Is the Minimal Erythema Dose Achievable at Optical Spectroscopy of Skin in Vivo?

Since UV radiation is capable to cause skin erythema, there is a damage risk at in-vivo UV spectroscopy of skin. An optical fiber delivery of UV radiation to the skin is potentially dangerous because of its small aperture, and, consequently, the high output power density of radiation. In this paper, to investigate this issue, an analysis of the distribution of energy absorbed in skin was conducted using Monte Carlo simulations of light transport. On the example of two types of light sources - an optical fiber and an extended large-area source, which usually applied at UV phototherapy, it was shown that the approach calculating the UV radiation dose as a radiant exposure is not quite correct for the optical-fiber illumination.