Plate-shaped object limited angle CT image reconstruction method and device, equipment and medium

Abstract

The invention discloses a plate-shaped object limited angle CT image reconstruction method and device, equipment and a medium, and the method comprises the steps: obtaining multiple groups of projection data of a detected plate-shaped object, reconstructing a base material image based on the multiple groups of projection data of the detected plate-shaped object, and carrying out the limited angle artifact removal of the base material image through a limited angle imaging optimization model, the combination of energy spectrum CT reconstruction and a finite angle imaging optimization model is realized. In this way, the base material in the detected plate-shaped object can be separated, the gray information and gradient information of the visible boundary in the limited angle reconstruction image can be utilized to recover the internal structure submerged by the limited angle artifact, and the metal artifact and the limited angle artifact in the detected plate-shaped object reconstruction image can be removed at the same time. And the reconstruction effect of the plate-shaped object reconstruction image is improved.

Description

Technical Field

[0001] The present application relates to the technical field of X-ray CT imaging, and particularly relates to a method, device, equipment and medium for reconstructing limited-angle CT images of a plate-shaped object. Background Art

[0002] X-ray Computed Tomography (abbreviated as X-ray CT) has been widely used in the fields of medical treatment, industrial non-destructive testing, biological sample testing, security inspection, etc. A multi-energy spectrum CT imaging system uses X-rays at multiple different energy spectra to scan an object to be measured, and obtains projection data of the object to be measured at multiple different energy spectra. Using these projection data, the basis material image or pseudo mono-energetic image of the object to be measured can be reconstructed, so as to achieve the purposes of material separation, contrast enhancement, removal of metal artifacts, hardening artifacts, etc. However, when detecting objects to be measured in the shape of a flat plate such as a circuit board or a chip, due to limitations of the scanning environment or equipment, etc., only projection data within a limited angular range can be obtained, which will cause limited-angle artifacts related to the scanning direction to appear in the reconstructed basis material image or pseudo mono-energetic image, resulting in incorrect decomposition of the basis material image or pseudo mono-energetic image.

[0003] Therefore, the existing technology still needs to be improved. Summary of the Invention

[0004] The technical problem to be solved by the present application is to provide a method, device, equipment and medium for reconstructing limited-angle CT images of a plate-shaped object in view of the deficiencies of the existing technology.

[0005] To solve the above technical problem, the first aspect of the present application provides a method for reconstructing limited-angle CT images of a plate-shaped object, wherein the method for reconstructing limited-angle CT images of a plate-shaped object specifically includes:

[0006] Performing energy-spectrum limited-angle scanning on the plate-shaped object to be measured by using a CT system, and obtaining multiple groups of projection data of the plate-shaped object to be measured;

[0007] Assigning initial values to various basis material images of the plate-shaped object to be measured to obtain various estimated values of the basis material images;

[0008] Performing image reconstruction based on multiple groups of projection data and various estimated values of the basis material images to obtain various reconstructed image values of the basis material;

[0009] Removing limited-angle artifacts from various reconstructed basis material images based on a preset limited-angle imaging optimization model to obtain a reconstructed image of the plate-shaped object to be measured.

[0010] The method for reconstructing limited-angle CT images of a plate-shaped object, wherein the performing energy-spectrum limited-angle scanning on the plate-shaped object to be measured by using a CT system and obtaining projection data of the plate-shaped object to be measured at at least two energy spectra specifically includes:

[0011] The plate-shaped object is scanned with a limited-angle CT scanning mode at a given high X-ray tube voltage and a low X-ray tube voltage respectively to obtain projection data of a high energy spectrum and projection data of a low energy spectrum.

[0012] The method for reconstructing a limited-angle CT image of a plate-shaped object, wherein the image reconstruction is performed based on multiple sets of projection data and estimated values of various basis material images to obtain reconstructed image values of various basis materials, specifically including:

[0013] Using the inclined projection correction technique, image reconstruction is performed based on multiple sets of projection data and estimated values of various basis material images to obtain reconstructed image values of various basis materials.

[0014] The method for reconstructing a limited-angle CT image of a plate-shaped object, wherein the construction process of the limited-angle imaging optimization model is as follows:

[0015] Based on the directional partial derivative of the reconstructed image value for removing limited-angle artifacts to be calculated, a smoothness constraint term is constructed;

[0016] Based on the directional partial derivative of the reconstructed image of the basis material and the directional partial derivative of the reconstructed image value for removing limited-angle artifacts to be calculated, an approximation constraint term is constructed;

[0017] Integrate the smoothness constraint term and the approximation constraint term over the set of positions of non-boundary points on the reconstructed image of the basis material to obtain an objective function;

[0018] Construct a limited-angle imaging optimization model by minimizing the objective function.

