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https://www.readbyqxmd.com/read/28645204/when-homoplasy-is-not-homoplasy-dissecting-trait-evolution-by-contrasting-composite-and-reductive-coding
#1
Alejandro Torres-Montúfar, Thomas Borsch, Helga Ochoterena
The conceptualization and coding of characters is a difficult issue in phylogenetic systematics, no matter which inference method is used when reconstructing phylogenetic trees or if the characters are just mapped onto a specific tree. Complex characters are groups of features that can be divided into simpler hierarchical characters (reductive coding), although the implied hierarchical relational information may change depending on the type of coding (composite vs reductive). Up to now, there is no common agreement to either code characters as complex or simple...
June 22, 2017: Systematic Biology
https://www.readbyqxmd.com/read/28644799/hybrid-cs-dmri-periodic-time-variant-subsampling-and-omnidirectional-total-variation-based-reconstruction
#2
Yipeng Liu, Shan Wu, Xiaolin Huang, Bing Chen, Ce Zhu
Compressive sensing (CS) has been used to accelerate dynamic magnetic resonance imaging (DMRI). Currently, the online CS-DMRI is faster, whereas the offline CS-DMRI provides higher accuracy for image reconstruction. To achieve good image reconstruction performance in terms of both speed and accuracy, we propose a hybrid CS-DMRI method using periodic timevariant subsampling for different frames. In each period, there is one reference frame that is sampled at a higher subsampling ratio. The two nearby reference frames with good reconstruction quality can be used to provide rough predictions of the other frames between them...
June 20, 2017: IEEE Transactions on Medical Imaging
https://www.readbyqxmd.com/read/28644152/incorporating-hypr-de-noising-within-iterative-pet-reconstruction-hypr-osem
#3
Ju-Chieh Kevin Cheng, Julian C Matthews, Vesna Sossi, Jose Anton-Rodriguez, Andre Salomon, Ronald Boellaard
HighlY constrained back-PRojection (HYPR) is a post-processing de-noising technique originally developed for time-resolved Magnetic Resonance Imaging. It has been recently applied to dynamic imaging for Positron Emission Tomography (PET) and shown promising results. In this work, we have developed an iterative reconstruction algorithm (HYPR-OSEM) which improves the signal-to-noise ratio (SNR) in static imaging (i.e. single frame reconstruction) by incorporating HYPR de-noising directly within the ordered subsets expectation maximization (OSEM) algorithm...
June 23, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28641250/deep-convolutional-neural-network-for-inverse-problems-in-imaging
#4
Kyong Hwan Jin, Michael T McCann, Emmanuel Froustey, Michael Unser
In this paper, we propose a novel deep convolutional neural network (CNN)-based algorithm for solving ill-posed inverse problems. Regularized iterative algorithms have emerged as the standard approach to ill-posed inverse problems in the past few decades. These methods produce excellent results, but can be challenging to deploy in practice due to factors including the high computational cost of the forward and adjoint operators and the difficulty of hyper parameter selection. The starting point of our work is the observation that unrolled iterative methods have the form of a CNN (filtering followed by point-wise nonlinearity) when the normal operator ( H*H where H* is the adjoint of the forward imaging operator, H ) of the forward model is a convolution...
June 15, 2017: IEEE Transactions on Image Processing: a Publication of the IEEE Signal Processing Society
https://www.readbyqxmd.com/read/28639254/use-of-a-digital-phantom-developed-by-qiba-for-harmonizing-suvs-obtained-from-the-state-of-the-art-spect-ct-systems-a-multicenter-study
#5
Tadaki Nakahara, Hiromitsu Daisaki, Yasushi Yamamoto, Takashi Iimori, Kazuyuki Miyagawa, Tomoya Okamoto, Yoshiki Owaki, Nobuhiro Yada, Koichi Sawada, Ryotaro Tokorodani, Masahiro Jinzaki
BACKGROUND: Although quantitative analysis using standardized uptake value (SUV) becomes realistic in clinical single-photon emission computed tomography/computed tomography (SPECT/CT) imaging, reconstruction parameter settings can deliver different quantitative results among different SPECT/CT systems. This study aims to propose a use of the digital reference object (DRO), which is a National Electrical Manufacturers Association (NEMA) phantom-like object developed by the Quantitative Imaging Biomarker Alliance (QIBA) fluorodeoxyglucose-positron emission tomography technical committee, for the purpose of harmonizing SUVs in Tc-99m SPECT/CT imaging...
