Fast holographic scattering compensation for deep tissue biological imaging

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.

Deep tissue scattering compensation with three-photon F-SHARP

“…Different guidestar-based methods have been developed (24), which use fluorescent targets such as beads (25), photoacoustic feedback (26) or ultrasound (27)(28)(29) to determine the wavefront correction map. An alternative approach is to determine the correction by modulating the SLM pixels to iteratively improve the correction pattern (30)(31)(32)(33). However, the measurement speed of this approach is limited by the modulation speed of the SLM.…”

Recent advances in optical imaging through deep tissue: imaging probes and techniques

“…The visual cortex and Hippocampus of mouse brain in vivo [39] Synaptic structures in the deep cortical region of a Thy1-GFP mouse brain [40] High and basal dendritic spines of a mouse V1 neuron in vivo [41] GFP expressed microtubule of Drosophila larval macrophage [42] GFP-expressed pyramidal neuron in a living mouse brain [43] Single microglia cell from hippocampus tissue of a mouse brain [44] Coherence-gating Label-free, High sensing speed / Mixed phase retardations of input and output paths, Deal with low-order aberration modes…”

“…Adapted with permission from Ref. [44]. Scale bar in b, 5 μm below 630 μm in a living brain were acquired by using a three-photon laser combined with F-SHRAP (Fig.…”

“…A different holographic technique of indirect sensing was reported, which provided non-invasive scattering compensation using the phase information obtained by a holographic phase interferometer, thereby, the system rapidly corrected the sample-induced aberration with just one measurement [44]. The dynamic adaptive scattering compensation holography (DASH) integrated with a twophoton microscope enabled to measure single microglia cell images from 530 μm thick tissue from the hippocampus of a mouse brain (Fig.…”

Fast wavefront shaping for two-photon brain imaging with large field of view correction

“…Technically, larger field of view in imaging through scattering media would require AO correction at an update rate equal to the pixel scan rate divided by the size of the memory effect of the medium in pixel units. While fast wavefront shaping based on highspeed spatial light modulators [11][12][13] and hybrid strategies 8,14,15 was developed to tackle the fast decorrelation time of biological tissues in depth, their update speeds remain too slow to keep up with typical pixel scan rates. Sufficiently fast wavefront update was so far only demonstrated in one dimension and without implementation into a microscope 16 .…”