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Biomedical subjects

M Stefanelli

Publications and source records attributed to M Stefanelli.

At least 19 recordsLinked to original sources
PubMed1995

A case study in ontology library construction.

The goal of our work is to facilitate the development of medical knowledge-based systems by providing a library of reusable ontologies. The availability of such a library reduces the amount of knowledge acquisition required to create knowledge bases of new applications, and makes it easier to connect a knowledge-based system to existing data bases. This article presents a case study in constructing such a library. The emphasis is on studying the principles that underly the internal structure of the library as well as on the process of constructing and using the library. We envision that, in the future, application ontologies can be constructed by the selection and refinement of generic ontologies and domain ontologies from such a library.

Artificial Intelligence↗
PubMed1994

GAMES II Project: a general architecture for medical knowledge-based systems.

GAMES II aims at developing a comprehensive and commercially viable methodology to avoid problems ordinarily occurring in KBS development. GAMES II methodology proposes to design a KBS starting from an epistemological model of medical reasoning (the Select and Test Model). The design is viewed as a process of adding symbol level information to the epistemological model. The architectural framework provided by GAMES II integrates the use of different formalisms and techniques providing a large set of tools. The user can select the most suitable one for representing a piece of knowledge after a careful analysis of its epistemological characteristics. Special attention is devoted to the tools dealing with knowledge acquisition (both manual and automatic). A panel of practicing physicians are assessing the medical value of such a framework and its related tools by using it in a practical application.

Artificial Intelligence↗
PubMed1994

A framework for building and simulating qualitative models of compartmental systems.

This paper describes a framework, called QCMF (Qualitative Compartmental Modeling Framework), which assists the user in formulating models of a pathophysiological system and in analyzing their behaviors through the simulation of the effects of a variety of pathogenetic mechanisms and therapeutical treatments. QCMF has adopted the compartmental theory as modeling ontology: a system is represented as a finite set of interacting compartments. The user enters, through an iconic language and menus, the compartmental structure of a pathophysiological system and the definition of the kinds of functional relationships describing the interactions between compartments. Then, QCMF automatically generates a behavior model of the system. Such a model consists of a set of ordinary differential equations, which are qualitatively expressed, and is directly coded into the language which is interpreted by the simulation algorithm. The system behavior can be obtained by simulating the model starting from an initial state which describes the perturbations acting on the system. The code defining the initial state is automatically built by QCMF as well. Finally, explanations of the predicted behavior are also automatically generated.

Algorithms↗
PubMed1994

[Left valvular involvement in carcinoid: description of a case].

Right-sided valvular heart disease is a common complication of metastatic carcinoid tumors. On the contrary, left valve involvement is a rare finding. In our report we describe a patient in whom the subsequent involvement of right and left heart valves was documented by 2D and Doppler echocardiography. The patient was a 46-year-old woman who, in the last three years, complained of face flushing, postprandial diarrhea and shooting epigastric pain lasting for hours. She came at our observation for increasing dyspnoea, peripheral edemas and asthenia. 2D-echocardiography and Color Doppler revealed a severe tricuspid regurgitation and a turbulent blood flow across the pulmonary valve. An Angiographic examination confirmed the severe tricuspidal regurgitation and disclosed a mild pulmonary stenosis. These findings were associated with high 5 hydroxyndole acetic acid (5-HIAA) urinary excretion and the presence of a liver metastasizing ileal carcinoid tumor. Some months later, a new 2D echo-Doppler examination showed thickening and reduced motion of the posterior mitral leaflet, associated with regurgitation and an aortic insufficiency without evident structural valvular abnormalities. Even if carefully investigated no right-to-left shunt was found.

Angiography↗
PubMed1993

Medical diagnostic reasoning: epistemological modeling as a strategy for design of computer-based consultation programs.

The complexity of cognitive emulation of human diagnostic reasoning is the major challenge in the implementation of computer-based programs for diagnostic advice in medicine. We here present an epistemological model of diagnosis with the ultimate goal of defining a high-level language for cognitive and computational primitives. The diagnostic task proceeds through three different phases: hypotheses generation, hypotheses testing and hypotheses closure. Hypotheses generation has the inferential form of abduction (from findings to hypotheses) constrained under the criterion of plausibility. Hypotheses testing is achieved by a deductive inference (from generated hypotheses to expected findings), followed by an eliminative induction, constrained under the criterion of covering, which matches expected findings against patient's findings to select the best explanation. Hypotheses closure is a deductive-inductive type of inference very similar to the inferences operating in hypotheses testing. In this case induction matches the consequences of the generated hypotheses against the patient's characteristics or preferences under the criterion of utility. By using the language exploited in this epistemological model, it is possible to describe the cognitive tasks underlying the most influential knowledge-based diagnostic systems.

Artificial Intelligence↗
PubMed1993

European research efforts in medical knowledge-based systems.

