Device for correcting backscattering in an X-ray image

Abstract

An X-ray imaging detector (102) is proposed, wherein the X-ray imaging detector includes an X-ray converter (103) for converting X-ray radiation into charges. The X-ray imaging detector further includes a detector plate (104) for collecting the charges generated by the X-ray converter and for generating an image. In addition, the X-ray imaging detector includes a structured plate (105) for modulating the intensity of the backscattered X-ray radiation, wherein the structured plate is arranged on a side of the detector plate opposite to the X-ray converter side. In addition, the X-ray imaging detector includes a data processing system configured to mitigate image distortion caused by the backscattered X-ray radiation. In addition, the data processing system uses information about the structured plate.

Description

Technical Field

[0001] The present invention relates to an X-ray imaging detector and an X-ray imaging system. The X-ray imaging detector includes a structured plate for modulating the intensity of backscattered X-ray radiation and a data processing system for removing image distortion caused by the backscattered X-ray radiation. Background Art

[0002] X-ray imaging systems are used in a number of applications such as medical diagnostics, airport security, materials analysis, etc. For example, in a medical application, an X-ray tube and an X-ray imaging detector are arranged on opposite sides of a patient. The X-ray tube can generate a fan-shaped beam of X-rays. Photons of the X-ray beam are partially absorbed by the patient's body parts. Thus, bones absorb more photons compared to lean tissue. The photons that pass through the patient's body are then received by the X-ray imaging detector, which generates a shadow image of the patient's anatomical structure. The resulting image is a two-dimensional projection of the three-dimensional structure of the patient's body.

[0003] An X-ray imaging detector can include an X-ray converter and a detector plate. The X-ray converter converts X-ray radiation into charge. This conversion can be direct or indirect. For example, amorphous selenium can be used to directly convert X-ray radiation into charge. Alternatively, an indirect detector can include a scintillator to convert X-ray radiation into visible light, which can then be converted into charge by means of a photodiode. The charge generated by the X-ray converter can be collected by the detector plate. In addition, the detector plate can include an array, such as a uniform rectangular array of thin film transistors (TFTs). For example, each TFT can be connected to a photodiode for collecting the charge generated by that photodiode. The detector plate can also include readout electronics for reading out the charge. These readout electronics can also be configured to convert the charge into pixel values, where each pixel value is a single number representing the charge collected at the corresponding TFT. As a result, the detector plate can generate a digital image including pixel values.

[0004] The X-ray converter and the detector plate can absorb approximately 75% of the impinging X-ray radiation. The remaining 25% of the impinging X-ray photons can pass through the X-ray converter and the detector plate. To absorb such X-ray photons, conventional X-ray imaging detectors include a protective layer, which is a uniform layer of a radiation-impermeable material such as lead.

[0005] US2002 / 0011572 A1 discloses a radiation image pickup device that includes an image pickup element for converting radiation into an electrical signal and picking up an image of an object. Summary of the Invention

[0006] The protective layer of a conventional X-ray imaging detector can have a significant weight. The weight of the X-ray imaging detector may be less of a concern for an X-ray imaging detector stored in a Bucky tray, but especially for a portable X-ray imaging detector, reducing the weight can be beneficial. Thus, it can be desirable to provide an improved X-ray imaging detector with a lower weight.

[0007] This is achieved by an embodiment according to one aspect of the present invention, and additional preferred embodiments are also described. It should be noted that any feature, element, and / or function of the X-ray imaging detector described below is equally applicable to the X-ray imaging system described below, and vice versa. By replacing the protective layer with a structured plate, the weight of the imaging detector is significantly reduced.

[0008] According to the present invention, an X-ray imaging detector is provided. The X-ray imaging detector includes: an X-ray converter for converting X-ray radiation into charge; a detector plate for collecting the charge generated by the X-ray converter and for generating an image; a data processing system for processing the image generated by the detector plate; and a structured plate for modulating the intensity of backscattered X-ray radiation, wherein the X-ray converter, the detector plate, and the structured plate are arranged in this order. That is, the structured plate is arranged on the side of the detector plate opposite to the X-ray converter side, in other words, the detector plate is sandwiched between the structured plate and the X-ray converter. In addition, the data processing system is configured to use information about the structured plate to remove image distortion caused by the backscattered X-ray radiation.

