Photon counting CT (Computed Tomography) non-uniformity response correction method, device, equipment and medium

Abstract

The invention discloses a photon counting CT non-uniformity response correction method, device and equipment and a medium, and the method comprises the steps: carrying out the image collection of a to-be-imaged object through a photon counting CT, and obtaining a multi-energy object projection drawing; performing air correction on the multi-energy object projection drawing to obtain a multi-energy object attenuation projection drawing after air correction; and performing non-uniformity response correction on the multi-energy object attenuation projection drawing based on the non-linear correction table to obtain a corrected multi-energy object attenuation projection drawing. Therefore, different correction die bodies can be used according to different imaging objects to achieve multi-imaging scene correction, and a more excellent non-uniform response correction effect is achieved.

Description

Technical Field

[0001] The present invention relates to a method, device, equipment and medium for photon counting CT non-uniformity response correction, and relates to the field of photon counting CT imaging. Background Technique

[0002] Photon counting CT is a computed tomography technology characterized by semiconductor detectors. It can identify and count the energy of X-rays, improve spatial resolution and reduce radiation dose. Photon counting CT uses photon counting detectors, which have higher energy resolution ability, higher spatial resolution and higher detection efficiency.

[0003] However, due to the immature process of current photon counting detectors, there are serious non-uniform response problems between detector crystal modules and between pixels and pixels, which will lead to serious ring artifacts in the reconstructed CT images, thus affecting the image quality and the identification of lesions. The main reasons for this non-uniform response may be: (1) the crystal of the photon counting detector is impure or there are differences in crystals between different modules; (2) the inconsistency of the pixel post-processing circuit; (3) the inconsistency of threshold calibration.

[0004] In order to suppress the image artifact problem caused by the non-uniform response of the photon counting detector, it can be considered from three aspects: hardware-side methods, image post-processing methods and correction methods. Among them, the hardware-side methods can use a moving detector or a spiral scanning method for imaging to average the response differences between different pixels. However, the hardware-side methods increase the complexity of the system and reduce the spatial resolution at the same time. The image post-processing method utilizes the spatial structure characteristics of the artifacts, which appear as strip artifacts on the sinogram and as concentric ring artifacts on the reconstructed image. Then, the artifacts can be removed by filtering methods. However, it is difficult to completely suppress the ring artifacts solely by the image post-processing method, and new artifacts and a decrease in image resolution may be introduced. The correction method adopts the detector non-uniformity correction method. The detector non-uniformity correction method is an important part of the CT imaging data processing flow, which is to collect imaging data under different conditions in advance, and then calculate the corresponding correction model parameters to obtain a correction table to correct the actual imaging data. Common photon counting detector correction methods such as flat field correction, polynomial nonlinear correction, polynomial material decomposition correction, correction based on detector response or based on system spectrum estimation, etc. However, due to the high non-linearity and diversity of the pixel responses of the photon counting detector, the above correction methods are still difficult to completely correct the non-uniformity between pixel responses, and ring artifacts still remain in the image. At the same time, the above correction methods have limited applicable scenarios. For example, the polynomial material decomposition correction method based on PMMA and AL dual-material phantoms has a good correction effect on common biological tissues, but when the biological tissue is injected with a high-attenuation contrast agent such as iodine, the correction effect is very poor. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, in view of the above problems, the object of the present invention is to provide a method, device, equipment and medium for photon counting CT non-uniformity response correction, which can solve the problems of unsatisfactory correction effect and limited applicable scenarios of the existing photon counting CT non-uniformity response correction method.

[0006] In order to achieve the above object of the invention, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the photon counting CT non-uniformity response correction method provided by the present invention includes:

[0008] Performing image acquisition on the object to be imaged by a photon counting CT to obtain a multi-energy object projection map;

[0009] Performing air correction on the multi-energy object projection map to obtain an air-corrected multi-energy object attenuation projection map;

[0010] Performing non-uniformity response correction on the multi-energy object attenuation projection map based on a non-linear correction table to obtain a corrected multi-energy object attenuation projection map.

