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https://www.readbyqxmd.com/read/28522252/optical-quality-of-rotationally-symmetrical-contact-lenses-derived-from-their-power-profiles
#1
Antonio J Del Águila-Carrasco, Daniel Monsálvez-Romín, Eleni Papadatou
PURPOSE: To present a methodology for evaluating the optical quality of rotationally symmetrical contact lenses (CLs) from a single power profile. METHODS: Simulated rotationally symmetrical power profiles corresponding to different CLs designs (monofocal, two-zone center-near bifocal, and four-zone center-distance bifocal) were used to calculate the wavefront error profile by means of numerical integration. Then, each lens wavefront error profile was spun around the center to obtain the lens wavefront error surface...
May 15, 2017: Contact Lens & Anterior Eye: the Journal of the British Contact Lens Association
https://www.readbyqxmd.com/read/28522170/optimization-of-the-alpha-image-reconstruction-an-iterative-ct-image-reconstruction-with-well-defined-image-quality-metrics
#2
Sergej Lebedev, Stefan Sawall, Michael Knaup, Marc Kachelrieß
PURPOSE: Optimization of the AIR-algorithm for improved convergence and performance. METHODS: The AIR method is an iterative algorithm for CT image reconstruction. As a result of its linearity with respect to the basis images, the AIR algorithm possesses well defined, regular image quality metrics, e.g. point spread function (PSF) or modulation transfer function (MTF), unlike other iterative reconstruction algorithms. The AIR algorithm computes weighting images α to blend between a set of basis images that preferably have mutually exclusive properties, e...
May 15, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28514670/radiation-safety-in-children-with-congenital-and-acquired-heart-disease-a-scientific-position-statement-on-multimodality-dose-optimization-from-the-image-gently-alliance
#3
REVIEW
Kevin D Hill, Donald P Frush, B Kelly Han, Brian G Abbott, Aimee K Armstrong, Robert A DeKemp, Andrew C Glatz, S Bruce Greenberg, Alexander Sheldon Herbert, Henri Justino, Douglas Mah, Mahadevappa Mahesh, Cynthia K Rigsby, Timothy C Slesnick, Keith J Strauss, Sigal Trattner, Mohan N Viswanathan, Andrew J Einstein
There is a need for consensus recommendations for ionizing radiation dose optimization during multi-modality medical imaging in children with congenital and acquired heart disease (CAHD). These children often have complex diseases and may be exposed to a relatively high cumulative burden of ionizing radiation from medical imaging procedures including cardiac computed tomography, nuclear cardiology studies and fluoroscopically guided diagnostic and interventional catheterization and electrophysiology procedures...
May 17, 2017: JACC. Cardiovascular Imaging
https://www.readbyqxmd.com/read/28499015/mri-exposimetry-how-to-analyze-compare-and-represent-worker-exposure-to-static-magnetic-field
#4
Antoine Delmas, Nicolas Weber, Joris Piffre, Cédric Pasquier, Jacques Felblinger, Pierre-André Vuissoz
Worker exposure to electromagnetic fields (EMF) is a growing concern of international commissions. A European directive from 2013 (2013/35/EU) recommend to estimate or measure EMF exposure of all exposed workers. Magnetic resonance imaging (MRI) workers are specially concerned by this point because they work all day long in the vicinity of a very strong magnet (generally 1.5 or 3 T), which cannot be turned off. Setting up a magnetic field monitoring device on these workers would therefore be a good way to ensure their security...
May 12, 2017: Radiation Protection Dosimetry
https://www.readbyqxmd.com/read/28495830/establishing-recommendations-for-stroke-systems-in-the-thrombectomy-era-the-upstate-new-york-stakeholder-proceedings
#5
Zainab Magdon-Ismail, Curtis Benesch, Jeremy T Cushman, Ian Brissette, Andrew M Southerland, Ethan S Brandler, Cemal B Sozener, Sue Flor, Roseanne Hemmitt, Kathleen Wales, Krystal Parrigan, Steven R Levine
BACKGROUND AND PURPOSE: The American Heart Association/American Stroke Association and Department of Health Stroke Coverdell Program convened a stakeholder meeting in upstate NY to develop recommendations to enhance stroke systems for acute large vessel occlusion. METHODS: Prehospital, hospital, and Department of Health leadership were invited (n=157). Participants provided goals/concerns and developed recommendations for prehospital triage and interfacility transport, rating each using a 3-level impact (A [high], B, and C [low]) and implementation feasibility (1 [high], 2, and 3 [low]) scale...
