1,246 research outputs found
Application of Multifractal Analysis to Segmentation of Water Bodies in Optical and Synthetic Aperture Radar Satellite Images
A method for segmenting water bodies in optical and synthetic aperture radar
(SAR) satellite images is proposed. It makes use of the textural features of
the different regions in the image for segmentation. The method consists in a
multiscale analysis of the images, which allows us to study the images
regularity both, locally and globally. As results of the analysis, coarse
multifractal spectra of studied images and a group of images that associates
each position (pixel) with its corresponding value of local regularity (or
singularity) spectrum are obtained. Thresholds are then applied to the
multifractal spectra of the images for the classification. These thresholds are
selected after studying the characteristics of the spectra under the assumption
that water bodies have larger local regularity than other soil types.
Classifications obtained by the multifractal method are compared quantitatively
with those obtained by neural networks trained to classify the pixels of the
images in covered against uncovered by water. In optical images, the
classifications are also compared with those derived using the so-called
Normalized Differential Water Index (NDWI)
Who Learns Better Bayesian Network Structures: Accuracy and Speed of Structure Learning Algorithms
Three classes of algorithms to learn the structure of Bayesian networks from
data are common in the literature: constraint-based algorithms, which use
conditional independence tests to learn the dependence structure of the data;
score-based algorithms, which use goodness-of-fit scores as objective functions
to maximise; and hybrid algorithms that combine both approaches.
Constraint-based and score-based algorithms have been shown to learn the same
structures when conditional independence and goodness of fit are both assessed
using entropy and the topological ordering of the network is known (Cowell,
2001).
In this paper, we investigate how these three classes of algorithms perform
outside the assumptions above in terms of speed and accuracy of network
reconstruction for both discrete and Gaussian Bayesian networks. We approach
this question by recognising that structure learning is defined by the
combination of a statistical criterion and an algorithm that determines how the
criterion is applied to the data. Removing the confounding effect of different
choices for the statistical criterion, we find using both simulated and
real-world complex data that constraint-based algorithms are often less
accurate than score-based algorithms, but are seldom faster (even at large
sample sizes); and that hybrid algorithms are neither faster nor more accurate
than constraint-based algorithms. This suggests that commonly held beliefs on
structure learning in the literature are strongly influenced by the choice of
particular statistical criteria rather than just by the properties of the
algorithms themselves.Comment: 27 pages, 8 figure
Personalized Event Prediction for Electronic Health Records
Clinical event sequences consist of hundreds of clinical events that
represent records of patient care in time. Developing accurate predictive
models of such sequences is of a great importance for supporting a variety of
models for interpreting/classifying the current patient condition, or
predicting adverse clinical events and outcomes, all aimed to improve patient
care. One important challenge of learning predictive models of clinical
sequences is their patient-specific variability. Based on underlying clinical
conditions, each patient's sequence may consist of different sets of clinical
events (observations, lab results, medications, procedures). Hence, simple
population-wide models learned from event sequences for many different patients
may not accurately predict patient-specific dynamics of event sequences and
their differences. To address the problem, we propose and investigate multiple
new event sequence prediction models and methods that let us better adjust the
prediction for individual patients and their specific conditions. The methods
developed in this work pursue refinement of population-wide models to
subpopulations, self-adaptation, and a meta-level model switching that is able
to adaptively select the model with the best chance to support the immediate
prediction. We analyze and test the performance of these models on clinical
event sequences of patients in MIMIC-III database.Comment: arXiv admin note: text overlap with arXiv:2104.0178
An overview of decision table literature.
The present report contains an overview of the literature on decision tables since its origin. The goal is to analyze the dissemination of decision tables in different areas of knowledge, countries and languages, especially showing these that present the most interest on decision table use. In the first part a description of the scope of the overview is given. Next, the classification results by topic are explained. An abstract and some keywords are included for each reference, normally provided by the authors. In some cases own comments are added. The purpose of these comments is to show where, how and why decision tables are used. Other examined topics are the theoretical or practical feature of each document, as well as its origin country and language. Finally, the main body of the paper consists of the ordered list of publications with abstract, classification and comments.