[0019] The method for reconstructing a limited-angle CT image of a plate-shaped object, wherein the limited-angle imaging optimization model is:

[0020]

[0021] wherein, u represents the image optimized by the limited-angle imaging optimization model, Ω′ represents the set of positions of non-boundary points on the reconstructed image, v represents the reconstructed image value for removing limited-angle artifacts, φ represents the reconstructed image of the basis material, μ represents a preset constant coefficient, · x represents the directional partial derivative in the horizontal direction x of the image.

[0022] The method for reconstructing a limited-angle CT image of a plate-shaped object, wherein the analytical solution of the limited-angle imaging optimization model is:

[0023]

[0024] wherein, both a and b represent non-boundary points in the horizontal direction of the image, l(x) represents a regulation term, and x represents non-boundary points between a and b in the horizontal direction of the image.

[0025] The described method for reconstructing a limited-angle CT image of a plate-shaped object, wherein removing limited-angle artifacts from the reconstructed images of various base materials based on a preset limited-angle imaging optimization model to obtain the reconstructed image of the plate-shaped object to be measured specifically includes:

[0026] Removing limited-angle artifacts from the reconstructed images of various base materials based on a preset limited-angle imaging optimization model to obtain the reconstructed images of various base materials with limited-angle artifacts removed;

[0027] Detecting whether the reconstructed images of various base materials with limited-angle artifacts removed meet the preset requirements;

[0028] If the preset requirements are met, using the reconstructed images of various base materials with limited-angle artifacts removed as the reconstructed image of the plate-shaped object to be measured;

[0029] If the preset requirements are not met, using the reconstructed images of various base materials with limited-angle artifacts removed as the estimated values of various base material images, and re-executing the step of image reconstruction based on multiple sets of projection data and the estimated values of various base material images until the preset requirements are met to obtain the reconstructed image of the plate-shaped object to be measured.

[0030] The second aspect of the present application provides a device for reconstructing a limited-angle CT image of a plate-shaped object, wherein the device for reconstructing a limited-angle CT image of a plate-shaped object specifically includes:

[0031] An acquisition module, configured to perform an energy spectrum limited-angle scan on the plate-shaped object to be measured by using a CT system to acquire multiple sets of projection data of the plate-shaped object to be measured;

[0032] An assignment module, configured to assign initial values to the images of various base materials of the plate-shaped object to be measured to obtain the estimated values of various base material images;

[0033] A reconstruction module, configured to perform image reconstruction based on multiple sets of projection data and the estimated values of various base material images to obtain the reconstructed image values of various base materials;

[0034] An artifact removal module, configured to remove limited-angle artifacts from the reconstructed images of various base materials based on a preset limited-angle imaging optimization model to obtain the reconstructed image of the plate-shaped object to be measured.

[0035] The third aspect of the present application provides a computer-readable storage medium, where the computer-readable storage medium stores one or more programs, and the one or more programs can be executed by one or more processors to implement the steps in any of the above-described methods for reconstructing a limited-angle CT image of a plate-shaped object.

[0036] The fourth aspect of the present application provides a terminal device, which includes: a processor and a memory;

[0037] A computer-readable program executable by the processor is stored on the memory;

[0038] When the processor executes the computer-readable program, the steps in any of the above-described methods for reconstructing a limited-angle CT image of a plate-shaped object are implemented.

[0039] Beneficial effects: Compared with the prior art, the present application provides a method, device, equipment and medium for reconstructing a limited-angle CT image of a plate-shaped object. After obtaining multiple sets of projection data of the plate-shaped object to be measured, the method reconstructs a base material image based on the multiple sets of projection data of the plate-shaped object to be measured, and then uses a limited-angle imaging optimization model to remove limited-angle artifacts from the base material image, realizing the combination of energy spectrum CT reconstruction and the limited-angle imaging optimization model. In this way, not only can the base materials in the plate-shaped object to be measured be separated, but also the gray-scale information and gradient information of the visible boundaries in the limited-angle reconstructed image can be used to restore the internal structure submerged by the limited-angle artifacts, and at the same time, the metal artifacts and limited-angle artifacts in the reconstructed image of the plate-shaped object to be measured are removed, improving the reconstruction effect of the reconstructed image of the plate-shaped object. Description of the Drawings

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0041] Figure 1 It is a model example diagram of the plate-shaped object to be measured provided by the embodiment of the present application.

