Dissertations / Theses on the topic 'Dynamic X-ray imaging'
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Lee, Tiffany (Tiffany Ting). "Long range x-ray imaging utilizing coded aperture techniques and dynamic reconstruction." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44837.
Full textIncludes bibliographical references (p. 50).
Improvised explosive devices (IED) pose a very serious threat to civilians and military forces around the world, and new technologies must be developed for the early detection of these objects. Because of the high concentrations of low atomic number material such as nitrogen and hydrogen present in these explosives, x-ray backscattering provides a viable method of collecting information about these targets by analyzing their shape. Furthermore, a coded aperture used in conjunction with dynamic reconstruction algorithms offers high sensitivity and resolution even while the target is moving towards the detector. This paper describes a lab-based system that simulated a source-target-detector arrangement to be utilized in a radiation detecting vehicle in order to test dynamic reconstruction methods. Using a 225 kVp x-ray tube as the source, a medical CT-system camera fitted with a drill mask of 50% fill factor as the detector, and both radioisotope sources and low Z backscatter targets, images were acquired and reconstructed. The geometry of the experimental setup was optimized to reduce background noise from air scatter and environmental sources, as well as to prevent incident photons from directly reaching the detector from the x-ray tube. Measurements of a Co-60 point source and Co-57 area source with high activity generated high contrast images for which the shapes of the sources were clearly resolved. Acquisitions with varying target-detector distance of low Z materials, including a filled water jug and a four inch thick polyethylene arrow, produced lower contrast images in which the shapes were not as easily distinguished. The radioisotope tests were a proof of principle for dynamic reconstruction and the backscatter targets provided much insight on methods for improving the lab system, including the addition of steel behind the target, the narrowing of the detector energy window, and reassessment of the x-ray cone-beam.
by Tiffany Lee.
S.B.
Jones, Cameron Christopher. "VALIDATION OF COMPUTATIONAL FLUID DYNAMIC SIMULATIONS OF MEMBRANE ARTIFICIAL LUNGS WITH X-RAY IMAGING." UKnowledge, 2012. http://uknowledge.uky.edu/cbme_etds/2.
Full textGradl, Regine [Verfasser], Franz [Akademischer Betreuer] Pfeiffer, Jan J. [Gutachter] Wilkens, and Franz [Gutachter] Pfeiffer. "Dynamic Phase-Contrast X-ray Imaging at an Inverse Compton Source / Regine Gradl ; Gutachter: Jan J. Wilkens, Franz Pfeiffer ; Betreuer: Franz Pfeiffer." München : Universitätsbibliothek der TU München, 2019. http://d-nb.info/1200547918/34.
Full textChembrolu, Venkatesh. "Time-resolved X-ray imaging of magnetization dynamics in spin transfer torque devices /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Full textTan, Dongyue. "In situ ultrafast synchrotron X-ray imaging studies of the dynamics of ultrasonic bubbles in liquids." Thesis, University of Hull, 2015. http://hydra.hull.ac.uk/resources/hull:12399.
Full textÖstlin, Christofer. "Single-molecule X-ray free-electron laser imaging : Interconnecting sample orientation with explosion data." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-231009.
Full textCaleman, Carl. "Towards Single Molecule Imaging - Understanding Structural Transitions Using Ultrafast X-ray Sources and Computer Simulations." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7915.
Full textJönsson, Olof. "Ultrafast Structural and Electron Dynamics in Soft Matter Exposed to Intense X-ray Pulses." Doctoral thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-331936.
Full textBell, Jayna T. (Jayna Teresa). "Detection of improvised explosive devices at long-range using coded aperture imaging of backscattered X-rays with dynamic reconstruction." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/53279.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (p. 117-118).
Standoff detection of improvised explosive devices (IEDs) is a continuing problem for the U.S. military. Current X-ray detection systems cannot detect explosives at distances above a few meters and with a source-detector system moving in relation to the target. The aim of this study is to determine the feasibility of a large-area, Coded-Aperture Imaging (CAI) system using X-Ray backscatter as the source of radiation. A moving source-detector system required development of a new reconstruction technique, dynamic reconstruction (DR), which continually back-projects detected events on an event-by-event basis. This research imaged multiple low-Z (polyethylene and water-filled), area targets with backscattered X-rays using standard medical imaging equipment, coded aperture masks with ideal bi-level autocorrelation properties, and dynamic reconstruction (DR). Lower fill factor apertures were the primary metric investigated because contrast was shown to be inversely related to the mask's percentage of open area. This study experimentally determined the optimal mask fill factor, gamma camera imaging protocols, and experimental geometry by examining the resulting effects on image quality. Reconstructed images were analyzed for Contrast-to-noise ratio (CNR), Signal-to-noise Ratio (SNR), resolution, sharpness, the uniformity of the background (artifacts). In addition to changing the fill factor, additional methods of improving the contrast included changing the experimental geometry, reducing the X-ray tube filtration, and widening the X-ray source's cone beam (FOV).
