Quantification of Facial Movements by Surface Laser Scanning

Novel evaluation method for facial nerve palsy using 3D facial recognition system in iPhone

OBJECTIVE

While subjective methods like the Yanagihara system and the House-Brackmann system are standard in evaluating facial paralysis, they are limited by intra- and inter-observer variability. Meanwhile, quantitative objective methods such as electroneurography and electromyography are time-consuming. Our aim was to introduce a swift, objective, and quantitative method for evaluating facial movements.

METHODS

We developed an application software (app) that utilizes the facial recognition functionality of the iPhone (Apple Inc., Cupertino, USA) for facial movement evaluation. This app leverages the phone's front camera, infrared radiation, and infrared camera to provide detailed three-dimensional facial topology. It quantitatively compares left and right facial movements by region and displays the movement ratio of the affected side to the opposite side. Evaluations using the app were conducted on both normal and facial palsy subjects and were compared with conventional methods.

RESULTS

Our app provided an intuitive user experience, completing evaluations in under a minute, and thus proving practical for regular use. Its evaluation scores correlated highly with the Yanagihara system, the House-Brackmann system, and electromyography. Furthermore, the app outperformed conventional methods in assessing detailed facial movements.

CONCLUSION

Our novel iPhone app offers a valuable tool for the comprehensive and efficient evaluation of facial palsy.

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.

Accuracy evaluation of tridimensional images performed by portable stereophotogrammetric system

Abstract Introduction Human facial characteristics vary according to individual dental occlusion, facial harmony, orofacial musculature and the format and configuration of craniofacial structures. Traditionally, anthropometric measurements have been acquired through direct evaluation of subjects in a clinical environment using calipers and metric tapes to measure distances between arches and landmarks. Scientific breakthroughs have enabled the digitization of data and introduced the possibility of quick, precise, radiation-free acquisitions; details can be archived for future analysis and easily shared with patients and colleagues. Among new facial analysis methods, the stereophotogrammetry technique has emerged, which uses a group of cameras to take many photographs of a subject in rapid succession from multiple angles. Nowadays, portable stereophotogrammetric systems are being proposed, as they are more practical and easier to use. Objective The aim of this work was to analyze the accuracy and reproducibility of a portable 3D stereophotogrammetric system (Vectra H1, Canfield, Fairfield, NJ, USA) in measuring soft facial tissues of 30 participants, defining measures of a cube and comparing these measurements with those obtained by a set 3D stereophotogrammetric system (Vectra M3, Canfield, Fairfield, NJ, USA) with previously validated accuracy and reproducibility through quantitative analysis of possible errors. Material and method Thirty temporary landmarks were used to measure (in mm) 34 distances in 30 participants (n = 30). Regarding the cube, 12 angles and 9 linear distances were evaluated. Result The results obtained by the established methodology indicated that the Vectra H1 portable system has shown accuracy and reproducibility equal to that of the Vectra M3 set system. Conclusion Data analysis and correlation to literature findings show Vectra H1's capability to reliably capture tridimensional images, which makes it practical for use in diverse clinical applications.

A Quantitative Assessment of Lip Movements in Different Facial Expressions Through 3-Dimensional on 3-Dimensional Superimposition: A Cross-Sectional Study

PURPOSE

The quantitative assessment of facial modifications from mimicry is of relevant interest for the rehabilitation of patients who can no longer produce facial expressions. This study investigated a novel application of 3-dimensional on 3-dimensional superimposition for facial mimicry.

MATERIALS AND METHODS

This cross-sectional study was based on 10 men 30 to 40 years old who underwent stereophotogrammetry for neutral, happy, sad, and angry expressions. Registration of facial expressions on the neutral expression was performed. Root mean square (RMS) point-to-point distance in the labial area was calculated between each facial expression and the neutral one and was considered the main parameter for assessing facial modifications. In addition, effect size (Cohen d) was calculated to assess the effects of labial movements in relation to facial modifications.

