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The First Application of the Two-Dimensional Scanning Videokymography in Excised Canine Larynx Model
The First Application of the Two-Dimensional Scanning Videokymography in Excised Canine Larynx Model *Soo-Geun Wang, *Hee-June Park, *Jae Keun Cho, *Jeon Yeob Jang, †Won Yong Lee, *Byung-Joo Lee, †Jin-Choon Lee, and *Wonjae Cha, *Busan, yYangsan, Kyeongnam, Republic of Korea Summary: Objective. Evaluation of the vibratory pattern of vocal folds is of paramount importance to diagnose vocal fold disorders. Currently, laryngeal videokymography (VKG) and digital kymography from high-speed videolaryngoscopy are the available techniques for studying aperiodic vibrations of vocal folds. But VKG has the fundamental limitation that only linear portion of the vocal fold mucosa can be visualized. Digital kymography has the disadvantages of no immediate feedback during examination, considerable waiting time before kymographic visualization, recoding duration limited to seconds, and extreme demands on storage space. We developed a new system—two-dimensional (2D) scanning VKG—for evaluation of the vibratory pattern of vocal folds, and the method provided a possible alternative with its advantages and disadvantages. Thus, we aimed to evaluate the feasibility of the new device for the vocal fold vibration in excised canine larynx model. Methods. The vibrating pattern for vocal folds was evaluated using high-speed videolaryngoscopic and 2D scanning videokymographic system in the excised canine larynx model. Results. The images of canine vocal folds were captured with high-speed videolaryngoscopic system and converted to the kymographic images using the software. The kymographic image acquired by 2D scanning VKG was comparable with multi-line digital kymography at multiple locations. Conclusions. The vocal fold vibration could be evaluated in the excised canine larynx model using 2D scanning VKG. And this new device is expected to be a promising tool to evaluate the vocal fold vibration for clinical practice and voice research. Key Words: Videokymography–Vocal fold–Vibration–Canine larynx–High-speed video system. INTRODUCTION Examination of the vibratory movement of vocal fold mucosa is important to understand the mechanism of voice production and to diagnose various vocal fold disorders. Laryngeal videostroboscopy is widely used to show ‘‘illusory’’ slow motion images of the vibrating vocal folds. However, it can usually obtain a clear image when vocal fold vibrations are periodic with stable phonation frequency.1 Currently, laryngeal videokymography (VKG) and high-speed videolaryngoscopic system are the only available techniques for directly studying aperiodic vibrations of vocal folds.2 Laryngeal VKG was developed to enable kymographic image encoded as a standard video signal3 and can reveal the vocal fold kymography directly on a standard video monitor.4 But VKG has the fundamental limitation that only linear portion of the vocal fold mucosa can be visualized. For the evaluation of the motion of the whole vocal fold vibration, laryngeal high-speed imaging system was introduced.5 Digital kymography is extracted from the images obtained in laryngeal high-speed imagAccepted for publication September 26, 2014. The authors have no funding and financial relationship to disclose. Conflict of interest: None. From the *Department of Otorhinolaryngology-Head and Neck Surgery, Pusan National University Hospital, Busan, Republic of Korea; and the yDepartment of Otorhinolaryngology-Head and Neck Surgery, Pusan National University Yangsan Hospital, Yangsan, Kyeongnam, Republic of Korea. Address correspondence and reprint requests to Wonjae Cha, Department of Otorhinolaryngology-Head and Neck Surgery, Pusan National University Hospital, 179 Gudeok-Ro, Seo-Gu, Busan, 602-739, Republic of Korea. E-mail: Cha.Wonjae@gmail. com Journal of Voice, Vol. -, No. -, pp. 1-4 0892-1997/$36.00 Ó 2014 The Voice Foundation http://dx.doi.org/10.1016/j.jvoice.2014.09.029
