JP6022750B2 - Radiation detector - Google Patents

Description

  Each embodiment of the present invention relates to a radiation detection apparatus.

  An X-ray image detector using an active matrix has attracted much attention as a diagnostic detector for detecting radiation, particularly X-rays. By applying X-rays to a planar detector, an X-ray image or a real-time X-ray image is output as a digital signal. Since this X-ray image detector is a solid state detector, it is highly expected in terms of image quality performance and stability. For this reason, many universities and manufacturers have been engaged in research and development.

  The first practical application has been developed for chest and general radiography that collects still images with a relatively large dose, and has recently been commercialized. Commercialization is expected in the near future for applications in the cardiovascular and gastrointestinal fields where it is necessary to clear higher technical hurdles and realize real-time video of 30 frames per second under fluoroscopic dose. . For this moving image application, improvement of S / N and real-time processing technology of minute signals are important development items.

  Radiation detection devices that detect radiation, particularly X-rays, are used in a wide range of fields such as industrial nondestructive inspection, medical diagnosis, and structural research. Among radiation detection devices, a radiation detection device having a radiation detection panel in which a phosphor layer is directly formed on a planar photodetector having a photoelectric conversion element is known as a high-sensitivity and high-definition device. . In the phosphor layer of this radiation detection apparatus, the radiation is converted into light that can be detected by the photoelectric conversion element section. In the photoelectric conversion element portion of this radiation detection apparatus, pixels each having a plurality of photosensors and TFTs (Thin Film Transistors) are two-dimensionally arranged on a glass substrate. The switching element of each pixel is connected to a gate line representing a row and a signal line representing a column. The gate lines and the signal lines are arranged in a grid pattern and are connected to each pixel arranged in the grid pattern.

  By laminating a phosphor that converts X-rays into visible light on a planar photodetector, X-rays incident from the outside are converted into visible light inside the phosphor, and the generated visible light is detected by planar light. Incident light. Visible light incident on the photodiode in the planar photodetector is converted into electric charge and accumulated in the photodiode or in the capacitive element connected in parallel. The X-ray image information converted into electric charge is transmitted to the outside of the substrate through a switching element (TFT) connected to the photodiode. When the potential of the gate line changes, the TFT connected to the gate line where the potential has changed becomes conductive, and the charge accumulated in the photodiode or the capacitor connected to the conductive TFT becomes TFT. Is output to the outside. The electric charge output to the outside is output to the outside of the glass substrate through a signal line connected to the TFT.

  The charge signal output to the outside of the glass substrate is input to the integrating amplifier connected to each signal line. The charge information input to the integrating amplifier is amplified, converted into a potential signal, and output. The potential signal output from the integrating amplifier is converted into a digital value by an analog / digital converter, and finally edited as an image signal and output to the outside of the X-ray image detector. The radiation detection panel is supported on one surface of a plate-like support member, and a circuit board for driving the radiation detection panel is supported on the other surface of the support member. The radiation detection panel and the circuit board are electrically connected by a flexible circuit board. It is connected.

  The support member for supporting the radiation detection panel and the circuit board connected to the radiation detection panel are protected from the outside, and the housing of the radiation detection device is configured by combining metal and resin parts so as to be integrated. Yes. If noise is applied to the charge signal output from the radiation detection panel substrate to the outside, a defect or an abnormal value may occur in the image signal.

JP 2000-28736 A

  When the radiation detection apparatus is driven, noise that affects the charge signal output from the circuit board to the outside of the radiation detection panel is generated. A flexible circuit board that transmits a minute charge signal detected by the radiation detection panel to the circuit board may be affected by the noise and acquire an image signal having a large noise component.

  In many cases, the circuit board is composed of a plurality of boards in consideration of expandability and productivity. A plurality of circuit boards function as a single drive circuit by dividing necessary functions for each circuit board and combining the circuit boards. If each of the divided circuit boards has a different ground voltage, the potential signal output from the integrating amplifier may acquire an image signal shifted for each divided circuit board. .

  Therefore, the problem to be solved by the present invention is to provide a radiation detection apparatus that reduces the influence of noise on an electric signal flowing through a flexible substrate.

