Photoacoustic Microscopy: Technological Advances, Biomedical Applications, and Future Perspectives.

Photoacoustic microscopy (PAM) is a powerful subbranch of photoacoustic imaging that achieves microscale spatial resolution and subcellular-level visualization by exploiting endogenous optical contrast, cross-scale capacity, and multiparametric functional readouts. Despite these strengths, clinical translation of PAM is impeded by technical bottlenecks in scanning speed, optical-acoustic coupling, and image reconstruction. This narrative review synthesizes recent engineering breakthroughs that are overcoming these limitations, including advanced scanning architectures, fiber laser sources, high-sensitivity transducers (e.g., CMUTs and transparent ultrasonic detectors), and deep learning-assisted reconstruction algorithms such as attention-based U-Nets and generative adversarial networks. We further highlight representative biomedical applications across dermatology, cerebrovascular hemodynamics, ophthalmology, and gastrointestinal endoscopy, illustrating PAM's versatile diagnostic potential. Finally, we discuss persistent challenges, such as miniaturization, depth penetration, and regulatory hurdles, and propose translational strategies to accelerate PAM's evolution from a laboratory research tool to a mainstream precision medicine imaging modality.