High-performance photoacoustic and ultrasound endoscopy through transparent ultrasound transducer in vivo preclinical study of live pigs

Recent advances in biomedical imaging have highlighted photoacoustic (PA) imaging as a key technology, particularly when integrated with conventional ultrasound (US) systems. Within this field, endoscopic PA and US imaging (EPU) represents a significant development, combining PA capabilities with endoscopic US to provide enhanced diagnostic capabilities. This integrated approach enables detailed visualization of vascular structures and blood vessel distribution within gastrointestinal wall layers, improving cancer and tumor detection capabilities. For successful clinical adoption of EPU technology, systems must achieve extended working distances while maintaining superior PA imaging quality and matching the US performance of commercial endoscopes. The optimal configuration requires coaxial alignment of laser and acoustic beams to ensure high signal-to-noise ratios and extended working ranges. While previous EPU implementations utilized ring transducers or opto-acoustic beam combiners for alignment purposes, these approaches encountered various limitations in terms of size reduction, acoustic performance, system complexity, and signal quality. Our research addresses these challenges through the implementation of a miniaturized transparent ultrasound transducer (TUT) in EPU systems. The developed TUT, based on PMN-PT and ITO materials, achieves a center frequency of 21 MHz with 62% bandwidth. Animal trials conducted on rats and pigs demonstrated the system's clinical viability, with successful visualization of porcine esophageal wall layers. This novel TUT-based approach effectively overcomes previous technical limitations, marking a significant advancement in endoscopic imaging technology for medical diagnostics.