D. D. Mehta, et al., “Direct measurement and modeling of intraglottal, subglottal, and vocal fold collision pressures during phonation in an individual with a hemilaryngectomy,” Applied Sciences, vol. 11, no. 16, pp. 7256, 2021. Publisher's VersionAbstract
    The purpose of this paper is to report on the first in vivo application of a recently developed transoral, dual-sensor pressure probe that directly measures intraglottal, subglottal, and vocal fold collision pressures during phonation. Synchronous measurement of intraglottal and subglottal pressures was accomplished using two miniature pressure sensors mounted on the end of the probe and inserted transorally in a 78-year-old male who had previously undergone surgical removal of his right vocal fold for treatment of laryngeal cancer. The endoscopist used one hand to position the custom probe against the surgically medialized scar band that replaced the right vocal fold and used the other hand to position a transoral endoscope to record laryngeal high-speed videoendoscopy of the vibrating left vocal fold contacting the pressure probe. Visualization of the larynx during sustained phonation allowed the endoscopist to place the dual-sensor pressure probe such that the proximal sensor was positioned intraglottally and the distal sensor subglottally. The proximal pressure sensor was verified to be in the strike zone of vocal fold collision during phonation when the intraglottal pressure signal exhibited three characteristics: an impulsive peak at the start of the closed phase, a rounded peak during the open phase, and a minimum value around zero immediately preceding the impulsive peak of the subsequent phonatory cycle. Numerical voice production modeling was applied to validate model-based predictions of vocal fold collision pressure using kinematic vocal fold measures. The results successfully demonstrated feasibility of in vivo measurement of vocal fold collision pressure in an individual with a hemilaryngectomy, motivating ongoing data collection that is designed to aid in the development of vocal dose measures that incorporate vocal fold impact collision and stresses.
    D. Mehta, J. B. Kobler, G. Maguluri, J. Park, E. Chang, and N. Iftimia, “Integrating optical coherence tomography with laryngeal videostroboscopy,” Proceedings of the Acoustical Society of America. 2017.Abstract

    Special Session: New trends in imaging for speech production (Speech Communication Technical Committee)

    During clinical voice assessment, laryngologists and speech-language pathologists rely heavily on laryngeal endoscopy with videostroboscopy to evaluate pathology and dysfunction of the vocal folds. The cost effectiveness, ease of use, and synchronized audio and visual feedback provided by videostroboscopic assessment serve to maintain its predominant clinical role in laryngeal imaging. However, significant drawbacks include only two-dimensional spatial imaging and the lack of subsurface morphological information. A novel endoscope will be presented that integrates optical coherence tomography that is spatially and temporally co-registered with laryngeal videoendoscopic technology through a common path probe. Optical coherence tomography is a non-contact, micron-resolution imaging technology that acts as a visual ultrasound that employs a scanning laser to measure reflectance properties at air-tissue and tissue-tissue boundaries. Results obtained from excised larynx experiments demonstrate enhanced visualization of three-dimensional vocal fold tissue kinematics and subsurface morphological changes during phonation. Real-time, calibrated three-dimensional imaging of the mucosal wave and subsurface layered microstructure of vocal fold tissue is expected to benefit in-office evaluation of benign and malignant tissue lesions. Future work calls for the in vivo evaluation of the technology in patients before and after surgical management of these types of lesions.

    M. E. Powell, D. D. Deliyski, R. E. Hillman, S. M. Zeitels, J. A. Burns, and D. D. Mehta, “Comparison of videostroboscopy to stroboscopy derived from high-speed videoendoscopy for evaluating patients with vocal fold mass lesions,” American Journal of Speech-Language Pathology, vol. 25, pp. 576-589, 2016. Publisher's VersionAbstract

    indirect physiological signal to predict the phase of the vocal fold vibratory cycle for sampling. Simulated stroboscopy (SS) extracts the phase of the glottal cycle directly from the changing glottal area in the high-speed videoendoscopy (HSV) image sequence. The purpose of this study is to determine the reliability of SS relative to VS for clinical assessment of vocal fold vibratory function in patients with mass lesions.

    Methods VS and SS recordings were obtained from 28 patients with vocal fold mass lesions before and after phonomicrosurgery and 17 controls who were vocally healthy. Two clinicians rated clinically relevant vocal fold vibratory features using both imaging techniques, indicated their internal level of confidence in the accuracy of their ratings, and provided reasons for low or no confidence.

    Results SS had fewer asynchronous image sequences than VS. Vibratory outcomes were able to be computed for more patients using SS. In addition, raters demonstrated better interrater reliability and reported equal or higher levels of confidence using SS than VS.

    Conclusion Stroboscopic techniques on the basis of extracting the phase directly from the HSV image sequence are more reliable than acoustic-based VS. Findings suggest that SS derived from high-speed videoendoscopy is a promising improvement over current VS systems.

