Comparison of various fractal analysis methods for retinal images

Abstract

Retinal vessels are known to behave like a fractal, waherein a part of a geometrical pattern resembles the whole. Although the box counting method has been used most commonly, currently there exists no "best method" for fractal analysis on retinal vessels. In the present study we compared the different methods of fractal analysis of retinal images. This study included 43 normal retinal images from public databases (STARE & DRIVE) and 40 retinal images (20 normal and 20 diseased) collected from an epidemiological study database (Sankara Nethralaya diabetic retinopathy epidemiology and molecular genetics study; SNDREAMS). In our study we calculated and compared the values of fractal dimensions by Box counting method, Hausdorff Fractal Dimension (HFD), Modified Hausdorff Fractal Dimension (MHFD) and Fourier Fractal Dimension (FFD). The coefficient of variation(CV) was the least with HFD methods in different databases (DRIVE & STARE: −0.088, SNDREAMS Normal retinal images: −0.117, SNDREAMS Diseased retinal images: −0.103). Our study showed that HFD method was the best method to calculate the fractal dimensions of normal and diseased retinal images.