In order to solve the above problems, a radiation detection apparatus according to an embodiment includes a radiation detection panel that includes a first terminal group and detects radiation incident on an incident surface and outputs an electrical signal, and the incidence of the radiation detection panel A support plate that supports a surface opposite to the surface; a circuit board that includes a second terminal group and is positioned on the opposite side of the radiation detection panel of the support plate to drive the radiation detection panel; and the first terminal A flexible board that extends electrically outside the outer edge of the support plate and electrically connects between the group and the second terminal group; a plate-like fixing portion that extends along the circuit board; and the circuit board Conductive noise shielding having at least a part of an element located on the circuit board standing in the direction toward the support plate and extending across between the flexible board and the circuit board. and body, Serial is mounted on a flexible board, comprising a, an integrating amplifier for amplifying and integrating the electric signal which the radiation detection panel is output.
The flexible substrate and the integrating amplifier are provided on the side opposite to the element side with the shielding portion interposed therebetween.

It is the II arrow directional cross-sectional view of FIG. 2 of the radiation detection apparatus by 1st Embodiment. It is an II-II arrow top view of FIG. 1 is a block diagram of a radiation detection apparatus according to a first embodiment. It is a typical perspective view of the radiation detection panel by 1st Embodiment. It is a circuit diagram of the image detection part by 1st Embodiment. It is a top view of the radiation detection panel by a 1st embodiment. It is a top view of the circuit board by the 1st embodiment. It is sectional drawing of the vicinity of the noise shield in the modification of the radiation detection apparatus of 1st Embodiment. It is sectional drawing of the radiation detection apparatus by 2nd Embodiment. It is a XX arrow top view of FIG. It is sectional drawing of the vicinity of the noise shield of the radiation detection apparatus by 3rd Embodiment.

A radiation detection apparatus according to an embodiment will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or similar structure, and the overlapping description is abbreviate | omitted.
[First Embodiment]
FIG. 3 is a block diagram of the radiation detection apparatus according to the first embodiment. FIG. 4 is a schematic perspective view of the radiation detection panel in the present embodiment. FIG. 5 is a circuit diagram of the image detection unit in the present embodiment.

  The radiation detection apparatus 30 includes a radiation detection panel 21, a gate driver 32, an integration amplifier 33, an A / D converter 34, a row selection circuit 35, and an image synthesis circuit 36. The radiation detection panel 21 includes a fluorescence conversion film 38 and an image detection unit 12. The fluorescence conversion film 38 generates fluorescence in the visible light region when the X-ray 37 enters. The generated fluorescence reaches the surface of the image detection unit 12.

  The image detection unit 12 receives the fluorescence generated by the fluorescence conversion film 38 and generates an electrical signal. As a result, the visible light image generated in the fluorescence conversion film 38 by the incident X-rays 37 is converted into image information expressed by an electrical signal in the image detection unit 12.

  The image detection unit 12 has a plurality of fine pixels arranged in a square lattice pattern. Each pixel is formed on the holding substrate 11. The holding substrate 11 is a plate made of glass. 3 and 4, the pixels are only described for 5 rows and 5 columns or 4 rows and 4 columns, but actually more pixels are formed according to the resolution and imaging area. In FIG. 3, the fluorescence conversion film 38 and the image detection unit 12 are drawn separately, but in reality they are in close contact.

  Each pixel includes a thin film transistor 14, a capacitor 15, and a photodiode 39. The photodiode 39 and the capacitor 15 are connected to the source terminal of the thin film transistor 14 in parallel. The gate terminal of the thin film transistor 14 is connected to the gate line 13. The drain terminal of the thin film transistor 14 is connected to the signal line 17.

  The gate lines 13 are provided in the same number as the number of rows of the grid in which the pixels are arranged, and the gate terminals of the thin film transistors 14 in the pixels in the same row are connected to the same gate line. The signal lines 17 are provided in the same number as the number of columns of the grid in which the pixels are arranged, and the gate terminals of the thin film transistors 14 in the pixels in the same column are connected to the same gate line.

  Each gate line 13 is connected to a gate driver 32. There are a plurality of gate drivers 32, for example. The gate driver 32 is connected to the row selection circuit 35. The gate driver 32 receives a signal from the row selection circuit 35 and sequentially changes the voltages of the many gate lines 13. The row selection circuit 35 sends a signal for selecting a predetermined row for scanning the X-ray image to the gate driver 32.