[0009] An X-ray tube can emit an X-ray beam. The X-ray photons can at least partially propagate through the object to be analyzed. After propagating through the object, the X-ray photons can impinge on the X-ray converter of the X-ray imaging detector. The X-ray converter can be a direct converter, which can include, for example, amorphous selenium for directly converting X-ray radiation into charge. Alternatively, the X-ray converter can be an indirect converter, which can include a scintillator and a photodiode array. The X-ray converter can at least partially convert the impinging X-ray radiation into charge. For example, the X-ray converter can include a uniform rectangular array of X-ray conversion elements, each X-ray conversion element being configured to at least partially convert the impinging X-ray radiation into charge. The charge generated by the X-ray converter is collected by the detector plate, which can include, for example, a uniform rectangular array of detector elements. In addition, each detector element can include a switch such as a TFT. In particular, each detector element can collect the charge of one X-ray conversion element. The detector plate can also include readout electronics for reading out the charge collected by the detector elements. The readout electronics can also be configured to convert the charge into image pixel values. Thus, the detector plate can be configured to generate a digital image representing the amount of X-ray radiation impinging on the X-ray imaging detector.

[0010] However, a significant portion of the impinging X-ray radiation can propagate through the X-ray converter and the detector plate. This X-ray radiation can impinge on a structured plate. As defined in one aspect of the present invention, the X-ray converter, the detector plate, and the structured plate are arranged in this order, or in other words, the structured plate is arranged on the side of the detector plate opposite to the X-ray converter side. Thus, the structured plate is arranged behind the detector plate. The X-ray converter, the detector plate, and the structured plate are preferably pairwise parallel to each other. Herein, the direction orthogonal to the structured plate is referred to as the imaging direction. In addition, the region "in front of the X-ray converter" is to be understood as the region on the side of the X-ray converter opposite to the detector plate. In addition, the region "behind the structured plate" is the region on the side of the structured plate opposite to the detector plate.

[0011] The structured plate is configured to modulate the intensity of X-ray radiation. In other words, the structured plate can filter the X-ray radiation, wherein different regions of the structured plate provide different degrees of X-ray radiation attenuation. For example, in some regions of the structured plate, the attenuation of X-ray radiation can be negligible, while in other regions of the structured plate the attenuation can be significant. However, even the strongest attenuation of X-ray radiation provided by the structured plate may be substantially weaker compared to the attenuation provided by a conventional X-ray protective layer. For example, a conventional X-ray protective layer can attenuate X-ray radiation by 90% or more, which means that at most 10% of the X-ray photons propagate through the conventional X-ray protective layer. In contrast, the strongest attenuation of X-ray radiation provided by the structured plate can be 50% or less. The structured plate can superimpose a spatial pattern onto the intensity of the X-ray radiation that propagates through the X-ray converter and the detector plate.

[0012] One or more objects can be located in the region behind the structured plate. These objects may scatter back X-ray radiation that propagates through the X-ray converter, the detector plate, and the structured plate. Some of these objects can be part of the X-ray imaging detector. For example, the data processing system of the X-ray imaging detector can be arranged in the region behind the structured plate. The X-ray imaging detector can include various other components, such as a power supply in the region behind the structured plate. Other objects in the environment surrounding the X-ray imaging detector can also scatter back X-ray radiation. For example, the X-ray imaging detector can be located on a tabletop, which can scatter back X-ray radiation.

[0013] The backscattered X-ray photons can propagate through the structured plate and the detector plate again. When hitting the X-ray converter, the backscattered X-ray photons can generate charge, which may cause image distortion in the image generated by the detector plate. Since the structured plate modulates the intensity of the backscattered X-ray radiation, it can introduce a pattern in the image distortion caused by the backscattered X-ray radiation. In other words, the image distortion caused by the backscattered X-ray radiation can have a structure that depends on the structured plate and can be used to mitigate or remove these image distortions.

[0014] Correspondingly, the X-ray imaging detector includes a data processing system configured to remove image distortion caused by backscattered X-ray radiation. Additionally, the data processing system uses information about the structured plate. For example, the data processing system may utilize a calibration image of the structured plate, i.e., an image of the structured plate that has been recorded in a calibration mode. In particular, the calibration image may have been recorded in the absence of another object to be analyzed by means of X-ray radiation. Additionally or alternatively, the data processing system may utilize other kinds of information about the structured plate, such as a theoretical model describing its structure. For example, the structured plate may include a uniform rectangular array of radiopaque portions embedded in a radiolucent material. In this case, information about the position and size of the radiopaque portions may be provided and used by the data processing system to remove image distortion caused by the backscattered X-ray radiation.

