Label-free optical imaging of 3D structural and functional microcirculations

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DESCRIPTION (provided by applicant): The primary objective for the proposed project is to develop a novel high-resolution (<10 5m), real-time and non-invasive optical imaging tool that is capable of comprehensive, simultaneous, and quantitative assessments of blood perfusion and tissue oxygen consumption within a scanned tissue volume up to 2 mm in depth without the use of labeling technique. Non-invasive and label-free imaging techniques for quantifying blood flow and blood oxygenation - down to capillary-level resolution - are of paramount importance for the improved understanding, diagnosis, and treatment of diseases that have peripheral vascular involvement, such as stroke, traumatic brain injury, hemorrhage, retinopathy, and cancer. Currently no optical imaging techniques are available that can offer simultaneous measurements of blood perfusion and oxygen consumption at a critical imaging depth (>1mm) within microcirculatory tissue beds in vivo. The proposed imaging tool - functional optical micro-angiography (fOMAG) - is a comprehensive and label- free volumetric imaging technology designed to simultaneously image and quantify blood perfusion and the oxygenation status of perfused blood within a scanned tissue volume. fOMAG will be designed to: 1) Image the detailed vessel architectures by separating endogenous optical signals backscattered from blood flow, from those endogenous optical signals backscattered from the tissue background (i.e. from bulk static tissue); 2) Determine volumetric blood flow by employing a novel Doppler OMAG technique. This technique is based on the linear relationship between phase-changes in the optical fOMAG signals and the blood flow velocity when fOMAG images the tissue; 3) Map the oxygenation status of the blood perfusion by a novel spectroscopic OMAG technique, which relies on the different molar extinction coefficients between the oxygenated and de- oxygenated hemoglobin in the near-infrared region at 800 nm wavelength band. The project will test the hypothesis that blood perfusion and oxygen consumption in tissues can be invasively and reliably imaged, quantified, and characterized simultaneously in real time, at 0- to 2-mm tissue depths and at a resolution of <10 5m. The specific aims of the project are to: 1) construct an fOMAG imaging system, 2) develop a novel phase- resolved Doppler OMAG to quantify volumetric blood flow, 3) characterize a novel spectroscopic OMAG to image oxygen saturation in blood vessels, 4) validate fOMAG In vivo by volumetric imaging of cerebral blood perfusion in mice, and 5) investigate the utility of fOMAG for non-invasive transcranial monitoring of changes in cerebrovascular blood flow and healing-associated neovascularization after traumatic brain injury in mice. PUBLIC HEALTH RELEVANCE: We propose to develop a novel biomedical imaging technology, functional optical micro-angiography that can provide the simultaneous, quantitative assessment of tissue blood perfusion and oxygen consumption within a scanned tissue volume in vivo non-invasively and without the use of labeling techniques. This novel imaging technique will become an important tool to investigate blood supply to tissues, and may help diagnosis, monitoring, and therapeutic interventions in diseases with vascular involvement.