Automated detection of the tongue surface in sequences of ultrasound images.

An image processing system has been developed for a Macintosh II personal computer. It is designed to process sequences of sagittal tongue sections that are digitized in real time and stored in standard tagged image file format (TIFF). The successive processing steps are: (a) a low-pass filter for noise reduction, (b) a resampling of the sector of interest in polar coordinates, (c) a matched filter (vertical differentiator) for the enhancement of the tissue/air interface in the surface region of the tongue, and (d) an extraction of border points by searching for an optimal radial path along the angular dimension. This latter task is achieved by dynamic programming, which has the following advantages. First, due to the use of a global criterion to guide the detection, it is very robust. Second, as a result of certain restrictions of the allowable transitions, the extracted contours are smooth. Finally, the method permits the specification of particular predefined contour points. This system was implemented in a program that can handle image sequences in a fully automatic mode. Results obtained using ultrasound data are presented.