Sensitivity of Phonation Onset Pressure to Vocal Fold Stiffness Distribution.

Phonation onset is characterized by the unstable growth of vocal fold (VF) vibrations that ultimately results in self-sustained oscillation and the production of modal voice. Motivated by histological studies, much research has focused on the role of the layered structure of the vocal folds in influencing phonation onset, wherein the outer "cover" layer is relatively soft and the inner "body" layer is relatively stiff. Recent research, however, suggests that the body-cover (BC) structure over-simplifies actual stiffness distributions by neglecting important spatial variations, such as inferior-superior (IS) and anterior-posterior gradients and smooth transitions in stiffness from one histological layer to another. Herein, we explore sensitivity of phonation onset to stiffness gradients and smoothness. By assuming no a priori stiffness distribution and considering a second-order Taylor series sensitivity analysis of phonation onset pressure with respect to stiffness, we find two general smooth stiffness distributions most strongly influence onset pressure: a smooth stiffness containing aspects of BC differences and IS gradients in the cover, which plays a role in minimizing onset pressure, and uniform increases in stiffness, which raise onset pressure and frequency. While the smooth stiffness change contains aspects qualitatively similar to layered BC distributions used in computational studies, smooth transitions in stiffness result in higher sensitivity of onset pressure than discrete layering. These two general stiffness distributions also provide a simple, low-dimensional, interpretation of how complex variations in VF stiffness affect onset pressure, enabling refined exploration of the effects of stiffness distributions on phonation onset.

Singing more, singing harsher: occurrence of nonlinear phenomena in a primate' song.

Nonlinear phenomena (NLP) in animal vocalizations arise from irregularities in the oscillation of the vocal folds. Various non-mutually exclusive hypotheses have been put forward to explain the occurrence of NLP, from adaptive to physiological ones. Non-human primates often display NLP in their vocalizations, yet the communicative role of these features, if any, is still unclear. We here investigate the occurrence of NLP in the song of a singing primate, the indri (Indri indri), testing for the effect of sex, age, season, and duration of the vocal display on their emission. Our results show that NLP occurrence in indri depends on phonation, i.e., the cumulative duration of all the units emitted by an individual, and that NLP have higher probability to be emitted in the later stages of the song, probably due to the fatigue indris may experience while singing. Furthermore, NLP happen earlier in the vocal display of adult females than in that of the adult males, and this is probably due to the fact that fatigue occurs earlier in the former because of a greater contribution within the song. Our findings suggest, therefore, that indris may be subjected to physiological constraints during the singing process which may impair the production of harmonic sounds. However, indris may still benefit from emitting NLP by strengthening the loudness of their signals for better advertising their presence to the neighboring conspecific groups.

Piezo1-expressing vocal fold epithelia modulate remodeling via effects on self-renewal and cytokeratin differentiation.

Mechanoreceptors are implicated as functional afferents within mucosa of the airways and the recent discovery of mechanosensitive channels Piezo1 and Piezo2 has proved essential for cells of various mechanically sensitive tissues. However, the role for Piezo1/2 in vocal fold (VF) mucosal epithelia, a cell that withstands excessive biomechanical insult, remains unknown. The purpose of this study was to test the hypothesis that Piezo1 is required for VF mucosal repair pathways of epithelial cell injury. Utilizing a sonic hedgehog (shh) Cre line for epithelial-specific ablation of Piezo1/2 mechanoreceptors, we investigated 6wk adult VF mucosa following naphthalene exposure for repair strategies at 1, 3, 7 and 14 days post-injury (dpi). PIEZO1 localized to differentiated apical epithelia and was paramount for epithelial remodeling events. Injury to wildtype epithelium was most appreciated at 3 dpi. Shhcre/+; Piezo1loxP/loxP, Piezo2 loxP/+ mutant epithelium exhibited severe cell/nuclear defects compared to injured controls. Conditional ablation of Piezo1 and/or Piezo2 to uninjured VF epithelium did not result in abnormal phenotypes across P0, P15 and 6wk postnatal stages compared to heterozygote and control tissue. Results demonstrate a role for Piezo1-expressing VF epithelia in regulating self-renewal via effects on p63 transcription and YAP subcellular translocation-altering cytokeratin differentiation.

