The Haskins Optically Corrected Ultrasound System (HOCUS)

Abstract

The tongue is critical in the production of speech, yet its nature has made it difficult to measure. Not only does its ability to attain complex shapes make it difficult to track, it is also largely hidden from view during speech. The present article describes a new combination of optical tracking and ultrasound imaging that allows for a noninvasive, real-time view of most of the tongue surface during running speech. The optical system (Optotrak) tracks the location of external structures in 3-dimensional space using infrared emitting diodes (IREDs). By tracking 3 or more IREDs on the head and a similar number on an ultrasound transceiver, the transduced image of the tongue can be corrected for the motion of both the head and the transceiver and thus be represented relative to the hard structures of the vocal tract. If structural magnetic resonance images of the speaker are available, they may allow the estimation of the location of the rear pharyngeal wall as well. This new technique is contrasted with other currently available options for imaging the tongue. It promises to provide high-quality, relatively low-cost imaging of most of the tongue surface during fairly unconstrained speech.

Indexing head movement during speech production using optical markers

“…While the helmet-attached probe avoids the issue of immobilization, it can cause discomfort and has still been found to shift up to 10 mm (Scobbie et al, 2008). The second approach is head-correction (Whalen et al, 2005;Aron et al, 2006), which leaves the head and jaw more free to move by tracking the relative position of the head and probe using optical markers, but use of a tiara shares the potential discomfort of helmet-mounted probes. Since there was no material difference in accuracy between using forehead-affixed optical markers and markers affixed to a headmounted tiara, the head-correction approach can be improved by using foreheadaffixed optical markers, which simplifies the experimental setup and avoids potential participant discomfort.…”

“…For example, Dohen et al (2004) used points on glasses to measure jaw aperture relative to the head. Whalen et al (2005) proposed using visual markers affixed to either head-mounted goggles or some other head-mounted device during the collection of ultrasound data of the tongue to place tongue contours into a coordinate system relative to the palate during post-processing. By using multiple markers, this approach allows tracking of both the positional and rotational movements of the head, but it is also unknown whether and how much such an apparatus moves relative to the skull.…”

Speech production after glossectomy: Methodological aspects

“…The presence of oedema in the first post-surgery condition prevents from having the same position of the probe across assessment conditions due to the temporary swelling of the neck. Solutions based on optical measures have also been proposed (Whalen et al, 2005). However, this experimental set-up was not available for this study.…”

Measuring lingual coarticulation from midsagittal tongue contours: Description and example calculations using English /t/ and /ɑ/

“…Nor is there, at the time of writing, an ultrasound system synchronised with audio, which can rival EMA in its time resolution. However, ultrasound has proved a convenient and effective technique for imaging a large, continuous portion of the tongue surface (see, e.g., Stone 1999;Iskarous 2005;Whalen et al 2005;Stone 2005). It is comparatively non-invasive, inexpensive and undemanding of participants.…”