December 2017: EJNMMI Research
https://www.readbyqxmd.com/read/28636511/feasibility-of-low-dose-coronary-computed-tomographic-angiography-used-in-atrial-fibrillation-patients
#6
Chenglin Zhao, Mengxi Jiang, Jianxin Liu, Li Gao, Xiaoying Wang
OBJECTIVE: The diagnosis of coronary artery disease (CAD) in atrial fibrillation (AF) patients using coronary computed tomography angiography (CCTA) requires a large exposure dosage or repeated examinations. This study evaluates the feasibility of using low-dose CCTA in the double prospectively ECG-triggered high-pitch spiral acquisition mode (Double Flash Spiral mode). METHODS: Twenty-eight AF patients with suspected CAD were recruited. Double Flash Spiral mode (tube voltage 100 kVp) and iterative reconstruction was used for CCTA examination...
March 21, 2017: Acta Cardiologica
https://www.readbyqxmd.com/read/28629567/ct-coronary-calcium-scoring-with-tin-filtration-using-iterative-beam-hardening-calcium-correction-reconstruction
#7
Christian Tesche, Carlo N De Cecco, U Joseph Schoepf, Taylor M Duguay, Moritz H Albrecht, Domenico De Santis, Akos Varga-Szemes, Virginia W Lesslie, Ullrich Ebersberger, Richard R Bayer, Christian Canstein, Ellen Hoffmann, Thomas Allmendinger, John W Nance
OBJECTIVES: To investigate the diagnostic accuracy of CT coronary artery calcium scoring (CACS) with tin pre-filtration (Sn100kVp) using iterative beam-hardening correction (IBHC) calcium material reconstruction compared to the standard 120kVp acquisition. BACKGROUND: Third generation dual-source CT (DSCT) CACS with Sn100kVp acquisition allows significant dose reduction. However, the Sn100kVp spectrum is harder with lower contrast compared to 120kVp, resulting in lower calcium score values...
June 2017: European Journal of Radiology
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
#8
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
#9
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/28623319/fast-projection-matching-for-x-ray-tomography
#10
Chun-Chieh Wang, Cheng-Cheng Chiang, Biqing Liang, Gung-Chian Yin, Yi-Tse Weng, Liang-Chi Wang
X-ray 3D tomographic techniques are powerful tools for investigating the morphology and internal structures of specimens. A common strategy for obtaining 3D tomography is to capture a series of 2D projections from different X-ray illumination angles of specimens mounted on a finely calibrated rotational stage. However, the reconstruction quality of 3D tomography relies on the precision and stability of the rotational stage, i.e. the accurate alignment of the 2D projections in the correct three-dimensional positions...
June 16, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28622671/low-dose-ct-with-a-residual-encoder-decoder-convolutional-neural-network-red-cnn
#11
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
#12
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/28622249/dynamic-liver-magnetic-resonance-imaging-in-free-breathing-feasibility-of-a-cartesian-t1-weighted-acquisition-technique-with-compressed-sensing-and-additional-self-navigation-signal-for-hard-gated-and-motion-resolved-reconstruction
#13
Benjamin Kaltenbach, Andreas M Bucher, Julian L Wichmann, Dominik Nickel, Christoph Polkowski, Renate Hammerstingl, Thomas J Vogl, Boris Bodelle
OBJECTIVES: The aim of this study was to assess the feasibility of a free-breathing dynamic liver imaging technique using a prototype Cartesian T1-weighted volumetric interpolated breathhold examination (VIBE) sequence with compressed sensing and simultaneous acquisition of a navigation signal for hard-gated and motion state-resolved reconstruction. MATERIALS AND METHODS: A total of 43 consecutive oncologic patients (mean age, 66 ± 11 years; 44% female) underwent free-breathing dynamic liver imaging for the evaluation of liver metastases from colorectal cancer using a prototype Cartesian VIBE sequence (field of view, 380 × 345 mm; image matrix, 320 × 218; echo time/repetition time, 1...
