Objective.Despite major advances in dual-energy computed tomography (CT), obtaining accurate attenuation values for quantitative applications remains a technical challenge. To address this topic, we introduce a novel projection data domain material decomposition method that is an extension of an approach we recently proposed for beam hardening correction in single energy CT.Approach.The proposed method employs object-specific scatter correction and an analytical energy response model. We compare its performance to image-based material decomposition on accuracy of attenuation values using the American College of Radiology (ACR) CT accreditation phantom, scanned with consecutive low and high energy axial scans in centered and off-centered positions. Accuracy is assessed across the five inserts, and the images are analyzed for beam hardening artifacts and noise. Additionally, we assess the usefulness of object-specific scatter correction, and we assess performance over conventional data domain material decomposition and for anthropomorphic abdomen phantom imaging.Main results.In the ACR phantom, the proposed method yielded a significant improvement in accuracy of the attenuation values, particularly at low energies (<70 keV), and an important reduction in beam hardening artifacts. While similarly high accuracy was achieved for water, quantitative error within the non-water inserts was lower and more uniform across the 30-140 keV range, especially in the more challenging off-centered positioning of the phantom. Noise showed expected parabolic behavior, but with minimum at lower keV, which may be clinically advantageous. Object-specific scatter correction was shown to prevent major artifacts. Advantages over conventional data-domain decomposition clearly appeared when only a standard phantom is available to calibrate the latter. Lastly, the proposed method was shown to perform well, without any changes, in the more complex scenario of abdominal phantom imaging.Significance.This work demonstrates that data-based material decomposition using an analytical energy response model with object-specific scatter correction offers a promising pathway to improve accuracy of CT attenuation values.

Abstract The x-ray attenuation coefficient of most materials is energy-dependent, and this dependence varies among materials. Moreover, the x-ray beam in a typical computed tomography (CT) scanner has a broad energy spectrum. Therefore, image reconstruction from x-ray CT data is a nonlinear problem. If the nonlinear nature of CT data is ignored and a linear reconstruction formula is used, which is frequently the case, the resulting image contains beam-hardening artifacts such as streaks. In this work, we describe the nonlinearity of CT data using a conventional and widely accepted model. Our main contribution is the characterization of streak artifacts arising from this nonlinearity. We also obtain an explicit expression for the leading singular behavior of the reconstruction near the streaks. Finally, numerical experiments are conducted to validate the theoretical results.

Cone beam computed tomography (CBCT) X-ray imaging suffers from poor soft tissue contrast, HU instability, and beam hardening artifacts. The generalizability of the commonly used signal-to-equivalent thickness calibration (STC) method is limited by scattering in large field-of-view (FOV) settings. We therefore introduce scatter-reduced STC (SR-STC) to improve robustness across varying scatter conditions. For STC, multiple acrylic thicknesses were imaged to derive pixel-wise calibration curves relating measured beam intensity to material thickness. In the SR-STC approach, a scatter intensity image was subtracted from each thickness projection prior to calibration. Projection data was processed prior to reconstruction. A spectral CT phantom with tissue-equivalent targets was scanned with varying scattering conditions utilizing a clinical head and neck CBCT device. SR-STC performance was evaluated against FFC, STC, and the vendor reconstruction pipeline. In addition, a linear regression analysis was performed using clinical CT to study HU agreement with clinical benchmark. The introduced SR-STC method improved soft tissue contrast across almost all imaging parameters compared to FFC and vendor reconstructions with the standard STC providing a smaller improvement. For most high contrast targets, SR-STC provided the highest contrast. SR-STC demonstrated best HU value agreement with helical CT. The SR-STC provided high subjective image quality, reducing beam hardening-related artefacts. The conventional STC method did not perform as well across varying imaging settings. This highlights the need for a scatter-reducing act on the common STC method. The introduced SR-STC method was found to be an easy-to-implement calibration method with the potential to improve HU accuracy, soft tissue contrast, and to mitigate beam hardening artifacts in diagnostic CBCT devices.

