Abstract
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 μm.
Highlights
Scattering in biological tissues is a major barrier for in vivo optical imaging of all but the most superficial structures
Numerical simulations and experimental evaluations of the dynamic adaptive scattering compensation holography (DASH) algorithm in two-photon excited fluorescence microscopy (TPEF) reveal signal enhancement that is roughly 10x higher at the end of the first iteration compared to focus scanning holographic aberration probing (F-SHARP) and iterative multi-photon adaptive compensation technique (IMPACT), the exact enhancement ratio can vary based on experimental factors like the structure of the scatterer and the accuracy of the FSHARP interferometer alignment
We show numerically that DASH efficiently uses the information from each measured photon, allowing correction with about half as many collected photons and requiring half as many measurements compared to stepwise algorithms
Summary
Scattering in biological tissues is a major barrier for in vivo optical imaging of all but the most superficial structures. We introduce dynamic adaptive scattering compensation holography (DASH), a new algorithm that enables significantly faster convergence than IMPACT and F-SHARP.
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