[Measurement and interpretation of irregular vocal cord fold vibrations]

Voice pathology classification based on High-Speed Videoendoscopy

This work presents a method for automatical and objective classification of patients with healthy and pathological vocal fold vibration impairments using High-Speed Videoendoscopy of the larynx. We used an image segmentation and extraction of a novel set of numerical parameters describing the spatio-temporal dynamics of vocal folds to classification according to the normal and pathological cases and achieved 73,3% cross-validation classification accuracy. This approach is promising to develop an automatic diagnosis tool of voice disorders.

[Hoarseness: biomechanisms and quantitative laryngoscopy]

Every phonosurgical procedure alters endolaryngeal anatomy; be it by removing tissue, or injection or implantation of autologous or foreign material. However, the effect that an altered airflow cross section and changed soft tissue elasticity will have on the voice cannot be predicted. With the aim of promoting rational indications for phonosurgery, the current article explains the biomechanisms of the normal and the disordered voice, including the complex interdependence of tissue viscoelasticity, glottal airstream and sound production. According to European Laryngological Society (ELS) recommendations, five - not entirely mutually independent - evaluation criteria form the basis of indication assessments: self-rating (by the patient), proxy rating (by the physician), technical signal analysis (computerized), aerodynamics (spirometry) and vibration analysis (stroboscopy). The ELS evaluation standards agreed upon in 2001 enable indications and - by virtue of pre- and postoperative comparisons - therapeutic successes to be assessed. The 10-year-old ELS protocol has been updated by a real-time method for visualizing vocal fold vibrations: the phonovibrogram (PVG) has replaced stroboscopy. Independently of the morphological anatomic details of the larynx, PVG visualizes the symmetry and regularity of vocal fold motion, thus allowing preoperative estimation of tissue elasticity.

Spatiotemporal analysis of high-speed videolaryngoscopic imaging of organic pathologies in males

PURPOSE

The aim of this study was to identify parameters that would differentiate healthy from pathological organic-based vocal fold vibrations to emphasize clinical usefulness of high-speed imaging.

METHOD

Fifty-five men (M age = 36 years, SD = 20 years) were examined and separated into 4 groups: 1 healthy (26 individuals) and 3 pathological (10 individuals with contact granuloma, 12 with polyps, and 7 with cysts). Vocal fold vibrations were recorded using a high-speed camera during sustained phonation. Twenty objective glottal area waveform and 24 phonovibrogram parameters representing spatiotemporal characteristics were analyzed. Statistical group comparisons were performed to document spatiotemporal changes for organic lesions that cannot be determined visually. To look for specific pattern profiles within organic lesions, the authors performed linear discriminant analysis.

RESULTS

Thirteen parameters showed significant differences between the healthy group and at least 1 pathological group. The differences occurred more in temporal than in spatial parameters. Contact granuloma showed the fewest statistical differences (3 parameters), followed by cysts (9 parameters), and polyps (10 parameters). Linear discriminant analysis achieved accuracy performance of 76% (all groups separated) and 82% (healthy vs. pathological).

CONCLUSION

The results suggest that for males, the differences between healthy voices and organic voice disorders may be more pronounced within temporal characteristics that cannot be visually detected without high-speed imaging.

Advances in laryngeal imaging

Imaging and image analysis became an important issue in laryngeal diagnostics. Various techniques, such as videostroboscopy, videokymography, digital kymography, or ultrasonography are available and are used in research and clinical practice. This paper reviews recent advances in imaging for laryngeal diagnostics.

[Basic research on vocal fold dynamics: three-dimensional vibration analysis of human and canine larynges]

BACKGROUND

The understanding of normal and pathological vocal fold dynamics is the basis for a pathophysiological motivated voice therapy. Crucial vocal fold dynamics concerning voice production occur at the medial part of the vocal fold which is seen as the most critical region of mucosal wave propagation. Due to the limited size of the larynx the possibilities of laryngeal imaging by endoscopic techniques are limited.

MATERIAL AND METHODS

This work describes an experimental set-up that enables quantification of the entire medial and superior vocal fold surface using excised human and in vivo canine larynges.

RESULTS

The data obtained enable analysis of vocal fold deflections, velocities, and mucosal wave propagation. The reciprocal dependencies can be examined and different areas of vocal fold dynamics located. The vertical components obscured in clinical endoscopy can be visualized. This is not negligible.

CONCLUSIONS

In particular it is shown that the vertical deflection, which cannot be observed by clinical examination, plays an important part in the dynamics and therefore cannot be omitted for therapeutic procedures. The theoretically assumed entrainment and influence of the two main vibration modes enabling normal phonation is confirmed.

[Phonovibrogram: vocal fold dynamics integrated within a single image]

BACKGROUND

Stroboscopy is widely used and is quite adequate for the examination of normal voices, but with increasing hoarseness its suitability declines, even when it is supplemented by video recordings and image evaluation. Real-time procedures such as videokymography or high-speed (HS) video imaging are more suitable methods of observing the movements of the vocal folds in such cases. A drawback of any video recording is the later time-consuming offline replay of the films in slow motion and our restricted pattern recognition for motion and other time-dependent processes.