    D. D. Mehta and R. E. Hillman, “Current role of stroboscopy in laryngeal imaging,” Current Opinion in Otolaryngology & Head and Neck Surgery, vol. 20, no. 6, pp. 429-436, 2012. Publisher's VersionAbstract

    PURPOSE OF REVIEW: To summarize recent technological advancements and insight into the role of stroboscopy in laryngeal imaging. RECENT FINDINGS: Although stroboscopic technology has not undergone major technological improvements, recent clarifications have been made to the application of stroboscopic principles to video-based laryngeal imaging. Also recent advances in coupling stroboscopy with high-definition video cameras provide higher spatial resolution of vocal fold vibratory function during phonation. Studies indicate that the interrater reliability of visual stroboscopic assessment varies depending on the laryngeal feature being rated and that only a subset of features may be needed to be representative of an entire assessment. High-speed videoendoscopy (HSV) judgments have been shown to be more sensitive than stroboscopy for evaluating vocal fold phase asymmetry, pointing to the future potential of complementing stroboscopy with alternative imaging modalities in hybrid systems. Laryngeal videostroboscopy alone continues to play a central role in clinical voice assessment. Even though HSV may provide more detailed information about phonatory function, its eventual clinical adoption will depend on how remaining practical, technical, and methodological challenges will be met. SUMMARY: Laryngeal videostroboscopy continues to be the modality of choice for imaging vocal fold vibration, but technological advancements in HSV and associated research findings are driving increased interest in the clinical adoption of HSV to complement videostroboscopic assessment.

    D. D. Mehta and R. E. Hillman, “The evolution of methods for imaging vocal fold phonatory function,” Perspectives on Speech Science and Orofacial Disorders, vol. 22, no. 1, pp. 5-13, 2012. Publisher's VersionAbstract

    In this article, we provide a brief summary of the major technological advances that led to current methods for imaging vocal fold vibration during phonation including the development of indirect laryngoscopy, imaging of rapid motion, fiber optics, and digital image capture. We also provide a brief overview of new emerging technologies that could be used in the future for voice research and clinical voice assessment, including advances in laryngeal high-speed videoendoscopy, depth-kymography, and dynamic optical coherence tomography.

    D. D. Mehta, D. D. Deliyski, and R. E. Hillman, “Commentary on why laryngeal stroboscopy really works: Clarifying misconceptions surrounding Talbot's law and the persistence of vision,” Journal of Speech, Language, and Hearing Research, vol. 53, no. 5, pp. 1263-1267, 2010. Publisher's VersionAbstract

    PURPOSE: The purpose of this article is to clear up misconceptions that have propagated in the clinical voice literature that inappropriately cite Talbot's law (1834) and the theory of persistence of vision as the scientific principles that underlie laryngeal stroboscopy. METHOD: After initial research into Talbot's (1834) original studies, it became clear that his experiments were not designed to explain why stroboscopy works. Subsequently, a comprehensive literature search was conducted for the purpose of investigating the general principles of stroboscopic imaging from primary sources. RESULTS: Talbot made no reference to stroboscopy in designing his experiments, and the notion of persistence of vision is not applicable to stroboscopic motion. Instead, two visual phenomena play critical roles: (a) the flicker-free perception of light and (b) the perception of apparent motion. In addition, the integration of stroboscopy with video-based technology in today's voice clinic requires additional complexities to include synchronization with camera frame rates. CONCLUSIONS: References to Talbot's law and the persistence of vision are not relevant to the generation of stroboscopic images. The critical visual phenomena are the flicker-free perception of light intensity and the perception of apparent motion from sampled images. A complete understanding of how laryngeal stroboscopy works will aid in better interpreting clinical findings during voice assessment.

    D. D. Mehta and R. E. Hillman, “Voice assessment: Updates on perceptual, acoustic, aerodynamic, and endoscopic imaging methods,” Current Opinion in Otolaryngology & Head and Neck Surgery, vol. 16, pp. 211-215, 2008. Publisher's VersionAbstract

    PURPOSE OF REVIEW: This paper describes recent advances in perceptual, acoustic, aerodynamic, and endoscopic imaging methods for assessing voice function. RECENT FINDINGS: We review advances from four major areas. PERCEPTUAL ASSESSMENT: Speech-language pathologists are being encouraged to use the new consensus auditory-perceptual evaluation of voice inventory for auditory-perceptual assessment of voice quality, and recent studies have provided new insights into listener reliability issues that have plagued subjective perceptual judgments of voice quality. ACOUSTIC ASSESSMENT: Progress is being made on the development of algorithms that are more robust for analyzing disordered voices, including the capability to extract voice quality-related measures from running speech segments. AERODYNAMIC ASSESSMENT: New devices for measuring phonation threshold air pressures and air flows have the potential to serve as sensitive indices of glottal phonatory conditions, and recent developments in aeroacoustic theory may provide new insights into laryngeal sound production mechanisms. ENDOSCOPIC IMAGING: The increased light sensitivity of new ultra high-speed color digital video processors is enabling high-quality endoscopic imaging of vocal fold tissue motion at unprecedented image capture rates, which promises to provide new insights into the mechanisms of normal and disordered voice production. SUMMARY: Some of the recent research advances in voice function assessment could be more readily adopted into clinical practice, whereas others will require further development.