[0042] Figure 2 is Figure 1 A schematic diagram of the metal material part of the plate-shaped object to be measured shown.

[0043] Figure 3 is Figure 1 A schematic diagram of the non-metal material part of the plate-shaped object to be measured shown.

[0044] Figure 4 It is a schematic diagram of the metal material part obtained by directly reconstructing using projection data.

[0045] Figure 5 It is a schematic diagram of the non-metal material part obtained by directly reconstructing using projection data.

[0046] Figure 6 It is a flowchart of the method for reconstructing a limited-angle CT image of a plate-shaped object provided by the embodiment of the present application.

[0047] Figure 7Schematic diagram of a CT scanning system for performing limited-angle CT scanning on a plate-shaped object to obtain projection data of the measured plate-shaped object.

[0048] Figure 8 Schematic diagram of the metal material part obtained by reconstruction through the method provided by the embodiments of the present application.

[0049] Figure 9 Schematic diagram of the non-metal material part obtained by reconstruction through the method provided by the embodiments of the present application.

[0050] Figure 10 Schematic diagram of the reconstructed image of the measured plate-shaped object obtained by reconstruction through the method provided by the embodiments of the present application.

[0051] Figure 11 Principle block diagram of the plate-shaped object limited-angle CT image reconstruction device provided by the embodiments of the present application.

[0052] Figure 12 Principle block diagram of the terminal device provided by the embodiments of the present application. Specific embodiments

[0053] The embodiments of the present application provide a method, device, equipment and medium for reconstructing a plate-shaped object limited-angle CT image. To make the purpose, technical solution and effect of the present application clearer and more definite, the following further describes the present application in detail with reference to the accompanying drawings and by way of examples. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0054] Those skilled in the art of the present technology can understand that unless specifically stated otherwise, the singular forms "a", "an", "the" and "said" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the specification of the present application means the presence of the described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or their groups. It should be understood that when we say that an element is "connected" or "coupled" to another element, it can be directly connected or coupled to other elements, or there may also be intermediate elements. In addition, the "connection" or "coupling" used herein may include wireless connection or wireless coupling. The term "and / or" used herein includes all or any unit and all combinations of one or more related listed items.

[0055] Those skilled in the art can understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as the general understanding of those of ordinary skill in the art to which this application belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted in an idealized or overly formal sense unless specifically defined as here.

[0056] It should be understood that the sequence numbers and magnitudes of the steps in this embodiment do not imply the order of execution. The execution order of each process is determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of this application.

[0057] The following further illustrates the application content by describing the embodiments in conjunction with the accompanying drawings.

[0058] X-ray computed tomography technology (X ray Computed Tomography, abbreviated as X-ray CT) has been widely used in the fields of medical treatment, industrial non-destructive testing, biological sample testing, security inspection, etc. The multi-energy spectrum CT imaging system uses X-rays at multiple different energy spectra to scan the object to be measured, and obtains the projection data of the object to be measured at multiple different energy spectra. Using these projection data, the base material image or pseudo-monochromatic image of the object to be measured can be reconstructed, so as to achieve the purposes of material separation, contrast enhancement, removal of metal artifacts, hardening artifacts, etc. However, when detecting flat-shaped objects to be measured such as circuit boards and chips, due to limitations of the scanning environment or equipment, only projection data within a limited angular range can be obtained, which will cause limited-angle artifacts related to the scanning direction to appear in the reconstructed base material image or pseudo-monochromatic image, resulting in errors in the decomposition of the base material image or pseudo-monochromatic image.

[0059] For example, assume that the plate-shaped object as Figure 1 shown contains metal materials and non-metal materials. The metal material part is as Figure 2 shown, and the non-metal material part is as Figure 3 shown. The plate-shaped object is scanned at a limited angle of 120° with X-ray tube voltages of 140 KV and 80 KV to obtain two sets of projection data, and then the two sets of projection data are directly used for image reconstruction, and the reconstructed image of the metal material as Figure 4 shown and the reconstructed image of the non-metal material as Figure 5 shown will be obtained. It can be seen from the reconstructed images of these two base materials that obvious artifacts exist in the reconstructed images of the two base materials, which in turn affects the reconstruction effect of the plate-shaped object.