BackgroundThe microstructure of material at a μm length scale leads to ultra‐small‐angle scattering of X‐rays, which typically occurs, e.g., for lung tissue or some plastic foams. When using an interferometer, this effect alters the visibility of the fringe pattern, which can be detected and resolved by the detector. Thus, the ultra‐small‐angle scattering can be represented as a dark‐field image. For a polychromatic source, the hardening of the source spectrum changes visibility as well, generating an additional fake dark‐field signal by the attenuation of the material on top of the real ultra‐small‐angle scatter‐related dark‐field signal. Consequently, even homogeneous materials without microstructure typically exhibit a change in visibility.PurposeThe objective of this study is to develop a fast, simple, and robust method to correct dark‐field signals and bony structures present due to beam hardening on dark‐field chest radiographs of study participants.MethodsThe method is based on calibration measurements and image processing. BH by bones and soft tissue is modeled by aluminum and water, respectively, which have no microstructure and thus only generate an artificial dark‐field signal. Look‐up tables were then created for both. By using a weighted mean of these, forming a single LUT, and using the attenuation images, the artificial dark‐field signal and thus the bone structures present are reduced for study participants.ResultsIt was found that applying a correction using a weighted LUT leads to a significant reduction of bone structures in the dark‐field image. The weighting of the aluminum component has a substantial impact on the degree to which bone structures remain visible in the dark‐field image. Furthermore, a large negative bias in the dark‐field image–dependent on the aluminum weighting–was successfully corrected.ConclusionsBH‐induced signal in the dark‐field images was successfully reduced using the method described. The choice of aluminum weighting to suppress rib structures, as well as the selection of bias correction, should be evaluated based on the specific clinical question.

The quantitative accuracy of computed tomography (CT) values in contrast-enhanced CT is affected by tube voltage, body size, and scattered radiation. This study aimed to analyze the influence of these factors on CT values using Monte Carlo simulation and to clarify the usefulness of tube voltage optimization considering body size. The Particle and Heavy Ion Transport code System was used to analyze transmitted X-ray spectra at 80-140 kV in water phantoms (16-32 cm in diameter) containing contrast medium. Sinograms were generated under conditions that included both primary and scattered radiation, and images were reconstructed using the filtered back projection method. CT values in the contrast medium region were then evaluated. As body size increased, beam hardening progressed, and CT values in the contrast medium region decreased. This decrease in CT values was more pronounced at higher tube voltages, whereas higher CT values were maintained at lower tube voltages even in large phantoms. Scattered radiation further reduced CT values, with a greater effect observed in larger phantoms. Beam hardening and scattered radiation are major factors that reduce the quantitative accuracy of CT values, particularly in larger body sizes. Low tube voltage imaging is effective for stabilizing CT values and maintaining contrast enhancement. These findings support the optimization of tube voltage tailored to body size.

Metal artifacts in dental computed tomography (CT) severely degrade diagnostic image quality, especially near metallic implants, due to photon starvation and beam hardening. This study presents a simulation-based feasibility evaluation of a hybrid single-energy material decomposition (SEMD)–virtual monochromatic imaging (VMI)-normalized metal artifact reduction (NMAR) framework for artifact suppression in dental CT. The framework applies SEMD to separate soft- and dense-tissue components from a single 80 kVp CT scan, synthesizes virtual monochromatic projections through VMI, and performs NMAR correction on the optimal virtual image. Unlike data-driven or hardware-dependent MAR techniques, this physics-based approach uses only single-energy data without requiring prior knowledge of metallic composition, enhancing interpretability and clinical compatibility. Numerical simulations with a three-dimensional skull phantom containing one, three, and five titanium (Ti) inserts were conducted to assess performance. At 60 keV, the virtual monochromatic CT achieved the higheststructural similarity index measure (SSIM = 0.79) and reduced artifact index (AI = 5.71) compared with the original polychromatic CT (SSIM = 0.76, AI = 5.84). With NMAR, image quality further improved (SSIM = 0.87, AI = 3.58), and the intersection-over-union (IoU) between segmented and reference metal masks increased from 0.69 to 0.95, confirming robustness to segmentation errors. These results demonstrate that the proposed hybrid SEMD-VMI-NMAR framework effectively suppresses artifacts, maintains physical consistency, and offers computational feasibility under clinically relevant single-energy conditions, providing a solid basis for future experimental and clinical validation.

