Dual-layer flat panel detector and dual-layer flat panel detector-based x-ray imaging method

Abstract

The present invention provides a dual-layer flat panel detector and a dual-layer flat panel detector-based X-ray imaging method. The dual-layer flat panel detector comprises an upper detector unit and a lower detector unit; the upper detector unit is configured to receive X-rays, and, on the basis of absorbed X-rays, generate a first image electrical signal and transmit unabsorbed X-rays as residual rays to the lower detector unit; and the lower detector unit is configured to receive the residual rays to generate a second image electrical signal, wherein the signal-to-noise ratio of the lower detector unit is greater than the signal-to-noise ratio of the upper detector unit. The present invention effectively solves the problem of poor signal-to-noise ratio of a high-energy image, and improves the performance of the high-energy image.

Description

Dual-layer flat panel detector and X-ray imaging method based on dual-layer flat panel detector Technical Field

[0001] This invention belongs to the field of detector technology, and relates to a dual-layer flat panel detector, and more particularly to a dual-layer flat panel detector and an X-ray imaging method based on the dual-layer flat panel detector. Background Technology

[0002] The dual-layer flat panel detector is an advanced X-ray imaging device widely used in medical imaging and industrial inspection due to its ability to acquire multi-energy level images in a single exposure. Its core principle is to separate X-ray signals of different energies using a stacked structure of two detectors. The upper detector absorbs low-energy X-rays and generates a low-energy image, capturing object details and soft tissue information. The lower detector receives the remaining high-energy X-rays that have penetrated the upper layer, generating a high-energy image used to identify high-density structures or thicker objects. The advantage of this structure is that it can acquire both low-energy and high-energy images in a single exposure, improving examination efficiency and avoiding motion artifacts caused by equipment or patient movement in traditional multiple imaging processes. This characteristic makes the dual-layer flat panel detector extremely valuable in medical fields (e.g., chest imaging, bone density analysis) and industrial inspection (e.g., non-destructive testing of welds, material resolution).

[0003] However, existing dual-layer planar detectors still have significant performance drawbacks: First, low signal-to-noise ratio (SNR) in high-energy images. The upper amorphous silicon detector is highly efficient at absorbing X-rays, especially low-energy X-rays. This efficient absorption significantly reduces the number of X-rays penetrating to the lower layer, resulting in a weaker X-ray signal received by the lower detector and the signal being masked by internal electronic noise. This leads to low quantum conversion efficiency (DQE) and poor SNR in high-energy images. Second, reduced resolution. Due to the higher noise and weaker received signal of the lower amorphous silicon detector, image details are easily blurred, making it difficult to accurately distinguish high-density materials. In medical imaging, this can lead to unclear lesion areas, affecting diagnostic accuracy. Third, increased image ghosting. To compensate for the insufficient SNR of the lower detector, one approach is to increase the thickness of the scintillator to improve signal strength. However, increasing the scintillator thickness leads to a longer scattering path of the light signal within the material and causes light interference between pixels, resulting in noticeable image ghosting, especially during rapid imaging switching, which affects overall image quality. Summary of the Invention

[0004] The purpose of this invention is to provide a dual-layer flat panel detector and an X-ray imaging method based on the dual-layer flat panel detector, in order to solve the technical problem of low image performance acquired by the dual-layer flat panel detector in the prior art.

[0005] In a first aspect, the present invention provides a dual-layer flat panel detector, comprising an upper detector unit, a lower detector unit, and a filter layer between the upper detector unit and the lower detector unit;

[0006] The upper detector unit is configured to receive X-rays, generate a first image electrical signal based on the absorbed X-rays, and transmit unabsorbed X-rays as residual rays through the filter layer to the lower detector unit.

[0007] The lower-level detector unit is configured to receive the remaining rays to generate a second image electrical signal;

[0008] The signal-to-noise ratio of the lower-layer detector unit is greater than that of the upper-layer detector unit.

[0009] In one embodiment of the present invention, the upper detector unit is an amorphous silicon detector, and the lower detector unit is a complementary metal-oxide-semiconductor detector.

