28 February 2013 Determination of the optical properties of melanin-pigmented human skin equivalents using terahertz time-domain spectroscopy
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Abstract
Terahertz time-domain spectroscopy (THz-TDS) methods have been utilized in previous studies in order to characterize the optical properties of skin and its primary constituents (i.e., water, collagen, and keratin). However, similar experiments have not yet been performed to investigate whether melanocytes and the melanin pigment that they synthesize contribute to skin’s optical properties. In this study, we used THz-TDS methods operating in transmission geometry to measure the optical properties of in vitro human skin equivalents with or without normal human melanocytes. Skin equivalents were cultured for three weeks to promote gradual melanogenesis, and THz time domain data were collected at various time intervals. Frequency-domain analysis techniques were performed to determine the index of refraction (n) and absorption coefficient (μa) for each skin sample over the frequency range of 0.1-2.0 THz. We found that for all samples as frequency increased, n decreased exponentially and the μa increased linearly. Additionally, we observed that skin samples with higher levels of melanin exhibited greater n and μa values than the non-pigmented samples. Our results indicate that melanocytes and the degree of melanin pigmentation contribute in an appreciable manner to the skin’s optical properties. Future studies will be performed to examine whether these contributions are observed in human skin in vivo.
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Dawn Lipscomb, Ibtissam Echchgadda, Xomalin G. Peralta, Gerald J. Wilmink, "Determination of the optical properties of melanin-pigmented human skin equivalents using terahertz time-domain spectroscopy", Proc. SPIE 8585, Terahertz and Ultrashort Electromagnetic Pulses for Biomedical Applications, 85850F (28 February 2013); doi: 10.1117/12.2005170; https://doi.org/10.1117/12.2005170
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