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Biomedical subjects

T Timmers

Publications and source records attributed to T Timmers.

7 recordsLinked to original sources

A framework for uniform access to data, software and knowledge.

An object-oriented framework is presented that offers integration of various types of entities at one workstation. Five types of entities are distinguished: data, knowledge, functions, presentation forms and hardware, and for each of these entities an 'accessor' is introduced. An accessor offers abstraction from the particularities of access to the entities. For the interaction with this framework a programming language has been defined. A restricted form of the framework has been used to implement a prototype medical workstation for the support of clinical data analysis.

Artificial Intelligence

Integration of an object knowledge base into a medical workstation.

A simple, yet powerful, knowledge base and its development environment is described that can act as a "knowledge server", integrated into a medical workstation. In many areas, such an integration of a knowledge base with other modules and systems is required, but difficult or impossible to achieve with existing commercial development shells. Three applications of the knowledge base are described: a controlled vocabulary for the classification of Congenital Heart Diseases, an extended data model for cardiology, and management of syntax descriptions for the BMDP command language.

Artificial Intelligence

Neutrophil granulation stained with May Grunwald Giemsa or pure Azure B-eosin Y quantified by image analysis.

Neutrophil granulation was quantified after staining with May Grunwald Giemsa or with the pure dyes Azure B and eosin Y. Spinner slides of the buffy coat of 3 normal subjects and 14 persons with different grades of toxic granulation were studied. Morphometric parameters were measured using an image analysis computer (Texture Analysis System, Leitz Wetzlar, FRG). The parameters for granulation varied over a wider range in Azure B (AzB) than in May Grunwald Giemsa (MGG) stained granulocytes. This is in accordance with the visual microscopy observation, that granulation is more pronounced after staining with AzB than MGG. The predominant shade of the nucleus was similar in both stains, whereas considerable and variable differences in the shade of the cytoplasm were found.

Azure Stains

Relation of quantitative features of visually normal intermediate cells in cervical intraepithelial neoplasia I and II smears to progression or nonprogression of the lesion.

The relationship between the quantitative features extracted from digitized images of visually normal intermediate cells in cervical intraepithelial neoplasia (CIN) I and II smears and the subsequent follow-up diagnosis was studied. Using the ISPAHAN interactive system of pattern recognition, the average rate of correct classification of progressive or nonprogressive lesions was 80% at the specimen level. It is concluded that additional diagnostic information regarding the probability of progression of CIN I and II lesions may be obtained by studying the microphotometric features of visually normal intermediate cells in the cervical smears. Significant differences were found between intermediate cells close to obviously dysplastic cells and those at a distance. The implication of this finding and the problems involved in the selection of the cells are briefly discussed.

Female

A model for the classification of specimens containing random proportions of abnormal cells.

The effect of abnormal cell proportion on the performance of an automated cervical prescreening system is discussed in K.R. Castleman and B.S. White, Cytometry 2:155-18. The model employed assumes fixed proportions of abnormal cells, both in the design stage and in the test stage. In the present paper, an extended model is developed that allows for random variability of this proportion. It is shown, that there is a fundamental, non-zero lower limit to the false-negative specimen error rate, which depends only on the coefficient of variation. This limit may be reached even for moderate values of the coefficient of variation, which implies that a satisfactory prescreening system may not be feasible.

Cytological Techniques

The use of correspondence analysis in the assessment of morphologic changes during carcinogenesis.

Correspondence analysis is a statistical technique originally developed for the analysis of frequency and contingency tables. It may also be successfully applied to the problem of the assessment of the characteristics of samples of cytological material. The present article describes the use of this formalism on feature data measured on urothelial cells in populations obtained from rats at different time points after exposition to a carcinogenic agent. After the application of correspondence analysis, the projections of the samples corresponding to the different time points onto the plane spanned by the first two factorial axes constitute a trajectory, preserving the time ordering. The locations of the projections of cell samples of untreated animals (controls) with respect to this trajectory suggest that two different processes inducing different morphological changes are at work: Early abnormal samples are characterized by a lower-than-normal value of nuclear stain content, whereas late abnormals are mainly characterized by a higher-than-normal nuclear stain value. It is shown that populations of selected atypical cells show less variation throughout the carcinogenic process than populations of randomly selected cells.

Animals

Classification of immature and mature cells of the neutrophil series using morphometrical parameters.

Quantitative morphological data of six classes of immature and mature cells of the neutrophil series of the bone marrow of normal persons were used for statistical classification experiments (myeloblasts, promyelocytes, myelocytes, metamyelocytes, bands and segments). On each cell, parameters were measured directly from the image or calculated from the shape of the density histogram or the counting densitogram using a Texture Analysis System (E. Leitz, Wetzlar, Germany). The parameters were analyzed with the interactive statistical pattern recognition system ISPAHAN. One half of the data were used as a learning set and the other half as the test set. The parameters were compared according to their performance in discrimination between the classes, alone and in combinations. Parameters not contributing to an improvement of the discrimination were disregarded. Eleven parameters were selected and used for classification by two different methods: a stepwise and a "one-shot" method. Stepwise classification resulted in a 79% correct classification rate. Most errors occurred between cell classes in neighboring stages of maturation. In 96% of all cases the computer classification was either in accordance with that of the technician or with a cell class of a neighboring maturation stage. One step classification by the computer was in agreement with the technicians in 82% of the cases. For 98% of the cells the computer classification was either in accordance with that of the technician or with a cell class of a neighboring maturation stage. The data set was collected by two technicians, operating independently. Differences in their interpretation of the maturation stage were found by comparing the performance of classifiers based on both cell samples. Since the images of the cells were not available for reexamination, the causes of disagreement in classification between the technicians and between computer and technicians could not be evaluated.

Biometry