Noninvasive quantification of metabolic rate of oxygen (MRO 2 ) by photoacoustic microscopy

Many diseases, normal decay and physiological functions are closely related to alterations in the metabolic rate of oxygen (MRO₂). In this study, we demonstrate that all the parameters for MRO₂ quantification can be simultaneously obtained by optical-resolution photoacoustic microscopy (OR-PAM). MRO₂ of the mouse ear under normothermia (31 °C skin temperature) and controlled systematic hyperthermia (42 °C skin temperature) was studied. As a result of hyperthermia, the MRO₂ increased by 34.1%. The tumor hypermetabolism was also demonstrated by longitudinally monitoring a melanoma growing on a mouse ear. The results show that OR-PAM, as a single noninvasive imaging modality, is well suited for quantitative MRO₂ measurement in microenvironments.