Search Results (72)

In compressed sensing, it is believed that the L₀ norm minimization is the best way to enforce a sparse solution. However, the L₀ norm is difficult to implement in a gradient-based iterative image reconstruction algorithm. The total variation (TV) norm minimization is considered a proper substitute for the L₀ norm minimization. This paper points out that the TV norm is not powerful enough to enforce a piecewise-constant image. This paper uses the limited-angle tomography to illustrate the possibility of using the L₀ norm to encourage a piecewise-constant image. However, one of the drawbacks of the L₀ norm is that its derivative is zero almost everywhere, making a gradient-based algorithm useless. Our novel idea is to replace the zero value of the L₀ norm derivative with a zero-mean random variable. Computer simulations show that the proposed L₀ norm minimization outperforms the TV minimization. The novelty of this paper is the introduction of some randomness in the gradient of the objective function when the gradient is zero. The quantitative evaluations indicate the improvements of the proposed method in terms of the structural similarity (SSIM) and the peak signal-to-noise ratio (PSNR). Full article

Background: Two-dimensional periapical radiographs (PAs) only offer limited information regarding three-dimensional periodontal infrabony defects. In contrast, cone beam computed tomography (CBCT) enables visualization of the entire defect morphology. This study aimed to evaluate the agreement between CBCT and direct intrasurgical measurements (ISs) regarding the characteristics of infrabony defects, including measurements of defect depth, width, the type of defect (one-wall, two-wall, three-wall), and defect extension. Methods: Intrasurgical and radiographic assessments were performed by two calibrated examiners on 26 infrabony defects in 17 patients who underwent periodontal surgery. The defect depth, width, type, and extension were compared between intrasurgical observations and PA or CBCT findings. The CBCT assessment was performed mainly using axial reconstructions. Angle measurements were compared between CBCT and PAs. Results: The mean differences between CBCT and intrasurgical measurements were −0.11 ± 0.49 mm for depth and −0.07 ± 0.41 mm for width, with no significant differences. The ICC values were 0.938 and 0.923 for depth and width, respectively. The mean difference in width between PAs and ISs was significantly different (−0.36 ± 0.73 mm; p = 0.002). CBCT demonstrated high agreement with intrasurgical observations for defect type (κ = 0.819) and defect extension (κ = 0.855), while lower agreements were found for PAs. Conclusions: CBCT is a valid assessment modality for infrabony defects. It demonstrated strong agreement with ISs—as the gold standard—for depth and width measurements, and its agreement with ISs regarding defect type and extension appeared to surpass that of PAs. Full article

This study presents a comprehensive methodology for the detection and characterization of fractures in geological samples using X-ray computed tomography (CT). By combining convolution-based image processing techniques with advanced neural network-based segmentation, the proposed approach achieves high precision in identifying complex fracture networks. The method was applied to a marly limestone sample from the Maiolica Formation, part of the Umbria–Marche stratigraphic succession (Northern Apennines, Italy), a geological context where fractures often vary in size and contrast and are frequently filled with minerals such as calcite or clays, making their detection challenging. A critical part of the work involved addressing multiple sources of uncertainty that can impact fracture identification and measurement. These included the inherent spatial resolution limit of the CT system (voxel size of 70.69 μm), low contrast between fractures and the surrounding matrix, artifacts introduced by the tomographic reconstruction process (specifically the Radon transform), and noise from both the imaging system and environmental factors. To mitigate these challenges, we employed a series of preprocessing steps such as Gaussian and median filtering to enhance image quality and reduce noise, scanning from multiple angles to improve data redundancy, and intensity normalization to compensate for shading artifacts. The neural network segmentation demonstrated superior capability in distinguishing fractures filled with various materials from the host rock, overcoming the limitations observed in traditional convolution-based methods. Overall, this integrated workflow significantly improves the reliability and accuracy of fracture quantification in CT data, providing a robust and reproducible framework for the analysis of discontinuities in heterogeneous and complex geological materials. Full article