May 11, 2017: Stroke; a Journal of Cerebral Circulation
https://www.readbyqxmd.com/read/28487471/using-dti-to-assess-white-matter-microstructure-in-cerebral-small-vessel-disease-svd-in-multi-centre-studies
#6
Iain David Croall, Valerie Lohner, Barry Moynihan, Usman Khan, Ahamad Hassan, John T O'Brien, Robin G Morris, Daniel J Tozer, Victoria C Cambridge, Kirsty Harkness, David Werring, Andrew M Blamire, Gary A Ford, Thomas R Barrick, Hugh S Markus
Diffusion tensor imaging (DTI) metrics such as Fractional Anisotropy (FA) and Mean Diffusivity (MD) have been proposed as clinical trial markers of cerebral small vessel disease due to their associations with outcomes such as cognition. However, studies investigating this have been predominantly single-centre. As clinical trials are likely to be multi-site, further studies are required to determine whether associations with cognition of similar strength can be detected in a multi-centre setting. 109 patients (mean age=68) with symptomatic lacunar infarction and confluent white matter hyperintensities (WMH) on MRI was recruited across 6 sites as part of the PRESERVE DTI sub-study...
May 9, 2017: Clinical Science (1979-)
https://www.readbyqxmd.com/read/28477340/a-neural-network-approach-for-fast-automated-quantification-of-dir-performance
#7
John Neylon, Yugang Min, Daniel A Low, Anand Santhanam
PURPOSE: A critical step in adaptive radiotherapy (ART) workflow is deformably registering the simulation CT with the daily or weekly volumetric imaging. Quantifying the deformable image registration accuracy under these circumstances is a complex task due to the lack of known ground-truth landmark correspondences between the source data and target data. Generating landmarks manually (using experts) is time-consuming, and limited by image quality and observer variability. While image similarity metrics (ISM) may be used as an alternative approach to quantify the registration error, there is a need to characterize the ISM values by developing a non-linear cost function and translate them to physical distance measures in order to enable fast, quantitative comparison of registration performance...
May 5, 2017: Medical Physics
https://www.readbyqxmd.com/read/28475698/the-growing-need-for-validated-biomarkers-and-endpoints-for-dry-eye-clinical-research
#8
Neeta S Roy, Yi Wei, Eric Kuklinski, Penny A Asbell
Purpose: Biomarkers with minimally invasive and reproducible objective metrics provide the key to future paradigm shifts in understanding of the underlying causes of dry eye disease (DED) and approaches to treatment of DED. We review biomarkers and their validity in providing objective metrics for DED clinical research and patient care. Methods: The English-language literature in PubMed primarily over the last decade was surveyed for studies related to identification of biomarkers of DED: (1) inflammation, (2) point-of-care, (3) ocular imaging, and (4) genetics...
May 1, 2017: Investigative Ophthalmology & Visual Science
https://www.readbyqxmd.com/read/28475073/video-decolorization-using-visual-proximity-coherence-optimization
#9
Yizhang Tao, Yiyi Shen, Bin Sheng, Ping Li, Rynson W H Lau
Video decolorization is to filter out the color information while preserving the perceivable content in the video as much and correct as possible. Existing methods mainly apply image decolorization strategies on videos, which may be slow and produce incoherent results. In this paper, we propose a video decolorization framework that considers frame coherence and saves decolorization time by referring to the decolorized frames. It has three main contributions. First, we define decolorization proximity to measure the similarity of adjacent frames...
May 2, 2017: IEEE Transactions on Cybernetics
https://www.readbyqxmd.com/read/28470792/super-resolution-intracranial-quiescent-interval-slice-selective-magnetic-resonance-angiography
#10
Ioannis Koktzoglou, Robert R Edelman
PURPOSE: To evaluate the combination of nonenhanced quiescent-interval slice-selective (QISS) magnetic resonance angiography (MRA) with super-resolution reconstruction for portraying the intracranial arteries. METHODS: The intracranial arteries of seven volunteers were imaged at 3T using QISS MRA acquired with a flow-compensated fast low-angle shot (FLASH) readout and thin overlapping slices. The impacts of super-resolution reconstruction and various acquisition parameters on the delineation of intracranial arteries were quantified using four metrics: arterial-to-background contrast-to-noise ratio (CNR), arterial-to-background contrast, arterial sharpness, and arterial full-width-at-half-maximum (FWHM)...