Support of deep learning to classify vocal fold images in flexible laryngoscopy.

PURPOSE: To collect a dataset with adequate laryngoscopy images and identify the appearance of vocal folds and their lesions in flexible laryngoscopy images by objective deep learning models. METHODS: We adopted a number of novel deep learning models to train and classify 4549 flexible laryngoscopy images as no vocal fold, normal vocal folds, and abnormal vocal folds. This could help these models recognize vocal folds and their lesions within these images. Ultimately, we made a comparison between the results of the state-of-the-art deep learning models, and another comparison of the results between the computer-aided classification system and ENT doctors. RESULTS: This study exhibited the performance of the deep learning models by evaluating laryngoscopy images collected from 876 patients. The efficiency of the Xception model was higher and steadier than almost the rest of the models. The accuracy of no vocal fold, normal vocal folds, and vocal fold abnormalities on this model were 98.90 %, 97.36 %, and 96.26 %, respectively. Compared to our ENT doctors, the Xception model produced better results than a junior doctor and was near an expert. CONCLUSION: Our results show that current deep learning models can classify vocal fold images well and effectively assist physicians in vocal fold identification and classification of normal or abnormal vocal folds.

Laryngeal Diadochokinesis in the Mandarin Population.

INTRODUCTION: This study identifies the most suitable syllable for laryngeal diadochokinesis (LDDK) in Mandarin speakers. METHODS: One hundred and ten Mandarin speakers aged 18-83 years were used in the study. LDDK was assessed using quick repetitions of /ʔe/, /ʔi/, /ʔa/, /he/, /ha/, and /hi/. The observation index included the average rate (syllable/s) and regularity (%). RESULTS: In the various age groups, there was no significant difference in LDDK rate and regularity of adducted syllables (p > 0.05), and only the regularity of /ʔi/ is significantly different between aged 18-40 and 41-64 years (p = 0.040). When vocal fold adduction was compared between various syllables, there was no significant difference in LDDK rate and regularity (p > 0.05). In various age groups, the LDDK rate of abduction syllables is different (p < 0.05) compared with the LDDK regularity of abduction syllables (p > 0.05). In various abduction syllables, there is no difference in LDDK rate (p > 0.05); however, /ha/ and /hi/ have significant differences in LDDK regularity (p = 0.007). CONCLUSION: According to the preliminary data, /ʔa/ and /ha/ can be used as suitable indicators to analyse the coordination ability of the laryngeal movement of Mandarin speakers.

Differences in Glottal Closure and Visibility of the Anterior Commissure during Rigid-90°, Rigid-70°, and Flexible Laryngostroboscopy.

