Identification of skin phototypes through in vivo photoacoustic measurements

Abstract

The aim of the present work was to classify and identify skin phototypes through in vivo photoacoustic (PA) measurements. Fifty-seven female volunteers took part in the study, being clinically evaluated and classified according to skin phototype (Fitzpatrick classification). After cleaning the skin area to be measured, the PA signal level was obtained for the inner and outer faces of both forearms. Volunteers were then classified according to the respective PA signal amplitude; subsequently, this classification was compared to the phototype classification and to the recently proposed Baumann classification. Comparison between the PA signal of the inner and outer faces of the forearm shows a highly significant statistical difference (p < 0.005), attributed to the higher pigmentation level of the skin region continuously exposed to solar radiation, demonstrating that skin constitution and aspect are influenced by the level of sun exposure. Comparison among phototypes was performed separately for the inner and outer faces of the forearm. The results show that the PA signal level (amplitude) for the inner forearm tends to scale with skin phototype, also allowing the division of the volunteers in two groups, according to their pigmentation levels and also following the recent Baumann classification. In this way, the photoacoustic methodology presented allows an objective, numerical classification of the skin types.Keywords Skin, In vivo research, Photoacoustic technique, Phototype, Skin pigmentation. Identificação dos fototipos de pele através de medidas fotoacústicas in vivo