High-speed wide-field multi-parametric photoacoustic microscopy.

Capable of imaging blood perfusion, oxygenation, and flow simultaneously at the microscopic level, multi-parametric photoacoustic microscopy (PAM) has quickly emerged as a powerful tool for studying hemodynamic and metabolic changes due to physiological stimulations or pathological processes. However, the low scanning speed poised by the correlation-based blood flow measurement impedes its application in studying rapid microvascular responses. To address this challenge, we have developed a new, to the best of our knowledge, multi-parametric PAM system. By extending the optical scanning range with a cylindrically focused ultrasonic transducer (focal zone, 76µm×4.5mm) for simultaneous acquisition of 500 B-scans, the new system is 112 times faster than our previous multi-parametric system that uses a spherically focused transducer (focal diameter, 40 µm) and enables high-resolution imaging of blood perfusion, oxygenation, and flow over an area of 4.5×1mm2 at a frame rate of 1 Hz. We have demonstrated the feasibility of this system in the living mouse ear. Further development of this system into reflection mode will enable real-time cortex-wide imaging of hemodynamics and metabolism in the mouse brain.