Development of optical tissue phantoms for the evaluation of the thickness of pigmented skin lesions by a conveniently purpose-modified digital camera: numerical simulations and experimental measures.

The development of an optical skin-tissue phantom can be useful in accelerating and optimizing the diagnosis of suspected lesions of the skin tissue. In fact, benign melanocytic lesions are different, in terms of diffuse reflectance, from that of melanoma. Diffuse reflectance of skin pigmented lesions depends on the amount and distribution of the absorbing/diffusing cromophores, mainly haemoglobin and melanin, embedded in the skin layers. In an attempt to correlate the thickness to the dangerousness of the lesion, phantoms able to simulate the diffuse reflectance of some lesions with different thickness have been developed and used to validate an inhouse developed survey instrument potentially useful to the dermatologist to evaluate the dangerousness of a pigmented skin tissue lesion. The basic material for lesions and skin-like phantoms is a poly(vinyl alcohol) - PVA transparent hydrogel in which appropriate amounts of optical scatterers have been added extraneously at the time of formation, to achieve the tunability of optical properties. Liquid India ink has been used to simulate the melanin and all the other cromophores. Slabs were prepared to mimic lesions with different thicknesses. The optical properties of tissue phantoms have been determined in the visible and near-infrared spectral range by using a conveniently purpose-modified digital camera.