Development of a real-time tongue motion monitoring system for managing swallowing-induced motion in neck cancer radiation therapy

Abstract

Background Swallowing-induced anatomical motion can compromise the accuracy of head-and-neck radiotherapy, underscoring the need for proactive motion management. Because tongue motion precedes laryngeal displacement, it may serve as a predictive signal for swallowing onset.Objective To develop and evaluate a real-time tongue-motion monitoring system and assess its utility for predicting swallowing-induced motion in radiotherapy.Methods The system comprised a gas-pressure module that measures intra-oral pressure (a surrogate for tongue motion) and an IR-marker tracking module for laryngeal motion. Reliability testing (accuracy and repeatability) was conducted for both modules. Synchronized acquisition was verified by analyzing peak-time differences between paired signals to exclude inter-module delay. A volunteer study (n = 14) quantified the temporal relationship between intra-oral pressure and laryngeal motion.Results The developed real-time tongue-motion monitoring system demonstrated reliable performance. In volunteers, tongue motion consistently preceded laryngeal motion, with per-volunteer medians of 0.405-0.805 s (predominantly 0.5-0.7 s), supporting its validity as a predictive signal for swallowing onset.Conclusions Real-time tongue-motion monitoring provides a predictive signal for swallowing onset and can aid management of swallowing-induced motion in head-and-neck radiotherapy. By enabling early detection of swallowing events, the system has the potential to reduce dose-delivery errors and improve treatment accuracy.