ing system and show the real vibratory image of vocal folds mucosa.6,7 But it has the disadvantages of no immediate feedback during examination, considerable waiting time before kymographic visualization, recoding duration limited to seconds, and extreme demands on storage space.8 To overcome these limitations of the previous methods, we developed a new videokymographic system for twodimensional (2D) analysis of the whole vocal folds.9 In this article, we report the first application of 2D scanning VKG for the vocal fold vibration in the excised canine larynx model. MATERIALS AND METHODS Excised canine larynx model A male dog weighing 8 kg was used in this study. The dog was sacrificed for this study, and the larynx was eviscerated from the fourth tracheal ring to the hyoid bone. Supraglottal structures such as epiglottis, false vocal folds, and aryepiglottic folds were removed. Interarytenoid approximation was performed to medialize the vocal folds for the excised larynx. The prepared excised larynx was fixed in the lung apparatus designed for the canine model, and an endotracheal tube was used to seal off the trachea and to deliver airflow to the glottis. The endoscope could be moved to and pro for the appropriate distance from the canine larynx (Figure 1). High-speed videolaryngoscopic system and digital kymography Laryngeal color high-speed video system (KayPENTAX, Model 9710, Montvale, NJ, USA) with a rigid endoscope (Storz, 10 mm, 0 Laryngoscope, 8701AG, Germany) was used to
2
FIGURE 1. The setting of two-dimensional (2D) scanning kymography for the excised canine larynx. The prepared excised larynx was fixed in the lung apparatus designed for the canine model, and an endotracheal tube was used to seal off the trachea and to deliver airflow to the glottis. The endoscope could be mobilized to and pro for the appropriate distance from the canine larynx. Full HD CMOS (complementary metal oxide semiconductor) image sensor (1920 3 1080 pixels) and rolling shutter camera were implemented to the new device. A rigid endoscope (Storz, 10 mm, 0 Laryngoscope) were assembled with the new device to the system. capture the vocal fold mucosa of the excised canine larynx at 2000 frames per second. The obtained images were converted to the kymographic image (digital kymography) using Kay’s image processing software (KIPS, KayPENTAX, Model 9181). Two-dimensional scanning VKG Two-dimensional videokymographic system was manufactured in cooperation with U-medical Co. LTD (Busan, Korea). Full
Journal of Voice, Vol. -, No. -, 2014
HD CMOS (complementary metal oxide semiconductor) image sensor (1920 3 1080 pixels) and rolling shutter camera were implemented to the new device. A rigid endoscope (Storz, 10 mm, 0 Laryngoscope) and A 300-W xenon light source (Storz, NOVA 300) were assembled with the new device to the system (Figure 1). The system was used to capture the entire vocal fold of the excised canine larynx, and the video was recorded at 30 frames per second. The resolution of the final 2D VKG images was 1920 3 1080 pixels, and the exposition time of a single line displayed in the image (1920 3 1080 pixels) was 1/32 400 second because the scanning time for one frame with a rolling shutter camera is 1/30 second. RESULTS High-speed videolaryngoscopic imaging and digital kymography in the excised canine larynx model The vocal folds vibration of the excised canine larynx was captured with high-speed videolaryngoscopic system at 2000 frames per second. The fundamental frequency measured 387 Hz with the microphone. The obtained video was processed using Kay’s image processing software, and digital kymography was extracted in the four levels of the vocal folds (Figure 2). Two-dimensional VKG imaging in the excised canine larynx model The vibrating images of the canine vocal folds were captured with 2D scanning VKG system (Figure 3). The rolling shutter
FIGURE 2. The postprocessing of laryngeal color high-speed video-endoscopic imaging and digital kymography (DKG). The anterior part of the larynx is on the bottom. As shown previously, the four levels of the canine vocal folds were analyzed (A) and converted to the kymographic images (B) with Kay’s image processing software (KIPS).
Soo-Geun Wang, et al
2D Scanning Videokymography in Excised Canine Larynx
3
FIGURE 3. The vibrating images of the canine vocal folds captured with two-dimensional (2D) videokymographic system. The rolling shutter camera scanned the vibrating vocal folds of the excised canine vertically downward and various phases of vibrating vocal folds could be shown in a single frame. The images of opening, open, closing, and closed phases were displayed on a monitor constantly like digital kymography. The amplitude and phasic difference could be compared between both vocal folds. camera scanned the vibrating vocal folds of the excised canine vertically, and the entire phase of the vibrating cycle could be shown in a single frame. The multiple lines with various timing were constantly displayed on a monitor. The amplitude and phase differences could be compared between both vocal folds.
