Design and evaluation of a novel portable erythema-melanin-meter

Background and Objectives: Objective evaluation of the pigmentation index (PI) and the eythema index (EI) of human skin is a prerequisite for successful optimization of laser- and intense-pulsed-light (IPL)-based treatment modalities in dermatology. Study Design/Materials and Methods: We describe a three-wavelength technique for determining PI and EI as well as its particular implementation using LEDs operating at wavelengths of 560,650, and 710 run and a large-area photodiode. The instrument has been evaluated both in vitro and in vivo. Results: In vitro, good correlation between the measured indices and results obtained with commercially available techniques has been observed. In addition, linearity of the PI with melanin concentration in the phantom medium up to 7 x 10(-3) nm(-1) (defined as a slope of the optical density spectrum) has been established. In vivo, feasibility of using the technique for predicting the minimal erythema dose (MED), minimal phototoxic dose (MPD), and the threshold of epidermal damage in a photothermal treatment has been demonstrated. Conclusions: The data suggest that the technique has a substantial potential as a method of pre-treatment diagnostics for photochemical and photothermal procedures. Lasers Surg. (C) 2004 Wiley-Liss, Inc.