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https://www.readbyqxmd.com/read/28629559/prospective-intra-individual-comparison-of-standard-dose-versus-reduced-dose-thoracic-ct-using-hybrid-and-pure-iterative-reconstruction-in-a-follow-up-cohort-of-pulmonary-nodules-effect-of-detectability-of-pulmonary-nodules-with-lowering-dose-based-on-nodule
#1
Varut Vardhanabhuti, Chun-Lap Pang, Sean Tenant, James Taylor, Christopher Hyde, Carl Roobottom
OBJECTIVES: To determine the diagnostic accuracy of lung nodule detection in thoracic CT using 2 reduced dose protocols comparing 3 available CT reconstruction algorithms (filtered back projection-FBP, adaptive statistical reconstruction-ASIR and model-based iterative reconstruction-MBIR) in a western population. MATERIALS AND METHODS: A prospective single-center study recruited 98 patients with written consent. Standard dose (STD) thoracic CT followed by 2 reduced-dose protocols using automatic tube current modulation (RD1) and fixed tube current (RD2) were performed and reconstructed with FBP, ASIR and MBIR with subsequent diagnostic accuracy analysis for nodule detection...
June 2017: European Journal of Radiology
https://www.readbyqxmd.com/read/28629554/emphysema-quantification-and-lung-volumetry-in-chest-x-ray-equivalent-ultralow-dose-ct-intra-individual-comparison-with-standard-dose-ct
#2
Michael Messerli, Thorsten Ottilinger, René Warschkow, Sebastian Leschka, Hatem Alkadhi, Simon Wildermuth, Ralf W Bauer
OBJECTIVES: To determine whether ultralow dose chest CT with tin filtration can be used for emphysema quantification and lung volumetry and to assess differences in emphysema measurements and lung volume between standard dose and ultralow dose CT scans using advanced modeled iterative reconstruction (ADMIRE). METHODS: 84 consecutive patients from a prospective, IRB-approved single-center study were included and underwent clinically indicated standard dose chest CT (1...
June 2017: European Journal of Radiology
https://www.readbyqxmd.com/read/28622671/low-dose-ct-with-a-residual-encoder-decoder-convolutional-neural-network-red-cnn
#3
Hu Chen, Yi Zhang, Mannudeep K Kalra, Feng Lin, Yang Chen, Peixo Liao, Jiliu Zhou, Ge Wang
Given the potential risk of X-ray radiation to the patient, low-dose CT has attracted a considerable interest in the medical imaging field. Currently, the main stream low-dose CT methods include vendor-specific sinogram domain filtration and iterative reconstruction algorithms, but they need to access raw data whose formats are not transparent to most users. Due to the difficulty of modeling the statistical characteristics in the image domain, the existing methods for directly processing reconstructed images cannot eliminate image noise very well while keeping structural details...
June 13, 2017: IEEE Transactions on Medical Imaging
https://www.readbyqxmd.com/read/28622587/statistical-characterization-of-noise-for-spatial-standardization-of-ct-scans-enabling-comparison-with-multiple-kernels-and-doses
#4
Gonzalo Vegas-Sánchez-Ferrero, Maria J Ledesma-Carbayo, George R Washko, Raúl San José Estépar
Computerized tomography (CT) is a widely adopted modality for analyzing directly or indirectly functional, biological and morphological processes by means of the image characteristics. However, the potential utilization of the information obtained from CT images is often limited when considering the analysis of quantitative information involving different devices, acquisition protocols or reconstruction algorithms. Although CT scanners are calibrated as a part of the imaging workflow, the calibration is circumscribed to global reference values and does not circumvent problems that are inherent to the imaging modality...
June 7, 2017: Medical Image Analysis
https://www.readbyqxmd.com/read/28614900/computational-method-for-estimating-boundary-of-abdominal-subcutaneous-fat-for-absolute-electrical-impedance-tomography
#5
Tohru F Yamaguchi, Yoshiwo Okamoto
Abdominal fat accumulation is considered an essential indicator of human health. Electrical impedance tomography has considerable potential for abdominal fat imaging because of the low specific conductivity of human body fat. In this paper, we propose a robust reconstruction method for high-fidelity conductivity imaging by abstraction of the abdominal cross section using a relatively small number of parameters. Toward this end, we assume homogeneous conductivity in the abdominal subcutaneous fat area, and characterize its geometrical shape by parameters defined as the ratio of the distance from the center to boundary of subcutaneous fat to the distance from the center to outer boundary in 64 equiangular directions...
