Dual-energy CT material decomposition method, device, system, electronic equipment and storage medium

Abstract

The present application relates to the field of medical imaging technology, and in particular to a dual-energy CT material decomposition method, device, system, electronic device and storage medium, wherein the method comprises: obtaining a high-energy projection higher than an X-ray energy threshold and a low-energy projection lower than an X-ray energy threshold of a target to be measured during CT scanning; performing material decomposition of the projection domain according to the high-energy projection and the low-energy projection, and generating a high-energy virtual monoenergetic projection and a low-energy virtual monoenergetic projection while obtaining a preliminary decomposition result of the target to be measured; correcting the decomposition error of the low-energy virtual monoenergetic projection to obtain a corrected low-energy virtual monoenergetic projection, and using the corrected low-energy virtual monoenergetic projection and the high-energy virtual monoenergetic projection to correct the preliminary decomposition result to obtain the final decomposition result of the target to be measured. Therefore, the embodiments of the present application can effectively reduce the influence of material decomposition error, suppress artifacts caused by decomposition error, effectively correct the error of conventional dual-energy material decomposition, and improve the accuracy of material decomposition.

Description

Technical Field

[0001] The present application relates to the field of medical imaging technology, and in particular to a dual-energy CT (Computed Tomography) material decomposition method, device, system, electronic equipment and storage medium. Background Art

[0002] Computed tomography (CT) technology has been widely used in medical imaging and plays an important role in medical diagnosis. The CT imaging system uses the attenuation characteristics of X-rays to reconstruct the internal structure of an object by scanning the object at multiple angles. However, according to the principle of CT imaging, the reconstruction result of a certain position of an object reflects the linear attenuation coefficient of that point. Different materials with different densities may have the same or similar attenuation coefficients at a certain energy, which brings difficulties to the material identification and disease diagnosis of CT imaging; in addition, because the photon energy of the X-ray source is a continuous spectrum and the attenuation ability of the material is different at different X-ray energies, when the average energy of the X-ray passes through the object, it will increase, which will cause hardening artifacts in the reconstructed image, making the diagnosis of low-contrast soft tissue lesions more difficult. Hardening correction is divided into hardware-based and software-based methods. Among them, the hardware-based method has limited effect in clinical applications; the software-based method can achieve hardening correction of uniform materials through water correction, but for CT images in medicine, water correction cannot significantly suppress the hardening effect of bones. However, due to the obvious distribution characteristics of bones, the bone distribution of the image can be extracted as prior information through pre-reconstruction to achieve hardening correction of multiple materials.

[0003] Dual-energy or multi-energy CT imaging is one of the current research hotspots in the field of CT and has been applied to actual medical imaging. Dual-energy CT refers to the use of two energy spectra to scan objects separately to achieve effective distinction between different materials; multi-energy CT uses the correlation between material attenuation coefficient and X-ray energy to provide more information than conventional CT. Therefore, compared with traditional CT, multi-energy CT can suppress hardening artifacts, improve tissue contrast, improve image quality, and reduce radiation dose, and has many advantages. The current mainstream dual-energy CT system includes technologies such as dual-source dual-detection, fast kilovolt switching, and double-layer detectors. These technologies have their own advantages and disadvantages, and have been commercialized. With the development of flat-panel detector technology, cone beam CT (CBCT, Cone beam Computer Tomography) based on large-area flat-panel detectors has been increasingly used in clinical practices such as diagnostic imaging and interventional imaging, such as oral examination, image guidance in surgery and radiotherapy, etc. This technology has the advantages of high detector integration, high spatial resolution, low radiation dose, and convenient and flexible scanning. However, due to the scattering and cone-angle artifacts caused by large-area scanning, the image quality of CBCT is currently weaker than that of multi-detector CT (MDCT), which also limits its application in diagnostic imaging. However, dual-energy CBCT based on a double-layer flat-panel detector provides the possibility for further improvement of imaging performance: this dual-energy CT technology can achieve homologous, simultaneous, and isotropic imaging in principle, and there is no problem of temporal and spatial mismatch of dual-energy projection data, so it can achieve material decomposition in the projection domain. This decomposition method makes full use of energy spectrum information and can theoretically completely eliminate the influence of hardening artifacts.

[0004] However, the dual-energy CT technology also faces some inherent shortcomings, mainly reflected in the low energy separation and low signal level of high-energy projection data. The commonly used method for material decomposition in the projection domain is polynomial fitting. For cranial imaging, water and bone can be selected as the decomposition base materials, and the high and low energy projections can be decomposed into water and bone projection images. Then, the attenuation coefficients of the two base materials at a specific energy are used as weights to make a weighted addition of the two, which can generate a virtual monoenergetic projection at that energy, and reconstruct a virtual monoenergetic image. However, due to the strong attenuation of X-rays by the first-layer detector, when the ray path passes through thicker bones, the signal level of the high-energy projection data is lower, resulting in excessive noise, which seriously affects the accuracy of material decomposition. When generating virtual monoenergetic projections, the decomposition error in the decomposition result is transmitted to the virtual monoenergetic projection to cause projection errors, which makes it easy for striped artifacts to appear in the reconstructed decomposition image and virtual monoenergetic image. Summary of the invention

[0005] The present application provides a dual-energy CT material decomposition method, device, system, electronic device and storage medium, which can effectively reduce the impact of material decomposition errors, suppress artifacts caused by decomposition errors, effectively correct the errors of conventional dual-energy material decomposition, and improve the accuracy of material decomposition.

