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A new videokymography system for evaluation of the vibration pattern of entire vocal folds
Auris Nasus Larynx 43 (2016) 315–321 Contents lists available at ScienceDirect
Auris Nasus Larynx journal homepage: www.elsevier.com/locate/anl
A new videokymography system for evaluation of the vibration pattern of entire vocal folds Soo-Geun Wang a, Hee-June Park a, Byung-Joo Lee a, Sung-Mo Lee b, Bumjun Ko c, Sang Min Lee c, Young Min Park c,* a Department of Otorhinolaryngology-Head and Neck Surgery, Pusan National University School of Medicine and Biomedical Research Institute, Busan, Republic of Korea b Lee Sung Mo Internal Medicine Clinic, Busan, Republic of Korea c Department of Otorhinolaryngology, Bundang Jesaeng Hospital, Deajin Medical Center, Seongnam, Gyeonggi, Republic of Korea
A R T I C L E I N F O
A B S T R A C T
Article history: Received 11 August 2015 Accepted 16 October 2015 Available online 18 November 2015
Objective: To overcome the limitations of previous videokymography methods, we developed a new videokymography system for the evaluation of the whole mucosal wave of the entire vocal cord mucous membrane. Methods: To confirm the usefulness of the new videokymography system, we performed videokymography to evaluate the mucosal wave of the vocal folds during modal and falsetto phonation in normal adult males. Additionally, we serially performed both laryngeal videostroboscopy and the new videokymography method in patients diagnosed with acute ulcerative laryngitis. Results: Using the new videokymography system, the mucosal wave pattern of entire vocal folds was captured during the examination. The opening and closing durations could be differentiated, and the symmetry of amplitude and phase could be assessed. The shape of the medial and lateral peaks could be assessed. In patients with acute laryngitis, the new videokymography system showed an enhanced ability to evaluate the flexibility of the vocal folds. Conclusion: The new videokymography system enables recording of the whole mucosal wave pattern of entire vocal folds. Although further studies are required to confirm its clinical efficacy for the evaluation of vocal folds, the system can be applied to evaluate the static and dynamic status of vocal folds in patients with vocal cord diseases. ß 2015 Elsevier Ireland Ltd. All rights reserved.
Keywords: Videokymography Vocal cord Vibration
1. Introduction For the physical examination of patients with voice change complaints, it is important to assess the static and dynamic status of the vocal folds. Using a laryngeal endoscope,
* Corresponding author at: Department of Otorhinolaryngology, Bundang Jesaeng Hospital, Deajin Medical Center, Seohyeon-ro 180, Bundang-gu, Seongnam, Gyeonggi, Republic of Korea. Tel.: +82 10 4230 3725; fax: +82 31 779 0265. E-mail address: [email protected] (Y.M. Park). http://dx.doi.org/10.1016/j.anl.2015.10.002 0385-8146/ß 2015 Elsevier Ireland Ltd. All rights reserved.
otolaryngologists can evaluate the structural abnormalities and mobility of the vocal folds. However, the dynamic abnormalities of the vocal folds could not be detected on laryngeal endoscopy in some patients with voice change complaints [1]. In these patients, the vibration pattern of the vocal folds should be assessed. For humans to produce voice, the vocal folds must vibrate rapidly at a frequency of 70–1000 Hz, although the frequency differs according to sex [1]. However, conventional laryngeal endoscopy cannot assess the mucosal wave of the vocal folds due to the image processing speed (50–60 images/s) [1].