DISCUSSION Kymography of vocal fold vibration has been used to capture and record vocal fold movements since the early 1970s. Gall et al10 used a single lens reflex camera and an indirect laryngoscopic mirror to capture vocal fold movements. The entire area of the vocal fold could be recorded using the instrument as the slit shutter moved in the direction of inferior-to-superior in the front of the fixed film in the equipment, which was called ‘‘photokymography.’’ Then, in 1984, he devised strip kymography and it enabled the vibrating images of vocal folds to be acquired while the slit shutter was fixed to one point of the vocal folds and the film was moved rapidly.11 Currently there are three kymographic techniques for displaying vocal fold vibration: VKG, high-speed digital kymography, and strobovideokymography.8 The VKG system delivers the kymographic images directly in real time on a video screen, and the two latter methods need software to construct kymographic images extracted from high-speed videolaryngoscopy and strobovideolaryngoscopy. All the three techniques are certainly useful to visualize and evaluate the vibration of the vocal fold mucosa but have some limitations in clinical settings.8 First, VKG can display only one position displayed at one time. The position of the kymography should be selected during recordings, and anterior-posterior phase differences are not displayed. Multiple simultaneous kymographs along the glottis are not available. Second, high-speed digital kymography, based on high-speed videolaryngoscopic system, has no immediate feedback on vocal fold vibration during examination. To construct kymographic visualization, considerable waiting time is mandatory. The recording duration of high-speed videolaryngoscopic system is several seconds at most but it demands extremely huge storage space. Finally, strobovideokymography, based on laryngeal strobovideolaryngoscopic system, depends
on the quality of stroboscopic triggering. Because the image of strobovideolaryngoscopy is unsatisfactory when the pitch is unstable, only periodic vibration can be analyzed. We developed 2D scanning VKG that might provide a possible alternative to the other devices with its advantages and disadvantages. The principle of Gall’s ‘‘photokymography’’ was applied to our device (Figure 4). A modified full HD CMOS image sensor with electronic rolling shutter camera was implemented for the new VKG system. Rolling shutter is a method of image acquisition in which a picture or each frame of a video is recorded not from a snapshot of a single point in time, but rather by scanning across the frame either vertically or horizontally. The rolling shutter in a CMOS image sensor works similar to a focal plane shutter in a film camera (the rolling shutter is sometimes referred to as an electronic focal plane shutter). Typically, the rows of pixels in the image sensor are reset in sequence, starting at the top of the image and proceeding row by row to the bottom. In our device, the time of a frame was set to 1/30 second, and the resolution of CMOS was 1920 3 1080 pixels. Because the images were horizontally scanned, the exposure time of a single line might be estimated
FIGURE 4. Principle of Gall’s ‘‘photokymography’’ and 2D scanning VKG. The entire area of the vocal folds could be recorded using the instrument as the slit shutter moved in the direction of superior-toinferior in the front of the fixed film in the equipment, which was called photokymography. Using this technique, dynamic images of the entire vocal folds could be acquired, combining several images in serial order captured in different time zones. In two-dimensional (2D) scanning VKG, the modified complementary metal oxide semiconductor (CMOS) image sensor with a rolling shutter camera makes this technique possible in real time.
