scholarly journals Evaluating a calcium-aware kernel for CT CAC scoring with varying surrounding materials and heart rates: a dynamic phantom study

2021 ◽  
Author(s):  
Niels R. van der Werf ◽  
Ronald Booij ◽  
Bernhard Schmidt ◽  
Thomas G. Flohr ◽  
Tim Leiner ◽  
...  
Keyword(s):  
Coronary Artery ◽  
Soft Tissue ◽  
Patient Specific ◽  
Reconstruction Technique ◽  
Ct Reconstruction ◽  
Raw Data ◽  
Heart Rates ◽  
Tissue Equivalent ◽  
Tin Filtration ◽  
Reconstruction Kernel

Abstract Objectives The purpose of this study was twofold. First, the influence of a novel calcium-aware (Ca-aware) computed tomography (CT) reconstruction technique on coronary artery calcium (CAC) scores surrounded by a variety of tissues was assessed. Second, the performance of the Ca-aware reconstruction technique on moving CAC was evaluated with a dynamic phantom. Methods An artificial coronary artery, containing two CAC of equal size and different densities (196 ± 3, 380 ± 2 mg hydroxyapatite cm−3), was moved in the center compartment of an anthropomorphic thorax phantom at different heart rates. The center compartment was filled with mixtures, which resembled fat, water, and soft tissue equivalent CT numbers. Raw data was acquired with a routine clinical CAC protocol, at 120 peak kilovolt (kVp). Subsequently, reduced tube voltage (100 kVp) and tin-filtration (150Sn kVp) acquisitions were performed. Raw data was reconstructed with a standard and a novel Ca-aware reconstruction technique. Agatston scores of all reconstructions were compared with the reference (120 kVp) and standard reconstruction technique, with relevant deviations defined as > 10%. Results For all heart rates, Agatston scores for CAC submerged in fat were comparable to the reference, for the reduced-kVp acquisition with Ca-aware reconstruction kernel. For water and soft tissue, medium-density Agatston scores were again comparable to the reference for all heart rates. Low-density Agatston scores showed relevant deviations, up to 15% and 23% for water and soft tissue, respectively. Conclusion CT CAC scoring with varying surrounding materials and heart rates is feasible at patient-specific tube voltages with the novel Ca-aware reconstruction technique. Key Points • A dedicated calcium-aware reconstruction kernel results in similar Agatston scores for CAC surrounded by fatty materials regardless of CAC density and heart rate. • Application of a dedicated calcium-aware reconstruction kernel allows for radiation dose reduction. • Mass scores determined with CT underestimated physical mass.

scholarly journals Fluid–structure interactions (FSI) based study of low-density lipoproteins (LDL) uptake in the left coronary artery

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Xueping Chen ◽  
Jian Zhuang ◽  
Huanlei Huang ◽  
Yueheng Wu
Keyword(s):  
Shear Stress ◽  
Coronary Artery ◽  
Left Coronary Artery ◽  
Arterial Wall ◽  
Low Density Lipoproteins ◽  
Patient Specific ◽  
Low Density ◽  
Fluid Structure ◽  
Flowing Blood ◽  
Stress Dependent

AbstractThe purpose of this study is to compare the effect of the different physical factors on low-density lipoproteins (LDL) accumulation from flowing blood to the arterial wall of the left coronary arteries. The three-dimensional (3D) computational model of the left coronary arterial tree is reconstructed from a patient-specific computed tomography angiography (CTA) image. The endothelium of the coronary artery is represented by a shear stress dependent three-pore model. Fluid–structure interaction ($$FSI$$ FSI ) based numerical method is used to study the LDL transport from vascular lumen into the arterial wall. The results show that the high elastic property of the arterial wall decreases the complexity of the local flow field in the coronary bifurcation system. The places of high levels of LDL uptake coincide with the regions of low wall shear stress. In addition, hypertension promotes LDL uptake from flowing blood in the arterial wall, while the thickened arterial wall decreases this process. The present computer strategy combining the methods of coronary CTA image 3D reconstruction, $$FSI$$ FSI simulation, and three-pore modeling was illustrated to be effective on the simulation of the distribution and the uptake of LDL. This may have great potential for the early prediction of the local atherosclerosis lesion in the human left coronary artery.

