In vivo photoacoustic microscopy with 7.6-µm axial resolution using a commercial 125-MHz ultrasonic transducer.

Photoacoustic microscopy has achieved submicron lateral resolution, but its axial resolution is much lower. Here an axial resolution of 7.6 μm, the highest axial resolution validated by experimental data, has been achieved by using a commercial 125 MHz ultrasonic transducer for signal detection followed by the Wiener deconvolution for signal processing. Limited by the working distance, the high-frequency ultrasonic transducer can penetrate 1.2 mm into biological tissue from the ultrasound detection side. At this depth, the signal-to-noise ratio decreases by 11 dB, and the axial resolution degrades by 36%. The new system was demonstrated in imaging melanoma cells ex vivo and mouse ears in vivo.