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S.-G. Wang et al. / Auris Nasus Larynx 43 (2016) 315–321
Although the vibration pattern of the vocal folds can be observed using optical illusory slow motion with a stroboscope, this is possible only in patients with a periodic vibration pattern [1,2]. By contrast, a high-speed imaging system can observe the mucosal wave of the vocal folds irrespective of vibration periodicity. However, its use is not widespread because of the high cost [3]. Although Svec et al. developed the videokymography (VKG) system to examine the mucosal wave of the vocal folds located on a fixed line, the mucosal wave of the entire vocal folds could not be observed in a single recording [1,4]. As mentioned above, various imaging techniques were developed to assess the mucosal wave pattern of the vocal folds. However, as each system has its advantages and disadvantages, they are used clinically in a complementary manner. To analyze the mucosal wave pattern of the entire vocal folds in a single recording, we developed a specific CCD video system and produced a new VKG system equipped with a CCD video sensor [5]. Use of this new VKG system to evaluate the vibration pattern of the vocal folds results in two types of image of the vocal folds being obtained (laryngeal endoscopic image and videokymographic image). Unlike the previous VKG system devised by Svec et al., our VKG system enables evaluation of the whole mucosal wave pattern of the entire vocal folds during a single examination. To confirm its clinical usefulness, the VKG system was used to evaluate the mucosal wave pattern of the vocal folds during falsetto and modal phonation of normal adult males. Additionally, VKG was serially applied to patients with acute laryngitis to evaluate the dynamic healing status of their vocal folds. 2. Materials and methods 2.1. Subjects The Institutional Review Board of Pusan National University Hospital approved this study (#E-2015105). We invented a specific CCD video system and produced a new VKG system equipped with a CCD video system to evaluate the mucosal wave pattern of entire vocal folds. The new VKG system was applied to evaluate the vibration pattern of the vocal folds in two subjects. One subject (P.H.J.) produced falsetto and modal phonation, and the vibration pattern of his vocal folds was examined using the new VKG system. The other subject (L.S.M.) was diagnosed with acute ulcerative laryngitis, and volunteered to undergo both laryngeal videostroboscopy and the new VKG method for the evaluation of disease status. The examinations were performed serially after the commencement of treatment. To confirm the usefulness of our system, stroboscopy and modified VKG were performed simultaneously during the follow-up period. 2.2. Principle of the new VKG system The previous VKG system devised by Svec et al. can record images from a single selected line (Fig. 1). Therefore, it is possible to increase the rate of images captured and recorded per second at the expense of spatial information. However, the slit of the rolling shutter was not fixed in one place in the new VKG system, instead it moved forward along the vocal folds
Fig. 1. Principle of the new VKG system. Using the previous VKG system, only one portion of the vocal folds located on a fixed line (black line) was evaluated during the examination. In the new VKG system, the slit of the rolling shutter moved forward (black arrow) along the vocal folds during the examination. Therefore, the whole mucosal wave of the entire vocal folds could be assessed in a single examination.
(Fig. 1). During extended-length examination, it continues to move back and forth repeatedly. Therefore, the whole mucosal wave of the entire vocal folds was observed and recorded in a single examination, and characteristic videokymographic images were obtained. 2.3. Configuration of the new VKG system A complementary metal-oxide semiconductor (CMOS) video sensor and rolling shutter were used to obtain the videokymographic images of the entire vocal folds. This system was designed for the acquisition of images at rates of 30 frames/s and 32,400 lines/s, which is sufficient to cover the frequency range of the vocal folds. A 300 W xenon light source (Storz Nova 300; Karl Storz, Tuttlingen, Germany) was used to provide sufficient illumination. In the previous VKG system, the entire vocal folds could not be assessed in a single examination because only one portion of the vocal folds located on a fixed line was observed. Because the slit of the rolling shutter was fixed in one place, the entire mucosal wave could be examined. By contrast, the slit of the rolling shutter of our system moved forward from the posterior portion of the vocal folds during the examination (Fig. 1). Therefore, the mucosal wave of the entire vocal folds could be assessed in a single examination. 3. Results 3.1. Videokymographic images of normal adult males Using the new VKG system, videokymographic images were obtained during phonation of normal adult males (Fig. 2).
S.-G. Wang et al. / Auris Nasus Larynx 43 (2016) 315–321
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Fig. 2. Characteristic videokymographic images generated by the new VKG system during phonation. (A) The mucosal wave pattern of the entire vocal folds was captured during a single examination. (B) The symmetry of the amplitude (arrow) could be assessed. (C) The opening (b) and closing (a) durations could be differentiated. (D and E) The shape of the medial (arrow) and lateral peaks (arrow) could be assessed.
