ABSTRACT
OBJECTIVES: (1) To determine ciliary beat frequency (CBF) using a consumer-grade cellphone camera and MATLAB and (2) to evaluate the effectiveness and accuracy of the proposed method. STUDY DESIGN: Prospective animal study. SETTING: Academic otolaryngology department research laboratory. METHODS: Five ex vivo tracheal samples were extracted from 3 freshly euthanized (<3 hours postmortem) New Zealand white rabbits and incubated for 30 minutes in buffer at 23°C, buffer at 37°C, or 10% formalin at 23°C. Samples were sectioned transversely and observed under a phase-contrast microscope. Cilia movement was recorded through the eyepiece using an iPhone 6 at 240 frames per second (fps). Through MATLAB programming, the video of the 23°C sample was downsampled to 120, 60, and 30 fps, and Fourier analysis was performed on videos of all frame rates and conditions to determine CBF. CBF of the 23°C sample was also calculated manually frame by frame for verification. RESULTS: Recorded at 240 fps, the CBF at 23°C was 5.03 ± 0.4 Hz, and the CBF at 37°C was 9.08 ± 0.49 Hz (P < .001). The sample with 10% formalin did not display any data beyond DC noise. Compared with 240 fps, the means of other frame rates/methods (120, 60, 30 fps; manual counting) at 23°C all showed no statistical difference (P > .05). CONCLUSION: There is no significant difference between CBF measured via visual inspection and that analyzed by the developed program. Furthermore, all tested acquisition rates are shown to be effective, providing a fast and inexpensive alternative to current CBF measurement protocols.
Subject(s)
Cell Phone , Cilia/physiology , Mucociliary Clearance/physiology , Software , Trachea/ultrastructure , Animals , In Vitro Techniques , Prospective Studies , Rabbits , Video RecordingABSTRACT
BACKGROUND: Measuring ciliary beat frequency (CBF) is a technical challenge and difficult to perform in vivo. Doppler optical coherence tomography (D-OCT) is a mesoscopic noncontact imaging modality that provides high-resolution tomographic images and detects micromotion simultaneously in living tissues. In this work we used D-OCT to measure CBF in ex vivo tissue as the first step toward translating this technology to clinical use. METHODS: Fresh ex vivo samples of rabbit tracheal mucosa were imaged using both D-OCT and phase-contrast microscopy (n = 5). The D-OCT system was designed and built to specification in our lab (1310-nm swept source vertical-cavity surface-emitting laser [VCSEL], 6-µm axial resolution). The samples were placed in culture and incubated at 37°C. A fast Fourier transform was performed on the D-OCT signal recorded on the surface of the samples to gauge CBF. High-speed digital video of the epithelium recorded via phase-contrast microscopy was analyzed to confirm the CBF measurements. RESULTS: The D-OCT system detected Doppler signal at the epithelial layer of ex vivo rabbit tracheal samples suggestive of ciliary motion. CBF was measured at 9.36 ± 1.22 Hz using D-OCT and 9.08 ± 0.48 Hz using phase-contrast microscopy. No significant differences were found between the 2 methods (p > 0.05). CONCLUSION: D-OCT allows for the quantitative measurement of CBF without the need to resolve individual cilia. Furthermore, D-OCT technology can be incorporated into endoscopic platforms that allow clinicians to readily measure CBF in the office and provide a direct measurement of mucosal health.