INTRODUCTION: The conventional rigid-90° and rigid-70° laryngostroboscopy has been so far considered the gold standard in assessing the vibratory behavior of the vocal folds and the glottal closure configuration during phonation. Meanwhile, this rigid laryngostroboscopy is more and more replaced by flexible chip-on-tip systems. The aim of this study was to evaluate the influence of these different endoscopic techniques on glottal closure configuration and on visibility of the complete focal fold length including anterior commissure during phonation. METHODS: Twenty-one euphonic subjects were enrolled (mean age 34.6 ± 9.5; m = 10, f = 11). They were examined with the three laryngoscopic techniques (conventional rigid-90°, rigid-70°, and flexible chip-on-tip laryngoscopy during low and high voice pitch with soft and loud voice intensity). For evaluating the degree of glottal closure, a modified classification of Södersten et al. was applied and the visibility of the anterior commissure was evaluated. The correlation of the three endoscopic techniques was assessed with Cohen and Fleiss' kappa. RESULTS: In even low loud phonation, the rigid-90° and rigid-70° endoscopies revealed a complete closure of the glottis in only 47.6% of subjects but with flexible endoscopy in 81%. The complete vocal fold length with anterior commissure was best visible with flexible endoscopy in 90.5% in low-soft and high-soft phonation. The rigid-90° endoscopy showed a slight agreement in comparison with the flexible endoscopy in regard to the types of vocal fold closure with a Cohen's kappa coefficient k = 0.199. The rigid-90° endoscopy showed an almost perfect agreement with k = 0.84 when compared to the rigid-70° endoscopy. The flexible endoscopy compared to the rigid-70° endoscopy showed a fair agreement with k = 0.346. CONCLUSION: We found mainly corresponding results in both rigid-90° and rigid-70° endoscopic techniques which can be explained by the same transoral approach with the tongue pulled out, whereas the flexible transnasal endoscopy mainly gives a better view on the anterior commissure. The influence of transorally or transnasally guided endoscopic techniques needs to be considered in interpretation of laryngostroboscopic parameters like vocal fold closure and supraglottal hyperactivity.

[Polypositional transcutaneous ultrasound assessment of vocal folds mobility. Ultrasonographic sign of laryngeal dysfunction]. / Polipozitsionnoe ul'trazvukovoe issledovanie golosovykh skladok v diagnostike narushenii podvizhnosti gortani.

Fiberoptic laryngoscopy is a standard procedure for evaluation of vocal folds immobility. However, this method is invasive, requires special qualifications and technical equipment, which limits its routine use. Therefore, in daily practice, the vast majority of laryngoscopy are performed by an indirect way, the accuracy of which depends on the specialist experience and the patient compliance. On the other hand, a large number of patients require for a convenient, non-invasive and inexpensive approach to assess the vocal folds mobility. The transcutaneous laryngeal ultrasonography can be such a method. However, the disadvantage of this technique is low informative value. OBJECTIVE: To increase the effectiveness of the diagnosis of laryngeal dysfunction using transcutaneous laryngeal ultrasonography. MATERIAL AND METHODS: Patients underwent laryngeal ultrasonography and videolaryngoscopy before and after thyroid or parathyroid surgery. Ultrasound was performed polypositionally in the transverse and oblique planes. Functional tests with breathing and breath holding were used. Qualitative (the smile or flying bird signs, the vertical closing line of the vocal folds, synchronicity and symmetry movement of the arytenoid cartilages) and quantitative (the length contraction of the vocal cord, the rotation angle of the arytenoid cartilage) ultrasonic parameters determin the normal vocal folds mobility. RESULTS: 996 patients were included in the study. Vocal folds paresis was detected in 106 (10.6%) patients. In 72 (7.2%) cases partial impaired mobility of the vocal folds (laryngeal dyskinesia) were detected. The echographic patterns of these patients were analyzed. Qualitative ultrasound signs of laryngeal dysfunction were identified: a crooked smile or falling bird signs, a closing line deformation of the vocal folds, an arytenoid immobility. Quantitative ultrasound signs included: a decrease in the length contraction of the vocal cord and a reduction of rotation angle of the arytenoid cartilage. Unilateral laryngeal paresis was diagnosed in 101 (10.1%) patients. In unilateral disorders the rotation angle of the arytenoid on the affected side was 0-14° and the length contraction of the vocal cord was 0-1.8 mm. A crooked smile or falling bird signs, a closing line deformation of the vocal folds and immobility of the arytenoid cartilages were also determined. In 5 (0.5%) cases bilateral laryngeal paresis was revealed, in which on both sides the rotation angles of the arytenoid were 0-14°, and the length contraction of the vocal cords was 0-1.8 mm. At the same time there was no a smile or flying bird signs and a closing line of the vocal folds. Laryngeal dyskinesia was characterized by a crooked smile or falling bird signs and a closing line deformation of the vocal folds. At the same time, partial mobility of the arytenoid cartilage was noted in comparison with the contralateral side (there was a difference in the rotation angle of the arytenoid between the right and left sides of 15 ° or more degrees). CONCLUSION: The sensitivity and specificity polypositional ultrasound of the vocal folds in women were 100% and 99.8%, in men - 85.7% and 99.2%, respectively.

