920 resultados para diagnostic tests


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Previous studies have revealed considerable interobserver and intraobserver variation in the histological classification of preinvasive cervical squamous lesions. The aim of the present study was to develop a decision support system (DSS) for the histological interpretation of these lesions. Knowledge and uncertainty were represented in the form of a Bayesian belief network that permitted the storage of diagnostic knowledge and, for a given case, the collection of evidence in a cumulative manner that provided a final probability for the possible diagnostic outcomes. The network comprised 8 diagnostic histological features (evidence nodes) that were each independently linked to the diagnosis (decision node) by a conditional probability matrix. Diagnostic outcomes comprised normal; koilocytosis; and cervical intraepithelial neoplasia (CIN) 1, CIN II, and CIN M. For each evidence feature, a set of images was recorded that represented the full spectrum of change for that feature. The system was designed to be interactive in that the histopathologist was prompted to enter evidence into the network via a specifically designed graphical user interface (i-Path Diagnostics, Belfast, Northern Ireland). Membership functions were used to derive the relative likelihoods for the alternative feature outcomes, the likelihood vector was entered into the network, and the updated diagnostic belief was computed for the diagnostic outcomes and displayed. A cumulative probability graph was generated throughout the diagnostic process and presented on screen. The network was tested on 50 cervical colposcopic biopsy specimens, comprising 10 cases each of normal, koilocytosis, CIN 1, CIN H, and CIN III. These had been preselected by a consultant gynecological pathologist. Using conventional morphological assessment, the cases were classified on 2 separate occasions by 2 consultant and 2 junior pathologists. The cases were also then classified using the DSS on 2 occasions by the 4 pathologists and by 2 medical students with no experience in cervical histology. Interobserver and intraobserver agreement using morphology and using the DSS was calculated with K statistics. Intraobserver reproducibility using conventional unaided diagnosis was reasonably good (kappa range, 0.688 to 0.861), but interobserver agreement was poor (kappa range, 0.347 to 0.747). Using the DSS improved overall reproducibility between individuals. Using the DSS, however, did not enhance the diagnostic performance of junior pathologists when comparing their DSS-based diagnosis against an experienced consultant. However, the generation of a cumulative probability graph also allowed a comparison of individual performance, how individual features were assessed in the same case, and how this contributed to diagnostic disagreement between individuals. Diagnostic features such as nuclear pleomorphism were shown to be particularly problematic and poorly reproducible. DSSs such as this therefore not only have a role to play in enhancing decision making but also in the study of diagnostic protocol, education, self-assessment, and quality control. (C) 2003 Elsevier Inc. All rights reserved.

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We report on a study comparing absolute K-alpha yield from Ti foils measured with a calibrated system of an X-ray CCD coupled to a curved LiF Von-Hamos crystal spectrometer to the difference in the signals measured simultaneously with two similar photodiodes fitted with two different filters. Our data indicate that a combination of photodiodes with different filters could be developed into an alternative and inexpensive diagnostic for monitoring single shot pulsed emission in a narrow band of X-ray region.

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One of the most decisive factors in the quality of education and academic performance of students is quality, preparation and dedication of the teachers. The exquisite system of selecting candidates for teacher training programs is one of the fundamentals of success of the Finnish Education System. The responsibility of choosing the best students to convert them into teachers is a challenge that involves a significant reform of university admission. Achieving this goal involves the choice of strategies and educational tools in accordance to the complexity of the demands presented by the teaching profession in the digital age. This study describes, analyzes and compares the admission tests in the University of Spain (PAU) and Finland (VAKAVA), for those who wish to become professional educators, in order to understand the possible influence of these tests to select the most suitable candidates to develop into future teaching professionals. The results showed that in Spain, the entrance test to universities is developed in a general way for all the students that aspire to any field of knowledge, while in Finland, the test is specific and particular for students aspiring to the field of education. The results of this study can guide and encourage the necessary changes that have to be done in the admission tests to Spanish university in general and to teacher education faculties in particular.

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Phase resolved optical emission spectroscopy (PROES) bears considerable potential for diagnostics of RF discharges that give detailed insight of spatial and temporal variations of excitation processes. Based on phase and space resolved measurements of the population dynamics of excited states several diagnostic techniques have been developed. Results for a hydrogen capacitively coupled RF (CCRF) discharge are discussed as an example. The gas temperature, the degree of dissociation and the temporally and spatially resolved electron energy distribution function (EEDF) of energetic electrons (>12eV) are measured. Furthermore, the pulsed electron impact excitation during the field reversal phase, typical for hydrogen CCRF discharges, is exploited for measurements of atomic and molecular data like lifetimes of excited states, coefficients for radiationless collisional de-excitation (quenching coefficients), and cascading processes from higher electronic states.