[0006] A first aspect of the present application provides a dual-energy CT material decomposition method, comprising the following steps: obtaining a high-energy projection of a target to be measured whose average energy of equivalent energy spectrum is higher than a preset value and a low-energy projection of whose average energy of equivalent energy spectrum is lower than the preset value during CT scanning; performing material decomposition in a projection domain according to the high-energy projection and the low-energy projection, and generating a high-energy virtual monoenergetic projection and a low-energy virtual monoenergetic projection while obtaining a preliminary decomposition result of the target to be measured; correcting the projection error of the low-energy virtual monoenergetic projection to obtain a corrected low-energy virtual monoenergetic projection, and using the corrected low-energy virtual monoenergetic projection and the high-energy virtual monoenergetic projection to correct the decomposition error of the preliminary decomposition result to obtain a final decomposition result of the target to be measured.

[0007] Optionally, correcting the projection error of the low-energy virtual monoenergetic projection to obtain a corrected low-energy virtual monoenergetic projection includes: weighting the high-energy projection and the low-energy projection to obtain a total projection under the full energy spectrum; and using the total projection under the full energy spectrum to correct the projection error of the low-energy virtual monoenergetic projection to obtain the corrected low-energy virtual monoenergetic projection.

[0008] Optionally, before correcting the projection error of the low-energy virtual monoenergetic projection by using the total projection under the full energy spectrum, the method further includes: correcting the multi-material energy spectrum hardening error of the total projection under the full energy spectrum to obtain the total projection after energy spectrum correction.

[0009] Optionally, the method of using the total projection under the full energy spectrum to correct the projection error of the low-energy virtual monoenergetic projection to obtain the corrected low-energy virtual monoenergetic projection includes: acquiring the counting level of the high-energy projection; matching the respective weights of the total projection after energy spectrum correction and the low-energy virtual monoenergetic projection according to the counting level, and obtaining the corrected low-energy virtual monoenergetic projection after weighting.

[0010] Optionally, the correction of the multi-material energy spectrum hardening error of the total projection under the full energy spectrum to obtain the total projection after energy spectrum correction includes: reconstructing the bones of the target to be measured based on the total projection under the full energy spectrum to obtain a pre-reconstructed image; performing threshold segmentation on the pre-reconstructed image to obtain the bone distribution of the target to be measured, and obtaining a bone projection through forward projection; calculating the hardening error in the total projection according to the bone projection and the total projection, and correcting the energy spectrum error of the total projection based on the hardening error to obtain the total projection after energy spectrum correction.

[0011] Optionally, the material decomposition of the projection domain is performed according to the high-energy projection and the low-energy projection to obtain a preliminary decomposition result of the target to be measured, and a high-energy virtual monoenergetic projection and a low-energy virtual monoenergetic projection are generated, including: decomposing water and bones in the high-energy projection and the low-energy projection to obtain a water projection and a bone projection of the target to be measured; reconstructing a water image of the target to be measured according to the water projection, and reconstructing a bone image of the target to be measured according to the bone projection; matching the weights of the water projection and the bone projection at different energies according to the attenuation coefficients of water and bones at different energies, and weighting the water projection and the bone projection at different energies to obtain the high-energy virtual monoenergetic projection and the low-energy virtual monoenergetic projection.

[0012] A second aspect of the present application provides a dual-energy CT material decomposition device, comprising: an acquisition module, used to acquire a high-energy projection of a target to be measured whose average energy of equivalent energy spectrum is higher than a preset value and a low-energy projection of whose average energy of equivalent energy spectrum is lower than the preset value during CT scanning; a decomposition module, used to perform material decomposition in a projection domain according to the high-energy projection and the low-energy projection, and generate a high-energy virtual monoenergetic projection and a low-energy virtual monoenergetic projection while obtaining a preliminary decomposition result of the target to be measured; a correction module, used to correct the projection error of the low-energy virtual monoenergetic projection, obtain a corrected low-energy virtual monoenergetic projection, and use the corrected low-energy virtual monoenergetic projection and the high-energy virtual monoenergetic projection to correct the decomposition error of the preliminary decomposition result, and obtain a final decomposition result of the target to be measured.

[0013] Optionally, the correction module is further used to: weight the high-energy projection and the low-energy projection to obtain a total projection under the full energy spectrum; use the total projection under the full energy spectrum to correct the projection error of the low-energy virtual monoenergetic projection to obtain the corrected low-energy virtual monoenergetic projection.

[0014] Optionally, the correction module is further used to: correct the multi-material energy spectrum hardening error of the total projection under the full energy spectrum to obtain the total projection after energy spectrum correction.

[0015] Optionally, the correction module is further used to: obtain the counting level of the high-energy projection; match the respective weights of the total projection after energy spectrum correction and the low-energy virtual monoenergetic projection according to the counting level, and obtain the corrected low-energy virtual monoenergetic projection after weighting.

[0016] Optionally, the correction module is further used to: reconstruct the bones of the target to be measured based on the total projection under the full energy spectrum to obtain a pre-reconstructed image; perform threshold segmentation on the pre-reconstructed image to obtain the bone distribution of the target to be measured, and obtain the bone projection through forward projection; calculate the hardening error in the total projection based on the bone projection and the total projection, correct the energy spectrum error of the total projection based on the hardening error, and obtain the total projection after energy spectrum correction.

[0017] Optionally, the decomposition module is further used to: decompose water and bones in the high-energy projection and the low-energy projection to obtain the water projection and bone projection of the target to be measured; reconstruct the water image of the target to be measured based on the water projection, and reconstruct the bone image of the target to be measured based on the bone projection; match the weights of the water projection and the bone projection at different energies according to the attenuation coefficients of water and bones at different energies, and weight the water projection and the bone projection at different energies to obtain the high-energy virtual monoenergetic projection and the low-energy virtual monoenergetic projection.

