A flat panel detector

Abstract

The present application relates to a kind of flat panel detector, belong to flat panel detector technical field, including scintillation crystal, two opposite sides of scintillation crystal are coupled with photoelectric detector, one photoelectric detector is aligned with scintillation crystal setting, another photoelectric detector is misaligned with scintillation crystal setting, the structure of 2 photoelectric detectors is same, the present application can solve the technical problems of existing technology limited to pixel size, cannot significantly improve the inherent resolution of flat panel detector.

Description

Technical Field

[0001] This invention belongs to the field of flat panel detector technology, and specifically relates to a flat panel detector. Background Technology

[0002] Currently, most X-ray imaging equipment (DR, CBCT) uses scintillation crystal (CsI, GOS) coupled flat-panel detectors to detect X-rays, such as... Figure 1 As shown. Scintillation crystals use cesium iodide (CsI) or gadolinium oxysulfide (GOS) to convert X-rays into visible light. A photodetector array, composed of several photoconverter pixels, converts visible light into electrical signals. Readout electronics then read out the electrical signals of the array according to their positions, thus obtaining the light intensity at different locations in the pixel array, which represents the intensity of X-rays at those locations. A flat-panel detector composed of numerous pixels has an inherent positional resolution equal to the geometric size of a single pixel (photodiode). Generally, under current amorphous silicon technology, the dimensions of a single photodiode (pixel) are approximately 100µm x 100µm.

[0003] Existing methods to improve the inherent resolution of flat panel detectors involve reducing the design size of individual photodiodes. This necessitates redesigning photoelectric converter arrays with new pixel sizes, resulting in long lead times, high costs, and significant risks. Furthermore, the size of individual pixels cannot be reduced indefinitely; smaller pixel sizes mean a smaller fill factor, a smaller effective detection area, a lower signal-to-noise ratio per pixel, and lower detection efficiency. Summary of the Invention

[0004] To address the shortcomings of existing technologies, a flat panel detector is proposed to solve the technical problem that existing technologies are limited by pixel size and cannot significantly improve the inherent resolution of flat panel detectors.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A flat panel detector includes a scintillation crystal, with photodetectors coupled to two opposite sides of the scintillation crystal. One photodetector is aligned with the scintillation crystal, while the other photodetector is offset from the scintillation crystal. The two photodetectors have the same structure.

[0007] The technical solution is further configured such that, along the thickness direction of the flat panel detector, the scintillation crystal is aligned with the two photodetectors, and the misalignment direction of the scintillation crystal and the photodetectors, the thickness direction of the flat panel detector, and the rotation direction of the flat panel detector are orthogonal.

[0008] The technical solution is further configured such that the misalignment distance between the scintillation crystal and the photodetector is equal to half the size of a single pixel of the photodetector.

[0009] The technical solution is further configured such that an optical adhesive coating layer is provided on the coupling surface between the scintillation crystal and the photodetector.

[0010] The technical solution is further configured such that the two photodetectors are respectively connected to the same data readout module, and the data readout of the two photodetectors is synchronously timed.

[0011] The technical solution is further configured such that both the scintillation crystal and the photodetector that are misaligned with it have non-overlapping areas, and the non-overlapping areas are provided with light-shielding layers.

[0012] The technical solution is further configured such that the scintillation crystal is the same size as the photodetector.

[0013] This technical solution is further configured such that the pixel array of the photodetector is M×N, the pixel size is P×P, the photodetector and the scintillation crystal are misaligned by P / 2, and the scintillation crystal is equivalently divided into a pixel array with a pixel size of P / 2×P. The signal strength read by each pixel in the photodetector misaligned with the scintillation crystal is A. ij The signal strength read by each pixel in the photodetector aligned with the scintillation crystal is B. ij Where i represents the number of rows in the pixel array, i≤M, j represents the number of columns in the pixel array, j≤N, and S is the number of pixels corresponding to the pixel array on the scintillation crystal. in Where i represents the number of rows in the pixel array, i≤M, and n represents the number of columns in the pixel array, n=2j, n≤2N, then:

[0014] When n=1, S i1 =A i1 ;

[0015] When n≥2 and n is even, S in =B ij -S i(n-1) S i(n+1) =A i(j+1) -S in .

[0016] The beneficial effects of this invention are:

[0017] Without altering the pixel array of the photodetector, a "sandwich" structure is formed by coupling two photodetectors with a single-layer scintillation crystal. Simultaneously, one of the photodetectors needs to be misaligned with the scintillation crystal to improve the resolution of the intrinsic position of the flat panel detector. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a flat panel detector in existing technology;

[0019] Figure 2 This is a schematic diagram of the flat panel detector used in an embodiment of the present invention;

[0020] Figure 3 This is a schematic diagram of the scintillation crystal being equivalently segmented in an embodiment of the present invention;

[0021] Figure 4 yes Figure 3 Partial schematic diagram at point C;

[0022] Figure 5 This is a schematic diagram illustrating the application of the flat panel detector in an embodiment of the present invention.