  Each signal line 17 is connected to an integrating amplifier 33. The integrating amplifier 33 amplifies and outputs a very small charge signal output from the radiation detection panel 21 through the signal line 17. The integrating amplifier 33 is connected to the A / D converter 34. The A / D converter 34 is connected to the image composition circuit 36.

  FIG. 6 is a plan view of the radiation detection panel according to the present embodiment.

  The radiation detection panel 21 is formed with a terminal group 61 for drawing out the gate line 13 and the signal line 17. The terminal group 61 that pulls out the gate line 13 and the terminal group 61 that pulls out the signal line 17 are arranged along the adjacent sides of the radiation detection panel 21 in the vicinity of those sides. A moisture barrier 65 that covers the fluorescence conversion film 38 may be fixed to the radiation detection panel 21.

  FIG. 7 is a plan view of the circuit board in the present embodiment.

  The gate driver 32, the row selection circuit 35, the A / D converter 34, the image composition circuit 36, and the like are formed on the circuit board 23. On the circuit board 23, a terminal group 62 for connecting the electric circuit to the gate line 13 and the signal line 17 of the radiation detection panel 21 is formed. The terminal group 62 connected to the gate line 13 and the terminal group 62 connected to the signal line 17 are arranged along the adjacent sides of the circuit board 23 in the vicinity of those sides.

  FIG. 1 is a cross-sectional view taken along the line II of FIG. 2 of the radiation detection apparatus according to the present embodiment. 2 is a plan view taken along the line II-II in FIG.

  The radiation detection device 30 has a housing 22. The housing 22 is a box in which an opening covered with the radiation incident window 19 is formed on the X-ray detection surface side.

  Inside the housing 22, a radiation detection panel 21, a support plate 20, a circuit board 23, a noise shield 24 and a flexible board 18 are housed. The support plate 20 is, for example, a square flat plate. The support plate 20 may be composed of a plurality of plates. Moreover, the board which comprises the support plate 20 may contain the board | plate made from lead which shields an X-ray, for example. The support plate 20 is fixed to the housing 22 with a support pillar (not shown).

  In the radiation detection panel 21, the surface opposite to the incident surface of the X-ray 37, that is, the surface opposite to the surface on which the TFT circuit layer 10 or the like of the holding substrate 11 is formed is placed on one surface of the support plate 20. Has been. The opposite surface of the radiation detection panel 21 to the support plate 20 is pressed against the support plate 20 by a pressing member 64 fixed to the inner surface of the housing 22.

  The circuit board 23 is fixed to the support plate 20 by circuit board support pillars 25. A flexible substrate 18 extends between the radiation detection panel 21 and the circuit board 23. The flexible substrate 18 extends outside the outer edge of the support plate 20. That is, the flexible substrate 18 passes between the outer edge of the support plate 20 and the side surface of the housing 22. The terminal group 61 arranged in the peripheral portion of the radiation detection panel 21 and the terminal group 62 arranged in the peripheral portion of the circuit board 23 are extended.

  The noise shield 24 includes a fixed part 51 and a shield part 52. The fixing portion 51 is formed in a plate shape that extends along the circuit board 23. The shielding part 52 is formed in a plate shape standing from the fixing part 51 in the direction from the circuit board 23 toward the support plate 20. Further, the shielding part 52 extends across at least a part of an element such as the gate driver 32 located on the circuit board 23 and the flexible board 18. The noise shield 24 is made of a conductive material such as aluminum, stainless steel, or copper. The noise shield 24 is produced by integrally forming the fixing portion 51 and the shielding portion 52 by, for example, extruding metal.

The fixing part 51 is fixed to the circuit board 23 using, for example, screws 53 . The circuit board 23 has a portion where the ground of the circuit formed on the circuit board 23 is exposed, and the fixing portion 51 is in contact with the portion where the ground is exposed. Further, the end of the shielding part 52 opposite to the fixed part 51 is in contact with the support plate 20.

  Next, the operation of the radiation detection apparatus 30 will be described.

