An instrument for the non-invasive assessment of lip function during speech

The clinical application of three-dimensional motion capture (4D): a novel approach to quantify the dynamics of facial animations

The aim of this pilot study was to evaluate the feasibility of measuring the change in magnitude, speed, and motion similarity of facial animations in head and neck oncology patients, before and after lip split mandibulotomy. Seven subjects (four males, three females) aged 42-80 years were recruited. The subjects were asked to perform four facial animations (maximal smile, lip purse, cheek puff, and grimace) from rest to maximal position. The animations were captured using a Di4D motion capture system, which recorded 60 frames/s. Nine facial soft tissue landmarks were manually digitized on the first frame of the three-dimensional image of each animation by the same operator and were tracked automatically for the sequential frames. The intra-operator digitization error was within 0.4mm. Lip purse and maximal smile animations showed the least amount of change in magnitude (0.2mm) following surgery; speed difference was least for smile animation (-0.1mm/s). Motion similarity was found to be highest for lip purse animation (0.78). This pilot study confirmed that surgery did influence the dynamics of facial animations, and the Di4D capture system can be regarded as a feasible objective tool for assessing the impact of surgical interventions on facial soft tissue movements.

A geometric morphometric approach to the analysis of lip shape during speech: development of a clinical outcome measure

Objective assessments of lip movement can be beneficial in many disciplines including visual speech recognition, for surgical outcome assessment in patients with cleft lip and for the rehabilitation of patients with facial nerve impairments. The aim of this study was to develop an outcome measure for lip shape during speech using statistical shape analysis techniques. Lip movements during speech were captured from a sample of adult subjects considered as average using a three-dimensional motion capture system. Geometric Morphometrics was employed to extract three-dimensional coordinate data for lip shape during four spoken words decomposed into seven visemes (which included the resting lip shape). Canonical variate analysis was carried out in an attempt to statistically discriminate the seven visemes. The results showed that the second canonical variate discriminated the resting lip shape from articulation of the utterances and accounted for 17.2% of the total variance of the model. The first canonical variate was significant in discriminating between the utterances and accounted for 72.8% of the total variance of the model. The outcome measure was created using the 95% confidence intervals of the canonical variate scores for each subject plotted as ellipses for each viseme. The method and outcome model is proposed as reference to compare lip movement during speech in similar population groups.

A comparison of the reproducibility of verbal and nonverbal facial gestures using three-dimensional motion analysis

Objective: To evaluate the reproducibility of selected verbal and nonverbal facial gestures.

Study Design: Cross-sectional study.

Setting: School of Dentistry, Cardiff University, Cardiff, United Kingdom.

Subjects and Methods: Twenty-five white subjects were asked to perform four verbal gestures and two nonverbal facial gestures in a normal, relaxed manner. The sequences were captured using a noninvasive, three-dimensional motion analysis scanner (3dMDFace Dynamic System; 3Q Technologies, Atlanta, GA) at an initial time point (T1) and one month later (T2). Principal component analysis was used to analyze the dynamics of lip movement, and dynamic time warping was used to evaluate the reproducibility between T1 and T2 for the individual facial gestures. Statistical analyses were used to compare the reproducibility of the different facial gestures.

Results: All four verbal gestures were found to be significantly more reproducible than the nonverbal gestures. The word “puppy” was most reproducible, and the normal smile expression least reproducible. A hierarchy of reproducibility is proposed as “puppy,” “baby,” “rope,” “bob,” standardized smile, normal smile.

Conclusion: Verbal facial gestures, in particular the words “puppy” and “baby,” are more appropriate for use in the assessment of lip movement when compared with smile expressions because of their high level of reproducibility over a one-month period.