The mucosal wave pattern of the entire vocal folds was evaluated during a single examination (Fig. 2A). The opening and closing durations could be differentiated, and the symmetry of the amplitude and phase could be assessed (Fig. 2B and C). The shape of the medial and lateral peaks could also be assessed (Fig. 2D and E). 3.2. Stroboscopic and videokymographic images in a patient with acute laryngitis Both vocal folds revealed diffuse redness with irregular mucosal edges using both imaging modalities at the first visit. The mucosal wave of the vocal folds was completely absent, and purulent discharge was observed in the larynx. In addition, a spindle-shaped gap was observed because the vocal folds could not make contact with each other (Fig. 3A and B) (Supplementary video file 1). On both imaging modalities, the patient showed slight improvement in redness and purulent discharge of both vocal
cords after 1 week. Although the gap between the cords persisted, incomplete glottis closure remained evident, as shown in Fig. 4A. However, the new VKG method, but not laryngeal videostroboscopy, revealed that the mucosal waves of both vocal cords had slightly recovered. However, the amplitude of the left cord was less than that of the right (Fig. 4B). The two imaging techniques, laryngeal videostroboscopy and the new VKG method, were performed after 4 weeks of treatment. Both showed that adduction of both vocal cords had recovered completely, and the redness and discharge had disappeared almost completely (Fig. 5A). In addition, the new VKG system showed that the mucosal waves of both cords had recovered almost completely, and the shapes of their medial peaks were normal (Fig. 5B) (Supplementary video file 2). 4. Discussion Laryngeal videostroboscopy is commonly used to evaluate vocal cord lesions. However, much experience is required to
318
S.-G. Wang et al. / Auris Nasus Larynx 43 (2016) 315–321
Fig. 3. Images obtained by laryngeal videostroboscopy (A) and the new VKG system (B) at the first visit (Supplementary video file 1).
make a definite diagnosis based only on laryngeal videostroboscopic findings. With the exception of vocal cord polyposis, which leads to a larger amplitude of mucosal waves, it is impossible to make a diagnosis based on only a single laryngeal videostroboscopy image. Although structural and functional abnormalities of the vocal cords can be evaluated using the VKG system devised by Svec et al., the entire vocal cord mucous membrane cannot be observed. Although multi-line VKG or digital VKG systems, including strobovideokymography (SVKG) and digital VKG, were developed to overcome the limitations of VKG, these methods are also limited in terms of their clinical application [6,7]. SVKG can be used to evaluate lesions at multiple horizontal segments of the vocal cord mucous membrane.
However, similar to classic laryngeal videostroboscopy, it cannot be performed in patients with aperiodic vibration. In digital VKG, kymographic images can be acquired through post-processing of captured images using software [6]. Digital VKG could additionally assess the phase difference between the anterior and posterior surfaces of the vocal cord. However, its recording time is limited, and a large amount of memory is required to save captured images. In addition, it cannot image the entire vocal cords simultaneously [6]. To overcome these limitations, we developed a new VKG system for the evaluation of the whole mucosal wave pattern of the vocal folds. As this VKG system can observe the actual vibration pattern of the entire vocal cord mucous membrane simultaneously, the distortion problems associated with the
S.-G. Wang et al. / Auris Nasus Larynx 43 (2016) 315–321
319
Fig. 4. Imaging findings of laryngeal videostroboscopy (A) and the new VKG system (B) after 1 week. The amplitude of the mucosal wave of the left vocal cord was less than that of the right vocal cord as determined by the new VKG system.
previous VKG system can be avoided. In the present study, we assessed the system’s efficacy in comparison with that of laryngeal videostroboscopy. The system successfully recorded dynamic images of the entire vocal cord mucous membrane in real-time and facilitated analysis of all mucosal movements simultaneously. In particular, the flexibility of the vocal folds could be easily evaluated using the new VKG system. When no structural abnormalities of the vocal folds are detected in patients with hoarseness, it is important to assess the flexibility of the vocal folds. Because inflammatory diseases can increase the stiffness of the lamina propria of the vocal folds due to an inflammatory reaction, the flexibility of
the vocal folds can deteriorate without remarkable gross abnormalities. Use of the new VKG system in such cases would enable the dynamic status of the vocal folds being evaluated. In the present study, we invented the new VKG system with the rolling shutter and showed the superiority of it in the analysis of dynamic movement of the vocal folds compared to stroboscopy. However, further study is required to prove clinical efficacy and superiority of it compared to traditional single line VKG. Therefore, we will perform the comparison analysis of the new VKG system and the traditional single line VKG in the future study.
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Fig. 5. Imaging findings of laryngeal videostroboscopy and the new VKG system after 4 weeks. The mucosal waves of both cords had recovered almost completely, and the shapes of their medial peaks were normal, as determined using the new VKG system (Supplementary video file 2).
