Models of incremental concept formation

Given a set of observations, humans acquire concepts that organize those observations and use them in classifying future experiences. This type of concept formation can occur in the absence of a tutor and it can take place despite irrelevant and incomplete information. A reasonable model of such human concept learning should be both incremental and capable of handling this type of complex experiences that people encounter in the real world. In this paper, we review three previous models of incremental concept formation and then present CLASSIT, a model that extends these earlier systems. All of the models integrate the process of recognition and learning, and all can be viewed as carrying out search through the space of possible concept hierarchies. In an attempt to show that CLASSIT is a robust concept formation system, we also present some empirical studies of its behavior under a variety of conditions

Methods for Analysing Endothelial Cell Shape and Behaviour in Relation to the Focal Nature of Atherosclerosis

The aim of this thesis is to develop automated methods for the analysis of the spatial patterns, and the functional behaviour of endothelial cells, viewed under microscopy, with applications to the understanding of atherosclerosis. Initially, a radial search approach to segmentation was attempted in order to trace the cell and nuclei boundaries using a maximum likelihood algorithm; it was found inadequate to detect the weak cell boundaries present in the available data. A parametric cell shape model was then introduced to fit an equivalent ellipse to the cell boundary by matching phase-invariant orientation fields of the image and a candidate cell shape. This approach succeeded on good quality images, but failed on images with weak cell boundaries. Finally, a support vector machines based method, relying on a rich set of visual features, and a small but high quality training dataset, was found to work well on large numbers of cells even in the presence of strong intensity variations and imaging noise. Using the segmentation results, several standard shear-stress dependent parameters of cell morphology were studied, and evidence for similar behaviour in some cell shape parameters was obtained in in-vivo cells and their nuclei. Nuclear and cell orientations around immature and mature aortas were broadly similar, suggesting that the pattern of flow direction near the wall stayed approximately constant with age. The relation was less strong for the cell and nuclear length-to-width ratios. Two novel shape analysis approaches were attempted to find other properties of cell shape which could be used to annotate or characterise patterns, since a wide variability in cell and nuclear shapes was observed which did not appear to fit the standard parameterisations. Although no firm conclusions can yet be drawn, the work lays the foundation for future studies of cell morphology. To draw inferences about patterns in the functional response of cells to flow, which may play a role in the progression of disease, single-cell analysis was performed using calcium sensitive florescence probes. Calcium transient rates were found to change with flow, but more importantly, local patterns of synchronisation in multi-cellular groups were discernable and appear to change with flow. The patterns suggest a new functional mechanism in flow-mediation of cell-cell calcium signalling

Cuantificación de glándulas en imágenes histopatológicas de cáncer gástrico

Automatic detection and quantification of glands in gastric cancer may contribute to objectively measure the lesion severity, to develop strategies for early diagnosis, and most importantly to improve the patient categorization; however, gland quantification is a highly subjective task, prone to error due to the high biopsy traffic and the experience of each expert. The present master’s dissertation is composed by three chapters that carry to an objective identification of glands. In the first chapter of this document we present a new approach for segmentation of glandular nuclei based on nuclear local and contextual (neighborhood) information “NLCI”. A Gradient-BoostedRegression-Tree classifier is trained to distinguish between glandular nuclei and non glandular nuclei. Validation was carried out using 45.702 annotated nuclei from 90 fields of view (patches) extracted from whole slide images of patients diagnosed with gastric cancer. NLCI achieved an accuracy of 0.977 and an F-measure of 0.955, while R-CNN yielded corresponding accuracy and F-measures of 0.923 and 0.719, respectively. In second chapter we presents an entire framework for automatic detection of glands in gastric cancer images. By selecting gland candidates from a binarized version of the hematoxylin channel. Next, the gland’s shape and nuclei are characterized using local features which feed a Random-Cross-validation method classifier trained previously with images manually annotated by an expert. Validation was carried out using a data-set with 1.330 from seven fields of view extracted from patients diagnosed with gastric cancer whole slide images. Results showed an accuracy of 93 % using a linear classifier. Finally, in the third chapter analyzing gland and their glandular nuclei most relevant features, since predict if a patient will survive more than a year after being diagnosed with gastric cancer. A feature selection based on mutual information: criteria of max-dependency, max-relevance, and min-redundancy “mRMR” approach selects those features that correlated better with patient survival. A data set with 668 Fields of View (FoV), 2.076 glandular structures from 14 whole slide images were extracted from patient diagnosed with gastric cancer. Results showed an accuracy of 78.57 % using a QDA Linear & Quadratic Discriminant Analysis was training with Leave-one-out e.g training with thirteen cases and leaving a separate case to validate.La detección y cuantificación automática de las glándulas en el cáncer gástrico puede contribuir a medir objetivamente la gravedad de la lesión, desarrollar estrategias para el diagnóstico precoz y lo que es más importante, mejorar la categorización del paciente; sin embargo, su cuantificación es una tarea altamente subjetiva, propensa a errores debido al alto tráfico de biopsias y a la experiencia de cada experto. La presente disertación de maestría está compuesta por tres capítulos los cuales llevan a la cuantificación objetiva de glándulas. En el primer capítulo del documento se presenta un nuevo enfoque para la segmentación de los núcleos glandulares en base a la información nuclear local y contextual (vecindario). Se entrenó un Gradient-Boosted-Regression-Tree para distinguir entre núcleos glandulares y núcleos no glandulares. La validación se llevó con 45.702 núcleos anotados manualmente de 90 campos de visión (parches) extraídos de imágenes de biopsias completas de pacientes diagnosticados con cáncer gástrico. NLCI logró una precisión de 0.977% y un F-Score de 0.955%, mientras que fast R-CNN arrojó una precisión de 0.923% y un F-Score y 0.719%. En el segundo capítulo se presenta un marco completo para detección automática de glándulas en imágenes de cáncer gástrico. Las glándulas candidatas se seleccionan de una versión binarizada del canal de hematoxilina. A continuación, la forma y los núcleos de las glándulas se caracterizan y se alimenta un clasificador Random Cross Validation, entrenado previamente con imágenes anotadas manualmente por un experto. La validación se realizó en un conjunto de datos con 1.330 parches extraídos de siete biopsias de pacientes diagnosticados con cáncer gástrico. Los resultados mostraron una precisión del 93% utilizando un clasificador lineal. Finalmente, el tercer capítulo analiza las características más relevantes de las glándulas y sus núcleos glandulares, para predecir la sobrevida a un año de un paciente diagnosticado con cáncer gástrico. Una selección de características basada en información mutua: criterios de dependencia máxima, máxima relevancia y mínima redundancia (mRMR) escogen las características correlacionadas con la supervivencia del paciente. Se extrajo un conjunto de datos con 668 campos de visión (FoV), 2.076 estructuras glandulares de 14 imágenes completas de pacientes diagnosticados con cáncer gástrico. Los resultados mostraron una precisión del 76.3% usando un Análisis Discriminante Lineal y Cuadrático (QDA) y un esquema de evaluación entrenando con trece casos y dejando un caso aparte para validar.Magíster en Ingeniería Biomédica. Línea de investigación: Procesamiento de señale