[0010] In one embodiment of the present invention, the amorphous silicon detector includes a first scintillator and a thin-film transistor;

[0011] The first scintillator is used to receive X-rays to obtain absorbed X-rays and convert the absorbed X-rays into visible light as a first optical signal;

[0012] The thin-film transistor is used to convert the first optical signal into a first image electrical signal and transmit it to the peripheral circuit.

[0013] In one embodiment of the present invention, the complementary metal-oxide-semiconductor detector includes a second scintillator and a complementary metal-oxide-semiconductor photosensitive element;

[0014] The second scintillator is used to convert the received residual rays into visible light as a second optical signal;

[0015] The complementary metal-oxide-semiconductor photosensitive element is used to convert the second optical signal into a second image electrical signal and transmit it to the peripheral circuit.

[0016] In one embodiment of the present invention, a filter layer is further provided between the upper detector unit and the lower detector unit.

[0017] In one embodiment of the present invention, the filter layer is made of metal.

[0018] In one embodiment of the present invention, the material of the filter layer is air.

[0019] Secondly, the present invention provides an X-ray imaging method based on a dual-layer flat panel detector, comprising:

[0020] The upper detector unit receives X-rays, generates a first image electrical signal based on the absorbed X-rays, and transmits the unabsorbed X-rays as residual rays through the filter layer to the lower detector unit.

[0021] The remaining rays are received using the lower-level detector unit to generate a second image electrical signal;

[0022] A filter layer is provided between the upper detector unit and the lower detector unit; the signal-to-noise ratio of the lower detector unit is greater than that of the upper detector unit.

[0023] As described above, the dual-layer flat panel detector and the X-ray imaging method based on the dual-layer flat panel detector of the present invention have the following beneficial effects:

[0024] This invention combines two detector units with different signal-to-noise ratios (SNRs). A detector unit with a relatively high SNR serves as the lower layer, while a detector unit with a relatively low SNR serves as the upper layer. These two layers capture X-rays of different energies, obtaining a first image electrical signal corresponding to the low-energy image and a second image electrical signal corresponding to the high-energy image. This effectively solves the problem of poor SNR in high-energy images, improving their performance and better meeting clinical requirements. Furthermore, this invention includes a filter layer between the two detector units to filter out residual X-rays, further enhancing the image performance of high-energy images. Attached Figure Description

[0025] Figure 1 shows a schematic diagram of the structure of the dual-layer flat panel detector according to an embodiment of the present invention.

[0026] Figure 2 shows a schematic diagram of a specific embodiment of the dual-layer flat panel detector according to an embodiment of the present invention.

[0027] Figure 3 shows a schematic flowchart of the X-ray imaging method based on a dual-layer flat panel detector according to an embodiment of the present invention.

[0028] Component labeling explanation: 10 is the upper detector unit, 20 is the filter layer, 30 is the lower detector unit, 11 is the first scintillator, 12 is the thin film transistor, 31 is the second scintillator, and 32 is the complementary metal-oxide-semiconductor photosensitive element. Detailed Implementation

[0029] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0030] A detector is a device that receives physical signals from the outside world and converts them into processable electrical signals or data. It is widely used in scientific research, medical diagnosis, industrial inspection, and environmental monitoring. The basic function of a detector is to capture specific types of physical quantities, such as light, sound, electromagnetic waves, particle radiation, or mechanical vibrations, and convert these signals into electrical signals through specific sensing mechanisms for subsequent analysis and processing. Based on their working principles and application scenarios, detectors can be classified into various types, such as optical detectors, radiation detectors, gas detectors, and chemical detectors. In the field of X-ray imaging, the detector plays a particularly important role, serving as the core device connecting the X-ray source to the final image result. Taking an amorphous silicon detector as an example, it converts high-energy X-rays into visible light through a scintillator layer, then converts the light signal into an electrical signal through a photodiode array. This electrical signal is then read and digitized by a thin-film transistor array to ultimately generate an image. The performance of the detector directly affects the clarity, contrast, and resolution of the image; therefore, its core indicators include sensitivity, signal-to-noise ratio, resolution, and response time. High-performance detectors can achieve high-precision signal capture even under extremely low signal strength, while possessing rapid response capabilities to meet the needs of real-time monitoring and dynamic imaging. In addition, the materials, structure, and circuit design of the detector also significantly affect its performance.

