Stereo Laryngoscopic Impact Site Prediction for Droplet-Based Stimulation of the Laryngeal Adductor Reflex

Abstract

The laryngeal adductor reflex (LAR) is a vital reflex of the human larynx. LAR malfunctions may cause life-threatening aspiration events. An objective, noninvasive, and reproducible method for LAR assessment is still lacking. Stimulation of the larynx by droplet impact, termed Microdroplet Impulse Testing of the LAR (MIT-LAR), may remedy this situation. However, droplet instability and imprecise stimulus application thus far prevented MIT-LAR from gaining clinical relevance. We present a system comprising two alternative, custom-built stereo laryngoscopes, each offering a distinct set of properties, a droplet applicator module, and image/point cloud processing algorithms to enable a targeted, dropletbased LAR stimulation. Droplet impact site prediction (ISP) is achieved by droplet trajectory identification and spatial target reconstruction. The reconstruction and ISP accuracies were experimentally evaluated. Global spatial reconstruction errors at the glottal area of (0.3 ± 0.3) mm and (0.4 ± 0.3) mm and global ISP errors of (0.9 ± 0.6) mm and (1.3 ± 0.8) mm were found for a rod lens-based and an alternative, fiberoptic laryngoscope, respectively. In the case of the rod lens-based system, 96 % of all observed ISP error values are inferior to 2 mm; a value of 80 % was found with the fiberoptic assembly. This contribution represents an important step towards introducing a reproducible and objective LAR screening method into the clinical routine.INDEX TERMS Aspiration, biomedical engineering, computer aided diagnosis, endoscopes, image guidance, laryngeal closure reflex, reflex latency, stereo endoscopy.

Computational Analysis of the Droplet‐Stimulated Laryngeal Adductor Reflex in High‐Speed Sequences

“…However, this issue can be reduced by controlling droplet formation as described in our previous work 41 . Future iterations of the MIT‐LAR system will also benefit from our recent work on stereoscopic droplet impact site prediction 42,43 …”

“…41 Future iterations of the MIT-LAR system will also benefit from our recent work on stereoscopic droplet impact site prediction. 42,43 The performance of the proposed workflow is limited in cases of very small or unusually shaped glottal areas. The segmentation procedure can also be disturbed by foreign objects (mucus/stimulation droplets) in the glottal region.…”