Download or read book Prototype Fan Beam Optical Computed Tomography Scanner for Three dimensional Radiotherapy Dose Verification written by David Rudko and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A prototype rapid, high precision fan beam optical computed tomography (OptCT) scanner for three-dimensional polymer gel dosimetry of complex radiotherapy protocols has been developed. This study documents the design. construction and characterization of the system, as well as preliminary reconstructed optical attenuation images and dosimetric verification experiments. The principal goal in scanner design and implementation was to satisfy the Radiotherapy Accuracy and Precision (RTAP) criteria consisting of a spatial resolution of 1 x 1 x 1 mm3, an imaging time of 60 minutes, a dose accuracy within 3% and a precision within 1%. The scanner, which employs a sixty degree fan beam of 543 nm laser light to scan irradiated polymer gel samples up to 19 cm in cross-sectional diameter. has several defining attributes. Data acquisition for a single slice through a dosimeter is achieved in two minutes, using one signal acquisition per CT projection angle over a total of 360 projections. The effects of scatter and refraction of visible light are minimized by using the unique radial design of the matching medium tank, the concentric arrangement of a prototype, computer numerical control (CNC)-machined collimator and five Hamamatsu photodiode detector arrays for light detection. The novel tertiary collimation eliminates scattered light by 13% and improves reconstructed image contrast-to-noise ratio. Other characteristics of the scanner include: a laser power output variation of only 0.7%:, signal-to-noise ratio (SNR.) for calibration projections of up to 294:1, SNR for transmission projections through an irradiated polymer gel dosimeter of up to 161:1, a large absorbance dynamic range extending from 0.1 to 1.7 absorbance units and a spatial resolution of 0.25 mm2 in the axial plane of the scan?ning geometry and 0.8 mm along the longitudinal z-axis of the scan plane. Images of optical attenuation coefficients and concomitant dose maps extracted from irradi?ated, normoxic N--isopropylacylamide (NIPAM) polymer gels were used to investigate the potential of the system for dosimetric verification. Three different NIPAM gel irradiation experiments were performed and the resultant OptCT dose distributions were compared to the Eclipse? (Varian Medical Systems. Palo Alto. CA.) treatment planning system model. While the fan beam OptCT scanner provides promising ini?tial images of reconstructed optical attenuation coefficients, its dosimetric accuracy compared to Eclipse - nominally 7% in low dose gradient regions and 5% on the field edges - constitutes the most significant area for future refinement.
Download or read book Development of a Fan beam Optical Computed Tomography Scanner for Three dimensional Dosimetry written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The current state of a prototype fan-beam optical computed tomography scanner for three-dimensional radiation dosimetry has been presented. The system uses a helium-neon laser and a line-generating lens for fan-beam creation. Five photodiode arrays form an approximate arc detector array of 320-elements. Two options of physical collimators provide two levels of scatter-rejection: single-slot (SS) and multi-hole (MH). A pair of linear polarizers has been introduced as a means of light intensity modulation. This work examined: (i) the characterization of system components, (ii) data acquisition & imaging protocols, and (iii) the scanning of an nPAG dosimeter. (i): The polarizer-pair method of light intensity modulation has been calibrated and the polarization sensitivity of the detector array was evaluated. The relationship between detected values and both light intensity and photodiode integration time was examined. This examination indicated the need for an offset correction to treat all data acquired by the system. Data corruption near the edges of each photodiode array was found to cause ring artefacts in image reconstructions. Two methods of extending the dynamic range of the system---via integration time and light intensity---were presented. The use of master absorbent solutions and spectrophotometric data allowed for the preparation of absorption-based and scatter-based samples of known opacities. This ability allowed for the evaluation of the relative scatter-rejection capabilities of the system's two collimators. The MH collimator accurately measured highly-attenuating solutions of both absorption-based and scatter-based agents. The SS collimator experienced some contamination by scattered light with absorption-based agents, and significant contamination with scatter-based agents. Also, using the SS collimator, a `spiking' artefact was observed in highly-attenuating samples of both solution types. (ii): A change in imaging protocol has been described that grea.
