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Hyperspectral Imaging of Diabetes Mellitus Skin Complications
Published in Andrey V. Dunaev, Valery V. Tuchin, Biomedical Photonics for Diabetes Research, 2023
Viktor V. Dremin, Evgenii A. Zherebtsov, Alexey P. Popov, Igor V. Meglinski, Alexander V. Bykov
The increase in BVF in the skin (shown in Figure 8.7a) causes the decrease of skin reflectance within the entire spectral range of 500–900 nm. However, the most significant changes are observed in the region of strong blood absorption (500–600 nm). The most prominent changes in the skin reflectance caused by the variation in blood oxygen saturation are observed in the range of 600–800 nm (see Figure 8.7b). The influence of the melanin content in the epidermis is shown in Figure 8.7c. It is seen that an increase in melanin content decreases the reflectance in the entire spectral range considered. However, the change in the shape of spectra is significantly different compared to the increase in BVF. Increase in the epidermal thickness (see Figure 8.7d) acts differently for the spectral region 500–600 nm and 600–900 nm. Below 600 nm, the increase in the epidermal thickness causes an increase in skin reflectance; however, for the longer wavelengths, a similar increase causes a decrease in reflectance. This effect can be explained by the significantly lower (up to two orders of magnitude) absorption of oxyhemoglobin in the red-IR spectral region relative to absorption in the green region. Thus, the oxygenated blood turns into a moderate absorber, and the decrease in the reflectance in the red-IR region is caused by the increased optical density of the epidermis.
Modelling and analysis of skin pigmentation
Published in Ahmad Fadzil Mohamad Hani, Dileep Kumar, Optical Imaging for Biomedical and Clinical Applications, 2017
Ahmad Fadzil Mohamad Hani, Hermawan Nugroho, Norashikin Shamsudin, Suraiya H. Hussein
Two observational studies have been conducted to evaluate the developed system. In these studies, the skin reflectance of participants and lesion reflectance data of patients have been obtained using spectrophotometer. The selected lesion and normal skin, in this case, must have an area with diameter not less than 7 mm.
The 21-day cumulative irritation assay in man: a half-century summary and re-evaluation
Published in Cutaneous and Ocular Toxicology, 2021
Since the evaluation used in the 21-day CIT is visual, a question regarding its objectivity arises. Many bioengineering instruments have been developed to address this question, using either measurements from microvascularization (laser Doppler velocimetry) or skin reflectance (tristimulus colorimeter, spectroradiometer, and two-channel erythema metre). Table 2 summarises these instruments' principles and advantages, which are also discussed in depth in the following passages.