High-resolution optical Doppler tomography for in vitro and in vivo fluid flow dynamics

Background: The objective of our research was to use a noninvasive tomographic imaging technique with high spatial resolution (2-15 pm) to characterize and monitor fluid flow and the microvasculature in highly scattering biological tissues at user-specified discrete locations. Methods: The technique of optical Doppler tomography (ODT) combines laser Doppler flowmetry (LDF) with optical coherence tomography to obtain high-resolution tomographic velocity and structural images of static and moving constituents in highly scattering biological tissues. We present ODT structural and velocity images using in vitro turbid samples of a circular conduit infused with a suspension of polymer microspheres. At a thin rectangular cross-section of the conduit, the Intralipid flow was measured. Blood flow velocity was measured in vivo in the ear of rodent skin. Results: In first model, the ODT velocity images demonstrated beads near the center of the conduit moving faster than those near the circular wall. In the second model, the ODT velocity images indicated that laminar flow was fastest along the central axis of the conduit. Blood flow in 2 small veins with diameters of 70 and 40 μm, respectively, and an artery with diameter of 25 μm, was clearly identified in a rodent model. Conclusion: In our preliminary in vitro and in vivo studies on turbid samples and model vasculatures, we determined that the application of ODT to characterize and image blood flow with high spatial resolution at discrete user-specified locations in highly scattering biological tissues is feasible.