4 to 1/32 400 (30 3 1080) second. The rolling shutter camera continuously scans each line of the laryngoscopic images from top to bottom, and CMOS image sensor acquires the multiple lines with different timings (Figure 4). The images of 2D scanning VKG moved up and down according to the change in pitch or were occasionally displayed in a fixed form. These effects occur because of an aliasing phenomenon. In cases with discordance between the scanning camera speed and the vibration cycle of the vocal fold, the vibratory image of the vocal folds moves upward or downward in waves. On the other hand, when the scanning cycle matched the vibration cycle of the vocal fold, the image is shown like a fixed form. The 2D scanning VKG system could extract dynamic images of the entire vocal fold in real time and analyze the whole vibratory movement simultaneously. In this study, we performed both 2D scanning VKG and highspeed digital kymography. As a new device for evaluating vocal fold vibration, 2D scanning VKG system has several advantages compared with laryngeal high-speed imaging system. First of all, 2D scanning VKG system could extract dynamic images of the entire vocal fold in real time and analyze the whole vibratory movement simultaneously. In the second place, 2D scanning VKG can be performed in real time and thus maybe useful in office-based settings. As for digital kymography, the images captured in high-speed videolaryngoscopy should be converted to the kymographic image using special software (such as Kay’s image processing software) and thus it is hard to be applicable immediately in clinical settings. Third, high-speed videolaryngoscopic system needs very large storage space for video or images (1000 4000 frame/s). But 2D scanning VKG adopts the setting of 30 frames/s and thus need smaller scale of data storage. The result of 2D scanning VKG is the multi-phasic functional images of the vibrating mucosa, and several key images might be enough to analyze vocal fold mucosa. Based on the electronic medical record system, 2D scanning VKG system could be a more useful tool in clinical settings because the key images can be attached to the medical chart. But 2D scanning VKG also had the disadvantages. The motion of the vocal fold at a specific location could not be evaluated here like in VKG or digital kymography, and anteriorposterior phase differences could not be evaluated like in a multi-line digital kymography or in phonovibrography. Combination of spatial and temporal information could make it problematic to determine whether the irregularities shown in the 2D
Journal of Voice, Vol. -, No. -, 2014
VKG images are due to some spatial abnormality on the vocal folds or due to irregular nature of the vibrations. Canine and human larynges have anatomic similarities that allow the canine larynx to be used as an animal model for studying mechanisms of human phonation. An excised canine larynx model was used to examine the feasibility of 2D scanning VKG for evaluating vibration patterns of vocal folds, and we could verify the visualization of the canine vocal folds using 2D scanning VKG. Further study for the application for humans should be followed. CONCLUSIONS The vibration of the entire vocal folds could be evaluated in the excised canine larynx model using the 2D scanning VKG. And this new device is expected to be a promising tool to evaluate the vibration patterns of vocal folds for clinical practice and voice research. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.jvoice.2014.09.029. REFERENCES 1. Kendall KA. High-speed laryngeal imaging compared with videostroboscopy in healthy subjects. Arch Otolaryngol Head Neck Surg. 2009;135:274–281. 2. Verikas A, Uloza V, Bacauskiene M, Gelzinis A, Kelertas E. Advances in laryngeal imaging. Eur Arch Otorhinolaryngol. 2009;266:1509–1520. 3. Svec JG, Schutte HK. Videokymography: high-speed line scanning of vocal fold vibration. J Voice. 1996;10:201–205. 4. Qiu Q, Schutte HK. Real-time kymographic imaging for visualizing human vocal-fold vibratory function. Rev Sci Instrum. 2007;78:024302. 5. Hirose H. High-speed digital imaging of vocal fold vibration. Acta Otolaryngol Suppl. 1988;458:151–153. 6. Wittenberg T, Tigges M, Mergell P, Eysholdt U. Functional imaging of vocal fold vibration: digital multislice high-speed kymography. J Voice. 2000;14:422–442. 7. Larsson H, Hertegard S, Lindestad PA, Hammarberg B. Vocal fold vibrations: high-speed imaging, kymography, and acoustic analysis: a preliminary report. Laryngoscope. 2000;110:2117–2122. 8. Svec JG, Schutte HK. Kymographic imaging of laryngeal vibrations. Curr Opin Otolaryngol Head Neck Surg. 2012;20:458–465. 9. Wang SG, Lee BJ, Lee JC, et al. Development of two-dimensional scanning videokymography for analysis of vocal fold vibration. J Korean Soc Laryngol Phoniatr Logop. 2013;24:107–111. 10. Gall V, Gall D, Hanson J. Laryngeal photokymography. Arch Klin Exp Ohren Nasen Kehlkopfheilkd. 1971;200:34–41. 11. Gall V. Strip kymography of the glottis. Arch Otorhinolaryngol. 1984;240: 287–293.
