Revista de Informática Biomédica, v. 5, n. 1 (2015)

Tamanho da fonte:  Menor  Médio  Maior

Two-dimensional sample entropy analysis of rat sural nerve aging

Antonio Carlos da Silva Senra Filho, Luiz Eduardo Virgilio da Silva, Valéria Paula Sassoli Fazan, Joaquim Cezar Felipe, Luiz Otavio Murta Junior


Entropy analysis of images are usually performed using Shannon entropy, which calculates the probability of occurrency of each gray level on the image. However, not only the pixel gray level but also the spatial distribution of pixels might be important for image analysis. On the other hand, sample entropy (SampEn) is an important tool forestimation of irregularity in time series, which calculates the probability of pattern occurrence within the series. Therefore, we propose here an extension of SampEn to a two-dimensional case, namely SampEn 2D , as an entropy method for extracting features from images that accounts for the spatial distribution of pixels. SampEn 2D was applied to histological segments of sural nerve obtained from young (30 days) and elderly (720 days) rats. Morphometric indexes, such as the total number of myelinated fibers and the average myelinated fibers area and perimeter were also calculated. Results show that SampEn 2D can extract useful information from histological nerve images, classifying elderly rat image as more regular than young rat. As SampEn 2D is related to irregularity/unpredictability, we can conclude that the proposed method is complementary to morphometric indexes. Further studies are being built to validate SampEn 2D .


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