[0060] Based on this, an embodiment of the present application provides a method for reconstructing a limited-angle CT image of a plate-shaped object. After obtaining multiple sets of projection data of the plate-shaped object to be measured, a base material image is reconstructed based on the multiple sets of projection data of the plate-shaped object to be measured, and then a limited-angle imaging optimization model is used to remove limited-angle artifacts from the base material image, realizing the combination of energy spectrum CT reconstruction and the limited-angle imaging optimization model. In this way, not only can the base materials in the plate-shaped object to be measured be separated, but also the gray-scale information and gradient information of the visible boundaries in the limited-angle reconstructed image can be used to restore the internal structure submerged by limited-angle artifacts, while removing metal artifacts and limited-angle artifacts in the reconstructed image of the plate-shaped object to be measured, improving the reconstruction effect of the reconstructed image of the plate-shaped object.

[0061] An application environment of the method for reconstructing a limited-angle CT image of a plate-shaped object provided by an embodiment of the present application may include a multi-energy spectrum CT system and a host computer. The multi-energy spectrum CT system is connected to the host computer. The host computer may specifically be a desktop terminal, a mobile terminal, or a server, etc. The mobile terminal may specifically be at least one of a mobile phone, a tablet computer, a notebook computer, etc. The server may be implemented by an independent server or a server cluster composed of multiple servers. Among them, the multi-energy spectrum CT system is used to perform energy spectrum limited-angle scanning on the plate-shaped object to be measured to collect multiple sets of projection data of the plate-shaped object to be measured, and transmit the multiple sets of projection data to the host computer. The host computer is used to assign initial values to various base material images of the plate-shaped object to be measured to obtain various estimated values of the base material images; perform image reconstruction based on the multiple sets of projection data and various estimated values of the base material images to obtain various reconstructed image values of the base material; perform limited-angle artifact removal on various reconstructed images of the base material based on a preset limited-angle imaging optimization model to obtain a reconstructed image of the plate-shaped object to be measured. Of course, the host computer may also display the reconstructed image of the plate-shaped object to be measured, etc.

[0062] As Figure 6 shown, a method for reconstructing a limited-angle CT image of a plate-shaped object provided by this embodiment specifically includes:

[0063] S10. Use a CT system to perform energy spectrum limited-angle scanning on the plate-shaped object to be measured to obtain multiple sets of projection data of the plate-shaped object to be measured.

[0064] Specifically, the multiple sets of projection data may be obtained by scanning the plate-shaped object to be measured using two or more X-ray energy spectra; or only using one X-ray energy spectrum and using a sandwich detector or a photon counting detector. In one implementation, the multiple sets of projection data are two sets of projection data, and the two sets of projection data are obtained by scanning the plate-shaped object to be measured using two X-ray energy spectra. Correspondingly, using a CT system to perform energy spectrum limited-angle scanning on the plate-shaped object to be measured to obtain multiple sets of projection data of the plate-shaped object to be measured may specifically be:

[0065] The plate - like object to be measured is scanned respectively with a given high X - ray tube voltage and a given low X - ray tube voltage in a limited - angle CT scanning mode to obtain projection data of a high - energy spectrum and projection data of a low - energy spectrum.

[0066] Specifically, as Figure 7 shown, the CT system is configured in a limited - angle CT scanning mode. Point O is the rotation center of the plate - like object to be measured, the arrow is the rotation direction of the plate - like object to be measured, α is the limited angle. When the ray source and the detector are turned on, the ray source emits X - rays onto the plate - like object to be measured, and the plate - like object to be measured rotates around point O by a limited angle α. The detector obtains the X - ray projection data corresponding to the limited angle α of the plate - like object to be measured to obtain the projection data of the plate - like object to be measured. Among them, the projection data of the high - energy spectrum is obtained by scanning according to the above - mentioned scanning process under the given high X - ray tube voltage, and the projection data of the low - energy spectrum is obtained by scanning according to the above - mentioned scanning process under the given low X - ray tube voltage. In addition, the limited angle α is pre - set, and it can be determined according to the plate - like object to be measured. There is no specific limitation here, and only a specific example is given. The range of the limited angle α can be

[0067] It should be noted that here only two sets of projection data are taken as examples to illustrate the acquisition process of the projection data, and the number of projection data is not limited. In practical applications, there can also be multiple sets of projection data, such as 3 sets, 4 sets, etc. And when obtaining multiple sets of projection data, only the X - ray tube voltage is different, and the rest of the scanning environments are the same.