Proteomic analysis reveals that aging rabbit vocal folds are more vulnerable to changes caused by systemic dehydration.

BACKGROUND: Older adults are more prone to develop systemic dehydration. Systemic dehydration has implications for vocal fold biology by affecting gene and protein expression. The objective of this study was to quantify vocal fold protein changes between two age groups and hydration status, and to investigate the interaction of age and hydration status on protein expression, which has not been investigated in the context of vocal folds before. Comparative proteomics was used to analyze the vocal fold proteome of 6.5-month-old and > 3-year-old rabbits subjected to water ad libitum or water volume restriction protocol. RESULTS: Young and older adult rabbits (n = 22) were either euhydrated (water ad libitum) or dehydrated by water volume restriction. Dehydration was confirmed by body weight loss of - 5.4% and - 4.6% in young and older groups, respectively, and a 1.7-fold increase of kidney renin gene expression in the young rabbits. LC-MS/MS identified 2286 proteins in the rabbit vocal folds of young and older adult rabbits combined. Of these, 177, 169, and 81 proteins were significantly (p ≤ 0.05) affected by age, hydration status, or the interaction of both factors, respectively. Analysis of the interaction effect revealed 32 proteins with opposite change patterns after dehydration between older and young rabbit vocal folds, while 31 proteins were differentially regulated only in the older adult rabbits and ten only in the young rabbits in response to systemic dehydration. The magnitude of changes for either up or downregulated proteins was higher in the older rabbits. These proteins are predominantly related to structural components of the extracellular matrix and muscle layer, suggesting a disturbance in the viscoelastic properties of aging vocal fold tissue, especially when subjected to systemic dehydration. CONCLUSIONS: Water restriction is a laboratory protocol to assess systemic dehydration-related changes in the vocal fold tissue that is translatable to human subjects. Our findings showed a higher number of proteins differentially regulated with a greater magnitude of change in the vocal folds of older adult rabbits in the presence of systemic dehydration compared to younger rabbits. The association of these proteins with vocal fold structure and biomechanical properties suggests that older human subjects may be more vulnerable to the effects of systemic dehydration on vocal function. The clinical implications of these protein changes warrant more investigation, but age should be taken into consideration when evaluating vocal treatment recommendations that interfere with body fluid balance.

Advances in Organ Preservation for Laryngeal Cancer.

OPINION STATEMENT: At the University of Wisconsin, all treatment of head and neck cancer patients begins with discussion at our multi-disciplinary tumor board. Most patients with T4 disease, with existing laryngeal dysfunction, considered unlikely to complete definitive CRT or who have a high risk of persistent aspiration after non-operative management undergo total laryngectomy. A laryngeal sparing approach is attempted on most other patients. Radiotherapy is delivered over 6.5 weeks, preferably with concurrent weekly cisplatin. If the patient is hesitant of chemotherapy or has contraindications to cisplatin, concurrent cetuximab may be offered. Patients treated with RT alone are often treated to the same dose, but via an accelerated schedule by adding a 6th fraction per week. The 6th fraction is given by delivering two treatments at least 6 h apart on a weekday of the patient's choosing. We consider the following to be major risk factors for clinically significant weight loss during treatment: a 10% or greater loss of weight in the 6 months prior to starting treatment, delivery of concurrent cisplatin, and treatment of the bilateral neck with radiation. Patients who have 2-3 of these characteristics are often given gastrostomy tubes prophylactically. Patients are seen 2 weeks after completion of therapy, and then every 3 months after completion for 2 years. A CT neck and PET-CT are performed at the first 3-month visit. They are seen twice in year three, and then yearly until years 5-7. At each of these visits, we have a low threshold to present the patient at our multidisciplinary tumor board for consideration of salvage laryngectomy if there are signs of progression.