METHODS

The phonovibrogram (PVG) is an image-processing algorithm that extracts the vocal fold motions of a whole laryngoscopic HS video film and automatically compresses them into a single image.

RESULTS

Simple patterns that vary from person to person are revealed by PVG; these can be categorized by means of simple geometric forms, which a human observer can more easily recognize and interpret than dynamic motion patterns. The PVG computation is described in detail and an extensive guide to interpretation is given, illustrated by reference to theoretical and real examples.

CONCLUSION

In clinical conditions, HS laryngoscopic video recording is useful only in association with automatic image processing. The PVG procedure is a promising approach and tests should be performed with a view to further clinical validation.

Phonovibrography: mapping high-speed movies of vocal fold vibrations into 2-D diagrams for visualizing and analyzing the underlying laryngeal dynamics

Endoscopic high-speed laryngoscopy in combination with image analysis strategies is the most promising approach to investigate the interrelation between vocal fold vibrations and voice disorders. So far, due to the lack of an objective and standardized analysis procedure a unique characterization of vocal fold vibrations has not been achieved yet. We present a visualization and analysis strategy which transforms the segmented edges of vibrating vocal folds into a single 2-D image, denoted Phonovibrogram (PVG). Within a PVG the individual type of vocal fold vibration becomes uniquely characterized by specific geometric patterns. The PVG geometries give an intuitive access on the type and degree of the laryngeal asymmetry and can be quantified using an image segmentation approach. The PVG analysis was applied to 14 representative recordings derived from a high-speed database comprising normal and pathological voices. We demonstrate that PVGs are capable to differentiate and quantify different types of normal and pathological vocal fold vibrations. The objective and precise quantification of the PVG geometry may have the potential to realize a novel classification of vocal fold vibrations.

Erbium:YAG-Laserchirurgie an Stimmlippengewebe

The application of lasers in microsurgery of the vocal fold has very special requirements. Easy handling as well as a precise cutting quality with a small laser induced thermal necrosis zone are necessary. In this study, an Erbium:YAG laser was evaluated for phonosurgery. For this, vocal folds from the porcine larynx were irradiated with the Erbium laser wavelength of 3 mum. The ablation rate, as well as the mechanical and thermal damage were investigated as a function of pulse duration, repetition rate and laser fluence. The results show that Erbium lasers are well suited for application on the vocal fold. The laser induced thermal damage was restricted to a superficial layer of only about 20-30 microm, resulting in a loss of the multilayered epithelium. Thermal necrosis had a range of about 5 microm. Further investigations on the vocal folds of humans must be performed to determine whether this laser is qualified for clinical applications.

Clinically evaluated procedure for the reconstruction of vocal fold vibrations from endoscopic digital high-speed videos

Investigation of voice disorders requires the examination of vocal fold vibrations. State of the art is the recording of endoscopic high-speed movies which capture vocal fold vibrations in real-time. It enables investigating the interrelation between disturbances of vocal fold vibrations and voice disorders. However, the lack of clinical studies and of a standardized procedure to reconstruct vocal fold vibrations from high-speed videos constrain the clinical acceptance of the high-speed technique. An image processing approach is presented that extracts the vibrating vocal fold edges from digital high-speed movies. The initial segmentation is principally based on a seeded region-growing algorithm. Even in movies with low image quality the algorithm segments successfully the glottal area by an introduced two-dimensional threshold matrix. Following segmentation, the vocal fold edges are reconstructed from the computed time-varying glottal area. The performance of the procedure was objectively evaluated within a study comprising 372 high-speed recordings. The accuracy of vocal fold reconstruction exceeds manual segmentation results obtained by clinical experts. The algorithm reaches an information flow-rate of up to 98 images per second. The robustness and high accuracy of the procedure makes it suitable for the application in clinical routine. It enables an objective and highly accurate description of vocal fold vibrations which is essential to realize extensive clinical studies which focus on the classification of voice disorders.

Charakterisierung von Stimmlippen mittels optischer Kohärenztomographie

Optical coherence tomography (OCT) is a new, non-invasive method for investigating biological tissue, with a beam penetration of up to 3 mm. In this study, OCT was used on porcine and human larynxes. The porcine vocal folds were assigned to defined areas and examined by OCT followed by traditional histomorphological analysis. We were able to validate this new method by demonstrating that both OCT and the histological assays showed a clear demarcation of the epithelium mucosae from the deeper layers. OCT application to human vocal folds delivered same results. The current standard procedure for ensuring an accurate diagnosis if tissue is malignant, is still an invasive one. Our results show that OCT allows the collection of crucial information on the quality of morphological changes on a vocal fold without the necessity of being invasive. Thus, we propose that OCT be introduced as a new method for the detection of morphological changes in the vocal fold complementary to other established methods.