(cont.) 14 studies were performed that found 25% fill factor mask reconstructions had the highest average CNR (14.7), compared to 50% and 12.5% fill factor (CNRs 8.50 and 6.9, respectively) with a system resolution of 25 mm at the target. Thus, this study's techniques confirmed that large-area, low fill factor coded apertures could successfully be used, in conjunction with dynamic reconstruction, to image complex, extended scenes at 5 meters with capabilities of up to 50 meters or more.
by Jayna T. Bell.
S.M.
Mohee, Lakshana. "Collagen scaffolds for tissue engineering : the relationship between microstructure, fluid dynamics, mechanics and scaffold deformation." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/276980.
Full textEliah, Dawod Ibrahim. "Structural integrity of highly ionized peptides." Thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-387886.
Full textGnodtke, Christian. "Dynamik endlicher Vielteilchen-Systeme in intensiven Röntgenlaserpulsen." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-67676.
Full textGnodtke, Christian. "Dynamik endlicher Vielteilchen-Systeme in intensiven Röntgenlaserpulsen." Doctoral thesis, Max-Planck-Institut für Physik komplexer Systeme, 2010. https://tud.qucosa.de/id/qucosa%3A25554.
Full textCandau, Nicolas. "Compréhension des mécanismes de cristallisation sous tension des élastomères en conditions quasi-statiques et dynamiques." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0057/document.
Full textStrain induced crystallization (SIC) of Natural Rubber (NR) has been the subject of a large number of studies since its discovery in 1929. However, the literature is very poor concerning the study of SIC when samples are deformed with a stretching time in the range of the SIC characteristic time (around 10msec-100msec). Thus, the aim of this thesis is to contribute to the understanding of the SIC phenomenon thanks to dynamic tensile tests at high strain rates. To meet this goal, we have developed a dynamic tensile test machine allowing stretching samples of elastomers at strain rates up to 290 s-1. The tests are carried out on four NR with different sulphur amount, two NR with different carbon black filler amounts. We also studied a synthetic rubber made of polyisoprene chains (IR) able to crystallize under strain. Dynamic tests are relatively difficult to interpret; a significant work has thus been first performed at slow strain rate. Moreover, the experiments are coupled with a thermodynamic approach. First, the general mechanisms associated to the crystallization are identified as follows: during mechanical loading or during cooling in the deformed state, SIC is the result of successive appearance of crystallite populations whose nucleation and growth depend on the local network density. Crystallization is enhanced when the cycle is performed above the melting stretching ratio. This phenomenon is attributed to a memory effect due to a permanent alignment of the chains. Finally, the effect of the strain rate is theoretically described thanks to a diffusion term. This approach, coupled with experiments suggests that SIC is mainly governed by the nucleation kinetics. For the dynamic test, the combination of the memory effect and the acceleration of the melting during the cycle lead to a reduction or even disappearance of the crystalline hysteresis. In addition, self-heating, which progressively increases with the frequency of the cycle, causes the delay of the melting stretching ratio. This well explains why the crystallinity index decreases at the minimum stretching ratio of the dynamic cycles when the frequency increases. We finally compared the ability of our different rubbers to crystallize at high strain rates. SIC is enhanced for the weakly crosslinked rubber. This might be related to the dynamics of its free entanglements, these ones acting as supplementary crosslinks at high strain rates. Then, a filled rubber is compared to the unfilled one. We found that the filled sample has a lower ability to crystallize at high strain rates as compared to the unfilled one. This is likely due to the strong self-heating at the interface between the fillers and the rubbery matrix. Finally, we observe a convergence of crystallization kinetics in natural and synthetic rubbers at high strains and high strain rates. This is attributed to the predominance of the entropic energy in the nucleation kinetics in these experimental conditions
Molloi, Sabee Y. "Dynamic dual-energy X-ray techniques for cardiac imaging." 1987. http://catalog.hathitrust.org/api/volumes/oclc/44856483.html.
Full textTypescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 153-168).
Gislason-Lee, Amber J., B. Hoornaert, A. R. Cowen, and A. G. Davies. "Understanding automated dose control in dynamic X-ray imaging systems." 2013. http://hdl.handle.net/10454/16960.
Full text(9713912), Junyu Wang. "APPLICATION OF X-RAY DIGITAL IMAGE CORRELATION (XDIC) ON MATERIALS WITH ENGINEERED SPECKLES." Thesis, 2020.
Find full textHung, Chi-Yuan, and 洪齊元. "Investigation of X-ray multiple Diffraction for Macromolecular Crystals: Stereoscopic multi-beam Imaging & Dynamical calculation." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/19508872767190776100.
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