Abstract
Two-photon photoacoustic microscopy (TP-PAM) can visualize inside of living structures deeper than a millimeter with optically-determined spatial resolution. However, the generation efficiency of two-photon photoacoustic (PA) signals is usually lower than that of one-photon PA signals. Thus, it is important to improve the generation and detection efficiencies of two-photon PA signals. In this presentation, we report the improvement of contrast in TP-PAM by time-gated detection. If the positions of the objective lens and acoustic transducer are fixed, the timing to detect two-photon PA signals by the acoustic transducer does not change. This is because two-photon PA signals are definitely generated from the laser focus. By adjusting the time-gated window to the time it takes for two-photon PA signals to reach the acoustic transducer, two-photon PA signals are able to be detected effectively. Additional technique of the time-gated detection to previously-reported image subtraction method enables us to visualize the cross-sectional melanin- and hemoglobin-contained structures more precisely.
