Clinical measurement of mucosal wave velocity using simultaneous photoglottography and laryngostroboscopy

Near-infrared photoglottography for measuring multiple glottal events

Near-infrared (NIR) photoglottography (PGG) is a non-invasive method for monitoring glottal activities which retains functionality of conventional PGG using visible light with more convenient accessibility. This paper is to investigate its performance in comparison with simultaneously recorded electroglottography (EGG) signals. Results showed that NIR PGG detects continuous transillumination for glottal aperture and vocal-fold contact. Glottal timing markers known as glottal closure and opening instants are detectable agreeing to the corresponding EGG-based instants. Further, it was inferred that variations of glottal waveforms based on NIR PGG reflect vertical vocal-fold edge motions.

Study of spatiotemporal liquid dynamics in a vibrating vocal fold by using a self-oscillating poroelastic model

The main purpose of this study is to investigate the spatiotemporal interstitial fluid dynamics in a vibrating vocal fold. A self-oscillating poroelastic model is proposed to study the liquid dynamics in the vibrating vocal folds by treating the vocal fold tissue as a transversally isotropic, fluid-saturated, porous material. Rich spatiotemporal liquid dynamics have been found. Specifically, in the vertical direction, the liquid is transported from the inferior side to the superior side due to the propagation of the mucosal wave. In the longitudinal direction, the liquid accumulates at the anterior-posterior midpoint. However, the contact between the two vocal folds forces the accumulated liquid out laterally in a very short time span. These findings could be helpful for exploring etiology of some laryngeal pathologies, optimizing laryngeal disease treatment, and understanding hemodynamics in the vocal folds.

Laser-Calibrated System for Transnasal Fiberoptic Laryngeal High-Speed Videoendoscopy

The design specifications and experimental characteristics of a newly developed laser-projection transnasal flexible endoscope coupled with a high-speed videoendoscopy system are provided. The hardware and software design of the proposed system benefits from the combination of structured green light projection and laser triangulation techniques, which provide the capability of calibrated absolute measurements of the laryngeal structures along the horizontal and vertical planes during phonation. Visual inspection of in vivo acquired images demonstrated sharp contrast between laser points and background, confirming successful design of the system. Objective analyses were carried out for assessing the irradiance of the system and the penetration of the green laser light into the red and blue channels in the recorded images. The analysis showed that the system has irradiance of 372 W/m² at a working distance of 20 mm, which is well within the safety limits, indicating minimal risk of usage of the device on human subjects. Additionally, the color penetration analysis showed that, with probability of 90%, the ratio of contamination of the red channel from the green laser light is less than 0.002. This indicates minimal effect of the laser projection on the measurements performed on the red data channel, making the system applicable for calibrated 3D spatial-temporal segmentation and data-driven subject-specific modeling, which is important for further advancing voice science and clinical voice assessment.

Development of laser ruler in rigid laryngoscope

OBJECTIVES

The objective of this study was to develop a new device that provides a simple, noninvasive method of measuring accurate lesion size while using an endoscope.

METHODS

We developed a rigid laryngoscope with a built-in laser-ruler using a one-light emitting diode and an acrylic plate. The invention incorporates a built-in laser diode that projects an auto-parallel beam into the optical path of the rigid laryngoscope to form two spots in the field of view.

RESULTS

While the interspot distance remains consistent despite changes in focal plane, magnification, or viewing angle of the laryngoscope, projection to an uneven surface introduces certain variations in the shape, and size of the spots, and the distance between the two spots.

CONCLUSION

The device enables a laryngologist to easily measure the distance between landmarks, as well as the change in real size, and the progressive change of vocal fold lesions in an outpatient setting.

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.

Characterization of lamina propria and vocal muscle in human vocal fold tissue by ultrasound Nakagami imaging

PURPOSE

A number of ultrasound techniques have been applied to identify the biomechanical properties of the vocal folds. These conventional ultrasound methods, however, are not capable of visually mapping the concentration of collagen and elastic fibers in the vocal folds in the form of a parametric image. This study proposes to use a statistical parameter, the Nakagami factor estimated from the statistical distribution of the ultrasonic signals backscattered from tissues, as a means for parametric imaging of the biomechanical properties of the vocal folds.

METHODS

The ultrasonic backscattered signals were acquired from four larynges (eight vocal folds) obtained from individuals without vocal fold pathology for constructing the Nakagami images. The textures of the Nakagami image in the lamina propria (LP) and the vocal muscle (VM) were observed and compared. The average and standard deviation of the Nakagami parameter for the LP and the VM were also calculated.

