High-speed label-free photoacoustic histopathology

Abstract

In tumor resection surgery, the entire tumor must be removed to prevent local recurrence of cancer. To achieve effective and successful tumor resection surgery, an intraoperative examination is performed for quick decision-making during the surgical process. Examination of frozen sections is a common method, but it has limitations that it requires time-consuming tissue processing procedures which leads to interpretation errors. Photoacoustic microscopy (PAM) with ultraviolet (UV) laser is a promising intraoperative surgical margin assessment method that provides depth-resolved and label-free imaging of cell nuclei without sectioning and staining. Despite these advantages, conventional PAM still has limited imaging speed that does not allow real-time imaging, because it achieves the volumetric images by raster scanning using 2-axis step motors. To overcome the limitation, we developed a high-speed reflection-mode OR-PAM based on a UV scanner. Using the scanner module, it took 180 seconds to acquire one volumetric data over 1 × 1 mm2. In an in-vitro test, the measured lateral and axial resolution were 1.2 μm and 65.1 μm, respectively. We performed ex-vivo experiments on paraffin sections of tissues after deparaffinization that had been excised from a kidney, liver, colon-cancer and a liver-cancer patient. We could find structures in tumorous tissues distinguishable from normal tissues in 4 × 8 mm2 which is clinically meaningful FOV. We could also identify single nucleus in UV-PAM images, and match it with the corresponding nucleus in microscopic images. © (2020) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.c