We studied quantitative evaluation of skin erythema using dorsum of hand images of photodynamic therapy (PDT) patients before and after the exposure to sunlight. While PDT is used as a minimally invasive cancer treatment, there is a problem of photosensitivity caused by residual photosensitizer in the skin. To prevent this problem, a dark hospitalization of two weeks in a room with less than 500 lx is prescribed in the case of Npe6 in Japan. After 2 weeks of a dark hospitalization, dorsum of hand is exposed to sunlight for 5 minutes, and the photosensitivity is visually judged to determine the end of a dark hospitalization, but this method has the problem of being qualitative and invasive. The purpose of this study was to quantitatively evaluate cutaneous photosensitivity by analyzing dorsum of hand images of PDT patients before and after the exposure to sunlight using three colorimetric systems. Dorsum of hand images before and after sunlight exposure of nine PDT patients were taken along with color scales. Image processing software was used to extract the sRGB values of the sunlight-exposed area and color scale from the acquired images as histograms. The sRGB values of the color scale of the images were used to correct the imaging conditions and to compare the images before and after sunlight exposure in three color systems: sRGB, CIELAB, and HSV color system. We suggest that the G values of sRGB has the possibility of quantitative evaluation of erythema and photosensitivity.
We investigated the photothermal effect of near-infrared pulsed laser irradiation on collagen synthesis in fibroblasts in vitro to reduce complications in skin rejuvenation therapy by selective collagen heating. Tissue thermal damage with pain by laser heating of water is a problem in conventional laser skin rejuvenation therapy. To reduce these complications, we suggest heating collagen fibril selectively by applying selective photothermolysis. Laser parameters such as wavelength, pulse duration, pulse interval, and irradiance are important for selective heating. Fibroblasts will be heated gently by conducted heat from collagen fibril in our process, which enhances the expression of heat shock protein 47 (HSP47) in fibroblasts. This procedure would reduce pain and thermal damage on fibroblasts compared with the conventional procedure. In this study, we evaluated the amount of HSP47 content per living cell to investigate the photothermal effect on fibroblasts. The temperature distribution of the dermis during laser irradiation was simulated by the finite element method (FEM). 1480 and 1550 nm pulsed laser was irradiated to cultured fibroblasts. The laser emitted with a pulse duration of 100 μs, repetition of 2 kHz, fluence of 0 - 60 J/cm2 , and irradiance of 0.5 W/cm2 . To evaluate cell functional changes in time, ELISA and cell viability assay were performed 24 and 48 hours after laser irradiation.
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