[0018] In a third aspect, an embodiment of the present application provides a dual-energy CT material decomposition system, comprising: an X-ray source, used to emit X-rays during CT scanning; a double-layer flat-panel detector, used to collect high-energy projections whose average energy of equivalent energy spectrum is higher than a preset value and low-energy projections whose average energy of equivalent energy spectrum is lower than the preset value during CT scanning; and a dual-energy CT material decomposition device as described in the above embodiment, used to obtain a final decomposition result of the target to be measured based on the high-energy projection and the low-energy projection.

[0019] Optionally, the double-layer flat-panel detector is formed by a first detector and a second detector stacked in parallel, wherein the first detector is used to absorb low-energy X-ray photons whose average energy of an equivalent energy spectrum is lower than a preset value to obtain the low-energy projection, and the second detector is used to absorb high-energy X-ray photons whose average energy of an equivalent energy spectrum is higher than a preset value to obtain the high-energy projection.

[0020] A fourth aspect of the present application provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the dual-energy CT material decomposition method as described in the above embodiments.

[0021] A fifth aspect of the present application provides a computer-readable storage medium having a computer program stored thereon, the program being executed by a processor to implement the dual-energy CT material decomposition method as described in the above embodiment.

[0022] Therefore, this application has at least the following beneficial effects:

[0023] At the projection points where the signal level is too low, the results of multi-material energy spectrum correction can be used to replace the results of material decomposition to reduce the decomposition error and eliminate streak artifacts. The virtual monoenergetic projection that eliminates the streak artifacts can be combined with the higher energy virtual monoenergetic projection generated by material decomposition to obtain a more accurate decomposition result, thereby effectively reducing the impact of the material decomposition error and suppressing the artifacts caused by the decomposition error. The errors of conventional dual-energy material decomposition can be effectively corrected, and the accuracy of material decomposition can be improved.

[0024] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0026] Figure 1 A flow chart of a dual-energy CT material decomposition method provided according to an embodiment of the present application;

[0027] Figure 2 This is an example diagram of a dual-energy CT imaging system based on a double-layer flat panel detector provided according to an embodiment of the present application;

[0028] Figure 3 A simplified structural schematic diagram of a double-layer flat-panel detector provided according to an embodiment of the present application;

[0029] Figure 4 A dual-energy material decomposition flow chart provided according to an embodiment of the present application;

[0030] Figure 5 Flow chart for multi-matter spectrum correction;

[0031] Figure 6 It is the result of dual energy reconstruction and material decomposition;

[0032] Figure 7 This is an exemplary diagram of a dual-energy CT material decomposition device according to an embodiment of the present application;

[0033] Figure 8 is an exemplary diagram of a dual-energy CT material decomposition system according to an embodiment of the present application;

[0034] Fig. 9 Schematic diagram of the structure of an electronic device according to an embodiment of the present application.

[0035] Description of reference numerals: Figure 2 In the figure, the rotating arrow indicates that the X-ray source and detector rotate around the object during X-ray tomography. Figure 6In the figure, Figure (a) (e) is the monoenergetic reconstruction results of low-energy and high-energy projections; Figure (b) (c) (d) is the water, bone and virtual monoenergetic images obtained by conventional material decomposition; Figure (f) (g) (h) is the water, bone and virtual monoenergetic images obtained by the dual-energy CT material decomposition method proposed in the embodiment of the present application. DETAILED DESCRIPTION

[0036] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0037] The following describes the dual-energy CT material decomposition method, device, electronic device and storage medium of the embodiment of the present application with reference to the accompanying drawings. In view of the problems mentioned in the above background technology, the present application provides a dual-energy CT material decomposition method, specifically, Figure 1 A schematic flow chart of a dual-energy CT material decomposition method provided in an embodiment of the present application is shown in FIG. Figure 1 As shown, the dual-energy CT material decomposition method includes the following steps:

[0038] In step S101, a high-energy projection whose equivalent energy spectrum average energy is higher than a preset value and a low-energy projection whose equivalent energy spectrum average energy is lower than a preset value are obtained during CT scanning of the target to be measured.

[0039] Among them, the equivalent energy spectrum and average energy of X-rays during CT scanning can be used to identify the high and low energy of X-rays; the preset value of the average energy of the equivalent energy spectrum can be specifically calibrated or set according to actual conditions, and no specific limitation is made to this.

[0040] It is understandable that the embodiments of the present application can use a variety of methods to collect high-energy projections and low-energy projections, which are not specifically limited. For example, the embodiments of the present application can use the following methods: Figure 2 The double-layer flat panel detector in the dual-energy CT material decomposition system shown collects high and low energy data, as follows:

[0041] The dual-energy CT material decomposition system uses a double-layer flat-panel detector to achieve simultaneous acquisition of high- and low-energy data. The only difference from the traditional cone-beam CT system is the detector. The scanning processes of the two are exactly the same, and no additional system design and scanning protocol are required.

[0042] The simplified structure of the double-layer flat-panel detector can be Figure 3As shown, a double-layer flat-panel detector can be formed by stacking two detectors in parallel. The upper and lower layers of detectors mainly absorb low-energy and high-energy X-ray photons respectively, thereby achieving one-time acquisition of high and low-energy data. There are many designs for double-layer flat-panel detectors. For example, for energy deposition detectors composed of CsI scintillators, in order to ensure a certain degree of energy spectrum separation, a thicker top detector design can be selected, or a thinner top detector plus a middle filter, such as 1mm Cu, to achieve energy separation. It should be noted that in actual operation, while improving energy separation, it generally brings a certain amount of high-energy photon loss, which will further reduce the signal level of high-energy data. Therefore, different factors must be weighed in the actual design process.

