Imaging Of Vocal Fold Vibration Research Articles

Preliminary Findings of Vocal Fold Vibratory Characteristics of Singers Analyzed by Laryngeal High-Speed Videoendoscopy

ObjectivesThis study investigates the vocal fold vibratory dynamics of singers, which are postulated to differ from those of normal speakers due to the singers' regular vocal training. The measurement of vocal fold vibration involved the utilization of laryngeal high-speed video endoscopy (LHSV) and subsequent LHSV-based analysis. The focus is to characterize and compare the LHSV-based measures derived from the glottal area waveform (GAW), namely fundamental frequency (F0GAW), glottal perturbation (jitterGAW and shimmerGAW), open quotient (OQGAW), and Nyquist plots, between singers and normal speakers across genders. MethodsParticipants comprised 13 singers from a local cultural and heritage academy and 56 normal speakers from a local university, all were evaluated to have normal voices. Each participant underwent LHSV procedures to capture images of vocal fold vibration, which were subsequently analyzed to generate the LHSV-based measures. ResultsMale singers exhibited lower F0GAW, jitterGAW, shimmerGAW, and OQGAW than female singers. When compared to normal speakers, male singers demonstrated higher F0GAW, and lower jitterGAW and shimmerGAW. No difference in OQGAW was found between male singers and normal speakers. Female singers exhibited lower jitterGAW compared to normal speakers, but no differences were observed in shimmerGAW and OQGAW. The results of Nyquist plots indicated no gender-related associations between types of rim width and among singers. However, for rim pattern, male singers were associated with a higher percentage of clustered rim, suggesting more regular vocal fold vibration, compared to female singers and male normal speakers. ConclusionsSingers, particularly male singers, demonstrate distinct and potentially superior vocal fold vibrations compared to normal speakers, likely attributed to their regular vocal training, resulting in refined vocal fold configurations even during speaking. Despite the limited sample of singers, the study offers valuable insights into the vocal fold vibratory behaviors in singers analyzed using LHSV.

Clinical Practicability of a Newly Developed Real-time Digital Kymographic System

A digital kymogram shows real images of vocal fold vibration. However, DKG is difficult to use in clinical practice because the recorded image cannot be seen instantaneously after examination, as considerable encoding time is required to visualize a digital kymogram. In addition, frame-by frame analysis should be implemented to evaluate high-speed videoendoscopy data, but is time- and labor-intensive. The purpose of the study was to validate the clinical practicability of a real-time multislice digital kymographic system developed by the authors. We analyzed the promptness and accuracy of the examination before and after intracordal injections in patients with unilateral vocal fold paralysis. To assess the clinical applicability of this system, six patients with unilateral vocal fold paralysis were selected. Real-time DKG was performed before and immediately after intracordal injection. We observed changes in the digital kymogram after the intracordal injection. Using this system, 10 scanning lines and up to five vertical pixel row could be obtained in real time, and the maximum acquisition time for the DKG image was 10 seconds. A digital kymogram of the patients could be instantaneously acquired, and whether the intracordal injection was appropriate or not. This article is the first validation study after the development of the real-time multislice digital kymographic system. Our system may be a promising tool in clinical practice for immediate assessment of the vibratory patterns of the vocal cords. More research is necessary for further clinical validation.

Flexible Fiber-Optic High-Speed Imaging of Vocal Fold Vibration: A Preliminary Report

High-speed video (HSV) imaging of vocal fold vibration has been possible only through the rigid endoscope. This study reports that a fiberscope-based high-speed imaging system may allow HSV imaging of naturalistic voicing. Twenty-two subjects were recorded using a commercially available black and white high-speed camera (Photron Motion Tools, 256 × 120 pixel, 2000 frames per second, 8 second acquisition time). The camera gain is set to +6 db. The camera is coupled to a standard fiber-optic laryngoscope (Olympus ENF P-4) with a 300-W Xenon light. Image acquisition was done by asking the subject to perform repeated phonation at modal phonation. Video images were processed using commercial video editing and video noise reduction software (After effects, Magix, and Neat Video 4.1). After video processing, the video images were analyzed using digital kymography (DKG). The HSV black and white video acquired by the camera is gray and lacks contrast. By adjustment of image contrast, brightness, and gamma and using noise reduction software, the flexible laryngoscopy image can be converted to video image files suitable for DKG and waveform analysis. The increased noise still makes edge tracking for objective analysis difficult, but subjective analysis of DKG plot is possible. This is the first report of HSV acquisition in an unsedated patient using a fiberscope. Image enhancement and noise reduction can enhance the HSV to allow extraction of the digital kymogram. Further image enhancement may allow for objective analysis of the vibratory waveform.

