Figure 4.

Examples of misclassification. A, C, The input of the classification of artery and vein network (CAVnet). B, D, The segmentation results produced by CAVnet. The yellow arrows show segmentation errors in the output images. Mis-segmentation may be caused when CAVnet overfits the “artery-vein-alternation rule” or when the capillary-free zone near arteries is unobvious. Artery-vein crossings may also make the algorithm generate misclassifications; however, note that in most places the algorithm correctly interpreted crossing vessels.