May 3, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28468407/depth-dependent-dispersion-compensation-for-full-depth-oct-image
#11
Liuhua Pan, Xiangzhao Wang, Zhongliang Li, Xiangyang Zhang, Yang Bu, Nan Nan, Yan Chen, Xuan Wang
A depth-dependent dispersion compensation algorithm for enhancing the image quality of the Fourier-domain optical coherence tomography (OCT) is presented. The dispersion related with depth in the sample is considered. Using the iterative method, an analytical formula for compensating the depth-dependent dispersion in the sample is obtained. We apply depth-dependent dispersion compensation algorithm to process the phantom images and in vivo images. Using sharpness metric based on variation coefficient to compare the results processed with different dispersion compensation algorithms, we find that the depth-dependent dispersion compensation algorithm can improve image quality at full depth...
May 1, 2017: Optics Express
https://www.readbyqxmd.com/read/28464372/validation-of-phantom-based-harmonization-for-patient-harmonization
#12
Joseph V Panetta, Margaret E Daube-Witherspoon, Joel S Karp
PURPOSE: To improve the precision of multicenter clinical trials, several efforts are underway to determine scanner-specific parameters for harmonization using standardized phantom measurements. The goal of this study was to test the correspondence between quantification in phantom and patient images and validate the use of phantoms for harmonization of patient images. METHODS: The National Electrical Manufacturers' Association image quality phantom with hot spheres was scanned on two time-of-flight PET scanners...
May 2, 2017: Medical Physics
https://www.readbyqxmd.com/read/28457741/commissioning-of-applicator-guided-stereotactic-body-radiation-therapy-boost-with-high-dose-rate-brachytherapy-for-advanced-cervical-cancer-using-radiochromic-film-dosimetry
#13
Saad Aldelaijan, Shada Wadi-Ramahi, Ahmad Nobah, Belal Moftah, Slobodan Devic, Noha Jastaniyah
PURPOSE: To describe an EBT3 GAFCHROMIC film-based dosimetry method to be used in commissioning of a combined HDR brachytherapy (HDRB) and stereotactic body radiation therapy (SBRT) boost for treatment of advanced cervical cancer involving extensive residual disease after external beam treatment. METHODS AND MATERIALS: A cube phantom was designed to firmly fit an intrauterine tandem applicator and EBT3 radiochromic film pieces. A high-risk clinical target volume (CTVHR, Total) was contoured with an extended arm at one side...
April 27, 2017: Brachytherapy
https://www.readbyqxmd.com/read/28452934/a-genetic-algorithm-for-the-generation-of-packetization-masks-for-robust-image-communication
#14
Katherine Zapata-Quiñones, Cristian Duran-Faundez, Gilberto Gutiérrez, Vincent Lecuire, Christopher Arredondo-Flores, Hugo Jara-Lipán
Image interleaving has proven to be an effective solution to provide the robustness of image communication systems when resource limitations make reliable protocols unsuitable (e.g., in wireless camera sensor networks); however, the search for optimal interleaving patterns is scarcely tackled in the literature. In 2008, Rombaut et al. presented an interesting approach introducing a packetization mask generator based in Simulated Annealing (SA), including a cost function, which allows assessing the suitability of a packetization pattern, avoiding extensive simulations...
April 28, 2017: Sensors
https://www.readbyqxmd.com/read/28448234/leveraging-clinical-imaging-archives-for-radiomics-reliability-of-automated-methods-for-brain-volume-measurement
#15
Viraj R Adduru, Andrew M Michael, Maria Helguera, Stefi A Baum, Gregory J Moore
Purpose To validate the use of thick-section clinically acquired magnetic resonance (MR) imaging data for estimating total brain volume (TBV), gray matter (GM) volume (GMV), and white matter (WM) volume (WMV) by using three widely used automated toolboxes: SPM ( www.fil.ion.ucl.ac.uk/spm/ ), FreeSurfer ( surfer.nmr.mgh.harvard.edu ), and FSL (FMRIB software library; Oxford Centre for Functional MR Imaging of the Brain, Oxford, England, https://fsl.fmrib.ox.ac.uk/fsl ). Materials and Methods MR images from a clinical archive were used and data were deidentified...