Download or read book Development of a Fan beam Optical Computed Tomography Scanner for Three dimensional Dosimetry written by Warren Gerard Campbell and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The current state of a prototype fan-beam optical computed tomography scanner for three-dimensional radiation dosimetry has been presented. The system uses a helium-neon laser and a line-generating lens for fan-beam creation. Five photodiode arrays form an approximate arc detector array of 320-elements. Two options of physical collimators provide two levels of scatter-rejection: single-slot (SS) and multi-hole (MH). A pair of linear polarizers has been introduced as a means of light intensity modulation. This work examined: (i) the characterization of system components, (ii) data acquisition & imaging protocols, and (iii) the scanning of an nPAG dosimeter. (i): The polarizer-pair method of light intensity modulation has been calibrated and the polarization sensitivity of the detector array was evaluated. The relationship between detected values and both light intensity and photodiode integration time was examined. This examination indicated the need for an offset correction to treat all data acquired by the system. Data corruption near the edges of each photodiode array was found to cause ring artefacts in image reconstructions. Two methods of extending the dynamic range of the system--via integration time and light intensity--were presented. The use of master absorbent solutions and spectrophotometric data allowed for the preparation of absorption-based and scatter-based samples of known opacities. This ability allowed for the evaluation of the relative scatter-rejection capabilities of the system's two collimators.
Download or read book MicroComputed Tomography written by Stuart R. Stock and published by CRC Press. This book was released on 2018-10-03 with total page 273 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the availability of commercial laboratory systems and the emergence of user facilities at synchrotron radiation sources, studies of microcomputed tomography or microCT have increased exponentially. MicroComputed Technology provides a complete introduction to the technology, describing how to use it effectively and understand its results. The first part of the book focuses on methodology, covering experimental methods, data analysis, and visualization approaches. The second part addresses various microCT applications, including porous solids, microstructural evolution, soft tissue studies, multimode studies, and indirect analyses. The author presents a sufficient amount of fundamental material so that those new to the field can develop a relative understanding of how to design their own microCT studies. One of the first full-length references dedicated to microCT, this book provides an accessible introduction to field, supplemented with application examples and color images.
Download or read book Proceedings written by and published by . This book was released on 1984 with total page 588 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Three dimensional Cone beam Computed Tomography ActiveX Style written by Stefano Agostinelli (fisico.) and published by . This book was released on 2000 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Residual Stress Thermomechanics Infrared Imaging Hybrid Techniques and Inverse Problems Volume 8 written by Marco Rossi and published by Springer Science & Business Media. This book was released on 2013-08-27 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt: Residual Stress, Thermomechanics & Infrared Imaging, Hybrid Techniques and Inverse Problems, Volume 8: Proceedings of the 2013 Annual Conference on Experimental and Applied Mechanics, the eighth volume of eight from the Conference, brings together contributions to this important area of research and engineering. The collection presents early findings and case studies on a wide range of areas, including: Advances in Residual Stress Measurement Methods Residual Stress Effects on Material Performance Optical, Ultrasonic, and Diffraction Methods for Residual Stress Measurement Thermomechanics & Infrared Imaging Inverse Methods Inverse Methods in Plasticity Applications in Experimental Mechanics
Download or read book Cumulated Index Medicus written by and published by . This book was released on 1994 with total page 1256 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Modular Multi source X ray Tube for Novel Computed Tomography Applications written by Brandon Joseph Walker and published by . This book was released on 2017 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: A modular implementation of a scanning multi-source x-ray tube is designed for the increasing number of multi-source imaging applications in computed tomography (CT). An electron beam array coupled with an oscillating magnetic deflector is proposed as a means for producing an x-ray focal spot at any position along a line. The preliminary multi-source model includes three thermionic electron guns that are deflected in tandem by a slowly varying magnetic field and pulsed according to a scanning sequence developed for a high-speed CT scanner. Particle tracking simulations with particle dynamics analysis software demonstrate that three 100 keV electron beams are laterally swept a combined distance of 15 cm over a stationary target with an oscillating magnetic field of 102 G perpendicular to the beam axis. Beam modulation is accomplished using 25 μs pulse widths to a grid electrode with a reverse gate bias of -500 V and an extraction voltage of +1000 V. Projected focal spot diameters are approximately 1 mm for 138 mA electron beams and the stationary target stays within thermal limits for the 14 kW module. This concept could be used as the basis for increasing scan throughput for high-speed stationary CT scanners, for lowering dose with virtual fan beam formation, for reducing scatter radiation in cone-beam CT, or in other industrial applications. A benchtop implementation of the multi-source x-ray tube model is subsequently developed to demonstrate proof of concept for the system. Particle tracking simulations for the benchtop system demonstrate that three 80 keV electron beams are able to be focused and laterally swept a combined distance of 15 cm over a stationary target with an oscillating magnetic field of approximately 60 G. Beam spot diameters are approximately 1 mm for 27 mA beams and the stationary target stays well within thermal limits. The relevant hardware and control circuits are developed for incorporation into a physical prototype, including the development of a programmable high voltage bi-polar square wave pulser for electron beam gating. The particle tracking, electromagnetic, and thermal simulations inform the design of a 2.2 kW benchtop system that is currently under construction.
