Method, device and equipment for removing ring artifacts in CT (Computed Tomography) imaging and medium

Abstract

The invention discloses a method for removing ring artifacts in CT imaging. The method comprises the following steps: correcting a projection sinogram of a central channel area of a projection domain detector based on a projection domain correction table; performing CT reconstruction on the corrected projection sinogram to obtain a reconstructed original CT image; extracting an image domain ring artifact of the original CT image; and subtracting the image domain ring artifact from the original CT image to obtain a ring-removed CT image. Therefore, by introducing the central channel selection window to carry out projection domain ring removal on the central channel area and carrying out integral ring removal in the image domain, the problem of black and white centers can be well inhibited under the condition that CT image distortion is not caused, the quality of the CT image, especially the photon counting CT image, is improved to a great extent, and the method can be widely applied to CT image processing.

Description

Technical Field

[0001] The present invention relates to a method, apparatus, device and medium for removing circular artifacts in CT imaging, and relates to the field of image processing. Background Art

[0002] During the CT imaging process, the inconsistent response of the detector will result in a large number of circular artifacts in the reconstructed CT image. Due to the immature technology process of the current photon counting detector, the inconsistent response is more serious. Therefore, more correction terms are required in photon counting CT to obtain the required image quality. However, despite adding many detector correction terms, such as flat field correction, non-linear correction, etc., the detector response values still have inconsistencies, which are manifested as strip artifacts on the projection domain sinogram. After back-projection, they are accumulated into the reconstructed CT image and present concentric circles centered on the image center in the image domain, which are also called circular artifacts. The closer to the image center, the greater the back-projection accumulation effect, and the more serious the circular artifacts are, and they are manifested as black heart or white heart artifacts at the center position.

[0003] There are two ideas for removing circular artifacts in CT images, namely, based on the projection domain and the image domain. Circular artifact removal in the projection domain is to process the strip artifacts on the projection domain sinogram, while circular artifact removal in the image domain often requires first converting the CT image to polar coordinates, then processing in the polar coordinate system, and finally converting back to the Cartesian coordinate system. The advantage of circular artifact removal in the projection domain is that it processes the data source, the inconsistency is not accumulated and amplified, it is easier to correct, and it can also well achieve consistency correction for the central channel, thus avoiding the black and white heart problems of the image. Its disadvantage is that the data processing in the projection domain will cause large CT value changes in the CT image after the reconstruction algorithm, which is easy to cause image distortion. The advantage of circular artifact removal in the image domain is that the influence on CT values is controllable and often does not cause large changes to CT values. The disadvantage is that due to the accumulation effect, the closer to the center, the larger the artifacts are. Since the image center will be at the image edge in the polar coordinate system after polar coordinate conversion, the circular artifact removal at the edge is often not ideal. Therefore, circular artifact removal in the image domain cannot well remove circular artifacts in the central region, and there are still black and white heart problems.

[0004] Therefore, how to remove circular artifacts from the CT image without causing image distortion, especially to solve the black and white heart problems, is particularly important. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art. For this reason, in view of the above problems, the purpose of the present invention is to provide a method, apparatus, device and medium for removing circular artifacts in CT imaging that can well suppress the black and white heart problems without causing CT image distortion.

[0006] In order to achieve the above invention purpose, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a method for removing circular artifacts in CT imaging, including: Correcting the projection sinogram of the projection domain detector central channel area based on a projection domain correction table; Performing CT reconstruction on the corrected projection sinogram to obtain a reconstructed original CT image; Extracting the image domain circular artifacts of the original CT image; Subtracting the image domain circular artifacts from the original CT image to obtain a CT image after removing the ring.

[0007] In some possible embodiments, the projection sinogram is data composed of the projection values of all channels of the detector at all projection angles of the imaging object, and the projection value is the linear attenuation coefficient of the object calculated under the corresponding X-ray path. The calculation formula is: ; Wherein, is the size of the projected photon number after attenuation by the object at a certain pixel, is the size of the photon number at the corresponding pixel projected only through air without passing through the object, is the size of the projected value at the corresponding pixel calculated.