On the necessity of using 3D imaging of vocal fold vibration

Physical mechanisms of regular and irregular vocal fold vibration were first studied using a computational model of vocal fold vibration. Later physical mechanisms of vocal fold vibration were studied in laboratory hemilarynx studies, where the medial surface of the vocal folds were imaged. While the method was also extended to clinical studies of vocal vibration, the method exhibited significantly less interpretive power in the clinical applications in which the superior surface of the vocal folds was imaged in 2D. Our hypothesis is that the interpretive power of the method of empirical eigenfunctions in studying the superior surface dynamics of the vocal folds will be significantly increased if one performs 3D imaging of the dynamics versus the standard 2D imaging. To test this hypothesis, the method of empirical eigenfunctions was employed on the same finite element model used in previous computational experiments. Our results confirm the hypothesis that the interpretive power of the method of empirical eigenfunctions was significantly increased in studying the superior surface dynamics of the vocal folds when 3D imaging was employed.

Influence of Embedded Fibers and an Epithelium Layer on the Glottal Closure Pattern in a Physical Vocal Fold Model

PURPOSE The purpose of this study was to explore the possible structural and material property features that may facilitate complete glottal closure in an otherwise isotropic physical vocal fold model. METHOD Seven vocal fold models with different structural features were used in this study. An isotropic model was used as the baseline model, and other models were modified from the baseline model by either embedding fibers aligned along the anterior-posterior direction in the body or cover layer, adding a stiffer outer layer simulating the epithelium layer, or a combination of the 2 features. Phonation tests were performed with both aerodynamic and acoustic measurements and high-speed imaging of vocal fold vibration. RESULTS Compared with the isotropic one-layer model, the presence of a stiffer epithelium layer led to complete glottal closure along the anterior-posterior direction and strong excitation of high-order harmonics in the resulting acoustic spectra. Similar improvements were observed with fibers embedded in the cover layer, but to a lesser degree. The presence of fibers in the body layer did not yield noticeable improvements in glottal closure or harmonic excitation. CONCLUSION This study shows that the presence of collagen and elastin fibers and the epithelium layer may play a critical role in achieving complete glottal closure.

Objective Measures of Laryngeal Imaging: What Have We Learned Since Dr. Paul Moore

Dr. Paul Moore pioneered the use of high-speed cinematography for observation of normal and abnormal vocal fold vibrations during phonation. His analysis of the glottal area waveform, opening and closing speed index, and open quotient from the high-speed films were labor intensive but relevant today. With advances in digital image capture and automated image extraction techniques, stroboscopy and high-speed images of vocal fold vibration may be analyzed with objective measures. Digital high-speed image capture in color is now clinically practical at high resolution. Digital kymography now allows analysis of the vibratory waveform from each vocal fold. Serial capture and comparison can document changes in vibratory function with treatment. Quantification of vocal fold vibration using such techniques is now practical. This is a review of vocal fold vibration capture and analysis techniques since Dr. Moore.

Pediatric high speed digital imaging of vocal fold vibration: A normative pilot study of glottal closure and phase closure characteristics

ObjectiveThe aim of the study is to characterize normal vibratory patterns of both glottal closure and phase closure in the pediatric population with the use of high speed digital imaging. MethodsFor this prospective study a total of 56 pre-pubertal children, 5–11 years (boys=28, girls=28) and 56 adults, 21–45 years (males=28, females=28) without known voice problems were examined with the use of a new technology of high speed digital imaging. Recordings were captured at 4000 frames per second for duration of 4.094s at participants’ typical phonation. With semi-automated software, montage analysis of glottal cycles was performed. Three trained experienced raters, rated features of glottal configuration and phase closure from glottal cycle montages. ResultsPosterior glottal gap was the predominant glottal closure configuration in children (girls=85%, boys=68%) with normal voice. Other glottal configurations observed were: anterior gap (girls=3.6%, boys=0%), complete closure (girls=7%, boys=10%) and hour glass (girls=0%, boys=11%). Adults with normal voice also demonstrated predominantly higher percentage of posterior glottal gap configuration (females=75% male=54%) compared to the configurations of anterior gap (females=0% male=7%), complete closure (females=2% male=39%), hour glass (females=3.6% male=3.6%). A predominantly open phase (51–70% of the glottal cycle) was observed in 86% girls and 71% boys. Compared to children, adult females showed a predominantly balance phased closure 46%, followed by open phase (39%) and predominantly closed phase (14%). Adult males showed a predominantly closed phase (43%), followed by predominantly open phase (39%), followed by a balanced phase (18%). ConclusionsThis is a first study investigating characteristics of normal vibratory motion in children with high speed digital imaging. Glottal configuration and phase closure for children with normal voices are distinctly different compared to adults. The results suggest that posterior glottal gap and a predominantly open phase of the glottal cycle should be considered as normal glottal configuration in children during modal pitch and loudness. This study provides preliminary information on the vibratory characteristics of children with normal voice. The data presented here may provide the bases for differentiating normal vibratory characteristics from the disordered in the pediatric population.