RESULTS

All participants were free from possible facial deformities, pathologies, or trauma that could affect facial mimicry. RMS values of facial areas differed significantly among facial expressions (P = .0004 by Friedman test). The widest modifications of the lips were observed in happy expressions (RMS, 4.06 mm; standard deviation [SD], 1.14 mm), with a statistically relevant difference compared with the sad (RMS, 1.42 mm; SD, 1.15 mm) and angry (RMS, 0.76 mm; SD, 0.45 mm) expressions. The effect size of labial versus total face movements was limited for happy and sad expressions and large for the angry expression.

CONCLUSION

This study found that a happy expression provides wider modifications of the lips than the other facial expressions and suggests a novel procedure for assessing regional changes from mimicry.

Facial Mobility after Maxilla-Mandibular Advancement in Patients with Severe Obstructive Sleep Apnea Syndrome: A Three-Dimensional Study

Introduction. The functional results of surgery in terms of facial mobility are key elements in the treatment of patients. Little is actually known about changes in facial mobility following surgical treatment with maxillomandibular advancement (MMA). Objectives. The three-dimensional (3D) methods study of basic facial movements in typical OSAS patients treated with MMA was the topic of the present research. Materials and Methods. Ten patients affected by severe obstructive sleep apnea syndrome (OSAS) were engaged for the study. Their facial surface data was acquired using a 3D laser scanner one week before (T1) and 12 months after (T2) orthognathic surgery. The facial movements were frowning, grimace, smiling, and lip purse. They were described in terms of surface and landmark displacements (mm). The mean landmark displacement was calculated for right and left sides of the face, at T1 and at T2. Results. One year after surgery, facial movements were similar to presurgical registrations. No modifications of symmetry were present. Conclusions. Despite the skeletal maxilla-mandible expansion, orthognathic surgical treatment (MMA) of OSAS patients does not seem to modify facial mobility. Only an enhancement of amplitude in smiling and knitting brows was observed. These results could have reliable medical and surgical applications.

Validity and intraobserver reliability of three-dimensional scanning compared with conventional anthropometry for children and adolescents from a population-based cohort study

BACKGROUND

Conventional anthropometric measurements are time consuming and require well trained medical staff. To use three-dimensional whole body laser scanning in daily clinical work, validity, and reliability have to be confirmed.

METHODS

We compared a whole body laser scanner with conventional anthropometry in a group of 473 children and adolescents from the Leipzig Research Centre for Civilization Diseases (LIFE-Child). Concordance correlation coefficients (CCC) were calculated separately for sex, weight, and age to assess validity. Overall CCC (OCCC) was used to analyze intraobserver reliability.

RESULTS

Body height and the circumferences of waist, hip, upper arm, and calf had an "excellent" (CCC ≥ 0.9); neck and thigh circumference, a "good" (CCC ≥ 0.7); and head circumference, a "low" (CCC < 0.5) degree of concordance over the complete study population. We observed dependencies of validity on sex, weight, and age. Intraobserver reliability of both techniques is "excellent" (OCCC ≥ 0.9).

CONCLUSION

Scanning is faster, requires less intensive staff training and provides more information. It can be used in an epidemiologic setting with children and adolescents but some measurements should be considered with caution due to reduced agreement with conventional anthropometry.

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.

A finite element model of the face including an orthotropic skin model under in vivo tension

Computer models of the human face have the potential to be used as powerful tools in surgery simulation and animation development applications. While existing models accurately represent various anatomical features of the face, the representation of the skin and soft tissues is very simplified. A computer model of the face is proposed in which the skin is represented by an orthotropic hyperelastic constitutive model. The in vivo tension inherent in skin is also represented in the model. The model was tested by simulating several facial expressions by activating appropriate orofacial and jaw muscles. Previous experiments calculated the change in orientation of the long axis of elliptical wounds on patients' faces for wide opening of the mouth and an open-mouth smile (both 30(o)). These results were compared with the average change of maximum principal stress direction in the skin calculated in the face model for wide opening of the mouth (18(o)) and an open-mouth smile (25(o)). The displacements of landmarks on the face for four facial expressions were compared with experimental measurements in the literature. The corner of the mouth in the model experienced the largest displacement for each facial expression (∼11-14 mm). The simulated landmark displacements were within a standard deviation of the measured displacements. Increasing the skin stiffness and skin tension generally resulted in a reduction in landmark displacements upon facial expression.