Laryngeal High-Speed Videoendoscopy: Rationale and Recommendation for Accurate and Consistent Terminology

Abstract

Purpose

The authors discuss the rationale behind the term laryngeal high-speed videoendoscopy to describe the application of high-speed endoscopic imaging techniques to the visualization of vocal fold vibration.

Method

Commentary on the advantages of using accurate and consistent terminology in the field of voice research is provided. Specific justification is described for each component of the term high-speed videoendoscopy, which is compared and contrasted with alternative terminologies in the literature.

Results

In addition to the ubiquitous high-speed descriptor, the term endoscopy is necessary to specify the appropriate imaging technology and distinguish among modalities such as ultrasound, magnetic resonance imaging, and nonendoscopic optical imaging. Furthermore, the term video critically indicates the electronic recording of a sequence of optical still images representing scenes in motion, in contrast to strobed images using high-speed photography and non-optical high-speed magnetic resonance imaging. High-speed videoendoscopy thus concisely describes the technology and can be appended by the desired anatomical nomenclature such as laryngeal.

Conclusions

Laryngeal high-speed videoendoscopy strikes a balance between conciseness and specificity when referring to the typical high-speed imaging method performed on human participants. Guidance for the creation of future terminology provides clarity and context for current and future experiments and the dissemination of results among researchers.

The accurate and consistent use of terminology is an important trait for any scientific field. Describing technologies with concise and specific language helps to disambiguate nomenclature, provides a common reference across investigators, and prevents the potential for misconceptions to propagate in the future. The purpose of this letter is to discuss the rationale behind the term laryngeal high-speed videoendoscopy (laryngeal HSV) to describe the application of high-speed endoscopic imaging techniques to the visualization of vocal fold vibration. For example, the ubiquitous term high-speed digital imaging could refer to the general application of several different kinds of imaging technologies, such as magnetic resonance imaging; optical coherence tomography; and ultrasound used in ex vivo, in vivo, and synthetic material environments. Applying the term HSV helps make the needed distinction among these technologies. Notably, the focus of this letter is on full-frame HSV technology versus high-speed videokymographic techniques (Švec & Schutte, 1996).

Table 1 lists popular terms that have been used in the voice literature to describe high-speed imaging of vocal fold vibration and is approximately ordered by the first appearance of a particular term. The history of laryngeal HSV thus can be traced from its earliest years using high-speed (nonvideo) motion picture cameras (Farnsworth, 1940; Herriott & Farnsworth, 1938) and electronic, video-based high-speed camera technology (Hess & Gross, 1993; Kiritani, Hirose, & Imagawa, 1993; Wittenberg, Moser, Tigges, & Eysholdt, 1995). Significant advances in the development and application of HSV technology have been made by researchers in several countries, including the United States, Japan, Germany, Sweden, and France. Using the citations in Table 1, one may explore the evolution of terminology in regard to laboratories, journals, and investigator type (clinician, engineer, etc.).

Table 1.

Tabulation of terminology in the voice literature used to describe the endoscopic visualization of human vocal fold vibration using high-speed imaging techniques.

Terminology	Selected references
High-speed motion picture	Farnsworth, 1940; Herriott & Farnsworth, 1938
Ultrahigh-speed photography	Harden, 1975
Ultra high-speed film	Yamada et al., 1982
High-speed laryngeal film	Baer et al., 1983; Booth & Childers, 1979
High-speed digital imaging	Kendall, 2012; Kiritani et al., 1993; Patel et al., 2008; Yamauchi et al., 2012, 2013; Yan et al., 2006
High-speed imaging	Chen et al., 2014; Echternach et al., 2010; Kendall et al., 2005; Kimura, Imagawa, et al., 2010; Kimura, Nito, et al., 2010; Kreiman et al., 2012; Larsson & Hertegård, 2004; Larsson et al., 2000; Maurer et al., 1996; Neubauer et al., 2001; Patel et al., 2012; van As et al., 1999
High-speed recording	Eysholdt et al., 1996
High-speed laryngoscopy	Deliyski et al., 2006; Granqvist & Lindestad, 2001
Endoscopic digital high-speed images	Döllinger et al., 2003
High-speed video imaging	Granqvist et al., 2003
High-speed digital videoendoscopy	Hertegård, 2005
High-speed laryngeal imaging	Kendall, 2009; Yan et al., 2005
Endoscopic digital high-speed recording	Schwarz et al., 2006
Endoscopic digital high-speed video	Lohscheller et al., 2007
High-speed movies	Lohscheller et al., 2008
High-speed videoendoscopy a	Chen et al., 2013; Deliyski et al., 2008; Ikuma et al., 2012, 2013a, 2013b, 2014; Karakozoglou et al., 2012; Krenmayr et al., 2012; Kunduk et al., 2012; Mehta et al., 2011
High-speed digital endoscopy	Döllinger, 2009
Ultra-rapid cinematography	Chevaillier et al., 2010
High-speed endoscopy	Döllinger et al., 2012
High-speed videolaryngoscopy	Bohr et al., 2014; Pinheiro et al., 2014

Note. Ordering is by earliest publication year.

