Simple Magnetic Swallowing Detection System

A magnetic swallowing-detection system that can detect swallowing sounds and measure the distance between two magnetic coils was developed to detect the swallowing function non-invasively. The coils were set on both sides of the thyroid cartilage, and the distance between them changes in accordance with the movement of the thyroid cartilage. Swallowing sounds were detected by a piezoelectric microphone attached to the neck. The coils and microphone were installed in a holding unit that can be positioned at the front of the neck. The system was simultaneously used with videofluorography (VF) to measure nine healthy subjects while they swallowed liquid barium. To evaluate the correlation between the swallowing event detected by the magnetic swallowing-detection system and the swallowing event obtained from VF, two-dimensional positions of the hyoid bone in each VF image were detected. Based on the detection results, the swallowing starting time that was detected by the magnetic swallowing-detection system coincided with that determined from VF, namely, 38±172 ms. The coincidence among the peak time point of VF, that of the distance between the magnetic coils, and that of the swallowing sound appeared to have an intraclass correlation coefficient of 0.9. Correlation between the peak time points of the VF tracking waveforms, the peak time points of distance between the magnetic coils, and the peak timing of the swallowing sound had an intraclass correlation coefficient of 0.9. It can be concluded that the magnetic swallowing-detection system can detect swallowing movements simply and non-invasively without x-ray exposure.