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geometrical calibration

Qinyong Lin, Ken Cai, Rongqian Yang, Weihu Xiao, Jinhua Huang, Yinwei Zhan, Jian Zhuang
BACKGROUND: Patient-to-image registration is required for image-guided surgical navigation, but marker-based registration is time consuming and subject to manual error. Markerless registration is an alternative solution to avoid these issues. METHODS: This study designs a calibration board and proposes a geometric calibration method to calibrate the near infrared tracking and structured light components of the proposed optical surgical navigation system simultaneously...
December 17, 2018: International Journal of Medical Robotics + Computer Assisted Surgery: MRCAS
Deyu Yin, Jingbin Liu, Teng Wu, Keke Liu, Juha Hyyppä, Ruizhi Chen
Laser rangefinders (LRFs) are widely used in autonomous systems for indoor positioning and mobile mapping through the simultaneous localization and mapping (SLAM) approach. The extrinsic parameters of multiple LRFs need to be determined, and they are one of the key factors impacting system performance. This study presents an extrinsic calibration method of multiple LRFs that requires neither extra calibration sensors nor special artificial reference landmarks. Instead, it uses a naturally existing cuboid-shaped corridor as the calibration reference, and it hence needs no additional cost...
December 10, 2018: Sensors
John S Kinsey, Edwin Corporan, Jelica Pavlovic, Matthew DeWitt, Christopher Klingshirn, Russell Logan
Emission measurements of black carbon (BC) mass were conducted on a T63 turboshaft engine, operated at idle and cruise power with conventional and alternative fuels, using an Artium LII-300 laser induced incandescence (LII) analyzer and AVL Model 483 Micro Soot Sensor (MSS) photoacoustic instrument using the manufacturer's calibration for both instruments. These measurements were compared to elemental carbon (EC) determined by manual and semi-continuous thermal-optical transmission analyses according to National Institute for Occupational Safety and Health (NIOSH) Method 5040 as the reference method...
December 7, 2018: Journal of the Air & Waste Management Association
Kun Ma, Mingqiang Li, Xi Tao, Dong Zeng, Yongbo Wang, Zhaoying Bian, Ziquan Wei, Gaofeng Chen, Qianjin Feng, Jianhua Ma, Jing Huang
OBJECTIVE: To establish a cone beam computed tomography (ECBCT) system for high-resolution imaging of the extremities. METHODS: Based on three-dimensional X-Ray CT imaging and high-resolution flat plate detector technique, we constructed a physical model and a geometric model for ECBCT imaging, optimized the geometric calibration and image reconstruction methods, and established the scanner system. In the experiments, the pencil vase phantom, image quality (IQ) phantom and a swine feet were scanned using this imaging system to evaluate its effectiveness and stability...
November 30, 2018: Nan Fang Yi Ke da Xue Xue Bao, Journal of Southern Medical University
Guochen Bao, Ka-Leung Wong, Dayong Jin, Peter A Tanner
The optical thermometer has shown great promise for use in the fields of aeronautical engineering, environmental monitoring and medical diagnosis. Self-referencing lanthanide thermo-probes distinguish themselves because of their accuracy, calibration, photostability, and temporal dimension of signal. However, the use of conventional lanthanide-doped materials is limited by their poor reproducibility, random distance between energy transfer pairs and interference by energy migration, thereby restricting their utility...
2018: Light, Science & Applications
Tianshun Miao, Petr Bruza, Brian W Pogue, Michael Jermyn, Venkataramanan Krishnaswamy, William Ware, Frank Rafie, David J Gladstone, Benjamin B Williams
PURPOSE: A remote imaging system tracking Cherenkov emission was analyzed to verify that the linear accelerator (linac) beam shape could be quantitatively measured at the irradiation surface for Quality Audit (QA). METHODS: The Cherenkov camera recorded 2D dose images delivered on a solid acrylonitrile butadiene styrene (ABS) plastic phantom surface for a range of square beam sizes, and 6 MV photons. Imaging was done at source to surface distance (SSD) of 100cm and compared to GaF film images and linac light fields of the same beam sizes, ranging over 5×5cm2 up to 20×20cm2 ...
