
213Arteriovenous Ratio Calculation Using Image-Processing Techniques
First, all of the bifurcations and crossings between vessels are detected. To this end,
several algorithms have been proposed in the literature. Some approaches [29,30] use clas-
siers to detect these specic structures. Other approaches are based on analyzing the
topological properties of both the bifurcations and the crossings [31,32]. The rst step in
this kind of algorithm is the segmentation of the vessel tree. Afterward, a thinning pro-
cedure is performed in order to obtain the skeleton of the vessels. Then, the 1 pixel-wide
segments are joined in order to obtain the who ...