In vivo functional chronic imaging of a small animal model using optical‐resolution photoacoustic microscopy

Optical‐resolution photoacoustic microscopy (OR‐PAM) has been validated as a valuable tool for label‐free volumetric microvascular imaging. More importantly, the advantages of noninvasiveness and measurement consistency suggest the use of OR‐PAM for chronic imaging of intact microcirculation. Here, such chronic imaging is demonstrated for the first time by monitoring the healing process of laser‐induced microvascular lesions in a small animal model in vivo . The central part of a 1 mm by 1 mm region in a nude mouse ear was treated under a continuous‐wave laser to create a microvascular lesion for chronic study. The region of interest was imaged before the laser treatment, immediately after the treatment, and throughout the healing process using both the authors’ OR‐PAM system and a commercial transmission‐mode optical microscope. Three‐dimensional microvascular morphology and blood oxygenation information were imaged simultaneously at capillary‐level resolution. Transmission‐mode optical microscopic images were acquired for comparison. OR‐PAM has potential important applications in microcirculatory physiology or pathophysiology, tumor angiogenesis, laser microsurgery, and neuroscience.