Flat panel detector, and method and device for using flat panel detector

Abstract

The invention discloses a flat panel detector and a method and device for using the flat panel detector. A flat panel detector is constructed on the basis of an amorphous silicon substrate on which a hexagonal pixel pattern is uniformly laid. The hexagonal pixels can be arranged more closely on a two-dimensional plane, and gaps among the pixels are reduced, so that a photosensitive area is maximized with a relatively high filling rate, and the spatial resolution of the detector is improved. And the hexagonal pixels enable a frequency space to generate an angle of 60 degrees, so that the influence of grid artifacts is reduced to a certain extent. Meanwhile, the hexagonal pixel array is effectively processed and optimized by adopting an image reconstruction algorithm, the signal-to-noise ratio of the single pixel of the flat panel detector is improved, and the definition and accuracy of the image are improved.

Description

A flat panel detector, a method and apparatus for using the flat panel detector Technical Field

[0001] This application relates to the field of flat panel detector technology, and in particular to a flat panel detector, a method and apparatus for using a flat panel detector. Background Technology

[0002] Digital radiography (DR) is widely used in the medical and imaging fields due to its advantages such as fast imaging speed, convenient operation, and high imaging resolution. The quality of DR imaging is inseparable from the flat panel detector. The principle of the amorphous silicon flat panel detector is as follows: a scintillator layer is placed on the top layer to convert incident X-rays into visible light photons; an amorphous silicon pixel array is placed on the second layer to absorb the visible light from the scintillator layer. These electrons are collected to form stored charges proportional to the X-ray intensity. The stored charge of each pixel is scanned and read out by the control circuit at the bottom layer, thereby forming an image and obtaining a digital X-ray image.

[0003] In existing technologies, amorphous silicon flat panel detectors are generally designed with a matrix pixel structure, and the resulting matrix pixel flat panel detectors are widely used. They meet different imaging requirements by adjusting the size and resolution of the matrix. However, when the matrix pixels are arranged, the spacing between the pixels affects the imaging effect. Therefore, how to improve amorphous silicon flat panel detectors to achieve higher quality image acquisition and imaging has become an urgent problem to be solved. Summary of the Invention

[0004] To address the aforementioned issues, this application provides a flat panel detector, a method for using the flat panel detector, and an apparatus for improving amorphous silicon flat panel detectors to achieve higher quality image acquisition and imaging.

[0005] This application discloses a flat panel detector, including: a substrate, electrodes, a readout circuit, and connecting lines connecting the electrodes and the readout circuit;

[0006] The substrate is uniformly covered with a pattern of hexagonal pixels; the substrate material is amorphous silicon.

[0007] The electrodes are disposed at the top or bottom of each hexagonal pixel for collecting charge;

[0008] The readout circuit is integrated and packaged with the substrate to obtain the amorphous silicon flat panel detector.

[0009] Optionally, the readout circuit includes: a thin-film transistor array, an analog-to-digital converter, and a charge amplifier;

[0010] The thin-film transistor array is used to control the charge input to the analog-to-digital converter;

[0011] The analog-to-digital converter is used to convert the charge into a digital signal and send it to the charge amplifier;

[0012] The charge amplifier is used to amplify the digital signal.

[0013] Optionally, the flat panel detector further includes a scintillator layer that converts rays into visible photons;

[0014] The substrate is disposed below the scintillator layer;

[0015] The substrate is used to collect the charge generated by the visible photon excitation.

[0016] Optionally, the flat panel detector further includes a heat dissipation element for heat dissipation of the flat panel detector.

[0017] Optionally, the flat panel detector further includes a support structure and / or a sealing device for protecting the flat panel detector.

[0018] Based on the aforementioned flat panel detector, this application also discloses a method for using the flat panel detector, the method being applied to the aforementioned flat panel detector, comprising:

[0019] The object is scanned with X-rays from multiple angles to obtain projection data; the projection data includes the projection angle and the distance between the X-ray and the center of rotation.

[0020] The projection data is projected back into the image space along the path of the X-ray to obtain a reconstructed image.

[0021] Optionally, after acquiring the projection data, the method further includes:

[0022] The projection data is then filtered.

[0023] Optionally, the step of projecting the projection data back into the image space along the path of the X-ray to obtain the reconstructed image includes:

[0024] The formula for obtaining the reconstructed image is:

[0025]

[0026] In the formula, f is the reconstructed image, f(x,y) is the pixel value of the reconstructed image at point (x,y), p′ is the filtered projection data, θ is the projection angle, r is the distance from the rotation center to the intersection of the X-ray and the detector, and h(r-xcosθ-ysinθ) is the interpolation or filtering function in the back projection process.

