Multispectral imaging for early diagnosis of melanoma

Melanoma is a very aggressive cutaneous neoplasm, incidence and mortality of which continues to rise worldwide. Identification of initial melanoma may be difficult because it may be clinically, and sometimes also dermoscopically, indistinguishable from benign lesions. Currently definitive diagnosis is made only by histopathological observation of the excised lesion. Several tools have been developed to help detecting malignant lesions. Dermoscopy highlights numerous characteristic features of the lesion and of the pigmented network. The method we propose exploits a multispectral imaging device to acquire a set of images in the visible and NIR range Thanks to the fact that light propagates into the skin and reaches different depths depending on its wavelength, such a system is capable of imaging layers of structures placed at increasing depths. Therefore a new semeiotics is proposed to describe the content of such images. Dermoscopic criteria can be easily applied to describe each image in the set, however inter-images correlation needs new suitable descriptors. The first group of new parameters describes how the dermoscopic ones, vary across the set of images. More features are then introduced. E.g. the longest wavelength where structures can be detected gives an estimate of the maximum depth reached by the pigmented lesion. While the presence of a bright-to-dark transition between the wavebands in the violet to blue range, reveals the presence of blue-whitish veil, which is a further malignancy marker.