[0008] In some possible embodiments, the generation process of the projection domain correction table includes: Obtaining a sinogram containing all angles, and obtaining an average projection by averaging the projections at all angles according to the sinogram; Calculating the non-uniform response residual value of the object imaging at each pixel of the detector through the average projection; Performing central channel area residual extraction on the non-uniform response residual value to obtain a projection domain correction table.

[0009] In some possible embodiments, performing central channel area residual extraction on the non-uniform response residual value to obtain a projection domain correction table includes: The non-uniform response residual value in the central channel area adopts the formula: ; wherein, is the central channel window function, is the residual in the central channel area after passing through the window function; All the extracted channel coordinate indexes and the corresponding non-uniform response residual values in the central channel area constitute the projection domain correction table.

[0010] In some possible embodiments, correcting the projection sinogram of the projection domain detector central channel area based on the projection domain correction table includes: Subtract the projection values at each pixel in the central channel region of the sine diagram of all angles from the non-uniformity response residual values corresponding to the central channel region. Among them, the non-uniformity response residual values in the central channel region are obtained according to the channel coordinate index, and the corrected residual values corresponding to the channels are obtained according to the projection domain correction table obtained above: ; Among them, is the projection at the i-th angle, is the corrected projection at the i-th angle, is the obtained corrected residual.

[0011] In some possible implementation manners, the process of extracting annular artifacts in the image domain includes: Transform the original CT image in the Cartesian coordinate system into a CT image in the polar coordinate system; Obtain a smoothed image by passing the CT image in the polar coordinate system through a filter; Subtract the smoothed image from the image in the polar coordinate system to obtain a rough annular artifact image in the polar coordinate system; Process the rough annular artifact image with a low-pass filter to filter out other noises except the annular artifacts to obtain a fine annular artifact image in the polar coordinate system; Convert the fine annular artifact image into the Cartesian coordinate system to complete the extraction of the annular artifact image.

[0012] In some possible implementation manners, subtract the annular artifacts in the image domain from the original CT image to obtain a CT image after removing the rings, and the calculation formula is: ; Among them, is the original CT image, is the extracted annular artifact image, is the final CT image after removing the rings.

[0013] In a second aspect, the present invention also provides a device for removing annular artifacts in CT imaging. The device includes: A correction unit configured to correct the projection sine diagram of the central channel region of the detector in the projection domain based on the projection domain correction table; A reconstruction unit configured to perform CT reconstruction on the corrected projection sine diagram to obtain a reconstructed original CT image; An artifact extraction unit configured to extract annular artifacts in the image domain of the original CT image; A de-ring unit configured to subtract the annular artifacts in the image domain from the original CT image to obtain a CT image after removing the rings.

[0014] In a third aspect, the present invention further provides an electronic device, comprising: at least one processor; and a memory communicatively connected to the processor; wherein, the memory stores instructions executable by the processor, and when the instructions are executed by the processor, the processor is enabled to execute the method described above.

[0015] In a fourth aspect, the present invention further provides a computer-readable storage medium storing one or more programs, the one or more programs including computer instructions for causing a computer to execute the method described above.

[0016] Due to the above technical solutions adopted by the present invention, it has the following characteristics: by introducing a central channel selection window, the present invention performs projection domain de-ringing on the central channel region, which is a region with limited de-ringing ability in the image domain but can be better processed in the projection domain. Then, overall de-ringing in the image domain can well suppress the black and white heart problem without causing CT image distortion, and greatly improve the quality of CT images, especially photon counting CT images. In summary, the present invention can be widely applied to CT image processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Throughout the drawings, the same reference numerals are used to denote the same components. In the drawings: Figure 1 is a flowchart of the method for CT imaging de-ringing artifacts according to an embodiment of the present invention; Figure 2 is a flowchart of the method for correcting the central channel region in the projection domain according to an embodiment of the present invention; Figure 3 is a flowchart of obtaining the non-uniform response residual value in the projection domain according to an embodiment of the present invention; Figure 4 is a flowchart of extracting the central channel region correction residual according to an embodiment of the present invention; Figure 5 is a flowchart of correcting the central channel region by using the extracted residual term according to an embodiment of the present invention; Figure 6 is a flowchart of image domain de-ringing according to an embodiment of the present invention; Figure 7 is a flowchart of extracting image domain ring artifacts according to an embodiment of the present invention; Figure 8 is a structural diagram of the electronic device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] It should be understood that the terms used herein are for the purpose of describing particular example embodiments only and are not intended to be limiting. Unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" as used herein may also include the plural forms. The terms "comprising", "including", "containing", and "having" are inclusive and thus specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order described or illustrated, unless explicitly indicated as an order of performance. It should also be understood that additional or alternative steps may be used.