[0015] Methods for using information about a superimposed pattern to mitigate structured image distortion have been previously described, see for example EP 3490455A1.

[0016] In an example, the structured plate includes radiopaque portions and radiolucent portions.

[0017] To modulate the intensity of backscattered X-ray radiation, the structured plate may include radiopaque portions and radiolucent portions, where the radiopaque portions provide a stronger X-ray radiation attenuation than the radiolucent portions. The radiopaque portions may be separated by the radiolucent portions of the structured plate, or the radiopaque portions may be connected to each other. Similarly, the radiolucent portions may be separated by the radiopaque portions of the structured plate, or the radiolucent portions may be connected to each other.

[0018] The radiopaque portions may include a radiopaque material. The radiopaque material may be a chemical element of the fourth period or higher of the periodic table. Alternatively, the radiopaque material may be a compound or alloy including atoms of the fourth period or higher of the periodic table. In particular, the radiopaque portions may include lead, tungsten, molybdenum, or gold. Other radiopaque materials are possible.

[0019] The radiolucent portions may include a radiolucent material. The radiolucent material may be a chemical element with an atomic number less than 15. Alternatively, the radiolucent material may be a compound or alloy including atoms with an atomic number less than 15. In particular, the radiolucent portions may include air, carbon, aluminum, paper, or plastic. Other radiolucent materials are possible.

[0020] In another example, the radiopaque portion is configured to have a minimum extent in a direction parallel to the structured plate, the minimum extent being greater than the size of the gap between adjacent conversion elements of the X-ray converter.

[0021] In other words, for all directions parallel to the structured plate, the extent of the radiopaque portion is greater than the size of the gap between adjacent conversion elements of the X-ray converter. For the sake of brevity, the minimum extent of the radiopaque portion in a direction parallel to the structured plate is hereinafter referred to as the width of the radiopaque portion. Similarly, the minimum extent of the radiolucent portion in a direction parallel to the structured plate is hereinafter referred to as the width of the radiolucent portion.

[0022] By ensuring that the width of the radiopaque portion is greater than the size of the gap between adjacent conversion elements, it can be ensured that the radiopaque portion does not completely overlap with the region of the X-ray converter that is insensitive to X-ray radiation. Thus, it can be ensured that the radiopaque portion is at least partially visible in the image generated by the detector plate. In other words, it can be ensured that the structured plate causes a pattern in the image distortion caused by backscattered X-ray radiation. Information about this pattern or corresponding information about the structured plate can be used by the data processing system to remove the image distortion caused by backscattered X-ray radiation.

[0023] In another example, the minimum extent of the radiopaque and / or radiolucent portion in a direction parallel to the structured plate is at least 1 mm.

[0024] The structured plate is configured to superimpose a pattern on the backscattered X-ray radiation. The pattern can be rather coarse. In particular, the width of the radiopaque portion can be 1 mm or greater. The radiopaque portions can have a large width, especially when these portions provide strong attenuation of the X-ray radiation (such as 70%, 80% or more). Additionally or alternatively, when the spatial variation of the backscattered X-ray intensity is smooth, i.e., when the object behind the structured plate does not cause a sharp change in the backscattered X-ray intensity, the radiopaque portions can have a large width.

[0025] Similarly, the width of the radiolucent portion can be 1 mm or greater. In particular, when the spatial variation of the backscattered X-ray intensity is smooth, the radiolucent portion can have a large width.

[0026] In another example, the radiopaque portion of the structured plate comprises lead, and the extent of the radiopaque portion in a direction perpendicular to the structured plate is from 0.05 mm to 0.2 mm.

[0027] The extent of the radiopaque portion in a direction perpendicular to the structured plate can be configured to provide a certain attenuation of the backscattered X-ray radiation that propagates through the radiopaque portion. The extent of the radiopaque portion in a direction perpendicular to the structured plate is hereinafter simply referred to as the thickness of the radiopaque portion. This thickness is preferably configured to provide an attenuation of 20% to 70% of the backscattered X-ray radiation that propagates through the radiopaque portion. A stronger attenuation of the backscattered X-ray radiation is also possible.