[0011] In some possible implementation manners, the multi-energy object projection map refers to a photon number distribution map of the object to be imaged under multiple energy windows collected by a photon counting CT at multiple different energy thresholds, where the energy window refers to an energy interval composed of multiple energy thresholds.

[0012] In some possible implementation manners, the formula for performing air correction on the multi-energy object projection map to obtain an air-corrected multi-energy object attenuation projection map is:

[0013]

[0014] Where is the size of the object projection photons of a certain pixel of the multi-energy object projection map under the i-th energy window, is the size of the air projection photons of the corresponding pixel of the multi-energy air projection under the i-th energy window, P i is the projection value of the corresponding pixel of the air-corrected multi-energy object attenuation projection map.

[0015] In some possible implementation manners, the generation process of the non-linear correction table includes:

[0016] Designing a variety of material flat phantoms, and performing combined acquisition on the flat phantoms to obtain multi-energy projection maps of the phantoms under different combinations;

[0017] Air correction is performed on the multi - energy projection image of the phantom to obtain the multi - energy attenuation projection images of the phantom under different combinations, and all combinations are traversed to obtain the multi - energy attenuation projection images of the phantom under all combinations;

[0018] Calculate the ideal attenuation projection images of the multi - energy attenuation projection images of the phantom under all combinations;

[0019] Based on the ideal attenuation projection images, non - linear polynomial model fitting is performed pixel - by - pixel to calculate the non - linear correction table for each pixel.

[0020] In some possible implementation manners, the ideal attenuation projection images of the multi - energy attenuation projection images of the phantom under all combinations are obtained by fitting a non - linear equation using the spatial coordinate relationship of the multi - energy attenuation projection pixels of the phantom. The non - linear equation selects a quadratic equation, and the calculation formula is:

[0021]

[0022] where m and n respectively represent the horizontal and vertical coordinates of the detector pixels, represents the ideal attenuation projection value of the (m, n) - th pixel in the i - th energy window, and a i represents the calculation coefficient of the ideal attenuation projection fitting in the i - th energy window.

[0023] In some possible implementation manners, the generation of the non - linear correction table is by using a non - linear polynomial model to fit the ideal attenuation projection and the actual attenuation projection pixel - by - pixel, and calculating the non - linear correction coefficient for each energy window Finally, a non - linear correction table is generated. Among them, the non - linear polynomial model adopts a first - order polynomial model, a second - order polynomial model or a third - order polynomial model. When performing non - uniform response correction on the multi - energy object attenuation projection image, the non - linear polynomial model used needs to be consistent with the non - linear polynomial model used when generating the above non - linear correction table.

[0024] In some possible implementation manners, the flat phantom selects a PMMA flat plate, an aluminum flat plate, an iodine - containing solution flat plate or a calcium - containing solution flat plate; the acquisition number combination of the flat phantom selects the acquisition number of a single - material flat phantom with different thicknesses, the acquisition number of a single - material flat phantom with different concentrations of solution, or the acquisition number of a combination of multiple materials; the area of the flat phantom should be large enough to cover all the effective detection areas of the photon - counting detector.

[0025] In a second aspect, the present invention also provides a photon - counting CT non - uniform response correction device, and the device includes:

[0026] An image acquisition unit, configured to perform image acquisition on the object to be imaged through a photon - counting CT to obtain a multi - energy object projection image;

[0027] An air correction unit, configured to perform air correction on the multi-energy object projection image to obtain an air-corrected multi-energy object attenuation projection image;

[0028] A non-uniformity response correction unit, configured to perform non-uniformity response correction on the multi-energy object attenuation projection image based on a non-linear correction table to obtain a corrected multi-energy object attenuation projection image.

[0029] In a third aspect, the present invention further provides an electronic device, including: 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 according to the above.

[0030] 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.

[0031] Due to the above technical solutions adopted by the present invention, it has the following characteristics:

[0032] 1. The photon counting CT non-uniformity response correction method provided by the present invention can use different correction phantoms according to different imaging objects to achieve multi-imaging scene correction, and fully utilizes the multi-energy window imaging data to achieve a more excellent non-uniform response correction effect.