RESULTS

The results showed that the Nakagami parameter of the LP is larger than that of the VM. Moreover, the LP and the VM have different shading features in the Nakagami images. It was found that the Nakagami parameter may depend on the concentration of collagen and elastic fibers, demonstrating that the Nakagami imaging may allow visual differentiation between the LP and the VM in the vocal folds.

CONCLUSIONS

Current preliminary results suggested that the high-frequency Nakagami imaging may allow real-time visual characterization of the vocal fold tissues in clinical routine examinations.

Real-time, high-resolution ultrasonography of the vocal folds--a prospective pilot study in patients before and after thyroidectomy

PURPOSE

The aim of the study was to evaluate the functionality of vocal folds (VF) by real-time, high-resolution ultrasonography (US) and to correlate the imaged features to results of laryngological examination (LE).

METHODS

The study group comprised 50 patients (41 females and nine males), qualified to thyroidectomy. All the patients had LE and US examination before and 2 days, 2 months, and 3 months after the surgery. We used high-resolution US imaging to identify VFs and, subsequently, a pulsed Doppler and Doppler gate to quantify the tissue displacement velocity in the vibrating VF section.

RESULTS

LE revealed unilateral VF paralysis in two patients. VF dysfunction was diagnosed in other four subjects. In simultaneously performed US examination, changes in VF displacement velocity (VFDV) were observed in ten patients. In two subjects, VFDV was below 30 cm/s- patients with VF paralysis, diagnosed in LE. In a further eight cases, we observed VFDV decrease by 50%, comparing to preoperative values. Both US-imaging and LE, performed after the 3-month follow-up, confirmed the transitional character of the above-mentioned pathologies.

CONCLUSIONS

US imaging of the VFs correlated with LE results, while being a minimally invasive, easily reproducible, and inexpensive method of examining VF functionality. Thanks to many recording options, it may soon become a perfect tool for an early identification of postoperative VF dysfunction with its later monitoring. To our knowledge, it is the first application of US and Doppler gate modes for VFDF quantification; however, an analysis on a larger group of patients is necessary to standardize the technique.

Acoustic Changes Related to Laryngeal Examination with a Rigid Telescope

The influence on voice quality of the insertion of endoscopic equipment with tongue anchoring and head position requirements during endoscopic evaluation has not been fully investigated. The present study attempted to examine the influence of: (1) the presence of a rigid endoscope and tongue anchoring, and (2) the angle of position technique (70-degree and 90-degree) on participants' vocal output during sustained production of the vowel /i/. Five acoustic measurements including fundamental frequency (F0) values, percent jitter values, relative average perturbation of F0 shimmer, and noise-to-harmonic ratios were used to represent participants' voice quality. Results indicated that F0 values were significantly influenced by the angle of sitting position, while percent jitter values, relative average perturbation of F0, shimmer, and noise- to-harmonic ratios were affected by the presence of a rigid endoscope and tongue anchoring.

Geschwindigkeitsmessung der Stimmlippenbewegung

INTRODUCTION

Clinical examinations with short-interval, color-filtered double-flash stroboscopy enable us to estimate the movements of the vocal fold edges during phonation. So-called 'displacement bands' show the degree of the vibratory amplitude in these images. Using the two-point light projection method the displacement bands can be measured with very high accuracy. A combination of these two methods was used for velocity measurements of the vocal fold movements within the phonatory cycle. The aim of the study was to explore the influence of change in sound pressure level (SPL) and fundamental frequency (F0) on the velocity of the horizontal amplitude of the vocal folds during phonation.

MATERIAL AND METHODS

40 healthy volunteers (31 women, 9 men, average age 24.8 years) were examined. During the special videostroboscopy with short-interval, color-filtered double flashes laser spots were projected onto the vocal folds by an endoscopic two-point light projection device. The subjects had to change their SPL and F0 following a test protocol. During phonation they had to produce tones in low, middle and high chest voice as well as in falsetto register. Each subject was asked to do this in a soft, a modal, a loud and a very loud manner. Images of the phonatory cycle showing the vocal folds immediately before collision were measured separately at three different positions. About 15,000 single measurements were evaluated.