Guided image filtering based ℓ0 gradient minimization for limited-angle CT image reconstruction

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Tianyi Wang ◽  
Chengxiang Wang ◽  
Kequan Zhao ◽  
Wei Yu ◽  
Min Huang
Keyword(s):  
Iteration Process ◽  
Real Data ◽  
Image Filtering ◽  
Reconstruction Technique ◽  
Ct Reconstruction ◽  
Imaging Device ◽  
Practical Applications ◽  
Guided Image Filtering ◽  
Simultaneous Algebraic Reconstruction Technique ◽  
Limited Angle

Abstract Limited-angle computed tomography (CT) reconstruction problem arises in some practical applications due to restrictions in the scanning environment or CT imaging device. Some artifacts will be presented in image reconstructed by conventional analytical algorithms. Although some regularization strategies have been proposed to suppress the artifacts, such as total variation (TV) minimization, there is still distortion in some edge portions of image. Guided image filtering (GIF) has the advantage of smoothing the image as well as preserving the edge. To further improve the image quality and protect the edge of image, we propose a coupling method, that combines ℓ 0 {\ell_{0}} gradient minimization and GIF. An intermediate result obtained by ℓ 0 {\ell_{0}} gradient minimization is regarded as a guidance image of GIF, then GIF is used to filter the result reconstructed by simultaneous algebraic reconstruction technique (SART) with nonnegative constraint. It should be stressed that the guidance image is dynamically updated as the iteration process, which can transfer the edge to the filtered image. Some simulation and real data experiments are used to evaluate the proposed method. Experimental results show that our method owns some advantages in suppressing the artifacts of limited angle CT and in preserving the edge of image.

scholarly journals True Kinematic Alignment Is Applicable in 44% of Patients Applying Restrictive Indication Criteria—A Retrospective Analysis of 111 TKA Using Robotic Assistance

2021 ◽  
Vol 11 (7) ◽  
pp. 662
Author(s):  
Kim Huber ◽  
Bernhard Christen ◽  
Sarah Calliess ◽  
Tilman Calliess
Keyword(s):  
Soft Tissue ◽  
Retrospective Analysis ◽  
Patient Specific ◽  
Kinematic Alignment ◽  
Postoperative Phase ◽  
Robotic Assistance ◽  
Component Position ◽  
Joint Stability ◽  
Robotic Assisted ◽  
Primary Tkas

Introduction: Image-based robotic assistance appears to be a promising tool for individualizing alignment in total knee arthroplasty (TKA). The patient-specific model of the knee enables a preoperative 3D planning of component position. Adjustments to the individual soft-tissue situation can be done intraoperatively. Based on this, we have established a standardized workflow to implement the idea of kinematic alignment (KA) for robotic-assisted TKA. In addition, we have defined limits for its use. If these limits are reached, we switch to a restricted KA (rKA). The aim of the study was to evaluate (1) in what percentage of patients a true KA or an rKA is applicable, (2) whether there were differences regarding knee phenotypes, and (3) what the differences of philosophies in terms of component position, joint stability, and early patient outcome were. Methods: The study included a retrospective analysis of 111 robotic-assisted primary TKAs. Based on preoperative long leg standing radiographs, the patients were categorized into a varus, valgus, or neutral subgroup. Initially, all patients were planned for KA TKA. When the defined safe zone had been exceeded, adjustments to an rKA were made. Intraoperatively, the alignment of the components and joint gaps were recorded by robotic software. Results and conclusion: With our indication for TKA and the defined boundaries, “only” 44% of the patients were suitable for a true KA with no adjustments or soft tissue releases. In the varus group, it was about 70%, whereas it was 0% in the valgus group and 25% in the neutral alignment group. Thus, significant differences with regard to knee morphotypes were evident. In the KA group, a more physiological knee balance reconstructing the trapezoidal flexion gap (+2 mm on average laterally) was seen as well as a closer reconstruction of the surface anatomy and joint line in all dimensions compared to rKA. This resulted in a higher improvement in the collected outcome scores in favor of KA in the very early postoperative phase.

