An acoustic-optic confocal probe based photoacoustic and ultrasonic tracheal endoscopy for characterizing phantom and model of chronic obstructive pulmonary disease

Integrated photoacoustic endoscopy and endoscopic ultrasound (PAE/EUS) are recognized as an effective method for detecting intestinal and intravascular diseases. Changes in the morphology and composition of the trachea are significant hallmarks of respiratory diseases. In this study, an acoustic-optic confocal probe was developed and integrated at the tip of a 2.1 mm diameter catheter to perform simultaneous PAE/EUS imaging. Phantom experimental results demonstrated that the catheter achieved a high lateral resolution of 11 µm, with an imaging depth of 12 mm, using an excitation energy of 1.5 μJ. Trachea from healthy and chronic obstructive pulmonary disease (COPD) rabbit models and in vivo were imaged by the PAE/EUS system. The results demonstrated that photoacoustic imaging could identify increases in the diameter and density of the tracheal microvessels, while ultrasound imaging provided detailed views of the tracheal submucosa. These findings underscore the potential of PAE/EUS in the diagnosis of COPD.