[0068] S20. Assign initial values to the images of various base materials of the plate - like object to be measured to obtain estimated values of the images of various base materials;

[0069] Specifically, the plate - like object to be measured can include several base materials, such as metal materials, non - metal materials, etc. The initial values are used as the initial values of each pixel in the images of various base materials of the plate - like object to be measured. The initial values can be pre - set. For example, if the initial value is 0, then the estimated values of the images of various base materials are all 0. In addition, the images of various base materials can be assigned the same initial value, or different initial values can be assigned to some or all of the images of the base materials according to the actual situation.

[0070] S30. Perform image reconstruction based on multiple sets of projection data and the estimated values of the images of various base materials to obtain the reconstructed image values of various base materials.

[0071] Specifically, image reconstruction is used to reconstruct various estimated basis material image values based on multiple sets of projection data to obtain various reconstructed basis material image values. Among them, methods such as the tilted projection correction technique, E-ART (Extended Algebraic Reconstruction Method), and IFBP (Iterative Filtered Back-projection) can be used for image reconstruction. In a specific implementation, the tilted projection correction technique is used for image reconstruction. Correspondingly, the process of reconstructing an image based on multiple sets of projection data and various estimated basis material image values to obtain various reconstructed basis material image values is specifically to use the tilted projection correction technique to reconstruct an image based on multiple sets of projection data and various estimated basis material image values to obtain various reconstructed basis material image values. Among them, the process of using the tilted projection correction technique for reconstruction can first determine the projection error between the estimated basis material image value and multiple sets of projection data, and determine the projection residual of the basis material based on the projection error. Then, the projection residual of the basis material is back-projected to obtain the image residual of the basis material. Finally, image reconstruction is performed based on the image residual to obtain the reconstructed basis material image value, which can effectively remove metal artifacts in the measured plate-like object and obtain the reconstructed basis material image value with metal artifacts removed.

[0072] S40. Remove finite-angle artifacts from various reconstructed basis material images based on a preset finite-angle imaging optimization model to obtain a reconstructed image of the measured plate-like object.

[0073] Specifically, the finite-angle imaging optimization model is pre-constructed for removing finite-angle artifacts. That is, after obtaining various reconstructed basis material image values, the various reconstructed basis material image values can be output to the finite-angle imaging optimization model, and finite-angle artifacts are removed through the finite-angle imaging optimization model to obtain a reconstructed image of the measured plate-like object. Among them, the reconstructed image of the measured plate-like object is synthesized based on various reconstructed basis material images with finite-angle artifacts removed. For example, through the finite-angle imaging optimization model, finite-angle artifacts are removed to obtain a reconstructed metal material image with finite-angle artifacts removed as shown in Figure 8 and a reconstructed non-metal material image with finite-angle artifacts removed as shown in Figure 9 . Then, by combining the reconstructed metal material image with finite-angle artifacts removed and the reconstructed non-metal material image with finite-angle artifacts removed, a reconstructed image of the measured plate-like object as shown in Figure 10 can be synthesized.

[0074] In one implementation, the construction process of the finite-angle imaging optimization model specifically includes:

[0075] Construct a smoothness constraint term based on the directional partial derivative of the reconstructed image value for removing finite - angle artifacts to be calculated;

[0076] Construct an approximation constraint term based on the directional partial derivative of the reconstructed image of the base material and the directional partial derivative of the reconstructed image value for removing finite - angle artifacts to be calculated;

[0077] Integrate the smoothness constraint term and the approximation constraint term over the set of positions of non - boundary points on the reconstructed image of the base material to obtain an objective function;

[0078] Construct a finite - angle imaging optimization model by minimizing the objective function.

[0079] Specifically, the finite - angle imaging optimization model includes a smoothness constraint term and an approximation constraint term. The smoothness constraint term is used to constrain the smoothness of the reconstructed image value for removing finite - angle artifacts to minimize the magnitude of the directional partial derivative, prompting the solution to tend to be smooth. The approximation constraint term is used to make the directional partial derivative of the reconstructed image value for removing finite - angle artifacts approach the directional partial derivative of the reconstructed image value of the base material, so that the solution can conform to the gray - scale and gradient values of the visible boundaries in the reconstructed image of the base material, and thus the internal structure of the measured plate - like object can be reconstructed using the gray - scale and gradient values of the visible boundaries in the reconstructed image of the base material.

