Noninvasive inspection of skin lesions via multispectral imaging

An optical noninvasive inspection tool is presented to, in vivo, better characterize biological tissues such as human skin. The method proposed exploits a multispectral imaging device to acquire a set of images in the visible and NIR range. This kind of information can be very helpful to improve early diagnosis of melanoma, a very aggressive cutaneous neoplasm, incidence and mortality of which continues to rise worldwide. Currently, noninvasive methods (i.e. dermoscopy) have improved melanoma detection, but the definitive diagnosis is still achieved only by invasive method (istopathological observation of the excised lesion). The multispectral system we developed is capable of imaging layers of structures placed at increasing depth, thanks to the fact that light propagates into the skin and reaches different depths depending on its wavelength. This allows to image many features which are less or not visible in the clinical and dermoscopic examination. A new semeiotics is proposed to describe the content of multispectral images. Dermoscopic criteria can be easily applied to describe each image in the set, however inter-images correlations need new suitable descriptors. The first group of new parameters describes how the dermoscopic features, vary across the set of images. More aspects 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.