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John W Hayes, Daniel Gomez-Cardona, Ran Zhang, Ke Li, Juan Pablo Cruz-Bastida, Guang-Hong Chen
PURPOSE: Low signal correction (LSC) in the raw counts domain has been shown to effectively reduce noise streaks in CT because the data inconsistency associated with photon-starved regions may be mitigated prior to the log transformation step. However, a systematic study of the performance of these raw data correction methods is still missing in literature. The purpose of this work was to provide such a systematic study for two well-known low signal correction schemes using either the adaptive trimmed mean (ATM) filter or the anisotropic diffusion (AD) filter in the raw counts domain...
March 12, 2018: Medical Physics
Brian Appleton, Taylor Hubbard, Andreu Glasmann, Enrico Bellotti
We report on the modulation transfer function (MTF) in short-wave infrared indium gallium arsenide (InGaAs) on indium phosphide (InP) planar photodetector arrays. Our two-dimensional numerical method consists of optical simulations using the finite-difference time domain method and drift-diffusion simulations using the finite-element method. This parametric study investigates MTF dependence on pitch, the addition of refractive microlenses, the thickness of the InGaAs absorber, and the doping concentration of the InGaAs absorber...
March 5, 2018: Optics Express
Edouard Huard, Sophie Derelle, Julien Jaeck, Jean Nghiem, Riad Haïdar, Jérôme Primot
A challenging point in the prediction of the image quality of infrared imaging systems is the evaluation of the detector modulation transfer function (MTF). In this paper, we present a linear method to get a 2D continuous MTF from sparse spectral data. Within the method, an object with a predictable sparse spatial spectrum is imaged by the focal plane array. The sparse data is then treated to return the 2D continuous MTF with the hypothesis that all the pixels have an identical spatial response. The linearity of the treatment is a key point to estimate directly the error bars of the resulting detector MTF...
March 5, 2018: Optics Express
Jesse Tanguay, Ian A Cunningham
PURPOSE: Single-photon-counting (SPC) and spectroscopic x-ray detectors are under development in academic and industry laboratories for medical imaging applications. The spatial resolution of SPC and spectroscopic x-ray detectors is an important design criterion. The purpose of this article is to extend the cascaded systems approach to include a description of the spatial resolution of SPC and spectroscopic x-ray imaging detectors. METHODS: A cascaded systems approach was used to model reabsorption of characteristic x rays Coulomb repulsion, and diffusion in SPC and spectroscopic x-ray detectors...
March 11, 2018: Medical Physics
Jason Nguyen, Liliana Werner, Jason Ludlow, Joah Aliancy, Larry Ha, Bryan Masino, Sean Enright, Ray K Alley, Ruth Sahler
PURPOSE: To evaluate intraocular lens (IOL) power, modulation transfer function (MTF), light transmission, and light scattering of a blue light-filtering IOL before and after power adjustment by a femtosecond laser obtained through increased hydrophilicity of targeted areas within the optic, creating the ability to build a refractive-index-shaping lens within an existing IOL. SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study...
March 7, 2018: Journal of Cataract and Refractive Surgery
Ileana Iftimia, Per H Halvorsen
PURPOSE: The aim of this study was to develop Quality Assurance procedures for the BrainLab ExacTrac (ET) imaging system following the TG 142 recommendations for planar kV imaging systems. MATERIALS AND METHODS: A custom-designed 3D printed holder was used to position the Standard Imaging QCkV-1 phantom at isocenter, facing the ET X ray tubes. The linac's light field (collimator at 45⁰) was used to position the phantom holder. The ET images were exported to ARIA where geometric distortion was checked...
March 10, 2018: Journal of Applied Clinical Medical Physics
Xufen Xie, Hongda Fan, Hongyuan Wang, Zebin Wang, Nianyu Zou
The slanted edge method is a basic approach for measuring the modulation transfer function (MTF) of imaging systems; however, its measurement accuracy is limited in practice. Theoretical analysis of the slanted edge MTF measurement method performed in this paper reveals that inappropriate edge angles and random noise reduce this accuracy. The error caused by edge angles is analyzed using sampling and reconstruction theory. Furthermore, an error model combining noise and edge angles is proposed. We verify the analyses and model with respect to (i) the edge angle, (ii) a statistical analysis of the measurement error, (iii) the full width at half-maximum of a point spread function, and (iv) the error model...