5. Conclusions
Funding
The new VKG system makes it possible to record the whole mucosal wave pattern of entire vocal folds in a single session. Although further studies are required to confirm its clinical efficacy for the evaluation of the vocal folds, the system can be used to evaluate the static and dynamic status of vocal folds in patients with vocal cord diseases.
S.-G. Wang has received grants from the Pusan National University (Grant number 221016) Research Grant (2 years), funded by Pusan National University School of Medicine.
Conflict of interest We have no relevant conflict of interest.
Acknowledgement S.-G. Wang has received grants from the Pusan National University Research Grant (2 years), funded by Pusan National University School of Medicine and Biomedical Research Institute.
S.-G. Wang et al. / Auris Nasus Larynx 43 (2016) 315–321
Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.anl. 2015.10.002. References [1] Svec JG, Schutte HK. Videokymography: high-speed line scanning of vocal fold vibration. J Voice 1996;10:201–5. [2] Svec JG, Schutte HK, Miller DG. A subharmonic vibratory pattern in normal vocal folds. J Speech Hear Res 1996;39:135–43.
321
[3] Hess MM, Gross M. High-speed, light-intensified digital imaging of vocal fold vibrations in high optical resolution via indirect microlaryngoscopy. Ann Otol Rhinol Laryngol 1993;102:502–7. [4] Schutte HK, Svec JG, Sram F. First results of clinical application of videokymography. Laryngoscope 1998;108:1206–10. [5] Wang SG, Lee BJ, Lee JC, Lim YS, Park YM, Park HJ, et al. Development of 2D scanning videokymography for analysis of vocal cord vibration. J Kor Soc Laryngol Phoniatr Logoped 2013;24:107–11. [6] Wittenberg T, Tigges M, Mergell P, Eysholdt U. Functional imaging of vocal fold vibration: digital multislice high-speed kymography. J Voice 2000;14:422–42. [7] Sung MW, Kim KH, Koh TY. Videostrobokymography: a new method for the quantitative analysis of vocal fold vibration. Laryngoscope 1999;109:1859–63.
Auris Nasus Larynx journal homepage: www.elsevier.com/locate/anl
A new videokymography system for evaluation of the vibration pattern of entire vocal folds Soo-Geun Wang a, Hee-June Park a, Byung-Joo Lee a, Sung-Mo Lee b, Bumjun Ko c, Sang Min Lee c, Young Min Park c,* a Department of Otorhinolaryngology-Head and Neck Surgery, Pusan National University School of Medicine and Biomedical Research Institute, Busan, Republic of Korea b Lee Sung Mo Internal Medicine Clinic, Busan, Republic of Korea c Department of Otorhinolaryngology, Bundang Jesaeng Hospital, Deajin Medical Center, Seongnam, Gyeonggi, Republic of Korea
A R T I C L E I N F O
A B S T R A C T
Article history: Received 11 August 2015 Accepted 16 October 2015 Available online 18 November 2015
Objective: To overcome the limitations of previous videokymography methods, we developed a new videokymography system for the evaluation of the whole mucosal wave of the entire vocal cord mucous membrane. Methods: To confirm the usefulness of the new videokymography system, we performed videokymography to evaluate the mucosal wave of the vocal folds during modal and falsetto phonation in normal adult males. Additionally, we serially performed both laryngeal videostroboscopy and the new videokymography method in patients diagnosed with acute ulcerative laryngitis. Results: Using the new videokymography system, the mucosal wave pattern of entire vocal folds was captured during the examination. The opening and closing durations could be differentiated, and the symmetry of amplitude and phase could be assessed. The shape of the medial and lateral peaks could be assessed. In patients with acute laryngitis, the new videokymography system showed an enhanced ability to evaluate the flexibility of the vocal folds. Conclusion: The new videokymography system enables recording of the whole mucosal wave pattern of entire vocal folds. Although further studies are required to confirm its clinical efficacy for the evaluation of vocal folds, the system can be applied to evaluate the static and dynamic status of vocal folds in patients with vocal cord diseases. ß 2015 Elsevier Ireland Ltd. All rights reserved.
