7,887 research outputs found
Application of CT in Diagnosing Carcinoma of the Maxillary Sinuses : PART 2: An Experimental Study of Pitfalls Encountered when Diagnosing Carcinoma of the Maxillary Sinuses with CT
No full text1982-03A phantom simulating the transverse section of the maxillary sinuses was constructed for experimentation with various CT scanners to study the following: (1) the occasional inability to image the very thin posterior-lateral walls which have no real bone defects, and (2) to verify whether or not the bony walls surrounding the maxillary sinuses are actually as thick as they appear on CT. The phantom was made of an acrylic cylinder containing three cavities simulating the maxillary sinuses and the nasal cavity and filled with water. The walls, made of thin aluminum and acrylic plates and placed between water and air, disappeared in some CT images. The thickness of the walls calculated from CT values was greater than the true thickness imaged by each CT scanner. The author stresses that in CT images, either experimentally or clinically, thin bony walls placed between water and air or fat tend to disappear, and that bony walls tend to appear thicker than their true thickenss.departmental bulletin pape
An approach to increasing the resolution of industrial CT images based on an aperture collimator
No full textThe spatial resolution of CT images is dominated by the focal spot size when it is large relative to the detector cells. We propose an approach to increase the spatial resolution by utilizing an aperture collimator. The aperture collimator is specially designed and placed in front of the X-ray source so that the rays penetrating the collimator form a set of narrow fan beams. Then an iterative algorithm is introduced to reconstruct CT images from the data obtained by scanning the narrow fan beams. Numerical experiments show that the proposed approach could significantly increase the resolution of the CT images. Furthermore, this approach is also robust against some challenging cases, such as the examination of low contrast object, reconstruction based on multi-energy data and perturbation of geometric errors in CT systems. (C) 2013 Optical Society of AmericaOpticsSCI(E)EI1ARTICLE2327946-279632
Author Co-Citation Analysis (ACA): a powerful tool for representing implicit knowledge of scholar knowledge workers
No full textIn the last decade, knowledge has emerged as one of the most important and valuable organizational assets. Gradually this importance caused to emergence of new discipline entitled ―knowledge management‖. However one of the major challenges of knowledge management is conversion implicit or tacit knowledge to explicit knowledge. Thus Making knowledge visible so that it can be better accessed, discussed, valued or generally managed is a long-standing objective in knowledge management. Accordingly in this paper author co- citation analysis (ACA) will be proposed as an efficient technique of knowledge visualization in academia (Scholar knowledge workers)
Verbeterde beeldreconstructie bij CT-scanners
No full textDe CT-scanner heeft een belangrijke rol in de medische wereld. Helaas gebruikt de CT-scanner voor het opstellen van een scan schadelijke straling. In dit onderzoek is nagegaan of er een betere beeldreconstructietechniek te vinden is voor het opstellen van een CT-afbeelding met gebruik van minder straling.De standaard voor het opstellen van een CT-afbeelding is het gebruik van de 2-norm. Vergelijken we de CT-afbeeldingen geconstrueerd met de 2-norm met CT-afbeeldingen geconstrueerd met de 1-norm en 0.5-norm dan zien we dat de 1-norm visueel het beste resultaat oplevert.Naast het vergelijken van de verschillende normen hebben we ook verschillende epsilon-regularisatiemethodes bekeken. De numerieke experimenten met de verschillende epsilon-regularisatiemethodes hebben we uitgevoerd op een systeem met 0%, 3% en 10% ruis, om te onderzoeken welke methode het beste toepasbaar is in de praktijk. Van de door ons geteste epsilon-regularisatiemethodes bleek de epsilon-regularisatie met epsilon := epsilon/2 met startwaarde epsilon = 10^(-8) en gebruik van de 1-norm de meest geschikte methode om een onderbepaald CT-probleem op te lossen
Palaeoflood and floodplain records from Spain: Evidence for long-term climate variability and environmental changes