[0033] 2. The calibration and correction processes of the present invention are simple, the calculation amount in the correction process is small, and it can be easily integrated into the existing photon counting CT system.

[0034] In summary, the present invention can be widely applied to photon counting CT imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] 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 represent the same components. In the drawings:

[0036] Figure 1 is a flowchart of the photon counting CT non-uniform response correction method according to an embodiment of the present invention;

[0037] Figure 2 is a flowchart of the multi-material flat panel non-linear calibration production table according to an embodiment of the present invention;

[0038] Figure 3 is a schematic diagram of the flat panel phantom acquisition data according to an embodiment of the present invention;

[0039] Figure 4 Schematic diagrams of the flat mold body and the solution flat mold body according to an embodiment of the present invention;

[0040] Figure 5 Schematic diagram of the stepped mold according to an embodiment of the present invention;

[0041] Figure 6 Schematic diagram of the multi - material combination according to an embodiment of the present invention;

[0042] Figure 7 Schematic diagram of the photon - counting detector pixel index according to an embodiment of the present invention;

[0043] Figure 8 Comparison effect diagrams of the attenuation projection map before and after non - uniformity response correction according to an embodiment of the present invention;

[0044] Figure 9 Structural diagram of the electronic device according to an embodiment of the present invention. Detailed implementation manners

[0045] It should be understood that the terms used herein are for the purpose of describing specific 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 the 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 their combinations. The method steps, processes, and operations described herein are not to be construed as necessarily requiring them to be performed in the particular order described or illustrated, unless the execution order is explicitly stated. It should also be understood that alternative or additional steps may be used.

[0046] Although the terms first, second, third, etc. may be used in this document 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 only be used 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 used herein do not imply an order or sequence. Thus, the first element, component, region, layer, or section discussed below may be referred to as the second element, component, region, layer, or section without departing from the teachings of the example embodiments.

[0047] For ease of description, spatially relative terms may be used herein to describe the relationship of one element or feature relative to another element or feature as shown in the figures, such as "inside", "outside", "inner side", "outside", "below", "above", etc. Such spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the figures.

[0048] In order to solve the problem that the correction effect of the existing photon counting CT non-uniform response correction method is not ideal and the applicable scenes are limited. The present invention provides a photon counting CT non-uniform response correction method, device, equipment and medium, including: performing image acquisition on the imaging object through photon counting CT to obtain a multi-energy object projection map; performing air correction on the multi-energy object projection map to obtain an air-corrected multi-energy object attenuation projection map; performing non-uniform response correction on the multi-energy object attenuation projection map based on a nonlinear correction table to obtain a corrected multi-energy object attenuation projection map. Therefore, the present invention can use different correction phantoms according to different imaging objects to achieve multi-imaging scene correction, and achieve a better non-uniform response correction effect. Therefore, the present invention can effectively correct the response non-uniformity between detector pixels, and can adapt to different imaging scenes at the same time. The method is simple and easy to implement, and can be easily integrated into the existing photon counting CT system.

[0049] The 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 accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0050] Photon counting detectors have serious non-uniform response, which is manifested in that the number of photons output by different detector units under the same X-ray incident spectrum is different, and the projection values ​​calculated after air correction are also different. This non-uniformity is related to the shape of the input X-ray spectrum, that is, the degree of non-uniformity of the projection images collected by different imaging objects is also different. Using a combination of multiple known material phantoms to simulate the composition of the object to be imaged as much as possible and constructing a suitable nonlinear response model is expected to solve the problem of non-uniform response of photon counting CT.

[0051] like Figure 1 As shown, the photon counting CT non-uniform response correction method proposed in this embodiment includes:

[0052] S1. Capture images of the object to be imaged by photon counting CT to obtain a multi-energy object projection image.

[0053] In this embodiment, the multi-energy object projection map refers to the photon number distribution map of the object to be imaged collected by the photon-counting CT at multiple different energy thresholds in multiple energy windows. Among them, the energy window refers to the energy interval composed of multiple energy thresholds. For example, in a photon-counting CT with two energy thresholds, assuming the energy thresholds are set as TH1 and TH2 respectively, a total of three energy intervals can be formed: (TH1, TH2), (TH1, +∞), and (TH2, +∞).