Establishing Relevant ADC-based Texture Analysis Metrics for Quantifying Early Treatment-Induced Changes in Head and Neck Squamous Cell Carcinomas

Purpose: The purpose of this study is to identify which texture analysis metrics calculated from apparent diffusion coefficient (ADC) maps from patients with head and neck squamous cell carcinomas (HNSCC) provide quantifiable measures of tumor physiology changes. We discerned which imaging metrics were relevant using baseline agreement and variations during early treatment. Methods: For selective patients with stages II-IV HNSCC, ADC maps were generated from two baselines, taken 1 week apart, and one early treatment scan, obtained during the 2nd week of curative-intent chemoradiation therapy. Regions of interest (ROI), consisting of primary and nodal disease were drawn onto resampled ADC maps. Four 3D texture matrices describing local and regional relationships between voxel intensities in the ROIs were generated. From these, 38 texture metrics and 7 histogram features were calculated for each patient, including the mean and median ADC. Agreement between the two baseline measures was estimated with the intra-class correlation coefficient (ICC). For each metric with an ICC≥0.80, the Wilcoxon signed-rank test was used to test if the difference between the mean of the baselines and the early treatment was non-zero. Results: Texture analysis was implemented on nine patients that had both baselines and early treatment images. Due to baseline agreement, only 9 of the 45 metrics had an ICC ≥0.80, including ADC mean and median. Six of these 9 metrics had a p-value \u3c 0.05. Only 1 of the 9 metrics remained of interest, after applying the Holm correction to the alpha levels: the run length non-uniformity metric (p = 0.004) in the Gray Level Run Length Matrix. Conclusion: The feasibility of texture analysis is dependent on the baseline agreement of each metric, which disqualifies many texture characteristics. However, metrics with high ICC have potential to provide additional quantitative information for the assessment of early treatment changes for HNSCC

Evolutionary 3D Image Segmentation of Curve Epithelial Tissues of Drosophila melanogaster

Analysing biological images coming from the microscope is challenging; not only is it complex to acquire the images, but also the three-dimensional shapes found on them. Thus, using automatic approaches that could learn and embrace that variance would be highly interesting for the field. Here, we use an evolutionary algorithm to obtain the 3D cell shape of curve epithelial tissues. Our approach is based on the application of a 3D segmentation algorithm called LimeSeg, which is a segmentation software that uses a particle-based active contour method. This program needs the fine tuning of some hyperparameters that could present a long number of combinations, with the selection of the best parametrisation being highly time-consuming. Our evolutionary algorithm automatically selects the best possible parametrisation with which it can perform an accurate and non-supervised segmentation of 3D curved epithelial tissues. This way, we combine the segmentation potential of LimeSeg and optimise the parameters selection by adding automatisation. This methodology has been applied to three datasets of confocal images from Drosophila melanogaster, where a good convergence has been observed in the evaluation of the solutions. Our experimental results confirm the proper performing of the algorithm, whose segmented images have been compared to those manually obtained for the same tissues.Ministerio de Ciencia, Innovación y Universidades TIN2017-88209-C2Junta de Andalucía US-1263341Junta de Andalucía P18-RT-2778Ministerio de Economía, Industria y Competitividad BFU2016-74975-PMinisterio de Ciencia e Innovación PID2019-103900GB-10