In vivo electron paramagnetic resonance oximetry and applications in the brain

Molecular oxygen (O(2)) is essential to brain function and mechanisms necessary to regulate variations in delivery or utilization of O(2) are crucial to support normal brain homeostasis, physiology and energy metabolism. Any imbalance in cerebral tissue partial pressure of O(2) (pO(2)) levels may lead to pathophysiological complications including increased reactive O(2) species generation leading to oxidative stress when tissue O(2) level is too high or too low. Accordingly, the need for oximetry methods, which assess cerebral pO(2) in vivo and in real time, is imperative to understand the role of O(2) in various metabolic and disease states, including the effects of treatment and therapy options. In this review, we provide a brief overview of the common in vivo oximetry methodologies for measuring cerebral pO(2). We discuss the advantages and limitations of oximetry methodologies to measure cerebral pO(2) in vivo followed by a more in-depth review of electron paramagnetic resonance oximetry spectroscopy and imaging using several examples of current electron paramagnetic resonance oximetry applications in the brain.