ing system and show the real vibratory image of vocal folds mucosa.6,7 But it has the disadvantages of no immediate feedback during examination, considerable waiting time before kymographic visualization, recoding duration limited to seconds, and extreme demands on storage space.8 To overcome these limitations of the previous methods, we developed a new videokymographic system for twodimensional (2D) analysis of the whole vocal folds.9 In this article, we report the first application of 2D scanning VKG for the vocal fold vibration in the excised canine larynx model. MATERIALS AND METHODS Excised canine larynx model A male dog weighing 8 kg was used in this study. The dog was sacrificed for this study, and the larynx was eviscerated from the fourth tracheal ring to the hyoid bone. Supraglottal structures such as epiglottis, false vocal folds, and aryepiglottic folds were removed. Interarytenoid approximation was performed to medialize the vocal folds for the excised larynx. The prepared excised larynx was fixed in the lung apparatus designed for the canine model, and an endotracheal tube was used to seal off the trachea and to deliver airflow to the glottis. The endoscope could be moved to and pro for the appropriate distance from the canine larynx (Figure 1). High-speed videolaryngoscopic system and digital kymography Laryngeal color high-speed video system (KayPENTAX, Model 9710, Montvale, NJ, USA) with a rigid endoscope (Storz, 10 mm, 0 Laryngoscope, 8701AG, Germany) was used to
2
FIGURE 1. The setting of two-dimensional (2D) scanning kymography for the excised canine larynx. The prepared excised larynx was fixed in the lung apparatus designed for the canine model, and an endotracheal tube was used to seal off the trachea and to deliver airflow to the glottis. The endoscope could be mobilized to and pro for the appropriate distance from the canine larynx. Full HD CMOS (complementary metal oxide semiconductor) image sensor (1920 3 1080 pixels) and rolling shutter camera were implemented to the new device. A rigid endoscope (Storz, 10 mm, 0 Laryngoscope) were assembled with the new device to the system. capture the vocal fold mucosa of the excised canine larynx at 2000 frames per second. The obtained images were converted to the kymographic image (digital kymography) using Kay’s image processing software (KIPS, KayPENTAX, Model 9181). Two-dimensional scanning VKG Two-dimensional videokymographic system was manufactured in cooperation with U-medical Co. LTD (Busan, Korea). Full
Journal of Voice, Vol. -, No. -, 2014
HD CMOS (complementary metal oxide semiconductor) image sensor (1920 3 1080 pixels) and rolling shutter camera were implemented to the new device. A rigid endoscope (Storz, 10 mm, 0 Laryngoscope) and A 300-W xenon light source (Storz, NOVA 300) were assembled with the new device to the system (Figure 1). The system was used to capture the entire vocal fold of the excised canine larynx, and the video was recorded at 30 frames per second. The resolution of the final 2D VKG images was 1920 3 1080 pixels, and the exposition time of a single line displayed in the image (1920 3 1080 pixels) was 1/32 400 second because the scanning time for one frame with a rolling shutter camera is 1/30 second. RESULTS High-speed videolaryngoscopic imaging and digital kymography in the excised canine larynx model The vocal folds vibration of the excised canine larynx was captured with high-speed videolaryngoscopic system at 2000 frames per second. The fundamental frequency measured 387 Hz with the microphone. The obtained video was processed using Kay’s image processing software, and digital kymography was extracted in the four levels of the vocal folds (Figure 2). Two-dimensional VKG imaging in the excised canine larynx model The vibrating images of the canine vocal folds were captured with 2D scanning VKG system (Figure 3). The rolling shutter
FIGURE 2. The postprocessing of laryngeal color high-speed video-endoscopic imaging and digital kymography (DKG). The anterior part of the larynx is on the bottom. As shown previously, the four levels of the canine vocal folds were analyzed (A) and converted to the kymographic images (B) with Kay’s image processing software (KIPS).
Soo-Geun Wang, et al
2D Scanning Videokymography in Excised Canine Larynx
3
FIGURE 3. The vibrating images of the canine vocal folds captured with two-dimensional (2D) videokymographic system. The rolling shutter camera scanned the vibrating vocal folds of the excised canine vertically downward and various phases of vibrating vocal folds could be shown in a single frame. The images of opening, open, closing, and closed phases were displayed on a monitor constantly like digital kymography. The amplitude and phasic difference could be compared between both vocal folds. camera scanned the vibrating vocal folds of the excised canine vertically, and the entire phase of the vibrating cycle could be shown in a single frame. The multiple lines with various timing were constantly displayed on a monitor. The amplitude and phase differences could be compared between both vocal folds.