March 1, 2018: Applied Optics
Patrick J Pan, Anshuman K Bansal, Scott J Genshaft, Grace H Kim, Robert D Suh, Fereidoun Abtin
PURPOSE: To determine size of ablation zone and pulmonary hemorrhage in double-freeze (DF) vs modified triple-freeze (mTF) cryoablation protocols with different probe sizes in porcine lung. MATERIALS AND METHODS: In 10 healthy adult pigs, 20 pulmonary cryoablations were performed using either a 2.4-mm or a 1.7-mm probe. Either conventional DF or mTF protocol was used. Serial noncontrast CT scans were performed during ablations. Ablation iceball and hemorrhage volumes were measured and compared between protocols and probe sizes...
March 3, 2018: Journal of Vascular and Interventional Radiology: JVIR
Maria A Parker, James C Anthony
INTRODUCTION: A mosaic of evidence links risk perceptions with drug use in adolescence, including population summaries to guide public health campaigns, as well as subject-specific estimates on preventing an adolescent's drug use by manipulating that individual's prior risk perceptions. We re-visit these issues with a public health perspective, asking whether population-level cannabis risk perceptions of school-attending adolescents at one grade level might predict cannabis use prevalence two and four grade levels later...
February 26, 2018: Addictive Behaviors
Antonio González-López
PURPOSE: In this work, the effect of noise on the precision in the modulation transfer function (MTF) calculation using different phantoms is investigated. Three different techniques are stud-ied, based on three different phantoms: edge, bar and star bar. For each technique, theoretical expressions for the standard deviation and the signal to noise ratio (SNR) of the MTF are derived. In addition, Monte Carlo simulations are carried out to study the accuracy and precision of all the three techniques...
March 3, 2018: Medical Physics
Oscar J Manrique, Kian Adabi, Jorys Martinez-Jorge, Pedro Ciudad, Fabio Nicoli, Kidakorn Kiranantawat
INTRODUCTION: There is an increased need for evidence-based practices in male-to-female (MtF) transgender vaginoplasty. Although there are a multitude of surgical techniques, there is a paucity of data comparing these procedures. A systematic review of retrospective studies on the outcomes of MtF vaginoplasty was conducted to minimize surgical complications and improve patient outcomes for transgender patients. METHODS: Applying the Preferred Reporting Items for Systematic Review and Meta-Analysis, a comprehensive search of several databases from 1985 to November 7, 2017, was conducted...
February 28, 2018: Annals of Plastic Surgery
Chiaki Tominaga, Hiroki Azumi, Mitsunori Goto, Masaaki Taura, Noriyasu Homma, Issei Mori
Edge methods are predominantly used for modulation transfer function (MTF) measurements in computed tomography (CT) images reconstructed using iterative methods. However, edge methods employ a relatively large and distinct test object, which is intended to simulate relatively large and distinct clinical organs. If one wants to assess the image quality of a small low-contrast object that is visually indistinct against a noisy background, a small and indistinct test object is desired. Another concern is that information related to the signal amount is discarded during MTF measurements...
February 23, 2018: Radiological Physics and Technology
Sifeng He, Yuan Meng, Mali Gong
This paper presents an effective approach to alleviate the cat-eye effect by inserting a freeform single lens into the original optical system. By shifting the image of the given optical system transversely on the original image plane, the reflected beams originating from the sensor are subsequently blocked by the optical aperture, substantially eliminating retroreflections from the system. The influence of incident angle on retroreflected beams is analyzed in detail, and the optimal image translation distance for completely eliminating the cat-eye effect is also proposed via numerical simulations...
February 10, 2018: Applied Optics
O Ortenzia, R Rossi, M Bertolini, A Nitrosi, C Ghetti
The aim of this article was to characterise the performance of four different digital breast tomosynthesis (DBT) systems in terms of dose and image quality parameters. One of them, GE Pristina, has never been tested before. Average glandular doses were measured both in DBT and 2D full field digital mammography mode. Several phantoms were employed to perform signal difference to noise ratio, slice sensitivity profile, slice to slice incrementation, chest wall offset, z-axis geometry, artefact spread function, low contrast detectability, contrast detail evaluations, image uniformity and in-plane MTF in chest wall-nipple and in tube-travel directions...
February 15, 2018: Radiation Protection Dosimetry
Sterling Quinn, Nathaniel Swain
Research suggests that transgender young offenders are a uniquely vulnerable caseload that may benefit from speech pathology intervention to help bring their voice into alignment with their gender identity. However, no previous studies have investigated treatment efficacy in this population. This study investigated the impact of intensive voice feminisation therapy targeting fundamental frequency and oral resonance in a 17 year old transgender individual within a youth justice institution. Acoustic analysis, listener and self-ratings of vocal femininity, self-ratings of vocal satisfaction, a post-treatment structured interview, and pre- and post- treatment completion of the Transsexual Voice Questionnaire (TVQ MtF ) were utilised to determine treatment impact...