June 14, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28612371/estimation-in-multi-arm-two-stage-trials-with-treatment-selection-and-time-to-event-endpoint
#6
Matthias Brückner, Andrew Titman, Thomas Jaki
We consider estimation of treatment effects in two-stage adaptive multi-arm trials with a common control. The best treatment is selected at interim, and the primary endpoint is modeled via a Cox proportional hazards model. The maximum partial-likelihood estimator of the log hazard ratio of the selected treatment will overestimate the true treatment effect in this case. Several methods for reducing the selection bias have been proposed for normal endpoints, including an iterative method based on the estimated conditional selection biases and a shrinkage approach based on empirical Bayes theory...
June 13, 2017: Statistics in Medicine
https://www.readbyqxmd.com/read/28610694/preconditioned-alternating-projection-algorithm-for-solving-the-penalized-likelihood-spect-reconstruction-problem
#7
Si Li, Jiahan Zhang, Andrzej Krol, C Ross Schmidtlein, David Feiglin, Yuesheng Xu
PURPOSE: The authors recently developed a preconditioned alternating projection algorithm (PAPA) for solving the penalized-likelihood SPECT reconstruction problem. The proposed algorithm can solve a wide variety of non-differentiable optimization models. This work is dedicated to comparing the performance of PAPA with total variation (TV) regularization (TV-PAPA) and a novel forward-backward algorithm with nested expectation maximization (EM)-TV iteration scheme (FB-EM-TV). METHODS: Monte Carlo technique was used to simulate multiple noise realizations of the fan-beam collimated SPECT data for a piecewise constant phantom with warm background, and hot and cold spheres with uniform activities at two noise levels...
June 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28603934/model-based-t1-mapping-with-sparsity-constraints-using-single-shot-inversion-recovery-radial-flash
#8
Xiaoqing Wang, Volkert Roeloffs, Jakob Klosowski, Zhengguo Tan, Dirk Voit, Martin Uecker, Jens Frahm
PURPOSE: To develop a model-based reconstruction technique for single-shot T1 mapping with high spatial resolution, accuracy, and precision using an inversion-recovery (IR) fast low-angle shot (FLASH) acquisition with radial encoding. METHODS: The proposed model-based reconstruction jointly estimates all model parameters, that is, the equilibrium magnetization, steady-state magnetization, 1/ T1*, and all coil sensitivities from the data of a single-shot IR FLASH acquisition with a small golden-angle radial trajectory...
June 11, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28600270/an-iterated-greedy-heuristic-for-mixed-no-wait-flowshop-problems
#9
Yamin Wang, Xiaoping Li, Ruben Ruiz, Shaochun Sui
The mixed no-wait flowshop problem with both wait and no-wait constraints has many potential real-life applications. The problem can be regarded as a generalization of the traditional permutation flowshop and the no-wait flowshop. In this paper, we study, for the first time, this scheduling setting with makespan minimization. We first propose a mathematical model and then we design a speed-up makespan calculation procedure. By introducing a varying number of destructed jobs, a modified iterated greedy algorithm is proposed for the considered problem which consists of four components: 1) initialization solution construction; 2) destruction; 3) reconstruction; and 4) local search...
June 5, 2017: IEEE Transactions on Cybernetics
https://www.readbyqxmd.com/read/28596635/an-investigation-of-low-dose-3d-scout-scans-for-computed-tomography
#10
Juliana Gomes, Grace J Gang, Aswin Mathews, J Webster Stayman
PURPOSE: Commonly 2D scouts or topograms are used prior to CT scan acquisition. However, low-dose 3D scouts could potentially provide additional information for more effective patient positioning and selection of acquisition protocols. We propose using model-based iterative reconstruction to reconstruct low exposure tomographic data to maintain image quality in both low-dose 3D scouts and reprojected topograms based on those 3D scouts. METHODS: We performed tomographic acquisitions on a CBCT test-bench using a range of exposure settings from 16...
