Development of laryngeal video stroboscope with laser marking module for dynamic glottis measurement

doi:10.1016/j.compmedimag.2013.10.004

Computerized Medical Imaging and Graphics

Volume 38, Issue 1, January 2014, Pages 34-41

https://doi.org/10.1016/j.compmedimag.2013.10.004 Get rights and content

Abstract

Physicians clinically use laryngeal video stroboscope as an auxiliary instrument to test glottal diseases, and read vocal fold images and voice quality for diagnosis. As the position of vocal fold varies in each person, the proportion of the vocal fold size as presented in the vocal fold image is different, making it impossible to directly estimate relevant glottis physiological parameters, such as the length, area, perimeter, and opening angle of the glottis. Hence, this study designs an innovative laser projection marking module for the laryngeal video stroboscope to provide reference parameters for image scaling conversion. This innovative laser projection marking module to be installed on the laryngeal video stroboscope using laser beams to project onto the glottis plane, in order to provide reference parameters for scaling conversion of images of laryngeal video stroboscope.

Introduction

Communication of people is directly related with the vocal sound. Vocal fold is the membranous structure of two symmetrical folds in the throat. In breathing, the vocal folds open to allow the lung to exchange air. In vocal actions such as speaking and singing, vocal fold will vibrate to make sound through the interaction with air. Glottis is the opening between the two sections of the vocal fold, and the size of glottis opening is subjected to the control of the vocal fold. When the air pressed out of the lung passes through glottis to impact the vocal fold, the sound is produced. Then, the adjustment of vocal fold will change the pitch and loudness of the sound. As human expressions by sound are very complex, the focus of phonetic medical research is to understand the sound making process, the causes of phonetic-related diseases and avoid voice injury.

At present, the diagnosis of glottal health and disease is mainly judged by images of laryngeal video stroboscope as shown in Fig. 1. Due to the individual difference in throat structure, it may easily lead to differences in subjective recognition because of different viewpoints of physicians. Regarding the clinical observation of vocal fold actions and glottis appearance, there is a lack of objective digitalized descriptions such as the area of glottis, the length of vocal fold, the perimeter of the vocal fold, etc. The currently available digital image processing technology identifies image characteristic values through various algorithm rules to identify specific areas. However, since digital image is composed of pixels, it is not easy to intuitively match with common measurement units. The major difficulty in conversion is caused by the different position of vocal fold. Due to the optical effects of laryngeal video stroboscope lens, the size proportions of presented digital glottis images may be different, resulting in misjudgment of data. Hence, to convert the length and area of glottis into general length and area units, it requires reliable scaling conversion references to learn the corresponding relationship between image pixels and length unit.

Section snippets

Literature review

Clinically, vocal fold disorders can be identified by investigation. Among various syndromes, raucous vocal folds are very common. Airflow induced by glottis atresia and irregular vibration of vocal folds are two main causes, which are mutually independent. So Eysholdt et al. [1] proposed using high-speed glottography (HGG) and quantification of irregular vibration of vocal folds, combining laryngeal video stroboscope and image processing, to locate the motion curve of each vocal fold. Airflow

Experimental design and verification

This laser projection marking module is installed on the laryngeal video stroboscope using laser beams to project onto the glottis plane, in order to provide reference parameters for scaling conversion of images for laryngeal video stroboscope. The device design is different from Schade's work in Reference [7]. Schade designed a clip-on device to the laryngoscope. In this paper, the laser fixture and spectroscope are installed at the rear end of the laryngeal video stroboscope, and the laser

Conclusions

Laryngeal video stroboscope is widely used in clinical tests to help physicians to directly observe voice disorders or location of diseased parts. Since the distance of using laryngeal video stroboscope to test the glottis varies from person to person, there is no standard for judging the proportions of glottis images. This study designed the laser projection marking module to guide the laser beams passing through spectroscope and reflection lens for projection onto the glottis images. The

Conflict of interest

The authors certify that none of the authors have any financial and personal relationships with any other people or organizations that could inappropriately influence (bias) their work.

Acknowledgement

The authors wish to thank the reviewers for their valuable comments.

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Usage of the device is not significantly different from that used in conventional endoscopic examinations. We made modifications to Schade's and our previous work.5,6 Two parallel laser beams, with a distance of 1mm, were obtained from a green dot laser by the beam splitter, to provide the scaling reference.
Qualitative laryngoscopy belongs to a diagnostic routine. Nevertheless, quantitative morphometric measurements of laryngeal structures remain challenging. This study aimed to introduce a special laser projection device that can facilitate computer-assisted digitalized analysis and provide important quantitative information for diagnostics and treatment planning.
The laryngeal images were captured with our device, which contained two parallel laser beams in order to provide the scaling reference. The maximum length of the vocal fold during respiration and vibration (phonation), vocal width at midpoint, total fold area, maximum cross-sectional area of the glottic space, and maximum vocal fold angle were determined and calculated. These parameters were analyzed and compared on the basis of age, sex, body height, body weight and body mass index.
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