Spatiotemporal analysis of normal and pathological human vocal fold vibrations.

PURPOSE: For spatiotemporal analysis to become a relevant clinical tool, it must be applied to human vocal fold vibration. Receiver operating characteristic (ROC) analysis will help assess the ability of spatiotemporal parameters to detect pathological vibration. MATERIALS AND METHODS: Spatiotemporal parameters of correlation length and entropy were extracted from high-speed videos of 124 subjects, 67 without vocal fold pathology and 57 with either vocal fold polyps or nodules. Mann-Whitney rank sum tests were performed to compare normal vocal fold vibrations to pathological vibrations, and ROC analysis was used to assess the diagnostic value of spatiotemporal analysis. RESULTS: A statistically significant difference was found between the normal and pathological groups in both correlation length (P < .001) and entropy (P < .001). The ROC analysis showed an area under the curve of 0.85 for correlation length, 0.87 for entropy, and 0.92 when the 2 parameters were combined. A statistically significant difference was not found between the nodules and polyps groups in either correlation length (P = .227) or entropy (P = .943). The ROC analysis showed an area under the curve of 0.63 for correlation length and 0.51 for entropy. CONCLUSIONS: Although they could not effectively distinguish vibration of vocal folds with nodules from those with polyps, the spatiotemporal parameters correlation length and entropy exhibit the ability to differentiate normal and pathological vocal fold vibration and may represent a diagnostic tool for objectively detecting abnormal vibration in the future, especially in neurological voice disorders and vocal folds without a visible lesion.

Typing vocal fold vibratory patterns in excised larynx experiments via digital kymography.

OBJECTIVES: Signal typing is central to the understanding of vocal fold vibratory patterns. Digital kymography (DKG) allows the direct observation of vocal fold vibratory patterns, and therefore, using DKG for vibratory signal typing may provide a useful complement to traditional signal typing techniques. METHODS: Video data collected from 20 larynges excised from mongrel dogs were observed with DKG in order to find examples of type 1 (nearly periodic), type 2 (subharmonic), and type 3 (aperiodic) vibratory patterns. The time series, frequency spectra, and correlation dimensions were calculated for each signal type. RESULTS: The type 1 pattern showed a periodic time series of glottal edges and a discrete frequency spectrum. The type 2 vibratory pattern displayed a time series of alternating high- and low-amplitude waves and a frequency spectrum that included a subharmonic (F0/2) frequency component. Regular and symmetric vibratory patterns were observed in the type 1 and type 2 patterns. The type 3 vibratory pattern was characterized by an aperiodic time series of glottal edges, a broadband frequency spectrum, and irregular and asymmetric vibratory patterns. The correlation dimension estimates increased from type 1 to type 2 to type 3. CONCLUSIONS: Imaging with DKG demonstrated an ability to assign a signal type to various laryngeal vibrations. Signal typing techniques utilizing direct observation of the vocal folds could be useful in determining valid methods for the analysis of vocal fold vibrations.

Effect of vocal fold injury location on vibratory parameters in excised canine larynges.

OBJECTIVE: To investigate the effect of vocal fold injury location on vibratory amplitude and lateral phase difference. STUDY DESIGN: Repeated measures with each excised canine larynx serving as own control. SETTING: Basic science study conducted in university laboratory. METHODS: Vocal fold vibration of excised canine larynges was recorded with a high-speed camera before and after inducing vocal fold injury at 1 of 5 locations: anterior, middle, posterior, medial, or superior. Medial and superior injuries were created within the middle third of the vocal fold. Five larynges were used for each of the 5 injury locations. Kymography was performed at the midpoint of the vocal folds for each video. Pre- and postinjury vibratory amplitude and lateral phase difference were compared for each location. RESULTS: The anterior and medial injuries produced consistent decreases in vibratory amplitude. Middle and posterior injuries might slightly decrease amplitude. Superior injuries seemed to have no effect on amplitude. Anterior and medial injuries induced phase asymmetry between the right and left vocal folds. Middle injuries appeared to affect phase difference slightly, whereas posterior and superior injuries had no effect. CONCLUSION: Injury to the anterior or medial portions of the vocal fold may be most likely to cause abnormal vocal fold vibration. Using caution in these locations during phonosurgery may favor superior postoperative vocal outcomes.

