Biomed. Opt. Express 3, 1978–1992 (2012)

Amy Oldenburg and colleagues from University of North Carolina at Chapel Hill in the United States have demonstrated that optical coherence tomography can be used to monitor the activity of cilia and mucus flow in the mammalian airway. Using an in vitro human airway model and ex vivo mouse tracheas, they have used cross-correlation measurements to quantify the flow of thick mucus directly. They also showed that optical coherence tomography with an axial resolution of ∼3 μm can image the layer of fine, hair-like cilia (∼7 μm in length) that line the airway and beat in a coordinated fashion to transport mucus. With the use of a sufficiently high frequency rate (>3.3 Hz) for variance contrast imaging, ciliary activity could be visualized underneath a thick and turbid mucus layer. The researchers predict that their methods will result in new applications for optical coherence tomography, which is already popular in studies of the retina. In particular, the scheme could be useful for examining changes that occur in the human respiratory system as a result of conditions such as cystic fibrosis and chronic obstructive pulmonary disease.