[0028] The attenuation provided by the radiopaque portions depends on their thickness and the attenuation coefficient of the material of the radiopaque portions. Thus, the attenuation coefficient can account for absorption and scattering, including coherent scattering. The attenuation coefficient depends on the frequency of the X-ray radiation and the material. Accordingly, radiopaque portions of different thicknesses can be configured for different radiopaque materials and for different frequencies of X-ray radiation.

[0029] For example, for a frequency corresponding to a photon energy of 100 keV, the attenuation coefficient of lead is approximately μ = 6 / mm. Thus, a radiopaque portion made of lead with a thickness of d = 0.1 mm provides an attenuation of 1–exp(−μd) = 45%. More generally, the thickness of the radiopaque portion including lead can be from 0.05 mm to 0.2 mm.

[0030] The radiopaque portions of the structured plate can include materials other than lead. For example, the radiopaque portions can include tungsten, molybdenum, or gold. For such materials, radiopaque portions of different thicknesses can be configured.

[0031] From the above explanation, it follows that the width of the radiolucent portion can be greater than the thickness of the radiopaque portion. The values of the width of the radiolucent portion and the thickness of the radiopaque portion can vary significantly, but the width of the radiolucent portion can generally be in the range of values from 0.2 times the thickness of the radiopaque portion to 50 times the thickness of the radiopaque portion. For example, the width of the radiolucent portion can be 0.2, 0.4, 1, 2, 4, 10, 20, or 50 times the thickness of the radiopaque portion.

[0032] In another example, the extent of the radiopaque portion in a direction perpendicular to the structured plate is configured such that the X-ray radiation is attenuated by 50% or less when propagating through the radiopaque portion.

[0033] The object of the present invention is to reduce the weight of the X-ray imaging detector. The radiopaque portions of the structured plate may include a dense material, and thus these portions may contribute significantly to the weight of the structured plate. For this reason, the thickness of the structured plate, and in particular the thickness of the radiopaque portions, should preferably be small.

[0034] The structured plate is configured to modulate the intensity of the backscattered X-ray radiation. Thus, the structured plate is configured to superimpose a pattern onto the image distortion caused by the backscattered X-ray radiation. The data processing system may be configured to determine a first pixel of an image generated by the detector plate, wherein the first pixel corresponds to a radiopaque portion of the structured plate. In other words, the backscattered X-ray radiation that propagates through the radiopaque portion of the structured plate may contribute to the value of the first pixel. Similarly, the data processing system may be configured to determine a second pixel, wherein the second pixel corresponds to a radiolucent portion of the structured plate. Thus, the backscattered X-ray radiation that does not propagate through the radiopaque portion of the structured plate may contribute to the value of the second pixel. The data processing system may be configured to remove the image distortion in the first and second pixels caused by the backscattered X-ray radiation based on the values of the first and second pixels and based on information about the attenuation provided by the radiopaque portion of the structured plate.

[0035] The radiopaque portion may be configured to provide attenuation of the backscattered X-ray radiation such that the impact of such attenuation on the pixel value is much higher than the quantization error caused by the readout electronics. However, it may be sufficient when the radiopaque portion of the structured plate attenuates the backscattered X-ray radiation by 20%, 30%, 40%, 50%, 60% or 70%.

[0036] In another example, the weight of the structured plate is less than 200 g.

[0037] In another example, the radiopaque portion includes radiopaque spheres and / or ellipsoids embedded in a radiolucent material, or the radiolucent portion includes radiolucent spheres and / or ellipsoids embedded in a radiopaque material.

[0038] In other examples, the radiopaque spheres and / or ellipsoids may be arranged on the surface of the radiolucent layer. The radiopaque portion may also include other shapes, such as a cuboid. Similarly, the radiolucent spheres and / or ellipsoids may be arranged on the surface of the radiopaque layer, and / or the radiolucent portion may have a shape different from a sphere or an ellipsoid.

[0039] The material of the radiopaque portion can have a higher density than the material of the radiolucent portion. A structured plate including radiopaque spheres embedded in or disposed on a radiolucent layer can have a particularly low weight.

[0040] In another example, the radiopaque portion includes radiopaque cylinders and / or strips separated by the radiolucent portion, or the radiolucent portion includes radiolucent cylinders and / or strips separated by the radiopaque portion.

[0041] The radiopaque or radiolucent cylinders can be oriented orthogonally to the structured plate. Thus, the axis of the cylinders can be parallel to the imaging direction. The cylinders can partially or fully penetrate the structured plate.