In the initial state, a charge is stored in the capacitor 15 connected in parallel with the photodiode 39, and a reverse bias voltage is applied to the photodiode 39 connected in parallel. This voltage is the same as the voltage applied to the signal line 17. Since the photodiode 39 is a kind of diode, even if a reverse bias voltage is applied, almost no current flows. Therefore, the electric charge stored in the capacitor 15 is held without decreasing.

  In such a situation, when X-rays 37 are incident on the fluorescence conversion film 38, high-energy X-rays are converted into a large amount of low-energy visible light inside the fluorescence conversion film 38. Part of the fluorescence generated inside the fluorescence conversion film 38 reaches the photodiode 39 disposed on the surface of the image detection unit 12.

Fluorescence incident on the photodiode 39 is converted into charge consisting of electrons and holes inside the photo diode 39, along the direction of an electric field is applied by the capacitor 15 to reach the both terminals with the photodiode 39. This charge movement is observed as a current flowing through the photodiode 39 .

The current flowing inside the photodiode 39 generated by the incidence of fluorescence flows into the capacitor 15 connected in parallel. Along with this, the electric charge stored in the capacitor 15 is canceled. As a result, the charge stored in the capacitor 15 decreases, and the potential difference generated between the terminals of the capacitor 15 also decreases compared to the initial state.

  The gate driver 32 has a function of changing the potentials of a large number of gate lines 13 in order. At a specific time, only one gate line 13 is changed in potential by the gate driver 32. Between the source terminal and the drain terminal of the thin film transistor 14 connected in parallel to the signal line 17 connected to the gate line 13 whose potential has changed, the state changes from an insulated state to a conductive state. A specific voltage is applied to each signal line 17. The voltage applied to the signal line is applied to the capacitor 15 connected through the source and drain terminals of the thin film transistor 14 connected to the gate line 13 whose potential has changed.

Since the capacitor 15 is in the same potential state as that of the signal line 17 in the initial state, when the charge amount of the capacitor 15 is not changed from the initial state, no charge transfer from the signal line 17 occurs in the capacitor 15. However, in the capacitor 15 connected in parallel with the photodiode 39 into which the fluorescence generated inside the fluorescence conversion film 38 is incident by the X-ray 37 incident from the outside, the charge stored inside is reduced, and the initial value is reduced. The potential of the state has changed. For this reason, the movement of the charge is generated from the signal line 17 through the thin film transistor 14 in the conductive state, and the amount of charge stored in the capacitor 15 returns to the initial state. Further, the amount of the electric charge that has moved becomes a signal flowing through the signal line 17 and is transmitted to the outside.

The current flowing through the signal line 17 is input to the corresponding integrating amplifier 33. The integrating amplifier 33 integrates the current that flows within a predetermined time, and outputs a voltage corresponding to the integrated value to the outside. By performing this operation, the amount of charge flowing through the signal line 17 within a certain time can be converted into a voltage value. As a result, the charge signal generated in the photodiode 39 corresponding to the fluorescence intensity distribution generated in the fluorescence conversion film 38 by the X-ray 37 is converted into potential information by the integrating amplifier 33.

  The potential generated in the integrating amplifier 33 is sequentially converted into a digital signal by the A / D converter 34. The signals that have become digital values are sequentially arranged in accordance with the rows and columns of pixels arranged inside the image detection unit 12 inside the image composition circuit 36, and are output to the outside as image signals.

  By continuously performing these operations, the X-ray image information incident from the outside is converted into image information by an electric signal and output to the outside. Image information based on an electrical signal output to the outside is imaged by, for example, a general display device, and an X-ray image can be observed as an image by visible light by the image.

When such a radiation detection apparatus 30 is driven, noise is generated from the circuit board 23 which is a part of the radiation detection apparatus 30. For example, the power supply circuit thus formed in the element such as a coil and a capacitor on the circuit board 23 is one of the major noise sources. An element such as the gate driver 32 can also be a noise generation source. The generated noise may affect the charge signal output from the radiation detection panel 21. In particular, the flexible substrate 18 that transmits a minute charge signal detected by the radiation detection panel 21 to the circuit substrate 23 is easily affected by noise. For this reason, when the influence of noise reaches the flexible substrate 18, an image signal having a particularly large noise component may be acquired.