[0031] Low-energy and high-energy rays are two types of radiation classified according to the energy of their photons, and are widely used in medical imaging, industrial inspection, and scientific research. Low-energy rays typically refer to rays with lower photon energies, generally in the range of tens of kiloelectron volts (keV), such as 20-50 keV. These rays have weaker penetrating power and are more easily absorbed by materials with lower density or atomic numbers (such as soft tissue or plastics). Because the absorption intensity is highly dependent on the material properties, low-energy rays can highlight details of soft tissues or thin materials in imaging, producing high-contrast images. Therefore, they are widely used in medical imaging to examine lesions in the lungs, breasts, or other soft tissues. In industrial inspection, low-energy rays are suitable for identifying minute cracks or defects in thin materials. Compared to low-energy rays, high-energy rays have higher photon energies, typically in the range of 70-120 keV or even higher, and their penetrating power is significantly enhanced. High-energy rays are better suited for penetrating thicker objects or denser materials, such as bone, metal, and thick armor. High-energy X-rays are primarily used in medical imaging to observe bones, detect metal implants, or assess the condition of high-density materials. In industrial inspection, they are used to analyze the internal structure of welded components or detect hidden defects in large-volume materials. The choice between low-energy and high-energy X-rays is usually determined by the imaging target and requirements. Low-energy X-rays are suitable for scenarios requiring detailed imaging and high contrast, while high-energy X-rays are better suited for applications with strong penetrating power. In dual-energy imaging technology, the combination of low-energy and high-energy X-rays further enhances material resolution through differential absorption. The compositional information of materials can be calculated from the absorption characteristics at different energies, thereby achieving more accurate detection and diagnosis.

[0032] The following will describe in detail the principle and implementation of the dual-layer flat panel detector and the X-ray imaging method based on the dual-layer flat panel detector in this embodiment, so that those skilled in the art can understand the dual-layer flat panel detector and the X-ray imaging method based on the dual-layer flat panel detector in this embodiment without creative effort.

[0033] To address the aforementioned technical problems in the prior art, embodiments of the present invention provide a dual-layer flat panel detector.

[0034] Figure 1 shows a schematic diagram of the structure of the dual-layer flat panel detector according to an embodiment of the present invention. Referring to Figure 1, the dual-layer flat panel detector of the present invention includes an upper detector unit 10, a lower detector unit 30, and a filter layer 20 between the upper detector unit 10 and the lower detector unit 30. This structural design aims to achieve layered processing of X-ray energy, thereby capturing low-energy and high-energy ray signals respectively, and finally generating image electrical signals of different energy levels.

[0035] The upper detector unit 10 is configured to receive X-rays and generate a first image electrical signal based on the absorbed X-rays, while transmitting unabsorbed X-rays as residual rays through a filter layer to the lower detector unit 30. The upper detector unit 10 has high absorption efficiency for low-energy X-rays, and its generated first image electrical signal typically contains rich low-energy image information for detail capture and soft tissue analysis, used to generate low-energy images. The filter layer 20 is located between the upper detector unit 10 and the lower detector unit 30. The filter layer 20 attenuates X-rays within a preset energy range to optimize the energy distribution of rays reaching the lower detector unit 30. In other words, the filter layer 20 filters and optimizes the residual rays and transmits the optimized residual rays to the lower detector unit 30. Therefore, the filter layer 20 optimizes the energy distribution of the residual rays, thereby increasing the proportion of high-energy rays transmitted to the lower detector unit 30. This design effectively reduces interference from scattered rays to the lower detector unit 30, improving the contrast and resolution of the high-energy image (corresponding to the second image electrical signal). Those skilled in the art can set an appropriate thickness of the filter layer according to the range of X-ray energy received; the greater the thickness, the higher the proportion of low-energy rays filtered. The lower detector unit 30 is configured to receive residual rays to generate a second image electrical signal; wherein the signal-to-noise ratio (SNR) of the lower detector unit 30 is greater than that of the upper detector unit 10. Compared to the upper detector unit 10, the lower detector unit 30 has a higher SNR and can generate higher-performance high-energy images at low doses. It should be noted that the above-mentioned generation of corresponding images (i.e., low-energy images) based on the first image electrical signal and the generation of corresponding images (i.e., high-energy images) based on the second image electrical signal are conventional methods in the art. The image electrical signal is transmitted to the peripheral circuit, and the corresponding image is obtained through processing and A / D conversion by the peripheral circuit. The key improvement of this embodiment lies in the structure of the dual-layer flat panel detector, where the upper and lower detector units independently image (i.e., generate different image electrical signals respectively). The structure of the dual-layer flat panel detector of this invention can improve the effect of extracting the first and second image electrical signals based on X-rays, thereby improving the image performance of the finally acquired images (low-energy and high-energy images).