[0043] Assuming the energy spectrum of X-rays is S(E), the high and low energy projections obtained by the detector can be expressed as:

[0044]

[0045]

[0046] in, and Respectively represent the detector responses of the two layers of detectors; μ T , D T , μ B , D B Respectively represent the linear attenuation coefficient and thickness of the upper and lower layers of the detector. S(E)·η T (E) and Represent the equivalent energy spectra of the upper and lower detectors respectively. If a filter is inserted between the two detectors, then The item should be changed to Among them, μ F , L FL represent the linear attenuation coefficient and thickness of the interlayer filter respectively.

[0047] In step S102, material decomposition of the projection domain is performed according to the high-energy projection and the low-energy projection, and a preliminary decomposition result of the target to be measured is obtained, and a high-energy virtual monoenergetic projection and a low-energy virtual monoenergetic projection are generated.

[0048] It can be understood that the embodiments of the present application use high and low energy projections to perform projection domain material decomposition, obtain preliminary material decomposition results, and generate a virtual monoenergetic projection at high energy and a suitable low energy virtual monoenergetic projection. The specific energy is related to the system energy spectrum, see the following embodiments.

[0049] The material decomposition process can be as follows Figure 4As shown, the spatially matched high and low energy projection data can be used in a variety of ways, which are not specifically limited; for example, the embodiment of the present application can be obtained by polynomial fitting, and the analytical method of polynomial fitting can decompose the high and low energy projections into projections of two base materials, and the decomposition formula can be:

[0050]

[0051]

[0052] Among them, the higher energy generated by linear weighted addition in the embodiment of the present application can be represented by E1, and its corresponding virtual monoenergetic projection can be The lower energy can be represented by E2, and its corresponding virtual monoenergetic projection can be

[0053] It should be noted that in medical CT scanning, the tomographic structure of the scanned object is mainly bones and various human tissues, among which the linear attenuation coefficient of human tissue is approximately the same as that of water. Therefore, the embodiment of the present application can decompose the water and bones in the high-energy projection and the low-energy projection, and perform relevant calculations using the relevant data of the water and bones of the target to be measured.

[0054] In an embodiment of the present application, material decomposition of the projection domain is performed according to the high-energy projection and the low-energy projection, and a preliminary decomposition result of the target to be measured is obtained, and a high-energy virtual monoenergetic projection and a low-energy virtual monoenergetic projection are generated, including: decomposing water and bones in the high-energy projection and the low-energy projection to obtain a water projection and a bone projection of the target to be measured; reconstructing a water image of the target to be measured according to the water projection, and reconstructing a bone image of the target to be measured according to the bone projection; matching the weights of the water projection and the bone projection at different energies according to the attenuation coefficients of water and bones at different energies, and weighting the water projection and the bone projection at different energies to obtain a high-energy virtual monoenergetic projection and a low-energy virtual monoenergetic projection.

[0055] It can be understood that the embodiments of the present application can decompose the base material substances in the projection domain of the high and low energy projections. With water and bones as the base materials, the high and low energy projections can be decomposed into projections of only water and bones. The two can be reconstructed separately to obtain reconstructed images of water and bones. The attenuation coefficients of water and bones at different energies are used as weights, and the weighted addition of the two base material reconstructed images is performed to generate virtual monoenergetic images at different energies.

[0056] Specifically, if Figure 5 As shown, the projection of the base material is obtained by conventional projection domain material decomposition, and then a virtual monoenergetic projection at a higher energy E1 is generated by linear weighted addition. and virtual monoenergetic projection at lower effective energy E2 Among them, the material decomposition of the projection domain can be achieved by using the spatially matched high and low energy projection data. The commonly used analytical method is polynomial fitting, which decomposes the high and low energy projections into projections of two base materials, as shown in the following formula:

[0057]

[0058]

[0059] In step S103, the projection error of the low-energy virtual monoenergetic projection is corrected to obtain a corrected low-energy virtual monoenergetic projection, and the decomposition error of the preliminary decomposition result is corrected using the corrected low-energy virtual monoenergetic projection and the high-energy virtual monoenergetic projection to obtain a final decomposition result of the target to be measured.

[0060] It can be understood that the embodiments of the present application can correct the projection error in the low-energy virtual monoenergetic projection to obtain a corrected low-energy virtual monoenergetic projection. Since the virtual monoenergetic projection is a linear weighted combination of the material decomposition results, the projection error in the virtual monoenergetic projection comes from the decomposition error of the material decomposition, and the lower the energy, the greater the projection error. Based on this correlation, the embodiments of the present application can in turn achieve error correction of material decomposition by correcting the virtual monoenergetic projection; specifically, the embodiments of the present application can use the high-energy virtual monoenergetic projection and the corrected low-energy virtual monoenergetic projection to obtain the corrected material decomposition results, and reconstruct the reconstructed images of the base material water and bones and the virtual monoenergetic images at different energies.

[0061] In an embodiment of the present application, the projection error of the low-energy virtual monoenergetic projection is corrected to obtain a corrected low-energy virtual monoenergetic projection, including: weighting the high-energy projection and the low-energy projection to obtain a total projection under the full energy spectrum; using the total projection under the full energy spectrum to correct the projection error of the low-energy virtual monoenergetic projection to obtain a corrected low-energy virtual monoenergetic projection.

[0062] It can be understood that the embodiments of the present application can perform weighted addition of the collected high and low energy data to obtain a total projection under the full energy spectrum, and perform multi-matter energy spectrum correction on the projection to obtain a projection result after spectrum correction, and use the projection after multi-matter energy spectrum correction as a physical prior and combine it with the low-energy virtual monoenergetic projection to perform error correction to obtain a corrected low-energy virtual monoenergetic projection.

