Current role of stroboscopy in laryngeal imaging

Abstract

Purpose of review: To summarize recent technological advancements and insight into the role of stroboscopy in laryngeal imaging.

Recent findings: Although stroboscopic technology has not undergone major technological improvements, recent clarifications have been made to the application of stroboscopic principles to video-based laryngeal imaging. Also recent advances in coupling stroboscopy with high-definition video cameras provide higher spatial resolution of vocal fold vibratory function during phonation. Studies indicate that the interrater reliability of visual stroboscopic assessment varies depending on the laryngeal feature being rated and that only a subset of features may be needed to be representative of an entire assessment. High-speed videoendoscopy (HSV) judgments have been shown to be more sensitive than stroboscopy for evaluating vocal fold phase asymmetry, pointing to the future potential of complementing stroboscopy with alternative imaging modalities in hybrid systems. Laryngeal videostroboscopy alone continues to play a central role in clinical voice assessment. Even though HSV may provide more detailed information about phonatory function, its eventual clinical adoption will depend on how remaining practical, technical, and methodological challenges will be met.

Summary: Laryngeal videostroboscopy continues to be the modality of choice for imaging vocal fold vibration, but technological advancements in HSV and associated research findings are driving increased interest in the clinical adoption of HSV to complement videostroboscopic assessment.

Figure 1

Comparison of the spatial resolution of still frames captured using (A) standard-definition (720 × 480 pixels) videostroboscopy and (B) high-definition (1920 × 1080 pixels) videostroboscopy obtained with rigid endoscopy of normal adult males. A selected segment of the vocal fold edge in each exam is magnified (14x) to illustrate the increased pixelation that occurs in the standard-definition image. High-definition frame courtesy of KayPENTAX Corporation.

Figure 2

Stroboscopy Evaluation Rating Form developed by Poburka [13], whose interrater reliability was evaluated by Nawka and Konerding [15]. Continued on following page.

Figure 2

Stroboscopy Evaluation Rating Form developed by Poburka [13], whose interrater reliability was evaluated by Nawka and Konerding [15]. Continued on following page.

Figure 3

Dual rigid endoscopy of a vocally normal speaker sustaining a vowel. Each row of HSV frames depicts one cycle of vocal fold vibration. White boundaries indicate the durations of NTSC video fields, during which one strobe is flashed to capture advancing phases in the glottal cycle. With the phonatory fundamental frequency at 236 Hz, one videostroboscopic frame (comprising two fields) would be composed every eight cycles. 477 frames are displayed, representing 76.32 ms of time. Modified version of Figure 11.4 in [10].