[0019] Although the terms first, second, third, etc. may be used herein to describe multiple elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or section from another. Unless the context clearly indicates otherwise, terms such as "first", "second", and other numerical terms when used herein do not imply an order or sequence. Thus, a first element, component, region, layer, or section discussed below may be referred to as a second element, component, region, layer, or section without departing from the teachings of the example embodiments.

[0020] For ease of description, spatial relative relationship terms may be used herein to describe the relationship of one element or feature shown in the figures to another element or feature, such as "inner", "outer", "inside", "outside", "below", "above", etc. Such spatial relative relationship terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the figures.

[0021] Since the CT value of the CT image is less affected and controllable by the image domain de-ringing, but there is a problem of insufficient processing ability for the central region, the projection domain de-ringing can treat all regions of the detector equally and is expected to solve the problem of black and white centers in the image center. However, a large amount of processing on the projection domain data will cause distortion of the CT image. The CT imaging de-ringing artifact method, device, equipment and medium provided by the present invention include: correcting the projection sinogram of the central channel region of the projection domain detector based on the projection domain correction table; performing CT reconstruction on the corrected projection sinogram to obtain the reconstructed original CT image; extracting the image domain circular artifacts of the original CT image; and subtracting the image domain circular artifacts from the original CT image to obtain the de-ringed CT image. Therefore, based on the projection domain correction plus image domain de-ringing, the present invention introduces a central channel selection window in the projection domain to only correct the central channel region in the projection domain, and then performs overall de-ringing in the image domain, which can well suppress the problem of black and white center points without causing distortion of the CT image, and greatly improve the quality of CT images, especially photon counting CT images.

[0022] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention can be more thoroughly understood and the scope of the present invention can be fully conveyed to those skilled in the art.

[0023] Example 1: As Figure 1 shown, the method for CT imaging de-ringing artifacts provided in this embodiment includes: S1. Correction of the central channel region in the projection domain.

[0024] In this embodiment, the sinogram data of the central channel region of the projection domain detector is corrected to ensure a better suppression effect on the circular artifacts in the central channel region and not cause distortion of the reconstructed image. Among them, the central channel of the detector refers to the detector pixel points projected by the X-ray source along the perpendicular to the rotation center axis of the CT system on the detector, and the central channel region of the detector refers to the pixel region with a given window size centered on the central channel of the detector. The sinogram data refers to the data composed of the projection values of all channels of the detector at all projection angles of the imaging object, and the projection value refers to the linear attenuation coefficient of the object calculated under the corresponding X-ray path, which can be obtained through the following formula: ; where is the size of the projected photon number after attenuation by the object at a certain pixel, is the size of the photon number corresponding to the pixel projected only through air without passing through the object, is the calculated size of the projection value corresponding to the pixel.

[0025] In this embodiment, as Figure 2 shown, the process of correcting the central channel region in the projection domain includes: S11. Obtain a sinogram containing all angles (where all angles represent all angles at which the CT system rotates around the imaging object for projection data acquisition), and obtain an average projection by averaging all-angle projections according to the sinogram.

[0026] In this embodiment, the calculation formula for averaging all-angle projections is: ; where N is the number of imaging angles, is the projection value at the i th angle, and is the average projection of all.

[0027] S12. As Figure 3 shown, calculate the non-uniform response residual value of the object imaging under each pixel of the detector through the average projection.

[0028] In this embodiment, calculating the non-uniform response residual value of the object imaging under each pixel of the detector through the average projection includes: S121. Smooth the average projection to obtain the smoothed average projection.

