High-resolution dynamic full-field optical coherence microscopy: illuminating intracellular activity in deep tissue.

Dynamic full-field optical coherence microscopy (d-FF-OCM) is a label-free imaging technique that captures intrinsic subcellular motions to generate functional contrast. This dynamic approach yields images with fluorescence-like contrast, highlighting active structures without the need for fluorescent labels. However, current d-FF-OCM implementations have limitations when imaging deep within highly scattering tissues at high resolution. Here, we present a new high-resolution d-FF-OCM system that overcomes these limitations, enabling depth-extended high-resolution imaging in such tissues. The setup uses 100× oil-immersion objectives (NA = 1.25) and a high-brightness, laser-pumped incoherent white light source to achieve nanometre-scale resolution at depths up to ~120 µm in highly scattering samples. We also incorporate real-time reference arm adjustment to maintain signal strength and contrast as the focus moves deeper into the sample. Using this system, we imaged fresh ex vivo mouse liver and small intestine with extended depth and detail. In these tissues, the dynamic contrast clearly revealed fine structures not visible with conventional OCT-for example, the sinusoidal microvasculature and organized cell layers in the liver, as well as neural plexuses and crypts in the intestine-all visualized label-free.