Aligning intraoral scans and cone beam computed tomography scans with beam hardening artifacts: A dental technique.

Dual-energy CT (DECT) offers advantages over single-energy CT and MRI in the evaluation of the pediatric genitourinary system. Material specific techniques allow for creation of virtual noncontrast and iodine overlay images, which can avoid the radiation needed for a dedicated non-contrast CT or highlight areas of contrast enhancement. DECT also offers improved characterization of cysts and masses by differentiating between iodine, calcium, and proteinaceous/hemorrhagic material. Composition analysis of renal stones may allow for tailored stone therapy. Additionally, energy-specific techniques such as virtual monoenergetic images reconstructed at higher kV can reduce artifacts, especially those related to beam hardening. Conversely, virtual monoenergetic images reconstructed at lower kV offer increased contrast conspicuity, allowing for lower radiation and contrast doses. This paper reviews DECT technologies, post-processing techniques of material decomposition and virtual monoenergetic imaging, and examples of pediatric genitourinary clinical applications of DECT.

The objective of the research was to study the modes of electron beam hardening on the structure and properties of surface layers of tool high-speed steels. The limiting modes of electron beam hardening were determined experimentally, which allow obtaining the maximum microhardness of the hardened layer without melting the surface being treated. Based on the results of experimental studies, a comprehensive parameter of the treatment mode was proposed, according to which the intensity of heating and cooling of the surface layer of the tool can be determined - the power density of the beam. This parameter includes all other parameters of the hardening treatment mode: diameter, power, and speed of beam movement relative to the tool surface. It has been established that the maximum hardness of the hardened layer during electron beam treatment can be achieved by high-temperature hardening without melting the treated surface. Hardening without melting also ensures the formation of a highly dispersed structure throughout the entire depth of the hardened layer. Melting of the surface of a tool undergoing electron beam hardening should be considered an extremely undesirable processing option. In the case of melting of the surface layer in a tool made of high-speed steels, a significant decrease in microhardness is observed. At the same time, the surface layer contains a significant amount of residual austenite. Hardening with melting, in which a significant amount of residual austenite is formed, is the main reason for the sharp decrease in the content of carbide phases in the surface layer. Together, all this leads to a decrease in the wear resistance of tool high-speed steels. In the case of hardening with melting, there is also a deterioration in the tool's resistance to large plastic deformations at elevated temperatures in the cutting zone. It has been established that the depth of the hardened layer significantly depends on the initial structure of the steels. The maximum depth of the hardened layer in tool high-speed steels can be obtained by their preliminary heat treatment in the form of volumetric hardening and tempering. Within the framework of the experimental studies, a range of optimal values of the overlap coefficient was established, which corresponds to the minimum values of the tempering zone width.

Purposes: Beam hardening artifacts caused by dental implants remain one of the most significant limitations of cone-beam computed tomography (CBCT), often compromising the evaluation of peri-implant bone and potentially masking critical diagnostic findings. Although metal artifact reduction (MAR) and noise-optimization filters such as the Adaptive Image Noise Optimizer (AINO) are widely available in commercial CBCT systems, their effectiveness varies depending on implant configuration and scanning parameters. A clearer understanding of how implant positioning influences artifact severity-together with how MAR and AINO perform under different conditions-is essential for improving diagnostic reliability. Materials and Methods: A fresh frozen cadaver head, with dental implants inserted using two configurations (C1 and C2), was scanned using different scan parameters, with and without metal artifact reduction and image optimization filters. The percentages of gray value alteration due to artifacts were evaluated, using registered pre-implant scans as a control. Regions of interest were defined by an experienced researcher. For the two implant conditions, ROIs were placed as follows: C1-lingual, buccal and mesial to the mesial implant; lingual, buccal and distal to the distal implant; and an additional ROI between the implants (n = 7); C2-lingual, buccal, mesial and distal to each implant (n = 8). For each ROI, the mean gray value was measured in five consecutive axial slices, and rescaled according to calibration points in air and soft tissue. Results: Significant differences were found in gray values across configurations and scan modes. In the C2 configuration, combined MAR and AINO restored gray values in certain ROIs from 1.227 (OFF) to 1.223 (MAR+AINO), closely matching the control (1.227). In contrast, C1 showed limited improvement; for example, buccal ROI gray values decreased from 3.978 (OFF) to 3.323 (AINO) compared to the control (3.273), with no significant benefit from additional MAR. Conclusion: Artifacts from implants can be significantly affected by their (relative) position and the use of MAR and AINO.

