Search results for "STED"
showing 10 items of 2256 documents
Simulated one-pass list-mode: an approach to on-the-fly system matrix calculation.
2013
In the development of prototype systems for positron emission tomography a valid and robust image reconstruction algorithm is required. However, prototypes often employ novel detector and system geometries which may change rapidly under optimization. In addition, developing systems generally produce highly granular, or possibly continuous detection domains which require some level of on-the-fly calculation for retention of measurement precision. In this investigation a new method of on-the-fly system matrix calculation is proposed that provides advantages in application to such list-mode systems in terms of flexibility in system modeling. The new method is easily adaptable to complicated sy…
Estimation of the elastic parameters of human liver biomechanical models by means of medical images and evolutionary computation.
2013
This paper presents a method to computationally estimate the elastic parameters of two biomechanical models proposed for the human liver. The method is aimed at avoiding the invasive measurement of its mechanical response. The chosen models are a second order Mooney–Rivlin model and an Ogden model. A novel error function, the geometric similarity function (GSF), is formulated using similarity coefficients widely applied in the field of medical imaging (Jaccard coefficient and Hausdorff coefficient). This function is used to compare two 3D images. One of them corresponds to a reference deformation carried out over a finite element (FE) mesh of a human liver from a computer tomography image, …
Calculating minimum discrepancy to assess the nestedness of species assemblages
2009
Nestedness is a pattern whereby species-poor assemblages are composed of subsets of the species occurring in richer assemblages. One of the most commonly used measures of the degree of nestedness for presence-absence matrices is the ‘discrepancy’ metric. A hitherto neglected property of that metric is that it may take several values for a given site-by-species matrix in the presence of ties in the marginal totals. This complicates the quantification of nestedness for the observed presence-absence matrix, as well as the assessment of statistical significance, which is typically achieved through Monte Carlo simulations. A solution to the problem is to calculate the minimum discrepancy using a…
A laser ion source for trace analysis
1988
A laser ion source has been set up which is based on resonant stepwise excitation and ionization of atomic vapor confined in an ionization chamber. Using a pulsed copper vapor/dye laser system with a high repetition rate (6.5 kHz) one expects high efficiency and high selectivity for this new type of ion source. First test experiments with lead are reported.
Production of negative osmium ions by laser desorption and ionization.
2010
The interest to produce negative osmium ions is manifold in the realm of high-accuracy ion trap experiments: high-resolution nearly Doppler-free laser spectroscopy, antihydrogen formation in its ground state, and contributions to neutrino mass spectrometry. Production of these ions is generally accomplished by sputtering an Os sample with Cs(+) ions at tens of keV. Though this is a well-established method commonly used at accelerators, these kind of sources are quite demanding and tricky to operate. Therefore, the development of a more straightforward and cost effective production scheme will be of benefit for ion trap and other experiments. Such a scheme makes use of desorption and ionizat…
Advantages of fitting contrast curves using logistic function: a technical note.
2013
Objective The aim of this article is to demonstrate how the contrast properties of an imaging system can be ideally fitted with the use of stripe patterns and the logistic function. Study Design Stripe patterns with defined amounts of line pairs (lp/mm) per mm (10-20 lp/mm) were recorded with the use of digital photostimulable storage phosphor. Scan data and normalized image data were analyzed with the use of ImageJ and MatLab to calculate different contrast curves. Results For original scan data, the goodness of fit was 0.0000019 (sum of squared error [SSE]). The R-square was 0.9998. For normalized data the goodness of fit was 0.0007 (SSE) and the R-square 0.998. An amount of 50% contrast …
New, fast, and accurate procedure to calibrate a 2-dimensional digital measurement method.
2005
Traditionally, dental casts have been measured by hand, with conventional calipers. Today, several digital methods are available for automatically measuring tooth size, but their accuracy depends on proper calibration. The purpose of this article is to introduce a fast and accurate procedure to calibrate a previously introduced 2-dimensional computerized system of measuring mesiodistal tooth size and calculating overall and anterior Bolton ratios. In this calibration method, the cast is digitized while sitting on a sheet of graph paper. The magnification of the paper in 2 axes can be easily calculated and hence the magnification of the dental cast digital image.
The decision support system for telemedicine based on multiple expertise
1998
This paper discusses the application of artificial intelligence in telemedicine and some of our research results in this area. The main goal of our research is to develop methods and systems to collect, analyse, distribute and use medical diagnostics knowledge from multiple knowledge sources and areas of expertise. Use of modern communication tools enable a physician to collect and analyse information obtained from experts worldwide with the help of a decision support medical system. In this paper we discuss a multilevel representation and processing of medical data using a system which evaluates and exploits knowledge about the behaviour of statistical diagnostics methods. The presented te…
Computer-assisted Interventions on Basic Number Skills
2014
Computer-assisted interventions (CAI) on basic number skills have been studied over the last 70 years. The technical development from large, room-sized, mainframe computers to handhelds is revising the school pedagogy in a similar fashion to what school books once did. Computers provide a tool for delivering instruction, but still the contents of CAI have followed on the ruling pedagogical trends of the time. The basic models of repetitive practice to gain arithmetic fluency and problem solving–oriented discovery learning can be found from CAI on numerical skills. The increasing knowledge about educational neuroscience has not changed these models, but turned the attention to the details in…
Accelerating decoding-related skills in poor readers learning a foreign language: a computer-based intervention
2013
The results of Fast ForWord® training on English decoding-related skills were examined. Finnish fifth-grade students were identified as having reading fluency problems and poor skills in English as a foreign language learned at school and were randomly assigned to either a training group (TRG) or a control group. The TRG (n = 13) received 50 min of daily computer program-based training for a period of approximately 10 weeks. Students in the first control group (n = 11) received the school’s regular instructional programme. A second control group was composed of 14 average readers. The students’ English skills were examined in pre-test, post-test and follow-up measurements. The TRG students …