[0029] In this embodiment, the method for smoothing the average projection can adopt mean filtering, Gaussian filtering, median filtering, bilateral filtering, or total variation filtering, etc. The mathematical process can be described as follows: ; ; where is the average projection after smoothing filtering, and is the non-uniform response residual.

[0030] Further, in this embodiment, the median filter is used for smoothing the average projection, and the window width of the filter can be set to 5×5. Taking this as an example, it is not limited to this.

[0031] S122. Subtract the smoothed average projection value from the average projection to obtain the non-uniform response residual value.

[0032] S13. The non-uniform response residual value of the central channel region.

[0033] In this embodiment, as Figure 4As shown in the figure, the extraction of the non-uniform response residual value in the central channel region includes using a suitable central channel selection window to extract the residual value of the central channel region from the non-uniform response residual, and obtaining a projection domain correction table.

[0034] Furthermore, the extraction of the non-uniform response residual value in the central channel region can be described by the following formula: ; where is the central channel window function, is the residual of the central channel region after passing through the window function. The window function is defined as a matrix with values inside the window as close to 1 as possible, values outside the window as close to 0 as possible, and the size is the same as the size of the projection image. Among them, all the extracted channel coordinate indices and the corresponding non-uniform response residual values in the central channel region form the projection domain correction table.

[0035] Furthermore, the central channel selection window can select a rectangular window function, a Gaussian window function, etc.

[0036] Furthermore, the window width of the central channel selection window can be set to an appropriate size according to the severity of the central ring artifact in the image after the actual system reconstruction. For example, the window width can be set to 50 detector channel widths. Taking this as an example, it is not limited to this.

[0037] S14. The projection sinogram after correction in the central channel region.

[0038] In this embodiment, as Figure 5 shown, the extracted non-uniform response residual value in the central channel region is used as the projection domain correction table for all-angle projection correction, and finally the projection sinogram after correction in the central channel region is obtained.

[0039] Furthermore, the process of obtaining the projection sinogram after correction in the central channel region is as follows: subtract the projection value at the central channel region of the sinogram of all angles pixel by pixel from the non-uniform response residual value in the central channel region. Among them, the non-uniform response residual value in the central channel region obtains the correction residual value corresponding to the channel according to the corresponding channel coordinate index based on the obtained projection domain correction table, which can be described by the following formula: ; where is the projection at the i-th angle, is the projection after correction at the i-th angle, is the correction residual obtained above.

[0040] S2. As Figure 6 shown, the corrected projection sinogram passes through the CT reconstruction algorithm to obtain the original CT image after reconstruction.

[0041] In this embodiment, the CT reconstruction algorithm includes the filtered back projection algorithm, the iterative reconstruction algorithm, etc.

[0042] S3. Perform image domain de-ringing.

[0043] In this embodiment, the process of performing image domain de-ringing is as follows: Extract the ring artifacts in the image domain, and subtract the extracted ring artifacts from the reconstructed original CT image to obtain the de-ringed CT image.

[0044] Further, as shown in FIG. 7, the process of extracting the ring artifacts in the image domain includes: S31. Transform the original CT image in the Cartesian coordinate system into a CT image in the polar coordinate system.

[0045] S32. Pass the CT image in the polar coordinate system through a filter to obtain a smoothed image.

[0046] In this embodiment, the filter can be a median filter, taking this as an example, not limited thereto.

[0047] S33. Subtract the smoothed image from the image in the polar coordinate system to obtain a rough ring artifact image in the polar coordinate system.

[0048] S34. Process the rough ring artifact image with a low-pass filter to filter out other noises except the ring artifacts to obtain a fine ring artifact image in the polar coordinate system.

[0049] In this embodiment, the low-pass filter can be a mean filter, taking this as an example, not limited thereto.

[0050] S35. Transform the fine ring artifact image into the Cartesian coordinate system to complete the extraction of the ring artifact image.

[0051] S4. Obtain the de-ringed image.

[0052] In this embodiment, the method for obtaining the de-ringed image is to subtract the extracted ring artifact image from the original CT image, and the calculation formula is: ; where is the original CT image, is the extracted ring artifact image, is the final de-ringed CT image.

