Development of a spring-loaded headset for enhanced mandibular tracking for ultrasound tongue imaging

Measurement of tongue movement using ultrasonography requires close contact of the probe with the submandibular region. Ideally, the probe should follow the mandible’s movement during speech while maintaining a constant relative position to it. However, conventional devices often attach the probe to an inflexible arm mounted on a headset. This design impedes mandibular movement or causes the probe to shift, creating a shift in the origin of the images. We developed a prototype headset with a spring that allows the probe to follow the vertical mandibular movement. We assessed the effectiveness of the prototype by comparing the mandibular and probe movement using the conventional and prototype headsets when a Japanese speaker spoke /ai/, /apa/, /ata/, and /aka/. As a result, for the conventional headset, the probe moved 11.1 mm anteroposteriorly and 5.9 mm vertically for the mandibular tip movements of 12.0 and 17.6 mm, respectively. In contrast, for the prototype, the probe moved 9.5 mm anteroposteriorly and 13.1 mm vertically for the mandibular tip movements of 11.2 and 17.0 mm, respectively. The increased vertical movement of the probe for the prototype is attributed to the spring mechanism and it makes the probe movement closer to the mandibular movement.