Photoacoustic microscopy of cerebral blood-oxygenation dynamics in mice

In this work, we exploit the high depth and temporal resolutions of PAM to noninvasively image the blood-oxygenation dynamics of multiple cortex vessels in the mouse brain simultaneously in response to controlled hypoxic and hyperoxic challenges. The dark-field photoacoustic microscopy (PAM) technique was enhanced to image the cortex vasculature of the mouse brain in vivo using endogenous hemoglobin contrast with one second temporal resolution. The maximum values of about 20% with standard deviation ± 1.2% were found to vary significantly among the cortex vessels studied. The hypoxic response time to rise from 10 % to 90 % of maximum was 63 ± 6 sec. The reverse response time for this event was 16 ± 2 sec.