From lab design to clinical translation: photoacoustic endoscopy.

Photoacoustic endoscopy (PAE) integrates pulsed optical excitation and acoustic detection within miniaturized probes for intraluminal and intracavitary imaging. By combining optical absorption contrast with ultrasound-based detection, PAE complements conventional endoscopy by visualizing subsurface vasculature and providing functional or compositional contrast, including hemoglobin oxygenation, lipid-rich tissue, collagen-associated signals, and molecular probes. This review summarizes scenario-driven PAE development from engineering design to translational application, focusing on optical excitation, acoustic detection, and scanning strategies. We analyze trade-offs among resolution, depth of field, sensitivity, imaging speed, field of view, probe dimensions, and workflow compatibility, and review representative applications in cardiovascular, gastrointestinal, reproductive, urinary, respiratory, and surgical-guidance settings. Current evidence remains largely preclinical or early feasibility. Future translation requires standardized quantitative metrics, laser safety evaluation, robust engineering and prospective clinical validation.