[0053] In summary, since the artifacts at the center channel of the present invention have been well suppressed in the projection domain, the problem of black and white centers in the final de-ringed CT image is also solved.

[0054] Embodiment 2: The above Embodiment 1 provides a method for removing circular artifacts in CT imaging. Correspondingly, this embodiment provides a device for removing circular artifacts in CT imaging. The device provided in this embodiment can implement the method for removing circular artifacts in CT imaging of Embodiment 1, and the device can be implemented in a software, hardware, or software-hardware combination manner. For the convenience of description, when describing this embodiment, various units are described separately according to their functions. Of course, in implementation, the functions of each unit can be implemented in the same or multiple software and / or hardware. For example, the device can include integrated or separate functional modules or functional units to execute the corresponding steps in each method of Embodiment 1. Since the device in this embodiment is basically similar to the method embodiment, the description process of this embodiment is relatively simple, and the relevant parts can refer to the partial description of Embodiment 1. The embodiment of the device for removing circular artifacts in CT imaging provided by the present invention is only illustrative.

[0055] Specifically, the present invention further provides a device for removing circular artifacts in CT imaging, and the device includes: A correction unit configured to correct the projection sinogram of the central channel area of the projection domain detector based on a projection domain correction table; A reconstruction unit configured to perform CT reconstruction on the corrected projection sinogram to obtain a reconstructed original CT image; An artifact extraction unit configured to extract the image domain circular artifacts of the original CT image; A de-ring unit configured to subtract the image domain circular artifacts from the original CT image to obtain a de-ringed CT image.

[0056] Embodiment 3: This embodiment provides an electronic device corresponding to the method for removing circular artifacts in CT imaging provided in Embodiment 1. The electronic device can be an electronic device for a client, such as a mobile phone, a laptop computer, a tablet computer, a desktop computer, etc., to execute the method of Embodiment 1.

[0057] As Figure 8 shown, the electronic device includes a processor, a memory, a communication interface, and a bus. The processor, the memory, and the communication interface are connected through the bus to complete communication with each other. A computer program that can run on the processor is stored in the memory. When the processor runs the computer program, it executes the method of Embodiment 1. The implementation principle and technical effect are similar to those of Embodiment 1 and will not be elaborated here. Those skilled in the art can understand that Figure 8 the structure shown in

[0058] In a preferred embodiment, when the logic instructions in the above-mentioned memory can be implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of this application, in essence, or the part that contributes to the prior art or a part of this technical solution can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of this application. The aforementioned storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), and optical discs that can store program codes.

[0059] In a preferred embodiment, the processor can be various types of general-purpose processors such as a central processing unit (CPU) or a digital signal processor (DSP), which is not limited herein.

[0060] Embodiment 4: This embodiment provides a computer-readable storage medium storing one or more programs, and the one or more programs include computer instructions. When the computer instructions are executed by a computer, the computer is caused to execute the method provided in the above-mentioned Embodiment 1.

[0061] In a preferred embodiment, the computer-readable storage medium can be a tangible device that holds and stores instructions executed. For example, it can be, but is not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any combination of the above. The computer-readable storage medium stores computer program instructions, and these computer program instructions cause the computer to execute the method provided in the above-mentioned Embodiment 1.

[0062] This application is described with reference to the flowcharts and / or block diagrams of methods, devices (apparatus), and computer program products according to the embodiments of this application. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0063] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to operate in a particular manner, such that the instructions stored in the computer-readable memory produce a manufacture including an instruction device that implements the function specified in one process Figure 1 one process or more processes and / or blocks Figure 1 specified in a block or more blocks.

[0064] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, so that the instructions executed on the computer or other programmable apparatus provide steps for implementing the function specified in one process Figure 1 one process or more processes and / or blocks Figure 1 specified in a block or more blocks.

[0065] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between each embodiment can be referred to each other. The key point of each embodiment is to illustrate the differences from other embodiments. In the description of this specification, the descriptions with reference to the terms "a preferred embodiment", "furthermore", "specifically", "in this embodiment", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments of this specification. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention 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 recorded in the foregoing embodiments, or equivalently replace 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 invention.