[0042] The cross-section of the cylinders in a plane parallel to the structured plate can be circular or elliptical. Other cross-sections of the cylinders in a plane parallel to the structured plate are also possible. In some examples, the cylinders can be oblique cylinders.

[0043] Alternatively, the structured plate can include radiopaque or transmissive lines, which can be oriented parallel to the structured plate. The length of the strips can be equal to the corresponding dimension of the structured plate. Alternatively, the length of the strips can be a fraction of the corresponding dimension of the structured plate. For example, a plurality of radiopaque lines can be arranged along a line, with radiolucent portions therebetween. Similarly, a plurality of transmissive lines can be arranged along a line, with radiopaque portions therebetween.

[0044] In another example, the radiopaque or radiolucent portions are irregularly distributed and / or oriented.

[0045] The pattern superimposed by the structured plate on the image distortion caused by backscattered X-ray radiation should not be similar to the pattern of the object to be analyzed. In addition, the pattern superimposed by the structured plate on the image distortion caused by backscattered X-ray radiation should be dissimilar compared to the X-ray intensity pattern caused by backscattered objects in the region behind the structured plate. In addition, the pattern superimposed by the structured plate on the image distortion caused by backscattered X-ray radiation should be dissimilar compared to the X-ray intensity pattern caused by other objects, which can absorb backscattered X-ray radiation, and / or can be located in the region behind the structured plate. This can be achieved by irregularly distributing the radiopaque or radiolucent portions in the structured plate. For example, the radiopaque or radiolucent portions can be randomly distributed in the structured plate. Additionally or alternatively, the radiopaque or radiolucent material can be randomly oriented.

[0046] The random distribution of the radiopaque and radiolucent portions in the structured plate can also facilitate the time- and / or cost-effective manufacture of the structured plate.

[0047] In another example, the radiopaque or radiolucent portions form a regular stripe pattern or a regular grid.

[0048] For example, the structured plate can include a radiopaque layer to which parallel radiopaque lines are attached. The gaps between the radiopaque lines can be filled with a radiolucent material to form the radiolucent portions. The radiolucent material can be air or another gas. Alternatively, the radiolucent material can be aluminum, carbon, or another solid material. The radiopaque layer can be optional, i.e., the radiopaque and transmissive lines can be stacked to form the structured plate. Alternatively, the structured plate can include a radiolucent layer to which parallel transmissive lines are attached. The gaps between the transmissive lines can be filled with a radiopaque material to form the radiopaque portions.

[0049] Alternatively, the radiopaque or radiolucent portions can form a regular grid, such as a rectangular or hexagonal grid.

[0050] The stripes of the regular stripe pattern or the regular grid can be parallel to the rows or columns of the detector elements of the detector plate. Alternatively, the stripes of the regular stripe pattern or the regular grid can be angled with respect to the rows and columns of the detector elements of the detector plate.

[0051] In another example, the spatial frequency of the radiopaque portions is higher in a first region of the structured plate than in a second region of the structured plate.

[0052] For example, an image generated by the detector plate can have a first part that may generally be more relevant than a second part of the image. For example, the center of the image is often more relevant than the edges of the image. The first and second parts of the image generated by the detector plate can correspond to the first and second regions of the structured plate, respectively. In the first region of the structured plate, the spatial frequency of the radiopaque portions can be higher than in the second region of the structured plate. The higher spatial frequency of the radiopaque portions in the first region of the structured plate can allow for better contrast to be achieved in the corresponding first part of the image generated by the detector plate. At the same time, the higher spatial frequency of the radiopaque portions can result in a higher weight of the structured plate, since the radiopaque material of the radiopaque portions can have a higher density than the radiolucent material of the radiolucent portions. Thus, by configuring a lower spatial frequency of the radiopaque portions in the second region of the structured plate compared to the first region of the structured plate, the weight of the structured plate can be reduced.

[0053] In another example, the X-ray imaging detector further includes a component that causes backscattered X-ray radiation with a sharp intensity change in a first region of the structured plate.

[0054] In this case, compared to a second region of the structured plate, the structured plate may include a higher spatial frequency of radiopaque portions in the first region of the structured plate. The high spatial resolution of the radiopaque portions in the first region of the structured plate can allow for resolving the backscattered X-ray intensity variations caused by the backscattering component. Thus, an improved contrast in a corresponding first portion of the image generated by the detector plate can be achieved. At the same time, the higher spatial frequency of the radiopaque portions can result in a higher weight of the structured plate, since the material of the radiopaque portions can have a higher density than the material of the radiolucent portions. Therefore, by configuring the radiopaque portions with a lower spatial frequency in the second region of the structured plate compared to the first region of the structured plate, the weight of the structured plate can be reduced.