[0036] The dual-layer flat panel detector of this invention, through the combination of an upper and lower detector unit and energy optimization of the filter layer, achieves layered acquisition and high-quality imaging of low-energy rays (corresponding to the first image electrical signal) and high-energy rays (corresponding to the second image electrical signal). The lower detector unit 30 has a better signal-to-noise ratio than the upper detector unit 10, further improving the system's performance in high-energy imaging, making this solution suitable for scenarios requiring high-resolution, multi-energy-level images, such as medical imaging and industrial inspection.

[0037] Optionally, the upper detector unit 10 is an amorphous silicon detector, and the lower detector unit 30 is a complementary metal-oxide-semiconductor (CMOS) detector. In this embodiment, the upper detector unit 10 is an amorphous silicon detector. Amorphous silicon detectors have a fast and sensitive response to X-rays, can efficiently capture X-ray signals and generate low-energy image electrical signals, and the manufacturing process of amorphous silicon detectors is mature and the cost is relatively low. The lower detector unit 30 is a complementary metal-oxide-semiconductor (CMOS) detector. Compared with amorphous silicon detectors, firstly, amorphous silicon detectors amplify the signal after transmission, resulting in the amplification of both signal and noise. At low doses, the signal can be overwhelmed by noise, resulting in a poor image signal-to-noise ratio. In contrast, CMOS detectors amplify the signal before transmission, resulting in less noise and a higher signal-to-noise ratio. Secondly, amorphous silicon detectors have relatively slow capacitor charging and discharging during data readout, causing image information from the previous frame to remain in the next frame, affecting image quality. CMOS detectors have a high frame rate and fast image readout, resulting in less image ghosting. Therefore, CMOS detectors have higher quantum conversion efficiency, effectively improving the signal-to-noise ratio of images generated from residual X-rays. Compared to amorphous silicon detectors, CMOS detectors still provide excellent resolution and image quality under low-light or low-energy X-ray conditions. In other words, CMOS detectors have the advantages of low noise and minimal image retention at low doses, making them ideal as lower-layer detector units for obtaining high-energy images with high signal-to-noise ratios and clearer detail resolution. This invention achieves efficient dual-energy imaging through a combination design of amorphous silicon and CMOS detectors, avoiding the low signal-to-noise ratio problem of high-energy images in existing dual-layer detector technologies. Amorphous silicon absorbs some X-rays to generate low-energy images, while the remaining X-rays are received by the CMOS detector, reducing artifacts caused by interference between upper and lower layer signals. Furthermore, it effectively reduces image retention caused by X-ray accumulation, thereby improving the quality of high-energy images.