Role of Plaque Morphology in Altering the Flow Characteristics in Diseased Coronary Artery

2012 ◽  
Author(s):  
Carlos Moreno ◽  
Kiran Bhaganagar
Keyword(s):  
Coronary Artery ◽  
Nonlinear Response ◽  
Flow Characteristics ◽  
Proximal Region ◽  
Patient Specific ◽  
Plaque Morphology ◽  
Mean Velocity ◽  
Peak Location ◽  
The Mean

Patient specific simulations of a single patient based on an accurate representation of the plaque in a diseased coronary artery with 35% stenosis are performed to understand the effect of inlet forcing frequency and amplitude on the wall shear stress (WSS). Numerical simulations are performed with unsteady flow conditions in a laminar regime. The results have revealed that at low amplitudes, WSS is insensitive to forcing frequency and is it in phase with Q. The maximum WSS is observed at the proximal region of the stenosis, and WSS has highest negative values at the peak location of the stenosis. For higher pulsatile amplitude (a > 1.0), WSS exhibits a strong sensitivity with forcing frequencies. At higher forcing frequency the WSS exhibits nonlinear response to the inlet forcing frequency. Furthermore, significant differences in the mean velocity profile are observed during maximum and minimum volumetric flow rates.

scholarly journals Design and Production of Two-Piece Thyroid-Neck Phantom by the Concurrent Use of Epoxy Resin and Poly(Methyl Methacrylate) Soft Tissue Equivalent Materials

2018 ◽  
Vol 8 (2) ◽  
Author(s):  
M Karimi ◽  
H Mostaghimi ◽  
S. F Shams ◽  
A R Mehdizadeh
Keyword(s):  
Soft Tissue ◽  
Methyl Methacrylate ◽  
Epoxy Resin ◽  
Attenuation Coefficients ◽  
Poly Methyl Methacrylate ◽  
Tissue Equivalent ◽  
Concurrent Use ◽  
Human Soft Tissue ◽  
Mass Attenuation Coefficients ◽  
Mass Attenuation

The aim of this report is to present a new two-piece thyroid-neck phantom produced by the concurrent use of epoxy resin and poly(methyl methacrylate) (PMMA: plexiglass) soft tissue equivalent materials. Accordingly, mass attenuation coefficients of the epoxy resin and the plexiglass compounds were obtained from simulation (NIST XCOM 3.1) and measurements (practical dosimetry) and compared to those related to human soft tissue (ICRU 44). The thyroid-neck phantom and thyroid gland dimensions were derived from scientific references and the atlas of human anatomy, respectively. The thyroid phantom was designed by CATIA V5R16 software and produced by the epoxy resin compound by three-dimensional printer. Other organs were designed by ProNest software and made by the plexiglass sheets by CNC laser cutting machine. The mass attenuation coefficients for the epoxy resin (50 keV- 20 MeV) and the plexiglass (0-20 MeV) were comparable to human soft tissue (ICRU 44), all with standard relative deviation beneath 5%. In addition, the SPECT images indicated the similarity between human thyroid tissue and its phantom. In conclusion, this study proves the feasibility and reliability of epoxy resin application in the production of two-piece thyroid-neck phantom. This phantom can be applied in the calibration of gamma camera systems, dosimetry and gamma spectrometry in the nuclear medicine field.

scholarly journals Biomechanical modeling of knee for specific patients with chronic anterior cruciate ligament injury

2013 ◽  
Vol 10 (1) ◽  
pp. 525-545 ◽  
Author(s):  
Nenad Filipovic ◽  
Velibor Isailovic ◽  
Dalibor Nikolic ◽  
Aleksandar Peulic ◽  
Nikola Mijailovic ◽  
...  
Keyword(s):  
Gait Analysis ◽  
Acl Reconstruction ◽  
Cruciate Ligament ◽  
Biomechanical Model ◽  
Element Model ◽  
Gait Pattern ◽  
Von Mises Stress ◽  
Ligament Injury ◽  
Patient Specific ◽  
Reconstruction Technique

