Modeling tongue surface contours from Cine-MRI images

This study demonstrated that a simple mechanical model of global tongue mov ement in parallel sagittal planes could be used to quantify tongue motion d uring speech. The goal was to represent simply the differences in 2D tongue surface shapes and positions during speech movements and in subphonemic sp eech events such as coarticulation and left-to-right asymmetries. The study used tagged Magnetic Resonance Images to capture motion of the tongue duri ng speech. Measurements were made in three sagittal planes (left, Midline, right) during movement from consonants (/k/, /s/) to vowels (/i/, /a/, /u/) . MR image-sequences were collected during the C-to-V movement. The image-s equence had seven time-phases (frames), each 56 ms in duration. A global model was used to represent the surface motion. The motions were d ecomposed into translation, rotation, homogeneous stretch, and in-plane she ar. The largest C-to-V shape deformation was from /k/ to /a/. It was compos ed primarily of vertical compression, horizontal expansion, and downward tr anslation. Coarticulatory effects included a trade-off in which tongue shap e accommodation was used to reduce the distance traveled between the C and V. Left-to-right motion asymmetries may have increased rate of motion by re ducing the amount of mass to be moved.