[0027] Optionally, after obtaining the reconstructed image, the method further includes:

[0028] The reconstructed image is post-processed; the post-processing includes one or more of the following: smoothing filtering, edge enhancement, and contrast adjustment.

[0029] Based on the aforementioned flat panel detector, this application also discloses an apparatus using a flat panel detector, comprising: a scanning unit and a reconstruction unit;

[0030] The scanning unit is used to perform X-ray scanning on an object from multiple angles to acquire projection data; the projection data includes the projection angle and the distance between the X-ray and the center of rotation.

[0031] The reconstruction unit is used to project the projection data back into the image space along the path of the X-ray to obtain a reconstructed image.

[0032] Optionally, the device further includes:

[0033] A filtering unit is used to filter the projection data.

[0034] Optionally, the formula for obtaining the reconstructed image is:

[0035]

[0036] In the formula, f is the reconstructed image, f(x,y) is the pixel value of the reconstructed image at point (x,y), p′ is the filtered projection data, θ is the projection angle, r is the distance from the rotation center to the intersection of the X-ray and the detector, and h(r-xcosθ-ysinθ) is the interpolation or filtering function in the back projection process.

[0037] Optionally, the device further includes:

[0038] A post-processing unit is used to perform post-processing on the reconstructed image; the post-processing includes one or more of smoothing filtering, edge enhancement, and contrast adjustment.

[0039] This application discloses a flat panel detector, a method for using the flat panel detector, and an apparatus for doing so. The flat panel detector is constructed based on an amorphous silicon substrate with a uniformly distributed pattern of hexagonal pixels. The hexagonal pixels can be arranged more densely in a two-dimensional plane, reducing the gaps between pixels and thus maximizing the photosensitive area with a higher fill rate, thereby improving the spatial resolution of the detector. Furthermore, the hexagonal pixels create a 60° angle in the frequency space, mitigating the influence of grid artifacts to some extent. Simultaneously, an image reconstruction algorithm is used to effectively process and optimize the hexagonal pixel array, improving the signal-to-noise ratio of a single pixel in the flat panel detector and enhancing image clarity and accuracy. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0041] Figure 1 is a schematic diagram of the structure of a flat panel detector disclosed in an embodiment of this application;

[0042] Figure 2 is a flowchart illustrating a method for using a flat panel detector disclosed in an embodiment of this application;

[0043] Figure 3 is a schematic diagram of a device using a flat panel detector disclosed in an embodiment of this application. Detailed Implementation

[0044] To facilitate understanding, the working principle of a flat panel detector will first be explained in detail: A flat panel detector typically consists of a scintillator layer, a pixel array, and a readout circuit. The top layer of the flat panel detector is the scintillator layer (made of cesium iodide or gadolinium oxysulfide). The scintillator converts incident X-rays into visible light photons, creating a gain of 1000 to 10000 times. The next layer is an amorphous silicon pixel array, which in current technology is designed with a matrix pixel structure. The visible light photons emitted by the scintillator layer are transmitted to the photodiodes of the amorphous silicon pixel array, where they are absorbed and converted into photocurrent (electrons). These electrons are then collected by the capacitance of the photodiodes, forming a stored charge proportional to the intensity of the incident X-rays. Under the control of the control circuit, the stored charge in the photodiode array of each pixel is read out sequentially. The control circuit typically includes a thin-film transistor (TFT) array, with each TFT connected to a photodiode as a switching element for the pixel. When the TFT is turned on, the stored charge on the photodiode is released and transferred to the readout circuit.

[0045] Matrix pixel flat panel detectors, as the mainstream technology, are still widely used in medical X-ray and CT (Computed Tomography) equipment, as well as in industrial inspection and security checks. Matrix pixel flat panel detectors can meet different imaging needs by adjusting the size and resolution of the matrix. However, they also have the following drawbacks: When arranging matrix pixels (such as common rectangular or square pixels), because the four corners of the photodiodes need to be rounded, the ratio of the effective photosensitive area of ​​the matrix pixel to the matrix area (fill rate) is relatively low, resulting in gaps between pixels. These gaps directly affect the continuity and sharpness of the image, especially when displaying or enlarging images at high resolutions, where the impact on image quality is more pronounced.