In this study we modeled a patient specific 3D knee after anterior cruicate ligament (ACL) reconstruction. The purpose of the ACL reconstruction is to achieve stability in the entire range of motion of the knee and the establishment of the normal gait pattern. We present a new reconstruction technique that generates patient-specific 3D knee models from patient?s magnetic resonant images (MRIs). The motion of the ACL reconstruction patients is measured by OptiTrack system with six infrared cameras. Finite element model of bones, cartilage and meniscus is used for determination stress and strain distribution at different body postures during gait analysis. It was observed that the maximum effective von Mises stress distribution up to 8 MPa occurred during 30% of the gait cycle on the meniscus. The biomechanical model of the knee joint during gait analysis can provide insight into the underlying mechanisms of knee function after ACL reconstruction.

A content-adaptive unstructured grid based regularized CT reconstruction method with a SART-type preconditioned fixed-point proximity algorithm

2022 ◽  
Author(s):  
Yun Chen ◽  
Yao Lu ◽  
Xiangyuan Ma ◽  
Yuesheng Xu
Keyword(s):  
Integral Equation ◽  
Fixed Point ◽  
Optimization Problem ◽  
Unstructured Grid ◽  
Reconstruction Technique ◽  
Reconstruction Method ◽  
Ct Reconstruction ◽  
Image Domain ◽  
Computational Costs ◽  
Content Adaptive

Abstract The goal of this study is to develop a new computed tomography (CT) image reconstruction method, aiming at improving the quality of the reconstructed images of existing methods while reducing computational costs. Existing CT reconstruction is modeled by pixel-based piecewise constant approximations of the integral equation that describes the CT projection data acquisition process. Using these approximations imposes a bottleneck model error and results in a discrete system of a large size. We propose to develop a content-adaptive unstructured grid (CAUG) based regularized CT reconstruction method to address these issues. Specifically, we design a CAUG of the image domain to sparsely represent the underlying image, and introduce a CAUG-based piecewise linear approximation of the integral equation by employing a collocation method. We further apply a regularization defined on the CAUG for the resulting illposed linear system, which may lead to a sparse linear representation for the underlying solution. The regularized CT reconstruction is formulated as a convex optimization problem, whose objective function consists of a weighted least square norm based fidelity term, a regularization term and a constraint term. Here, the corresponding weighted matrix is derived from the simultaneous algebraic reconstruction technique (SART). We then develop a SART-type preconditioned fixed-point proximity algorithm to solve the optimization problem. Convergence analysis is provided for the resulting iterative algorithm. Numerical experiments demonstrate the outperformance of the proposed method over several existing methods in terms of both suppressing noise and reducing computational costs. These methods include the SART without regularization and with quadratic regularization on the CAUG, the traditional total variation (TV) regularized reconstruction method and the TV superiorized conjugate gradient method on the pixel grid.

Correlation of Soft Tissue Swelling and Timing to Surgery With Acute Wound Complications for Operatively Treated Ankle and Other Lower Extremity Fractures

2019 ◽  
Vol 40 (5) ◽  
pp. 526-536 ◽  
Author(s):  
Matthew D. Riedel ◽  
Amber Parker ◽  
Mingxin Zheng ◽  
Jorge Briceno ◽  
Steven J. Staffa ◽  
...  
Keyword(s):  
Risk Factors ◽  
Soft Tissue ◽  
Lower Extremity ◽  
Tobacco Use ◽  
Wound Complication ◽  
Timing Of Surgery ◽  
Ankle Fractures ◽  
Patient Specific ◽  
Wound Complications ◽  
Heel Pad