[0023] In the attached diagram: 1-scintillation crystal, 2-first photodetector, 3-second photodetector, 4-shielding layer. Detailed Implementation

[0024] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Based on the embodiments in this application, other similar embodiments obtained by those skilled in the art without creative effort should all fall within the scope of protection of this application. Furthermore, directional terms mentioned in the following embodiments, such as "up," "down," "left," and "right," are only for reference to the directions in the accompanying drawings; therefore, the directional terms used are for illustrative purposes and not for limiting the invention.

[0025] According to an embodiment of the present invention, a flat panel detector is provided; please refer to [link / reference]. Figure 2 The scintillation crystal 1 is included, and photodetectors are coupled to two opposite sides of the scintillation crystal 1. One photodetector is aligned with the scintillation crystal 1, and the other photodetector is misaligned with the scintillation crystal 1. The two photodetectors have the same structure.

[0026] Specifically, the two photodetectors are a first photodetector 2 and a second photodetector 3. The first photodetector 2 is aligned with the scintillation crystal 1, while the second photodetector 3 is offset from the scintillation crystal 1. The first photodetector 2 and the second photodetector 3 have the same structure, and both can independently receive visible light emitted by the scintillation crystal 1. Furthermore, the scintillation crystal 1 has the same size as the first photodetector 2 and the second photodetector 3.

[0027] It should be noted that, without changing the pixel array of the photodetector, a "sandwich" sandwich structure is formed by coupling two photodetectors with a single-layer scintillation crystal 1. At the same time, one of the photodetectors needs to be misaligned with the scintillation crystal 1 to improve the resolution of the intrinsic position of the flat panel detector.

[0028] In this embodiment, see the flat panel detector. Figure 2 as well as Figure 5 Along the thickness direction of the flat panel detector, the scintillation crystal 1 is aligned with the two photodetectors, and the misalignment direction of the scintillation crystal 1 and the photodetectors, the thickness direction of the flat panel detector, and the rotation direction of the flat panel detector are orthogonal.

[0029] In practical cone-beam CT applications, the X-ray passes through the first photodetector 2 before reaching the scintillation crystal 1, below which lies the second photodetector 3. The thickness direction of the flat panel detector is along the Y-axis, and the detector rotates around the Z-axis without changing the detection resolution in the Z-axis direction. The second photodetector 3 is misaligned with the scintillation crystal 1 along the X-axis, halving the detection resolution in the X-axis direction. The Z-axis pixel size affects the slice thickness of the tomographic scan, while the X-axis pixel size affects the image resolution.

[0030] In this embodiment, see the flat panel detector. Figures 2 to 4 The misalignment distance between the scintillation crystal 1 and the second photodetector 3 is equal to half the size of a single pixel of the second photodetector 3.

[0031] In this embodiment, see the flat panel detector. Figures 2 to 4 An optical adhesive coating layer is provided on the coupling surface between the scintillation crystal 1 and the photodetector.

[0032] In this embodiment, see the flat panel detector. Figures 2 to 4 The scintillation crystal 1 and the second photodetector 3 are misaligned to form a non-overlapping area, and the non-overlapping area is provided with a light-shielding layer 4. Specifically, the non-overlapping area is located at the edge of the scintillation crystal 1 and the second photodetector 3.

[0033] The first photodetector 2 is coupled along the thickness direction of the scintillation crystal 1. Optical adhesive is applied to the coupling surface of both to form an optical adhesive coating layer, eliminating air gaps, and the two are perfectly aligned and coupled edge-to-edge. Then, the second photodetector 3 is placed opposite the first photodetector 2, also along the thickness direction of the scintillation crystal 1. Optical adhesive is also applied to the coupling surface of both. It is important to note that the scintillation crystal 1 and the second photodetector 3 need to be offset by half a pixel. Precise positioning is required during installation. A microscope and laser pointer are used for alignment. The outermost column of exposed pixels of the second photodetector 3 is blackened to form a light-shielding layer 4 to prevent light signal interference. At the same time, the part of the scintillation crystal 1 that is not fully coupled with the second photodetector 3 is also blackened to form a light-shielding layer to prevent external light signal interference. The first photodetector 2, scintillation crystal 1, and second photodetector 3 are aligned in the thickness direction.

[0034] In this embodiment, see the flat panel detector. Figures 2 to 5 Two photodetectors are connected to the same data readout module, and the data readout of the two photodetectors is synchronized with the timing control.

[0035] It should be noted that the signal readout control of the first photodetector 2 and the second photodetector 3 must be synchronized. After absorbing X-rays, the scintillation crystal 1 emits visible light to both sides simultaneously, and both the first photodetector 2 and the second photodetector 3 can receive the visible light. The first photodetector 2 and the second photodetector 3 are subject to the timing control of the same data readout module (or circuit), and begin signal integration and collection at the same time. The integration and collection time is the same, and then the signal integration and collection stops at the same time. Then, the signal data of the first photodetector 2 and the second photodetector 3 are read out respectively.

