Tongue muscle strain analysis from multimodal MRI (Shao et al., 2023)

Purpose: Muscle groups within the tongue in healthy and diseased populations show different behaviors during speech. Visualizing and quantifying strain patterns of these muscle groups during tongue motion can provide insights into tongue motor control and adaptive behaviors of a patient.

Method: We present a pipeline to estimate the strain along the muscle fiber directions in the deforming tongue during speech production. A deep convolutional network estimates the crossing muscle fiber directions in the tongue using diffusion-weighted magnetic resonance imaging (MRI) data acquired at rest. A phase-based registration algorithm is used to estimate motion of the tongue muscles from tagged MRI acquired during speech. After transforming both muscle fiber directions and motion fields into a common atlas space, strain tensors are computed and projected onto the muscle fiber directions, forming so-called strains in the line of actions (SLAs) throughout the tongue. SLAs are then averaged over individual muscles that have been manually labeled in the atlas space using high-resolution T2-weighted MRI. Data were acquired, and this pipeline was run on a cohort of eight healthy controls and two glossectomy patients.

Results: The crossing muscle fibers reconstructed by the deep network show orthogonal patterns. The strain analysis results demonstrate consistency of muscle behaviors among some healthy controls during speech production. The patients show irregular muscle patterns, and their tongue muscles tend to show more extension than the healthy controls.

Conclusions: The study showed visual evidence of correlation between two muscle groups during speech production. Patients tend to have different strain patterns compared to the controls. Analysis of variations in muscle strains can potentially help develop treatment strategies in oral diseases.

Supplemental Material S1. Histograms of the bottom and top 10% SLA values along the 1st and 2nd fiber directions from /ə/ to /θ/, /i/, and /ŋ/. The control data are grouped together. The ratio of the flap volume to the whole tongue volume is 0.17 and 0.26 for Patient 1 and 2, respectively.

Shao, M., Xing, F., Carass, A., Liang, X., Zhuo, J., Stone, M., Woo, J., & Prince, J. L. (2023). Analysis of tongue muscle strain during speech from multimodal magnetic resonance imaging. Journal of Speech, Language, and Hearing Research, 66(1), 513–526. https://doi.org/10.1044/2022_JSLHR-22-00329