Three-dimensional imaging of the larynx for pre-operative planning of laryngeal framework surgery

Analysis of Dysphagia and Cough Strength in Patients with Unilateral Vocal Fold Paralysis

The association between swallowing function and cough strength in patients with unilateral vocal fold paralysis (UVFP) is unknown. We evaluated the relationship between voluntary cough strength and dysphagia among patients with UVFP (UVFP group) by comparing their data with that of corresponding healthy participants (healthy control [HC] group) in a prospective observational study. From February 1st, 2018 to March 30th, 2019, we recruited patients with a voice disorder due to UVFP, who were referred to our university hospital. Patients with a history of laryngeal surgery, vagal nerve paralysis, or cardiac and respiratory failure were excluded. Descriptive and clinical data regarding swallowing, voice, and cough peak flow (CPF) were collected as a measure of cough strength. The UVFP group comprised six women and seven men (median age, 68.0 years), and the HC group comprised six women and eight men (median age 65.5 years). The groups differed significantly in the Eating Assessment Tool (EAT)-10 scores and CPF rates (P < 0.001). Among patients with UVFP, 84.6% had an abnormal EAT-10 score of ≥ 3. Additionally, 16.7% of the patients exhibited liquid aspiration with contrast medium on a videofluorographic swallowing study (VFSS). There was no correlation between the CPF values, EAT-10 scores, or the VFSS results. Therefore, patients with severe UVFP, whose condition had been fixed, had difficulties when swallowing (85% of cases), and some even presented with aspiration on VFSS (20% of cases), while receiving a regular diet.

Three-dimensional imaging of vocalizing larynx by ultra-high-resolution computed tomography

PURPOSE

Ultra-high-resolution computed tomography (UHRCT) is an emerging imaging technology that is able to achieve simultaneous 160 slices with super-thin 0.25 mm thickness. The purpose of this study was to assess the feasibility of UHRCT to visualize laryngeal structure and kinetics.

METHODS

Three normal volunteers and three patients with unilateral vocal fold paralysis (UVFP) were incorporated in this case series. First, images were taken under five conditions in normal volunteers. Five tasks consisted of (1) air inspiration through the nose (IN), (2) breath holding (BH), (3) sustained vowel /i:/ phonation (IP), (4) humming phonation (HP), and (5) forced glottic closure during exhalation (FC). Three-dimensional CT images of arytenoid and cricoid cartilages, as well as virtual laryngoscopic images, were reconstructed using UHRCT data. Reconstructed images were compared among five conditions to assess the best tasks to picture laryngeal kinetics. Second, pre- and post-phonosurgical images were examined in UVFP patients to evaluate potential role of UHRCT to assess laryngeal pathology in hoarse patients.

RESULTS

Among the five conditions, IN and IP conditions were considered suitable to visualize laryngeal structure at rest and during phonation, respectively. Kinetic abnormalities including asymmetric motion of arytenoid cartilages were elucidated in UVFP patients, and virtual endoscopy visualized the clinically invisible posterior three-dimensional glottic chinks. Furthermore, UHRCT was useful to understand changes in laryngeal structure achieved by phonosurgery.

CONCLUSIONS

UHRCT is an emerging imaging technology that can be used for minimally invasive visualization and assessment of laryngeal structure and kinetics. Future studies to assess more number of patients with laryngeal dysfunction are warranted.

Changes in Vocal Fold Morphology During Singing Over Two Octaves

OBJECTIVE

Vocal folds are widely assumed to only elongate to raise vocal pitch. However, the mechanisms seem to be more complex and involve both elongation and tensioning of the vocal folds in series. The aim of the present study was to show that changes in vocal fold morphology depend on vocal fold elongation and tensioning during singing.

STUDY DESIGN

This was a prospective study.

METHODS

Forty-nine professional female singers (25 sopranos, 24 altos) were recruited and three-dimensional laryngeal images analyzed in a coronal view derived from high-resolution computed tomography scans obtained at the mean speaking fundamental frequency (ƒ₀) and one (2ƒ₀) and two octaves (4ƒ₀) above ƒ₀.

RESULTS

The vocal fold angle, defined by a tangent above and below the vocal folds, was 58° at ƒ₀, 47° at 2ƒ₀, and 59° at 4ƒ₀.

