Abstract
Microscale quantification of cilia-driven fluid flow is an emerging area in medical physiology, including pulmonary and central nervous system physiology. Cilia-driven fluid flow is most completely described by a three-dimensional, three-component (3D3C) vector field. Here, we generate 3D3C velocimetry measurements by synthesizing higher dimensional data from lower dimensional measurements obtained using two separate optical coherence tomography (OCT)-based approaches: digital particle image velocimetry (DPIV) and dynamic light scattering (DLS)-OCT. Building on previous work, we first demonstrate directional DLS-OCT for 1D2C velocimetry measurements in the sub-1 mm/s regime (sub-2.5 inch/minute regime) of cilia-driven fluid flow in Xenopus epithelium, an important animal model of the ciliated respiratory tract. We then extend our analysis toward 3D3C measurements in Xenopus using both DLS-OCT and DPIV. We demonstrate the use of DPIV-based approaches towards flow imaging of Xenopus cerebrospinal fluid and mouse trachea, two other important ciliary systems. Both of these flows typically fall in the sub-100 μm/s regime (sub-0.25 inch/minute regime). Lastly, we develop a framework for optimizing the signal-to-noise ratio of 3D3C flow velocity measurements synthesized from 2D2C measures in non-orthogonal planes. In all, 3D3C OCT-based velocimetry has the potential to comprehensively characterize the flow performance of biological ciliated surfaces.
Highlights
Cilia driven-fluid flow is an important physiological process in numerous organ systems
Ciliary flow is responsible for clearance of mucus from the respiratory tract, movement of cerebrospinal fluid (CSF) in the ventricles of the brain, determination of left-right patterning in the embryonic node, and movement of ova in the Fallopian tubes [1]
We will focus on an autocorrelation-based technique we previously demonstrated, directional dynamic light scattering (DLS)-optical coherence tomography (OCT) [11], as well as a related cross-correlation based technique, digital particle image velocimetry (DPIV)
Summary
Cilia driven-fluid flow is an important physiological process in numerous organ systems. Because ciliary flow results from the shearing action of many cilia along a complex geometrical surface, ciliary flow lacks certain symmetries, such as unidirectionality and axisymmetry [2,3,4]. While these symmetries can simplify the quantification and analysis of other types of flow, such as Poiseuille flow in arteries, they are typically not applicable in the context of cilia-driven fluid flow. For a steady-state flow field described in three spatial dimensions, the fluid motion at each location in three-dimensional space is described by a three-component vector
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