Three-dimensional Imaging of High-resolution Computer Tomography of Singers' Larynges—A Pilot Study

An Old Myth: Prediction of the Correct Singing Voice Classification. True or not?

OBJECTIVE

Predicting the correct singing voice classification based on laryngoscopy is an old myth. The aim of this study was to evaluate if a professional phoniatrician/laryngologist can predict the correct singing voice classification only from laryngoscopy and to analyze different anatomical parameters between professional sopranos and altos to determine whether a multivariate analysis of anatomical parameters can predict the singing register.

STUDY DESIGN

Prospective study METHODS: We included 49 professional female singers (25 sopranos, 24 altos). Laryngoscopic images were shown to professional phoniatricians/laryngologists to rate whether it they show a soprano or an alto. In addition, a high-resolution computer tomography (HRCT) scan was performed during singing of ƒ0 by each singer. DICOM scan data were rendered and 3D-visualized using the software MIMICS. In all singers, we measured the length of the vocal folds of the glottis, the distance from the anterior commissure orthogonally to the vertebral spine, and the antero-posterior distance of the subglottis/trachea 1 cm and 2 cm below the glottis. We also measured the length and volume of the resonance space.

RESULTS

It was not possible to predict the singing voice classification only from laryngoscopy. In the HRCT images, sopranos had significantly shorter vocal folds, a shorter glottal length, a shorter distance from the anterior commissure to the spine, and a shorter resonance space. When combining all parameters, the chance of correctly predicting a soprano was 74.1% and an alto 68.2%.

CONCLUSION

Although there are anatomical differences between sopranos and altos, prediction of the singing voice classification from laryngoscopy or HRCT is not reliable enough for clinical use.

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.

Computed Tomography Data to Generate a Reproducible, Anatomically Accurate Hemilaryngeal Model

Objective

The study aims to demonstrate the reproducibility and feasibility of creating a hemilaryngeal model with a medialized vocal fold (VF) using 3-dimensional (3D) modeling techniques in both healthy larynges and those affected by cancer.

Study Design

Three-dimensional modeling of human larynges.

Setting

Tertiary academic referral center and regenerative medicine laboratory.

Subjects and Methods

Computed tomography (CT) scans from 10 healthy control and 10 patients with laryngeal cancer were segmented and imported into 3D modeling software. The larynx was cut sagittally to create a hemilaryngeal model and the vocal fold medialized. Measurements were taken from the CT and 3D model data and compared.

Results

All control modeling data closely matched the CT data and were not statistically different from each other. There was a significant correlation between subglottic anteroposterior diameter and VF length ( r2 = 0.78, P = .0008), and it may be a valuable tool to infer true VF dimension in cases where disruption has occurred. The modeling data from patients with cancer did not show statistical difference to the control data, showing that accurate modeling can also be achieved in patients with laryngeal cancer.

Conclusion

CT scan-based 3D modeling of the larynx and VF is possible and reproducible. The results closely match those previously reported in the literature and can also be replicated in cases with laryngeal cancer. This study paves the way for future de novo fabricated laryngeal scaffolds that can be synthesized using 3D printers and tailored to meet surgical demands.

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.

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.

The larynx ruler to measure height and profile of vocal folds: a proof of concept

INTRODUCTION

Glottic leakage during phonation is a direct consequence of unilateral vocal fold (VF) paralysis. This air leakage can be in the horizontal plane and in the vertical plane. Presently, there is no easily applicable medical device allowing noninvasive, office-based measurement of the relative vertical position of the VFs. The larynx ruler (LR) is a laser-based measuring device that could meet the previously stated need, using a flexible endoscope. This study represents a proof of concept regarding the use of the LR in assessing VF relative positions in the vertical plane.

MATERIALS AND METHODS

One fresh male human cadaver larynx, free of neurologic and anatomic disease, was explored with the LR system through the operative channel of a flexible gastroenterology video-endoscope. The tip of the video-endoscope was located in the laryngeal vestibule. The right crico-arytenoid joint was posteriorly disarticulated. Tilting of the VF was obtained by pulling or pushing the arytenoid cartilage with a mosquito forceps fixed to the stump of the previously sectioned superior tip of the posterior crico-arytenoid muscle allowing anterior and posterior tilting of the arytenoid cartilage in order to induce an elevation or a depression of the VF process. Ten "push" and ten "pull" sessions were performed. The distance from the tip of the video-endoscope to each illuminated pixel of the laser beam was recorded. The level difference between the left and right VFs was measured for each recording.

RESULTS

Data provided by the LR were consistently in accordance with the movements applied on the VFs. The accuracy of 0.2 mm of the LR is compatible with the envisioned applications for the human larynx.

CONCLUSION

The LR system represents a feasible technique to evaluate respective vertical position of VFs in the human larynx. Technical limitations were identified that will require improvements before experimental use on human beings.