Transcutaneous laryngeal ultrasonography in vocal fold assessment before and after thyroid surgery in light of recent studies.

Transcutaneous laryngeal ultrasonography (TLUS) has become a cheap, convenient, and novel method in vocal fold (VF) assessment. The gold standard method of VF examination is laryngoscopy. It requires ear, nose, and throat specialist consultation and additional equipment. Moreover, laryngoscopy causes distress to patients, and during the COVID-19 pandemic it is a high-risk, aerosol-producing procedure. The aim of the paper was to review publications on the role of TLUS in VF evaluation. Considered aspects included VF visibility, factors affecting them, and different variables measured during TLUS examination. The visibility of VFs in TLUS ranged from 72.8 to 100%. Among men it was significantly lower (17-100%) in comparison to women (83-100%). All but 2 authors concluded that TLUS is a viable tool that can be an alternative to laryngoscopy in diagnosing VFs. Obesity, age, male gender, height, calcified thyroid, and incision close to the thyroid cartilage were independent factors for inaccessible vocal folds. VF displacement velocity (VFDV) is the most objective parameter measured by Doppler, and it is proportional to the velocity of the wave causing the vibrations of the VFs. After VF paralysis, this parameter is reduced. Valsalva manoeuvre, low-frequency transducer, and different transducer positions can improve images obtained on USG. TLUS in a majority of cases can adequately assess whether the function of the VFs is intact or paresis/paralysis has occurred. It is noninvasive and rapid, it adds no extra cost, and it can be a part of the preoperative examination of the thyroid gland. TLUS can usually be a convenient alternative to laryngoscopy.

ß-Catenin signaling is essential for mammalian larynx recanalization and the establishment of vocal fold progenitor cells.

Congenital laryngeal webs result from failure of vocal fold separation during development in utero Infants present with life-threatening respiratory problems at birth, and extensive lifelong difficulties in breathing and voicing. The molecular mechanisms that instruct vocal fold formation are rarely studied. Here, we show, for the first time, that conditional inactivation of the gene encoding ß-catenin in the primitive laryngopharyngeal epithelium leads to failure in separation of the vocal folds, which approximates the gross phenotype of laryngeal webbing. These defects can be traced to a series of morphogenesis defects, including delayed fusion of the epithelial lamina and formation of the laryngeal cecum, failed separation of the larynx and esophagus with reduced and disorganized cartilages and muscles. Parallel to these morphogenesis defects, inactivation of ß-catenin disrupts stratification of epithelial cells and establishment of p63+ basal progenitors. These findings provide the first line of evidence that links ß-catenin function to the cell proliferation and progenitor establishment during larynx and vocal fold development.

Dynamic Biomechanical Analysis of Vocal Folds Using Pipette Aspiration Technique.

The voice producing process is a complex interplay between glottal pressure, vocal folds, their elasticity and tension. The material properties of vocal folds are still insufficiently studied, because the determination of material properties in soft tissues is often difficult and connected to extensive experimental setups. To shed light on this less researched area, in this work, a dynamic pipette aspiration technique is utilized to measure the elasticity in a frequency range of 100-1000 Hz. The complex elasticity could be assessed with the phase shift between exciting pressure and tissue movement. The dynamic pipette aspiration setup has been miniaturized with regard to a future in-vivo application. The techniques were applied on 3 different porcine larynges 4 h and 1 d postmortem, in order to investigate the deterioration of the tissue over time and analyze correlation in elasticity values between vocal fold pairs. It was found that vocal fold pairs do have different absolute elasticity values but similar trends. This leads to the assumption that those trends are more important for phonation than having same absolute values.

RNA sequencing identifies transcriptional changes in the rabbit larynx in response to low humidity challenge.

