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

Abstract

Cerebral metabolic rate of oxygen ( ) consumption is a key physiological variable that characterizes brain metabolism in a steady state and during functional activation. We aim to develop a minimally invasive optical technique for real-time measurement of concurrently with cerebral blood flow (CBF). 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. The method enables computation and tracking of during functional activation with high temporal resolution ( ). In contrast to other approaches, our assessment of does not require measurements of CBF or hemoglobin oxygen saturation. The independent records of intravascular and extravascular partial pressures of oxygen, CBF, and provide information about the physiological events that accompany neuronal activation, creating opportunities for dynamic quantification of brain metabolism.