[0055] In another example, the data processing system is configured to utilize a calibration image of the structured plate for removing image distortion caused by backscattered X-ray radiation.

[0056] To capture the calibration image of the structured plate, the X-ray tube may be arranged in a region behind the structured plate, which means that the X-ray tube, the structured plate, the detector plate, and the X-ray converter may be arranged in this order. Alternatively, the calibration image of the structured plate may be recorded by arranging the X-ray tube, the structured plate, the X-ray converter, and the detector plate in this order.

[0057] According to the present invention, an X-ray imaging system is also proposed. The X-ray imaging system includes an X-ray tube and an X-ray imaging detector according to the present invention.

[0058] Furthermore, an object to be analyzed may be arranged between the X-ray tube and the X-ray imaging detector. The X-ray tube may be configured to emit an X-ray beam in the direction of the object. The X-ray beam can be partially attenuated by the object. The X-ray imaging detector may be configured to generate an image representing the intensity of the X-ray radiation after passing through the object. The structured plate and the data processing system of the X-ray imaging detector are configured to remove image distortion caused by backscattered X-ray radiation from the image generated by the X-ray imaging detector. The X-ray imaging system may further include a control unit for synchronizing the operations of the X-ray tube and the X-ray imaging detector, and / or for controlling imaging parameters such as tube voltage, tube current, integration period, etc.

[0059] It should be understood that the X-ray imaging detector and the X-ray imaging system as defined in one aspect of the present invention have similar and / or identical preferred embodiments, especially as defined in the preferred embodiments. It should also be understood that the preferred embodiments of the present invention may also be any combination of various embodiments.

[0060] These and other aspects of the present invention will be apparent from the embodiments described hereinafter and will be elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Exemplary embodiments of the present invention will be described hereinafter with reference to the drawings:

[0062] Figure 1 An embodiment of an X-ray imaging system is schematically and exemplarily shown.

[0063] Figures 2a to 2e An embodiment of a structured plate of an X-ray imaging detector is schematically and exemplarily shown. DETAILED DESCRIPTION OF THE INVENTION

[0064] Figure 1 An embodiment of an X-ray imaging system 100 is schematically and exemplarily shown. The X-ray imaging system includes an X-ray tube 101 and an X-ray imaging detector 102. The X-ray tube may be configured to emit an X-ray beam towards the X-ray imaging detector. In Figure 1 which, the shape of the X-ray beam is illustrated by the outermost X-rays 106a and 106b. An object to be analyzed may be placed in the region between the X-ray tube and the X-ray imaging detector (not shown in Figure 1 ).

[0065] The X-ray imaging detector includes an X-ray converter 103 for converting X-ray radiation into charge and a detector plate 104 for collecting the charge generated by the X-ray converter and for generating an image.

[0066] The X-ray converter may be a direct or indirect converter. For example, the X-ray converter may include amorphous selenium for directly converting X-ray radiation into charge. Alternatively, the X-ray converter may include a scintillator for converting X-ray radiation into light and an array of photodiodes for converting the light into charge. The X-ray converter may include an array of conversion elements, each conversion element being configured to convert X-ray radiation into charge.

[0067] The detector board 104 may include an array of corresponding detector elements for collecting charges generated by the conversion elements of the X-ray converter. In addition, each detector element may include a TFT. The detector board may also include readout electronics for reading out the image, where each pixel of the image may correspond to the charge generated by one conversion element of the X-ray converter. Thus, the detector board may be configured to generate a digital image visualizing the amount of X-ray radiation impinging on the X-ray converter.

[0068] The X-ray converter may attenuate the impinging X-ray radiation by approximately 75%. The remaining approximate 25% of the X-ray radiation may propagate through the X-ray converter and the detector board. This X-ray radiation may impinge on the structured board 105, which is arranged behind the detector board when viewed from the X-ray converter. The structured board may be configured to modulate the intensity of the X-ray radiation. In addition, the structured board may include radiopaque and radiolucent portions.