This article presents the effects of novel electron beam hardening (EBH) process parameters in terms of residual stresses (RSs) and microstructure modification in as-received C45 cylindrical specimens. The EBH was performed using continuous irradiation with power in the range of 720–2070 W on an Evobeam µEBW Cube 400 machine. A distinctive feature of the novel surface hardening process is the linear scanning mode in the axial direction of the treated cylindrical surface, which makes it suitable for machining shafts and axles. Using a one-factor-at-a-time technique, the individual effects of the electron beam current Ib, workpiece peripheral velocity vp, scanning frequency (SF), and focal length (FL) on the RSs and microstructure in surface layers were evaluated. The X-ray diffraction results, scanning electron microscopy (SEM) images, and phase analyses confirmed the significant potential of the EBH process for forming compressive RSs due to martensitic transformation in the surface zone and gradient microstructure in terms of structure and phase composition. The measured maximum compressive axial and hoop RSs of −289.5 and −345 MPa, respectively, and compressive zone at a depth of approximately 0.3 mm correlate with the phase transformation region at a depth of approximately 0.2 mm. Based on the results for RSs and microstructure modification, the limitations with respect to the suitable operating parameter values were established. After excluding these operating parameter values, the following suitable ranges of the operating parameters were determined: Ib∈16,36 mA,vp∈18,45 mm/s, SF∈(5000,20,000) Hz, and FL∈(+5,−5) mm. The specified ranges are the basis for conducting a planned experiment on the novel EBH process.

BackgroundLinear accelerators used for cancer treatments, in general, have one flattening filter (FF) for each x‐ray energy. In a newly developed 6 MV low energy linac model, beam optimization at higher dose rates is achieved by two FFs.PurposeTo achieve optimization in higher dose rates for smaller fields with FF, one small flattening filter (SF) for fields covering up to 16 × 16 cm2 and another large flattening filter (LF), to provide flattened fields till 30 × 30 cm2 are made available. A smaller thickness filter selectively flattens central part of the beam.MethodsRecently, a new generation low energy Siddharth II model 6 MV linac is manufactured by M/s Panacea Medical Technologies Pvt Ltd in India, with two FFs. Experimentally measured dose rates with SF and FF vis‐à‐vis un‐flattened open beam were compared with theoretical estimates. Furthermore, a comparison is made with beam characteristics of a True Beam Varian linear accelerator for 6 MV beam.ResultsAs beam hardening is expected with FF, it was taken appropriate to consider 1.20 MeV mean energy for 6 MV bremsstrahlung continuous spectrum, before entry to FF. Measured transmissions of 0.8140 and 0.4470 for SF and LF, respectively, compare well with theoretically estimated 0.7904 and 0.4130. A dose rate enhancement factor 1.821 is achieved along with better flatness for smaller fields. The measured factor 0.4470 for large filter for Siddharth II, is similar to a transmission of 0.5100 for True Beam 6 MV photons.ConclusionAs the first of its kind, the thin FF covers smaller solid angle of the total beam, giving higher MU/min in small fields, which might help for radical treatments. Also, there will be less power input requirements because of gain in dose rate.