^aRecommended terminology.

What is clear from the list and the selected references is the necessity of including the modifier high-speed to clarify that the object of interest (vocal fold tissue) is being captured at a rate faster than the eye can see and faster than conventional video-recording technology because the object itself is moving at such a rapid rate. Although we acknowledge that high-speed is a relative adjective (today's high speed is often tomorrow's slow speed), the descriptor indicates to the reader that the recording mode is in the general category of high–frame rate imaging. In addition, it is important to note that the HSV modality is inherently in the category of non-real-time imaging in regard to the necessity of slow-motion video playback; in contrast, although other modalities, such as videostroboscopy, may also be played back in slow motion, these modalities are primarily designed to be displayed to the viewer in real time to allow for the simultaneous auditory evaluation of voice quality (Mehta & Hillman, 2012).

To date, practically all technologies for imaging the temporal details of vocal fold vibration make use of high-speed video cameras coupled to an endoscope that is inserted transorally or transnasally to view the laryngeal anatomy. Thus, it might not seem necessary to specify the term endoscopy in describing the technology. However, in all likelihood it will simply be a matter of time before other imaging modalities—optical coherence tomography, ultrasound, magnetic resonance imaging, and the like—will catch up in regard to image sampling rate. When that occurs, general terms such as digital imaging will lose their uniqueness in describing a particular imaging modality. Specifying endoscopy in the terminology is thus necessary to take this eventuality into account. Even today, high-speed cameras are being used to image everything from the beating of butterfly wings to airbags deployed during vehicle crash testing, and drawing clear distinctions among these applications is already necessary. Also, high-speed video cameras have been all-digital for decades, and certainly they have been digital since the very first time video cameras were used for laryngeal high-speed endoscopic recordings (Hess & Gross, 1993; Kiritani et al., 1993; Wittenberg et al., 1995). Finally, specifying the term imaging does not add information but rather creates ambiguity, because biomedical professionals are accustomed to relating this term to techniques based on non-optical principles—such as gamma ray, ultrasound, or nuclear-magnetic resonance—that also require some method of image reconstruction.

Inclusion of the term video in our terminology makes an important distinction in disambiguating the term high-speed, which by itself could refer to methods based on electronic versus non-electronic principles or optical versus non-optical principles (e.g, high-speed photography, high-speed magnetic resonance imaging, or high-speed video). Although an ingenious technique of revealing previously invisible characteristics, high-speed photography is inherently designed to freeze the rapid motion of an object and capture a single snapshot in time (think of Harold Edgerton's bullet through an apple). High-speed video, however, specifies that more than a few quick image bursts are captured because a video is a sequence of images that reflect the natural and observable temporal progression of a moving object. Specifically, the Society of Motion Picture & Television Engineers (White Plains, NY) defines video as “the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of optical still images representing scenes in motion” (quoted in Watson & Hill, 2012, p. 314). Thus, animated films or sequences of pictures (as in a slideshow) are not videos. Because the definition also limits a video to having captured a singular event, the concatenation of videos taken at different points in time is not a video anymore; it is then considered a movie (motion picture). Note that, in clinical voice assessment, the use of video in the term videostroboscopy is appropriate because stroboscopic sampling (albeit performed at non-uniform intervals) occurs in time order to capture a sequence of observable images. However, analog film-based high-speed motion picture/photography technology (Brubaker & Holinger, 1947; Farnsworth, 1940; Herriott & Farnsworth, 1938; Moore, White, & Von Leden, 1962) is not considered video because those cameras did not electronically capture video images; instead, they used mechanical and chemical methods to expose film for the capture and saving of images.

Laryngeal HSV thus strikes a balance between conciseness and specificity when referring to the currently typical high-speed imaging method performed on human participants. Terms such as high-speed videolaryngoscopy (or with variants such as videostrobolaryngoscopy and strobovideolaryngoscopy) may be considered unwieldy. In addition, because the technique itself may be succinctly referred to as HSV, the acronym HSV remains flexible so it can be qualified by other anatomical terms to describe the body part being imaged (e.g., heart valve HSV, velar HSV, or tongue HSV).

We hope that this brief letter provides clarity and context to the terminology chosen and guidance for the creation of future terminology. The suggested HSV terminology has been adopted by an ad hoc committee of the American Speech-Language-Hearing Association that is developing recommended protocols for instrumental voice assessment and protocols for endoscopic, acoustic, and aerodynamic assessment of voice (see Ad Hoc Committee on Developing Instrumental Voice Assessment Protocols, http://www.asha.org/About/governance/committees/Active-Ad-Hoc-Committees/). The committee is composed of research scientists and clinicians with international representation and backgrounds spanning voice science, speech-language pathology, otolaryngology, physics, and engineering.

Funding Statement

This work was supported by a grant from the National Institute on Deafness and Other Communication Disorders (R01 DC007640), awarded to Dimitar D. Deliyski, and by the Voice Health Institute.