Keywords: Videokymography Vocal cord Vibration
1. Introduction For the physical examination of patients with voice change complaints, it is important to assess the static and dynamic status of the vocal folds. Using a laryngeal endoscope,
* Corresponding author at: Department of Otorhinolaryngology, Bundang Jesaeng Hospital, Deajin Medical Center, Seohyeon-ro 180, Bundang-gu, Seongnam, Gyeonggi, Republic of Korea. Tel.: +82 10 4230 3725; fax: +82 31 779 0265. E-mail address: [email protected] (Y.M. Park). http://dx.doi.org/10.1016/j.anl.2015.10.002 0385-8146/ß 2015 Elsevier Ireland Ltd. All rights reserved.
otolaryngologists can evaluate the structural abnormalities and mobility of the vocal folds. However, the dynamic abnormalities of the vocal folds could not be detected on laryngeal endoscopy in some patients with voice change complaints [1]. In these patients, the vibration pattern of the vocal folds should be assessed. For humans to produce voice, the vocal folds must vibrate rapidly at a frequency of 70–1000 Hz, although the frequency differs according to sex [1]. However, conventional laryngeal endoscopy cannot assess the mucosal wave of the vocal folds due to the image processing speed (50–60 images/s) [1].
316
S.-G. Wang et al. / Auris Nasus Larynx 43 (2016) 315–321
Although the vibration pattern of the vocal folds can be observed using optical illusory slow motion with a stroboscope, this is possible only in patients with a periodic vibration pattern [1,2]. By contrast, a high-speed imaging system can observe the mucosal wave of the vocal folds irrespective of vibration periodicity. However, its use is not widespread because of the high cost [3]. Although Svec et al. developed the videokymography (VKG) system to examine the mucosal wave of the vocal folds located on a fixed line, the mucosal wave of the entire vocal folds could not be observed in a single recording [1,4]. As mentioned above, various imaging techniques were developed to assess the mucosal wave pattern of the vocal folds. However, as each system has its advantages and disadvantages, they are used clinically in a complementary manner. To analyze the mucosal wave pattern of the entire vocal folds in a single recording, we developed a specific CCD video system and produced a new VKG system equipped with a CCD video sensor [5]. Use of this new VKG system to evaluate the vibration pattern of the vocal folds results in two types of image of the vocal folds being obtained (laryngeal endoscopic image and videokymographic image). Unlike the previous VKG system devised by Svec et al., our VKG system enables evaluation of the whole mucosal wave pattern of the entire vocal folds during a single examination. To confirm its clinical usefulness, the VKG system was used to evaluate the mucosal wave pattern of the vocal folds during falsetto and modal phonation of normal adult males. Additionally, VKG was serially applied to patients with acute laryngitis to evaluate the dynamic healing status of their vocal folds. 2. Materials and methods 2.1. Subjects The Institutional Review Board of Pusan National University Hospital approved this study (#E-2015105). We invented a specific CCD video system and produced a new VKG system equipped with a CCD video system to evaluate the mucosal wave pattern of entire vocal folds. The new VKG system was applied to evaluate the vibration pattern of the vocal folds in two subjects. One subject (P.H.J.) produced falsetto and modal phonation, and the vibration pattern of his vocal folds was examined using the new VKG system. The other subject (L.S.M.) was diagnosed with acute ulcerative laryngitis, and volunteered to undergo both laryngeal videostroboscopy and the new VKG method for the evaluation of disease status. The examinations were performed serially after the commencement of treatment. To confirm the usefulness of our system, stroboscopy and modified VKG were performed simultaneously during the follow-up period. 2.2. Principle of the new VKG system The previous VKG system devised by Svec et al. can record images from a single selected line (Fig. 1). Therefore, it is possible to increase the rate of images captured and recorded per second at the expense of spatial information. However, the slit of the rolling shutter was not fixed in one place in the new VKG system, instead it moved forward along the vocal folds
Fig. 1. Principle of the new VKG system. Using the previous VKG system, only one portion of the vocal folds located on a fixed line (black line) was evaluated during the examination. In the new VKG system, the slit of the rolling shutter moved forward (black arrow) along the vocal folds during the examination. Therefore, the whole mucosal wave of the entire vocal folds could be assessed in a single examination.