The objective of this study was to investigate electron beam hardening (EBH) technology and compare its performance with laser beam hardening (LBH) in the context of manufacturing components such as gears, which increasingly employ submicron bainitic steels. Given the stringent demands for durability and fatigue resistance of gear teeth, identifying an optimal surface hardening method is essential for extending service life. Comprehensive analyses, including light and electron microscopy, hardness testing, tribocorrosion testing, and X-ray diffraction for phase composition, were conducted. The EBH-treated layer exhibited a slightly higher hardness (by 26 HV) compared to the LBH-treated layer (average 654 HV), while the base material measured 393 HV. The EBH process produced a uniform hardness distribution with a subsurface zone of reduced hardness. In contrast, LBH resulted in a surface oxide layer absent in EBH due to its vacuum environment. Both techniques reduced the residual austenite content in the surface layer from 22.5% to approximately 1.3%–1.4%. Notably, EBH achieved comparable hardening effects with nearly half the energy input of LBH, demonstrating superior energy efficiency and industrial feasibility. Application of the developed EBH process to an actual gear component confirmed its practical potential for modern gear manufacturing.

The feasibility of dual-energy X-ray computed tomography (DECT) with experimentally implemented scatter and beam hardening corrections to quantitatively determine the 4D (3D spatial with time) evolution of partial densities of bentonite and water was examined. Compacted bentonite samples were imaged using an X-ray microtomography system with various X-ray spectra before and after two days of water infiltration. The effects of scattering and beam hardening in the projection images were corrected using beam-stop array measurements and signal-to-thickness calibration. A post-reconstruction material decomposition (MD) technique was applied to obtain the partial density distributions of bentonite and water, from which the water content distributions were subsequently derived. The results were validated by physically slicing partially saturated bentonite samples and measuring the water content of the slices gravimetrically. Additionally, a previously developed deformation measurement-based X-ray tomography method was used to derive reference results. Comparing the results from MD with those from the other techniques demonstrated that DECT can yield quantitative estimates of 4D water content distribution in bentonite with reasonable accuracy in this experimental set-up. When testing the impact of correction methods on the results, it was found that both scattering and beam hardening must be corrected, as the post-reconstruction MD is sensitive to errors in spectral measurements.

High-resolution imaging is critical for the diagnosis, treatment planning, and postoperative monitoring of cerebral aneurysms, which affect up to 5% of the population and pose a significant risk of rupture and subarachnoid hemorrhage. Surgical clipping remains a definitive treatment option, but metallic clips can introduce substantial imaging artifacts, complicating posttreatment assessment. This review synthesizes current knowledge on the impact of aneurysm clip materials and designs on artifact generation and explores strategies for artifact mitigation. Conventional materials like titanium are favored for their biocompatibility and reduced ferromagnetism but still cause beam hardening, streak artifacts, and signal loss in CT and MRI scans. Emerging alternatives, including ceramics, composites, polymers, and bioresorbable clips, show promise in reducing artifacts while maintaining mechanical reliability. Innovations in clip design, such as fenestrated or low-profile models, further aid in minimizing imaging distortion. Advanced imaging methods, including dual-energy CT, iterative reconstruction algorithms, and metal artifact reduction software, demonstrate significant improvements in image quality but may introduce limitations such as increased processing demands or subtle anatomical distortions. Future directions emphasize the development of next-generation clip materials, robotic-assisted surgical approaches, and artificial intelligence-driven reconstruction techniques to further optimize visualization and patient safety. Continued research and multidisciplinary collaboration will be essential to translate these innovations into routine neurosurgical practice.

