Photoacoustic microscopy (PAM) has become a premier microscopy tool that can provide the anatomical, functional, and molecular information of animals and humans in vivo. However, conventional PAM systems suffer from limited temporal and/or spatial resolution. Here, we present a fast PAM system and an agent-free localization method based on a stable and commercial galvanometer scanner with a custom-made scanning mirror (L-PAM-GS). This novel hardware implementation enhances the temporal resolution significantly while maintaining a high signal-to-noise ratio (SNR). These improvements allow us to photoacoustically and noninvasively observe the microvasculatures of small animals and humans in vivo. Furthermore, the functional hemodynamics, namely, the blood flow rate in the microvasculature, is successfully monitored and quantified in vivo. More importantly, thanks to the high SNR and fast B-mode rate (500 Hz), by localizing photoacoustic signals from captured red blood cells without any contrast agent, unresolved microvessels are clearly distinguished, and the spatial resolution is improved by a factor of 2.5 in vivo. L-PAM-GS has great potential in various fields, such as neurology, oncology, and pathology.

光声显微镜（PAM）已成为一种主要的显微镜工具，可以在体内提供动物和人类的解剖，功能和分子信息。然而，常规的PAM系统受时间和/或空间分辨率的限制。在这里，我们提出了一种快速的PAM系统和一种基于稳定的商用振镜扫描仪和定制扫描镜（L-PAM-GS）的无代理定位方法。这种新颖的硬件实现方式在保持高信噪比（SNR）的同时，显着提高了时间分辨率。这些改进使我们能够在体内光听和无创地观察小型动物和人的微脉管系统。此外，功能性血流动力学，即微脉管系统中的血流速度，在体内得到了成功的监测和定量。更重要的是，由于高SNR和快速的B模式速率（500 Hz），通过定位来自捕获的红细胞的光声信号而没有任何造影剂，可以清楚地区分未分辨的微血管，空间分辨率提高了2.5倍体内。L-PAM-GS在神经病学，肿瘤学和病理学等各个领域具有巨大的潜力。