[0054] Furthermore, the number of multiple energy windows can be two or more, which is not limited here and can be determined according to actual needs.

[0055] S2. Use the pre-collected multi-energy air projection to perform air correction on the multi-energy object projection map to obtain the air-corrected multi-energy object attenuation projection map.

[0056] In this embodiment, the multi-energy air projection refers to the air projection collected under the same imaging protocol as the above multi-energy object projection map, that is, the same system imaging parameter settings. Among them, the air projection means that no object to be imaged is placed in the scanning area, and only X-rays pass through the air.

[0057] In this embodiment, the formula for performing air correction on the multi-energy object projection map pixel by pixel to obtain the air-corrected multi-energy object attenuation projection map is as follows:

[0058]

[0059] Among them, is the size of the object projection photons in the i-th energy window under a certain pixel of the multi-energy object projection map, is the size of the air projection photons in the i-th energy window under the corresponding pixel of the multi-energy air projection, and P i is the size of the projection value under the corresponding pixel of the air-corrected multi-energy object attenuation projection map. Among them, the projection map in this embodiment refers to a two-dimensional picture, and the pixel-by-pixel operation is for calculating the projection value of a single pixel. After the calculation is completed, the projection map is finally formed.

[0060] S3. Perform non-uniformity response correction on the multi-energy object attenuation projection map based on the non-linear correction table generated by pre-calibration to obtain the corrected multi-energy object attenuation projection map.

[0061] In this embodiment, performing non-uniformity response correction on the multi-energy object attenuation projection map based on the non-linear correction table generated by pre-calibration to obtain the corrected multi-energy object attenuation projection map, the specific implementation process is as follows:

[0062] S31. Calibrate through the acquisition of multiple material flat phantoms to obtain non-linear correction coefficients. The structure is simple and the projection values of the acquisitions are smooth. Therefore, the ideal projection value, that is, P, can be obtained by fitting the pixel spatial coordinatesideal , which is used to generate a non-linear correction table.

[0063] In this embodiment, as Figure 2 shown, the non-linear correction table is obtained by collecting data from a multi-material flat phantom and calculating non-linear model parameters. The specific process is as follows:

[0064] 1) Design a multi-material flat phantom to simulate the attenuation of different objects to be imaged by X-rays, and perform combined data collection on the flat phantom to obtain the multi-energy projection images of the phantom under different combinations. Among them, the flat phantom refers to a flat material or a flat container phantom with a uniform thickness, and data collection refers to the data collection process when the photon-counting CT system is in a non-rotating stationary state and the X-ray vertically passes through the flat phantom.

[0065] In this embodiment, as Figure 3 shown, the area of the multi-material flat phantom should be large enough to cover all the effective detection areas of the photon-counting detector.

[0066] Furthermore, as Figure 4 shown, the materials used for the multi-material flat phantom can be one or more. The flat phantom can be selected as a PMMA flat plate, an aluminum flat plate, an iodine solution flat plate, a calcium solution flat plate, etc. The multi-material flat phantom can design different thickness flat plates or different concentration solution flat plates according to the actual imaging scenario. For example: the multi-material flat phantom can also be designed in a stepped shape, as Figure 5 shown.

[0067] Furthermore, the combined data collection of the flat phantom can perform different material combinations on the above multi-material flat phantom according to the actual imaging scenario. For example: for the soft tissue imaging scenario, only the PMMA flat phantom with similar attenuation can be used; for the imaging scenario containing bone tissue, the combination of the PMMA flat plate and the aluminum flat plate or the calcium solution flat plate can be used; for the imaging scenario with iodine contrast agent injection, an iodine solution flat plate can be added for further combined data collection.

[0068] Furthermore, the combined data collection of the flat phantom can select data collection of a single material with different thickness flat phantoms or a single material with different concentration solution flat phantoms, or can also select combined data collection of multiple materials. The combined data collection of multiple materials can select two materials or three or more materials, as Figure 6 shown. The combined multiple materials can be selected as PMMA flat plate + AL flat plate, PMMA flat plate + iodine solution flat plate, PMMA flat plate + AL flat plate + iodine solution flat plate, etc.

