An Ultraviolet‐Transparent Ultrasound Transducer Enables High‐Resolution Label‐Free Photoacoustic Histopathology

Abstract Ultraviolet photoacoustic microscopy (UV‐PAM), based on the high intrinsic optical absorption of DNA/RNA, holds great promise for intraoperative label‐free histopathological imaging modalities. Although clinical histopathology requires high‐resolution images to observe individual cell structures, conventional UV‐PAM suffers from relatively low resolution compared to the clinical histological modalities. Notably, opto‐ultrasound beam combiners or ring‐shaped ultrasound transducers, which have been used as geometrically coaxial methods of conventional reflection‐mode UV‐PAMs, restrict the numerical apertures (NA) due to their long working distances and/or hollow structures. Here, an ultraviolet‐transparent ultrasound transducer (UV‐TUT) is demonstrated that enables high‐resolution reflection‐mode UV‐PAM by improving the NA (0.38) and consequent spatial resolution (0.47 ± 0.03 µm). The study has successfully demonstrated its superior performance with mouse brain tissue and performed photoacoustic histopathology with cancerous animal tissues. This work proposes the ultimate form of a label‐free reflection‐mode UV‐PAM system with the potential to boost the practical use of intraoperative photoacoustic histopathology.