CONCLUSION

The decreased caudomedial angle of the vocal fold from ƒ₀ to 2ƒ₀ (change in muscle belly from ";fat" to "thin") and increased angle from 2ƒ₀ to 4ƒ₀ (from "thin" to "fat") strongly supports the hypothesis that the vocal folds elongate and then tension when singing from ƒ₀ to 4ƒ₀. This is the first study to show this relationship in vivo.

The Cricothyroid Joint: A Practical Guide for Distinguishing Between Different Joint Types

OBJECTIVE

Type A cricothyroid joint (CTJ) leads to a higher elongation of the vocal folds than Type B/C CTJ. Therefore, the determination for the CTJ type is important whether to perform a cricoid-thyroid approximation for a pitch elevation in transwomen with gender dysphoria. This study aimed to develop a tool for clinicians and radiologists for distinguishing between Type A (cricoid cartilage protuberance) and Type B/C (flat surface with/without cartilage of the cricoid) CTJs on high-resolution computed tomography (HRCT).

STUDY DESIGN

This was a prospective study.

METHODS

Analysis of 60 male HRCTs and 60 female HRCTs of the larynx/CTJs. Three-dimensional reconstruction of the laryngeal cartilages, based on visualization of the CTJ in HRCT scans. The intercartilaginous distances (nearest distance between the inner side of the Thyroid and outer side of the cricoid of the CTJ) were measured to compare different types of CTJs.

RESULTS

In all HRCT scans, three-dimensional reconstructions of the CTJ were feasible. All Type A CTJs showed the typical cricoid cartilage protuberance (like a volcano) in biplanar images and three-dimensional reconstructions. All Type B/C CTJs showed a flat cricoid joint cartilage in biplanar images and three-dimensional reconstructions. The type distribution was Type A: 61% in male and female larynges; Type B/C: 39% in male and female larynges. The intercartilaginous distances were Type A: 0.71 mm [0.42-0.98] in male larynges and 0.75 mm [0.44-1.40] in female larynges; Type B/C: 1.13 mm [0.36-1.24] in male larynges and 1.32 mm [0.76-2.47] in female larynges.

CONCLUSIONS

In HRCT scans, the Type A CTJ showed an intercartilaginous space less than 1 mm. In contrast, the Type B/C CTJ showed an intercartilaginous distance exceeded 1 mm.

3D multiscale imaging of human vocal folds using synchrotron X-ray microtomography in phase retrieval mode

Human vocal folds possess outstanding abilities to endure large, reversible deformations and to vibrate up to more than thousand cycles per second. This unique performance mainly results from their complex specific 3D and multiscale structure, which is very difficult to investigate experimentally and still presents challenges using either confocal microscopy, MRI or X-ray microtomography in absorption mode. To circumvent these difficulties, we used high-resolution synchrotron X-ray microtomography with phase retrieval and report the first ex vivo 3D images of human vocal-fold tissues at multiple scales. Various relevant descriptors of structure were extracted from the images: geometry of vocal folds at rest or in a stretched phonatory-like position, shape and size of their layered fibrous architectures, orientation, shape and size of the muscle fibres as well as the set of collagen and elastin fibre bundles constituting these layers. The developed methodology opens a promising insight into voice biomechanics, which will allow further assessment of the micromechanics of the vocal folds and their vibratory properties. This will then provide valuable guidelines for the design of new mimetic biomaterials for the next generation of artificial larynges.

Surgical Impact of the Montgomery Implant System on Arytenoid Cartilage and the Paralyzed Vocal Fold

OBJECTIVES/HYPOTHESIS

Medialization thyroplasty (MT) has become a prominent method for treating glottal insufficiency. This study aimed to visualize the biomechanical influence of a medialization implant on arytenoid cartilage, particularly on the length and level of paralyzation in the vocal fold, in patients with unilateral vocal fold paralysis.

STUDY DESIGN

Prospective study.

METHODS

We recruited 15 patients (10 men, 5 women) with unilateral vocal fold paralysis that underwent MT with a Montgomery® thyroplasty implant. We performed high-resolution computed tomography of the arytenoid cartilage before and after MT and analyzed the three-dimensional images. To visualize the movement of the arytenoid and to measure the lengthening of the vocal fold, we superimposed pre- and postoperative 3D images with MIMICS software.

