7,122 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
Risk of hematological malignancies from CT radiation exposure in children, adolescents and young adults
No full textAuthor Correction: Risk of hematological malignancies from CT radiation exposure in children, adolescents and young adults : 10.1038/s41591-025-03689-5International audienceOver one million European children undergo computed tomography (CT) scans annually. Although moderate- to high-dose ionizing radiation exposure is an established risk factor for hematological malignancies, risks at CT examination dose levels remain uncertain. Here we followed up a multinational cohort (EPI-CT) of 948,174 individuals who underwent CT examinations before age 22 years in nine European countries. Radiation doses to the active bone marrow were estimated on the basis of body part scanned, patient characteristics, time period and inferred CT technical parameters. We found an association between cumulative dose and risk of all hematological malignancies, with an excess relative risk of 1.96 (95% confidence interval 1.10 to 3.12) per 100 mGy (790 cases). Similar estimates were obtained for lymphoid and myeloid malignancies. Results suggest that for every 10,000 children examined today (mean dose 8 mGy), 1–2 persons are expected to develop a hematological malignancy attributable to radiation exposure in the subsequent 12 years. Our results strengthen the body of evidence of increased cancer risk at low radiation doses and highlight the need for continued justification of pediatric CT examinations and optimization of doses
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
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
Who is to teach “these guys” to “shoot less?”
No full textSpecial Edition issue - Terrorism and Counter-Terrorism in Sub-Saharan AfricaWhile conducting research on counter-terrorism (CT) systems of the Central and Eastern European Member States of the European Union, a unique perspective on the European involvement in countering terrorism in Sub-Saharan Africa was offered to the author by a Czech defence ministry official. In his view, the fact that his country made a decision to contribute “boots on the ground” to the European Union Training Mission in Mali (EUTM Mali) was astonishing, to say the least: “Things like Mali, you sometimes wonder how these thing happen, even if you are part of them (Havranek 2013).” Thus a decision to participate in this latest CT motivated (building a Malian military capable of taking on the jihadists of Al Qaeda in the Islamic Maghreb, AQIM) EU venture in Africa seems not to have been preceded by a careful analysis and weighting of the options on behalf of his country. In fact, it seemed like a knee jerk reaction to a call for troops from France and subsequently from Brussels. In the end, we might even speculate if, in this very case, the Czech Republic duly settled on a number of troops to be sent to Mali (very low – in dozens) and comfortably ticked off the box on its involvement in yet another Common Security and Defence Policy (CSDP) military mission in Africa, and its contribution to external aspects of combating terrorism on EU level.Publisher PD
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