BACKGROUND Posterior lumbar interbody fusion has good clinical results,but adjacent segment disease(ASD)affects its long-term efficacy.In patients with L4-5 fusion who were followed up for more than 10 years,the ASD i...BACKGROUND Posterior lumbar interbody fusion has good clinical results,but adjacent segment disease(ASD)affects its long-term efficacy.In patients with L4-5 fusion who were followed up for more than 10 years,the ASD incidence was 33.3%.Magnetic resonance imaging(MRI)is key for ASD diagnosis,but metal artifacts from internal fixation limit its use;therefore,removing the artifacts is crucial for ASD diagnosis and treatment.AIM To evaluate the value of WARP MRI for patients with lumbar ASD.METHODS In our hospital,the lumbar spines of patients with ASD were assessed via lumbar MRI,including conventional sequences and sequences for artifacts.A PACS workstation was used for image measurement,analysis,and assessment,which mainly included measurement of the internal fixation implant artifact area,evaluation of the visibility of the anatomical structures surrounding the implant,and diagnostic assessment of ASD in the section.Conventional MRI data sequences and artifacts to sequence the contrast analysis of the MRI data.RESULTS A total of 30 patients with ASD after lumbar fusion and internal fixation were included in the study;the patients included 13 male and 17 female patients and were aged 66.03±5.83 years.The metal artifact area of the WARP T2-tirm sequence was significantly smaller than that of the conventional STIR sequence[(20.85±6.27)cm²vs(50.56±8.55)cm²,P<0.01].The WARP T2-tirm sequence was observed around the implants,pedicles,intervertebral foramen,and vertebral bodies,and the conventional STIR sequence clearly displayed nerve roots within the intervertebral foramen.In all 30 patients,all adjacent segments of the WARP T2-tirm sequence could be clearly observed(above Grade 4),whereas it was difficult to observe these segments in the conventional STIR sequence due to the presence of more severe metal artifacts.CONCLUSION WARP sequences can significantly reduce the artifact area in the sagittal and cross-sectional images of titanium alloy spinal fixation,providing a good imaging reference for the diagnosis of ASD.展开更多
When the object contains metals,its x-ray computed tomography(CT)images are normally affected by streaking artifacts.These artifacts are mainly caused by the x-ray beam hardening effects,which deviate the measurements...When the object contains metals,its x-ray computed tomography(CT)images are normally affected by streaking artifacts.These artifacts are mainly caused by the x-ray beam hardening effects,which deviate the measurements from their true values.One interesting observation of the metal artifacts is that certain regions of the metal artifacts often appear as negative pixel values.Our novel idea in this paper is to set up an objective function that restricts the negative pixel values in the image.We must point out that the naïve idea of setting the negative pixel values in the reconstructed image to zero does not give the same result.This paper proposes an iterative algorithm to optimize this objective function,and the unknowns are the metal affected projections.Once the metal affected projections are estimated,the filtered backprojection algorithm is used to reconstruct the final image.This paper applies the proposed algorithm to some airport bag CT scans.The bags all contain unknown metallic objects.The metal artifacts are effectively reduced by the proposed algorithm.展开更多
To solve the problem that metal artifacts severely damage the clarity of the organization structure in computed tomography（CT） images, a sinogram fusion-based metal artifact correction method is proposed. First, the...To solve the problem that metal artifacts severely damage the clarity of the organization structure in computed tomography（CT） images, a sinogram fusion-based metal artifact correction method is proposed. First, the metal image is segmented from the original CT image by the pre-set threshold. The original CT image and metal image are forward projected into the original projection sinogram and metal projection sinogram, respectively. The interpolation-based correction method and mean filter are used to correct the original CT image and preserve the edge of the corrected CT image, respectively. The filtered CT image is forward projected into the filtered image sinogram. According to the position of the metal sinogram in the original sinogram and filtered image sinogram, the corresponding sinograms PM^D （ in the original sinogram） and PM^C （ in the filtered image sinogram）can be acquired from the original sinogram and filtered image sinogram, respectively. Then, PM^D and PM^C are fused into the fused metal sinogram PM^F according to a certain proportion.The final sinogram can be acquired by fusing PM^F , PM^D and the original sinogram P^O. Finally, the final sinogram is reconstructed into the corrected CT image and metal information is compensated into the corrected CT image.Experiments on clinical images demonstrate that the proposed method can effectively reduce metal artifacts. A comparison with classical metal artifacts correction methods shows that the proposed metal artifacts correction method performs better in metal artifacts suppression and tissue feature preservation.展开更多