Over the last ten years, transcatheter tricuspid valve interventions (TTVIs) have emerged as effective options for symptomatic patients with moderate-to-severe tricuspid regurgitation (TR) who are at prohibitive surgical risk. Successful application of these therapies depends on a patient-tailored, multimodal imaging workflow. Transthoracic and transesophageal echocardiography remain the first-line diagnostic tools, rapidly stratifying TR severity, mechanism, and right ventricular function, and identifying cases requiring further evaluation. Cardiac computed tomography (CT) then provides anatomical detail—quantifying tricuspid annular dimension, leaflet tethering, coronary artery course, and venous access anatomy—to refine candidacy and simulate optimal device sizing and implantation angles. In patients with suboptimal echocardiographic windows or equivocal functional data, cardiovascular magnetic resonance (CMR) offers gold-standard quantification of RV volumes, ejection fraction, regurgitant volume, and tissue characterization to detect fibrosis. Integration of echo-derived parameters, CT anatomical notes, and CMR functional assessment enables the heart team to better select patients, plan procedures, and determine the optimal timing, thereby maximizing procedural success and minimizing complications. This review describes the current strengths, limitations, and future directions of multimodality imaging in comprehensive evaluations of TTVI candidates. Full article

The microscale solid and pore structures of waste is crucial for the bio-hydro-mechanical behaviors of landfilled municipal solid waste (MSW). The quantitative analysis of the structural characteristics of MSW is still limited. In this study, borehole MSW samples at different depths (i.e., 0 m, 2.5 m, 5 m, 7.5 m, 10 m, and 12.5 m) were drilled from a landfill. The waste composition and basic physical properties of these samples were tested in laboratory. Solid and pore structural characteristics were studied through computed tomography (CT) analysis. The results indicate that the ratio of cellulose content to lignin content (i.e., C/L) decreased from 0.85 to 0.47 with increasing depth. For solid particles, two-dimensional (2D) particles constituted the greatest fraction (60.22~72.16%), which showed a decrease with increasing depth. The deeper sample tended to have more fine particles. For pores, the void ratio decreased from 1.68 to 1.10 with increasing depth, with more small pore channels. Meanwhile, the average pore diameter coefficient (λ) decreased from 0.209 to 0.190, the pore angle (θ_e) decreased from 29.6° to 17.8°, the tortuosity (τ) increased from 1.129 to 1.184, and the connectivity (c_e) decreased from 12.0 to 4.1. These quantitative findings can further the understanding of fluid flow behaviors in landfilled waste. Full article

Background/Objectives: One of the surgical interventions applied in the cervical region is the pedicle screw method. The cervical pedicle screw is stronger than any other screw method; however, use of the cervical pedicle screw is limited due to the variability in the anatomy of the cervical vertebrae and the risks to the neurological and vascular structures in this region. This study aimed to determine the morphological features of subaxial cervical vertebrae of the adult Turkish population and to provide guidance for the pedicle screwing method. Methods: In our study, pedicle analyses were examined in the subaxial neck vertebrae of a total of 60 patients, 30 male and 30 female, using computed tomography images. In subaxial vertebrae (C3–C7), bilateral pedicle width, pedicle axis length, pedicle transverse angle, sagittal and transverse diameter of vertebral foramen, and the distance between two pedicles were measured. Results: Pedicle widths that did not fit the commonly used 3.5 mm pedicle screw were detected in both male and female patients. The mean bilateral pedicle width in male patients was found to be greater than in female patients. When the parameter results were compared according to the levels, it was found that the pedicle width, pedicle axis length, transverse diameter, and the distance between the two pedicles increased statistically significantly. Conclusions: We think that the data obtained from the study will help determine the appropriate screwing (screw selection) in subaxial vertebra pedicle surgery and increase the success of the surgical procedure. Full article

Neurodegenerative diseases (NDDs) that are characterized by the accumulation of alpha-synuclein (α-syn) aggregates in both neurons and the non-neuronal cells of the brain are called synucleinopathies. The most common synucleinopathies includes Parkinson’s disease (PD), Parkinson’s disease dementia (PDD), multiple system atrophy (MSA), and dementia with Lewy bodies (DLB). Significant progress has been made in the development of positron emission tomography (PET) radiotracers for synucleinopathies, yielding several α-syn tracers that have entered clinical studies. However, selective α-syn imaging still faces inherent challenges. This review provides a comprehensive overview of the progress in α-syn PET radiotracers from three angles: Alzheimer’s disease (AD)-derived scaffolds, representative compound scaffolds and analogs, and the identification of α-syn tracers through high-throughput screening (HTS). We discuss the characteristics, advantages, and limitations of the tracers for preclinical and clinical application. Finally, future directions in the development of radioligands for proteinopathies are discussed. There is no clinical available PET radiotracer for imaging α-syn aggregates, but these advances have laid a key foundation for non-invasive α-syn imaging and early diagnosis of synucleinopathies. Full article