RESULTS

The measured velocity of the horizontal amplitude during the closing phase of the vocal folds in chest voice was 30-160 cm/s. An increase in SPL resulted in an increasing velocity of the displacement bands. A change in F0 did not lead to statistically relevant changes in the measured velocity.

CONCLUSION

A combination of short-interval, color-filtered double-flash stroboscopy and a two-point light projection method enables measurements of the velocity of vocal fold movements. The SPL is the important factor for the velocity change within the phonatory cycle. F0 seems not to covary with the velocity of the horizontal amplitude during the closing phase of the phonatory cycle.

Endoscopic Measurement of Vocal Fold Movement during Adduction and Abduction

OBJECTIVES/HYPOTHESIS

Whereas vibration of the vocal folds has been analyzed and modeled in detail, less attention has been paid to quantifying the slower motions of abduction and adduction. Because these gestures reflect neuromuscular function, cartilage geometry, and joint mobility, objective measurement might improve assessment and treatment of patients with neuromuscular or structural disease.

STUDY DESIGN

Prospective, observational.

METHODS

Twenty-one normal adult volunteers performed a repeated "ee-sniff" task at three rates during flexible endoscopy. Distortion in the images was corrected and frame-by-frame analysis of the angle between the true vocal folds (glottic angle) yielded measures of maximum abduction angle (MAA) and mean angular velocities of abduction (MVAB) and adduction (MVAD).

RESULTS

Reliability tests indicated interjudge variability of 3.8 degrees (deg). The mean MAA was 51 deg and ranged from 31 to 77 deg across subjects. The mean MVADs were 229, 309, and 475 deg/s for slow, medium, and fast rates, respectively, and the mean MVABs were 330, 388, and 441 deg/s for slow, medium, and fast rates, respectively. Statistical analysis showed greater influence of gesture rate on adduction than on abduction.

CONCLUSIONS

The glottic angle can be reliably measured from flexible endoscopic images and angular velocities of vocal fold abduction and adduction can be determined from analysis of sequential video frames. Accuracy is significantly enhanced by correction of distortion in the images. This approach holds promise for objective characterization of vocal fold function in patients with a variety of disorders.

Laser projection in high-speed glottography for high-precision measurements of laryngeal dimensions and dynamics

The detection of metric dimensions of laryngeal structures yields valuable information for both clinical and research purposes. The use of a laser projection system combined with a high-speed camera system enables the derivation of absolute spatial dimensions of the larynx. Vocal fold length, vibratory amplitudes and velocity can be derived. This was shown on 13 female and 9 male larynges during phonation of a vowel at different pitches. The vocal fold length, the amplitude of oscillation and the velocity of vibration were analyzed in between pitches of 119 to 236 Hz in the male group and 181 to 555 Hz in the female group. The vocal folds' length ranged from 8.4 to 14.3 mm in the male group and from 7.7 to 15.6 mm in the female group. Corresponding amplitudes varied from 0.33 to 1.24 mm (male) and from 0.38 to 0.82 mm (female). The maximal velocity of vibration was between 0.48 and 0.85 m/s in males and between 0.47 and 1.3 m/s in females without showing significant correlation between each parameter. The described technique enables the detection of absolute spatial laryngeal dimensions of female and male subjects at different pitches. Dynamic processes such as velocity of vibration can be quantified. The detection of metric data serves to optimize biomechanical model computations and provides valuable information in diagnostics and interpretation of organic and non-organic voice disorders.

Aerodynamics, voice quality, and laryngeal image analysis of normal and pathologic voices

PURPOSE OF REVIEW

The purpose of this review is to describe examinations of phonatory function and their relation to image analysis of the unilaterally immobile larynx. Special emphasis was placed on image analysis using three-dimensional endoscopic images produced from CT scans.

RECENT FINDINGS

Developments in modern image processing technique have led to the quantification of various aspects of vocal fold vibration. Stroboscopic images of the vocal fold were digitized and, subsequently, the glottal gap area, amplitude, and degree of bowing were analyzed quantitatively in relation to phonatory function. Vocal fold vibration was observed with the aid of videokymography, during which images from a single transverse line can be recorded. Successive line images were shown in real time on a monitor, with the time dimension displayed in the vertical direction. This system enabled the assessment of left-right asymmetries, open quotient, propagation of mucosal waves, and forth. Three-dimensional endoscopic images derived from multislice CT scans provided a novel method for evaluating morphologic characteristics of the laryngeal lumen in relation to phonatory function. The combination of three-dimensional endoscopy and coronal reconstructed images supplemented stroboscopic findings exemplified by differences in vertical position and thickness between the vocal folds.

