A preliminary study on skin phantoms to test spatially resolved-Diffuse Reflectance Spectroscopy as a tool to help diagnose cutaneous melanoma: A non-invasive measurement of Breslow index.
Résumé
Diagnosing malignant melanoma implies to evaluate its thickness also known as Breslow Index. Currently, Breslow Index is measured by the anatomopathologist after the visible tumour has been biopsied. Non-invasive measurement of Breslow Index using optical methods would turn the overall procedure into a one-step process thus reducing morbidity, cost and system burden. In the current study spatially-resolved Diffuse Reflectance (DR) Spectroscopy (using five Collection to Excitation Separations - CEFS) was evaluated as a tool to discriminate several Breslow Index simulated by phantoms. Those phantoms were made of two layers: the bottom and the top layers were made so as to simulate respectively dermis and melanoma optical coefficients optical coefficients. Dermis was considered as being mainly scattering (intralipids mixed with gelatin) and melanoma was considered as being both scattering and absorbing because of melanin (intralipids and coffee mixed within gelatin). Bottom layer's thickness was constant (6.3 mm) and top layers were either 2, 3, 4, 5 or 6 mm-thick. Our results show that absolute values of DR signal allow discrimination (p<0.05) of 1 mm-thickness variation of layers simulating Breslow Index at each CEFS : 271, 536, 834 or 1076 µm. However absolute values might be very sensitive to inter-individual variations so we tried to elaborate a relative way of analyzing data and found out that signal intensity decreases linearly with CEFS (R²>0.92). Slopes of the decreasing signal allow discrimination (p<0.05) and that might be more robust to inter-individual variations of melanomas' absorption coefficients. A clinical trial needs to be carried out in order to confirm such an hypothesis.