Background: Considerable debate exists regarding how soft-tissue edema should influence timing of surgery for ankle and other lower extremity fractures. Assessment of swelling is subjective, and timing varies among surgeons. However, timing of surgery is one of the few modifiable factors in fracture care. Ultrasonography can objectively measure swelling and help determine optimal timing. The purposes of this study were to determine whether objective measures of swelling, timing to surgery, and patient-specific risk factors correlated with wound complications and to try to create a prediction model for postoperative wound complications based on identified modifiable and nonmodifiable risk factors. Methods: Patients with closed ankle and other lower extremity fractures requiring surgery with an uninjured, contralateral extremity were included. Demographic information and sonographic measurements on both lower extremities were obtained pre-operatively. Subjects were followed for 3 months and wound complications were documented. A predictive algorithm of independent risk factors was constructed, determining wound complication risk. Given that patients with ankle fractures made up the majority of the study cohort (75/93 or 80%), a separate statistical analysis was performed on this group. A total of 93 subjects completed the study, with 75/93 sustaining ankle fractures. Results: Overall wound complication rate was 18.3%. Timing to surgery showed no correlation with wound complications. A heel-pad edema index >1.4 was independently associated with wound complications. Subgroup analysis of ankle fractures demonstrated a 3.4× increase in wound complications with a heel-pad edema index >1.4. Tobacco history and BMI >25 were independent predictors of wound complications. An algorithm was established based on heel-pad edema index, BMI >25, and tobacco history. Patients with none of the 3 factors had a 3% probability of a wound complication. Patients with 1/3, 2/3 and 3/3 factors had a 12-36%, 60-86% and 96% probability of a wound complication, respectively. Conclusions: Timing to surgery had no correlation with wound complications. Heel-pad edema index >1.4, BMI >25, and tobacco-use correlated with wound complications. When separately analyzing the cohort that sustained ankle fractures, the heel-pad edema index of >1.4 was still demonstrated to be predictive of wound complications corresponding to a 3.4× increase in wound complication rates (11.1% vs 37.5%). Risk of wound complications significantly increased with each factor. In patients with increased BMI and/or tobacco use, resolution of heel edema may significantly reduce wound complications in lower extremity trauma. Level of Evidence: Level II, prognostic, prospective cohort study.

scholarly journals Effect of Reconstruction Algorithm on the Identification of 3D Printing Polymers Based on Hyperspectral CT Technology Combined with Artificial Neural Network

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1963 ◽  
Author(s):  
Zheng Fang ◽  
Renbin Wang ◽  
Mengyi Wang ◽  
Shuo Zhong ◽  
Liquan Ding ◽  
...  
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
3D Printing ◽  
Principal Components ◽  
Reconstruction Technique ◽  
Ct Reconstruction ◽  
Training Set ◽  
X Ray ◽  
Test Sets ◽  
Artificial Neural

Hyperspectral X-ray CT (HXCT) technology provides not only structural imaging but also the information of material components therein. The main purpose of this study is to investigate the effect of various reconstruction algorithms on reconstructed X-ray absorption spectra (XAS) of components shown in the CT image by means of HXCT. In this paper, taking 3D printing polymer as an example, seven kinds of commonly used polymers such as thermoplastic elastomer (TPE), carbon fiber reinforced polyamide (PA-CF), acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), ultraviolet photosensitive resin (UV9400), polyethylene terephthalate glycol (PETG), and polyvinyl alcohol (PVA) were selected as samples for hyperspectral CT reconstruction experiments. Seven kinds of 3D printing polymer and two interfering samples were divided into a training set and test sets. First, structural images of specimens were reconstructed by Filtered Back-Projection (FBP), Algebra Reconstruction Technique (ART) and Maximum-Likelihood Expectation-Maximization (ML-EM). Secondly, reconstructed XAS were extracted from the pixels of region of interest (ROI) compartmentalized in the images. Thirdly, the results of principal component analysis (PCA) demonstrated that the first four principal components contain the main features of reconstructed XAS, so we adopted Artificial Neural Network (ANN) trained by the reconstructed XAS expressed by the first four principal components in the training set to identify that the XAS of corresponding polymers exist in both of test sets from the training set. The result of ANN displays that FBP has the best performance of classification, whose ten-fold cross-validation accuracy reached 99%. It suggests that hyperspectral CT reconstruction is a promising way of getting image features and material features at the same time, which can be used in medical imaging and nondestructive testing.

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