No full text10 páginas, 5 figuras, 1 tabla.-- El PDF del artículo es la versión manuscrita del autor.Palaeoflood chronologies from seven Spanish river basins and floodplain aggradation chronologies from thirteen rivers are analysed. These fluvial records were divided in to two sub-sets, namely Atlantic (10 ka record) and Mediterranean (3 ka record) river basins, which represent distinct modern hydroclimatic conditions. In Atlantic basins floods result from intense, widespread rainfalls associated with Atlantic frontal systems transported by westerly airflow. Mediterranean river flooding is related to heavy rainfall induced by mesoscale convective systems (MCSs) during autumn months. Evidence from radiocarbon dates in slackwater flood deposits shows six periods of flood clusters at 10,750–10,240; 9550–9130; 4820–4440; 2865–2350; 960–790; and 520–290 cal BP. Despite the different flood-producing weather conditions in Atlantic and Mediterranean rivers, the radiocarbon sample clusters overlap and indicate changes in large-scale atmospheric circulation and climatic conditions in the Iberian Peninsula. Comparison with proxy records of mean temperature for the Northern Hemisphere demonstrates a relationship between the period of slackwater flood deposition and cold climatic phases (e.g. the 2650 yr BP climatic event or AD 1590–1650 period of the Little Ice Age). Radiocarbon dates from aggraded floodplain sediments were clustered at 2710–2320, 2000–1830, and 910–500 cal BP. The first cluster period is in phase with the timing of slackwater deposition, whereas the third (910–500 cal BP) occurs in between two periods of increased flood frequency as indicated by the palaeoflood and documentary flood records. It is argued that the 910–500 cal BP floodplain aggradation period reflects the first post-Roman evidence of environmental change related to generalised land-use changes at the catchment scale, which produced high sediment load transported to overbank areas during high flows.This palaeoflood research has been funded by the European Commission through the projects “Systematic, Palaeoflood and Historical data for the improvEment of flood Risk Estimation — SPHERE” (contract no. EVG1-CT-1999-00010) and “FloodWater recharge of alluvial Aquifers in Dryland Environments — WADE (contract no. GOCE-CT-2003-506680). The Spanish Commission of Science and Technology funded the project “Incorporation of palaeoflood and historical flood data in the calculation of dam safety — PALEOCAP” (CICYT project no. REN2001-1633-RIES), and the project “Infiltration on channel beds and recharge of aquifers related to floods and palaeofloods in ephemeral rivers — PALEOREC” (CICYT project no.CGL2005-01977/HID).Peer reviewe
MRI-based synthetic CT in the detection of knee osteoarthritis: Comparison with CT
No full textMagnetic resonance Imaging is the gold standard for assessment of soft tissues; however, X-ray-based techniques are required for evaluating bone-related pathologies. This study evaluated the performance of synthetic computed tomography (sCT), a novel MRI-based bone visualization technique, compared with CT, for the scoring of knee osteoarthritis. sCT images were generated from the 3T T1-weighted gradient-echo MR images using a trained machine learning algorithm. Two readers scored the severity of osteoarthritis in tibiofemoral and patellofemoral joints according to OACT, which enables the evaluation of osteoarthritis, from its characteristics of joint space narrowing, osteophytes, cysts and sclerosis in CT (and sCT) images. Cohen's κ was used to assess the interreader agreement for each modality, and intermodality agreement of CT- and sCT-based scores for each reader. We also compared the confidence level of readers for grading CT and sCT images using confidence scores collected during grading. Inter-reader agreement for tibiofemoral and patellofemoral joints were almost-perfect for both modalities (κ = 0.83–0.88). The intermodality agreement of osteoarthritis scores between CT and sCT was substantial to almost-perfect for tibiofemoral (κ = 0.63 and 0.84 for the two readers) and patellofemoral joints (κ = 0.78 and 0.81 for the two readers). The analysis of diagnosis confidence scores showed comparable visual quality of the two modalities, where both are showing acceptable confidence levels for scoring OA. In conclusion, in this single-center study, sCT and CT were comparable for the scoring of knee OA.</p
Morphology of <i>Pulleniatina </i>(planktonic foraminifera) from optical microscopy, micro-CT, and SEM investigations