[0063] Specifically, due to the spatiotemporal consistency of high- and low-energy projection data, in addition to dual-energy imaging analysis, the embodiment of the present application can fuse the two layers of projection data for conventional image reconstruction to obtain a traditional single-energy image with lower noise. The specific fusion method can be selected as the weighted addition of high- and low-energy projection data, as shown in the following formula:

[0064] P T =ωP L +(1-ω)PH

[0065] It can be roughly proved that the weight λ of the low-energy projection data mainly depends on the incident energy spectrum. Therefore, under the same scanning conditions, the same weight λ can be used to scan different objects; the optimal value of the weight can be obtained by experimentally minimizing the image signal-to-noise ratio.

[0066] Therefore, before reconstructing the image described in the following embodiments, the embodiments of the present application can utilize the spatiotemporal consistency of the high and low energy projection data of the double-layer flat-panel detector, and can perform weighted addition of the high and low energy projection data to obtain a projection under the full energy spectrum, thereby obtaining a higher signal level and a reconstructed image with lower noise.

[0067] In an embodiment of the present application, before using the total projection under the full energy spectrum to correct the projection error of the low-energy virtual monoenergetic projection, it also includes: correcting the multi-material energy spectrum hardening error of the total projection under the full energy spectrum to obtain the total projection after energy spectrum correction. Specifically: reconstructing the bones of the target to be measured based on the total projection under the full energy spectrum to obtain a pre-reconstructed image; performing threshold segmentation on the pre-reconstructed image to obtain the bone distribution of the target to be measured, and obtaining the bone projection through forward projection; calculating the hardening error in the total projection based on the bone projection and the total projection, and correcting the energy spectrum error of the total projection based on the hardening error to obtain the total projection after energy spectrum correction.

[0068] It is understandable that the embodiment of the present application can be based on the traditional monoenergetic image reconstruction to obtain the pre-reconstructed image, use the threshold segmentation to obtain the bone distribution in the pre-reconstructed image, and then perform forward projection to obtain the bone projection data. The hardening error in the total projection can be calculated based on the relationship between the hardening error and the total projection and the bone projection. This relationship can be obtained by the empirical polynomial fitting method. The total projection is corrected by the calculated error, so as to reconstruct the monoenergetic image after the multi-matter energy spectrum correction.

[0069] Specifically, in medical CT scanning, the tomographic structure of the scanned object is mainly bones and various human tissues. The linear attenuation coefficient of human tissue is similar to that of water, but the linear attenuation coefficient of bone is quite different from that of water. The water correction achieved by simple polynomial fitting cannot significantly suppress the beam hardening effect of bone. Bones have very obvious distribution characteristics in the reconstructed image, so the separation of bones and soft tissues can be achieved through image pre-reconstruction and threshold segmentation. Forward projection of bones can obtain the projection distribution of bones as prior information to achieve multi-matter spectrum correction. According to the relationship between the hardening error and the projection of bones and the total projection, the hardening error can be calculated using nonlinear mapping, and added to the total projection to obtain the projection after multi-matter spectrum correction, as shown in the following formula:

[0070] P dMMSC =P t +f(P t ,Pb )

[0071] Among them, f(P t ,P b ) is the hardening error, which can be expressed as a function of the total projection and the bone projection. Finally, the reconstructed image after multi-matter spectrum correction can be generated by image reconstruction.

[0072] The flow chart of multi-substance spectrum correction can be as follows: Figure 5 As shown by the dotted arrow in the figure, in order to improve the accuracy of hardening correction, the projection after energy spectrum correction can be used as the input of pre-reconstruction and perform multiple iterative corrections.

[0073] In an embodiment of the present application, the projection error of the low-energy virtual monoenergetic projection is corrected using the total projection under the full energy spectrum to obtain the corrected low-energy virtual monoenergetic projection, including: obtaining the counting level of the high-energy projection; matching the respective weights of the total projection after energy spectrum correction and the low-energy virtual monoenergetic projection according to the counting level, and obtaining the corrected low-energy virtual monoenergetic projection after weighting.

[0074] It is understandable that, since material decomposition is sensitive to low signal noise, when the ray path passes through thicker bones, the signal attenuation is severe, resulting in a high noise level, which makes the error of the decomposition result too large, and produces stripe-like artifacts in the generated virtual monoenergetic image. Considering that the result after multi-material spectrum correction has no stripe artifacts, and at a certain energy, it is similar to the virtual monoenergetic projection of material decomposition, the projection corrected to the energy of the multi-material spectrum can be combined with the virtual monoenergetic projection to achieve decomposition error correction and completely eliminate hardening artifacts; the embodiment of the present application can be implemented by adaptive weighted addition of the projections of the two. When weighted addition, different dynamic weights are used at different projection data points, and the specific size of the weight depends on the original count of the high-energy data: the total weight is 1, the lower the count level, the greater the weight of the projection corrected by the multi-material spectrum, and the smaller the weight of the virtual monoenergetic projection generated by the material decomposition; the larger the count, the opposite is true. When the count is lower than a certain threshold, the weight of the projection corrected by the multi-material spectrum is set to 1, and when it is higher than a certain threshold, its weight is set to 0. This process is equivalent to replacing the result of virtual monoenergetic projection with the result of multi-matter energy spectrum correction at the projection point where the signal level is too low to obtain a smaller projection error, thereby eliminating fringe artifacts.

[0075] By combining the virtual monoenergetic projection obtained in the above embodiment with the virtual monoenergetic projection of higher energy generated by material decomposition, a more accurate decomposition result can be obtained. Moreover, the decomposition result can be improved through multiple iterations.