This article describes the major projects going on in Europe in the field of Artificial Intelligence in Medicine. The important role of the Commission of the European Communities in providing the needed resources is stressed throughout the paper. Particular attention is given to the methodological and technological issues addressed by the European research teams, since the results which these teams accomplish are fundamental for a more extensive diffusion of knowledge-based systems in real medical settings. The variety of medical problems tackled shows that there is no field of medicine where the potential of advanced informatics technologies has not yet been assessed.

Artificial Intelligence↗
PubMed1993

Inferential knowledge acquisition.

This paper describes the approach we are pursuing for modeling inferential processes in knowledge-based systems. It is aimed at overcoming the lack of generality affecting many of the systems described in the literature. This mainly happens since the problem-solving method adopted by those systems is too closely tied to the particular domain problem over which the method itself has been modeled. We also describe a system called M-KAT (Medical Knowledge Acquisition Tool) which is useful in simplifying the process of acquiring inferential knowledge. M-KAT relies on an epistemological model of medical reasoning which represents a generalization of most of the problem-solving methods adopted in medical knowledge-based systems. The metarules formalism has been adopted as a mean for representing inferential knowledge and making its acquisition easier, thus allowing the computational implementation of the epistemological model of medical reasoning.

Artificial Intelligence↗
PubMed1993

Daily rhythmic variations in histamine in human blood.

We examined whether or not normal subjects have rhythmic changes of blood histamine levels. Daily predictable variations are present with 3 maxima and 3 minima and acrophase at 09.13. The significance of these changes is presently unknown.

Adult↗
PubMed1992

A specialized framework for medical diagnostic knowledge-based systems.

For a knowledge-based system (KBS) to exhibit an intelligent behavior, it must be endowed with knowledge enabling it to represent the expert's strategies. The elicitation task is inherently difficult for strategic knowledge, because strategy is often tacit, and, even when it has been made explicit, it is not an easy task to describe it in a form which may be directly translated and implemented into a program. This paper describes a Specialized Framework for Medical Diagnostic Knowledge-Based Systems that can help an expert in the process of building KBSs in a medical domain. The framework is based on an epistemological model of diagnostic reasoning which has proven to be helpful in describing the diagnostic process in terms of the tasks that it is composed of. It allows a straightforward modeling of diagnostic reasoning at the knowledge level by the domain expert, thus helping to convey domain-dependent strategies into the target KBS.

Artificial Intelligence↗
PubMed1991

GAMEES: a probabilistic environment for expert systems.

This paper describes GAMEES (Graphical Modelling Environment for Expert Systems), an interactive graphical environment for building and processing Belief Networks and Influence Diagrams. We review the existing systems designed for analogous purposes, and, after a brief introduction to Belief Networks and Influence Diagrams, we describe the graphical interface, discuss algorithms for probabilistic inference on these networks and illustrate the current implementation of GAMEES. The system has been designed for being integrated within wider expert systems and actually it is part of the Therapy Advisor module within an expert system for the management of anemic patients.

Algorithms↗
PubMed1991

A specialized framework for Medical Diagnostic Knowledge Based Systems.

To have a knowledge based system (KBS) exhibiting an intelligent behavior, it must be endowed even with knowledge able to represent the expert's strategies, other than with domain knowledge. The elicitation task is inherently difficult for strategic knowledge, because strategy is often tacit, and, even when it has been made explicit, it is not an easy task to describe it in a form that may be directly translated and implemented into a program. This paper describes a Specialized Framework for Medical Diagnostic Knowledge Based Systems able to help an expert in the process of building KBSs in a medical domain. The framework is based on an epistemological model of diagnostic reasoning which has proved to be helpful in describing the diagnostic process in terms of the tasks by which it is composed of.

Artificial Intelligence↗
PubMed1990

NEOANEMIA: a knowledge-based system emulating diagnostic reasoning.

Medical diagnosis can be modeled in terms of the classical notions of abduction, deduction, and induction. Abduction is making a preliminary guess that allows one to establish a set of plausible diagnostic hypotheses, followed by deduction for exploring their consequences and induction for testing the hypotheses with available patient data or for planning the acquisition of new data. Such a description of diagnostic reasoning at a knowledge level helps the construction of an expert system by fashioning the adopted expert system building tool to reflect the structure of the problem rather than by fitting the problem to the tool. To this aim, reasoning strategies need to be represented abstractly, separate from medical facts and relations, to make the design more transparent and explainable.

Anemia↗
PubMed1988

A performance evaluation of the expert system ANEMIA.

This paper reports the results of an evaluation study of the current level of performance given by ANEMIA, a knowledge-based consultation system addressing the clinical problem of managing anemic patients. ANEMIA was developed on a mainframe using the AI programming scheme EXPERT and then translated into a version running on a personal computer. At present the system is able to provide assistance in the diagnosis and management of 65 disease entities. After extensive local testing of accuracy, completeness, and consistency of the knowledge base included into ANEMIA, we designed a study to evaluate whether the system is able to appropriately mirror also the reasoning of well-known hematologists other than those who provided the knowledge. We were also interested in testing whether there were conflicting opinions among hematologists. Thus, we designed a validation study in which ANEMIA's performance could be compared with that of six hematologists and the interexpert consensus evaluated. ANEMIA's overall performance was judged acceptable in 87% (26/30) of the cases, while expert evaluators agreed with their colleagues in 90% (27/30) of them. A low interexpert consensus was found: considering the ratings given by different hematologists to the same ANEMIA performance, complete agreement occurred only 47% of the time.

