How blurry is that border? An investigation into algorithmic reproduction of skin lesion border cut-off

This paper describes an approach to algorithmically measuring the second of the ABCD criteria [Stolz W, Braun-Falco O, Bilek P, Landthaler M, Cognetta AB. Color atlas of dermatoscopy. Oxford: Blackwell Science Ltd, 1994], border cut-off. The method measures the lightness gradient of the lesion at the boundary. Gradients are assigned to "blurry" or "sharp cut-off" on the basis of a threshold obtained by comparing dermatologists' opinions with the algorithm. The algorithm appears to correlate quite well with dermatologists' opinions, although several concerns are apparent, especially the distribution of the image set. This algorithm presents a first step at measuring border cut-off and eventually, reproducing the ABCD criteria [Stolz W, Braun-Falco O, Bilek P, Landthaler M, Cognetta AB. Color atlas of dermatoscopy. Oxford: Blackwell Science Ltd, 1994].