Fig. 4: In vivo vascular dynamics revealed by FWMOT. Oxygen challenge experiment and dye injection monitoring in the central vein and artery in the mouse ear using FWMOT imaging.

a The OA images in the blue wavelengths, showing oxygenated (red) and de-oxygenated (green) vessels. We performed continuously B-Scans on the blue region denoted in a and ‘i’ shows such a cross-section. The green arrow and region in ‘i’ indicate the selected vein, and the red arrow and region indicate the selected artery. Green is 445 nm, red is 465 nm, scale bar 1 mm. b The changes in the ratio between the OA signal intensity in wavelength 2 (S₂) to that of wavelength 1 (S₁) in time during an oxygen stress test. The oxygen saturation is proportional to the ratio S₂/S₁. The oxygen saturation changes faster in the artery than in the vein, as expected. c The oxygen extraction rate during the same experiment. d The signal intensity at wavelengths 3 and 4 (S₃ and S₄ respectively) at the same artery and vein indicated in a during intravascular injection of the two dyes, Evan’s Blue and ICG. In both cases the signal intensity increases first in the artery and later in the vein. These experiments were repeated three time independently with similar results.