It is not easy to reduce the metal artifacts of computed tomography images.However,the pixel values inside the metal artifact regions vary smoothly,while those on the borders of the metal and the bone regions vary sha...It is not easy to reduce the metal artifacts of computed tomography images.However,the pixel values inside the metal artifact regions vary smoothly,while those on the borders of the metal and the bone regions vary sharply.When the Canny operation by adaptive thresholding is conducted on the raw image,the almost continuous edges can be formed obviously on the borders of the metal and the bone regions,but this kind of information cannot be formed for the metal artifact regions.In this paper,by searching the closed areas formed by the border edges of the bone regions in the Canny image,the metal artifact regions,which are very difficult to discriminate only by intensity thresholding,can be excluded effectively.A novel prior image-based method is thus developed for metal artifact reduction.The experiments demonstrate that the proposed method can be realized easily and reduce the metal artifacts effectively even if multiple large metal objects exist simultaneously in the image.The method is suitable for the clinical application.展开更多
This study presents an energy consumption(EC)forecasting method for laser melting manufacturing of metal artifacts based on fusionable transfer learning(FTL).To predict the EC of manufacturing products,particularly fr...This study presents an energy consumption(EC)forecasting method for laser melting manufacturing of metal artifacts based on fusionable transfer learning(FTL).To predict the EC of manufacturing products,particularly from scale-down to scale-up,a general paradigm was first developed by categorizing the overall process into three main sub-steps.The operating electrical power was further formulated as a combinatorial function,based on which an operator learning network was adopted to fit the nonlinear relations between the fabricating arguments and EC.Parallel-arranged networks were constructed to investigate the impacts of fabrication variables and devices on power.Considering the interconnections among these factors,the outputs of the neural networks were blended and fused to jointly predict the electrical power.Most innovatively,large artifacts can be decomposed into timedependent laser-scanning trajectories,which can be further transformed into fusionable information via neural networks,inspired by large language model.Accordingly,transfer learning can deal with either scale-down or scale-up forecasting,namely,FTL with scalability within artifact structures.The effectiveness of the proposed FTL was verified through physical fabrication experiments via laser powder bed fusion.The relative error of the average and overall EC predictions based on FTL was maintained below 0.83%.The melting fusion quality was examined using metallographic diagrams.The proposed FTL framework can forecast the EC of scaled structures,which is particularly helpful in price estimation and quotation of large metal products towards carbon peaking and carbon neutrality.展开更多
Metal objects in X-ray computed tomography can cause severe artifacts.The state-of-the-art metal artifact reduction methods are in the sinogram inpainting category and are iterative methods.This paper proposes a proje...Metal objects in X-ray computed tomography can cause severe artifacts.The state-of-the-art metal artifact reduction methods are in the sinogram inpainting category and are iterative methods.This paper proposes a projectiondomain algorithm to reduce the metal artifacts.In this algorithm,the unknowns are the metal-affected projections,while the objective function is set up in the image domain.The data fidelity term is not utilized in the objective function.The objective function of the proposed algorithm consists of two terms:the total variation of the metalremoved image and the energy of the negative-valued pixels in the image.After the metal-affected projections are modified,the final image is reconstructed via the filtered backprojection algorithm.The feasibility of the proposed algorithm has been verified by real experimental data.展开更多
Several bulk metallic glasses （BMGs） were selected to in vitro assess their magnetic resonance imaging （MRI） compatibility with agarose gel as a phantom, in terms of the extent of susceptibility artifacts in magne...Several bulk metallic glasses （BMGs） were selected to in vitro assess their magnetic resonance imaging （MRI） compatibility with agarose gel as a phantom, in terms of the extent of susceptibility artifacts in magnetic resonance image. The investigated metals include the Au49Ags.sPd2.3Cu26.9Si16.3, Zr61Ti2Cu2sA112, Cu50.4Nis.0Ti31Zr13 and Ti47Cu38Zr7.5Fe2.5Sn2Si1Ag2, together with pure titanium （CP-Ti） and Co-28Cr-6Mo alloy （ASTM-F799） for comparison. The artifact extent in MR images was quantitatively characterized according to the total volume in reconstructed 3D images with a series of slices under acquisition by fast spin echo （FSE） sequence and gradient echo （GRE） sequence. As indicated, artifact severity of the BMGs is much less than that of the CoCrMo alloy. The AuAgPdCuSi BMG manifested the smallest arti- fact among the four BMGs, while the TiCuZrFeSnSiAg BMG is comparative to the CP-Ti. The MRI compatibility of BMGs is ranked as a sequence of the Au-, Zr-, Cu- and Ti-based alloys. Dependence of material mag- netic susceptibility on artifact extent is also the case of the BMGs, even though it does not follow a simple linear relationship within a range of △χv = 30-180 ppm. These findings are of interest to reveal that the BMGs are potentially applied in the fields associated with an interventional MRI for MRI-guided surgeries.展开更多
