In vivofunctional microangiography by visiblelight optical coherence tomography

Although hemoglobin oxygen saturation (sO₂) in the microvasculature is an essential physiological parameter of local tissue functions, non-invasive measurement of microvascular sO₂ is still challenging. Here, we demonstrated that visible-light optical coherence tomography (vis-OCT) can simultaneously provide three-dimensional anatomical tissue morphology, visualize microvasculature at the capillary level, and measure sO₂ from the microvasculature in vivo. We utilized speckle contrast caused by the moving blood cells to enhance microvascular imaging. We applied a series of short-time inverse Fourier transforms to obtain the spectroscopic profile of blood optical attenuation, from which we quantified sO₂. We validated the sO₂ measurement in mouse ears in vivo through hypoxia and hyperoxia challenges. We further demonstrated that vis-OCT can continuously monitor dynamic changes of microvascular sO₂.