Real-time tracking of brain oxygen gradients and blood flow during functional activation

SIGNIFICANCE: Cerebral metabolic rate of oxygen ([Formula: see text]) consumption is a key physiological variable that characterizes brain metabolism in a steady state and during functional activation. AIM: We aim to develop a minimally invasive optical technique for real-time measurement of [Formula: see text] concurrently with cerebral blood flow (CBF). APPROACH: We used a pair of macromolecular phosphorescent probes with nonoverlapping optical spectra, which were localized in the intra- and extravascular compartments of the brain tissue, thus providing a readout of oxygen gradients between these two compartments. In parallel, we measured CBF using laser speckle contrast imaging. RESULTS: The method enables computation and tracking of [Formula: see text] during functional activation with high temporal resolution ([Formula: see text]). In contrast to other approaches, our assessment of [Formula: see text] does not require measurements of CBF or hemoglobin oxygen saturation. CONCLUSIONS: The independent records of intravascular and extravascular partial pressures of oxygen, CBF, and [Formula: see text] provide information about the physiological events that accompany neuronal activation, creating opportunities for dynamic quantification of brain metabolism.