Impact of Bayesian network model structure on the accuracy of medical diagnostic systems

While Bayesian network models may contain a handful of numerical parameters that are important for their quality, several empirical studies have confirmed that overall precision of their probabilities is not crucial. In this paper, we study the impact of the structure of a Bayesian network on the precision of medical diagnostic systems. We show that also the structure is not that important - diagnostic accuracy of several medical diagnostic models changes minimally when we subject their structures to such transformations as arc removal and arc reversal. © 2014 Springer International Publishing

Zastosowanie dynamicznych rozkładów Gaussowskich przy pomocy algorytmu ewolucji różnicowej

Dynamic Bayesian networks (DBNs) offer a framework for explicit modeling of temporal relationships, and are useful as both prognostic and diagnostic tools. In medicine, for example, they can assist in planning treatment options or in clinical management of patients. They have been also widely applied to genomics and proteomics. This paper shows how dynamic Bayesian networks can be used in a risk assessment in medicine and presents an example of an application to cervical cancer screening. The model is a convenient tool for assessing the risk of cervical precancer and invasive cervical cancer over time. These quantitative risk assessments are helpful for establishing the optimal timing of follow-up screening and are the first step toward generating individualized reevaluation scheduling.Dynamiczne sieci bayesowskie (DBNs) pozwalają na modelowanie zależności czasowych. Modele te są niejednokrotnie używane w prognostyce. Na przykład w medycynie, jako narzędzia do prognozowania czy też planowania terapii. Dynamiczne siecibayesowskie sa˛ też szeroko stosowane w genomice oraz w proteomice. Atrykuł ten opisuje, w jaki sposób dynamiczne sieci bayesowskie mogą być zastosowane w wyznaczaniu ryzyka w medycynie. W pracy przedstawiono przykład zastosowania dynamicznych sieci bayesowskich w profilaktyce raka szyjki macicy. Prezentowany model został zbudowany w oparciu o dwa źródła wiedzy: opinie eksperta oraz dane medyczne. Model ten pozwala na wyznaczanie ryzyka zachorowania na raka szyjki macicy. Wartości ryzyka wyznaczane przez model pozwalają na określenie optymalnego czasu wykonania kolejnych badań przesiewowych oraz na zindywidualizowanie procesu profilaktyki

Pozyskiwanie wiedzy od ekspertów w budowaniu modeli sieci bayesowskich

Knowledge acquisition from experts is a costly and time-consuming task. While domain experts have the necessary knowledge and expertise, they rarely have the experience needed to translate this knowledge into the model. This paper describes typical problems that are encountered by knowledge engineers when building Bayesian network models and illustrates some practical techniques to overcome them. The presented examples capture the problems that occurred during elicitation the numerical parameters of the model for diagnosis of liver disorders.Pozyskiwanie wiedzy od ekspertów jest kosztownym i czasochłonnym zadaniem. Pomimo ogromnej wiedzy i doświadczenia, jakie posiadają eksperci, niejednokrotnie nie potrafią ich przenieść na tworzony model. Poniższy artykuł opisuje przykłady problemów, z jakimi może się zetknąć inżynier wiedzy w trakcie budowania modeli sieci bayesowskich, jak również proponuje rozwiązania tych problemów. Prezentowane przykłady dotyczą problemów, jakie pojawiły się w trakcie pozyskiwania od eksperta parametrów numerycznych modelu sieci bayesowskiej do diagnozowania chorób wątroby

Impact of precision of Bayesian network parameters on accuracy of medical diagnostic systems

Objective: One of the hardest technical tasks in employing Bayesian network models in practice is obtaining their numerical parameters. In the light of this difficulty, a pressing question, one that has immediate implications on the knowledge engineering effort, is whether precision of these parameters is important. In this paper, we address experimentally the question whether medical diagnostic systems based on Bayesian networks are sensitive to precision of their parameters. Methods and materials: The test networks include Hepar II, a sizeable Bayesian network model for diagnosis of liver disorders and six other medical diagnostic networks constructed from medical data sets available through the Irvine Machine Learning Repository. Assuming that the original model parameters are perfectly accurate, we lower systematically their precision by rounding them to progressively courser scales and check the impact of this rounding on the models' accuracy. Results: Our main result, consistent across all tested networks, is that imprecision in numerical parameters has minimal impact on the diagnostic accuracy of models, as long as we avoid zeroes among parameters. Conclusion: The experiments' results provide evidence that as long as we avoid zeroes among model parameters, diagnostic accuracy of Bayesian network models does not suffer from decreased precision of their parameters. © 2013 Elsevier B.V

Bayesian Network Modeling in Discovering Risk Factors of Dental Caries in Three-Year-Old Children

Purpose - The aim of this study was to use probabilistic graphical models to determine dental caries risk factors in three-year-old children. The analysis was conducted on the basis of the questionnaire data and resulted in building probabilistic graphical models to investigate dependencies among the features gathered in the surveys on dental caries. Materials and Methods - The data available in this analysis came from dental examinations conducted in children and from a questionnaire survey of their parents or guardians. The data represented 255 children aged between 36 and 48 months. Self-administered questionnaires contained 34 questions of socioeconomic and medical nature such as nutritional habits, wealth, or the level of education. The data included also the results of oral examination by a dentist. We applied the Bayesian network modeling to construct a model by learning it from the collected data. The process of Bayesian network model building was assisted by a dental expert. Results - The model allows to identify probabilistic relationships among the variables and to indicate the most significant risk factors of dental caries in three-year-old children. The Bayesian network model analysis illustrates that cleaning teeth and falling asleep with a bottle are the most significant risk factors of dental caries development in three-year-old children, whereas socioeconomic factors have no significant impact on the condition of teeth. Conclusions - Our analysis results suggest that dietary and oral hygiene habits have the most significant impact on the occurrence of dental caries in three-year-olds

Probabilistyczny model wspierający wczesne diagnozowanie autyzmu

Bayesian networks are recognized as a suitable tool for modelling diagnostic problems. The power of this modelling is that it can combine knowledge coming from different sources. For example, in case of medical domain, the expert knowledge can be merged along with the medical data. This paper presents a Bayesian network model for early diagnosis of autism. The model was built based on the medical literature and then was revised by two domain experts. Our tool is dedicated to parents that can perform an early diagnosis of their child before visiting a specialist.Sieci bayesowskie są często używanym narzędziem w rozwiązywaniu problemów diagnostycznych. Jedną z zalet tego narzędzia jest mozliwość łączenia wiedzy pochodzącej z różnych źródeł. Na przykład, wiedza ekspertów może być połączona z danymi. W naszym artykule prezentujemy model sieci bayesowskiej wspomagający wczesne diagnozowanie autyzmu. Model został zbudowany w oparciu o literaturę medyczną, a następnie zweryfikowany przez ekspertów. Narzędzie, które stworzyliśmy jest dedykowane rodzicom, którzy mogą dokonać wstępnej diagnozy zanim skontaktują się ze specjalistą

Learning parameters in canonical models using weighted least squares

We propose a novel approach to learning parameters of canonical models from small data sets using a concept employed in regression analysis: weighted least squares method. We assess the performance of our method experimentally and show that it typically outperforms simple methods used in the literature in terms of accuracy of the learned conditional probability distributions