Fast holographic scattering compensation for deep tissue biological imaging

Scattering in biological tissues is a major barrier for in vivo optical imaging of all but the most superficial structures. Progress toward overcoming the distortions caused by scattering in turbid media has been made by shaping the excitation wavefront to redirect power into a single point in the imaging plane. However, fast, non-invasive determination of the required wavefront compensation remains challenging. Here, we introduce a quickly converging algorithm for non-invasive scattering compensation, termed DASH, in which holographic phase stepping interferometry enables new phase information to be updated after each measurement. This leads to rapid improvement of the wavefront correction, forming a focus after just one measurement iteration and achieving an order of magnitude higher signal enhancement at this stage than the previous state-of-the-art. Using DASH, we demonstrate two-photon fluorescence imaging of microglia cells in highly turbid mouse hippocampal tissue down to a depth of 530 mu m. Wavefront shaping is used to overcome scattering in biological tissues during imaging, but determining the compensation is slow. Here, the authors use holographic phase stepping interferometry, where new phase information is updated after each measurement, enabling fast improvement of the wavefront correction.

Automated summary

Scattering in biological tissues is a major hindrance for in vivo optical imaging, but wavefront shaping has shown promise in overcoming this challenge. The authors introduced an algorithm called DASH, which utilizes holographic phase stepping interferometry to quickly update phase information after each measurement, leading to rapid improvement in wavefront correction. This method achieved a significant increase in signal enhancement compared to previous technologies after just one measurement iteration.