[0036] In this embodiment, see the flat panel detector. Figures 2 to 5 The pixel arrays of the first photodetector 2 and the second photodetector 3 are M×N, with pixel sizes of P×P. The second photodetector 3 is offset from the scintillation crystal 1 by P / 2, effectively dividing the scintillation crystal 1 into a pixel array with a pixel size of P / 2×P. This allows the inherent resolution of the flat panel detector to be reduced by half, with the pixel's inherent resolution changing from P to P / 2. In the other direction of the flat panel detector, the size of the virtually divided pixels remains P, meaning the slice thickness remains unchanged in CT applications. In other words, within the limits of technology and physics, the inherent resolution of the flat panel detector is doubled. For example, with a pixel size of 100um x 100um, the inherent resolution is increased by 50um; with a pixel size of 70um x 70um, the inherent resolution is increased by 35um.

[0037] Let the signal strength read by each pixel in the second photodetector 3 be A.ij The signal strength read by each pixel in the first photodetector 2 is B. ij Where i represents the number of rows in the pixel array, i≤M, j represents the number of columns in the pixel array, j≤N, and the number of pixels corresponding to the pixel array on scintillation crystal 1 is S. in Where i represents the number of rows in the pixel array, i≤M, and n represents the number of columns in the pixel array, n=2j, n≤2N, then:

[0038] When n=1, S i1 =A i1 ;

[0039] When n≥2 and n is even, S in =B ij -S i(n-1) S i(n+1) =A i(j+1) -S in .

[0040] Specifically, when the scintillation crystal 1 absorbs X-rays and emits visible light that reaches the surface of the first photodetector 2, the size P×P of each pixel signal of the first photodetector 2 can be completely read due to the complete coupling between the two. The second photodetector 3 is offset by half a pixel size, that is, the outermost column of the second photodetector 3 is divided into pixels of size P / 2×P. The region where this pixel is coupled with the scintillation crystal 1 is S11. Therefore, the signal intensity read by A11 in the second photodetector 3 is the signal intensity of the S11 region. Similarly, the relationship between the size of each pixel signal of the first photodetector 2 and the second photodetector 3 and the pixel size S of the scintillation crystal 1 that is virtually divided can be obtained.

[0041] A11 = S11;

[0042] A12 = S12 + S13;

[0043] A13 = S13 + S14;

[0044] …

[0045] B11 = S11 + S12;

[0046] B12 = S13 + S14;

[0047] …

[0048] Based on the above equations, we can obtain:

[0049] S1 1 = A11;

[0050] S12 = B11 – A11;

[0051] S13 = A12 – S12;

[0052] S14 = B12 – S13;

[0053] …

[0054] It should be noted that the flat panel detector is a photodiode (PIN) type flat panel detector, which mainly includes a switching element and a photoelectric conversion unit. The switching element includes a thin film transistor (TFT), and the photoelectric conversion unit includes a photodiode (PIN). Under X-ray illumination, the scintillation crystal 1 of the flat panel detector converts X-ray photons into visible light, and then, under the action of the PIN, converts the visible light into an electrical signal. Finally, the TFT reads the electrical signal and outputs it to obtain the displayed image.

[0055] The present invention has been described in detail above. The above description is only a preferred embodiment of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of this application should still fall within the scope of the present invention.

Claims

1. A flat panel detector, characterized in that, The system includes a scintillation crystal, with photodetectors coupled to both opposite sides of the scintillation crystal. One photodetector is aligned with the scintillation crystal, while the other photodetector is misaligned with it. The two photodetectors have the same structure and are connected to the same data readout module. The data readout from the two photodetectors needs to be synchronized and timed. Along the thickness direction of the flat panel detector, the scintillation crystal is aligned with two photodetectors. The misalignment direction of the scintillation crystal and the photodetectors, the thickness direction of the flat panel detector, and the rotation direction of the flat panel detector are orthogonal. The misalignment distance between the scintillation crystal and the photodetectors is equal to half the size of a single pixel of the photodetector.

2. A flat panel detector according to claim 1, characterized in that, An optical adhesive coating is provided on the coupling surface between the scintillation crystal and the photodetector.

3. A flat panel detector according to claim 1, characterized in that, Both the scintillation crystal and the photodetector that are misaligned with it have non-overlapping areas, and the non-overlapping areas are provided with light-shielding layers.

4. A flat panel detector according to claim 1, characterized in that, The scintillation crystal is the same size as the photodetector.

5. A flat panel detector according to any one of claims 1-4, characterized in that, The photodetector has an M×N pixel array with a pixel size of P×P. The photodetector and the scintillation crystal are misaligned by P / 2, effectively dividing the scintillation crystal into a pixel array with a pixel size of P / 2×P. The signal strength read by each pixel in the photodetector misaligned with the scintillation crystal is A. ij The signal strength read by each pixel in the photodetector aligned with the scintillation crystal is B. ij Where i represents the number of rows in the pixel array, i≤M, j represents the number of columns in the pixel array, j≤N, and S is the number of pixels corresponding to the pixel array on the scintillation crystal. in Where i represents the number of rows in the pixel array, i≤M, and n represents the number of columns in the pixel array, n=2j, n≤2N, then: When n=1, S i1 =A i1 ; When n≥2 and n is even, S in = B ij -S i(n-1) S i（n+1） = A i(j+1) -S in .

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