Integration of Temporal Abstraction and Dynamic Bayesian Networks in Clinical Systems. A preliminary approach
Abstraction of temporal data (TA) aims to abstract time-points into higher-level interval concepts and to detect significant trends in both low-level data and abstract concepts. TA methods are used for summarizing and interpreting clinical data. Dynamic Bayesian Networks (DBNs) are temporal probabilistic graphical models which can be used to represent knowledge about uncertain temporal relationships between events and state changes during time. In clinical systems, they were introduced to encode and use the domain knowledge acquired from human experts to perform decision support. A hypothesis that this study plans to investigate is whether temporal abstraction methods can be effectively integrated with DBNs in the context of medical decision-support systems. A preliminary approach is presented where a DBN model is constructed for prognosis of the risk for coronary artery disease (CAD) based on its risk factors and using as test bed a dataset that was collected after monitoring patients who had positive history of cardiovascular disease. The technical objectives of this study are to examine how DBNs will represent the abstracted data in order to construct the prognostic model and whether the retrieved rules from the model can be used for generating more complex abstractions
Proceedings of the Tenth International Workshop on Health Text Mining and Information Analysis (LOUHI 2019)
International audienc
Automatic production and integration of knowledge to the support of the decision and planning activities in medical-clinical diagnosis, treatment and prognosis.
El concepto de procedimiento médico se refiere al conjunto de actividades seguidas por los profesionales de la salud para solucionar o mitigar el problema de salud que afecta a un paciente. La toma de decisiones dentro del procedimiento médico ha sido, por largo tiempo, uno de las áreas más interesantes de investigación en la informática médica y el contexto de investigación de esta tesis. La motivación para desarrollar este trabajo de investigación se basa en tres aspectos fundamentales: no hay modelos de conocimiento para todas las actividades médico-clÃnicas que puedan ser inducidas a partir de datos médicos, no hay soluciones de aprendizaje inductivo para todas las actividades de la asistencia médica y no hay un modelo integral que formalice el concepto de procedimiento médico. Por tanto, nuestro objetivo principal es desarrollar un modelo computable basado en conocimiento que integre todas las actividades de decisión y planificación para el diagnóstico, tratamiento y pronóstico médico-clÃnicos.
Para alcanzar el objetivo principal, en primer lugar, explicamos el problema de investigación. En segundo lugar, describimos los antecedentes del problema de investigación desde los contextos médico e informático. En tercer lugar, explicamos el desarrollo de la propuesta de investigación, basada en cuatro contribuciones principales: un nuevo modelo, basado en datos y conocimiento, para la actividad de planificación en el diagnóstico y tratamiento médico-clÃnicos; una novedosa metodologÃa de aprendizaje inductivo para la actividad de planificación en el diagnóstico y tratamiento médico-clÃnico; una novedosa metodologÃa de aprendizaje inductivo para la actividad de decisión en el pronóstico médico-clÃnico, y finalmente, un nuevo modelo computable, basado en datos y conocimiento, que integra las actividades de decisión y planificación para el diagnóstico, tratamiento y pronóstico médico-clÃnicos.The concept of medical procedure refers to the set of activities carried out by the health care professionals to solve or mitigate the health problems that affect a patient. Decisions making within a medical procedure has been, for a long time, one of the most interesting research areas in medical informatics and the research context of this thesis. The motivation to develop this research work is based on three main aspects: Nowadays there are not knowledge models for all the medical-clinical activities that can be induced from medical data, there are not inductive learning solutions for all the medical-clinical activities, and there is not an integral model that formalizes the concept of medical procedure. Therefore, our main objective is to develop a computable model based in knowledge that integrates all the decision and planning activities for the medical-clinical diagnosis, treatment and prognosis.
To achieve this main objective: first, we explain the research problem. Second, we describe the background of the work from both the medical and the informatics contexts. Third, we explain the development of the research proposal based on four main contributions: a novel knowledge representation model, based in data, to the planning activity in medical-clinical diagnosis and treatment; a novel inductive learning methodology to the planning activity in diagnosis and medical-clinical treatment; a novel inductive learning methodology to the decision activity in medical-clinical prognosis, and finally, a novel computable model, based on data and knowledge, which integrates the
decision and planning activities of medical-clinical diagnosis, treatment and prognosis
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