[0080] In one implementation, the finite - angle imaging optimization model is:

[0081]

[0082] where \(u\) represents the image optimized by the finite - angle imaging optimization model, \(\Omega'\) represents the set of positions of non - boundary points on the reconstructed image, \(v\) represents the reconstructed image value for removing finite - angle artifacts, \(\varphi\) represents the reconstructed image of the base material, \(\mu\) represents a preset constant coefficient, and \(\cdot\) x represents the directional partial derivative in the horizontal direction \(x\) of the image.

[0083] It should be noted that the above - mentioned finite - angle imaging optimization model is only a specific implementation given in the embodiments of the present application. In actual applications, as long as the finite - angle imaging optimization model that can remove finite - angle artifacts constructed by using the construction method in the embodiments of the present application is within the protection scope of the embodiments of the present application. For example, by simply changing the expression form of the smoothness constraint term and / or the approximation constraint term in the finite - angle imaging optimization model to change the expression form of the finite - angle imaging optimization model.

[0084] Furthermore, when determining the reconstructed image of the measured plate - like object through the finite - angle imaging optimization model, the analytical solution of the finite - angle imaging optimization model can be obtained first as:

[0085]

[0086] Among them, both a and b represent non-boundary points in the horizontal direction of the image, and l represents an adjustment term.

[0087] Specifically, the derivation process of the analytical solution can be as follows:

[0088] After obtaining the limited-angle imaging optimization model, consider the Eular-Lagrange equation We get:

[0089] (μ + 1)v xx = μφ xx , x ∈ (a, b)

[0090]

[0091] Within the segment (a, b), the Euler-Lagrange equation is a Poisson problem with Dirichlet boundary conditions:

[0092]

[0093] By subtracting the linear function l(x) from the function v(x), the problem is homogenized as:

[0094]

[0095] According to the strong extreme value principle, the unique solution of the equation is:

[0096]

[0097] That is, the analytical solution is:

[0098]

[0099] Then, through this analytical solution, the reconstructed image values for removing limited-angle artifacts can be directly determined to obtain the reconstructed image values of each base material for removing limited-angle artifacts, without the need to determine the reconstructed image values for removing limited-angle artifacts through iteration, reducing the computational amount required for solving and improving the removal speed of limited-angle artifacts.

[0100] In addition, in practical applications, in order to improve the image quality of the reconstructed image of the plate-like object to be measured, after obtaining the reconstructed image of the plate-like object to be measured, the reconstructed image of the plate-like object to be measured can also be detected to determine whether it meets the preset requirements. Correspondingly, the removing of limited-angle artifacts from the reconstructed images of various base materials based on the preset limited-angle imaging optimization model to obtain the reconstructed image of the plate-like object to be measured specifically includes:

[0101] Removing limited-angle artifacts from the reconstructed images of various base materials based on the preset limited-angle imaging optimization model to obtain the reconstructed images of various base materials with limited-angle artifacts removed;

[0102] Check whether the reconstructed images with finite-angle artifacts removed for various base materials meet the preset requirements;

[0103] If the preset requirements are met, use the reconstructed images with finite-angle artifacts removed for various base materials as the reconstructed images of the plate-like object to be measured;

[0104] If the preset requirements are not met, use the reconstructed images with finite-angle artifacts removed for various base materials as the estimated values of various base material images, and re-execute the step of image reconstruction based on multiple sets of projection data and the estimated values of various base material images until the preset requirements are met to obtain the reconstructed images of the plate-like object to be measured.

[0105] Specifically, the preset requirements are pre-set. For example, the number of iterations (i.e., the number of times of re-execution) reaches the preset number of times, or the image difference between the reconstructed images with finite-angle artifacts removed for the base materials determined in two adjacent iterations is less than the predicted difference threshold, etc. The preset requirements are used as the end condition of the iterative process. Therefore, when the preset requirements are met, it means that the iterative process meets the end condition, and thus the reconstructed images with finite-angle artifacts removed for various base materials can be used as the reconstructed images of the plate-like object to be measured; conversely, when the preset requirements are not met, it means that the iterative process does not meet the end condition, and then the iterative process is executed, that is, the reconstructed images with finite-angle artifacts removed for various base materials are used as the estimated values of various base material images, and the iteration is carried out again until the preset requirements are met.