BACKGROUND: Voice disorders are a worldwide problem impacting human health, particularly for occupational voice users. Avoidance of surface dehydration is commonly prescribed as a protective factor against the development of dysphonia. The available literature inconclusively supports this practice and a biological mechanism for how surface dehydration of the laryngeal tissue affects voice has not been described. In this study, we used an in vivo male New Zealand white rabbit model to elucidate biological changes based on gene expression within the vocal folds from surface dehydration. Surface dehydration was induced by exposure to low humidity air (18.6% + 4.3%) for 8 h. Exposure to moderate humidity (43.0% + 4.3%) served as the control condition. Ilumina-based RNA sequencing was performed and used for transcriptome analysis with validation by RT-qPCR. RESULTS: There were 103 statistically significant differentially expressed genes identified through Cuffdiff with 61 genes meeting significance by both false discovery rate and fold change. Functional annotation enrichment and predicted protein interaction mapping showed enrichment of various loci, including cellular stress and inflammatory response, ciliary function, and keratinocyte development. Eight genes were selected for RT-qPCR validation. Matrix metalloproteinase 12 (MMP12) and macrophage cationic peptide 1 (MCP1) were significantly upregulated and an epithelial chloride channel protein (ECCP) was significantly downregulated after surface dehydration by RNA-Seq and RT-qPCR. Suprabasin (SPBN) and zinc activated cationic channel (ZACN) were marginally, but non-significantly down- and upregulated as evidenced by RT-qPCR, respectively. CONCLUSIONS: The data together support the notion that surface dehydration induces physiological changes in the vocal folds and justifies targeted analysis to further explore the underlying biology of compensatory fluid/ion flux and inflammatory mediators in response to airway surface dehydration.

Magnetic resonance imaging of the vocal fold oscillations with sub-millisecond temporal resolution.

PURPOSE: The temporal resolution of the MRI acquisition is intrinsically limited by the duration of the spatial encoding, which is typically on the order of milliseconds. Faster motion such as the vibration of the vocal folds during phonation cannot be imaged with conventional MRI as this would require sampling frequencies in the kilo-Hertz range. Here, a faster MRI acquisition strategy is presented that encodes a 1D periodic motion at a temporal resolution that is an order of magnitude higher compared to conventional MRI. METHODS: The proposed method encodes the position of an object moving along 1 dimension by applying very short phase encoding gradients along the same direction. This reduces the temporal resolution from the repetition time (TR) to the duration of the phase encoding gradients, which in this work was well below 1 ms. The technique is applied to the vocal fold oscillations and the position of the vocal folds is measured simultaneously using electroglottography (EGG). Simulations of the point spread function for regular encoding and the proposed method are performed as well. RESULTS: With this new phase, encoding strategy oscillations of the human vocal folds up to a frequency of 145 Hz could be dynamically imaged at 10 images per cycle. Simulations show the advantage of this method over conventional imaging of fast moving objects. CONCLUSION: A new method for MR imaging of fast moving spins is presented allowing a temporal resolution below 1 ms at a spatial resolution below 1 mm, circumventing TR as the limit for temporal resolution.

Inspiratory and Expiratory Flow Changes, Voice Symptoms and Laryngeal Findings during Histamine Challenge Tests.

OBJECTIVE: The aim of this study was to analyse the associations between the spirometry parameter changes in relation to laryngeal finding changes and self-reported voice and throat symptom changes among patients undergoing a histamine challenge test. PATIENTS AND METHODS: Thirty adult patients with a chronic cough underwent a histamine challenge test. Videolaryngostroboscopy and voice and throat symptoms were assessed using a visual analogue scale immediately before and after the challenge test. Correlations between the relative changes in spirometry values in relation to the change in vocal fold oedema and redness and self-reported voice and throat symptom changes during the challenge test were assessed. RESULTS: A correlation between the relative change in inspiratory and expiratory air flow values and the change in voice and throat symptoms during the histamine challenge test was found. The vocal fold oedema, visible on videolaryngostroboscopy, caused by the histamine challenge did not significantly affect the spirometry air flow values. CONCLUSION: The relative changes in inspiratory and expiratory air flow and voice and throat symptoms during the histamine challenge test correlated. The vocal fold oedema caused by the histamine challenge, visible on videolaryngostroboscopy, did not significantly affect the spirometry air flow values.

