A major obstacle in understanding the mechanism of ischemic stroke is the lack of a tool to noninvasively or minimally
invasively monitor cerebral hemodynamics longitudinally. Here, we applied optical-resolution photoacoustic microscopy
(OR-PAM) to longitudinally study ischemic stroke induced brain injury in a mouse model with transient middle cerebral
artery occlusion (MCAO). OR-PAM showed that, during MCAO, the average hemoglobin oxygen saturation (sO2)
values of feeder arteries and draining veins within the stroke core region dropped ~10% and ~34%, respectively. After
reperfusion, arterial sO2 recovered back to the baseline; however, the venous sO2 increased above the baseline value by
~7%. Thereafter, venous sO2 values were close to the arterial sO2 values, suggesting eventual brain tissue infarction.