Capillary Vessels (IMAGE) Northwestern University Caption An image of capillaries taken with spectral contrast optical coherence tomography angiography, which is the first technology to capture blood flow and oxygen exchange. Credit Vadim Backman/Northwestern University Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.