is very easy to cause the upper and lower layers of conductors to be connected together when using scissors to cut the conductor, thus forming a short circuit point, causing the entire magnetic resonance radio frequency coil to malfunction. In addition, because the thickness of the flexible insulating dielectric layer is very small, it is difficult to find the short circuit point when a short circuit occurs. Moreover, the entire conductor of a general distributed capacitor is a whole and cannot be precisely cut to size. Only a small amount can be cut off each time, and continuous attempts are required to reduce the capacitance value of the distributed capacitor to the appropriate size. Otherwise, once too much is cut off, 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, the problem to be solved is how to use distributed capacitors on the MRI radio frequency coil while avoiding the upper and lower layers of the capacitor conductors from being connected together to form a short circuit point when adjusting the capacitance value. Summary of the invention
[0006] In order to overcome the shortcomings of the prior art, the present invention provides a distributed adjustable capacitor for a magnetic resonance imaging radio frequency coil, wherein each effective capacitor has the same unit area and the same capacitance value, so that the required capacitance value can be obtained by one-time cutting.
[0007] To achieve the above purpose, a distributed adjustable capacitor for a radio frequency coil of a magnetic resonance imaging is designed, comprising an upper conductor, a lower conductor, and an insulating dielectric layer, characterized in that: the upper conductor is located on the upper surface of the insulating dielectric layer, and the lower conductor is located on the lower surface of the insulating dielectric layer; the overlapping portion between the upper conductor and the lower conductor in the vertical direction is an effective capacitor, and the area of the effective capacitor is the effective capacitance value.
[0008] The upper conductors include 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 is connected to the upper conductor of the effective capacitor, and a plurality of upper layers of capacitor connecting conductors are evenly arranged on the upper conductor of the effective capacitor.
[0009] The upper layer of the capacitor connection conductor is formed by photolithography and etching.
[0010] The lower conductors include the lower conductors of the main capacitor, the lower conductors of the effective capacitor, and the lower layer of capacitor connecting conductors. One side of the lower conductor of the main capacitor is connected to the lower conductor of the effective capacitor, and a plurality of lower layers of capacitor connecting conductors are evenly arranged on the lower conductor of the effective capacitor.
[0011] The capacitor connection conductor lower layer is formed by photolithography and etching.
[0012] The upper conductor of the effective capacitor and the lower conductor of the effective capacitor overlap each other to form an effective capacitor, and a gap is provided between the upper layer of the capacitor connecting conductor and the lower layer of the capacitor connecting conductor.
[0013] The effective capacitor is in the shape of a square, a circle, or other regular shapes.
[0014] A method for adjusting the capacitance value of the distributed adjustable capacitor used in the radio frequency coil for magnetic resonance imaging is characterized in that the specific method is as follows: S1, stack the upper conductor, the insulating dielectric layer, and the lower conductor from top to bottom in sequence, the upper conductor of the main capacitor of the upper conductor overlaps with the lower conductor of the main capacitor of the lower conductor to form a main capacitor; the upper conductor of the effective capacitor of the upper conductor overlaps with the lower conductor of the capacitor connection conductor to form an effective capacitor; the capacitance value of the entire distributed capacitor = main capacitor + effective capacitor × the number of effective capacitors; S2, according to the actual situation, cut off the number of effective capacitors.
[0015] Compared with the prior art, the present invention provides a distributed adjustable capacitor for a radio frequency coil for magnetic resonance imaging. The unit area of the effective capacitance of the distributed adjustable capacitor is the same and has the same capacitance value. Therefore, when cutting the distributed adjustable capacitor to reduce the capacitance value, it is only necessary to count the corresponding number of effective capacitances and cut them off, without having to subtract a small amount each time and make multiple attempts, which greatly saves the debugging time of the radio frequency coil for magnetic resonance imaging. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 It is a schematic diagram of the overall framework of the present invention.
[0017] Figure 2 It is a schematic diagram of the upper conductor structure of the present invention.
[0018] Figure 3 It is a schematic diagram of the lower conductor structure of the present invention.
[0019] Figure 4 This is a schematic diagram of the distributed adjustable capacitor structure of the present invention.
[0020] Figure 5 Schematic diagram of the cutting process of the distributed adjustable capacitor of the present invention.