[0076] Specifically, due to the low signal level of high-energy projection and the low energy spectrum separation, large decomposition errors may occur, resulting in streaky artifacts in the reconstruction results, especially in the generated low-energy virtual monoenergetic images. Considering that at a certain effective energy, the projection after multi-material hardening correction and the virtual monoenergetic projection generated by material decomposition are the same, the projection after hardening correction can be used as a physical prior to guide the correction of material decomposition. Figure 4 As shown, the following steps are included:

[0077] The low-energy virtual monoenergetic projection and the multi-matter spectrum corrected projection are used as images for adaptive weighted image fusion to generate the error-corrected low-energy virtual monoenergetic projection, which can be shown as the following formula:

[0078]

[0079] Among them, λ is a weight factor that can be adaptively and dynamically adjusted according to the projection pixel value. The determination of λ can be calculated according to the following formula:

[0080]

[0081] Where I is the intensity signal measured by the detector, I h , I l is the selected high and low thresholds. This formula indicates that when the intensity signal measured by the detector is low, the noise is large and the material decomposition error is large. At this time, increasing the weight of the projection after multi-material energy spectrum correction can reduce the influence of material decomposition error, thereby achieving error correction and suppressing artifacts caused by decomposition error. Based on the high-energy virtual monoenergetic projection and the corrected low-energy virtual monoenergetic projection, the corrected base material decomposition result can be calculated according to the following formula. Further reconstruction can obtain reconstructed images of water and bones and virtual monoenergetic images at different energies.

[0082]

[0083] It should be noted that the embodiment of the present application performed a high-precision dual-energy CT scan of the skull model based on a laboratory platform. Figure 6 The comparison of reconstruction results of the conventional single-energy CT and the conventional dual-energy material decomposition method and the dual-energy material decomposition method proposed in the embodiment of the application is shown. The reliability and superiority of the method proposed in the embodiment of the application can be seen from the results.

[0084] The dual-energy CT material decomposition method of the present application embodiment will be described below through a specific embodiment, taking the high-precision dual-energy CT scanning of a skull model based on a laboratory platform as an example. Figure 6 As shown, the details are as follows:

[0085] S00: weighted addition of the collected high and low energy data is performed to obtain a total projection under the full energy spectrum, and multi-matter energy spectrum correction is performed on the projection to obtain a projection result after energy spectrum correction.

[0086] S01: Use high and low energy projections to perform material decomposition in the projection domain, obtain preliminary material decomposition results, and generate a virtual monoenergetic projection at high energy and a suitable low energy virtual monoenergetic projection. The specific energy is related to the system energy spectrum.

[0087] S02: Using the corrected projection of the multi-matter energy spectrum as a physical prior, combined with the low-energy virtual monoenergetic projection for error correction, to obtain the corrected low-energy virtual monoenergetic projection.

[0088] S03: Utilize the high-energy virtual monoenergetic projection and the corrected low-energy virtual monoenergetic projection to obtain the corrected material decomposition result, and reconstruct the reconstructed images of the base material water and bone and the virtual monoenergetic images at different energies.

[0089] It should be noted that while improving the energy separation, it usually leads to a certain loss of high-energy photons, which will further reduce the signal level of high-energy data. Therefore, different factors must be weighed in the actual design process of the embodiments of the present application.

[0090] According to the dual-energy CT material decomposition method proposed in the embodiment of the present application, the result of multi-material energy spectrum correction can be used to replace the result of material decomposition at the projection point where the signal level is too low, so as to reduce the decomposition error and eliminate the streak artifacts. The virtual monoenergetic projection that eliminates the streak artifacts can be combined with the higher energy virtual monoenergetic projection generated by the material decomposition to solve a more accurate decomposition result, thereby effectively reducing the impact of the material decomposition error, suppressing the artifacts caused by the decomposition error, and effectively correcting the error of conventional dual-energy material decomposition, thereby improving the accuracy of material decomposition.

[0091] Next, the dual-energy CT material decomposition device proposed according to the embodiment of the present application is described with reference to the accompanying drawings.

[0092] Figure 7 It is a block diagram of a dual-energy CT material decomposition device according to an embodiment of the present application.

[0093] like Figure 7 As shown, the dual-energy CT material decomposition device 10 includes: an acquisition module 101 , a decomposition module 102 and a correction module 103 .

[0094] Among them, the acquisition module 101 is used to obtain the high-energy projection of the target to be measured whose average energy of the equivalent energy spectrum is higher than the preset value and the low-energy projection of the equivalent energy spectrum whose average energy is lower than the preset value during CT scanning; the decomposition module 102 is used to perform material decomposition in the projection domain according to the high-energy projection and the low-energy projection, and obtain the preliminary decomposition result of the target to be measured, while generating a high-energy virtual monoenergetic projection and a low-energy virtual monoenergetic projection; the correction module 103 is used to correct the projection error of the low-energy virtual monoenergetic projection, obtain the corrected low-energy virtual monoenergetic projection, and use the corrected low-energy virtual monoenergetic projection and the high-energy virtual monoenergetic projection to correct the decomposition error of the preliminary decomposition result, so as to obtain the final decomposition result of the target to be measured.

[0095] In an embodiment of the present application, the correction module 103 is further used to: weight the high-energy projection and the low-energy projection to obtain a total projection under the full energy spectrum; use the total projection under the full energy spectrum to correct the decomposition error of the low-energy virtual monoenergetic projection to obtain a corrected low-energy virtual monoenergetic projection.

[0096] In the embodiment of the present application, the correction module 103 is further used to: correct the multi-material energy spectrum of the total projection under the full energy spectrum to obtain the total projection after energy spectrum correction.

[0097] In an embodiment of the present application, the correction module 103 is further used to: obtain the counting level of the high-energy projection; match the respective weights of the total projection after energy spectrum correction and the low-energy virtual monoenergetic projection according to the counting level, and obtain the corrected low-energy virtual monoenergetic projection after weighting.

