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

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.