[0106] In the embodiments of the present application, by using a preset finite-angle imaging optimization model to remove finite-angle artifacts and combining the finite-angle imaging optimization model with the tilt projection correction technology, finite-angle artifacts and metal artifacts can be removed simultaneously, improving the image quality of the reconstructed images. At the same time, when using the finite-angle imaging optimization model to remove finite-angle artifacts in the present application, by making full use of the gray information and gradient information of the visible boundaries in the reconstructed images, the internal structures submerged by finite-angle artifacts can be restored by an analytical method, and high-quality reconstructed images can be obtained after a small number of iterations, improving the removal speed of finite-angle artifacts.

[0107] Based on the above plate-like object finite-angle CT image reconstruction method, this embodiment provides a plate-like object finite-angle CT image reconstruction device, as Figure 11 shown, the plate-like object finite-angle CT image reconstruction device specifically includes:

[0108] An acquisition module 100, configured to perform an energy spectrum finite-angle scan on the plate-like object to be measured by using a CT system, and acquire multiple sets of projection data of the plate-like object to be measured;

[0109] An assignment module 200, configured to assign initial values to the various base material images of the plate-like object to be measured to obtain the estimated values of the various base material images;

[0110] A reconstruction module 300, configured to perform image reconstruction based on multiple sets of projection data and various estimated values of basis material images to obtain various reconstructed image values of basis materials;

[0111] An artifact removal module 400, configured to remove finite-angle artifacts from various reconstructed images of basis materials based on a preset finite-angle imaging optimization model to obtain a reconstructed image of the measured plate-like object.

[0112] Based on the above method for reconstructing a finite-angle CT image of a plate-like object, this embodiment provides a computer-readable storage medium storing one or more programs that can be executed by one or more processors to implement the steps in the method for reconstructing a finite-angle CT image of a plate-like object as described in the above embodiment.

[0113] Based on the above method for reconstructing a finite-angle CT image of a plate-like object, the present application further provides a terminal device, as Figure 12 shown, which includes at least one processor 20; a display screen 21; and a memory 22, and may further include a communication interface 23 and a bus 24. Among them, the processor 20, the display screen 21, the memory 22, and the communication interface 23 can complete mutual communication through the bus 24. The display screen 21 is set to display a preset user guidance interface in the initial setting mode. The communication interface 23 can transmit information. The processor 20 can call the logical instructions in the memory 22 to execute the method in the above embodiment.

[0114] In addition, when the logical instructions in the above memory 22 are implemented in the form of a software functional unit and sold or used as an independent product, they can be stored in a computer-readable storage medium.

[0115] The memory 22, as a computer-readable storage medium, can be set to store software programs and computer-executable programs, such as program instructions or modules corresponding to the methods in the embodiments of the present disclosure. The processor 20 executes functional applications and data processing by running the software programs, instructions, or modules stored in the memory 22, that is, implements the methods in the above embodiments.

[0116] The memory 22 may include a program storage area and a data storage area. Among them, the program storage area may store an operating system and application programs required for at least one function; the data storage area may store data created according to the use of the terminal device, etc. In addition, the memory 22 may include a high-speed random access memory and may also include a non-volatile memory. For example, various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disc, may also be a transient storage medium.

[0117] In addition, the specific processes of loading and executing multiple instructions in the above-mentioned storage medium and the terminal device have been described in detail in the above method and will not be repeated here.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for reconstructing a limited-angle CT image of a plate-shaped object, characterized in that, The specific method for reconstructing the limited-angle CT image of the plate-shaped object includes the following steps: Use a CT system to perform an energy-spectrum limited-angle scan on the plate-shaped object to be measured, and obtain multiple groups of projection data of the plate-shaped object to be measured; Assign initial values to the images of various base materials of the plate-shaped object to be measured to obtain estimated values of the images of various base materials; Perform image reconstruction based on multiple groups of projection data and the estimated values of the images of various base materials to obtain the reconstructed image values of various base materials; Remove the limited-angle artifacts from the reconstructed images of various base materials based on a preset limited-angle imaging optimization model to obtain the reconstructed image of the plate-shaped object to be measured.

2. The method for reconstructing a limited-angle CT image of a plate-shaped object according to claim 1, wherein The step of using a CT system to perform a limited-angle scan on the plate-shaped object to be measured and obtain the projection data of the plate-shaped object to be measured at at least two energy spectra specifically includes: Use the limited-angle CT scan mode to scan the plate-shaped object to be measured with a given high X-ray tube voltage and a given low X-ray tube voltage respectively to obtain the projection data of the high energy spectrum and the projection data of the low energy spectrum.

