Browsing by Subject "Vocal Cords"
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Item Automated Analysis of Electroglottographic Signal in Adductor Spasmodic Dysphonia(2013-01-22) Somanath, Keerthan; Mau, TedINTRODUCTION: The human voice can be evaluated by a variety of methods. Electroglottographic (EGG) signal is produced when vocal fold vibrations produce cyclic fluctuation in the electrical impedance across the larynx. The EGG signal thus reflects the degree of contact between the vocal folds during voice production and provides a measure of voice quality based on phonatory physiology. However, the utility of EGG has been limited because existing methods of EGG signal analysis focus on the evaluation of 2-3 parameters in a segment of sustained vowel production, which does not reflect pathologies more apparent in conversational speech. We hypothesize that the EGG signal can capture perceptually relevant information from continuous speech in adductor spasmodic dysphonia (ADSD), an enigmatic speech disorder. OBJECTIVES: 1. To develop an automated computer algorithm to analyze the EGG signal in continuous dysphonic speech. 2. To identify EGG waveform features that correlate with the perceived quality of vocal strain in ADSD. METHODS: A computer program was created and refined in MATLAB to display and analyze EGG data via a graphical user interface (GUI). An automated peak-detection algorithm was developed using the differentiated EGG signal and used to perform simultaneous multi-parameter analysis on the EGG signal from normal speech and speech in patients with ADSD. Between-group comparisons were made using two-tailed Student's t test. Also, intrasubject comparison was made between strained and less-strained syllables in ADSD speech. RESULTS: A program was successfully written to allow the display and automated analysis of EGG data from samples of continuous dysphonic speech. The program was found to generate data with good internal consistency. Application to normal and ADSD subjects showed that the open quotient parameter was able to distinguish between strained and less-strained syllables with statistical significance (p=0.04). DISCUSSION/CONCLUSION: We have developed a method to analyze EGG signal from samples of continuous dysphonic speech. The numerical and graphical data obtained support the utility of EGG as an objective means to clinically highlight the speech differences between normal subjects and subjects with ADSD. Further testing to establish normative values for the analyzed EGG parameters and their subsequent comparison with patient EGG data is required to affirm their utility for routine clinical voice assessment.Item Clinical Applications of a Computational Voice Simulator(2016-01-19) Rao, Ashwin; Mau, TedBACKGROUND: Given input vocal fold tissue geometries and mechanical properties, a simulator can produce a virtual voice of a defined pitch and sound pressure level. A simulator gives us a tool to systematically investigate the effects of changes to vocal fold geometry or tissue properties on the voice. OBJECTIVE:To create a user-friendly graphical interface for the NCVS voice simulator, and to use it to determine gender differences in vocal fold tissue properties. METHODS: Graphical user interface (GUI): A GUI was programmed in MATLAB, with windows that separately allow user control of (1) vocal fold tissue geometries and mechanical properties, (2) ranges of inputs for "brute force" simulations in which a range of properties are investigated, and (3) optimization parameters that allow "smart" simulations with target pitch and sound pressure levels. Geometric and tissue properties: A literature search was performed to determine reasonable values for vocal fold superficial layer, the vocal ligament, and vocalis muscle to use in the simulator. Gender differences in tissue properties: Two groups of simulations were carried out, one using typical female geometries with the average female speaking voice frequency of 200 Hz, the other using typical male geometries and 100 Hz as the desired target. Assessment of outcome: Each group of simulations comprised of several thousand simulations, with each simulation corresponding to a specific combination of frequency, sound pressure level, and corresponding tissue properties that generated those specific voice qualities. Clusters of solutions were identified with cluster analysis. RESULTS: Solutions visualized in 2D plots showing a strong linear dependence of voice frequency on the longitudinal shear modulus of the vocal ligament, consistent with the general understanding of vocal physiology. There was no clear dependence of frequency on the other tissue properties. Cluster analysis for the male simulation showed two groups of solutions. The first group had the superficial layer longitudinal shear moduli (μ'1) roughly equal to that of the muscle (μ'3). The second group had a ratio of μ'1/μ'3 between 10-20. This indicates that, for a male voice output of 100 Hz, tissue parameters are most optimal if the superficial layer and muscle have similar stiffness, or if the superficial layer is about 10-20 times stiffer than the muscle. The translayer ratio of μ'2/μ'3 also showed two main clusters: one close to 1 and another at a ratio of around 100. This indicated that, for an average male voice, the vocal ligament and muscle should have comparable stiffness, or the ligament is about 100 times stiffer than the muscle. On the other hand, cluster analysis for the female simulation only showed one solution group, with both μ'1/μ'3 and μ'2/μ'3 ratios of around 1. This indicated that, for a female voice output around 100 Hz, the superficial layer, muscle, and ligament layers all should have comparable stiffness levels. CONCLUSIONS: We have shown that simulations for female geometric parameters calculate different clusters than those for male parameters, given the same target pitch and SPL. By creating a GUI for the NCVS voice simulator, we are now enabling clinician users explore how various morphological defects and changes can affect the human voice, ultimately leading to improved clinical and surgical outcomes.Item The Decelluarized Human Umbilical Vein (HUV) as an Allogeneic Scaffold for Vocal Fold Tissue Engineering(2007-12-18) Rodriquez, Maritza Lizette; Chan, Roger W.The human umbilical vein (HUV) has great potential for use as a biological tissue engineering scaffold. Thus far, it has been used as an extracellular matrix (ECM) scaffold for cardiovascular tissue engineering applications due