Efficacy of Grayscaling Photoglottography Using High-Speed Videolaryngoscopic Images in the Evaluation of Vocal Fold Vibration.

Objectives: Methods for evaluating vocal fold vibration can be divided into indirect methods and directly observed vocal fold vibration. Indirect methods that can monitor the real-time opening and closing movements of the vocal folds include glottal inverse filtering, electroglottography (EGG), and photoglottography (PGG), with near-infrared PGG recently being reported. This study aimed to evaluate the usefulness of grayscaling photoglottography (GSP) to analyze vocal fold vibration. We compared the analysis accuracy of vocal fold oscillatory behavior with EGG and glottal area waveform (GAW).

Study Design: Cross-sectional comparative study METHODS: Participants included 10 normophonic men and 10 normophonic women. Another 10 participants had unilateral vocal fold paralysis, plus one participant each had spasmodic dysphonia, muscle tension dysphonia, and essential vocal tremors. High-speed videolaryngoscopy (HSV) was performed using a high-speed camera capable of recording at 1500 to 2000 frames per second for 10 seconds. Participants were asked to utter the sustained vowel /e/ at low pitch. EGG and voice signals were connected to a PC quirer and measured simultaneously with HSV. Data were analyzed in Praat.

Results: GAW and GSP showed significant differences in voice onset and offset times, but no significant differences were observed in any other parameters. Significant differences were observed in the results for amplitude periodicity, closed quotient, open quotient, speed quotient (SQ), and speed index (SI), and voice onset and offset time between GAW and EGG. Significant differences were found in the results for amplitude periodicity, SQ, SI, and voice onset and offset time between GSP and EGG. GAW exhibited the longest duration. Regarding voice onset and offset time, GAW exhibited the longest duration, followed by GSP and EGG. The only method available to verify the vertical-level difference between the right and left vocal fold was GSP.

Conclusions: We compared the analysis accuracy of GSP with the preexisting methods of GAW and EGG. GSP showed results similar to those of GAW in the evaluation of vocal fold vibration. Additionally, GSP can analyze the vertical-level difference between the right and left vocal fold. GSP could be a useful method for evaluating the vibratory characteristics of the vocal folds.