Dynamic B-Mode Ultrasound Imaging of Vocal Fold Vibration During Phonation

We used B-mode imaging to study the vibratory phenomena of the vocal folds. The presence of multilayered structures of the vocal folds in the B-mode image was verified by using freshly excised human larynges in vitro. To capture images of vocal fold vibration, a special treatment was used to reconstruct the aliasing B-mode motion pictures of vocal fold vibration. Echo-particle image velocimetry (Echo-PIV) analysis was then applied to trace the tissue particles in the motion pictures. The vibratory behavior of the body (vocal ligament and muscle) of the vocal folds was revealed. Further analysis showed a quasi-longitudinal wave along the body of the vocal folds in the coronal plane. This is, to the best of our knowledge, the first time that vocal fold vibration physiology has been studied using B-mode imaging and Echo-PIV. (E-mail: tyhsiao@ntu.edu.tw)

電子内視鏡システムを用いた咽喉頭の観察

Electronic videoendoscopy of the pharynx and larynx allows lesions to be visualized with precision. The images obtained using a charge-coupled device (CCD) chip are converted into electric signals and transmitted to the video system center. Clear, dynamic color images are reproduced on a color video monitor through a video system center. The basic components of an electronic videoendoscope system are a flexible endoscope, a video system center, a light source and a color video monitor.There are two methods of capturing and reproducing dynamic color images in electronic videoendoscopy; the single-plate simultaneous color CCD chip method and the single-plate red, green, and blue (RGB) surface scanning method. In the former method, a color CCD chip built into the distal tip of the endoscope contains multiple color pixels and can simultaneously capture different color wavelength of light. In the latter method, the tip of the endoscope incorporates a monochrome CCD chip that can only provide black and white signals. The color CCD chip simplifies color acquisition but is considerably larger than the monochrome CCD chip, requiring a wider diameter than the distal tip of the endoscope. This is one of the reasons why the single-plate RGB surface scanning method is preferred in a rhinolaryngeal electronic videoendoscope system.Digital image processing of lesions can be performed by electronic videoendoscopy. The enhanced color images are superior in quality.Laryngostroboscopy is the most practical method of determining the vibratory pattern of the vocal folds during phonation. However, the laryngostroboscope cannot connect with the electronic videoendoscope system using a single-plate RGB scanning method because of the presence of a rotating wheel filter between the light source and glass fiber bundle of the light guide. To obtain stroboscopic images with an electronic videoendoscope system, a single-plate simultaneous color CCD chip method is necessary.Recent advances in electronic technology enables production of the electronic videoendoscope system that can connect with a laryngostroboscope. The clear stroboscopic images of vocal fold vibration obtained by this system are described here.Literature reviews of the history and development of electronic videoendoscopy were also performed from the perspective of diagnostic usefulness.

Analysis of asymmetric vocal fold vibrations in a finite-element model

Asymmetric vibrations of a finite-element model of the vocal folds were analyzed using the method of empirical eigenfunctions. In a previous study of symmetric vibrations from the model, periodic vibrations yielded two dominant eigenfunctions, which were related to the theoretical normal modes of the model. In a more recent study, the method of empirical eigenfunctions was applied to high-speed endoscopic imaging of vocal fold vibration on human subjects, suggesting several mechanisms of irregular vibration. However, in the in vivo study, the investigation of empirical eigenfunctions was limited to the superior view provided by endoscopy. The results of the present computational study were compared with the in vivo study, while providing additional information regarding vocal fold vibration along the medial surface of the folds. Moreover, the computational study allowed the asymmetric vibrations to be studied systematically as a function of tissue stiffness. [Work supported by Grant No. R29 DC03072 from the National Institute on Deafness and Other Communication Disorders.]

Functional imaging of vocal fold vibration: Digital multislice high-speed kymography

For the diagnosis of voice disorders, and especially for the classification of hoarseness, direct observation of vocal fold vibration is essential. Furthermore, a quantitative description of the movement of the vocal fold becomes increasingly necessary to document and compare findings as well as the progression of speech therapy. On the base of digital high-speed sequences of vocal fold vibration, multiple "functional images"-also called digital kymograms-are obtained using image- and signal-processing algorithms. Digital kymograms can serve as a powerful aid for visualization, description, and classification of vocal fold vibration and as an intermediate step for image interpretation by biomechanical modeling. This visualization technique will be discussed and compared to other techniques currently available: videokymography and videostroboscopy. The technique is applied to several clinical examples: aperiodic processes (phonation onset), irregular vocal fold vibration (paralysis of the recurrent nerve), particular vibration modes (anterior-posterior modes), and running speech.

Imaging of vocal fold vibration by digital multi-plane kymography

Digital multi-plane kymography is presented as a new method to demonstrate vocal fold vibration from digital high-speed recordings. Single lines from digital high-speed sequences of laryngoscopical examinations are concatenated to images, which are called kymograms. In order to reveal anterior–posterior (AP) modes of vibration several kymograms from different location of the glottis can be obtained from a single recording. Problems due to rotation of the endoscope or relative movements of patient or examiner can be solved by image processing algorithms specifically designed for this application. Different types of phonation onset and examples of voice disorders are given.

High-speed digital imaging of vocal fold vibration.

A new method of digitally imaging vocal fold vibration using a solid-state image sensor attached to a conventional camera system is reported. The obtained image signals are stored in an image memory in combination with a personal computer through a high-speed A/D converter. The maximum frame rate for analysis is 4000 fps. After storage of data, images can be reproduced and displayed on a monitor screen as a form of slow-motion display. The system has proved useful for clinical examination of pathological vocal fold vibration.