[Disorder of mobility of vocal folds on the background of hypoparathyroidism at patient after subtotal resection of thyroid gland]. / Narushenie podvizhnosti golosovykh skladok na fone gipoparatireoza u bol'noi posle subtotal'noi rezektsii shchitovidnoi zhelezy.

During surgery on the thyroid gland, injury to the recurrent nerve is possible with the development of a clinical picture due to impaired mobility of the vocal fold. A disturbance of the mobility of the opposite vocal fold in the form of a paradoxical spasm may join these manifestations if the parathyroid glands were affected during surgery, followed by a decrease in the level of ionized calcium in the blood. Management of such patients presents certain difficulties. A clinical case of examination and treatment of a patient with bilateral impairment of mobility of the vocal folds resulting from thyroid surgery is presented. The peculiarity of this observation is that because of our treatment, we managed to stop the spasm of one vocal fold, and then restore the mobility of the other vocal fold, due to which a complete restoration of the respiratory and vocal function was achieved.

Computational analysis of six optical coherence tomography systems for vocal fold imaging: A comparison study.

OBJECTIVES: There have been many advancements in laryngeal imaging using optical coherence tomography (OCT), with varying system design and probes for use in research, office, and operating room settings. We evaluated the performance of six distinct OCT systems in imaging porcine vocal folds (cords) using computational image processing and segmentation. METHODS: Porcine vocal folds were scanned using six OCT systems. Imaging system and probe performance were quantitatively assessed for signal penetration, layer differentiation, and epithelium (EP) measurement. Fitted exponential decay curves with corresponding α constant and intensity thresholding segmentation were utilized to quantify the aforementioned parameters. RESULTS: The smallest average α constant and deepest signal penetration was of the SS-OCT 1700 nm 90 kHz microscope system (α = -1.74), followed by the SS-OCT 1310 nm 200 kHz VCSEL microscope system (α = -1.99), and SS-OCT 1310 nm 50 kHz rigid forward viewing endoscope system (α = -2.23). The EP was not readily visualized for three out of six systems, but was detected using automated segmentation. Average EP thickness (mean ± SD) was calculated as 55.79 ± 31.86 µm which agrees favorably with previous literature. CONCLUSION: Comparisons of OCT systems are challenging, as they encompass different probe design, optical path, and lasers, depending on application. Practical evaluation of different systems using computer based quantitative image processing and segmentation revealed basic, constructive information, such as EP measurements. To further validate the comparisons of system performance with clinical usability, in vivo human laryngeal imaging will be conducted. Further development of automated image processing and segmentation can be useful in rapid analysis of information. Lasers Surg. Med. 51:412-422, 2019. © 2019 Wiley Periodicals, Inc.

Assessment of vocal fold mobility using dynamic magnetic resonance imaging and ultrasound in healthy volunteers.

PURPOSE: To verify the value of dynamic magnetic resonance imaging (MRI) sequences, fast field echo (FFE), and balanced gradient echo (true fast imaging with steady-state free precession - TRUFI) in the evaluation of vocal fold mobility in healthy volunteers, against ultrasound examination (US) as the reference test. MATERIAL AND METHODS: Vocal fold mobility in 35 healthy volunteers (age 20-59 years, 20 women and 15 men) with no history of laryngeal disorders and neck surgeries was determined by means of US and MRI during normal breathing and phonation of the "hiiii" sound. US images were used to determine the glottic angles. During MRI two dynamic sequences, fast field echo and balanced gradient echo, were applied to determine the minimum and maximum values of the glottic angles, along with the rima glottidis area, separately for the right and left compartments. Due to differences in larynx anatomy, the abovementioned parameters were analysed separately for women and men. RESULTS: No significant differences were observed between the glottic angle values obtained during US and dynamic MRI (FFE and TRUFI sequences). Regardless of the dynamic MRI sequence used, a positive correlation was found between the maximum values of glottic angle and the rima glottidis area. This correlation was strong and statistically significant among men, but not in women. CONCLUSIONS: Dynamic MRI of vocal folds using FFE and TRUFI sequence is an accurate method for the objective evaluation of rima glottidis width.