Medical implants, often made of dense materials, pose significant challenges to accurate computed tomography (CT) reconstruction, especially near implants due to beam hardening and partial-volume artifacts. Moreover, diagnostics involving implants often require separate visualization for implants and anatomy. In this work, we propose a approach for joint estimation of anatomy and implants as separate volumes using a mixed prior model. We leverage a learning-based prior for anatomy and a sparsity prior for implants to decouple the two volumes. In addition, a hybrid mono-polyenergetic forward model is employed to accommodate the spectral effects of implants, and a multiresolution object model is used to achieve high-resolution implant reconstruction. The reconstruction process alternates between diffusion posterior sampling for anatomy updates and classic optimization for implants and spectral coefficients. Evaluations were performed on emulated cardiac imaging with stent and spine imaging with pedicle screws. The structures of the cardiac stent with 0.25mm wires were clearly visualized in the implant images, whereas the blooming artifacts around the stent were effectively suppressed in the anatomical reconstruction. For pedicle screws, the proposed algorithm mitigated streaking and beam-hardening artifacts in the anatomy volume, demonstrating significant improvements in SSIM and PSNR compared with frequency-splitting metal artifact reduction and model-based reconstruction on slices containing implants. The proposed mixed prior model coupled with a hybrid spectral and multiresolution model can help to separate spatially and spectrally distinct objects that differ from anatomical features in single-energy CT, improving both image quality and separate visualization of implants and anatomy.

Dual-energy computed tomography (DECT) generates virtual monochromatic images (VMI) and material decomposition images (MDI), facilitating enhanced tissue contrast and quantitative material assessment. However, the accuracy of these measurements may be influenced by object size due to beam hardening and associated spectral changes. To evaluate the impact of object size on the accuracy of iodine quantification and CT numbers in virtual monochromatic images (VMI) using split-filter dual-energy CT (SFDE), and to compare its performance with sequential acquisition dual-energy CT (SADE). CT scans were performed on phantoms with diameters ranging from 16 to 36cm using both SFDE and SADE techniques. Virtual monochromatic images and material decomposition images were generated. CT numbers and iodine concentrations were measured from embedded iodine rods, and relative errors were calculated using the 16cm phantom as a reference. CT numbers in VMI obtained from SFDE exhibited increasing variability with larger phantom sizes, particularly at both low and high energy levels. Iodine quantification errors with SFDE exceeded 10% in all phantom sizes and reached approximately 60% in the 36cm phantom. In contrast, SADE consistently maintained measurement errors within 10%. Object size significantly influences the accuracy of CT numbers and iodine quantification using SFDE, with larger phantoms showing marked overestimation. These results suggest that careful interpretation is necessary when applying SFDE-based quantitative imaging in patients with larger object sizes.

Dual energy CT-based Radiomics for identification of myocardial focal scar and artificial beam-hardening.

Dual-energy computed tomography (DECT) has been widely used in acute clinical settings to add diagnostic confidence and accuracy in head and neck imaging. Given the complexity of the head and neck anatomy, delayed or inaccurate diagnosis of abnormalities involving the head and neck region can result in poor outcomes and possibly life-threatening consequences. This article aims to familiarize radiologists with the clinical applications and limitations of DECT in emergency head and neck imaging to maintain interpretative accuracy and improve patients' outcomes. Here, we demonstrate the profound capabilities of DECT for detecting and characterizing pathologies in the head and neck region with its superior abilities to differentiate materials, improve contrast enhancement, and reduce beam hardening artifacts. The robust imaging protocols and diverse post-processing algorithms of DECT enable radiologists to make diagnoses more quickly and accurately while accounting for suboptimal imaging from poor contrast opacification and/or beam hardening artifacts, unexpected pathologies, and reduction of unnecessary additional studies, and therefore, reduction of radiation dose and improvement of workflow in the emergency setting.

This article presents a novel electron beam hardening (EBH) process for C45 steel cylindrical specimens in an as-received state, utilizing continuous irradiation with power in the range of 720–2070 W and line scanning in the axial direction. The influence of operating parameters (i.e., electron beam current, workpiece velocity, scanning frequency, and focal length) on microhardness is examined using a one-factor-at-a-time technique. Scanning electron microscopy images reveal pronounced surface transformation hardening of C45 steel, resulting in martensite transformation and the formation of a pseudo-amorphous structure in the surface layer. The maximum surface microhardness obtained, HV_0.05=903, is three times greater than that achieved after turning (the step before EBH). The electron beam current and workpiece velocity significantly influence the thermal processes in the surface layers and, consequently, the microhardness. Based on the experimental results, the optimal ranges of the operating parameters have been defined.