Imaging of hemoglobin oxygen saturation variations in single vessels in vivo using photoacoustic microscopy

Photoacoustic microscopy was used to noninvasively image variations in hemoglobin oxygen saturation (SO2) in the subcutaneous microvasculature of rats in vivo. In phantom tests, the calculated concentration fractions of red ink in double-ink mixtures matched the actual values with a 1% error. In ex vivo studies, the calculated SO2 in bovine blood agreed with the standard spectrophotometric measurements within a 4% systematic difference. In in vivo studies, arteries and veins were separated based on the measured SO2 values and variations in SO2 between different physiological states (hyperoxia, normoxia, and hypoxia) were imaged in single blood vessels.