  However, the radiation detection apparatus 30 according to the present embodiment stands up in a direction from the circuit board 23 toward the support plate 20 and extends across at least a part of the elements located on the circuit board 23 and the flexible board 18. A noise shield 24 having a plate-like shield 52 is provided. For this reason, the noise generated by the element located on one side of the flexible substrate 18 with respect to the shielding portion 52 is blocked by the shielding portion 52 and hardly reaches the opposite flexible substrate 18 side. For this reason, in the radiation detection apparatus 30 of this Embodiment, it is hard to receive the influence of the noise which generate | occur | produced itself. As a result, the image information based on the electrical signal output from the radiation detection device 30 is less affected by noise.

  In particular, an electrical signal that flows through the flexible board 18 due to noise generated by the noise generation source by providing the shield 52 so as to cross between the power supply circuit and other noise generation sources located on the circuit board 23 and the flexible board 18. Can be reduced. In particular, when the integrating amplifier 33 that is susceptible to noise is mounted on the flexible substrate 18, the influence of the noise on the image information is extremely small by preventing the influence of the noise on the flexible substrate 18. Become.

  In the present embodiment, the terminal group 62 provided on the circuit board 23 and connected to the flexible board 18 is provided on the periphery of the flexible board 18. No electrical element is arranged on the outer edge side of the terminal group 62 of the circuit board 23. For this reason, by providing the shielding part 52 so as to extend along the terminal group 62 in the vicinity of the terminal group 62 of the circuit board 23, the shielding part 52 is connected to the power supply circuit and other noise generation sources located on the circuit board 23. It is possible to cross between the flexible substrate 18.

  Further, the circuit board 23 has a portion where the ground is exposed, and the portion where the ground is exposed is in contact with the fixing portion 51. Further, the shielding part 52 is in contact with the support plate 20. For this reason, if the noise shield 24 and the portion of the support plate 20 in contact with the noise shield 24 are conductive, the ground of the circuit board 23 is electrically connected to a large conductive member. As a result, the potential of the ground (grounding portion) of the radiation detection apparatus 30 is stabilized, the operation stability is improved, and the influence of noise is reduced.

  Since the noise shield 24 has a shape in which plates are combined, it can be easily manufactured by, for example, extrusion molding. Alternatively, the noise shield 24 can be easily manufactured by bending a metal flat plate. Therefore, the time and cost required for the molding process can be reduced.

  Since the support plate 20 of the radiation detection apparatus 30 needs to have a certain level of strength, it tends to be relatively heavy. Furthermore, when the support plate 20 is provided with an X-ray shielding effect, it is necessary to use a heavy metal such as lead, which is heavy. For this reason, the radiation detection apparatus 30 tends to increase in weight. However, the noise shield 24 according to the present embodiment has a shape in which thin portions such as plates are combined, so that the space between the noise generation source and the flexible substrate 18 is smaller than when a solid prism or the like is used. The amount of material used can be reduced while keeping the same crossing area. Thereby, the material cost is reduced and the weight is reduced.

  FIG. 8 is a cross-sectional view of the vicinity of the noise shield in the modification of the present embodiment.

  The noise shield 24 in this modification is formed in a square pipe shape in which two parallel fixing parts 51 and two parallel shielding parts 52 are combined. The noise shield 24 of this modification can be manufactured by, for example, extrusion molding.

By using such a noise shielding body 24, the rigidity can be increased as compared with the case where each of the fixing portion 51 and the shielding portion 52 is one. For this reason, it is effective when the noise shield 24 requires high rigidity, such as when the circuit board 23 is supported by fixing the two fixing portions 51 of the noise shield 24 to the circuit board 23 and the support plate 20. .
[Second Embodiment]
FIG. 9 is a cross-sectional view of the radiation detection apparatus according to the second embodiment taken along the arrow IX-IX in FIG. FIG. 10 is a plan view taken along arrow XX in FIG.

  In the present embodiment, the circuit board 23 is divided into two. On one circuit board 23, an electric circuit for controlling the radiation detection panel 21 and processing signals transmitted from the radiation detection panel is formed, in addition to the gate driver 32. On the other circuit board 23, a power supply circuit for driving the radiation detection apparatus 30 is formed.