[0069] In this embodiment, the multi-energy projection images of the phantom can be obtained by collecting multiple frames of projections and taking the average to reduce the interference of noise.

[0070] 2) Use multi - energy air projection under the same protocol to perform air correction on the multi - energy projection images of the phantom to obtain the multi - energy attenuation projection images of the phantom under different combinations, and traverse all combinations to obtain the multi - energy attenuation projection images of the phantom under all combinations.

[0071] In this embodiment, traversing all combinations means completing the acquisition count for all preset combinations.

[0072] 3) Calculate the ideal attenuation projection images of the multi - energy attenuation projection images of the phantom under all combinations.

[0073] In this embodiment, as Figure 7 shown in the schematic diagram of the photon - counting detector pixel index, which represents the pixel space coordinate relationship of the multi - energy attenuation projection of the phantom. Calculating the ideal attenuation projection image means obtaining it by fitting a non - linear equation using the pixel space coordinate relationship of the multi - energy attenuation projection of the phantom.

[0074] Furthermore, the non - linear equation can be selected as a quadratic equation, and the calculation formula is as follows:

[0075]

[0076] where m and n respectively represent the horizontal and vertical coordinates of the detector pixels, represents the ideal attenuation projection value of the (m, n) - th pixel under the i - th energy window, and a i represents the calculation coefficient of the ideal attenuation projection fitting under the i - th energy window.

[0077] Substitute the above - mentioned multi - energy attenuation projection value of the phantom to replace and fit out the ideal attenuation projection calculation coefficient a i , and then the corresponding ideal attenuation projection value of the phantom can be calculated according to the detector pixel coordinates Among them, the method for fitting out the ideal attenuation projection calculation coefficient a i can select the least - squares fitting or the multiple linear regression method. For example: the regress function in MATLAB can be used to solve such problems, which will not be elaborated here.

[0078] 4) Fit the non - linear polynomial model pixel - by - pixel and calculate the non - linear correction table for each pixel.

[0079] In this embodiment, the calculation method of the non - linear correction table is to use the non - linear polynomial model to fit the ideal attenuation projection and the actual attenuation projection pixel - by - pixel, calculate the non - linear correction coefficient under each energy window and finally generate the non - linear correction table. Among them, the non - linear correction coefficient under each energy window is fitted out The methods used can be least squares fitting or multiple linear regression methods. For example, the regress function in MATLAB can be used to solve such problems, which will not be elaborated here.

[0080] Furthermore, a non-linear polynomial model is used to fit the non-linear relationship between the actual multi-energy attenuation projection and the ideal multi-energy attenuation projection. The non-linear polynomial model can adopt a first-order polynomial model, a second-order polynomial model or a third-order polynomial model, which is not limited here. When the non-linear polynomial model adopts a second-order polynomial model, its calculation formula is as follows:

[0081]

[0082] Among them, represents the ideal attenuation projection value of the (m,n)th pixel under the ith energy window, and represent the phantom attenuation projections under the selected energy windows base1 and base2 as the basis of the non-linear model, represents the non-linear correction coefficient for fitting the ideal attenuation projection of the pixel (m,n) corresponding to the ith energy window Among them, the number of bases of the non-linear model selected can be 2 or more, and should include the attenuation projection under the energy window to be fitted. Among them, the detector coordinate indices of all pixels and their corresponding non-linear correction coefficients constitute the non-linear correction table.

[0083] S32. Since the shapes and compositions of the objects to be imaged are diverse and there are problems of non-uniform response, the non-linear correction table is used to correct the attenuation projection map of the actual object to be imaged, and the corrected object attenuation projection map, that is, P corr .

