Reflection-mode photoacoustic microscopy using a hollow focused ultrasound transducer for in vivo imaging of blood vessels

A reflection-mode photoacoustic microscope using a hollow focused ultrasound transducer is developed for high-resolution in vivo imaging. A confocal structure of the laser and the ultrasound is used to improve the system resolution. The axial and lateral resolutions of the system are measured to be ～ 32 μm and ～ 58 μm, respectively. Ex vivo and in vivo modes are tested to validate the imaging capability of the photoacoustic microscope. The adjacent vein and artery can be seen clearly from the reconstructed photoacoustic images. The results demonstrate that the reflection-mode photoacoustic microscope can be used for high-resolution imaging of micro-blood vessels, which would be of great benefit for monitoring the neovascularization in tumor angiogenesis.