[0069] In the region behind the structured board (when viewed from the detector board), one or more objects may be located, which may scatter back the X-ray radiation that propagates through the X-ray converter, the detector board, and the structured board or laterally through the X-ray converter, the detector board, and the structured board. For example, the X-ray imaging detector may include one or more objects 107a, 107b, and 107c, which may scatter back the X-ray radiation. Such objects may be components of the data processing system of the X-ray imaging detector or the power supply. Figure 1 The X-ray 109a is illustrated, which propagates from the X-ray tube through the X-ray converter, the detector board, and the structured board. The object 107b scatters the X-ray 109a back towards the X-ray converter. When impinging on the X-ray converter, the backscattered X-ray 109a may be converted into charges, which results in a distortion of the image generated by the detector board 104. In addition, Figure 1 Several objects 108a, 108b, and 108c of the environment of the X-ray imaging system are illustrated. Such objects are also capable of causing backscattering of the X-ray radiation. For example, Figure 1 The X-ray 109b is illustrated, which propagates through the X-ray converter, the detector board, and the structured board. The object 108c scatters the X-ray 109b back towards the X-ray converter, where charges can be generated, which results in a distortion of the image.

[0070] The structured plate modulates the intensity of backscattered X-ray radiation. The image distortion caused by the backscattered X-ray radiation thus has a superimposed pattern that corresponds to the structure and composition of the structured plate. The data processing system of the X-ray imaging detector can be configured to mitigate the distortion caused by the backscattered X-ray radiation. Additionally, the data processing system can utilize information about the structured plate. For example, the data processing system can utilize a calibration image of the structured plate. Additionally or alternatively, the data processing system can use a theoretical model of the structured plate. The theoretical model can include information about the position and size of the radiopaque portions of the structured plate. Additionally, the theoretical model can include information about the attenuation provided by the radiopaque portions.

[0071] The pattern superimposed by the structured plate onto the image distortion caused by the backscattered X-ray radiation should not be similar to the pattern of the object to be analyzed. Additionally, the pattern superimposed by the structured plate onto the image distortion caused by the backscattered X-ray radiation should be dissimilar compared to the X-ray intensity patterns caused by the backscattered objects 107a to 107c and 108a to 108c. Additionally, an object such as 108b or 108c can be absorbing the X-ray radiation scattered back by the object 108a, thereby causing an X-ray intensity pattern of the backscattered X-ray radiation. The pattern superimposed by the structured plate onto the image distortion caused by the backscattered X-ray radiation should also be dissimilar compared to the X-ray intensity pattern caused by a backscattered X-ray radiation absorbing object such as 108b or 108c. This can be achieved by irregularly distributing the radiopaque or radiolucent portions in the structured plate. For example, the radiopaque or radiolucent portions can be randomly distributed in the structured plate. Additionally or alternatively, the radiopaque or radiolucent portions can be randomly oriented.

[0072] Figures 2a to 2e An embodiment of a structured plate for an X-ray imaging detector is schematically and exemplarily depicted. Figures 2a to 2e The structured plate is shown from a viewing direction orthogonal to the structured plate.

[0073] For example, Figure 2a a structured plate 210 including radiopaque portions 211 and radiolucent portions 212 is depicted. The radiopaque portions are arranged according to a uniform rectangular array. In Figure 2a it, the radiopaque portions can be radiopaque spheres embedded in a radiolucent material. Alternatively, the radiopaque spheres can be arranged on the surface of a radiolucent layer. It is also possible that the radiopaque portions are radiopaque cylinders that partially or fully penetrate the structured plate. Thus, the axis of the radiopaque cylinder is orthogonal to the structured plate. Since Figure 2a represents a two-dimensional visualization of a three-dimensional structured plate, those skilled in the art can envision several other variations of the shape of the radiopaque portions.

[0074] Figure 2b depicts a similarly structured plate 220 having a radiopaque portion 221 and a radiolucent portion 222. However, the radiopaque portions are arranged in Figure 2b a uniform hexagonal array geometry.

[0075] Figure 2c depicts another structured plate 230 having a radiopaque portion 231 and a radiolucent portion 232. However, the radiopaque portion 231 is randomly distributed in Figure 2c it.

[0076] Figure 2d shows another structured plate 240 having a radiopaque portion 241 and a radiolucent portion 242. In Figure 2d it, the radiopaque portions are radiopaque lines having a length shorter than the corresponding dimension of the structured plate. The lines are arranged in Figure 2d a uniform hexagonal array.

