29th Annual Meeting of the American Society of Photobiology

Downtown Marriot

Chicago, Il.

Laser spectroscopic methods for predicting UV sensitivity of human skin in vivo

Abstract-
Lasers are ideal instruments for investigating interactions between UV radiation and human skin in vivo because of their high spectral, spatial and time resolution. Therefore, UV radiation effects on human skin, the basic mechanisms of photoinduced processes and the optical properties of the skin can be determined with high accuracy. A short overview about lasers which can be tuned over various wavelengths and their potentialities concerning burning, tanning and typing will be presented. The wavelength dependencies of the erythema and pigmentation reactions - determined with highly monochromatic laser radiation combined with the standardized (CIE norm system) instrumental determination of the skin color - will be reported. Also the minimum doses at different wavelengths in the UVA and UVB region which induces erythema and pigmentation in the four Fitzpatrick skin types will be discussed in regard to the prediction of UV sensitivity. The individual grade of tanning of all four skin types before the irradiation with UVB or UVA or a combination of both is also very important - as our results show. Time courses of skin reactions after UV exposure may also give valuable information about skin typing. Strongly dynamic color changes within the first minutes after UV irradiation with various wavelengths will be demonstrated. Another new approach for measuring the optical properties of human skin in the UV range in vivo is the optoacoustic tissue differentiation with lasers. This technique allows the determination of wavelength dependent absorption coefficients with high spatial resolution. With the absorption coefficients, an absorption profile can be obtained which improves the determination of penetration depths of UV radiation into the skin. Based on our first results, the possibilities of this method concerning the prediction of UV sensitivity of various skin types in vivo will be discussed with future prospects of how this could lead to a determination method aided by instrumental measurements.

Keywords: Laser Spectroscopy, Action Spectroscopy, Optoacoustic Tissue Differentiation, UV Effects