High-Resolution Dynamic Full-Field Optical Coherence Microscopy: Illuminating Intracellular Activity in Deep Tissue

Abstract: 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 struggle to image deep within highly scattering tissues at high resolution. Here, we present a new high-resolution d-FF-OCM system that overcomes these limitations, enabling much deeper high-resolution imaging in such tissues. The setup uses 100x oil-immersion objectives (NA = 1.25) and a high-brightness, laser-pumped incoherent white light source to achieve nanometer-scale resolution at depths up to approximately 100 micrometers 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 unprecedented 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. By bridging the gap between high-resolution and deep imaging in highly scattering tissue, this advance provides a powerful new tool for biological microscopy, with potential applications from fundamental research to rapid intraoperative pathology.