[0098] In an embodiment of the present application, the correction module 103 is further used to: reconstruct the bones of the target to be measured based on the total projection under the full energy spectrum to obtain a reconstructed image; perform threshold segmentation on the pre-reconstructed image to obtain the bone distribution of the target to be measured, and obtain the bone projection through forward projection; calculate the hardening error in the total projection based on the bone projection and the total projection, correct the energy spectrum error of the total projection based on the hardening error, and obtain the total projection after energy spectrum correction.

[0099] In an embodiment of the present application, the decomposition module 102 is further used to: decompose water and bones in the high-energy projection and the low-energy projection to obtain the water projection and the bone projection of the target to be measured; reconstruct the water image of the target to be measured based on the water projection, and reconstruct the bone image of the target to be measured based on the bone projection; match the weights of the water projection and the bone projection at different energies according to the attenuation coefficients of water and bones at different energies, and weight the water projection and the bone projection at different energies to obtain a high-energy virtual monoenergetic projection and a low-energy virtual monoenergetic projection.

[0100] It should be noted that the above explanation of the dual-energy CT material decomposition method embodiment is also applicable to the dual-energy CT material decomposition device of this embodiment, and will not be repeated here.

[0101] The dual-energy CT material decomposition device proposed in the embodiment of the present application can reduce the impact of material decomposition errors and suppress artifacts caused by decomposition errors, thereby achieving correction of conventional dual-energy material decomposition errors and obtaining more accurate decomposition results.

[0102] Figure 8 Schematic diagram of the dual-energy CT material decomposition system provided in an embodiment of the present application.

[0103] like Figure 8 As shown, the dual-energy CT material decomposition system 20 may include: an X-ray source 201 , a double-layer flat panel detector 202 , and the dual-energy CT material decomposition device 10 described above.

[0104] Among them, the X-ray source 201 is used to emit X-rays during CT scanning; the double-layer flat-panel detector 202 is used to collect high-energy projections whose average energy of equivalent energy spectrum is higher than a preset value and low-energy projections whose average energy of equivalent energy spectrum is lower than a preset value during CT scanning; the above-mentioned dual-energy CT material decomposition device 10 is used to obtain the final decomposition result of the target to be measured based on the high-energy projection and the low-energy projection.

[0105] In the embodiment of the present application, the double-layer flat-panel detector 202 is composed of a first detector and a second detector stacked in parallel, wherein the first detector is used to absorb low-energy X-ray photons whose average energy of an equivalent energy spectrum is lower than a preset value to obtain a low-energy projection, and the second detector is used to absorb high-energy X-ray photons whose average energy of an equivalent energy spectrum is higher than a preset value to obtain a high-energy projection.

[0106] It should be noted that the aforementioned explanation of the dual-energy CT material decomposition method embodiment is also applicable to the dual-energy CT material decomposition system of this embodiment, and will not be repeated here.

[0107] The dual-energy CT material decomposition system proposed in the embodiment of the present application can reduce the impact of material decomposition errors and suppress artifacts caused by decomposition errors, thereby achieving correction of conventional dual-energy material decomposition errors and obtaining more accurate decomposition results.

[0108] Fig. 9 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application. The electronic device may include:

[0109] A memory 901 , a processor 902 , and a computer program stored in the memory 901 and executable on the processor 902 .

[0110] When the processor 902 executes the program, the dual-energy CT material decomposition method provided in the above embodiment is implemented.

[0111] Furthermore, the electronic device further comprises:

[0112] The communication interface 903 is used for communication between the memory 901 and the processor 902 .

[0113] The memory 901 is used to store computer programs that can be executed on the processor 902 .

[0114] The memory 901 may include a high-speed RAM (Random Access Memory) memory, and may also include a non-volatile memory, such as at least one disk memory.

[0115] If the memory 901, the processor 902 and the communication interface 903 are implemented independently, the communication interface 903, the memory 901 and the processor 902 can be connected to each other through a bus and communicate with each other. The bus can be an ISA (Industry Standard Architecture) bus, a PCI (Peripheral Component Interconnect) bus or an EISA (Extended Industry Standard Architecture) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Fig. 9 Only one thick line is used in the diagram, but this does not mean that there is only one bus or only one type of bus.

[0116] Optionally, in a specific implementation, if the memory 901, the processor 902 and the communication interface 903 are integrated on a chip, the memory 901, the processor 902 and the communication interface 903 can communicate with each other through an internal interface.

[0117] The processor 902 may be a CPU (Central Processing Unit), or an ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement the embodiments of the present application.

[0118] The embodiment of the present application further provides a computer-readable storage medium having a computer program stored thereon, which implements the above dual-energy CT material decomposition method when executed by a processor.

[0119] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0120] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0121] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0122] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiment, the N steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array, a field programmable gate array, etc.

[0123] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0124] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A dual-energy CT material decomposition method, characterized in that: The following steps are involved: Acquire a high-energy projection of a target to be measured whose average energy of equivalent energy spectrum is higher than a preset value and a low-energy projection of whose average energy of equivalent energy spectrum is lower than the preset value during CT scanning; Decomposing the material in the projection domain according to the high-energy projection and the low-energy projection, obtaining a preliminary decomposition result of the target to be measured, and generating a high-energy virtual monoenergetic projection and a low-energy virtual monoenergetic projection; as well as Correcting the projection error of the low-energy virtual monoenergetic projection by using the total projection under the full energy spectrum to obtain the corrected low-energy virtual monoenergetic projection comprises: Obtaining a count level of the high energy projection; The respective weights of the total projection after energy spectrum correction according to the counting level matching and the low-energy virtual monoenergetic projection are obtained after weighting, and the corrected low-energy virtual monoenergetic projection and the high-energy virtual monoenergetic projection are used to correct the decomposition error of the preliminary decomposition result to obtain the final decomposition result of the target to be measured.

