In vivo anatomical imaging of colorectum by tens-of-micron-resolved photoacoustic/ultrasonic endoscope

The existing photoacoustic/ultrasound (PA/US) endoscopes with compromise in lateral resolution were difficult to realize superior anatomical imaging. To obtain comprehensive biological information of the colorectum in a noninvasive manner, a tens-of-micron-resolved PA/US endoscope with a 360° field of view was developed. A coaxial structure, which ensures optical and acoustic foci aligned, was employed, and a PVDF-based focused transducer with a high frequency was applied. The endoscopic system achieved lateral resolutions of 16 μm (PA) and 73 μm (US), and axial resolution of 65 μm. Phantom and ex vivo experiments were performed to estimate the performance of the dual-modality endoscope. In vivo three-dimensional imaging of rabbit colorectum exhibited the intact vascular network at different depths from the mucosa of the colorectal wall to the mesentery, and the structures beneath them. Therefore, in vivo anatomical imaging demonstrates that the tens-of-micron-resolved PA/US endoscope holds great potential in the clinical detection of colorectal diseases.