[0021] See also Figures 1 to 4 , 1 is the upper conductor, 1-1 is the upper conductor of the main capacitor, 1-2 is the upper conductor of the effective capacitor, 1-3 is the upper layer of the capacitor connecting conductor, 2 is the insulating dielectric layer, 3 is the lower conductor, 3-1 is the lower conductor of the main capacitor, 3-2 is the lower conductor of the effective capacitor, 3-3 is the lower layer of the capacitor connecting conductor, and 4 is the effective capacitor. DETAILED DESCRIPTION
[0022] The present invention will be further described below with reference to the accompanying drawings.
[0023] like Figure 1 As shown, 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; the overlapping portion 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.
[0024] like Figure 2 As shown, the upper conductor 1 includes an upper conductor of the main capacitor, an upper conductor of the effective capacitor, and an upper layer of a capacitor connecting conductor. One side of the upper conductor 1-1 of the main capacitor is connected to an upper conductor 1-2 of the effective capacitor, and a plurality of upper layers of capacitor connecting conductors 1-3 are evenly distributed on the upper conductor 1-2 of the effective capacitor.
[0025] The capacitor connection conductor upper layer 1-3 is formed by photolithography etching.
[0026] like Figure 3 As shown, the lower conductor 3 includes a lower conductor of the main capacitor, a lower conductor of the effective capacitor, and a lower layer of capacitor connecting conductors. One side of the lower conductor 3-1 of the main capacitor is connected to the lower conductor 3-2 of the effective capacitor, and a plurality of lower layers of capacitor connecting conductors 3-3 are evenly distributed on the lower conductor 3-2 of the effective capacitor.
[0027] The capacitor connection conductor lower layer 3-3 is formed by photolithography etching.
[0028] like Figure 4 As shown, the upper conductor 1-2 of the effective capacitor and the lower conductor 3-2 of the effective capacitor overlap to form an effective capacitor 4, and a gap is provided between the upper capacitor connection conductor 1-3 and the lower capacitor connection conductor 3-3.
[0029] The effective capacitor 4 is in the shape of a square, a circle, or other regular shapes.
[0030] A method for adjusting the capacitance value of a distributed adjustable capacitor for a radio frequency coil for magnetic resonance imaging, the specific method is as follows: S1, stack the upper conductor 1, the insulating dielectric layer 2, and the lower conductor 3 from top to bottom in sequence, the upper conductor 1-1 of the main capacitor of the upper conductor 1 and the lower conductor 3-1 of the main capacitor of the lower conductor 3 overlap up and down to form a main capacitor; the upper conductor 1-2 of the effective capacitor of the upper conductor 1 and the lower capacitor connection conductor 3-3 of the lower conductor 3 overlap up and down to form an effective capacitor 4; the capacitance value of the entire distributed capacitor = main capacitor + effective capacitor × the number of effective capacitors; S2, according to the actual situation, cut off the number of effective capacitors.
[0031] The present invention adds a distributed adjustable capacitor next to a normal distributed capacitor (hereinafter referred to as a distributed main capacitor). The upper conductor 1 and the lower 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 these areas overlap in the vertical direction of the capacitor. The small areas on each layer of conductors are connected to the surrounding small areas through thin conductors (hereinafter referred to as capacitor connection conductors), and the upper and lower layers of conductors used to connect the small areas have a certain distance in the vertical direction of the capacitor and do not overlap each other.
[0032] The magnetic resonance imaging radio frequency coil of the present invention is very convenient to debug. It only needs to cut off some of the effective capacitor 4 units from the entire distributed capacitor to reduce the capacitance value of the capacitor, thereby changing the resonant frequency of the coil. In addition, since the capacitor connecting conductors between the effective capacitor 4 units of the upper and lower conductors are at a certain distance in the horizontal direction of the capacitor, there is no risk of short circuiting the upper and lower conductors when they are cut.
[0033] like Figure 4 As shown, according to Figure 2 and Figure 3 The upper conductor 1 and the lower conductor 3 are made separately, and the insulating dielectric layer 2 is inserted between the two to form the entire distributed adjustable capacitor. The actual operation process is to photoetch the upper and lower sides of the flexible PCBA board with the upper and lower conductive layers. Figure 3 and Figure 2 A distributed main capacitor is formed between the upper conductor 1-1 of the main capacitor and the lower conductor 3-1 of the main capacitor, and a distributed adjustable capacitor is formed between the grid-shaped upper conductor 1 and the lower conductor 3. Figure 4 The distributed adjustable capacitor in the embodiment consists of 30 effective capacitors 4 in 5 rows and 6 columns.