November 24, 2018: Medical Physics
Davide Biganzoli, Fabio Ferri
We revisited the classical Schätzel formulas (K. Schätzel, Quantum Optics2, 2871990) of the variance and covariance matrix associated to the normalized auto-correlation function in a Dynamic Light Scattering experiment when the sample is characterized by a single exponential decay function. Although thoroughly discussed by Schätzel who also outlined a correcting procedure, such formulas do not include explicitly the effects of triangular averaging that arise when the sampling time Δt is comparable or larger than the correlation time τc...
October 29, 2018: Optics Express
Firas Abedi, You Yang, Qiong Liu
Calibration on multi-camera imaging system in circular arrangement is a challenge task, because the preliminary shared feature points are absent among opposite viewpoints in the calibration procedure. In this paper, we propose a scheme of group geometric calibration and ideal rectification for circular multi-camera imaging system. In this scheme, a three-dimensional (3D) calibration object with new patterns is firstly designed to extract the extrinsic parameters. After that, the ideal camera projection matrix is estimated based on these parameters...
November 12, 2018: Optics Express
G Drzewiecki, G Krishna, H Katta
BACKGROUND: The Continuous Non-Invasive measurement of arterial Blood Pressure [CNIBP] is possible via the method of arterial tonometry and the arterial volume clamp methods. Arterial tonometry successfully measures continuous arterial pressure but requires large vessel deformation and a highly miniaturized pressure sensor to obtain a direct calibration of pressure. A properly designed tonometer is capable of achieving pressure accuracy of less than 5% error at the radial artery. The volume clamp method achieves comparable errors but is generally restricted to the very peripheral arteries...
October 9, 2018: Computers in Biology and Medicine
Ke Li, Xiao-Rui Wang, Bing-Tao Guo, Wei-Guo Zhang, Hang Yuan, Xiong-Xiong Wu, Chen Zhao
The accurate generation of infrared (IR) imaging features of subpixel targets plays a very important role in the demonstration, verification, and optimization of system design schemes as well as in research into detection algorithms for small targets in the development of remote IR early warning systems. Based on the generation mechanism of target full-link IR imaging features, this study theoretically considers target radiation characteristics, the working environment, and the spatial response and energy-conversion characteristics of IR sensors, and an accurate deduction model of IR imaging features of subpixel targets is proposed and established...
November 1, 2018: Applied Optics
Heng Mao, Jie He, Jiazhi Zhang, Yuanchao Bai, Muyue Zhai, Haiwen Li, Xiange Wen, Rui Chen, Huizhu Jia, Louis Tao, Ming Jiang
The state-of-the-art commercial telephoto lens has already provided us almost one giga space-bandwidth product. Since the single-image sensor cannot take such sampling capacity, we implement a four-parallel-boresight imaging system by using four such lenses and use 64 image sensors to complete full field of view (FOV) imaging for achieving 0.8 gigapixel over 15.6°×10.5°. Multiple sensors mosaicking can make most online computation and data transfer in parallel, and help us to realize a gigapixel video camera...
October 10, 2018: Applied Optics
Eugene Wong, Stefan Heist, Christian Bräuer-Burchardt, Holger Babovsky, Richard Kowarschik
Geometric calibration of digital light processing projectors in single-camera, fringe-projecting 3D measurement systems have been studied assuming the projector is inverse pinhole modeled. Conversely, a high-speed multi-aperture array projector (MAAP) projecting aperiodic fringes is not dependent on a digital mirror device and cannot be pinhole modeled. With MAAP projection, a stereo camera setup is required. This paper presents a model-less method to calibrate a MAAP by direct measurement of its illumination field and re-enables 3D measurements with a single camera even with surface discontinuities present...
September 10, 2018: Applied Optics
Ran Nissan, Galia Spectre, Avital Hershkovitz, Hefziba Green, Shai Shimony, Lisa Cooper, Sigal Nakav, Tzippy Shochat, Alon Grossman, Shmuel Fuchs
BACKGROUND: There is a paucity of data on apixaban levels among octogenarians with non-valvular atrial fibrillation (NVAF). We aimed to compare apixaban levels between octogenarians (with and without dose reduction) and younger patients, to assess the frequency of high and above-range drug levels. METHODS: A cross-sectional, prospective study of 80 patients treated with apixaban for NVAF was conducted. Apixaban levels were compared among octogenarians treated with 5 mg twice daily (bid), octogenarians with appropriately reduced dose (2...
