High-resolution in vivo optical-sectioning widefield microendoscopy

Microendoscopy incorporating a gradient index (GRIN) lens has emerged as a powerful tool for in vivo imaging. The lack of optical sectioning capability of widefield microendoscopy and the intrinsic optical aberrations of the GRIN lens itself, however, limit the achievable image contrast and resolution in three-dimensional (3D) tissues. In this study, we applied HiLo, a structured illumination method, to widefield microendoscopy in order to achieve optical sectioning. We also utilized adaptive optics (AO) to measure and correct GRIN lens aberrations. Together, HiLo and AO enabled subcellular-resolution microendoscopy imaging with optical sectioning and allowed us to image fine neuronal processes and synapses in the mouse brain in vivo. © 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.