Due to the beam-hardening effect of the broad energy spectrum of the X-ray source in computed tomography,the reconstructed images usually suffer from severe artifacts when metallic objects are being imaged.Metal artif...Due to the beam-hardening effect of the broad energy spectrum of the X-ray source in computed tomography,the reconstructed images usually suffer from severe artifacts when metallic objects are being imaged.Metal artifact correction methods are usually sophisticated and not practical,especially in some non-medical applications,in which the linear attenuation coefficients are unknown.This paper suggests a simple and effective algorithm to estimate the unreliable measurements.The proposed algorithm is an iterative algorithm,in which the iteration is performed in the projection domain,while the objective function is set up in the image domain.The final image is reconstructed with the conventional filtered backprojection algorithm.The feasibility of the proposed method is verified with airport bags that contain some unknown metals.展开更多
High-attenuation object-induced streaking and shadow artifacts in computerized to- mography （CT） are somewhat connected to the misfit of the X-ray projection data to the range space of the Radon transform. This misf...High-attenuation object-induced streaking and shadow artifacts in computerized to- mography （CT） are somewhat connected to the misfit of the X-ray projection data to the range space of the Radon transform. This misfit is mainly due to the beam hardening factor of the projection data which is unavoidable for polychromatic sources. The major difficulty in dealing with the beam hardening-induced streaking and shadow artifacts comes from its highly nonlinear nature depending on geometries of high attenuation objects. In this work, we investigate the mathematical characteristics of those streaking and shadow artifacts from the structure of the projection data. We also proposed a metal artifacts reduction method by incorporating the recent technique of the nonlinear beam-hardening corrector. Numerical simulations show that the proposed method effectively alleviates the streaking artifacts without changing the background images.展开更多
基金Supported by Shanghai Tongren Hospital Scientific Research Funds,No.TRKYRC-xx202203Shanghai Municipal Health Commission,No.2022YQ006Science and Technology Commission of Shanghai Municipality,No.22ZR1457200.
文摘BACKGROUND Posterior lumbar interbody fusion has good clinical results,but adjacent segment disease(ASD)affects its long-term efficacy.In patients with L4-5 fusion who were followed up for more than 10 years,the ASD incidence was 33.3%.Magnetic resonance imaging(MRI)is key for ASD diagnosis,but metal artifacts from internal fixation limit its use;therefore,removing the artifacts is crucial for ASD diagnosis and treatment.AIM To evaluate the value of WARP MRI for patients with lumbar ASD.METHODS In our hospital,the lumbar spines of patients with ASD were assessed via lumbar MRI,including conventional sequences and sequences for artifacts.A PACS workstation was used for image measurement,analysis,and assessment,which mainly included measurement of the internal fixation implant artifact area,evaluation of the visibility of the anatomical structures surrounding the implant,and diagnostic assessment of ASD in the section.Conventional MRI data sequences and artifacts to sequence the contrast analysis of the MRI data.RESULTS A total of 30 patients with ASD after lumbar fusion and internal fixation were included in the study;the patients included 13 male and 17 female patients and were aged 66.03±5.83 years.The metal artifact area of the WARP T2-tirm sequence was significantly smaller than that of the conventional STIR sequence[(20.85±6.27)cm²vs(50.56±8.55)cm²,P<0.01].The WARP T2-tirm sequence was observed around the implants,pedicles,intervertebral foramen,and vertebral bodies,and the conventional STIR sequence clearly displayed nerve roots within the intervertebral foramen.In all 30 patients,all adjacent segments of the WARP T2-tirm sequence could be clearly observed(above Grade 4),whereas it was difficult to observe these segments in the conventional STIR sequence due to the presence of more severe metal artifacts.CONCLUSION WARP sequences can significantly reduce the artifact area in the sagittal and cross-sectional images of titanium alloy spinal fixation,providing a good imaging reference for the diagnosis of ASD.
