Optical-resolution photoacoustic microscopy (OR-PAM) is an emerging technique that directly images optical absorption in tissue at high spatial resolution. To date, the majority of OR-PAM systems are based on single-focused optical excitation and ultrasonic detection, limiting the wide-field imaging speed. While 1D multifocal OR-PAM (1D-MFOR-PAM) has been developed, the potential of microlens and transducer arrays has not been fully realized. Here we present the development of 2D multifocal optical-resolution photoacoustic-computed microscopy (2D-MFOR-PACM), using a 2D microlens array and a full-ring ultrasonic transducer array. The microlens array generates 1800 optical foci within the focal plane of the 512-element transducer array, and raster scanning the microlens array yields optical-resolution photoacoustic images. The system has improved the in-plane resolution of a full-ring transducer array from to 29 μm and achieved an imaging time of 36 s over a field of view. In comparison, the 1D-MFOR-PAM would take more than 4 min to image over the same field of view. The imaging capability of the system was demonstrated on phantoms and animals both ex vivo and in vivo.
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