[0084] In this embodiment, the above non-linear correction table is used for all pixels, and the non-linear correction coefficient of the pixel is obtained according to its coordinate index After non-uniformity response correction, the corrected multi-energy object attenuation projection map is obtained. When performing non-uniformity response correction on the multi-energy object attenuation projection map, the non-linear polynomial model used needs to be consistent with the non-linear polynomial model used when generating the above non-linear correction table. The non-uniformity response correction model used for non-uniformity response correction can adopt a first-order polynomial model, a second-order polynomial model or a third-order polynomial model. Among them, correspondingly, when the non-uniformity response correction model adopts a second-order polynomial model, its calculation formula is as follows:

[0085]

[0086] Among them, is the non-linear correction coefficient of the pixel (m,n) corresponding to the ith energy window, It is the object attenuation projection map after the i-th energy window correction for the pixel (m,n).

[0087] As Figure 8 Shown is the comparison effect diagram of the non-uniformity response correction of the flat phantom attenuation projection map before and after. It can be seen that there is serious non-uniformity in the attenuation projection map before correction. There are large differences in the attenuation projection values between detector modules and between pixels. After correction by the correction method of the present invention, it can be seen that the uniformity of the flat phantom attenuation projection map is greatly improved.

[0088] Embodiment 2: The above Embodiment 1 provides a method for non-uniformity response correction of photon-counting CT. Correspondingly, this embodiment provides a device for non-uniformity response correction of photon-counting CT. The device provided in this embodiment can implement the method for non-uniformity response correction of photon-counting CT in Embodiment 1, and this device can be implemented in a software, hardware, or a combination of software and hardware 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, this device may include integrated or separate functional modules or functional units to execute the corresponding steps in the methods 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 non-uniformity response correction of photon-counting CT provided by the present invention is only illustrative.

[0089] Specifically, this embodiment also provides a device for non-uniformity response correction of photon-counting CT, and this device includes:

[0090] An image acquisition unit, configured to acquire an image of an object to be imaged through a photon-counting CT to obtain a multi-energy object projection map;

[0091] An air correction unit, configured to perform air correction on the multi-energy object projection map to obtain an air-corrected multi-energy object attenuation projection map;

[0092] A non-uniformity response correction unit, configured to perform non-uniformity response correction on the multi-energy object attenuation projection map based on a non-linear correction table to obtain a corrected multi-energy object attenuation projection map.

[0093] Embodiment 3: This embodiment provides an electronic device corresponding to the method for non-uniformity response correction of photon-counting CT 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.

[0094] As Figure 9As 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 effects are similar to those of Embodiment 1 and will not be elaborated here. Those skilled in the art can understand that Figure 9 The structure shown in is only a block diagram of some structures related to the solution of this application, and does not constitute a limitation on the computing device to which the solution of this application is applied. The specific computing device may include more or fewer components than those shown in the figure, or combine some components, or have a different component layout.

[0095] In a preferred embodiment, when the logical instructions in the above-mentioned memory can be implemented in the form of software functional units and sold or used as an independent product, they can be stored in a computer-readable storage medium. Based on this 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 memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), and optical discs that can store program codes.

[0096] In a preferred embodiment, the processor can be a general-purpose processor of various types such as a central processing unit (CPU) and a digital signal processor (DSP), which is not limited here.

[0097] Embodiment 4: This embodiment provides a computer-readable storage medium storing one or more programs. The one or more programs include computer instructions. When the computer instructions are executed by the computer, the computer is caused to execute the method provided in the above-mentioned Embodiment 1.

[0098] 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 that cause the computer to execute the method provided in the above-mentioned Embodiment 1.

[0099] This application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (devices), and computer program products according to embodiments of the present 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, such 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 one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or a device for implementing the functions specified in one or more of the blocks.

[0100] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device that implements the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or a device for implementing the functions specified in one or more of the blocks.

[0101] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or a device for implementing the functions specified in one or more of the blocks.

[0102] Each embodiment in this specification is described in a progressive manner. The same or similar parts among the embodiments can be referred to each other, and the differences between each embodiment and other embodiments are emphasized. In the description of this specification, the descriptions referring to terms such as "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 expressions 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.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended 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 described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for correcting non-uniformity response of photon counting CT, characterized in that, Including: Performing image acquisition on an object to be imaged by photon counting CT to obtain a multi-energy object projection map; Performing air correction on the multi-energy object projection map to obtain a multi-energy object attenuation projection map after air correction; Performing non-uniformity response correction on the multi-energy object attenuation projection map based on a non-linear correction table to obtain a corrected multi-energy object attenuation projection map.