to its many structural and biomechanical advantages. Since the HUV is vascular derived, the chemical and physical environment from which it came allows it to be more conducive to cell adhesion and ECM remodeling than currently available synthetic scaffold materials. The connective tissue component of the HUV is primarily the Wharton's Jelly (WJ), a gelatinous connective tissue surrounding the umbilical cord vessels. It is rich in peptide growth factors, glycosaminoglycans (GAGs), and proteoglycans, many of which are similar to those present in the vocal fold lamina propria. The vocal fold undergoes vibrations at relatively large amplitudes (1-2mm) and relatively high frequencies (100- 300Hz), thus requiring a scaffold that could endure such mechanical stimuli. The lamina propria consists of proteoglycans, glycosaminoglycans (especially hyaluronic acid), and fibrous proteins (collagen and elastin) that are optimally designed to withstand the unique mechanical stimuli. The natural biological constituents of the human umbilical vein, its structural stability, and the novel method for preparing uniform specimens make this tissue potentially useful as a vocal fold scaffold. Also, as a potential allograft, the possibility of interspecies viral infectivity is low. Native HUV tissue is obtained with an automated dissection method developed by Daniel et al. (2005), where HUVs are dissected from umbilical cords within two to three minutes, with uniform and repeatable dimensions using a custom built steelcutting machine. Preliminary experiments were conducted to determine the optimal decellularization protocol. Once this was determined, 15 cords were obtained to further examine the potential of the HUV as an acellular scaffold. Three cords from different donors (each sliced into 3 sections or scaffolds) were examined as follows: manually dissected, in the native state, decellularized, decellularized and cultured (controls), and recellularized. In these experiments, the HUV obtained was sliced into scaffolds of uniform dimensions (10-12mm x 17-20mm x 1-2mm), decellularized, recellularized with primary-culture human vocal fold fibroblasts, and cultured for 21 days. At the end of the 21 days, each scaffold was sliced into 3 sections, subjected to biomechanical testing, scanning electron microscopy (SEM) and histology. Using a custom-built linear simple shear rheometer, the viscoelastic properties of each scaffold section were determined. Preliminary experiments determined the optimal decellularization protocol based upon: the extent of decellularization, the depth of cellular infiltration, and their shear modulus (G') and dynamic viscosity (η') as compared to those of the human vocal fold. Recellularized scaffolds were determined to have G' and η' values similar to those of the human vocal fold cover obtained from a 79-year-old male and a 53-year-old female. Scanning electron microscopy (SEM) showed that viable fibroblast cells, as characterized by a lighter shade of gray and an elongated shape, attached to the abluminal surface of the scaffold. Native tissue, decellularized tissue, and control tissue all appeared to have an intact ECM protein network structure as shown by the scanning electron micrographs. Histological staining with hematoxylin and eosin, Alcian blue with and without hyaluronidase, Periodic acid-Schiff's reagent, Safranin-O, and Masson's Trichrome were used to examine cellular attachment, depth of cellular infiltration, the structure of the tissues and the scaffolds, and the expressions of various proteins and GAGs, including glycogen, hyaluronic acid, chondroitin sulfates A, B, and C, keratosulphate, mucins, sialomucins, and sulphated sialomucins. Results showed the presence of these proteins and GAGs in the native HUV tissue, varying extent of decreases in protein and GAG densities for the decellularized scaffold, and large decreases in protein and GAG densities for the control scaffold. However, the recellularized scaffold was able to regain some of the proteins and GAGs after 21 days of culture. Cell recovery results showed that the seeding of one million cells on each scaffold (with a seeding density of about 5,000 cells/mm2) led to an initial cell attachment of 1.7-1.8%, a faster proliferation than similar previous studies, and an average final cell count of around 480,000 cells per scaffold. These findings provided preliminary support to the potential of the acellular HUV scaffold as an allograft for the repair of vocal fold lamina propria lesions. The HUV consists of proteins conducive to cellular attachment and proliferation, has viscoelastic properties similar to those of the human vocal fold cover, demonstrates deep cellular infiltration, and can support the growth and recovery of a relatively large number of viable cells within a short period of time. Further studies involving a larger number of samples are needed to verify and extend the present findings.Item Quantifying the Perceptual Quality of Strain: An Electroglottographic Analysis of Continuous Dysphonic Speech(2015-04-03) Somanath, Keerthan; Mau, TedINTRODUCTION: Excessive vocal effort perceived as strain may involve increased vocal fold compression. Electroglottography (EGG) in principle could provide a measure of strain directly connected to oscillatory kinematics at the sound source. The utility of EGG has been limited by considerable inter- and intra-subject variability. OBJECTIVE: This work aims to (1) develop an algorithm to analyze EGG signal in continuous, dysphonic speech and (2) identify parameters that correlate with strain. METHODS: EGG signal from 8 normal speakers and 8 subjects with adductor spasmodic dysphonia (ADSD) reading two-sentence excerpts from the Rainbow Passage was processed by the new software developed in MATLAB. The contact quotient (CQ), pulse width at the 50% amplitude level (EGGW50), and various closing slope and opening slope measures were extracted from selected speech segments. Intra-subject and inter-subject comparisons were then made. RESULTS: None of the EGG parameters differed between normal and ADSD speakers. Within- subject comparison among ADSD speakers showed that the opening slope measure SO7525 distinguished between the strained and unstrained syllables. CONCLUSION: These results provide further insight into the utility and limitations of EGG. While EGG may have limited utility in inter-subject comparison, it may provide a useful objective measure of vocal strain in the same subject with variable degrees of strain or over time.