February 11, 2017: Proceedings of SPIE
https://www.readbyqxmd.com/read/28596194/influence-of-ultra-low-dose-and-iterative-reconstructions-on-the-visualization-of-orbital-soft-tissues-on-maxillofacial-ct
#11
G Widmann, D Juranek, F Waldenberger, P Schullian, A Dennhardt, R Hoermann, M Steurer, E-M Gassner, W Puelacher
BACKGROUND AND PURPOSE: Dose reduction on CT scans for surgical planning and postoperative evaluation of midface and orbital fractures is an important concern. The purpose of this study was to evaluate the variability of various low-dose and iterative reconstruction techniques on the visualization of orbital soft tissues. MATERIALS AND METHODS: Contrast-to-noise ratios of the optic nerve and inferior rectus muscle and subjective scores of a human cadaver were calculated from CT with a reference dose protocol (CT dose index volume = 36...
June 8, 2017: AJNR. American Journal of Neuroradiology
https://www.readbyqxmd.com/read/28583291/evaluation-of-a-commercial-model-based-iterative-reconstruction-algorithm-in-computed-tomography
#12
Nicoletta Paruccini, Raffaele Villa, Claudia Pasquali, Chiara Spadavecchia, Antonia Baglivi, Andrea Crespi
INTRODUCTION: Iterative reconstruction algorithms have been introduced in clinical practice to obtain dose reduction without compromising the diagnostic performance. PURPOSE: To investigate the commercial Model Based IMR algorithm by means of patient dose and image quality, with standard Fourier and alternative metrics. MATERIALS AND METHODS: A Catphan phantom, a commercial density phantom and a cylindrical water filled phantom were scanned both varying CTDIvol and reconstruction thickness...
June 2, 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28572719/multi-gpu-acceleration-of-branchless-distance-driven-projection-and-backprojection-for-clinical-helical-ct
#13
Ayan Mitra, David G Politte, Bruce R Whiting, Jeffrey F Williamson, Joseph A O'Sullivan
Model-based image reconstruction (MBIR) techniques have the potential to generate high quality images from noisy measurements and a small number of projections which can reduce the x-ray dose in patients. These MBIR techniques rely on projection and backprojection to refine an image estimate. One of the widely used projectors for these modern MBIR based technique is called branchless distance driven (DD) projection and backprojection. While this method produces superior quality images, the computational cost of iterative updates keeps it from being ubiquitous in clinical applications...
January 2017: Journal of Imaging Science and Technology
https://www.readbyqxmd.com/read/28560040/spatially-segmented-undersampled-mri-temperature-reconstruction-for-transcranial-mr-guided-focused-ultrasound
#14
Pooja Gaur, Beat Werner, Xue Feng, Samuel W Fielden, Craig H Meyer, William A Grissom
BACKGROUND: Volumetric thermometry with fine spatiotemporal resolution is desirable to monitor MR-guided focused ultrasound (MRgFUS) procedures in the brain, but requires some form of accelerated imaging. Accelerated MR temperature imaging methods have been developed that undersample k-space and leverage signal correlations over time to suppress the resulting undersampling artifacts. However, in transcranial MRgFUS treatments, the water bath surrounding the skull creates signal variations that do not follow those correlations, leading to temperature errors in the brain due to signal aliasing...
2017: Journal of Therapeutic Ultrasound
https://www.readbyqxmd.com/read/28558769/a-photoacoustic-imaging-reconstruction-method-based-on-directional-total-variation-with-adaptive-directivity
#15
Jin Wang, Chen Zhang, Yuanyuan Wang
BACKGROUND: In photoacoustic tomography (PAT), total variation (TV) based iteration algorithm is reported to have a good performance in PAT image reconstruction. However, classical TV based algorithm fails to preserve the edges and texture details of the image because it is not sensitive to the direction of the image. Therefore, it is of great significance to develop a new PAT reconstruction algorithm to effectively solve the drawback of TV. METHODS: In this paper, a directional total variation with adaptive directivity (DDTV) model-based PAT image reconstruction algorithm, which weightedly sums the image gradients based on the spatially varying directivity pattern of the image is proposed to overcome the shortcomings of TV...