[0038] Optionally, the amorphous silicon detector includes a first scintillator and a thin-film transistor (TFT). The first scintillator receives X-rays to obtain absorbed X-rays and converts the absorbed X-rays into visible light as a first optical signal. The TFT converts the first optical signal into a first image electrical signal and transmits it to the peripheral circuit. Figure 2 shows a schematic diagram of a specific embodiment of the dual-layer flat panel detector according to an embodiment of the present invention. Referring to Figure 2, the amorphous silicon detector includes a first scintillator 11 and a thin-film transistor 12, which can realize the conversion process from X-rays to visible light and then to the first image electrical signal. Specifically, the first scintillator 11 is a material that is in direct contact with X-rays. Its function is to absorb X-rays and convert them into visible light. This conversion is based on the photoelectric effect of the scintillator material, that is, after the energy of X-rays is absorbed by the scintillator, visible light photons are excited. The visible light is used as the first optical signal. The TFT is a key electronic component constituting the amorphous silicon detector. Its function is to convert the first optical signal into a first image electrical signal. The first image electrical signal is transmitted to the peripheral circuit. Through the peripheral circuit and A / D conversion, the corresponding digital image, i.e., a low-energy image, is obtained. This embodiment uses the first scintillator 11 and the thin-film transistor 12 to achieve the conversion from X-rays to electrical signals, thereby improving the sensitivity and response speed of the detector.

[0039] Optionally, the complementary metal-oxide-semiconductor (CMOS) detector includes a second scintillator and a CMOS photosensitive element. The second scintillator converts the received residual X-rays into visible light as a second optical signal. The CMOS photosensitive element converts the second optical signal into a second image electrical signal and transmits it to the peripheral circuit. Figure 2 shows a schematic diagram of a specific embodiment of the dual-layer flat panel detector according to an embodiment of the present invention. Referring to Figure 2, the CMOS detector includes a second scintillator 31 and a CMOS photosensitive element 32, which can realize the conversion process of residual X-rays into visible light and then into a second image electrical signal. Specifically, the second scintillator 31 absorbs the residual X-rays after passing through the upper detector unit and converts them into visible light to capture those X-rays that are not absorbed by the upper detector unit. The CMOS photosensitive element 32 converts the visible light signal generated by the second scintillator into an electrical signal. This conversion is based on the photoelectric effect, converting the optical signal into a corresponding current or voltage signal. The converted electrical signal (i.e., the second image electrical signal) is transmitted to the peripheral circuit via a complementary metal-oxide-semiconductor (CMOS) photosensitive element. Through the peripheral circuit and A / D conversion, the corresponding digital image, i.e., the high-energy image, is obtained. In this embodiment, the combination of a second scintillator and a CMOS photosensitive element can convert residual X-rays into the corresponding second image electrical signal.

[0040] Optionally, the filter layer is made of metal. In the dual-layer flat panel detector of this invention, the filter layer is a crucial component for achieving the separation of X-rays of different energies, and its material selection has a significant impact on the detector's performance. When the filter layer is made of metal, metal materials typically have high atomic numbers, enabling them to strongly absorb or scatter low-energy X-rays, forming a clear energy boundary between the upper and lower detector units. This ensures that the remaining X-rays passing through are predominantly of higher energy, thereby achieving effective separation of low-energy and high-energy rays. Further, the metal materials used in the filter layer include aluminum, copper, molybdenum, and tungsten. By using a metal material for the filter layer, the penetration capability of high-energy rays can be optimized, thereby reducing artifacts caused by excess low-energy rays and improving the contrast and resolution of high-energy images. Furthermore, the high thermal stability and mechanical strength of metal materials allow them to withstand the high-energy impact of X-rays, ensuring stable performance of the filter layer during long-term use.

[0041] Optionally, the filter layer is made of air. In a dual-layer flat-panel detector, the filter layer plays a crucial role in separating X-rays of different energies. As an extremely low-density medium, air has a weak absorption capacity for X-rays. Compared to a metal filter layer, the energy separation effect of an air filter layer is weaker. The low density of air means it has almost no obstruction effect on high-energy X-rays, ensuring that high-energy X-rays can pass smoothly through the filter layer to reach the lower detector layer, thereby achieving effective detection of high-energy rays.

[0042] The dual-layer flat-panel detector of this invention combines two detector units with different signal-to-noise ratios (SNRs). A detector unit with a relatively high SNR serves as the lower layer, and a detector unit with a relatively low SNR serves as the upper layer. These two layers capture X-rays of different energies, obtaining a first image electrical signal corresponding to the low-energy image and a second image electrical signal corresponding to the high-energy image. This effectively solves the problem of poor SNR in high-energy images, improving image performance and better meeting clinical requirements. Furthermore, this invention includes a filter layer between the two detector units to filter out residual X-rays, further enhancing the image performance of high-energy images.