RESULTS

On the affected side, the implant pushed the arytenoid backwards. In addition, the vocal process of the arytenoid was inwardly rotated. These movements resulted in an elongated, augmented vocal fold on the affected side.

CONCLUSION

MT led to an elongated, medialized vocal fold on the treated side. After the intervention, the vocal folds on both sides were the same length in the phonatory position.

How Age and Frequency Impact the Thyroid Cartilages of Professional Singers

OBJECTIVES/HYPOTHESIS

Young professional singers can easily reach very high pitches. In contrast, older singers often complain that they have to exert substantially more laryngopharyngeal force to reach the same high pitch compared with their earlier years. Various factors such as the property changes of the mucosa and ossification that impact the singing apparatus were suggested as explanations in the literature. The aim of this study was to analyze thyroid deformation-and thereby stiffness indirectly-during singing as a potential reason for this phenomenon.

STUDY DESIGN

Prospective study.

METHODS/DESIGN

We examined 44 female professional singers. High-resolution computed tomography scans were performed during singing at the fundamental mean speaking frequency and the first and second octaves above it. Digital Imaging and Communications in Medicine scan data were rendered and visualized 3-dimensionally using MIMICS software. By superimposition of the different 3-dimensional images, different positions of the thyroid were visualized. The distance from the posterior border of the thyroid was measured in all the examinations.

RESULTS

All laryngeal cartilages could be three-dimensionally visualized. The magnitude of the thyroidal deformation significantly depends on pitch and significantly correlates with age (r² = 0.7, P < 0.001).

CONCLUSIONS

The thyroid cartilage is flexible and its formability is especially important during singing. At higher pitches, the cartilage was more deformed. The larynx in older singers showed less thyroid cartilage deformation.

Automated setup for ex vivo larynx experiments

Ex vivo larynx experiments are limited in time due to degeneration of the laryngeal tissues. In order to acquire a significant and comparable amount of data, automatization of current manual experimental procedures is desirable. A computer controlled, electro-mechanical setup was developed for time-dependent variation of specific physiological parameters, including adduction and elongation level of the vocal folds and glottal flow. The setup offers a standardized method to induce defined forces on the laryngeal cartilages. Furthermore, phonation onset is detected automatically and the subsequent measurement procedure is automated and standardized to improve the efficiency of the experimental process. The setup was validated using four ex vivo porcine larynges, whereas each validation measurement series was executed with one separate larynx. Altogether 31 single measurements were undertaken, which can be summed up to a total experimental time of about 4 min. Vocal fold elongation and adduction lead both to an increase in fundamental frequency and subglottal pressure. Measurement procedures like applying defined subglottal pressure steps and onset-offset detection were reliably executed. The setup allows for a computer-based parameter control, which enables fast experimental execution over a wide range of laryngeal configurations. This maximizes the number of measurements and reduces personal effort compared with manual procedures.

Two-dimensional sectioned images and three-dimensional surface models for learning the anatomy of the female pelvis

In the Visible Korean project, serially sectioned images of the pelvis were made from a female cadaver. Outlines of significant structures in the sectioned images were drawn and stacked to build surface models. To improve the accessibility and informational content of these data, a five-step process was designed and implemented. First, 154 pelvic structures were outlined with additional surface reconstruction to prepare the image data. Second, the sectioned and outlined images (in a browsing software) as well as the surface models (in a PDF file) were placed on the Visible Korean homepage in a readily-accessible format. Third, all image data were visualized with interactive elements to stimulate creative learning. Fourth, two-dimensional (2D) images and three-dimensional (3D) models were superimposed on one another to provide context and spatial information for students viewing these data. Fifth, images were designed such that structure names would be shown when the mouse pointer hovered over the 2D images or the 3D models. The state-of-the-art sectioned images, outlined images, and surface models, arranged and systematized as described in this study, will aid students in understanding the anatomy of female pelvis. The graphic data accompanied by corresponding magnetic resonance images and computed tomographs are expected to promote the production of 3D simulators for clinical practice.