[0077] Figure 2e depicts another structured plate 250 having a radiopaque portion 251 and a radiolucent portion 252. Figure 2e The structured plate of

[0078] Figures 2a to 2e has been described as having radiopaque portions 211, 221, 231, 241, and 251 and radiolucent portions 212, 222, 232, 242, and 252. A reverse configuration having radiopaque portions 212, 222, 232, 242, and 252 and radiolucent portions 211, 221, 231, 241, and 251 is also possible.

[0079] Although the invention has been illustrated and described in detail in the drawings and the foregoing description, these illustrations and descriptions are to be considered illustrative or exemplary and not restrictive. In particular, the illustrated forms and shapes of the structured plates are merely exemplary. The invention is not limited to the disclosed embodiments. By studying the drawings, the disclosure, and the claims, those skilled in the art will be able to understand and implement other variations of the disclosed embodiments when practicing the claimed invention.

[0080] In the claims, the word "comprising" does not exclude other elements or steps, and the words "a" or "an" do not exclude a plurality. A single processor or other unit may perform the functions of several items recited in the claims. Although specific measures are recited in mutually different dependent claims, this does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. An X-ray imaging detector, comprising: an X-ray converter for converting X-ray radiation into charge, a detector plate for collecting the charge generated by the X-ray converter and for generating an image, a data processing system for processing the image generated by the detector plate, and a structured plate for modulating the intensity of backscattered X-ray radiation, wherein the structured plate is arranged on a side of the detector plate opposite to the X-ray converter side, and wherein the data processing system is configured to use information about the structured plate to remove image distortion caused by the backscattered X-ray radiation.

2. The X-ray imaging detector according to claim 1, wherein, the structured plate includes a radiopaque portion and a radiolucent portion.

3. The X-ray imaging detector according to claim 2, wherein, the radiopaque portion is configured to have a minimum extent in a direction parallel to the structured plate, and the minimum extent is greater than the size of the gap between adjacent conversion elements of the X-ray converter.

4. The X-ray imaging detector according to claim 3, wherein, the minimum extent of the radiopaque portion in the direction parallel to the structured plate is at least 1 mm.

5. The X-ray imaging detector according to any one of claims 2 to 4, wherein, the radiopaque portion of the structured plate includes lead, and wherein the extent of the radiopaque portion in a direction perpendicular to the structured plate is from 0.05 mm to 0.2 mm.

6. The X-ray imaging detector according to any one of claims 2 to 4, wherein, the extent of the radiopaque portion in a direction perpendicular to the structured plate is configured such that X-ray radiation is attenuated by 50% or less when propagating through the radiopaque portion.

7. The X-ray imaging detector according to any one of claims 1 to 4, wherein, the structured plate weighs less than 200 g.

8. The X-ray imaging detector according to any one of claims 2 to 4, wherein, the radiopaque portion includes radiopaque spheres and / or ellipsoids embedded in a radiolucent material, or wherein the radiolucent portion includes radiolucent spheres and / or ellipsoids embedded in a radiopaque material.

9. The X-ray imaging detector according to any one of claims 2 to 4, wherein, the radiopaque portion includes radiopaque cylinders and / or strips separated by the radiolucent portion, or wherein the radiolucent portion includes radiolucent cylinders and / or strips separated by the radiopaque portion.

10. The X-ray imaging detector according to any one of claims 2 to 4, wherein, the radiopaque portion or the radiolucent portion is irregularly distributed and / or oriented.

11. The X-ray imaging detector according to any one of claims 2 to 4, wherein, the radiopaque portion or the radiolucent portion forms a regular stripe pattern or a regular grid.

12. The X-ray imaging detector according to any one of claims 2 to 4, wherein, the radiation-permeable portion comprises air, carbon, aluminum or plastic.

13. The X-ray imaging detector according to any one of claims 2 to 4, wherein, the X-ray imaging detector further comprises components that cause backscattered X-ray radiation with a sharp intensity change in a first region of the structured plate, and / or wherein the spatial frequency of the radiation-impermeable portion or the radiation-permeable portion is higher in the first region of the structured plate than in a second region of the structured plate.

14. The X-ray imaging detector according to any one of claims 1 to 4, wherein, the data processing system is configured to use a calibration image of the structured plate to remove the image distortion caused by the backscattered X-ray radiation.

15. An X-ray imaging system comprising an X-ray tube and an X-ray imaging detector according to any one of claims 1-14.

Images