Measurement of the Epidermal Thickness with Fourier Domain Optical Coherence Tomography in an Occupational Health Study on Natural Sun Protection of the Human Skin.

Fourier domain optical coherence tomography (FD-OCT) was used to take cross-sectional images of the skin at the forehead, back of hand and back of volunteers. The aim of the occupational health study was the investigation of the natural sun protection of outdoor workers and in particular the quantification of the UV induced epidermal thickening. A set of manually segmented OCT images was used as a gold standard to evaluate the performance of automatic algorithms for finding the epidermal thickness. The established A-scan averaging method and two newly developed automatic algorithms were compared. The first of the new methods is based on Markov random chains and the second new and best performing algorithm is based on a convolution filter with a trace finding routine with a quadratic cost function. Although the results of all algorithms differ in the absolute values for the epidermal thickness, they all show the same tendencies. There is a strong dependency of epidermal thickness on skin site, a weak dependency on the season of the year and a noticeable epidermal thickening 7 days of recovery after UV induced erythema. [ABSTRACT FROM AUTHOR]