3. The method for reconstructing a limited-angle CT image of a plate-shaped object according to claim 1, characterized in that The step of performing image reconstruction based on multiple groups of projection data and the estimated values of the images of various base materials to obtain the reconstructed image values of various base materials specifically includes: Use the tilt projection correction technique to perform image reconstruction based on multiple groups of projection data and the estimated values of the images of various base materials to obtain the reconstructed image values of various base materials.

4. The method for reconstructing a limited-angle CT image of a plate-shaped object according to claim 1, characterized in that, The construction process of the limited-angle imaging optimization model is as follows: Construct a smoothness constraint term based on the directional partial derivatives of the reconstructed image values for removing limited-angle artifacts to be calculated; Construct an approximation constraint term based on the directional partial derivatives of the reconstructed images of the base materials and the directional partial derivatives of the reconstructed image values for removing limited-angle artifacts to be calculated; Integrate the smoothness constraint term and the approximation constraint term over the set of positions of non-boundary points on the reconstructed images of the base materials to obtain an objective function; Construct a limited-angle imaging optimization model by minimizing the objective function.

5. The method for reconstructing a limited-angle CT image of a plate-shaped object according to claim 1 or 4, characterized in that, The limited-angle imaging optimization model is: where, u represents the image optimized by the finite-angle imaging optimization model, Ω′ represents the set of positions of non-boundary points on the reconstructed image, v represents the value of the reconstructed image after removing finite-angle artifacts, φ represents the reconstructed image of the base material, μ represents a preset constant coefficient, · x represents the directional partial derivative in the horizontal direction x of the image.

6. The method for reconstructing a limited-angle CT image of a plate-shaped object according to claim 5, wherein The analytical solution of the limited-angle imaging optimization model is: Wherein, both a and b represent non-boundary points in the horizontal direction of the image, l(x) represents a regulation term, and x represents a non-boundary point between a and b in the horizontal direction of the image.

7. The method for reconstructing a limited-angle CT image of a plate-shaped object according to claim 1, wherein, The step of removing the limited-angle artifacts from the reconstructed images of various base materials based on a preset limited-angle imaging optimization model to obtain the reconstructed image of the plate-shaped object to be measured specifically includes: Remove the limited-angle artifacts from the reconstructed images of various base materials based on a preset limited-angle imaging optimization model to obtain the reconstructed images of various base materials with limited-angle artifacts removed; Detect whether the reconstructed images of various base materials with limited-angle artifacts removed meet the preset requirements; If the preset requirements are met, use the reconstructed images of various base materials with limited-angle artifacts removed as the reconstructed image of the plate-shaped object to be measured; If the preset requirements are not met, use the reconstructed images of various base materials with limited-angle artifacts removed as the estimated values of the images of various base materials, and re-execute the step of performing image reconstruction based on multiple groups of projection data and the estimated values of the images of various base materials until the preset requirements are met to obtain the reconstructed image of the plate-shaped object to be measured.

8. A limited-angle CT image reconstruction device for a plate-shaped object, characterized in that, The specific plate-shaped object limited-angle CT image reconstruction device includes: An acquisition module, configured to use a CT system to perform an energy-spectrum limited-angle scan on the plate-shaped object to be measured, and obtain multiple groups of projection data of the plate-shaped object to be measured; An assignment module, configured to assign initial values to various base material images of the to-be-tested plate-shaped object to obtain various estimated values of the base material images; A reconstruction module, configured to perform image reconstruction based on multiple sets of projection data and various estimated values of the base material images to obtain various reconstructed image values of the base materials; An artifact removal module, configured to perform limited-angle artifact removal on various reconstructed base material images based on a preset limited-angle imaging optimization model to obtain a reconstructed image of the to-be-tested plate-shaped object.

9. A computer-readable storage medium, characterized in that The computer-readable storage medium stores one or more programs, and the one or more programs can be executed by one or more processors to implement the steps in the limited-angle CT image reconstruction method of the plate-shaped object according to any one of claims 1-7.

10. A terminal device, characterized in that, Including: A processor and a memory; A computer-readable program executable by the processor is stored on the memory; When the processor executes the computer-readable program, the steps in the limited-angle CT image reconstruction method of the plate-shaped object according to any one of claims 1-7 are implemented.

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