| Summary: | 碩士 === 國立臺灣大學 === 光電工程學研究所 === 105 === The chronic damage of skin caused by cumulated exposure to ultraviolet radiation has brought great concern. To study the changes in skin dynamics, in vivo harmonic generation biopsy (HGB) was proposed as a potent imaging tool. HGB provides submicron resolution crucial for histopathological examination and leaves little optical damage in biotissues. With the use of HGB, this thesis is aimed at seeking out novel characteristics in solar lentigines, a type of sun-induced hyperpigmentation, both in their developing progress and after laser depigmenting treatments. Seventeen female Asian volunteers aged from 41 to 77 years old with solar lentigines on the face were involved in the study. Six parameters in HGB images concerning melanin contents or skin structure in lentigines were quantified. It is shown that in solar lentigines 2D longitudinal cellular size, the thickness of stratum corneum (SC), and melanin mass density in cytoplasm of basal cells near dermoepidermal junction (MMDDEJ) are increased. The finding of increase of MMDDEJ in vivo is unprecedented. MMDDEJ was believed to be more objectively comparable than the quantification of melanin proposed by previous studies. The significant decreases in 2D en face viewed melanin-rich cell density and thickness of SC after laser treatment were discovered. It was shown that the decreases in MMDDEJ and 2D melanin-rich cell density seem to have a positive correlation with the whitening of appearances on skin. It may be inferred that the main mechanisms which determine the effects from laser treatments are the removal of melanin-rich cells and the decrease of average melanin content in basal cells.
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