SUMMARY

Depth information about the vocal fold as well as the presence of paradoxic movement of the affected vocal fold and overadduction of the healthy vocal fold during phonation should be taken into account when surgical intervention to improve hoarseness resulting from unilateral vocal fold immobility is performed. Phonatory function tests, videostroboscopy, and laryngeal image analysis are prerequisites to achieving this goal.

Vocal fold vibration irregularities caused by different types of laryngeal asymmetry

The common symptom of hoarseness is regarded to be caused by (1) turbulences and air loss due to incomplete glottic closure and (2) irregular vibrations of the vocal folds. With real time resolution, the latter can only be observed using high-speed recording techniques (> or =2,000 images/s). In this paper an actual recording method is described, called high-speed glottography (HGG), which quantifies vibration irregularities. It combines imaging and image processing techniques with a functional endoscopy of the disordered voice and delivers motion curves separately for each vocal fold. They are fitted with a computer simulation in order to identify the underlying driving parameters of the vibration. A vocal fold is assumed to vibrate as a system of two coupled oscillators ("two-mass model"). From the model fit to bilateral motion curves, the subglottal pressure, muscular tension and oscillating masses of the vocal folds can be computed with reasonable accuracy. Besides normal voices, HGG has been applied to selected clinical cases of voice disorders. Two types of irregularities have been measured: there is a frequency difference either between left and right vocal folds (horizontal asymmetry) or on one side between the ventral and dorsal third (vertical asymmetry). By modeling, both categories of irregular motion curves can be explained in detail. It is presumed that laryngeal asymmetry (either in mass or tension) causes irregular vibrations.

Imaging of the larynx--extending the use of stroboscopy-related techniques

Three methods (I-III) are presented to demonstrate how technical modifications in the use of stroboscopy-related techniques can be applied to further analyze vocal fold vibrations. (I) With double exposure videostroboscopy, dynamic properties of vocal folds can be visualized within one single image. This allows for estimations of horizontal vibratory velocity of the vocal fold margins. (II) Stroboscopic transillumination of the larynx makes it possible to localize initial vocal fold opening in the horizontal glottal plane and to visualize different vibratory opening patterns. Bidirectional color-coded endoscopic imaging of the larynx facilitates a semi-automated, digital measurement of the glottal area. (III) Stroboscopic illumination using four light emitting diodes (LEDs) clipped on a rigid endoscope and triggered by a portable 'pocket-sized', battery-powered electronic control device offers new prospects for performing stroboscopy outside of specialized clinical facilities.

Comparison of the phonation-related structures among pig, dog, white-tailed deer, and human larynges

There is an important need for good animal models of the larynx for the study of the physiology of phonation. The dog's larynx has been used as an animal model for more than 2 centuries of phonatory research. However, there is some evidence that the pig larynx has advantages over the dog larynx as a model of phonation. Another larynx that is readily available is the deer larynx. In this comparative study, the laryngeal anatomy and function were examined in 4 species--human, pig, dog, and white-tailed deer. Particular attention was directed to those structures that one would predict could affect phonation, from the anatomic and biomechanical point of view. Although the vocal fold length was similar for all 4 species, the larynges described differed in some phonation-related characteristics. The data suggest that from a structural perspective, the pig larynx is a superior model for phonatory research.

Noninvasive assessment of vocal fold mucosal wave velocity using color doppler imaging

The vibratory movement of the vocal folds (VF) plays an important role in normal function of phonation. We developed a noninvasive technique to quantify the human mucosal wave velocity (MWV) in vivo using color Doppler imaging (CDI). During phonation, the motion of mucosa-air interface generates a unique pattern of US color artefacts that assist the identification of true VF location. An in vitro study using a vibrating string phantom was conducted to investigate how the CDI displayed a vibrating soft tissue at high frequency. The vibrating amplitude, frequency, mass density and the acoustic impedance of the soft tissues were found to dominate the formation of color artefacts. Based on the model of finite string with fixed ends, we estimated the mean MWV for 10 adult volunteers (6 men, 4 women, ages 34 +/- 5 years) with normal VF function. The mean MWVs for the men were found to vary from 2.1 to 10 m/s in a frequency range of 85 to 310 Hz at their comfortable pitch and intensity, and the women typically had higher MWVs that varied from 5.0 to 16.5 m/s in a frequency range of 180 to 480 Hz. The MWV increased linearly with the frequency and there was no observable difference in mucosa stiffness due to the effect of gender. The variation in MWV as it propagates vertically can be seen from the color and shape of the artefacts. The VF polyp resulted in abnormal MWV and different CDI vibratory artefacts. The CDI artefacts provide insight on the dynamics of mucosa structure during phonation, and the method presented is promising for noninvasive monitoring of laryngeal functions clinically.