[0046] To address the aforementioned drawbacks, this application discloses a flat panel detector that uses hexagonal pixels as its substrate. Hexagons, being closer to circles than rectangles, maximize the photosensitive area, resulting in a higher fill rate. For example, at the same pixel size, the fill rate of hexagonal pixels can reach approximately 91%, while the fill rate of square pixels is typically around 80%, effectively improving the gap problem between pixels. Furthermore, matrix pixels tend to produce abrupt image transitions, while the arrangement of hexagonal pixels more closely resembles the natural visual pattern of the human eye, contributing to smoother image transitions.

[0047] Secondly, during the use of flat panel detectors, grid artifacts can occur. A grid is a physical component in the X-ray imaging optical path used to reduce X-ray scattering and improve the clarity and contrast of X-ray images. However, due to the interaction between the grid structure and X-rays, when X-rays pass through the human body and the grid, a specific interference pattern is generated in the image, i.e., grid artifacts. When using the flat panel detector with the hexagonal pixel substrate disclosed in this application, a 60° angle will be generated in the frequency space, which helps to eliminate grid artifacts.

[0048] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0049] Example 1: This application discloses a flat panel detector, a method for using the flat panel detector, and a method for imaging with the device.

[0050] Specifically, the flat panel detector disclosed in this embodiment includes: a substrate, electrodes, a readout circuit, and connecting lines connecting the electrodes and the readout circuit.

[0051] In the flat panel detector described in this embodiment, the arrangement and size of the hexagonal pixels are first determined. Then, computer-aided design software (such as CAD) is used for precise design to ensure that the shape, size, and position of each hexagonal pixel meet the design requirements. Next, a suitable semiconductor material is selected as the substrate for the flat panel detector, and the designed hexagonal pixel pattern is etched onto the substrate using microfabrication techniques such as photolithography and etching. Secondly, electrodes are fabricated at the top or bottom of each hexagonal pixel to collect the charge (current) generated by visible photons converted from the scintillator layer. The shape and position of the electrodes need to be precisely controlled to ensure good matching and effective contact with the hexagonal pixels. The electrode material is selected from metals or alloys with good conductivity and stability. Finally, connecting lines are designed to connect the electrodes of each hexagonal pixel to the readout circuit. These connecting lines have low resistance, high stability, and good signal transmission performance.

[0052] In the flat panel detector described in this embodiment, Figure 1 is a schematic diagram of the structure of a flat panel detector disclosed in this application embodiment. As shown in Figure 1, a pattern of hexagonal pixels is uniformly distributed on the substrate. As an optional material, the substrate material is amorphous silicon that is sensitive to light or rays of a specific wavelength. Rectangular electrodes are disposed at the top or bottom of each hexagonal pixel (Figure 1 shows an example of electrodes disposed at the top of a hexagonal pixel) for collecting charge. In Figure 1, the electrode and its placement position are shown in only one hexagonal pixel; in actual operation, each hexagonal pixel has one electrode. In the hexagonal pixel in Figure 1, a readout circuit is disposed below the electrode, which is responsible for receiving the weak signal from the hexagonal pixel and performing conversion and amplification processing.

[0053] As an optional method, the readout circuit includes a TFT array, an analog-to-digital converter (ADC), and a charge amplifier. The TFT array controls the charge input to the ADC. The ADC converts the charge into a digital signal and sends it to the charge amplifier. The charge amplifier amplifies the digital signal.

[0054] In the flat panel detector described in this embodiment, Figure 1a shows the gate driver, and the circuit marked in red is the gate line. When the readout circuit is working, the gate driver sequentially turns on the TFTs on each scan line, allowing the TFTs to charge / discharge their electrodes, thereby affecting the voltage across the TFT capacitors. Figure 1b shows the source driver, and the circuit marked in blue is the data line. The intersection points of the hexagonal pixels are the display points of the flat panel detector. When the waveform sent by the gate driver sequentially turns on the TFTs of each row, the source drivers of the entire row simultaneously charge the display points of the entire row to their respective required voltages to display different gray levels. When this row is fully charged, the gate driver turns off the voltage, and then the gate driver of the next row turns on the voltage, and the same source drivers charge and discharge the display points of the next row.

[0055] In the flat panel detector described in this embodiment, the readout circuit is integrated and packaged with the substrate to obtain the final flat panel detector. During the integration process, it is necessary to ensure that the electrical connections and physical supports between the various components meet the design requirements.

