Potential of surface laser scanning to measure facial movement

Juvenile Facial Growth and Mimicry: A Preliminary 3D Study

Studies focused on facial development during childhood have been conducted by means of 3D technology to provide modifications of anthropometric parameters. Facial mobility was also considered. This study proposed a 3D approach to facial growth changes. Facial surface data of 6 subjects were acquired in T1 (age 7-14 years) and after 7 years (T2), in rest position, and during voluntary movements, by a 3D laser scanner. Linear and angular measurements on rest position scans at T1 and T2 were compared. Each mimic scan was superimposed with the corresponding rest scan. Displacement of significant anthropometric points was measured for each facial gesture and at T1 and T2 statistically compared. Vertical measurements were those most influenced by aging. Some measurements of central facial area were consistent over time. The pattern of soft tissues displacement for each expression was consistent in T1 and T2. These results may be helpful for missing children identification.

Evaluation of the Reproducibility of Nonverbal Facial Expressions Using a 3D Motion Capture System

Objective

To evaluate the reproducibility of three nonverbal facial expressions using a three-dimensional motion capture system.

Design

Prospective, cross-sectional, controlled study.

Setting

Glasgow Dental Hospital and School, University of Glasgow, United Kingdom.

Patients and Participants

Thirty-two subjects, 16 males and 16 females.

Methods

With a three-dimensional video passive stereophotogrammetry imaging system, maximal smile, cheek puff, and lip purse were captured for each subject. Anatomical facial landmarks were digitized on the first frame and then tracked automatically. The same facial expressions were captured 15 minutes later.

Main Outcome Measures

The magnitude of each expression and speed of landmark displacement were calculated. The landmark motion curves were spatially and temporally aligned to calculate the similarity of the dynamic movements of the same landmarks between the captures.

Results

There were no significant differences between individuals for magnitude ( P = .892) or for speed ( P = .456). There were significant differences in landmark movement similarity ( P = .011); similarity was more reproducible for maximal smile. There was no significant gender effect on the difference in magnitude. There was a significant gender effect on speed to reach maximal smile ( P = .044) and a pursed-lip expression ( P = .038). There was a significant gender effect on landmark movement similarities ( P = .031) for cheek puff expression.

Conclusions

There were no differences in magnitude and speed for maximal smile, cheek puff, and lip purse between the two captures for all participants. For individual expressions, maximal smile expression had the highest similarity value for individual landmarks.

Three-dimensional facial simulations and measurements: changes of facial contour and units associated with facial expression

Recent innovations in laser scanning technology provide a potentially useful technique for accurate three-dimensional documentation of the face. In this study, linear and area measurements of the facial contour and facial units have been recorded in a variety of chosen facial postures using surface laser scanning combined with three-dimensional lighting techniques on seven healthy volunteers and three patients with facial nerve paralysis. Three-dimensional surface measurement of the face was taken using a laser light scanner. Computer graphics lighting techniques were used to produce facial images constituted by highlights and shadows, which emboss facial contour and units. Then quantitative measurement of changes in facial angles and areas were made to analyze morphological changes of the face accompanying facial expression. Changes of angles and widths of the cheek and nasal units were found to be associated with dimensional changes imposed by the action of the underlying mimetic muscles. This system has potential value for both dynamic monitoring and evaluation of facial contour, units, and movement.

Novel technique for three-dimensional visualisation and quantification of deformable, moving soft-tissue body parts

BACKGROUND

Three-dimensional (3D) imaging of delicate, moving soft-tissue body parts is very difficult. Our understanding of the muscles that control lip movements is based largely on histological and cadaveric studies, which provide scant information about dynamic morphology. Our aim was to develop an innovative scanning technique for the imaging and reconstruction of dynamic orofacial morphology by use of 3D and four-dimensional (4D, ie, 3D plus time) ultrasonography.

METHODS

Four volunteers (including one patient) underwent ultrasonography with 3D/4D imaging systems. To avoid deformation of the delicate orofacial structures, a water bath with an acoustic window was devised. The orofacial part was immersed in the bath throughout scanning, and a timer was used to synchronize lip movements with the 4D scan.

FINDINGS

4D views showed the functional differences in superficial and deep muscle groups of the lips, and clearly showed the changes occurring with movement of the lips and mouth. In the patient, a pathological layer and its extension corresponding to surface malformation were clearly identified.

INTERPRETATION

We have developed a prototype device that has made possible 3D and 4D examination of orofacial anatomy and function. With further refinement of the device and improvement in 4D acquisition timing, this technique may offer a new way of dynamically imaging and quantifying many soft-tissue parts in 3D without deforming structure or disturbing function.

Sensitivity of a method for the analysis of facial mobility. II. Interlandmark separation

OBJECTIVE

This study demonstrates a method of quantifying facial movements based on distortions of the skin surface.

DESIGN

Landmarks were identified on the faces of five healthy human subjects (2 men and 3 women; mean age, 27.6 years; range, 26 to 29 years), and the distortions were characterized by changes in the separation between 20 pairs of landmark distances during specific maximal facial animations: smile, lip purse, cheek puff, grimace, eye closure, and eye opening. Data were recorded with a video-based tracking system for a period of 3 seconds at a sampling rate of 60 Hz or frames per second. For each subject, we analyzed the change in the separation of 20 pairs of landmarks, of which the majority were bilaterally symmetrical and functionally active.

RESULTS

Characteristic patterns of movement emerged for each animation. We found that smiling involved movements of the lateral orbital, circumoral, and chin regions; grimacing involved the inner orbital, lateral orbital, lateral nasal, and upper-lip regions; eye closure involved the inner orbital, lateral orbital, and, to a lesser degree, lateral nasal regions; eye opening involved the inner and lateral orbital regions; cheek puffing involved the cheek and lower-lip regions; and the lip purse animation involved the nasolabial, cheek, commissure, and lip regions.

CONCLUSION

This measurement of distortion provided a quantitative estimate of facial movement, and this approach is especially applicable to patients with unilateral problems in which the patient can serve as his or her own control.

Sensitivity of a method for the analysis of facial mobility. I. Vector of displacement

OBJECTIVE

(1) To determine which facial landmarks show the greatest movement during specific facial animations and (2) to determine the sensitivity of our instrument in using these landmarks to detect putatively abnormal facial movements.

DESIGN

Movements of an array of skin-based landmarks on five healthy human subjects (2 men and 3 women; mean age, 27.6 years; range, 26 to 29 years) were observed during the execution of specific facial animations. To investigate the instrument sensitivity, we analyzed facial movements during maximal smile animations in six patients with different types of functional problems. In parallel, a panel was asked to view video recordings of the patients and to rate the degree of motor impairment. Comparisons were made between the panel scores and those of the measurement instrument.

RESULTS

Specific regions of the face display movement that is representative of specific animations. During the smile animation, landmarks on the mid- and lower facial regions demonstrated the greatest movement. A similar pattern of movement was seen during the cheek puff animation, except that the infraorbital and chin regions demonstrated minimal movement. For the grimace and eye closure animations, the upper, mid-facial, and upper-lip regions exhibited the greatest movement. During eye opening, the upper and mid-facial regions, excluding the upper lip and cheek, moved the most, and during lip purse, markers on the mid- and lower face demonstrated the most movement. We used the smile-sensitive landmarks to evaluate individuals with functional impairment and found good agreement between instrument rankings based on the data from these landmarks and the panel rankings.

CONCLUSION

The present method of three-dimensional tracking has the potential to detect and characterize a range of clinically significant functional deficits.