June 16, 2017: Investigative Radiology
https://www.readbyqxmd.com/read/28622248/quantitative-perfusion-analysis-of-the-rectum-using-golden-angle-radial-sparse-parallel-magnetic-resonance-imaging-initial-experience-and-comparison-to-time-resolved-angiography-with-interleaved-stochastic-trajectories
#14
Ulrike I Attenberger, Jing Liu, Philipp Riffel, Johannes Budjan, Robert Grimm, Kai T Block, Stefan O Schoenberg, Xiaoying Wang, Daniel Hausmann
OBJECTIVES: Purpose of this study was to compare the quality of perfusion maps obtained from prototypical free-breathing magnetic resonance imaging (MRI) with continuous golden-angle radial sampling and iterative reconstruction (GRASP) to conventional acquisition using time-resolved angiography with interleaved stochastic trajectories (TWIST) in patients with rectal cancer. MATERIAL AND METHODS: Forty cases were included for retrospective analysis. Twenty of the patients received routine multiparametric MRI at 3 T for rectal cancer staging, including perfusion measurement with GRASP or TWIST (10 patients for each technique, including 5 prechemoradiation and 5 postchemoradiation)...
June 16, 2017: Investigative Radiology
https://www.readbyqxmd.com/read/28620616/the-impact-of-combining-a-low-tube-voltage-acquisition-with-iterative-reconstruction-on-total-iodine-dose-in-coronary-ct-angiography
#15
Toon Van Cauteren, Gert Van Gompel, Kaoru Tanaka, Douwe E Verdries, Dries Belsack, Koenraad H Nieboer, Inneke Willekens, Paul Evans, Sven Macholl, Guy Verfaillie, Steven Droogmans, Johan de Mey, Nico Buls
OBJECTIVES: To assess the impact of combining low-tube voltage acquisition with iterative reconstruction (IR) techniques on the iodine dose in coronary CTA. METHODS: Three minipigs underwent CCTA to compare a standard of care protocol with two alternative study protocols combining low-tube voltage and low iodine dose with IR. Image quality was evaluated objectively by the CT value, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) in the main coronary arteries and aorta and subjectively by expert reading...
2017: BioMed Research International
https://www.readbyqxmd.com/read/28616448/adaptive-statistical-iterative-reconstruction-improves-image-quality-without-affecting-perfusion-ct-quantitation-in-primary-colorectal-cancer
#16
D Prezzi, V Goh, S Virdi, S Mallett, C Grierson, D J Breen
OBJECTIVES: To determine the effect of Adaptive Statistical Iterative Reconstruction (ASIR) on perfusion CT (pCT) parameter quantitation and image quality in primary colorectal cancer. METHODS: Prospective observational study. Following institutional review board approval and informed consent, 32 patients with colorectal adenocarcinoma underwent pCT (100 kV, 150 mA, 120 s acquisition, axial mode). Tumour regional blood flow (BF), blood volume (BV), mean transit time (MTT) and permeability surface area product (PS) were determined using identical regions-of-interests for ASIR percentages of 0%, 20%, 40%, 60%, 80% and 100%...
2017: European Journal of Radiology Open
https://www.readbyqxmd.com/read/28614900/computational-method-for-estimating-boundary-of-abdominal-subcutaneous-fat-for-absolute-electrical-impedance-tomography
#17
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/28614327/super-resolution-in-diffractive-imaging-from-hemispherical-elastic-light-scattering-data
#18
Sergiy Lysenko, Valeriy Sterligov, Manuel Gonçalves, Armando Rúa, Iaroslav Gritsayenko, Félix Fernández
Angle-resolved hemispherical elastic light scattering techniques have been used to reconstruct the surface profile of two-dimensional photonic crystals with submicron resolution and metrological precision. Iterative algorithms permit subsequent calculation of a surface autocorrelation function with additional numerical approximation of the power spectrum and then yield final reconstruction of the surface shape. The proposed method enables filtering out unwanted scattering background, precluding the convergence of phase-retrieval algorithms...
June 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28612371/estimation-in-multi-arm-two-stage-trials-with-treatment-selection-and-time-to-event-endpoint
#19
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
#20
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
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