(Fig. 1). During extended-length examination, it continues to move back and forth repeatedly. Therefore, the whole mucosal wave of the entire vocal folds was observed and recorded in a single examination, and characteristic videokymographic images were obtained. 2.3. Configuration of the new VKG system A complementary metal-oxide semiconductor (CMOS) video sensor and rolling shutter were used to obtain the videokymographic images of the entire vocal folds. This system was designed for the acquisition of images at rates of 30 frames/s and 32,400 lines/s, which is sufficient to cover the frequency range of the vocal folds. A 300 W xenon light source (Storz Nova 300; Karl Storz, Tuttlingen, Germany) was used to provide sufficient illumination. In the previous VKG system, the entire vocal folds could not be assessed in a single examination because only one portion of the vocal folds located on a fixed line was observed. Because the slit of the rolling shutter was fixed in one place, the entire mucosal wave could be examined. By contrast, the slit of the rolling shutter of our system moved forward from the posterior portion of the vocal folds during the examination (Fig. 1). Therefore, the mucosal wave of the entire vocal folds could be assessed in a single examination. 3. Results 3.1. Videokymographic images of normal adult males Using the new VKG system, videokymographic images were obtained during phonation of normal adult males (Fig. 2).
S.-G. Wang et al. / Auris Nasus Larynx 43 (2016) 315–321
317
Fig. 2. Characteristic videokymographic images generated by the new VKG system during phonation. (A) The mucosal wave pattern of the entire vocal folds was captured during a single examination. (B) The symmetry of the amplitude (arrow) could be assessed. (C) The opening (b) and closing (a) durations could be differentiated. (D and E) The shape of the medial (arrow) and lateral peaks (arrow) could be assessed.
The mucosal wave pattern of the entire vocal folds was evaluated during a single examination (Fig. 2A). The opening and closing durations could be differentiated, and the symmetry of the amplitude and phase could be assessed (Fig. 2B and C). The shape of the medial and lateral peaks could also be assessed (Fig. 2D and E). 3.2. Stroboscopic and videokymographic images in a patient with acute laryngitis Both vocal folds revealed diffuse redness with irregular mucosal edges using both imaging modalities at the first visit. The mucosal wave of the vocal folds was completely absent, and purulent discharge was observed in the larynx. In addition, a spindle-shaped gap was observed because the vocal folds could not make contact with each other (Fig. 3A and B) (Supplementary video file 1). On both imaging modalities, the patient showed slight improvement in redness and purulent discharge of both vocal
cords after 1 week. Although the gap between the cords persisted, incomplete glottis closure remained evident, as shown in Fig. 4A. However, the new VKG method, but not laryngeal videostroboscopy, revealed that the mucosal waves of both vocal cords had slightly recovered. However, the amplitude of the left cord was less than that of the right (Fig. 4B). The two imaging techniques, laryngeal videostroboscopy and the new VKG method, were performed after 4 weeks of treatment. Both showed that adduction of both vocal cords had recovered completely, and the redness and discharge had disappeared almost completely (Fig. 5A). In addition, the new VKG system showed that the mucosal waves of both cords had recovered almost completely, and the shapes of their medial peaks were normal (Fig. 5B) (Supplementary video file 2). 4. Discussion Laryngeal videostroboscopy is commonly used to evaluate vocal cord lesions. However, much experience is required to
318
S.-G. Wang et al. / Auris Nasus Larynx 43 (2016) 315–321
Fig. 3. Images obtained by laryngeal videostroboscopy (A) and the new VKG system (B) at the first visit (Supplementary video file 1).
make a definite diagnosis based only on laryngeal videostroboscopic findings. With the exception of vocal cord polyposis, which leads to a larger amplitude of mucosal waves, it is impossible to make a diagnosis based on only a single laryngeal videostroboscopy image. Although structural and functional abnormalities of the vocal cords can be evaluated using the VKG system devised by Svec et al., the entire vocal cord mucous membrane cannot be observed. Although multi-line VKG or digital VKG systems, including strobovideokymography (SVKG) and digital VKG, were developed to overcome the limitations of VKG, these methods are also limited in terms of their clinical application [6,7]. SVKG can be used to evaluate lesions at multiple horizontal segments of the vocal cord mucous membrane.
