<i>In vivo</i> Micro-Tomographic Visualization of Capillary Angio-Dynamics Around Upper Dermis Under Mechanical Stimulus Using Low Coherence Interferometer “Optical Coherence Doppler Velocigraphy”

Abstract

The skin aging process, e.g. wrinkles and sagging, caused by not only aging but also ultraviolet irradiation, could be related to the depression of metabolic function. Therefore, an in vivo quantitative measurement of capillary blood flow velocity governing skin metabolism functionally, i.e. microcirculation, is crucial to clarify the skin aging and to create skincare products. The purpose of this study is to visualize the tomographic velocity of red blood cell in capillaries just below human epidermal skin using Optical Coherence Doppler Velocigraphy, namely OCDV. This was constructed on a low coherence interferometer, which could provide tomographic distribution of flow-modulated Doppler frequency by developing OCDV algorithm of Hilbert transform and adjacent autocorrelation. In order to validate OCDV system, this was in vivo applied to human forearm skin under respective mechanically stimulated conditions of control and avascularization. As a result, a cross-sectional imaging of blood flow velocity was found to display not only morphological OCT images but also networks of capillary vasculature inside dermal tissue. It was confirmed that blood flow velocity further decreased in upper dermis under avascularization than control condition. Additionally, OCDV could provide a velocity map of blood flow having sensitivity to mechanical stimulus, so has strong efficacy to diagnose “Capillary Angio-Dynamics” of skin tissue. In conclusions, OCDV system could be quite useful for a micro-tomographic imaging of blood flow velocity of capillaries inside skin.