基金This research is partially supported by NIH,No.R15EB024283.
文摘When the object contains metals,its x-ray computed tomography(CT)images are normally affected by streaking artifacts.These artifacts are mainly caused by the x-ray beam hardening effects,which deviate the measurements from their true values.One interesting observation of the metal artifacts is that certain regions of the metal artifacts often appear as negative pixel values.Our novel idea in this paper is to set up an objective function that restricts the negative pixel values in the image.We must point out that the naïve idea of setting the negative pixel values in the reconstructed image to zero does not give the same result.This paper proposes an iterative algorithm to optimize this objective function,and the unknowns are the metal affected projections.Once the metal affected projections are estimated,the filtered backprojection algorithm is used to reconstruct the final image.This paper applies the proposed algorithm to some airport bag CT scans.The bags all contain unknown metallic objects.The metal artifacts are effectively reduced by the proposed algorithm.
基金Open Research Fund of the Key Laboratory of Computer Netw ork and Information Integration of Ministry of Education of Southeast University(No.K93-9-2014-10C)the Scientific Research Foundation of Education Department of Anhui Province(No.KJ2014A186,SK2015A433)the National Basic Research Program of China(973 Program)(No.2010CB732503)
文摘To solve the problem that metal artifacts severely damage the clarity of the organization structure in computed tomography（CT） images, a sinogram fusion-based metal artifact correction method is proposed. First, the metal image is segmented from the original CT image by the pre-set threshold. The original CT image and metal image are forward projected into the original projection sinogram and metal projection sinogram, respectively. The interpolation-based correction method and mean filter are used to correct the original CT image and preserve the edge of the corrected CT image, respectively. The filtered CT image is forward projected into the filtered image sinogram. According to the position of the metal sinogram in the original sinogram and filtered image sinogram, the corresponding sinograms PM^D （ in the original sinogram） and PM^C （ in the filtered image sinogram）can be acquired from the original sinogram and filtered image sinogram, respectively. Then, PM^D and PM^C are fused into the fused metal sinogram PM^F according to a certain proportion.The final sinogram can be acquired by fusing PM^F , PM^D and the original sinogram P^O. Finally, the final sinogram is reconstructed into the corrected CT image and metal information is compensated into the corrected CT image.Experiments on clinical images demonstrate that the proposed method can effectively reduce metal artifacts. A comparison with classical metal artifacts correction methods shows that the proposed metal artifacts correction method performs better in metal artifacts suppression and tissue feature preservation.
文摘It is not easy to reduce the metal artifacts of computed tomography images.However,the pixel values inside the metal artifact regions vary smoothly,while those on the borders of the metal and the bone regions vary sharply.When the Canny operation by adaptive thresholding is conducted on the raw image,the almost continuous edges can be formed obviously on the borders of the metal and the bone regions,but this kind of information cannot be formed for the metal artifact regions.In this paper,by searching the closed areas formed by the border edges of the bone regions in the Canny image,the metal artifact regions,which are very difficult to discriminate only by intensity thresholding,can be excluded effectively.A novel prior image-based method is thus developed for metal artifact reduction.The experiments demonstrate that the proposed method can be realized easily and reduce the metal artifacts effectively even if multiple large metal objects exist simultaneously in the image.The method is suitable for the clinical application.
基金funded by the National Key Research and Development Program of China,No.2022YFB3303303Key Open Fund of State Key Lab of Materials Processing and Die&Mould Technology of China,No.P2024-001Zhejiang Provincial Research and Development Project of China,No.LGG22E050010。
文摘This study presents an energy consumption(EC)forecasting method for laser melting manufacturing of metal artifacts based on fusionable transfer learning(FTL).To predict the EC of manufacturing products,particularly from scale-down to scale-up,a general paradigm was first developed by categorizing the overall process into three main sub-steps.The operating electrical power was further formulated as a combinatorial function,based on which an operator learning network was adopted to fit the nonlinear relations between the fabricating arguments and EC.Parallel-arranged networks were constructed to investigate the impacts of fabrication variables and devices on power.Considering the interconnections among these factors,the outputs of the neural networks were blended and fused to jointly predict the electrical power.Most innovatively,large artifacts can be decomposed into timedependent laser-scanning trajectories,which can be further transformed into fusionable information via neural networks,inspired by large language model.Accordingly,transfer learning can deal with either scale-down or scale-up forecasting,namely,FTL with scalability within artifact structures.The effectiveness of the proposed FTL was verified through physical fabrication experiments via laser powder bed fusion.The relative error of the average and overall EC predictions based on FTL was maintained below 0.83%.The melting fusion quality was examined using metallographic diagrams.The proposed FTL framework can forecast the EC of scaled structures,which is particularly helpful in price estimation and quotation of large metal products towards carbon peaking and carbon neutrality.
