Error analysis of extracted tongue contours from 2d ultrasound images

The goal of this study was to characterize errors involved in obtaining midsagittal tongue contours from two-dimensional ultrasound image sequences. Toward that end, two basic experiments were conducted. First, manual tongue contours were obtained from 1,145 tongue ultrasound images recorded from four speakers during production of the sentence ‘I owe you a yoyo’, and the uncertainty associated with the contours was quantified. Second, tongue contours from the same images were obtained using the EdgeTrak, TongueTrack, and AutoTrace algorithms, and these were compared quantitatively with the manual tongue contours. Three basic error types associated with the tongue contours are identified, indicating areas in need of improvement in future algorithmic developments. Depending on the speaker, RMS errors for the algorithmically obtained contours ranged from 1.76 to 7.11 mm, and the standard deviation of manual contours ranged from 0.97 to 2.07 mm.