[0034] like Figure 5 As shown, the distributed capacitance adjustment method of the present invention is as follows Figure 5 By cutting the dotted line in the left figure, the three effective capacitors 4 on the left side of the first row can be cut off, and the following is obtained: Figure 5 The distributed capacitor shown in the figure on the right. The capacitance value of the entire distributed capacitor changes from the capacitance value of the distributed main capacitor plus the capacitance value of 30 effective capacitors 4 to the capacitance value of the distributed main capacitor plus the capacitance value of 27 effective capacitors 4. Since the upper layer 1-3 of the capacitor connection conductor and the lower layer 3-3 of the capacitor connection conductor between the effective capacitor 4 units do not overlap in the vertical direction of the capacitor plane, when the effective capacitor 4 is cut, no short circuit will be caused between the upper layer 1-3 of the capacitor connection conductor and the lower layer 3-3 of the capacitor connection conductor.
[0035] In summary, the debugging of the MRI radio frequency coil of the present invention is very convenient. It is only necessary to cut off some effective capacitor units from the entire distributed capacitor to reduce the capacitance of the capacitor, thereby changing the resonant frequency of the coil. Moreover, the capacitance value of each effective capacitor unit is equal, because the resonant frequency can be adjusted very accurately. At the same time, since there is a certain distance in the vertical direction between the upper layer of the capacitor connecting conductor and the lower layer of the capacitor connecting conductor between the upper and lower conductors, there is no risk of short circuiting the upper and lower conductors when they are cut.
Claims
1. A distributed adjustable capacitor for a radio frequency coil for magnetic resonance imaging, comprising an upper conductor, a lower conductor, and an insulating dielectric layer, characterized in that: 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); the overlapping portion between the upper conductor (1) and the lower conductor (3) in the vertical direction is an effective capacitor (4), and the area of the effective capacitor (4) is the effective capacitance value.
2. The distributed adjustable capacitor for a radio frequency coil for magnetic resonance imaging according to claim 1, characterized in that: The upper conductor (1) comprises 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 (1-1) of the main capacitor is connected to an upper conductor (1-2) of the effective capacitor, and a plurality of upper layers of capacitor connecting conductors (1-3) are evenly arranged on the upper conductor (1-2) of the effective capacitor.
3. The distributed adjustable capacitor for a radio frequency coil for magnetic resonance imaging according to claim 2, characterized in that: The capacitor connection conductor upper layer (1-3) is formed by photolithography and etching.
4. The distributed adjustable capacitor for a radio frequency coil for magnetic resonance imaging according to claim 1, characterized in that: The lower conductor (3) comprises 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 (3-1) of the main capacitor is connected to a lower conductor (3-2) of the effective capacitor, and a plurality of lower layers of capacitor connecting conductors (3-3) are evenly arranged on the lower conductor (3-2) of the effective capacitor.
5. The distributed adjustable capacitor for a radio frequency coil for magnetic resonance imaging according to claim 4, characterized in that: The capacitor connection conductor lower layer (3-3) is formed by photolithography and etching.
6. The distributed adjustable capacitor for a radio frequency coil for magnetic resonance imaging according to claim 2, characterized in that: The upper conductor (1-2) of the effective capacitor and the lower conductor (3-2) of the effective capacitor overlap to form an effective capacitor (4), and a gap is provided between the upper capacitor connection conductor (1-3) and the lower capacitor connection conductor (3-3).
7. A distributed adjustable capacitor for a radio frequency coil for magnetic resonance imaging according to claim 1 or 6, characterized in that: The effective capacitor (4) is in the shape of a square, a circle, or any other regular shape.
8. A method for adjusting the capacitance value of a distributed adjustable capacitor for a radio frequency coil for magnetic resonance imaging according to claim 1, characterized in that: The specific method is as follows: S1, stacking the upper conductor (1), the insulating dielectric layer (2), and the lower conductor (3) from top to bottom in sequence, the upper conductor (1-1) of the main capacitor of the upper conductor (1) and the lower conductor (3-1) of the main capacitor of the lower conductor (3) overlap up and down to form a main capacitor; the upper conductor (1-2) of the effective capacitor of the upper conductor (1) and the lower layer (3-3) of the capacitor connection conductor of the lower conductor (3) overlap up and down to form an effective capacitor (4); the capacitance value of the entire distributed capacitor = main capacitance + effective capacitance × the number of effective capacitors; S2, according to the actual situation, cut off the number of effective capacitors.