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Perception visuelle humaine, complétion des mosaïques et application à la reconstruction d'images de l'endothélium cornéen humain\\ en microscopie optique spéculaire

Abstract : Human corneal endothelium constitutes a monolayer of relatively hexagonal cells with irregular surfaces situated on the internal side of the cornea. These cells are fundamental because they preserve the transparency of the cornea. Their contours can be easily photographed on a patient, using optical specular microscopy (in vivo), or on a graft (ex vivo), using classic optical microscopy. Ophtalmologists then take an interest in cell density as well as in morphometric characteristcs (polymegathism and pleomorphism). However, their analysis using specific sofware is never as relevant as visual analysis. This observation led us to focus on the principles which govern human visual perception. In this thesis we verify in an elementary way that the principles of good continuation and proximity of the Gestalt theory are algorithmically verified on simple cases. This allows us to consider their use to close the contours that are imperfectly detected on images. Nevertheless, the results that are obtained suggest a complex interaction between those principles. The use of morphological methods based on sequential alternate filters, distance maps and watersheds provide good results. It is shown that these methods are based on the principles of Gestalt theory: proximity is introduced by the distance maps, continuation and closing are properties of the watershed operator. Their combined use allows the realization of a dual analysis "contours-régions'': distance maps give access to regional information based on the contours, whereas watersheds provide contour information based on regional markers. These impressions were verified by setting up a dissimilarity criterion which allows us to quantify the differences between a mosaic (cell structure observed on the picture of the endothelium) provided by an expert and another mosaic. Thus, several segmentation methods are tested, and the method we put forward gives the best results. This criterion of dissimilarity allowed us to find the best parameters of each method and to have a ranking established among them by ophtalmologists. In order to complete the segmentation of the images, we put forward a validation based on shape parameters
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https://tel.archives-ouvertes.fr/tel-00473725
Contributor : Andrée-Aimée Toucas <>
Submitted on : Friday, April 16, 2010 - 11:16:42 AM
Last modification on : Friday, October 23, 2020 - 4:33:16 PM
Long-term archiving on: : Monday, October 22, 2012 - 3:05:37 PM

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  • HAL Id : tel-00473725, version 1

Citation

Yann Gavet. Perception visuelle humaine, complétion des mosaïques et application à la reconstruction d'images de l'endothélium cornéen humain\\ en microscopie optique spéculaire. Traitement du signal et de l'image [eess.SP]. Ecole Nationale Supérieure des Mines de Saint-Etienne, 2008. Français. ⟨tel-00473725⟩

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