No full textPulleniatina is a genus of planktonic foraminifera that is widely used in biostratigraphic and palaeoceanographic studies. In our taxonomy, it comprises six morphospecies, alphabetically P. finalis, P. obliquiloculata, P. praecursor, P. praespectabilis, P. primalis, and P. spectabilis. Standard methods of taxonomic discrimination rely on descriptive characteristics of the adult test, such as the shape of the chambers, the shape and position of the primary aperture, the number of chambers per whorl, the height of the spire, the degree of involution, and the irregularity of coiling (“streptospirality”). Here, we illustrate representative specimens of each morphospecies and the likely ancestor, Neogloboquadrina acostaensis, from International Ocean Discovery Program (IODP) Site U1488 (Eauripik Rise, western equatorial Pacific Ocean) using light microscopy and X-ray microcomputed tomography (micro-CT). For each specimen, we provide multifocus light microscope images in three standard orientations, a set of up to 2000 X-radiographs, and a rendered three-dimensional (3D) model that can be viewed externally, internally, and in any cross-section using widely available freeware. We also include labelled images distinguishing each successive chamber and quantify the chamber volumes, the rate of size increase, the aspect ratios, and the angles at which they are added. A second set of specimens was crushed and imaged using scanning electron microscopy (SEM) to further study the internal morphology and wall texture. We use these observations to document the comparative ontogeny and test structure of the six Pulleniatina morphospecies in the context of an evolutionary model involving two diverging species lineages
Automatic Atlas Based Analysis of Radiotracer Uptake in Bones from Fused Nuclear Imaging/CT Data Sets of Mice
No full textPreclinical in vivo imaging is a powerful tool used for a wide variety of biomedical research applications including oncology, cardiac disease, and neurological disease. Disease physiology can be imaged in vivo with molecular imaging such as PET and SPECT. Quality analysis of molecular in vivo images currently requires an expert technician. The feasibility of large preclinical molecular imaging studies is limited by the man hours required to process the overwhelming amount of data created from preclinical scans. Our proposed solution to the bottle neck of manual image analysis is to implement automation of preclinical molecular image analysis. The method described in this study automatically registers different bone regions of interest in fused molecular imaging/CT scans. Automated analysis can run without supervision from a user, allowing for an increase in image processing throughput compared to manual analysis. The results of this novel image analysis show that atlas based registration of CT data is possible with a moderate degree of accuracy. Using this registration method to generate radiotracer uptake values for different bone groups resulted in mixed success. Bones that are registered first; skull, spine, pelvis, had automated radiotracer uptake measurements that correlated highly with the manual radiotracer uptake measurements. Bones that were last to be registered; tibia, hindpaws, were susceptible to large amounts of variation from the manual radiotracer uptake measurements. Large improvements to the accuracy of the results could be made by ensuring the accuracy of the joint registration of the atlas to the CT dataset
Towards a computer-assisted Computational Thinking (CT) assessment system in higher education
No full textWith the vision to promote CT to a wider group of audiences, this PhD project explores the formative assessment of CT skills in Programming Education to support students to learn CT skills in Higher Education. In this project, we plan to investigate the importance of CT in the context of Higher Education, explore the relationship between CT skills and programming skills, build a model to assess learners' CT skills and develop a computer-assisted assessment system with automated components to enhance students' CT competences in Higher Education. Mixed-method research methodologies will be employed in distinct phases of the project accordingly. A system which allows formative assessment of CT skills will be iteratively designed and constructed throughout the project. The outcome of the project should support the CT learning process, make CT more visible for people from diverse backgrounds and empower them with a CT mindset to embrace the digitalization of society.Web Information System
CT-PPS the program and its possiâ??ble developments
No full textThe CMS-TOTEM Precision Proton Spectrometer (CT-PPS) has the goal of studying central exclusive production processes in proton-proton collisions at LHC. Such processes are characterized by the presence of two protons scattered at small angles and detected inside the LHC beam pipe with CT-PPS, along with one or more particles produced at small rapidity values and detected by the central CMS detector. This gives access to a variety of interesting subjects, including the study of quartic gauge couplings and searches for new resonances produced in photon-photon or gluon-gluon fusion. A description of the experimental set-up will be presented, along with the current status of the project
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