February 8, 2018: Journal of Communication Disorders
Nate McDowell, Craig D Allen, Kristina Anderson-Teixeira, Paulo Brando, Roel Brienen, Jeff Chambers, Brad Christoffersen, Stuart Davies, Chris Doughty, Alvaro Duque, Fernando Espirito-Santo, Rosie Fisher, Clarissa G Fontes, David Galbraith, Devin Goodsman, Charlotte Grossiord, Henrik Hartmann, Jennifer Holm, Daniel J Johnson, Abd Rahman Kassim, Michael Keller, Charlie Koven, Lara Kueppers, Tomo'omi Kumagai, Yadvinder Malhi, Sean M McMahon, Maurizio Mencuccini, Patrick Meir, Paul Moorcroft, Helene C Muller-Landau, Oliver L Phillips, Thomas Powell, Carlos A Sierra, John Sperry, Jeff Warren, Chonggang Xu, Xiangtao Xu
Tree mortality rates appear to be increasing in moist tropical forests (MTFs) with significant carbon cycle consequences. Here, we review the state of knowledge regarding MTF tree mortality, create a conceptual framework with testable hypotheses regarding the drivers, mechanisms and interactions that may underlie increasing MTF mortality rates, and identify the next steps for improved understanding and reduced prediction. Increasing mortality rates are associated with rising temperature and vapor pressure deficit, liana abundance, drought, wind events, fire and, possibly, CO 2 fertilization-induced increases in stand thinning or acceleration of trees reaching larger, more vulnerable heights...
February 16, 2018: New Phytologist
Heather H Keller, Christina Lengyel, Natalie Carrier, Susan E Slaughter, Jill Morrison, Alison M Duncan, Catriona M Steele, Lisa Duizer, K Stephen Brown, Habib Chaudhury, Minn N Yoon, Veronique Boscart, George Heckman, Lita Villalon
This study determines the prevalence of inadequate micronutrient intakes consumed by long-term care (LTC) residents. This cross-sectional study was completed in thirty-two LTC homes in four Canadian provinces. Weighed and estimated food and beverage intake were collected over 3 non-consecutive days from 632 randomly selected residents. Nutrient intakes were adjusted for intra-individual variation and compared with the Dietary Reference Intakes. Proportion of participants, stratified by sex and use of modified (MTF) or regular texture foods, with intakes below the Estimated Average Requirement (EAR) or Adequate Intake (AI), were identified...
February 15, 2018: British Journal of Nutrition
Yoshinori Miyahara, Yuki Hara, Hiroto Nakashima, Tomonori Nishimura, Kanae Itakura, Taisuke Inomata, Hajime Kitagaki
In high-dose-rate (HDR) brachytherapy, a direct-conversion flat-panel detector (d-FPD) clearly depicts a 192Ir source without image halation, even under the emission of high-energy gamma-rays. However, it has been unknown why iridium is visible using a d-FPD. The purpose of this study was to clarify reasons for visibility of the source core based on physical imaging characteristics, including the modulation transfer functions (MTF), noise power spectral (NPS), contrast transfer functions (CTF), and linearity of d-FPD to high-energy gamma-rays...
February 9, 2018: Physics in Medicine and Biology
Ronald P Hudak, Rebecca Russell, P Paul Toland
Background: The evolution of governance models for the Military Health System's (MHS) large hospitals, called medical treatment facilities (MTFs), has culminated with the effort to implement Enhanced Multi-Service Markets (eMSM). The term eMSM refers to two separate concepts. First, MSM refers to those geographic areas, that is, markets, which have the following characteristics: they have MTFs that are operated by two or more Department of Defense (DoD) Services, that is, Army, Navy, or Air Force; there is a large beneficiary population; there is a substantial amount of direct care (i...
February 6, 2018: Military Medicine
Shoaib R Soomro, Hakan Urey
We propose an integrated 3D display and imaging system using a head-mounted device and a special dual-purpose passive screen that can simultaneously facilitate 3D display and imaging. The screen is mainly composed of two optical layers, the first layer is a projection surface, which are the finely patterned retro-reflective microspheres that provide high optical gain when illuminated with head-mounted projectors. The second layer is an imaging surface made up of an array of curved mirrors, which form the perspective views of the scene captured by a head-mounted camera...
January 22, 2018: Optics Express
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