Quantification of erythema and pigmentation using a videomicroscope and a computer

Abstract

We report a method for quantitative analysis of erythema and pigmentation using a videomicroscope interfaced with a computer. The analysis was carried out by examining the brightness intensity of every picture element, composed of an image picked up from each band of red, green, and blue, and by deriving the quasi-absorbance value (absorbance index) from the mean brightness for each band. In assessments of UV-induced erythema and tanning, excellent linear correlations were found between the results obtained with our system and those with a narrow-band reflectance spectrometer. Moreover, the absorbance indices of haemoglobin and melanin solutions showed linear relationships with their concentrations in in vitro examination. As the monitored picture becomes out of focus if incorrect pressure is exerted on the skin, and as regions of interest can be chosen from a magnified image, this system offers excellent interobserver reproducibility, and is suitable for the evaluation of erythema or pigmented lesions which are too small or irregular to quantify by conventional methods such as colorimetry.