Background/Objectives: Hindfoot valgus malalignment, characterized by the lateral deviation of the calcaneus and medial tilting of the talus, disrupts hindfoot biomechanics and increases strain on subtalar joint. This study evaluates weightbearing and non-weightbearing imaging modalities to identify dynamic alignment changes and their diagnostic implications. This study aims to (1) quantify changes in subtalar joint parameters between non-weightbearing computed tomography (NWBCT) and weightbearing computed tomography (WBCT) in patients with hindfoot valgus; (2) evaluate correlations between WBCT and standard radiographic parameters; and (3) identify radiographic predictors of subtalar joint status during weightbearing. Methods: We reviewed 70 patients with confirmed hindfoot valgus malalignment (hindfoot valgus angle >5°), identified through radiographic measurements. Of these, 32 underwent both NWBCT and WBCT, while 38 underwent WBCT alone. Hindfoot alignment angle (HAA) and hindfoot alignment ratio (HAR) were measured on hindfoot alignment radiographs, while heel valgus angle (HVA), talocalcaneal distance (TCD), subtalar joint subluxation (SL) and calcaneofibular distance (CF) were assessed on CT. Results: WBCT revealed significant increases in HVA and SL (both, p < 0.001) and decreases in TCD and CF (p < 0.001 and p = 0.002, respectively) compared to NWBCT, reflecting dynamic subtalar joint changes under weightbearing conditions. Receiver operating characteristic (ROC) analysis identified hindfoot alignment angle (HAA) as the most reliable predictor of talocalcaneal osseous contact, with a cutoff value of >9.25° based on Youden’s index, yielding a sensitivity of 73% and specificity of 81.8%. Inter- and intra-observer reliabilities for all parameters were excellent (ICC > 0.81). Conclusions: WBCT provides critical insights into subtalar joint dynamics under physiological loads, surpassing NWBCT in assessing weightbearing-induced alignment changes. Although standard radiographic parameters, particularly HAA, can serve as reliable, cost-effective predictors of subtalar joint pathology in resource-limited settings, WBCT should still be preferred when available, especially in patients with significant malalignment or when detailed dynamic evaluation is needed to guide clinical decision-making. Full article

Background and Objectives: Single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is a well-established technique for evaluating myocardial perfusion and function in patients with suspected or known coronary artery disease. While conventional dual-detector SPECT scanners have limitations in spatial resolution and photon detection sensitivity, recent advancements, including full-ring solid-state cadmium zinc telluride (CZT) detectors, offer enhanced image quality and improved diagnostic accuracy. This study aimed to compare the performance of Veriton-CT, a full-ring CZT SPECT system, with GE Discovery 530c, a dedicated cardiac fixed-angle gamma camera, in myocardial perfusion imaging and their correlation with coronary angiography findings. Materials and Methods: This was a prospective study that analyzed 21 patients who underwent MPI at the Department of Nuclear Medicine, Lithuanian University of Health Sciences, Kauno Klinikos. A one-day stress–rest protocol using 99mTc-Sestamibi was employed, with stress testing performed via bicycle ergometry or pharmacological induction. MPI was first conducted using GE Discovery 530c (GE Health Care, Boston, MA, USA), followed by imaging on Veriton-CT, which included low-dose CT for attenuation correction. The summed stress score (SSS), summed rest score (SRS), and summed difference score (SDS) were analyzed and compared between both imaging modalities. Coronary angiography results were retrospectively collected, and lesion-based analysis was performed to assess the correlation between imaging results and the presence of significant coronary artery stenosis (≥35% and ≥70% narrowing). Image quality and the certainty of distinguishing the inferior myocardial wall from extracardiac structures were also evaluated by two independent researchers with differing levels of experience. Results: Among the 14 patients included in the final analysis, Veriton-CT was more likely to classify MPI scans as normal (64.3%) compared to GE Discovery 530c (28.6%). Additionally, Veriton-CT provided a better assessment of the right coronary artery (RCA) basin, showing greater agreement with coronary angiography findings than GE Discovery 530c, although the difference was not statistically significant. No significant differences in lesion overlap were observed for the left anterior descending artery (LAD) or left circumflex artery (LCx) basins. Furthermore, the image quality assessment revealed slightly better delineation of extracardiac structures using Veriton-CT (Spectrum Dynamics Medical, Caesarea, Israel), particularly when evaluated by an experienced researcher. However, no significant difference was observed when assessed by a less experienced observer. Conclusions: Our findings suggest that Veriton-CT, with its full-ring CZT detector system, may offer advantages over fixed-angle gamma cameras in improving image quality and reducing attenuation artifacts in MPI. Although the difference in correlations with coronary angiography findings was not statistically significant, Veriton-CT showed a trend toward better agreement, particularly in the RCA basin. These results indicate that full-ring SPECT imaging could improve the diagnostic accuracy of non-invasive MPI, potentially reducing the need for unnecessary invasive angiography. Further studies with larger patient cohorts are required to confirm these findings and evaluate the clinical impact of full-ring SPECT technology in myocardial perfusion imaging. Full article