DISCUSSION Kymography of vocal fold vibration has been used to capture and record vocal fold movements since the early 1970s. Gall et al10 used a single lens reflex camera and an indirect laryngoscopic mirror to capture vocal fold movements. The entire area of the vocal fold could be recorded using the instrument as the slit shutter moved in the direction of inferior-to-superior in the front of the fixed film in the equipment, which was called ‘‘photokymography.’’ Then, in 1984, he devised strip kymography and it enabled the vibrating images of vocal folds to be acquired while the slit shutter was fixed to one point of the vocal folds and the film was moved rapidly.11 Currently there are three kymographic techniques for displaying vocal fold vibration: VKG, high-speed digital kymography, and strobovideokymography.8 The VKG system delivers the kymographic images directly in real time on a video screen, and the two latter methods need software to construct kymographic images extracted from high-speed videolaryngoscopy and strobovideolaryngoscopy. All the three techniques are certainly useful to visualize and evaluate the vibration of the vocal fold mucosa but have some limitations in clinical settings.8 First, VKG can display only one position displayed at one time. The position of the kymography should be selected during recordings, and anterior-posterior phase differences are not displayed. Multiple simultaneous kymographs along the glottis are not available. Second, high-speed digital kymography, based on high-speed videolaryngoscopic system, has no immediate feedback on vocal fold vibration during examination. To construct kymographic visualization, considerable waiting time is mandatory. The recording duration of high-speed videolaryngoscopic system is several seconds at most but it demands extremely huge storage space. Finally, strobovideokymography, based on laryngeal strobovideolaryngoscopic system, depends
on the quality of stroboscopic triggering. Because the image of strobovideolaryngoscopy is unsatisfactory when the pitch is unstable, only periodic vibration can be analyzed. We developed 2D scanning VKG that might provide a possible alternative to the other devices with its advantages and disadvantages. The principle of Gall’s ‘‘photokymography’’ was applied to our device (Figure 4). A modified full HD CMOS image sensor with electronic rolling shutter camera was implemented for the new VKG system. Rolling shutter is a method of image acquisition in which a picture or each frame of a video is recorded not from a snapshot of a single point in time, but rather by scanning across the frame either vertically or horizontally. The rolling shutter in a CMOS image sensor works similar to a focal plane shutter in a film camera (the rolling shutter is sometimes referred to as an electronic focal plane shutter). Typically, the rows of pixels in the image sensor are reset in sequence, starting at the top of the image and proceeding row by row to the bottom. In our device, the time of a frame was set to 1/30 second, and the resolution of CMOS was 1920 3 1080 pixels. Because the images were horizontally scanned, the exposure time of a single line might be estimated
FIGURE 4. Principle of Gall’s ‘‘photokymography’’ and 2D scanning VKG. The entire area of the vocal folds could be recorded using the instrument as the slit shutter moved in the direction of superior-toinferior in the front of the fixed film in the equipment, which was called photokymography. Using this technique, dynamic images of the entire vocal folds could be acquired, combining several images in serial order captured in different time zones. In two-dimensional (2D) scanning VKG, the modified complementary metal oxide semiconductor (CMOS) image sensor with a rolling shutter camera makes this technique possible in real time.