[0056] As an optional method, the flat panel detector described in this embodiment further includes a scintillator layer that converts rays into visible photons. A substrate is disposed below the scintillator layer and is used to collect the charge generated by the visible photon excitation.

[0057] As an optional method, considering that the flat panel detector may generate heat during operation, the flat panel detector in this embodiment further includes a heat dissipation element for dissipating heat from the flat panel detector. An effective thermal management scheme can be designed based on this heat dissipation element to ensure the stable operation of the flat panel detector. This heat dissipation element includes heat sinks, heat pipes, etc.

[0058] As an optional method, considering that the flat panel detector may be subjected to physical impact and vibration during operation, and may be affected by dust, the flat panel detector described in this embodiment also includes: a support structure and / or sealing device for protecting the flat panel detector.

[0059] The flat panel detector described in this embodiment is constructed based on an amorphous silicon substrate with a uniformly distributed pattern of hexagonal pixels. The hexagonal pixels can be arranged more densely in a two-dimensional plane, reducing the gaps between pixels and thus maximizing the photosensitive area with a higher fill rate, thereby improving the spatial resolution of the detector. Furthermore, the hexagonal pixels create a 60° angle in the frequency space, which to some extent mitigates the influence of grid artifacts.

[0060] Based on the flat panel detector disclosed in the above embodiments, this embodiment discloses a method for using the flat panel detector. The method is applied to the flat panel detector described above, as shown in Figure 2.

[0061] Step 101: Perform X-ray scanning on the object from multiple angles to obtain projection data.

[0062] In the method described in this embodiment, the projection data includes the projection angle and the distance (radial distance) between the X-ray and the center of rotation. This projection data can be denoted as p(θ,r).

[0063] As an alternative method, the acquired projection data can also be filtered to eliminate high-frequency noise and enhance image quality. Commonly used filters include the Ram-Lak filter (also known as a slant filter), whose frequency response is |ω| (where ω is the frequency). The filtered projection data can be denoted as p′(θ,r).

[0064] Step 102: Project the projection data back into the image space along the path of the X-ray to obtain the reconstructed image.

[0065] In the method described in this embodiment, considering the characteristics of the flat panel detector based on hexagonal pixels, a reconstruction algorithm based on filtered back-projection (FBP) can be selected, which involves projecting the projection data back along the path of the incident ray to the image space.

[0066] In the method described in this embodiment, during the back projection process, for each point (x, y) in the image, its reconstructed value f(x, y) is the sum of the projection values ​​of all rays passing through that point. As an optional method, the formula for obtaining the reconstructed image is:

[0067]

[0068] In the formula, f represents the reconstructed image, and f(x,y) represents the pixel value of the reconstructed image at point (x,y). p′ represents the filtered projection data. θ represents the projection angle, ranging from 0 to 2π. r represents the distance (radial distance) from the rotation center to the intersection of the X-ray and the detector. h(r-xcosθ-ysinθ) is the interpolation or filtering function in the back projection process, where r-xcosθ-ysinθ represents the distance from point (x,y) to the projection path.

[0069] In practical applications, h(r-xcosθ-ysinθ) is usually an impulse function (which may be a small weight or interpolation kernel in the discrete case) used to project the projection data to the correct position in the image space.

[0070] For the Ram-Lak filter, the Fourier transform of h(r) is |ω|. However, in practical calculations, filtering is usually performed directly in the spatial domain, so h(r) is the inverse Fourier transform of |ω|.

[0071] As an optional method, post-processing can be performed on the reconstructed image after it is obtained. This includes operations such as smoothing filtering, edge enhancement, and contrast adjustment to further improve image quality and visual effects. In the method described in this embodiment, these post-processing operations can be selected and applied according to actual needs to achieve the best image display effect. The number and specific content of post-processing operations are not limited here; any operation that meets the desired effect of the method described in this embodiment is acceptable.

[0072] The method described in this embodiment uses a hexagonal pixel array as its substrate. The hexagonal arrangement maximizes the photosensitive area, resulting in a high fill rate. This reduces gaps between pixels and improves image quality. Furthermore, filtering improves the signal-to-noise ratio of a single pixel in the flat panel detector, and combined with the FBP reconstruction algorithm, it achieves effective processing and optimization of the hexagonal pixel array, improving image clarity and accuracy. Simultaneously, the hexagonal pixels create a 60° angle in the frequency space, reducing grid artifacts and pixel inhomogeneities.

