Inverted multiscale optical resolution photoacoustic microscopy.

Optical resolution photoacoustic microscopy (ORPAM) is one of the fastest evolving photoacoustic imaging modalities. It not only has a comparable spatial resolution to pure optical microscopies such as epifluorescence microscopy, confocal microscopy, and two-photon microscopy, but also owns a higher penetration depth. In this study, we report an inverted multiscale (IM)-ORPAM that utilizes a two-dimensional galvanometric scanner integrated with two microscopic imaging lenses to achieve rotary-scanning-based multiscale imaging. A 15 MHz cylindrically focused ultrasonic transducer is mounted on a motorized rotator to synchronously follow the optical scanning paths. To minimize the loss of signal-to-noise ratio, the acoustic focal line is precisely adjusted confocal with the optical focal plane. Black tapes, carbon fibers, and sharp blades are imaged to evaluate the performance of the system, and in vivo multiscale imaging of vasculatures inside the ears and brains of mice is demonstrated using this system.