Photoacoustic endomicroscopy combined with ultrasound (PAEM-US) has been a long-standing expectation for gastrointestinal tumor examination. Here, we introduce a prototype disposable PAEM-US catheter and corresponding power interface unit, featuring catheter switchability, self-internal three-dimensional scanning, and system repeatability for gastrointestinal endoscopy. By utilizing high-fluence relays, cascade insertion loss of the optical waveguide is minimized to 0.6 dB with a high performance of power resistance, and a focus-customizable acousto-optic coaxial probe is designed for high-sensitivity optical-resolution photoacoustic imaging. Imaging capability was demonstrated with in vivo anatomical imaging at 30 frames per second. Imaging results showed co-registered microscopic visualization of the microvascular and stratification of the rat colorectum with lateral resolution of 18 μm and axial resolution of 63 μm, holding great potential in the clinical detection of gastrointestinal diseases.

The mechanical properties of organisms are important indicators for clinical disputes and disease monitoring, yet most existing elastography techniques are based on contact measurements, which are limited in many application scenarios. Photoacoustic remote sensing elastography (PARSE) is the first, to the best of our knowledge, elastography modality based on acoustic pressure monitoring, where elastic contrast information is obtained by using an all-optical non-contact and non-coherent intensity monitoring method through the time-response properties of laser-induced photoacoustic pressure. To validate PARSE, sections of different elastic organs were measured and this modality was applied to differentiate between bronchial cartilage and soft tissue to confirm the validity of the elasticity evaluation. PARSE, through a mathematical derivation process, has a 9.5-times greater distinction detection capability than photoacoustic remote sensing (PARS) imaging in stained bronchial sections, expands the scope of conventional PARS imaging, and has potential to become an important complementary imaging modality.