[0073] Based on the method for using a flat panel detector disclosed in the above embodiments, this embodiment correspondingly discloses an apparatus for using a flat panel detector. Referring to FIG3, the apparatus for using a flat panel detector includes: a scanning unit 201 and a reconstruction unit 202;

[0074] The scanning unit 201 is used to perform X-ray scanning on an object from multiple angles to acquire projection data; the projection data includes the projection angle and the distance between the X-ray and the center of rotation.

[0075] The reconstruction unit 202 is used to project the projection data back into the image space along the path of the X-ray to obtain a reconstructed image.

[0076] Optionally, the device further includes:

[0077] A filtering unit is used to filter the projection data.

[0078] Optionally, the formula for obtaining the reconstructed image is:

[0079]

[0080] In the formula, f is the reconstructed image, f(x,y) is the pixel value of the reconstructed image at point (x,y), p′ is the filtered projection data, θ is the projection angle, r is the distance from the rotation center to the intersection of the X-ray and the detector, and h(r-xcosθ-ysinθ) is the interpolation or filtering function in the back projection process.

[0081] Optionally, the device further includes:

[0082] A post-processing unit is used to perform post-processing on the reconstructed image; the post-processing includes one or more of smoothing filtering, edge enhancement, and contrast adjustment.

[0083] The embodiments in this specification are described in a progressive manner. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant details can be found in the method section.

[0084] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0085] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0086] The features described in the embodiments of this specification can be substituted for or combined with each other, so that those skilled in the art can implement or use this application.

[0087] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A flat panel detector, characterized in that, include: The substrate, electrodes, readout circuitry, and connecting lines connecting the electrodes and the readout circuitry; a pattern of hexagonal pixels is uniformly distributed on the substrate. The substrate is made of amorphous silicon; the electrodes are disposed on the top or bottom of each hexagonal pixel for collecting charge; the readout circuit is integrated and packaged with the substrate to obtain the amorphous silicon flat panel detector.

2. The flat panel detector according to claim 1, characterized in that, The readout circuit includes: a thin-film transistor array, an analog-to-digital converter, and a charge amplifier; the thin-film transistor array is used to control the charge input to the analog-to-digital converter; the analog-to-digital converter is used to convert the charge into a digital signal and send it to the charge amplifier; the charge amplifier is used to amplify the digital signal.

3. The flat panel detector according to claim 1 or 2, characterized in that, The flat panel detector further includes: a scintillator layer that converts rays into visible photons; the substrate is disposed below the scintillator layer; the substrate is used to collect the charge generated by the visible photon excitation.

4. The flat panel detector according to claim 3, characterized in that, The flat panel detector also includes a heat dissipation element for heat dissipation of the flat panel detector.

5. The flat panel detector according to claim 4, characterized in that, The flat panel detector also includes a support structure and / or a sealing device for protecting the flat panel detector.

6. A method using a flat panel detector, characterized in that, The method is applied to the flat panel detector according to any one of claims 1-5, and the method includes: performing X-ray scanning on the object from multiple angles to obtain projection data; the projection data includes the projection angle and the distance between the X-ray and the rotation center; and projecting the projection data back into the image space along the path of the X-ray to obtain a reconstructed image.

7. The method according to claim 6, characterized in that, After acquiring the projection data, the method further includes: filtering the projection data.

8. The method according to claim 7, characterized in that, The step of projecting the projection data back into the image space along the path of the X-ray to obtain the reconstructed image includes: the formula for obtaining the reconstructed image is: In the formula, f is the reconstructed image, f(x,y) is the pixel value of the reconstructed image at point (x,y), p′ is the filtered projection data, θ is the projection angle, r is the distance from the rotation center to the intersection of the X-ray and the detector, and h(r-xcosθ-ysinθ) is the interpolation or filtering function in the back projection process.

9. The method according to claim 6, characterized in that, After obtaining the reconstructed image, the method further includes: post-processing the reconstructed image; the post-processing includes one or more of smoothing filtering, edge enhancement, and contrast adjustment.

10. A device using a flat panel detector, characterized in that, include: The system includes a scanning unit and a reconstruction unit. The scanning unit is used to perform X-ray scanning on an object from multiple angles to acquire projection data. The projection data includes the projection angle and the distance between the X-ray and the center of rotation. The reconstruction unit is used to project the projection data back into the image space along the path of the X-ray to obtain a reconstructed image.

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