Objective: Voice disorders are commonly diagnosed in the outpatient setting using laryngeal videostroboscopy. While this method provides qualitative diagnostic information, it is limited to surface visualization of the layered vocal fold tissue and 3-D mucosal wave. Cross-sectional imaging can provide additional information on vocal fold pathologies, therapeutic efficacy, and offer insights into the function of the vocal folds. Our goal was to create an optical coherence tomography (OCT) laryngoscope for the outpatient clinic and demonstrate a strategy for cross-sectional imaging of the vocal folds and glottal cycle in awake subjects.
Methods: While OCT has been investigated to address the shortcomings of standard 2-D endoscopy, challenges remain in capturing the glottal cycle over the human fundamental frequency range. We have developed a fast-scanning OCT laryngoscope capable of asynchronous Nyquist sampling of the fundamental frequency range (up to 510 Hz). The OCT laryngoscope was designed for rigid, transoral endoscopy with a 3-D printed body for hand-held operation. A clinical endoscopy camera was coupled to the laryngoscope to provide coaxial imaging and navigation. A reconstruction algorithm was also designed to improve representation of the glottal cycle. Detailed local reconstructions of the glottal cycle in the coronal plane are created by combining frames (n=20) from several consecutive glottal cycles. Glottal phase variation within OCT frames was corrected to represent the left and right vocal fold at the same phase. The algorithm was validated using a vibrating phantom. To test the feasibility of our strategy in the voice clinic, healthy volunteers were imaged during sustained vowel production (/i/) and the glottal cycle reconstructed.
Results/Conclusion: Cross-sectional imaging of the vocal fold during phonation was achieved by increasing the scan rate of a hand-held OCT laryngoscope and implementing an algorithm to improve sampling of the vocal fold vibration. Reconstruction of the vocal fold cycle from awake, phonating volunteers is presented. The developed technology enables quantitative functional assessment of the superficial vocal fold layers. Use of OCT in the voice clinic has potential to improve diagnosis of vocal fold pathologies as well as the understanding of voice mechanisms and therapies.