基金This research is partially supported by NIH,No.R15EB024283.
文摘Metal objects in X-ray computed tomography can cause severe artifacts.The state-of-the-art metal artifact reduction methods are in the sinogram inpainting category and are iterative methods.This paper proposes a projectiondomain algorithm to reduce the metal artifacts.In this algorithm,the unknowns are the metal-affected projections,while the objective function is set up in the image domain.The data fidelity term is not utilized in the objective function.The objective function of the proposed algorithm consists of two terms:the total variation of the metalremoved image and the energy of the negative-valued pixels in the image.After the metal-affected projections are modified,the final image is reconstructed via the filtered backprojection algorithm.The feasibility of the proposed algorithm has been verified by real experimental data.
基金supported by the National Natural Science Foundation of China under Grant No.51571192
文摘Several bulk metallic glasses （BMGs） were selected to in vitro assess their magnetic resonance imaging （MRI） compatibility with agarose gel as a phantom, in terms of the extent of susceptibility artifacts in magnetic resonance image. The investigated metals include the Au49Ags.sPd2.3Cu26.9Si16.3, Zr61Ti2Cu2sA112, Cu50.4Nis.0Ti31Zr13 and Ti47Cu38Zr7.5Fe2.5Sn2Si1Ag2, together with pure titanium （CP-Ti） and Co-28Cr-6Mo alloy （ASTM-F799） for comparison. The artifact extent in MR images was quantitatively characterized according to the total volume in reconstructed 3D images with a series of slices under acquisition by fast spin echo （FSE） sequence and gradient echo （GRE） sequence. As indicated, artifact severity of the BMGs is much less than that of the CoCrMo alloy. The AuAgPdCuSi BMG manifested the smallest arti- fact among the four BMGs, while the TiCuZrFeSnSiAg BMG is comparative to the CP-Ti. The MRI compatibility of BMGs is ranked as a sequence of the Au-, Zr-, Cu- and Ti-based alloys. Dependence of material mag- netic susceptibility on artifact extent is also the case of the BMGs, even though it does not follow a simple linear relationship within a range of △χv = 30-180 ppm. These findings are of interest to reveal that the BMGs are potentially applied in the fields associated with an interventional MRI for MRI-guided surgeries.
文摘Due to the beam-hardening effect of the broad energy spectrum of the X-ray source in computed tomography,the reconstructed images usually suffer from severe artifacts when metallic objects are being imaged.Metal artifact correction methods are usually sophisticated and not practical,especially in some non-medical applications,in which the linear attenuation coefficients are unknown.This paper suggests a simple and effective algorithm to estimate the unreliable measurements.The proposed algorithm is an iterative algorithm,in which the iteration is performed in the projection domain,while the objective function is set up in the image domain.The final image is reconstructed with the conventional filtered backprojection algorithm.The feasibility of the proposed method is verified with airport bags that contain some unknown metals.
文摘High-attenuation object-induced streaking and shadow artifacts in computerized to- mography （CT） are somewhat connected to the misfit of the X-ray projection data to the range space of the Radon transform. This misfit is mainly due to the beam hardening factor of the projection data which is unavoidable for polychromatic sources. The major difficulty in dealing with the beam hardening-induced streaking and shadow artifacts comes from its highly nonlinear nature depending on geometries of high attenuation objects. In this work, we investigate the mathematical characteristics of those streaking and shadow artifacts from the structure of the projection data. We also proposed a metal artifacts reduction method by incorporating the recent technique of the nonlinear beam-hardening corrector. Numerical simulations show that the proposed method effectively alleviates the streaking artifacts without changing the background images.