  As in this embodiment, by forming a power supply circuit that can be a main source of noise affecting signal processing on a circuit board 23 different from the electric circuit for signal processing, signal processing is performed. Less susceptible to noise. However, by forming these circuits on another circuit board 23, there are cases in which the ground connection of each circuit is only a thin conductor or independent of each other. In such a case, the potential at each part of the ground of the radiation detection apparatus may be slightly different.

In the present embodiment, the grounds of the plurality of circuit boards 23 are electrically coupled by the conductive noise shield 24. For this reason, the difference in potential of each part of the ground of the plurality of circuit boards 23 can be reduced.
[Third Embodiment]
FIG. 11 is a cross-sectional view of the vicinity of the noise shield of the radiation detection apparatus according to the third embodiment.

In the radiation detection apparatus according to the present embodiment, the noise shielding body 24 has the shielding portions 52 standing on the long sides of the single fixing portion 51. The edges of these shielding parts 52 on the support plate 20 side are not in contact with the support plate 20. Further, for example, a columnar spacer 54 is disposed between the fixing portion 51 and the support plate 20. The spacer 54 is made of a conductive material.

Even if the edge of the shielding part 52 on the support plate 20 side is not in contact with the support board 20, the shielding part 52 is located between the flexible substrate 18 and the noise generation source on the circuit board 23. By doing so, the influence of noise can be reduced. In particular, it has been confirmed by experiments that a sufficient noise reduction effect can be obtained if the gap 27 between the edge of the shielding portion 52 and the support plate 20 is about 0.5 mm or less. In addition, by arranging the conductive spacer 53 between the noise shield 24 and the support plate 20, the ground of the circuit board 23 can be electrically connected to the large support plate 20.
[Other embodiments]
Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 ... TFT circuit layer, 11 ... Holding substrate, 12 ... Image detection part, 13 ... Gate line, 14 ... Thin-film transistor, 15 ... Condenser , 17 ... Signal line, 18 ... Flexible substrate, 19 ... Radiation incident window, 20 ... Support plate 21 ... Radiation detection panel, 22 ... Housing, 23 ... Circuit board, 24 ... Noise shield, 25 ... Circuit board support column, 27 ... Gap, 30 ... Radiation detection device, 32 ... Gate driver, 33 ... Integration amplifier, 34 ... A / D converter, 35 ... row selection circuit, 36 ... image composition circuit, 37 ... X-ray, 38 ... fluorescence conversion film, 39 ... photodiode, 51 ... fixing part, 52 ... shielding part, 53 ... screw , 54 ... Spacer , 61 ... Terminal group, 62 ... Terminal group, 63 ... Element, 64 ... Pressing member, 65 ... Moisture-proof body

Claims (5)

A radiation detection panel comprising a first terminal group for detecting radiation incident on the incident surface and outputting an electrical signal;
A support plate for supporting a surface opposite to the incident surface of the radiation detection panel;
A circuit board that has a second terminal group and is positioned on the opposite side of the radiation detection panel of the support plate to drive the radiation detection panel;
A flexible substrate that extends between the first terminal group and the second terminal group through the outer side of the outer edge of the support plate and is electrically connected;
A plate-shaped fixing portion extending along the circuit board, and at least a part of the element standing on the circuit board in a direction from the circuit board toward the support plate and between the flexible board and the flexible board A conductive noise shield having a plate-like shield extending across
An integrating amplifier that is mounted on the flexible substrate and integrates and amplifies the electrical signal output by the radiation detection panel;
Comprising
The radiation detection apparatus according to claim 1, wherein the flexible substrate and the integration amplifier are provided on a side opposite to the element side with the shielding portion interposed therebetween.   The radiation detection apparatus according to claim 1, wherein the shielding portion extends along an arrangement direction of terminals of the second terminal group. The circuit board has a ground exposed portion, the fixing portion contacts the ground exposed portion of the circuit board, and the support plate is positioned on the side facing the circuit board to shield radiation. the radiation detector according to claim 1 or 2 having a metal radiation shield plate, said noise shielding member is characterized by being electrically connected to the radiation shield plate for. The radiation detector according to claim 3 , further comprising a conductive spacer extending between the fixing portion and the support plate. The radiation detection apparatus according to any one of claims 1 to 4, wherein the fixing part and the shielding part are integrally formed by either extrusion molding or bending of a plate material.

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