However, similar to classic laryngeal videostroboscopy, it cannot be performed in patients with aperiodic vibration. In digital VKG, kymographic images can be acquired through post-processing of captured images using software [6]. Digital VKG could additionally assess the phase difference between the anterior and posterior surfaces of the vocal cord. However, its recording time is limited, and a large amount of memory is required to save captured images. In addition, it cannot image the entire vocal cords simultaneously [6]. To overcome these limitations, we developed a new VKG system for the evaluation of the whole mucosal wave pattern of the vocal folds. As this VKG system can observe the actual vibration pattern of the entire vocal cord mucous membrane simultaneously, the distortion problems associated with the
S.-G. Wang et al. / Auris Nasus Larynx 43 (2016) 315–321
319
Fig. 4. Imaging findings of laryngeal videostroboscopy (A) and the new VKG system (B) after 1 week. The amplitude of the mucosal wave of the left vocal cord was less than that of the right vocal cord as determined by the new VKG system.
previous VKG system can be avoided. In the present study, we assessed the system’s efficacy in comparison with that of laryngeal videostroboscopy. The system successfully recorded dynamic images of the entire vocal cord mucous membrane in real-time and facilitated analysis of all mucosal movements simultaneously. In particular, the flexibility of the vocal folds could be easily evaluated using the new VKG system. When no structural abnormalities of the vocal folds are detected in patients with hoarseness, it is important to assess the flexibility of the vocal folds. Because inflammatory diseases can increase the stiffness of the lamina propria of the vocal folds due to an inflammatory reaction, the flexibility of
the vocal folds can deteriorate without remarkable gross abnormalities. Use of the new VKG system in such cases would enable the dynamic status of the vocal folds being evaluated. In the present study, we invented the new VKG system with the rolling shutter and showed the superiority of it in the analysis of dynamic movement of the vocal folds compared to stroboscopy. However, further study is required to prove clinical efficacy and superiority of it compared to traditional single line VKG. Therefore, we will perform the comparison analysis of the new VKG system and the traditional single line VKG in the future study.
S.-G. Wang et al. / Auris Nasus Larynx 43 (2016) 315–321
320
Fig. 5. Imaging findings of laryngeal videostroboscopy and the new VKG system after 4 weeks. The mucosal waves of both cords had recovered almost completely, and the shapes of their medial peaks were normal, as determined using the new VKG system (Supplementary video file 2).
5. Conclusions
Funding
The new VKG system makes it possible to record the whole mucosal wave pattern of entire vocal folds in a single session. Although further studies are required to confirm its clinical efficacy for the evaluation of the vocal folds, the system can be used to evaluate the static and dynamic status of vocal folds in patients with vocal cord diseases.
S.-G. Wang has received grants from the Pusan National University (Grant number 221016) Research Grant (2 years), funded by Pusan National University School of Medicine.
Conflict of interest We have no relevant conflict of interest.
Acknowledgement S.-G. Wang has received grants from the Pusan National University Research Grant (2 years), funded by Pusan National University School of Medicine and Biomedical Research Institute.
S.-G. Wang et al. / Auris Nasus Larynx 43 (2016) 315–321
Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.anl. 2015.10.002. References [1] Svec JG, Schutte HK. Videokymography: high-speed line scanning of vocal fold vibration. J Voice 1996;10:201–5. [2] Svec JG, Schutte HK, Miller DG. A subharmonic vibratory pattern in normal vocal folds. J Speech Hear Res 1996;39:135–43.
321
[3] Hess MM, Gross M. High-speed, light-intensified digital imaging of vocal fold vibrations in high optical resolution via indirect microlaryngoscopy. Ann Otol Rhinol Laryngol 1993;102:502–7. [4] Schutte HK, Svec JG, Sram F. First results of clinical application of videokymography. Laryngoscope 1998;108:1206–10. [5] Wang SG, Lee BJ, Lee JC, Lim YS, Park YM, Park HJ, et al. Development of 2D scanning videokymography for analysis of vocal cord vibration. J Kor Soc Laryngol Phoniatr Logoped 2013;24:107–11. [6] Wittenberg T, Tigges M, Mergell P, Eysholdt U. Functional imaging of vocal fold vibration: digital multislice high-speed kymography. J Voice 2000;14:422–42. [7] Sung MW, Kim KH, Koh TY. Videostrobokymography: a new method for the quantitative analysis of vocal fold vibration. Laryngoscope 1999;109:1859–63.