Noninvasive assessment of laryngeal phonation function using color Doppler ultrasound imaging

Color Doppler imaging (CDI) was used to identify the morphology of vocal folds (VF) and to quantify the tissue horizontal displacement velocity (HDV) in the vibrating portion of VF. Mucosal HDV that gives an estimate of the stiffness of the VF cover is very important clinically. The VF and its cover were shown to be very hypoechoic and not adequately visible in B-scan image. However, in this study, we found that the structure of the true VF, especially the mucosa and the superficial layer of the lamina propria, the so-called "cover," can be easily identified and evaluated using CDI. The mean VF displacement velocity was measured by decoding the pseudocolor codes of the ultrasound (US) image at the vibrating sites. The mucosal mean HDV obtained from 10 normal men of age 34 +/- 8 years phonating at their most comfortable pitch and intensity (98 +/- 12 Hz, 55-65 dB) was about 68 +/- 10 cm/s, which agreed reasonably with the literature. Therefore, the CDI could be used as a potential tool for assessing the phonation function in the larynx nonintrusively.

Vocal Fold Impact Stress Analysis

Vocal fold impact stress (force/area) has been implicated as a factor possibly contributing to the formation of nodules and polyps. The force of impact of a moving body is related to its acceleration. Since the mass of the folds is relatively constant, one expects impact force to be directly proportional to acceleration. A measure that reflects the relative displacement of the vocal folds is photoglottography (PGG). The velocity and acceleration of the folds are easily obtained by calculating the first and second derivatives of the PGG displacement waveform. This study, therefore, compared the second derivative of the PGG signal with simultaneously measured impact stress in an excised canine larynx model. Glottal transillumination (PGG) was measured with a subglottic transducer. A miniature force transducer placed in the midline between the vocal folds measured impact stress at the midglottal position. For nine different larynges, there was a positive and linear relationship between the second derivative of PGG and impact stress. The statistically significant results support the hypothesis that the second derivative of PGG m ay provide a use fulnoninvasive way to estimate relative vocal fold impact stress.

Vocal fold physiology

This article examines the physiologic factors responsible for the production of phonation in humans. The article begins with an explanation of the control mechanisms of phonation and theories of vocal fold vibration. The physiologic concepts are based on the myoelastic-aerodynamic, body-cover, and mucosal wave theories. An evaluation of the cover-body theory is explained in terms of pitch control. The factors that regulate the vocal folds to produce pitch changes, intensity variation, and register effects are outlined. The changes in pitch, intensity, and voice qualities are related to the vocal fold mass, tension, subglottic pressure, and airflow generated by the phonatory systems. A brief summary of abnormal voice production is given in terms of disordered physiology and the emerging theory of chaos.

Strobophotoglottographic transillumination as a method for the analysis of vocal fold vibration patterns

The purpose of this exploratory study was to determine if laryngeal transillumination in combination with stroboscopy (strobophotoglottography; SPGG) is useful for (1) the visualization of vocal fold vibration (VFV) opening patterns, (2) the localization of initial vocal fold opening in horizontal glottal thirds (anterior, midmembranous, and posterior), (3) determination of the temporal correspondence of the so-called electroglottography (EGG)-knee and initial vocal fold separation, and, finally, (4) automatized quantitative measurements of glottal area function within endoscopic images. With stroboscopic transillumination, initial inferior vocal fold separation was detectable during the "closed" phase, where the vocal folds were still closed in the upper portion and therefore initial inferior vocal fold separation could not be visualized with usual laryngoscopy techniques. In the horizontal plane within similar fundamental frequencies in modal voice registers in two male subjects, localization of initial glottal opening depended on the voice types used (soft, normal, or pressed phonation). We found zipperlike posterior-to-anterior openings, initial midmembranous openings, initial anterior openings, as well as simultaneous initial opening of all three portions in the two healthy male adults examined. This technique proved to add temporal and spatial information to vocal fold opening patterns and extends our examination techniques to the very beginning of vocal fold opening at the inferior portion. Simultaneous electroglottogram tracking and comparison with bidirectionally illuminated stroboscopic images revealed a time-locked correspondence of the EGG-knee with the aforementioned initial inferior vocal fold separation. Bidirectional illumination combined with digital color extraction techniques allowed for image separation of subglottally and supraglottally illuminated structures. This facilitated vocal fold contour detection and automatized image processing, for example, for determination of glottal area function, and is considered to be a further step to objective automatized quantitative measurements within endoscopic images.

