Abstract:
Few studies have attempted to quantify the relative contributions of individual tongue muscles to the overall function of the tongue during swallowing, speech or respiration. The aim of this thesis is to analyse the multi-fibre mechanics of the tongue using an anatomically-realistic Finite Element (FE) tongue model. Outcomes of this thesis include new methods to investigate the underlying mechanisms of tongue muscle mechanics during various functional activities. The FE model of the tongue was first applied to find the optimal motion sensor placement for electromagnetic articulography during tongue elongation and retraction based on a forward problem analysis. Two optimal criteria for selecting sensor arrays were proposed: (1) the largest displacements containing the most information and (2) the largest displacements in the anatomical axial and overall directions. The inverse problem method was adopted to derive the contractile state of muscles for given kinematic data and thus, test the quality of sensor placement. The results showed that, under the influence of machine-inherent noise, the first optimality criteria was superior to the second, and the average bias and coefficient of variation decreased with an increasing number of sensors from 2, 4 to 6. In a second study, the FE tongue model was applied to identify possible muscle activity patterns during propulsion of dry swal- lowing based on an extended inverse problem analysis and tagged-MRI data from the literature. The computational results suggested: (1) previous literature hypotheses lacked consideration of the heterogeneous orientation of the transversus muscle in the posterior region compared to the middle and anterior regions, and (2) co-contractions of the hyoglossus, mylohyoid, styloglossus and the anterior-middle part of the transversus resulted in the best match of tongue deformation during propulsion of dry swallowing when compared with the experimentally acquired strain data from the literature. Two applications in this work demonstrate that the anatomically-realistic FE tongue model enables the quantitative study of muscular activities and geometric deformations of the tongue for various physiological activities. The future application of the FE model to broader areas, such as pathological tongue function or model-aided instrumentation design, is feasible.