[High speed glottographic diagnostics in laryngology]

INTRODUCTION

High speed imaging (HSI) allows thousands of pictures to be taken of the vibrating vocal folds per second. Although already developed in 1939 in the USA, this method only became clinically useful a few years ago as the amount of data exceeded the capacity of physical memory.

MATERIALS AND METHODS

Rigid endoscopes are normally used for high speed glottography. After clinical investigation of the patient, kymographic analysis can be carried out off-line. Up to 8,000 grayscale images of 256 x 256 pixels can be stored by the Wolf HS Endocam 5560 that we used in our study. A maximum of 4,000 images/s can be taken by the high speed camera.

RESULTS

In high speed glottography, analysis and documentation of single vocal fold movements within the vibratory cycle is possible. In contrast to stroboscopic investigations, aperiodic movements of the vocal folds can be visualized. The duration of a recording differs from 2 to 4 s depending on the capture speed. The data transfer to the computer for archiving and analysing the images takes a few minutes.

CONCLUSION

HSI has advantages and disadvantages compared to videoendoscopy and videostroboscopy. The main advantage is the visualisation of aperiodic movements, the disadvantages are the transfer time for the data and the poorer image quality compared to conventional videoendoscopy. Nevertheless HSI is a very promising technique in laryngological investigation.

[Therapy for unilateral vocal fold palsy]

The main symptom of unilateral vocal fold palsy is hoarseness, which can cause considerable disturbance to the patient depending on its extent and the patient's individual situation. Therapy aims at the restitution of a tuneful and resilient voice, which can be achieved by surgical or conservative means, improving the glottal closure and synchronizing the vocal fold vibrations during phonation. Vocal therapy is a common conservative method that may be supported by psychotherapeutic or physical procedures. In surgical therapy, there is a distinction between techniques of endoscopic augmentation by injecting different materials into the vocal folds and transcutaneous laryngeal framework surgery, i.e., transferring the paralyzed vocal fold to the glottal midline. Particularly apt for injection are biocompatible materials amount and position whose can easily be controlled. However, the inevitable resorption of many materials causes deterioration in voice quality. Furthermore, the change of vocal fold morphology obstructs regular phonatory vibration. On the other hand, medialization thyroplasty leads to permanent voice amelioration without a substantial complication rate when performed by experienced surgeons.

Bestimmung der subjektiven Beeinträchtigung durch Dysphonien

OBJECTIVE

The purpose of this study was to estimate the correlation between the voice handicap index (VHI) and the voice related quality of life (VRQOL) questionnaire with respect to gender and diagnosis (functional vs organic dysphonia).

MATERIALS AND METHODS

A total of 52 German speaking patients aged 48.8+/-22.0 years suffering from dysphonia of different benign etiologies (functional dysphonia: 18 women, 9 men; organic dysphonia: 13 women, 12 men) completed German versions of both the VHI and the VRQOL questionnaire without prior information on their individual diagnosis. Another 52 individuals without voice complaints served as age and sex matched controls. Complete data sets of all participants were analyzed using the Microsoft Excel and MATLAB software packages.

RESULTS

The results of both questionnaires correlate at a significant level, both for total score (r=-0.9) and the subscores (r=-0.74-r=-0.84) with only slight differences when comparing women and men and patients with functional and organic voice disorders.

CONCLUSIONS

Both questionnaires provide very similar results. Thus, for clinical purposes, it seems justified to restrict oneself to using only one of the questionnaires. Whenever basic information on the patients' self perception of a voice disorder is required, the VRQOL questionnaire with only ten items may be easier to handle than the VHI questionnaire with 30 items.

K�rperbeschwerden bei Patienten mit Dysphonien

BACKGROUND

In previous studies, patients with benign organic and functional voice disorders were shown to suffer from physical complaints. The present study focuses on a specific nosologic classification of these disorders in the sense of diagnosing a somatoform illness.

PATIENTS AND METHODS

Eighty patients (50 women, 30 men) aged 44+/-11 years (18-60), suffering from various voice disorders (functional: n=18 women, n=13 men; organic: n=32 women, n=17 men), were examined after informed consent. Physical complaints were assessed using the Giessen Complaint Questionnaire GBB-24. Age and gender matched normal controls were taken from the literature. Data were analyzed using the non parametric two-by-two four-field-test.

RESULTS

The individual diagnosis of dysphonic women showed pathologic values in all subscales except limb complaints. The individual diagnosis of men showed pathologic values in the limb complaints subscale (P<0.05). When comparing functional and organic disorders, no significant difference (P>0.05) was found in neither of the gender groups.

DISCUSSION AND CONCLUSIONS

Depending on gender and type of voice disorder, dysphonic patients suffer from different physical complaints. Both patients with functional and organic disorders are affected. Therefore, it does not seem justified to classify functional voice disorders as somatoform disorders.

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.

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.