The recommended protocols for instrumental assessment of voice using laryngeal endoscopic imaging, acoustic, and aerodynamic methods will enable clinicians and researchers to collect a uniform set of valid and reliable measures that can be compared across assessments, clients, and facilities.
High-speed videoendoscopy (HSV) captures the true intracycle vibratory behavior of the vocal folds, which allows for overcoming the limitations of videostroboscopy for more accurate objective quantification methods. However, the commercial HSV systems have not gained widespread clinical adoption because of remaining technical and methodological limitations and an associated lack of information regarding the validity, practicality, and clinical relevance of HSV. The purpose of this article is to summarize the practical, technological and methodological challenges we have faced, to delineate the advances we have made, and to share our current vision of the necessary steps towards developing HSV into a robust tool. This tool will provide further insights into the biomechanics of laryngeal sound production, as well as enable more accurate functional assessment of the pathophysiology of voice disorders leading to refinements in the diagnosis and management of vocal fold pathology. The original contributions of this paper are the descriptions of our color high-resolution HSV integration, the methods for facilitative playback and HSV dynamic segmentation, and the ongoing efforts for implementing HSV in phonomicrosurgery, as well as the analysis of the challenges and prospects for the clinical implementation of HSV, additionally supported by references to previously reported data.
Purpose-The purpose of this study was to ascertain the amount of phase asymmetry of the vocal fold vibration in normophonic speakers via visualization techniques and compare findings for habitual and pressed phonations.Method-Fifty-two normophonic speakers underwent stroboscopy and high-speed videoendoscopy (HSV). The HSV images were further processed into four visual displays: HSV playbacks, digital kymography (DKG) playbacks, mucosal wave kymography playbacks and static kymographic images of the medial line from the DKG playback. Two types of phase asymmetries, left-right and anterior-posterior, were rated on a scale from 1 to 5. Objective measures of left-right phase asymmetry were obtained.Results-The majority of normophonic speakers (81%) were noted to display anterior-posterior asymmetry; however 66% of those were characterized as mild. Seventy-nine percent of participants were noted to display left-right asymmetry, however 72% of those were mild. A moderate relationship between the objective measures and subjective ratings was found.Conclusions-Most normophonic speakers exhibit mild left-right and anterior-posterior asymmetries for both habitual and pressed phonations. Asymmetries were noted more often during habitual than pressed phonations, and when visualized by HSV and kymography than stroboscopy. Differences between objective measures and visual judgments support the need to quantify vocal fold vibratory features.
Purpose
In prior work, a manually derived measure of vocal fold vibratory phase asymmetry correlated to varying degrees with visual judgments made from laryngeal high-speed videoendoscopy (HSV) recordings. The current investigation extended upon this work by establishing an automated HSV-based framework to quantify three categories of vocal fold vibratory asymmetry.
Method
HSV-based analysis provided for cycle-to-cycle estimates of left-right phase asymmetry, left-right amplitude asymmetry, and axis shift during glottal closure for 52 normal speakers producing comfortable and pressed phonation. An initial cross validation of the automated left-right phase asymmetry measure was performed by correlating the measure with other objective and subjective assessments of phase asymmetry.
Results
Vocal fold vibratory asymmetry was exhibited to a similar extent in both comfortable and pressed phonations. The automated measure of left-right phase asymmetry strongly correlated with manually derived measures and moderately correlated with visual-perceptual ratings. Correlations with the visual-perceptual ratings remained relatively consistent as the automated measure was derived from kymograms taken at different glottal locations.
Conclusions
An automated HSV-based framework for the quantification of vocal fold vibratory asymmetry was developed and initially validated. This framework serves as a platform for investigating relationships between vocal fold tissue motion and acoustic measures of voice function.
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