In vivo multicontrast and tissue-activity imaging of zebrafish by label-free optical coherence tomography

Zebrafish is an essential model organism for biological study with competitive advantages over mammalian models. In this study, OCT and its contrast-extensions were utilized to make OCT sensitive to more than the tissue structure of zebrafish. The contrast-extensions include polarization-sensitive OCT (PS-OCT), OCT angiography (OCTA), and dynamic OCT (DOCT), which provided a comprehensive multi-contrast assessment of the in-vivo zebrafish microstructures and their functional activity. A 1.3-μm Jones matrix swept source OCT system is used in this study. Two scanning protocols have been utilized for measuring adult zebrafish. One is a raster scanning with repeated 4 frames at each B-scan location in 51.2 ms. It is mainly used for OCTA and PS-OCT reconstruction. The other is repeated raster scanning which scans each B-scan location 32 times in 6.55 s and is used for DOCT reconstruction. The characteristic anatomical were visualized. The dark stripes exhibited high Logarithmic Intensity Variance (LIV), which may relate to the intracellular activities of melanin-containing pigment cells so-called melanophores at the dark stripe. In addition, the spinal cord exhibited high LIV signals, and blood vessels around the spine appeared high OCTA and LIV signal, which may indicate the neuron activities and blood flow of the zebrafish, respectively.