Photoacoustic Tomography of Microcirculation

Photoacoustic tomography (PAT), a hybrid technology combining optical excitation and ultrasonic detection, senses functional or molecular optical absorption contrasts and enables high&resolution imaging as deep as the optical diffusive regime. PAT for label&free microvascular imaging is highly desirable because of the presence of hemoglobin as an endogenous chromophore. In this chapter, we first review two major embodiments of PAT (photoacoustic microscopy and photoacoustic computed tomography). Then, we introduce methods for in vivo quantification of total hemoglobin concentration, blood oxygenation, and blood flow. After that, we show a few recent biomedical applications, including angiogenesis monitoring, brain and ocular imaging, and in vivo detection of circulating tumor cells. We end by summarizing the current status of microvascular applications of PAT and proposing several future research directions.