Combining MRI, EMA and EPG measurements in a three-dimensional tongue model

Abstract

A three-dimensional (3D) tongue model has been developed using MR images of a reference subject producing 44 artificially sustained Swedish articulations. Based on the difference in tongue shape between the articulations and a reference, the six linear parameters jaw height, tongue body, tongue dorsum, tongue tip, tongue advance and tongue width were determined using an ordered linear factor analysis controlled by articulatory measures. The first five factors explained 88% of the tongue data variance in the midsagittal plane and 78% in the 3D analysis. The six-parameter model is able to reconstruct the modelled articulations with an overall mean reconstruction error of 0.13 cm, and it specifically handles lateral differences and asymmetries in tongue shape. In order to correct articulations that were hyperarticulated due to the artificial sustaining in the magnetic resonance imaging (MRI) acquisition, the parameter values in the tongue model were readjusted based on a comparison of virtual and natural linguopalatal contact patterns, collected with electropalatography (EPG). Electromagnetic articulography (EMA) data was collected to control the kinematics of the tongue model for vowel-fricative sequences and an algorithm to handle surface contacts has been implemented, preventing the tongue from protruding through the palate and teeth.