November 21, 2018: Drugs & Aging
Guo Zhang, Qingwei Wu, Taoyang Wang, Ruishan Zhao, Mingjun Deng, Boyang Jiang, Xin Li, Huabin Wang, Yu Zhu, Fangting Li
The Gaofen-3 (GF-3) satellite is the first C-band multi-polarization synthetic aperture radar (SAR) with the ability of high-accuracy mapping in China. However, the Ground Control Points (GCPs) are essential to ensure the accuracy of mapping for GF-3 SAR imagery at present. In this paper, we analyze the error sources that affect the geometric processing and propose a new block adjustment method without GCPs for GF-3 SAR imagery. Firstly, the geometric calibration of GF-3 image is carried out. Secondly, the rational polynomial coefficient (RPC) model is directly generated after the geometric calibration parameters compensation of each image...
November 18, 2018: Sensors
Angela Faragasso, Joa O Bimbo, Atsushi Yamashita, Hajime Asama
Since direct manual palpation is not possible in minimally invasive procedures, there is an active field of applied research which aims to retrieve the human sense of touch and feedback tissue properties through artificial tactile feedback. This paper presents an innovative stiffness sensor to be embedded at the tip of a commercial endoscopic camera. The sensor structure is based on multiple cantilever beams, which act as springs with different stiffness when indented into soft tissue. Geometric features mounted on the beams are tracked during physical contact...
July 2018: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Svenja Ipsen, Ralf Bruder, Ivo Kuhlemann, Philipp Jauer, Laura Motisi, Florian Cremers, Floris Ernst, Achim Schweikard
Ultrasound (US) guidance is a rapidly growing area in image-guided radiotherapy. For motion compensation, the therapy target needs to be visualized with the US probe to continuously determine its position and adapt for shifts. While US has obvious benefits such as real-time capability and proven safety, one of the main drawbacks to date is its user dependency - high quality results require long years of clinical experience. To provide positioning assistance for the setup of US equipment by non-experts, we developed a visual guidance tool combining real-time US volume and CT visualization in a geometrically calibrated setup...
July 2018: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
M Szott, Z Wang, D N Ruzic
Quantitative understanding of the physics of dust or granular matter transport significantly impacts several aspects of burning plasma science and technology. This work takes machine vision techniques popular in robotics and self-driving cars and applies them to identification and analysis of microparticles generated from exploding wires. Using only the image frames and knowledge of the intrinsic properties of the cameras, a Python code was written to identify the particles, automatically calibrate the relative image positions, and extract trajectory data...
October 2018: Review of Scientific Instruments
S Maur, D Stsepankou, J Hesser
The image quality of dental cone-beam computed tomography (CBCT) is limited by the accuracy of device calibration. Inaccurate calibration introduces errors in the reconstruction process, which may lead to severe artifacts in the reconstructed volume. Patient motion during scan acquisition induces similar effects. This paper introduces a novel auto-calibration approach calculating geometrical projection parameters from unknown patient geometry. We formulate consistency conditions linking the information of consecutive projection images and a regularization technique to prevent overall distortions...
October 29, 2018: Physics in Medicine and Biology
Robin Jose, Ludger Santen, M Reza Shaebani
We present a coarse-grained model for stochastic transport of noninteracting chemical signals inside neuronal dendrites and show how first-passage properties depend on the key structural factors affected by neurodegenerative disorders or aging: the extent of the tree, the topological bias induced by segmental decrease of dendrite diameter, and the trapping probabilities in biochemical cages and growth cones. We derive an exact expression for the distribution of first-passage times, which follows a universal exponential decay in the long-time limit...
November 20, 2018: Biophysical Journal
Seraina Anne Dual, Jan Michael Zimmermann, Jürg Neuenschwander, Nicholas Heinrich Cohrs, Natalia Solowjowa, Wendelin Jan Stark, Mirko Meboldt, Marianne Schmid Daners
Future left ventricular assist devices (LVADs) are expected to respond to the physiologic need of patients; however, they still lack reliable pressure or volume sensors for feedback control. In the clinic, echocardiography systems are routinely used to measure left-ventricular (LV) volume. Until now, echocardiography in this form was never integrated in LVADs due to its computational complexity. The aim of this study was to demonstrate the applicability of a simplified ultrasonic sensor to fit an LVAD cannula and to show the achievable accuracy in vitro...
October 25, 2018: Artificial Organs
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