Studies on Two-Dimensional Imaging of Oxygen Release from Microvessels.

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An apparatus for the determination of two-dimensional images of oxygen saturation and content of flowing erythrocytes in microvascular network was constructed. (1) The apparatus was composed of an inverted microscope, a video-camera, six interference filters with different wavelength, an image processor and a computer. Based on the difference of absorption spectra of oxygenated and deoxygenated hemoglobin in erythrocytes, the two-dimensional images of oxygen saturation and content of flowing erythrocytes in microvessels were prepared, and the profiles in a crossection of microvessels was also prepared. (2) The quantitative determination using the present apparatus was possible in the range of (hematocrit in %) x (inner diameter in mm) <4.5, thus for all microvessels releasing oxygen to tissues. The accuracy of the measurement was <plus-minus>10%. (3) The decrease of oxygen saturation of erythrocytes in the flow process from arterioles to venules in a microvacular network was imaged. The axial accumulation of erythrocytes, thus the formation of cell-free layr along vessel wall, the Fahraeus effect in narrower microvessels and the inverse Fahraeus effect in capillaires were simultaneously imaged. (4) With the decrease of flow velocity of erythrocytes in microvessels and in acidic pH in the tissues, the oxygen release from flowing erythrocytes was accelerated. (5) The relationship between the rheological properties of erythrocytes (hematocrit, erythrocyte deformation and erythrocyte aggregation) and the flow dynamics of erythrocytes evaluated by the thickness of cell-free layr and the flow resistance was quantitatively evaluated in relation with vascular elasticity. (6) Based on the analysis of reflection spectrum, the oxygen saturation of erythrocytes in microvessels on the surface of brain was also imaged. (7) Several problems for further studies were propose