Multifocal photoacoustic microscopy using a single-element ultrasonic transducer through an ergodic relay

Optical-resolution photoacoustic microscopy(OR-PAM)has demonstrated high-spatial-resolution imaging of optical absorption in biological tissue.To date,most OR-PAM systems rely on mechanical scanning with confocally aligned optical excitation and ultrasonic detection,limiting the wide-field imaging speed of these systems.Although several multifocal OR-PA(MFOR-PA)systems have attempted to address this limitation,they are hindered by the complex design in a constrained physical space.Here,we present a two-dimensional(2D)MFOR-PAM system that utilizes a 2D microlens array and an acoustic ergodic relay.Using a single-element ultrasonic transducer,this system can detect PA signals generated from 400 optical foci in parallel and then raster scan the optical foci patterns to form an MFOR-PAM image.This system improves the imaging resolution of an acoustic ergodic relay system from 220 to 13μm and enables 400-folds shorter scanning time than that of a conventional OR-PAM system at the same resolution and laser repetition rate.We demonstrated the imaging ability of the system with both in vitro and in vivo experiments.

Slide-free histological imaging by microscopy with ultraviolet surface excitation using speckle illumination

Microscopy with ultraviolet surface excitation(MUSE)is a promising slide-free imaging technique to improve the time-consuming histopathology workflow.However,since the penetration depth of the excitation light is tissue dependent,the image contrast could be significantly degraded when the depth of field of the imaging system is shallower than the penetration depth.High-resolution cellular imaging normally comes with a shallow depth of field,which also restricts the tolerance of surface roughness in biological specimens.Here we propose the incorporation of MUSE with speckle illumination(termed MUSES),which can achieve sharp imaging on thick and rough specimens.Our experimental results demonstrate the potential of MUSES in providing histological images with~1μm spatial resolution and improved contrast,within 10 minutes for a field of view of 1.7 mm×1.2 mm.With the extended depth of field feature,MUSES also relieves the constraint of tissue flatness.Furthermore,with a color transformation assisted by deep learning,a virtually stained histological image can be generated without manual tuning,improving the applicability of MUSES in clinical settings.