2. The method according to claim 1, characterized in that The step of correcting the projection error of the low-energy virtual monoenergetic projection to obtain a corrected low-energy virtual monoenergetic projection comprises: The high energy projection and the low energy projection are weighted to obtain a total projection under the full energy spectrum.

3. The method according to claim 2, characterized in that Before correcting the projection error of the low-energy virtual monoenergetic projection by using the total projection under the full energy spectrum, the method further comprises: The multi-material energy spectrum hardening error of the total projection under the full energy spectrum is corrected to obtain the total projection after energy spectrum correction.

4. The method according to claim 3, characterized in that The step of correcting the multi-material energy spectrum hardening error of the total projection under the full energy spectrum to obtain the total projection after energy spectrum correction includes: Reconstructing the bones of the target to be measured based on the total projection under the full energy spectrum to obtain a pre-reconstructed image; Performing threshold segmentation on the pre-reconstructed image to obtain the bone distribution of the target to be measured, and obtaining the bone projection by forward projection; The hardening error in the total projection is calculated according to the bone projection and the total projection, and the energy spectrum error of the total projection is corrected based on the hardening error to obtain the total projection after energy spectrum correction.

5. The method according to claim 1, characterized in that The material decomposition of the projection domain is performed according to the high-energy projection and the low-energy projection to obtain a preliminary decomposition result of the target to be measured, and at the same time, a high-energy virtual monoenergetic projection and a low-energy virtual monoenergetic projection are generated, including: Decomposing water and bones in the high-energy projection and the low-energy projection to obtain a water projection and a bone projection of the target to be measured; Reconstructing a water image of the target to be measured according to the water projection, and reconstructing a bone image of the target to be measured according to the bone projection; The weights of the water projection and the bone projection at different energies are matched according to the attenuation coefficients of water and bones at different energies, and the water projection and the bone projection are weighted at different energies to obtain the high-energy virtual monoenergetic projection and the low-energy virtual monoenergetic projection.

6. A dual-energy CT material decomposition device, characterized in that: include: An acquisition module, used for acquiring a high-energy projection whose average energy of equivalent energy spectrum is higher than a preset value and a low-energy projection whose average energy of equivalent energy spectrum is lower than the preset value during CT scanning of the target to be measured; A decomposition module, used for performing material decomposition of the projection domain according to the high-energy projection and the low-energy projection, obtaining a preliminary decomposition result of the target to be measured, and generating a high-energy virtual monoenergetic projection and a low-energy virtual monoenergetic projection; as well as A correction module, which uses the total projection under the full energy spectrum to correct the projection error of the low-energy virtual monoenergetic projection to obtain the corrected low-energy virtual monoenergetic projection, and is also used to obtain the counting level of the high-energy projection, and according to the counting level, the respective weights of the total projection after energy spectrum correction and the low-energy virtual monoenergetic projection are matched, and the corrected low-energy virtual monoenergetic projection is obtained after weighting, and the corrected low-energy virtual monoenergetic projection and the high-energy virtual monoenergetic projection are used to correct the decomposition error of the preliminary decomposition result to obtain the final decomposition result of the target to be measured.

7. The device according to claim 6, characterized in that The correction module is further used for: The high energy projection and the low energy projection are weighted to obtain a total projection under the full energy spectrum.

8. The device according to claim 7, characterized in that The correction module is further used for: The multi-material energy spectrum hardening error of the total projection under the full energy spectrum is corrected to obtain the total projection after energy spectrum correction.

9. The device according to claim 7, characterized in that The correction module is further used for: Reconstructing the bones of the target to be measured based on the total projection under the full energy spectrum to obtain a pre-reconstructed image; Performing threshold segmentation on the pre-reconstructed image to obtain the bone distribution of the target to be measured, and obtaining the bone projection by forward projection; The hardening error in the total projection is calculated according to the bone projection and the total projection, and the energy spectrum error of the total projection is corrected based on the hardening error to obtain the total projection after energy spectrum correction.

10. The device according to claim 6, characterized in that The decomposition module is further used for: Decomposing water and bones in the high-energy projection and the low-energy projection to obtain a water projection and a bone projection of the target to be measured; Reconstructing a water image of the target to be measured according to the water projection, and reconstructing a bone image of the target to be measured according to the bone projection; The weights of the water projection and the bone projection at different energies are matched according to the attenuation coefficients of water and bones at different energies, and the water projection and the bone projection are weighted at different energies to obtain the high-energy virtual monoenergetic projection and the low-energy virtual monoenergetic projection.

11. A dual-energy CT material decomposition system, characterized in that: include: An X-ray source, used to emit X-rays during CT scanning; A double-layer flat-panel detector, used for collecting high-energy projections whose average energy of equivalent energy spectrum is higher than a preset value and low-energy projections whose average energy of equivalent energy spectrum is lower than the preset value during CT scanning; as well as The dual-energy CT material decomposition device according to any one of claims 6 to 10, is used to obtain a final decomposition result of the target to be measured based on the high-energy projection and the low-energy projection.

12. The system according to claim 11, characterized in that The double-layer flat-panel detector is composed of a first detector and a second detector stacked in parallel, wherein the first detector is used to absorb low-energy X-ray photons whose average energy of an equivalent energy spectrum is lower than a preset value to obtain the low-energy projection, and the second detector is used to absorb high-energy X-ray photons whose average energy of an equivalent energy spectrum is higher than a preset value to obtain the high-energy projection.

13. An electronic device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the dual-energy CT material decomposition method according to any one of claims 1 to 5.

14. A computer-readable storage medium having a computer program stored thereon, characterized in that: The program is executed by a processor to implement the dual-energy CT material decomposition method according to any one of claims 1 to 5.

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