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 (SO_2) 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 SO_2 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 SO_2 values and variations in SO_2 between different physiological states (hyperoxia, normoxia, and hypoxia) were imaged in single blood vessels