4 to 1/32 400 (30 3 1080) second. The rolling shutter camera continuously scans each line of the laryngoscopic images from top to bottom, and CMOS image sensor acquires the multiple lines with different timings (Figure 4). The images of 2D scanning VKG moved up and down according to the change in pitch or were occasionally displayed in a fixed form. These effects occur because of an aliasing phenomenon. In cases with discordance between the scanning camera speed and the vibration cycle of the vocal fold, the vibratory image of the vocal folds moves upward or downward in waves. On the other hand, when the scanning cycle matched the vibration cycle of the vocal fold, the image is shown like a fixed form. The 2D scanning VKG system could extract dynamic images of the entire vocal fold in real time and analyze the whole vibratory movement simultaneously. In this study, we performed both 2D scanning VKG and highspeed digital kymography. As a new device for evaluating vocal fold vibration, 2D scanning VKG system has several advantages compared with laryngeal high-speed imaging system. First of all, 2D scanning VKG system could extract dynamic images of the entire vocal fold in real time and analyze the whole vibratory movement simultaneously. In the second place, 2D scanning VKG can be performed in real time and thus maybe useful in office-based settings. As for digital kymography, the images captured in high-speed videolaryngoscopy should be converted to the kymographic image using special software (such as Kay’s image processing software) and thus it is hard to be applicable immediately in clinical settings. Third, high-speed videolaryngoscopic system needs very large storage space for video or images (1000 4000 frame/s). But 2D scanning VKG adopts the setting of 30 frames/s and thus need smaller scale of data storage. The result of 2D scanning VKG is the multi-phasic functional images of the vibrating mucosa, and several key images might be enough to analyze vocal fold mucosa. Based on the electronic medical record system, 2D scanning VKG system could be a more useful tool in clinical settings because the key images can be attached to the medical chart. But 2D scanning VKG also had the disadvantages. The motion of the vocal fold at a specific location could not be evaluated here like in VKG or digital kymography, and anteriorposterior phase differences could not be evaluated like in a multi-line digital kymography or in phonovibrography. Combination of spatial and temporal information could make it problematic to determine whether the irregularities shown in the 2D
Journal of Voice, Vol. -, No. -, 2014
VKG images are due to some spatial abnormality on the vocal folds or due to irregular nature of the vibrations. Canine and human larynges have anatomic similarities that allow the canine larynx to be used as an animal model for studying mechanisms of human phonation. An excised canine larynx model was used to examine the feasibility of 2D scanning VKG for evaluating vibration patterns of vocal folds, and we could verify the visualization of the canine vocal folds using 2D scanning VKG. Further study for the application for humans should be followed. CONCLUSIONS The vibration of the entire vocal folds could be evaluated in the excised canine larynx model using the 2D scanning VKG. And this new device is expected to be a promising tool to evaluate the vibration patterns of vocal folds for clinical practice and voice research. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.jvoice.2014.09.029. REFERENCES 1. Kendall KA. High-speed laryngeal imaging compared with videostroboscopy in healthy subjects. Arch Otolaryngol Head Neck Surg. 2009;135:274–281. 2. Verikas A, Uloza V, Bacauskiene M, Gelzinis A, Kelertas E. Advances in laryngeal imaging. Eur Arch Otorhinolaryngol. 2009;266:1509–1520. 3. Svec JG, Schutte HK. Videokymography: high-speed line scanning of vocal fold vibration. J Voice. 1996;10:201–205. 4. Qiu Q, Schutte HK. Real-time kymographic imaging for visualizing human vocal-fold vibratory function. Rev Sci Instrum. 2007;78:024302. 5. Hirose H. High-speed digital imaging of vocal fold vibration. Acta Otolaryngol Suppl. 1988;458:151–153. 6. Wittenberg T, Tigges M, Mergell P, Eysholdt U. Functional imaging of vocal fold vibration: digital multislice high-speed kymography. J Voice. 2000;14:422–442. 7. Larsson H, Hertegard S, Lindestad PA, Hammarberg B. Vocal fold vibrations: high-speed imaging, kymography, and acoustic analysis: a preliminary report. Laryngoscope. 2000;110:2117–2122. 8. Svec JG, Schutte HK. Kymographic imaging of laryngeal vibrations. Curr Opin Otolaryngol Head Neck Surg. 2012;20:458–465. 9. Wang SG, Lee BJ, Lee JC, et al. Development of two-dimensional scanning videokymography for analysis of vocal fold vibration. J Korean Soc Laryngol Phoniatr Logop. 2013;24:107–111. 10. Gall V, Gall D, Hanson J. Laryngeal photokymography. Arch Klin Exp Ohren Nasen Kehlkopfheilkd. 1971;200:34–41. 11. Gall V. Strip kymography of the glottis. Arch Otorhinolaryngol. 1984;240: 287–293.