Anatomical education and surgical simulation based on the Chinese Visible Human: a three-dimensional virtual model of the larynx region

Anatomical knowledge of the larynx region is critical for understanding laryngeal disease and performing required interventions. Virtual reality is a useful method for surgical education and simulation. Here, we assembled segmented cross-section slices of the larynx region from the Chinese Visible Human dataset. The laryngeal structures were precisely segmented manually as 2D images, then reconstructed and displayed as 3D images in the virtual reality Dextrobeam system. Using visualization and interaction with the virtual reality modeling language model, a digital laryngeal anatomy instruction was constructed using HTML and JavaScript languages. The volume larynx models can thus display an arbitrary section of the model and provide a virtual dissection function. This networked teaching system of the digital laryngeal anatomy can be read remotely, displayed locally, and manipulated interactively.

Portable document format file showing the surface models of cadaver whole body

In the Visible Korean project, 642 three-dimensional (3D) surface models have been built from the sectioned images of a male cadaver. It was recently discovered that popular PDF file enables users to approach the numerous surface models conveniently on Adobe Reader. Purpose of this study was to present a PDF file including systematized surface models of human body as the beneficial contents. To achieve the purpose, fitting software packages were employed in accordance with the procedures. Two-dimensional (2D) surface models including the original sectioned images were embedded into the 3D surface models. The surface models were categorized into systems and then groups. The adjusted surface models were inserted to a PDF file, where relevant multimedia data were added. The finalized PDF file containing comprehensive data of a whole body could be explored in varying manners. The PDF file, downloadable freely from the homepage (http://anatomy.co.kr), is expected to be used as a satisfactory self-learning tool of anatomy. Raw data of the surface models can be extracted from the PDF file and employed for various simulations for clinical practice. The technique to organize the surface models will be applied to manufacture of other PDF files containing various multimedia contents.

A transthyroidal method for arytenoid adduction: a basic anatomical study

INTRODUCTION

Arytenoid adduction is a very effective procedure for medializing the posterior part of the vocal fold in vocal fold paralysis. Major drawback of the method is the technically sometimes-difficult access to the arytenoid with increased postoperative morbidity. Aim of this study was to provide basic anatomical data regarding the accessibility of the arytenoid cartilage through a thyroplasty window. Furthermore, to investigate the feasibility of an arytenoid adduction by fixation of a surgical screw to the arytenoid cartilage by using this approach.

MATERIALS AND METHODS

10 cadaver larynges, six female and four male, were dissected and measured for our points of interest. A standard manufacture-made surgical screw attached to a suture was anchored to the fovea oblonga of the arytenoid cartilage.

RESULTS

Our anatomical measurements proved a mean distance from the posterior edge of the thyroid window to the arytenoid of about 8-9 mm in male larynges and 7-8 mm in female larynges. The distances did not differ significantly between the sexes. Pulling the anchored surgical screw medializes the posterior part of the vocal fold.

DISCUSSION

Our data showed that there is a very constant morphometric relation between the thyroplasty window and the arytenoid cartilage. It is known that gender-related differences result in a veritable laryngeal dimorphism in nearly all absolute laryngeal dimensions. These differences appear to a much lesser extend in the distances from the surface to the depth, as was confirmed in our series. Using these findings led us to identification of the fovea oblonga near the muscular process as the most favorable point for fixation of a surgical screw through a conventional thyroplasty window. Pulling the attached suture medializes the arytenoid cartilage.

Developing a 3D model of the laryngeal cartilages using HRCT data and MIMICS's segmentation software

Discussions relating to the biomechanics of the larynx are still generally controversial. The purpose of this study is to develop a 3D model of the larynx based on high-resolution computer tomography (HRCT) data identifying and visualizing anatomical landmarks and structures of the larynx. We examined four fresh cadaver larynges with HRCT. The DICOM (Digital Imaging and Communication in Medicine) data were post-processed with the software package MIMICS for three-dimensional visualization. All relevant structures of the laryngeal cartilages could be identified on HRCT and visualized in a 3D model. We conclude that 1) HRCT provides excellent data for three-dimensional visualization of the laryngeal anatomy, and 2) the combined technology of HRCT and MIMICS is useful to study the biomechanics on 3D images and for preoperative planning of laryngeal framework surgery.