Application of MR elastography (MRE) to measure oral posture related changes in the stiffness of the zygomaticus major muscle

Motivation: The MR elastography (MRE) phase-gradient (PG) technique allows measurement of tissue stiffness for small structures. Goal(s): To use the PG technique to measure oral postural related changes in stiffness of the zygomaticus major (ZM) muscle in a small cohort of participants. Approach: The phase image of the first harmonic of Fourier-transformed, directionally filtered MRE wave images was analysed. The gradient of the change in phase along a 1D-profile drawn in the direction of the long axis of ZM corresponds to the wavenumber and provides a measure of ZM stiffness. Results: ZM stiffness increased significantly in mouth-open posture compared to mouth-closed posture. Impact: The feasibility of using the PG technique to measure oral posture related changes in the stiffness of ZM has been demonstrated. The method can potentially be applied to support the development of surgical treatments to rectify impaired oral posture.