A Low-Cost Method of Ciliary Beat Frequency Measurement Using iPhone and MATLAB: Rabbit Study

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.