We report a handheld multi-parametric photoacoustic microscopy system for functional and oxygen-metabolic imaging of the human skin microvasculature. With the high spatiotemporal resolution (3 μm and 10-Hz frame rate), the traverse of single red blood cells through the capillary can be visualized, from which the flow speed can be quantified. Furthermore, the multi-parametric measurement enables comprehensive quantification of the oxygen saturation and release in individual microvessels. The utility of this new technique has been demonstrated by studying the microvascular reactivity in humans.
We report a new multi-parametric photoacoustic microscopy (PAM) system, which enables high-resolution imaging of blood perfusion, oxygenation and flow at 0.2-Hz frame rate over an area of 4.5×4.5 mm2. Extending the laser scanning range by using a cylindrically focused transducer (focus: 50 µm by 4.5 mm), it increases the speed of our previous hybrid-scan system with a weakly focused transducer (focal diameter: 250 µm) by 18-fold without compromising the sensitivity. We have demonstrated the feasibility of this technique in the transmission mode in vivo. Further development of a reflection-mode system will enable real-time cortex-wide imaging of cerebral hemodynamics and metabolism.