Download or read book Digital Technologies in Craniomaxillofacial Surgery written by Alex M. Greenberg and published by Springer. This book was released on 2018-06-13 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt: Digital technologies are changing the way that surgeons operate. They are revolutionizing the ability of surgeons to visualize, plan, and create rapid prototyped models and patient- specific implants for the broad disciplines of ENT, plastic, oral and maxillofacial surgeons. This book provides information on the latest digital technologies available for craniomaxillofacial surgery, discussing how this technology allows for preplanned procedures with improved and superior outcomes. Rather than improvise during surgery, surgery and its procedures can be preconceptualized with superior outcomes and decreased patient morbidity.
Download or read book Science Abstracts written by and published by . This book was released on 1993 with total page 980 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Download or read book Physics Briefs written by and published by . This book was released on 1994 with total page 1146 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Computed Tomography written by Willi A. Kalender and published by John Wiley & Sons. This book was released on 2011-07-07 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book offers a comprehensive and user-oriented description of the theoretical and technical system fundamentals of computed tomography (CT) for a wide readership, from conventional single-slice acquisitions to volume acquisition with multi-slice and cone-beam spiral CT. It covers in detail all characteristic parameters relevant for image quality and all performance features significant for clinical application. Readers will thus be informed how to use a CT system to an optimum depending on the different diagnostic requirements. This includes a detailed discussion about the dose required and about dose measurements as well as how to reduce dose in CT. All considerations pay special attention to spiral CT and to new developments towards advanced multi-slice and cone-beam CT. For the third edition most of the contents have been updated and latest topics like dual source CT, dual energy CT, flat detector CT and interventional CT have been added. The enclosed CD-ROM again offers copies of all figures in the book and attractive case studies, including many examples from the most recent 64-slice acquisitions, and interactive exercises for image viewing and manipulation. This book is intended for all those who work daily, regularly or even only occasionally with CT: physicians, radiographers, engineers, technicians and physicists. A glossary describes all the important technical terms in alphabetical order. The enclosed DVD again offers attractive case studies, including many examples from the most recent 64-slice acquisitions, and interactive exercises for image viewing and manipulation. This book is intended for all those who work daily, regularly or even only occasionally with CT: physicians, radiographers, engineers, technicians and physicists. A glossary describes all the important technical terms in alphabetical order.
Download or read book Index Medicus written by and published by . This book was released on 2004 with total page 2520 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vols. for 1963- include as pt. 2 of the Jan. issue: Medical subject headings.
Download or read book Principles of Computerized Tomographic Imaging written by Avinash C. Kak and published by SIAM. This book was released on 2001-01-01 with total page 335 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive, tutorial-style introduction to the algorithms necessary for tomographic imaging.
Download or read book Introduction to Computed Tomography written by Lois E. Romans and published by Lippincott Williams & Wilkins. This book was released on 1995 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: Takes technical process of CT scanning and breaks it down to digestible components. Provides technical detail essential to understanding the modality.
