Fig. 4: Flexible imaging of biodynamics in vivo along the rectangular window of a mouse spinal cord with a curved surface.

a, Photograph of the exposed mouse spinal cord, with the width (W) and length (L) dimensions of the FOV. R, rostral side; C, caudal side. b, The strategy of multi-plane imaging to match the curved surface. Here, four planes at different focal depths are set, which correspond to four sub-FOVs along the spinal cord. c, Single-plane (top, as in conventional microscopes) and multi-plane (bottom) imaging of the mouse spinal cord in vivo, where the blood plasma is stained with FITC–dextran (fluorescein isothiocyanate–dextran). Each image is normalized to the mean intensity (mean(I)) of the corresponding whole FOV. The lower left insets show the Fourier transform (FT) spectra of the whole FOV images (on a log scale), where the dashed white circle denotes the 0.02% strength of the zero frequency. The focal depths of the four planes are labelled alongside the green spots in the bottom image. Scale bar, 500 μm. d, Expanded views of the regions highlighted by the dashed boxes in c. Scale bar, 50 μm. e, High-speed imaging of neutrophil trafficking along blood vessels in the mouse spinal cord in vivo. Whole FOV, 1.7 × 6.5 mm; frame rate, 3.3 Hz. Examples of neutrophil traces are denoted on the temporally averaged grayscale background. Neutrophils move along the traces in the direction marked by the dot, and the moving velocities are colour-coded. The inset shows the geometry of the dorsal venous system. Scale bar, 500 μm. f, Two representative traces of neutrophil trafficking, with red arrows denoting the moving directions. Scale bar, 500 μm. g, Expanded views of the neutrophils at different timestamps in traces 2 and 7, arranged in respective rows. The arrows denote moving directions. The image intensity is normalized to the minimum–maximum range in each timestamp. Scale bar, 50 μm.