The remarkable vocal anatomy of the koala (Phascolarctos cinereus): insights into low-frequency sound production in a marsupial species.

Koalas are characterised by a highly unusual vocal anatomy, with a descended larynx and velar vocal folds, allowing them to produce calls at disproportionately low frequencies. Here we use advanced imaging techniques, histological data, classical macroscopic dissection and behavioural observations to provide the first detailed description and interpretation of male and female koala vocal anatomy. We show that both males and females have an elongated pharynx and soft palate, resulting in a permanently descended larynx. In addition, the hyoid apparatus has a human-like configuration in which paired dorsal, resilient ligaments suspend the hyoid apparatus from the skull, while the ventral parts tightly connect to the descended larynx. We also show that koalas can retract the larynx down into the thoracic inlet, facilitated by a dramatic evolutionary transformation of the ventral neck muscles. First, the usual retractors of the larynx and the hyoid have their origins deep in the thorax. Secondly, three hyoid muscles have lost their connection to the hyoid skeleton. Thirdly, the genioglossus and geniohyoid muscles are greatly increased in length. Finally, the digastric, omohyoid and sternohyoid muscles, connected by a common tendinous intersection, form a guiding channel for the dynamic down-and-up movements of the ventral hyoid parts and the larynx. We suggest that these features evolved to accommodate the low resting position of the larynx and assist in its retraction during call production. We also confirm that the edges of the intra-pharyngeal ostium have specialised to form the novel, extra-laryngeal velar vocal folds, which are much larger than the true intra-laryngeal vocal folds in both sexes, but more developed and specialised for low frequency sound production in males than in females. Our findings illustrate that strong selection pressures on acoustic signalling not only lead to the specialisation of existing vocal organs but can also result in the evolution of novel vocal structures in both sexes.

Shear Wave Elastography to Assess False Vocal Folds in Healthy Adults: A Feasibility Study.

OBJECTIVES: The aim of the study was to investigate the feasibility of using ultrasound shear wave elastography to quantify mechanical properties and movement symmetry of false vocal folds positioned in adduction and abduction. METHODS: We prospectively measured the shear wave velocity (SWV) within the bilateral false vocal folds in 10 healthy adults using acoustic radiation force impulse imaging. From a transcutaneous approach at the level of thyroid cartilage, 5 SWV measurements were obtained within each side of the false vocal folds twice in adduction and again in abduction for each participant. Configuration-related differences in the SWV within false vocal folds were compared between adduction and abduction, in addition to differences between the right and left false vocal folds and between men and women, by a paired t test. We developed an SWV index [(SWVgreater - SWVlesser )/SWVgreater ] to assess movement symmetry between the right and left false vocal folds. Intraobserver agreement on repeated measures was examined by the intraclass correlation coefficient. RESULTS: The 10 participants included 5 men and 5 women. We observed that the SWV within false vocal folds was significantly higher in adduction than in abduction (P < .001). The SWV within false vocal folds in adduction was also significantly higher in women compared to men (P < .001). There was no significant difference in the SWV between the right and left false vocal folds in adduction or in abduction or between men and women in abduction (P > .05). The mean SWV index was 0.05 (range, 0.03-0.07). The intraclass correlation coefficient for intraobserver agreement was 0.89 (P < .001). CONCLUSIONS: Shear wave elastography seems to be feasible to quantify mechanical properties and evaluate the symmetry of false vocal folds in healthy adults.