Photoaging of the chest analyzed by capacitance imaging

Capacitance imaging is a new technique using sensors based on silicon technology developed to record fingerprints for security reasons. Applying such a sensor onto the skin surface gives the capacitance (hydration) map of the skin surface with a two-dimensional resolution of 50 microm. This method was used to characterize skin of the chests of 64 women with various grades of skin photoaging.

The severity of photoaging of the chest skin of 64 women was clinically assessed according to a six-grade scale. Capacitance images of the skin were recorded and analyzed in terms of mean capacitance, homogeneity of gray levels and density of microrelief lines. Capacitance images of the adjacent unexposed area (upper part of the breast) were also recorded and analyzed for comparison. Pictures of the different areas were recorded.

Microrelief line density decreases with the age of the volunteers but is independent of the severity of photoaging. Mean hydration of the skin surface is found to be independent of both photoaging severity and age. Evenness of hydration is a parameter markedly linked to the severity of photoaging independent of age. Uneven hydration is related to the juxtaposition of both hydrated and dry areas corresponding to some hyperpigmented and hyperkeratosic areas. Moreover, capacitance images reveal that some of the hyperpigmented areas may exhibit under- or over-hydrated conditions depending on the nature of the lesion.

Irregular skin surface hydration is an important characteristic of skin photoaging. It is related to skin pigmentation but does not parallel its unevenness of pigmentation.