Background/Objectives: Intraoral (IO) radiographs are critical for endodontic diagnostics, yet conventional orthoradial imaging often results in superimposition, limiting the visibility of individual root canals. Maxillary first premolars pose challenges due to their anatomical characteristics and positioning within the dental arch. This study aimed to retrospectively analyze cone-beam computed tomography (CBCT) data to determine the horizontal X-ray beam angulations for maxillary first premolars at which root canals overlap and neighboring tooth superimposition occur, providing clinically relevant guidance for optimizing IO radiographic techniques. Methods: CBCT scans from 85 patients were analyzed using ImageJ software to measure the angles at which maxillary first premolar root canals overlap or become obscured by adjacent teeth. The mean angles for canal overlap and neighboring tooth superimposition were determined. Statistical analysis was performed using SPSS Version 29.0, and the level of significance was set to 5%. Results: The mean angle for root canal overlap was 93.56° (±10.08). The angles at which neighboring teeth began to superimpose were 124.38° (±9.91) for the distal contour of the canine and 63.46° (±9.38) for the mesial root contour of the second premolar. No significant differences were observed between apical and coronal measurements for root canal overlap but tapering of the roots led to significant differences in neighboring tooth superimposition (p < 0.05). Conclusions: A mesial beam shift within a calculated safe corridor (98.5–129.5°) optimizes canal separation without superimposition from adjacent teeth. For ideal visualization, a mesial angulation close to 40° is recommended. These findings support improved IO radiographic techniques while minimizing the risk of retakes in adherence to the ALARA principle. Full article

Macular Telangiectasia (MacTel) is a rare retinal vascular disorder, with Type 3a MacTel being a distinct form characterized by retinal ischemia with the classical findings of MacTel, such as juxtafoveal telangiectasis, right-angled venules, and deep capillary plexus involvement without central nervous system findings. This case presents a novel X-shaped lesion pattern and ischemic features, expanding the known imaging spectrum of MacTel. A 53-year-old male with diabetes and a history of aripiprazole use presented with persistent blurred vision, a black curtain sensation, and metamorphopsia in the right eye. Visual acuity was 0.8 in the right eye and 1.0 in the left. A multimodal imaging approach, including fundus photography, fundus autofluorescence (FAF), fluorescein angiography (FFA), optical coherence tomography (OCT), and optical coherence tomography angiography (OCTA), was used to evaluate structural and vascular abnormalities. Fundus examination revealed an X-shaped hypopigmented lesion with central pigmentation. FAF showed hypoautofluorescence, indicating chronic RPE loss, and no loss of foveal autofluorescence was observed. FFA demonstrated progressive hyperfluorescence with perifoveal aneurysmal and telangiectatic vessels, along with a slightly enlarged foveal avascular zone (FAZ), suggesting ischemic involvement. OCT revealed intraretinal cysts, a disruption of the ellipsoid zone and external limiting membrane, pigment epithelial detachment, and increased choroidal backscattering. OCTA confirmed right-angled venules, aneurysmal telangiectatic vessels, and localized ischemia predominantly affecting the deep capillary plexus. This case highlights a rare variant of Type 3a MacTel with a unique X-shaped lesion. The presence of juxtafoveal telangiectasis, vascular occlusion, right-angled venules, and deep capillary plexus changes supports the diagnosis. Multimodal imaging played a critical role in characterizing the disease and differentiating it from other macular disorders, contributing to an expanded understanding of the clinical and imaging spectrum of MacTel. Full article

