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Published July 2011 | Published
Journal Article Open

Label-free oxygen-metabolic photoacoustic microscopy in vivo


Almost all diseases, especially cancer and diabetes, manifest abnormal oxygen metabolism. Accurately measuring the metabolic rate of oxygen (MRO_2) can be helpful for fundamental pathophysiological studies, and even early diagnosis and treatment of disease. Current techniques either lack high resolution or rely on exogenous contrast. Here, we propose label-free metabolic photoacoustic microscopy (mPAM) with small vessel resolution to noninvasively quantify MRO_2 in vivo in absolute units. mPAM is the unique modality for simultaneously imaging all five anatomical, chemical, and fluid-dynamic parameters required for such quantification: tissue volume, vessel cross-section, concentration of hemoglobin, oxygen saturation of hemoglobin, and blood flow speed. Hyperthermia, cryotherapy, melanoma, and glioblastoma were longitudinally imaged in vivo. Counterintuitively, increased MRO_2 does not necessarily cause hypoxia or increase oxygen extraction. In fact, early-stage cancer was found to be hyperoxic despite hypermetabolism.

Additional Information

© 2011 SPIE. Paper 11075R received Feb. 17, 2011; revised manuscript received Apr. 12, 2011; accepted for publication May 5, 2011; published online Jul. 1, 2011. The authors thank Christopher Favazza, Kim Chulhong, Song Hu, Lidai Wang, Dakang Yao, and Arie Krumholz for helpful discussions; Li Li for experimental assistance; and Professor James Ballard for manuscript editing. This research was supported by the National Institutes of Health Grants Nos. R01 EB000712, R01 EB008085, R01 CA134539, U54 CA136398, R01 EB010049, and 5P60 DK02057933.

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