Claims

1. A method for removing circular artifacts in CT imaging, characterized in that, Including: Correcting the projection sinogram of the central channel area of the projection domain detector based on the projection domain correction table; Performing CT reconstruction on the corrected projection sinogram to obtain the reconstructed original CT image; Extracting the image domain circular artifacts of the original CT image; Subtracting the image domain circular artifacts from the original CT image to obtain the CT image after removing the ring.

2. The method for removing circular artifacts in CT imaging according to claim 1, wherein, The projection sinogram is data composed of the projection values of all channels of the detector at all projection angles of the imaging object. The projection value is the linear attenuation coefficient of the object calculated under the corresponding X-ray path, and the calculation formula is: ； Among them, is the magnitude of the projected photon number after attenuation by the object for a certain pixel, is the magnitude of the photon number corresponding to the projection through air without passing through the object for the corresponding pixel, is the magnitude of the calculated projection value for the corresponding pixel.

3. The method for removing circular artifacts in CT imaging according to claim 1, wherein The generation process of the projection domain correction table includes: Obtaining the sinogram including all angles, and obtaining the average projection by averaging the projections of all angles according to the sinogram; Calculating the non-uniform response residual value of the object imaging under each pixel of the detector through the average projection; Performing central channel area residual extraction on the non-uniform response residual value to obtain the projection domain correction table.

4. The method for removing circular artifacts in CT imaging according to claim 1, wherein Performing central channel area residual extraction on the non-uniform response residual value to obtain the projection domain correction table, including: The non-uniformity response residual value of the central channel region adopts the formula: ; where is the central channel window function, is the residual of the central channel region after passing through the window function; The projection domain correction table is composed of all extracted channel coordinate indexes and the corresponding non-uniform response residual values in the central channel area.

5. The method for removing circular artifacts in CT imaging according to claim 4, characterized in that, Correcting the projection sinogram of the central channel area of the projection domain detector based on the projection domain correction table, including: Subtracting the projection values at the central channel area of the sinograms of all angles pixel by pixel from the corresponding non-uniform response residual values in the central channel area. Among them, the non-uniform response residual value in the central channel area is obtained according to the channel coordinate index, and the correction residual value under the corresponding channel is obtained according to the obtained projection domain correction table: ； Among them, is the projection at the i-th angle, is the projection after correction at the i-th angle, is the obtained correction residual.

6. The method for removing circular artifacts in CT imaging according to claim 1, wherein The image domain circular artifact extraction process includes: Transforming the original CT image in the Cartesian coordinate system into a CT image in the polar coordinate system; Obtaining the smoothed image by passing the CT image in the polar coordinate system through a filter; Subtracting the smoothed image from the image in the polar coordinate system to obtain the rough ring artifact image in the polar coordinate system; Processing the rough ring artifact image with a low-pass filter to filter out other noises except the circular artifacts to obtain the fine ring artifact image in the polar coordinate system; Converting the fine ring artifact image into the Cartesian coordinate system to complete the extraction of the circular artifact image.

7. The method for removing circular artifacts in CT imaging according to claim 1, wherein, Subtracting the image domain circular artifacts from the original CT image to obtain the CT image after removing the ring, and the calculation formula is: ； Among them, is the original CT image, is the extracted circular artifact image, is the final CT image after removing the ring.

8. An apparatus for removing circular artifacts in CT imaging, characterized in that, The device includes: A correction unit configured to correct the projection sinogram of the central channel area of the projection domain detector based on the projection domain correction table; A reconstruction unit configured to perform CT reconstruction on the corrected projection sinogram to obtain the reconstructed original CT image; An artifact extraction unit configured to extract the image domain circular artifacts of the original CT image; A de-ring unit configured to subtract the image domain circular artifacts from the original CT image to obtain the CT image after removing the ring.

9. An electronic device, characterized in that, Including: At least one processor; And a memory communicatively connected to the processor; wherein, the memory stores instructions executable by the processor, and the instructions are executed by the processor so that the processor can execute the method according to any one of claims 1-7.

10. A computer-readable storage medium storing one or more programs, characterized in that, The one or more programs include computer instructions for causing a computer to execute the method according to any one of claims 1-7.

Images