This paper investigates the effects of particle morphology (PM) and particle size distribution (PSD) on the micro-macro mechanical behaviours of granular soils through a novel X-ray micro-computed tomography (μCT)-based discrete element method (DEM) technique. This technique contains the grain-scale property extraction by the X-ray μCT, DEM parameter calibration by the one-to-one mapping technique, and the massive derivative DEM simulations. In total, 25 DEM samples were generated with a consideration of six PSDs and four PMs. The effects of PSD and PM on the micro-macro mechanical behaviours were carefully investigated, and the coupled effects were highlighted. It is found that (a) PM plays a significant role in the micro-macro mechanical responses of granular soils under triaxial shear; (b) the PSD uniformity can enhance the particle morphology effect in dictating the peak deviatoric stress, maximum volumetric strain, contact-based coordination number, fabric evolution, and shear band formation, while showing limited influences in the maximum dilation angle and particle-based coordination number; (c) with the same PSD uniformity and PM degree, the mean particle volume shows minimal effects on the macro-micro mechanical behaviours of granular soils as well as the particle morphology effects. Full article

Objective: Pars fractures are a common cause of lower back pain, especially among young individuals. Although computed tomography (CT) and magnetic resonance imaging (MRI) scanning are commonly used in developed regions, traditional radiography remains the main diagnostic method in many developing countries. This study assessed whether the standard radiographic angles suggested in textbooks are optimal for an Asian population since Asian groups have lower lumbar lordosis. This study found a 35° angle to be the most effective angle for lumbar oblique X-ray imaging. Additionally, the potential for a customized positioning auxiliary device was examined to improve image quality and reduce patient discomfort in cost-sensitive healthcare settings like Taiwan’s single-payer system. Methods: A total of 100 participants underwent lumbar oblique radiography using a specially designed footboard with angle markings. Radiologists evaluated 600 images based on waist-to-hip ratio (WHR) and body mass index to identify the optimal angulation for various body types. Results: For individuals with a WHR of 0.85, a 35° angle provided superior image quality, while 45° was more effective for slimmer patients. This optimized approach indicates the cost-effectiveness and diagnostic value of traditional X-ray imaging. Conclusions: The 35° angulation standardizes lumbar X-ray imaging for an Asian cohort, reducing repeat scans and improving accuracy. Using a positioning device further enhances image quality and patient comfort, supporting the clinical utility of traditional radiography in resource-limited environments. Full article

Patellar pathologies are a common cause of knee dysfunction, with Patellofemoral Pain Syndrome (PFPS) alone responsible for 25% of knee-related visits to sports medicine clinics. Non-traumatic conditions, while often overlooked, can also lead to significant discomfort and functional limitations, highlighting the importance of accurate and timely diagnosis for effective management and prevention of complications. This pictorial review examines the radiologic characteristics of various non-traumatic patellar disorders, focusing on imaging modalities such as radiography, computed tomography (CT), and magnetic resonance imaging (MRI). Key diagnostic markers, including patellar tilt, tibial tuberosity–trochlear groove distance (TT-TG), and congruence angle (CA), are discussed for their significance in non-traumatic pathology identification. Furthermore, this review highlights specific radiologic features for a range of non-traumatic patellar conditions, including patellar tendinopathy, chondromalacia patellae, and trochlear dysplasia, emphasizing how distinct radiologic findings facilitate precise diagnosis and clinical assessment. Ultimately, it provides a practical guide for clinicians in diagnosing non-traumatic patellar pathologies through a comprehensive review of key radiologic features while also discussing advancements in imaging technologies and management strategies to support accurate diagnosis and effective clinical decision-making. Full article

In the fabrication of optical polymer-based components, such as diffractive gratings and waveguides, high throughput and high precision are required. The non-destructive evaluation of these complex polymer-based structures is a significant challenge. Different measurement techniques can measure the structure geometry directly or via its functionality indirectly. This study investigates various measurement techniques aimed at assessing these structures from 200 nm up to 20 µm. Environmental scanning electron microscopy (ESEM), white light interferometry (WLI), atomic force microscopy (AFM), micro computed tomography (µCT), optical coherence tomography (OCT), phase contrast microscopy (PCM), and Mueller matrix ellipsometry (MME) are investigated for their practical limits of lateral resolution and aspect ratio. The impact of the specimens’ complexity factors, including structure width and aspect ratio, on measurement quality is discussed. A particular focus of this study is on the suitability of different measurement systems for evaluating undercuts and enclosed structures while considering structure size, slant angle, and cover thickness. The aim is to discuss the specific advantages of the individual measurement systems and their application areas in order to be able to quickly select suitable measurement systems for a non-destructive evaluation of polymer-based micro and nanostructures. Full article