Kymographic characterization of vibration in human vocal folds with nodules and polyps.

OBJECTIVES/HYPOTHESIS: Digital kymography (DKG) can provide objective quantitative data about vocal fold vibration, which may help distinguish normal from pathological vocal folds as well as nodules from polyps. STUDY DESIGN: Case-control study. METHODS: There were 87 subjects who were separated into three groups: control, nodules, and unilateral polyps, and examined using a high-speed camera attached to an endoscope. Videos were analyzed using a custom MATLAB program, and three DKG line-scan positions (25%, 50%, and 75% of vocal fold length) were used in statistical analyses to compare vocal fold vibrational frequency, amplitude symmetry index (ASI), amplitude order, and vertical and lateral phase difference (VPD and LPD, respectively). RESULTS: Significant differences among groups were found in all vibrational parameters except frequency. Polyps and nodules groups exhibited greater ASI values (less amplitude symmetry) than the control group. Although the control group consistently showed its largest amplitudes at the midline, the polyps group showed larger amplitudes toward the posterior end of the vocal folds. A significant anterior-posterior pattern in amplitude was not found in the nodules group. LPD values were usually largest (most symmetrical) in the control group, followed by nodules and polyps. LPD at the 25% position allowed for differentiation between polyp and nodule groups. The largest VPD (more pronounced mucosal wave) values were usually found in the control group. CONCLUSIONS: Vibratory characteristics of normal and pathological vocal folds were quantitatively examined and compared using multiline DKG. These findings may allow for better characterization of pathologies and eventually assist in improving the clinical utility of DKG.

Quantitative study of vibrational symmetry of injured vocal folds via digital kymography in excised canine larynges.

PURPOSE: Digital kymography and vocal fold curve fitting are blended with detailed symmetry analysis of kymograms to provide a comprehensive characterization of the vibratory properties of injured vocal folds. METHOD: Vocal fold vibration of 12 excised canine larynges was recorded under uninjured, unilaterally injured, and bilaterally injured conditions. Kymograms were created at 25%, 50%, and 75% of the vocal fold length, and vibratory parameters were compared quantitatively among conditions and were studied with respect to right-left and anterior-posterior symmetries. RESULTS: Anterior-posterior amplitude asymmetry was found in the bilateral condition. The unilateral condition showed significant right-left amplitude asymmetry, and it showed the lowest right-left phase symmetry among the conditions. In condition comparisons, vertical phase difference did not show significant differences among conditions, whereas amplitudes were significantly different among conditions at all line scan positions and most vocal fold lips. Significant differences in frequency were found among the conditions at all 4 vocal fold lips, with the bilateral condition exhibiting the greatest frequency. CONCLUSION: Digital kymography and curve fitting provide detailed information about the vibratory behavior of injured vocal folds. Awareness of vibratory properties associated with vocal fold injury may aid in diagnosis, and the quantitative abilities of digital kymography may allow for objective treatment selection.

Mucosal wave measurement and visualization techniques.

Organized vibration of the vocal folds is critical for high-quality voice production. When the vocal folds oscillate, the superficial tissue of the vocal fold is displaced in a wave-like fashion, creating the so-called "mucosal wave." Because the mucosal wave is dependent on vocal fold structure, physical alterations of that structure cause mucosal wave abnormalities. Visualization and quantification of mucosal wave properties have become useful parameters in diagnosing and managing vocal fold pathology. Mucosal wave measurement provides information about vocal fold characteristics that cannot be determined with other assessment techniques. Here, we discuss the benefits, disadvantages, and clinical applicability of the different mucosal wave measurement techniques, such as electroglottography, photoglottography, and ultrasound and visualization techniques that include videokymography, stroboscopy, and high-speed digital imaging. The various techniques and their specific uses are reviewed with the intention of helping researchers and clinicians choose a method for a given situation and understand its limitations and its potential applications. Recent applications of these techniques for quantitative assessment demonstrate that additional research must be conducted to realize the full potential of these tools. Evaluations of existing research and recommendations for future research are given to promote both the quantitative study of the mucosal wave through accurate and standardized measurement of mucosal wave parameters and the development of reliable methods with which physicians can diagnose vocal disorders.