Photoacoustic microscopy: a potential new tool for evaluation of angiogenesis inhibitor.

The feasibility of photoacoustic microscopy (PAM) for evaluation of angiogenesis inhibitor was investigated on a chick embryo model in vivo. Different concentrations of the angiogenesis inhibitor, Sunitinib, were applied to the chorioallantoic membrane (CAM) of the chick embryos. Imaging of microvasculature in embryo CAMs was acquired using a laser-scanning PAM system; while the optical microscopy (OM) capturing the microvascular images of the same set of CAMs for comparison served as a gold standard for validating the results from PAM. The microvascular density as a function of applied Sunitinib concentration has been quantified in both PAM and OM images. The results from these two modalities have a good agreement, suggesting that PAM could provide an unbiased quantification of microvascular density for objective evaluation of anti-angiogenesis medication. In comparison with conventional OM which enables only two-dimensional enface imaging, PAM is capable of three-dimensional analysis of microvessels, including not only morphology but also functions, as demonstrated in part by the imaging result on a canine bladder model. The emerging PAM technique shows promise to be used in clinical and preclinical settings for comprehensive and objective evaluation of anti-angiogenesis medications.