April 27, 2017: Radiology
https://www.readbyqxmd.com/read/28444772/multi-atlas-approach-with-local-registration-goodness-weighting-for-mri-based-electron-density-mapping-of-head-and-neck-anatomy
#16
Reza Farjam, Neelam Tyagi, Harini Veeraraghavan, Aditya Apte, Kristen Zakian, Margie A Hunt, Joseph O Deasy
PURPOSE: The growing use of magnetic resonance imaging (MRI) as a substitute for computed tomography-based treatment planning requires the development of effective algorithms to generate electron density maps for treatment planning and patient setup verification. The purpose of this work was to develop a method to synthesize computerized tomography (CT) for MR-only radiotherapy of head and neck cancer patients. METHODS: The algorithm is based on registration of multiple patient datasets containing both MRI and CT images (a "multi-atlas" algorithm)...
April 26, 2017: Medical Physics
https://www.readbyqxmd.com/read/28444524/in-vitro-optical-quality-of-monofocal-aspheric-toric-intraocular-lenses-effect-of-cylindrical-power
#17
Teresa Ferrer-Blasco, Alberto Domínguez-Vicent, Santiago García-Lázaro, María Amparo Diez, José F Alfonso, José J Esteve-Taboada
PURPOSE: To assess the in vitro optical quality of monofocal aspheric toric intraocular lenses (IOLs) as a function of the cylindrical power. METHODS: The in vitro optical quality of the AcrySof IQ Toric IOLs SN6AT2, SN6AT3, SN6AT4, SN6AT5 and SN6AT6 (Alcon Laboratories Inc., Forth Worth, TX, USA) was assessed with an instrument conceived for measuring Zernike's coefficients at 3.0- and 5.0-mm apertures. As a reference, the aspheric monofocal lens AcrySof IQ Aspheric SN60WF (Alcon Laboratories Inc...
April 25, 2017: International Ophthalmology
https://www.readbyqxmd.com/read/28437922/from-toes-to-top-of-atmosphere-fowler-s-sneaker-depth-index-of-water-clarity-for-the-chesapeake-bay
#18
Benjamin Crooke, Lachlan I W McKinna, Ivona Cetinić
Fowler's Sneaker Depth (FSD), analogous to the well known Secchi disk depth (Zsd), is a visually discerned citizen scientist metric used to assess water clarity in the Patuxent River estuary. In this study, a simple remote sensing algorithm was developed to derive FSD from space-borne spectroradiometric imagery. An empirical model was formed that estimates FSD from red-end remote sensing reflectances at 645 nm, Rrs(645). The model is based on a hyperbolic function relating water clarity to Rrs(645) that was established using radiative transfer modeling and fine tuned using in-water FSD measurements and coincident Rrs(645) data observed by NASA's Moderate Resolution Imaging Spectroradiometer aboard the Aqua spacecraft (MODISA)...
April 17, 2017: Optics Express
https://www.readbyqxmd.com/read/28437565/relaxed-ordered-subset-preconditioned-alternating-projection-algorithm-for-pet-reconstruction-with-automated-penalty-weight-selection
#19
C Ross Schmidtlein, Yizun Lin, Si Li, Andrzej Krol, Bradley J Beattie, John L Humm, Yuesheng Xu
PURPOSE: Performance of the preconditioned alternating projection algorithm (PAPA) using relaxed ordered subsets (ROS) with a non-smooth penalty function was investigated in positron emission tomography (PET). A higher order total variation (HOTV) regularizer was applied and a method for unsupervised selection of penalty weights based on the measured data is introduced. METHODS: A ROS version of PAPA with HOTV penalty (ROS-HOTV-PAPA) for PET image reconstruction was developed and implemented...
April 24, 2017: Medical Physics
https://www.readbyqxmd.com/read/28436849/reverse-classification-accuracy-predicting-segmentation-performance-in-the-absence-of-ground-truth
#20
Vanya V Valindria, Ioannis Lavdas, Wenjia Bai, Konstantinos Kamnitsas, Eric O Aboagye, Andrea G Rockall, Daniel Rueckert, Ben Glocker
When integrating computational tools such as automatic segmentation into clinical practice, it is of utmost importance to be able to assess the level of accuracy on new data, and in particular, to detect when an automatic method fails. However, this is difficult to achieve due to absence of ground truth. Segmentation accuracy on clinical data might be different from what is found through cross-validation because validation data is often used during incremental method development, which can lead to overfitting and unrealistic performance expectations...
April 17, 2017: IEEE Transactions on Medical Imaging
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