Adult↗
PubMed1986

ANEMIA: an expert consultation system.

Anemia is a knowledge-based consultation program for anemic states. It has been built using an artificial intelligence programming scheme, called EXPERT, which was developed at Rutgers University. At present, ANEMIA is able to provide assistance in the diagnosis and management of 64 disease entities. They include iron deficiency anemias, anemias due to chronic disorders, thalassemias, hemolytic anemias, arigenerative anemias, and a few other miscellaneous conditions. ANEMIA was tested against a data base of 220 retrospective and 100 new cases and the overall accuracy in the diagnostic performance was pretty good. Our intent is that ANEMIA ultimately will be able to serve as surrogate for the hematologist with the nonhematologist physician-user.

Anemia↗
PubMed1985

Classification of anaemia on the basis of ferrokinetic parameters.

Quantitative information on abnormalities of erythropoiesis and mechanisms of anaemia has been obtained in 136 anaemic patients by means of ferrokinetic studies. To derive a functional classification of anaemia based on ferrokinetic parameters, agglomerative hierarchical cluster analysis and principal coordinate analysis were utilized as techniques for unsupervised classification. Two main clusters were found and named anaemia with low potential erythropoiesis and with high potential erythropoiesis, since the most discriminant parameter between them was total erythroid iron turnover, a measure of total erythropoietic activity. A value of total erythropoiesis equal to 4 times the normal was found to discriminate these two types of anaemia in 94% of cases. Within the group with low potential erythropoiesis, three clusters showing different qualitative disturbances of erythropoiesis were singled out. Among patients with high potential erythropoiesis, two clusters were found. A value of effective erythropoiesis equal to 2.5 times the normal was shown to have a high discriminant power between these clusters. This threshold level distinguished between patients having ineffective erythropoiesis or peripheral haemolysis as the major mechanism of anaemia. The present functional classification of anaemia provides a complete picture of the different pathogenetic mechanisms and may represent the basis for a more rational diagnostic approach to erythroid disorders.

Adolescent↗
PubMed1984

Quantitation of reticuloendothelial iron kinetics in humans.

Reticuloendothelial iron kinetics were investigated in a simultaneous dual-isotope study in 10 healthy adult subjects in whom 55Fe-ferric hydroxide phosphate colloid was used to label the reticuloendothelial iron pools, and 59Fe-transferrin was used to define plasma iron kinetics. The simultaneous clearance of 55Fe and 59Fe from plasma and the uptake of each into red blood cells were measured over 14 days. The 55Fe-colloid was cleared almost immediately, and its iron was rapidly released to bind to plasma transferrin. Red cell incorporation of 55Fe was, however, much slower than that of 59Fe bound to transferrin in vitro. The data were analyzed by a new model of reticuloendothelial iron metabolism that contained two reticuloendothelial iron pools; one had a rapid turnover and donated iron to transferrin, and the other, a storage pool, had a slower turnover. The transit pool contained a mean of 164 mumol iron with little variation between subjects, whereas the storage pool was somewhat larger (mean 873 mumol iron) and showed more marked variation between subjects. In general an equal proportion of the iron leaving the transit pool went to transferrin and to the storage pool. The distribution between the two routes did not appear to be related either to plasma iron concentration, latent iron-binding capacity, or transferrin saturation.

Adult↗
PubMed1984

Immunoregulatory T cells in measles. The relationship between reduced lymphocyte proliferative response to PHA and increased proportion of circulating suppressor-cytotoxic T cells.

Viral infections are often associated with immunodeficiency states. Although T lymphocytes have been thought to suppress the host's immune response, the precise cellular basis for this phenomenon remains unclear. Therefore, we characterized peripheral blood mononuclear cells from 9 measles virus-infected children by means of monoclonal antibodies directed against surface antigens expressed on human T lymphocytes and T-cell subsets. In addition, the measles lymphocyte blast transformation response to the T-cell mitogen phytohaemagglutinin (PHA) was evaluated as an index of specific T-cell immunocompetence. During the course of measles, there was a slight reduction in the proportion of total circulating T cells, with a relative decrease in helper-inducer and a parallel increase in suppressor-cytotoxic T lymphocytes. The PHA lymphocyte blastogenic response was found to be defective in children with measles and, interestingly, there was a significant negative correlation between the reduced PHA blast transformation value and the increased proportion of suppressor-cytotoxic cells. The biological implications of these finding with respect to the underlying immunopathology of the measles virus infection are discussed.

Antibodies, Monoclonal↗