Mesoscopic oblique plane microscopy via light-sheet mirroring

Understanding the intricate interplay and inter-connectivity of biological processes across an entire organism is important in various fields of biology, including cardiovascular research, neuroscience, and developmental biology. Here, we present a mesoscopic oblique plane microscope (OPM) that enables whole organism imaging with high speed while revealing fine details such as endothelial nuclei. A microprism underneath the sample enhances the axial resolution and optical sectioning through total internal reflection of the light sheet. Through rapid refocusing of the light sheet, the imaging depth is extended up to threefold while keeping the axial resolution constant. Using low magnification objectives with a large field of view, we realize mesoscopic imaging over a volume of 3.7 mm × 1.5 mm × 1 mm with ∼2.3 µm lateral and ∼9.2 µm axial resolution. Applying the mesoscopic OPM, we demonstrate in vivo and in toto whole organism imaging of the zebrafish vasculature and its endothelial nuclei, and blood flow dynamics at 12 Hz acquisition rate, resulting in a quantitative map of blood flow across the entire organism.