May 30, 2017: Biomedical Engineering Online
https://www.readbyqxmd.com/read/28556204/optimal-combination-of-anti-scatter-grids-and-software-correction-for-cbct-imaging
#16
Uros Stankovic, Lennert S Ploeger, Marcel van Herk, Jan-Jakob Sonke
PURPOSE: CBCT has been widely adopted in clinical practice for image-guided radiotherapy. Soft tissue contrast and Hounsfield units are impaired to presence of scattered radiation. In our previous work we proposed a high selectivity anti-scatter grid (ASG) as a possible solution to the problem. An alternative approach is the application of iterative scatter correction using deconvolution with scatter point spread function (PSF). The purpose of this work was to compare the performance of ASGs with different selectivity with and without the iterative and uniform scatter corrections in terms of CBCT image quality...
May 29, 2017: Medical Physics
https://www.readbyqxmd.com/read/28555878/correlation-between-a-2d-channelized-hotelling-observer-and-human-observers-in-a-low-contrast-detection-task-with-multi-slice-reading-in-ct
#17
Lifeng Yu, Baiyu Chen, James M Kofler, Christopher P Favazza, Shuai Leng, Matthew A Kupinski, Cynthia H McCollough
PURPOSE: Model observers have been successfully developed and used to assess the quality of static 2D CT images. However, radiologists typically read images by paging through multiple 2D slices (i.e. multi-slice reading). The purpose of this study was to correlate human and model observer performance in a low-contrast detection task performed using both 2D and multi-slice reading, and to determine if the 2D model observer still correlate well with human observer performance in multi-slice reading...
May 27, 2017: Medical Physics
https://www.readbyqxmd.com/read/28527236/a-weighted-difference-of-l1-and-l2-on%C3%A2-the%C3%A2-gradient-minimization-based-on%C3%A2-alternating-direction-method-for%C3%A2-circular%C3%A2-computed-tomography
#18
Wanli Lu, Lei Li, Ailong Cai, Hanming Zhang, Linyuan Wang, Bin Yan
Iterative reconstruction algorithms for computed tomography (CT) through total variation (TV) regularization can provide accurate and stable reconstruction results. TV minimization is the L1-norm of gradient-magnitude images and can be regarded as a convex relaxation method to replace the L0 norm. In this study, a fast and efficient algorithm, which is named a weighted difference of L1 and L2 (L1 - αL2) on the gradient minimization, was proposed and investigated. The new algorithm provides a better description of sparsity for the optimization-based algorithms than TV minimization algorithms...
May 15, 2017: Journal of X-ray Science and Technology
https://www.readbyqxmd.com/read/28508476/magnetic-resonance-electrical-properties-tomography-for-small-anomalies-using-boundary-conditions-a-simulation-study
#19
Joonsung Lee, Narae Choi, Jin Keun Seo, Dong-Hyun Kim
PURPOSE: Magnetic Resonance Electrical Property Tomography (MREPT) is an emerging imaging modality using measured B1 maps from Magnetic Resonance Imaging (MRI) to measure a distribution of electric conductivity and permittivity of the subject at the Larmor frequency. Conventional MREPT approachesat single transmit channel system using the Helmholtz equation rely on an assumption that conductivity and permittivity of the subject are locally homogeneous. For small tissue structures and tissue boundaries, in which the assumption of locally homogeneous conductivity and permittivity does not hold, the reconstructed conductivity values deviated from the actual values, so called "Boundary Artifacts"...
May 16, 2017: Medical Physics
https://www.readbyqxmd.com/read/28505440/iterative-reconstruction-of-memory-kernels
#20
Gerhard Jung, Martin Hanke, Friederike Schmid
In recent years, it has become increasingly popular to construct coarse-grained models with non-Markovian dynamics to account for an incomplete separation of time scales. One challenge of a systematic coarse-graining procedure is the extraction of the dynamical properties, namely, the memory kernel, from equilibrium all-atom simulations. In this article, we propose an iterative method for memory reconstruction from dynamical correlation functions. Compared to previously proposed noniterative techniques, it ensures by construction that the target correlation functions of the original fine-grained systems are reproduced accurately by the coarse-grained system, regardless of time step and discretization effects...
May 30, 2017: Journal of Chemical Theory and Computation
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