Artículos

Segmentation of Blood Vessels Based on a Threshold that Combines Statistical and Scale Space Filters

Segmentación de Vasos Sanguíneos Basada en un Umbral que Combina Filtros Espaciales Estadísticos

Roberto Rodríguez

Institute of Cybernetics, Mathematics and Physics (ICIMAF)
Digital Signal Processing Group
Calle 15 no. 551 e/ C y D, CP 10 400, Ciudad de la Habana, CUBA

E-mail: rrm@iicmf.inf.cu

Article received on October 25, 2004; accepted on July 07, 2005

Abstract

This paper presents a strategy for segmenting blood vessels based on the threshold, which–combines statistic and scale space filter. By incorporating statistical information, the strategy is capable of reducing over–segmentation. We propose a three stage strategy which involves: (1) optimal selection of window size; (2) optimal selection of scale and (3) segmentation process. We compared our strategy to two commonly used thresholding techniques. Experimental results showed that our method is much more robust and accurate. Our strategy suggested a modification to Otsu's method. In this application the important information to be extracted from images is only the number of blood vessels present in the images. The proposed strategy was tested on manual segmentation, where segmentation errors less than 3% for false positives and 0% for false negatives are observed. The work presented in this paper is a part of a global image analysis process. Therefore, these images will be subject to a further morphometrical analysis in order to diagnose and predict automatically malign tumors.

Keywords: Thresholding method, Scale–space filter, Image segmentation, Angiogenesis process.

Resumen

Este artículo presenta una estrategia para la segmentación de vasos sanguíneos basada en el umbral, la cual combina estadística y filtro de espacio escala. Al incorporar información estadística la estrategia es capaz de reducir la sobre segmentación. Nosotros proponemos una estrategia consistente de tres estados, la cual involucra: (1) selección óptima del tamaño de ventana; (2) óptima selección de la escala y (3) el proceso de segmentación. Nuestra estrategia es comparada con dos técnicas comúnmente muy usadas las cuales hacen uso del umbral. Los resultados experimentales mostraron que nuestro método es mucho más robusto y exacto. Nuestra estrategia sugirió una modificación al método de Otsu. En esta aplicación la información importante a extraer de las imágenes es solamente el número de vasos sanguíneos presentes en ellas. Los resultados de la estrategia propuesta fueron comparados con aquellos obtenidos a través de la segmentación manual, donde el error de segmentación para los falsos positivos fue menor que el 3% y para los falsos negativos fue del 0%. El trabajo presentado en este artículo es parte de un proceso global de análisis de imágenes. Por tanto, estas imágenes serán sujetas a un adicional análisis morfométrico para diagnósticar y pronósticar automáticamente tumores malignos.

Palabras Clave: Método a través del umbral, Filtro espacio escala, Segmentación de imágenes, Proceso de angiogénesis.

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Acknowledgements

The authors would like to thank Dr. Roberto Wong from "Dr. Carlos J. Finlay" hospital, Cuba, for facilitating the test images and accepting this project.

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