Glottographic phase difference in recurrent nerve paralysis

Phase measures with simultaneously recorded electroglottography (EGG) and photoglottography (PGG) signals have been studied in canine models and found to be sensitive to the effect of recurrent laryngeal nerve (RLN) paralysis on vocal fold vibration. This study examined the usefulness of this type of measure in clinical application. The combined glottographic signals were obtained from 5 men with a diagnosis of unilateral RLN paralysis and 5 age-matched controls. In the patient group, EGG waveforms were found to have a consistent phase delay in relation to PGG. A measure of the overall glottographic phase difference (GPD) was found to significantly distinguish the control group (mean GPD = 0.2371 ms) from the patient group (mean GPD = -0.2765 ms). A validity analysis performed on 19 subjects with or without unilateral RLN paralysis confirmed that the GPD test had a relatively high efficiency (91.7%) in detecting unilateral RLN paralysis in the male population.

Integrated analyzer and classifier of glottographic signals

Electroglottography (EGG) and photoglottography (PGG) are two plausible methods to study voice production for monitoring the patterns of laryngeal vibrations. It has been suggested that measures such as open quotient and speed quotient calculated from glottographic signals can provide useful information regarding pathological phonation. In this paper, an integrated analyzer and classifier of glottographic signals was implemented. The system makes it possible to calculate the measures from digitized EGG and PGG signals automatically in order to examine vocal fold abnormality. The system developed several techniques to extract features from glottographic signals and proposed a statistical classification method that can possibly aid the diagnosis process. To check the reliability of the system, a training set and a test set of glottographic signals from normal people and patients with recurrent/superior laryngeal paralysis were analyzed and classified by the system. The results showed that the system is a useful tool for quantitative study of phonatory pathophysiology and can be used by the examiner who is interested in the clinical examination of glottographic signals. Moreover, glottographic techniques may have some clinical applications in the quantitative documentation of phonatory function in patients with voice disorders but requires further evaluation before clinical application.

Quantitative measurement of mucosal wave by high-speed photography in excised larynges

The movement characteristics of mucosal waves of the vocal fold are important components in normal phonation. Quantitative studies of the mucosal wave have used stroboscopic techniques from a supraglottic view. The current study measured displacement of mucosal epithelium during experimental phonation by using high-speed photography from an infraglottic view. Effects of thyroarytenoid contraction, increased mean airflow rate, and variation of vocal fold length were examined in canine larynges. Top and bottom vocal fold "lip" amplitude, fundamental frequency, and phase difference were the dependent variables examined. Thyroarytenoid contraction increased the amplitude of the top and bottom lips, decreased the fundamental frequency, and increased the phase difference. Increase in airflow through the glottis decreased the top lip amplitude and phase difference and appeared to increase the fundamental frequency and to decrease the bottom lip amplitude. Vocal fold lengthening decreased the bottom lip amplitude and increased the fundamental frequency and appeared to decrease the top lip amplitude and phase difference.

Glottographic signal perturbation in biomechanically different types of dysphonia

Glottographic signals may be superior to acoustic signals for tracking glottal source perturbations, since supraglottal vocal tract effects on glottographic signals are relatively minimal compared with the acoustic signal as measured beyond the lips. This study compared the ability of differing signals to differentiate among normal voices and abnormal voices that were due to two categories of biomechanical disease. Acoustic, electroglottographic, and photoglottographic signals recorded during vowel phonation sustained by 26 normal subjects and 65 patients were measured for perturbations of frequency and amplitude. One-way analysis of variance (ANOVA) revealed that amplitude perturbation measures from photoglottographic signals significantly differentiated neuromuscular from mass lesion sources of dysphonia. Acoustic and electroglottographic signal perturbations differentiated between normal and abnormal voices but did not distinguish between the dysphonic characteristics of neuromuscular disorders and those of mass lesions of the vocal folds.