Boundary detection for skin lesions: an edge focusing algorithm

The accurate location of the boundary of skin lesions is an important first step in the automatic diagnosis of malignant melanoma. The use of standard edge detectors for skin lesion boundary detection has serious shortcomings since those giving sufficiently detailed borders are sensitive to spurious small scale structure elsewhere in the image while those which ignore small scale structure involve low-pass filtering which loses border detail. Edge focusing uses edge detectors of progressively smaller scale, each focusing only in the region of the boundary estimated by the previous detector. This results in a series of boundary position estimates of increasingly finer scale while eliminating spurious edges resulting from noise and other image detail. The selection of the “best fit” boundary is made by comparison of the contrast between narrow regions just inside and outside the boundary or from the variance of image intensity in the latter region