Early diagnosis of malignant melanoma without invasive excision and histology is one of the main challenges of modern dermatology. Evaluation of risk is often left to the experience and sensibility of the physician/dermatologist and to empirical evaluation of suspect skin lesions made by eye or with simple epi-illumination dermoscopes. Moreover, danger associated to malignant melanoma is strongly affected by the penetration of cancerous cells in the depth of the skin, hence only after histology complete disrmination between malignant and non-malignant lesions is achieved.
Principle of operation
Our dermoscope is based on the illumination provided by three different types of LED in the red, green and blue part of the visible spectrum. They illuminate the region under examination with 45° angle of incidence with linealry polarized light. Image acquisition is performed using a camera and a linear polarizer whose principal axis can be automatically rotated in two position: parallel and perpendicular to incident light polarization. When perpendicular, light reflected just from the surface of the skin and lesion is highly rejected, since it preserves input polarization, while photons scattered in depth in the tissue can reach the camera giving info about the deeper structures. Different LEDs can be switched on and off independently, taking advantage of the spectral properties of the different layers of the skin to get the greater amount of information.
White light, red, green and blue, parallel and perpendicular images are automatically acquired in a few seconds and can then be elaborated with dedicated software to highlight the different features in, under and around the lesion.
D. Kapsokalyvas, N. Bruscino, D. Alfieri, V. de Giorgi, G. Cannarozzo,T. Lotti, F.S. Pavone, Imaging of human skin lesions with the multispectral dermoscope, Photonic Therapeutics and Diagnostics VI. Edited by Kollias, Nikiforos; Choi, Bernard; Zeng, Haishan; Malek, Reza S.; Wong, Brian J.; Ilgner, Justus F. R.; Gregory, Kenton W.; Tearney, Guillermo J.; Marcu, Laura; Hirschberg, Henry; Madsen, Steen J.; Mandelis, Andreas; Mahadevan-Jansen, Anita; Jansen, E. Duco. Proceedings of the SPIE, Volume 7548, pp. 754808-754808-8 (2010).