[0043] To address the aforementioned technical problems in the prior art, this embodiment of the invention also provides an X-ray imaging method based on a dual-layer flat panel detector. This method is implemented using the dual-layer flat panel detector described above. Specifically, Figure 3 shows a flowchart of the X-ray imaging method based on a dual-layer flat panel detector according to this embodiment. Referring to Figure 3, the X-ray imaging method based on a dual-layer flat panel detector according to this embodiment includes the following steps:

[0044] Step S100: Receive X-rays using the upper detector unit, generate a first image electrical signal based on the absorbed X-rays, and transmit the unabsorbed X-rays as residual rays through the filter layer to the lower detector unit.

[0045] Step S200: Receive the remaining rays using the lower-level detector unit to generate a second image electrical signal;

[0046] A filter layer is provided between the upper and lower detector units; the signal-to-noise ratio of the lower detector unit is greater than that of the upper detector unit.

[0047] The scope of protection of the X-ray imaging method based on a dual-layer flat panel detector in this embodiment is not limited to the order of steps listed in this embodiment. Any solution achieved by adding, subtracting, or replacing steps in the prior art based on the principle of this invention is included within the scope of protection of this invention.

[0048] The X-ray imaging method based on a dual-layer flat panel detector in this invention utilizes upper and lower detector units to capture X-rays of different energies, obtaining a first image electrical signal corresponding to the low-energy image and a second image electrical signal corresponding to the high-energy image. This effectively solves the problem of poor signal-to-noise ratio in high-energy images, improving image performance and better meeting clinical requirements. Furthermore, the filter layer between the two detector units can perform filtering to further enhance the image performance of high-energy images.

[0049] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and changes in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of protection of this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A dual-layer flat panel detector, comprising an upper detector unit, a lower detector unit, and a filter layer between the upper detector unit and the lower detector unit; The upper detector unit is configured to receive X-rays, generate a first image electrical signal based on the absorbed X-rays, and transmit unabsorbed X-rays as residual rays through the filter layer to the lower detector unit. The lower-level detector unit is configured to receive the remaining rays to generate a second image electrical signal; in, The signal-to-noise ratio of the lower-layer detector unit is greater than that of the upper-layer detector unit.

2. The dual-layer flat panel detector according to claim 1, characterized in that, The upper detector unit is an amorphous silicon detector, and the lower detector unit is a complementary metal-oxide-semiconductor detector.

3. The dual-layer flat panel detector according to claim 2, characterized in that, The amorphous silicon detector includes a first scintillator and a thin-film transistor; The first scintillator is used to receive X-rays to obtain absorbed X-rays and convert the absorbed X-rays into visible light as a first optical signal; The thin-film transistor is used to convert the first optical signal into a first image electrical signal and transmit it to the peripheral circuit.

4. The dual-layer flat panel detector according to claim 2, characterized in that, The complementary metal-oxide-semiconductor detector includes a second scintillator and a complementary metal-oxide-semiconductor photosensitive element; The second scintillator is used to convert the received residual rays into visible light as a second optical signal; The complementary metal-oxide-semiconductor photosensitive element is used to convert the second optical signal into a second image electrical signal and transmit it to the peripheral circuit.

5. The dual-layer flat panel detector according to claim 1, characterized in that, The filter layer is made of metal.

6. The dual-layer flat panel detector according to claim 1, characterized in that, The filter layer is made of air.

7. An X-ray imaging method based on a dual-layer flat panel detector, comprising: The upper detector unit receives X-rays, generates a first image electrical signal based on the absorbed X-rays, and transmits the unabsorbed X-rays as residual rays through the filter layer to the lower detector unit. The remaining rays are received using the lower-level detector unit to generate a second image electrical signal; A filter layer is provided between the upper detector unit and the lower detector unit; the signal-to-noise ratio of the lower detector unit is greater than that of the upper detector unit.

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