2. The photon counting CT non-uniformity response correction method according to claim 1, wherein The multi-energy object projection map refers to a photon number distribution map of the object to be imaged under multiple energy windows collected by photon counting CT at multiple different energy thresholds, where the energy window refers to an energy interval composed of multiple energy thresholds.

3. The photon counting CT non-uniformity response correction method according to claim 2, wherein The calculation formula for performing air correction on the multi-energy object projection map to obtain a multi-energy object attenuation projection map after air correction is: Among them, is the magnitude of the number of object projection photons in the i-th energy window of a certain pixel in the multi-energy object projection image, is the magnitude of the number of air projection photons in the i-th energy window corresponding to the pixel of the multi-energy air projection, and P i is the projection value of the corresponding pixel in the multi-energy object attenuation projection image after air correction.

4. The photon counting CT non-uniformity response correction method according to claim 2, characterized in that The generation process of the non-linear correction table includes: Designing multiple material flat phantoms, and performing combined data acquisition on the flat phantoms to obtain multi-energy projection maps of the phantoms under different combinations; Performing air correction on the multi-energy projection maps of the phantoms to obtain multi-energy attenuation projection maps of the phantoms under different combinations, and traversing all combinations to obtain multi-energy attenuation projection maps of the phantoms under all combinations; Calculating the ideal attenuation projection maps of the multi-energy attenuation projection maps of the phantoms under all combinations; Based on the ideal attenuation projection maps, performing non-linear polynomial model fitting pixel by pixel to calculate the non-linear correction table for each pixel.

5. The photon counting CT non-uniformity response correction method according to claim 4, wherein Calculating the ideal attenuation projection maps of the multi-energy attenuation projection maps of the phantoms under all combinations is obtained by fitting a non-linear equation using the spatial coordinate relationship of the multi-energy attenuation projection map pixels of the phantoms. The non-linear equation selects a quadratic equation, and the calculation formula is: where m and n represent the horizontal and vertical coordinates of the detector pixels respectively, represents the ideal attenuation projection value of the (m, n)th pixel under the ith energy window, a i represents the calculation coefficient of the ideal attenuation projection fitted under the ith energy window.

6. The photon counting CT non-uniformity response correction method according to claim 4, wherein The generation of the non-linear correction table is achieved by fitting the ideal attenuation projection and the actual attenuation projection pixel by pixel using a non-linear polynomial model, and calculating the non-linear correction coefficients under each energy window. Finally, a non-linear correction table is generated. Among them, the non-linear polynomial model adopts a first-order polynomial model, a second-order polynomial model or a third-order polynomial model. When performing non-uniformity response correction on the attenuation projection map of a multi-energy object, the non-linear polynomial model used needs to be consistent with the non-linear polynomial model used in the generation of the above non-linear correction table.

7. The photon counting CT non-uniformity response correction method according to claim 4, characterized in that, The flat phantom selects a PMMA flat phantom, an aluminum flat phantom, an iodine-containing solution flat phantom or a calcium-containing solution flat phantom; the combined data acquisition of the flat phantom selects data acquisition of single-material flat phantoms with different thicknesses, data acquisition of single-material flat phantoms with different concentrations of solutions, or selects combined data acquisition of multiple materials; the area of the flat phantom should be large enough to cover all effective detection areas of the photon counting detector.

8. A photon counting CT non-uniformity response correction device, characterized in that The device includes: An image acquisition unit configured to perform image acquisition on an object to be imaged by photon counting CT to obtain a multi-energy object projection map; An air correction unit configured to perform air correction on the multi-energy object projection map to obtain a multi-energy object attenuation projection map after air correction; A non-uniformity response correction unit configured to perform non-uniformity response correction on the multi-energy object attenuation projection map based on a non-linear correction table to obtain a corrected multi-energy object attenuation projection map.

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.

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