Quantitative measurement of functional and anatomical traits of 4D tonguemotion in the course of speech or other lingual behaviors remains a majorchallenge in scientific research and clinical applications. Here, we introducea statistical multimodal atlas of 4D tongue motion using healthy subjects thatenables a combined quantitative characterization of tongue motion in areference anatomical configuration. This atlas framework, termed speech map,combines cine- and tagged-MRI in order to provide both the anatomic referenceand motion information during speech. Our approach involves a series of stepsincluding (1) construction of a common reference anatomical configuration fromcine-MRI, (2) motion estimation from tagged-MRI, (3) transformation of themotion estimations to the reference anatomical configuration, (4) correction ofpotential time mismatch across subjects, and (5) computation of motionquantities such as Lagrangian strain. Using this framework, the anatomicconfiguration of the tongue appears motionless, while the motion fields andassociated strain measurements change over the time course of speech. Inaddition, to form a succinct representation of the high-dimensional and complexmotion fields, principal component analysis is carried out to characterize thecentral tendencies and variations of motion fields of our speech tasks. Ourproposed method provides a platform to quantitatively and objectively explainthe differences and variability of tongue motion by illuminating internalmotion and strain that have so far been intractable. The findings are used tounderstand how tongue function for speech is limited by abnormal internalmotion and strain in glossectomy patients.
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