Reconstruction of facial morphology from laser scanned data. Part I: reliability of the technique

Current status of optical scanning in facial prosthetics: A systematic review and meta-analysis

Purpose To assess the accuracy of scanning technologies for constructing facial prostheses on human faces.Study selection Our systematic search was performed on five databases. Studies reporting on human volunteers (P) whose faces were scanned with a scanning technology were eligible. The anthropometrical interlandmark distances (ILDs) were used as indicators of accuracy; the ILDs are measured on the virtual models (I) and directly on the faces (C). The virtual models deviated from their true values (O). Studies reporting the measurements on patients with or without facial deformities were included, but cadavers or inanimate objects were reasons for exclusion. We performed a mean difference (MD) / standardized MD analysis with a random effect model. The difficulties regarding the scanning procedure mentioned in the articles were also assessed.Results We found 3723 records after duplicate removal. Twenty five articles were eligible for the qualitative review, and ten articles were included in the quantitative synthesis. Eight different ILDs were compared in MD analyses. The differences were between -0.54-0.43 mm. We also performed a regional three-dimensional analysis to compare scanning technologies in each major region. No significant differences were found in any of the regions and axes. The most mentioned difficulties were artifacts due to motion or blinking.Conclusions The results suggest no systematic skew in linear dimensions neither between direct caliper measurements nor between measurements on the scanned models, scanning technologies, or facial regions.

Facial scanning technologies in the era of digital workflow: A systematic review and network meta-analysis

PURPOSE

The aim of this network meta-analysis is to evaluate the accuracy of various face-scanning technologies in the market, with respect to the different dimensions of space (x, y, and z axes). Furthermore, attention will be paid to the type of technologies currently used and to the best practices for high-quality scan acquisition.

MATERIAL AND METHODS

The review was conducted following the PRISMA guidelines and its updates. A thorough search was performed using the digital databases MEDLINE, PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials by entering research lines or various combinations of free words. The main keywords used during the search process were "photogrammetry", "laser scanner", "optical scanner", "3D, and "face".

RESULTS

None of the included technologies significantly deviated from direct anthropometry. The obtained mean differences in the distances between the considered landmarks range from 1.10 to -1.74 mm.

CONCLUSION

Limiting the movements of the patient and scanner allows for more accurate facial scans with all the technologies involved. Active technologies such as laser scanners (LS), structured light (SL), and infrared structured light (ISL) have accuracy comparable to that of static stereophotogrammetry while being more cost-effective and less time-consuming.

Three-dimensional topography of facial soft tissues for the safer and effective threading procedures

INTRODUCTION

To reduce complications caused by the procedure, the target layer for thread lifting should be the superficial fat or superficial musculoaponeurotic system of the face. The aim of this study was to establish the thicknesses of the facial skin and superficial fat using a 3D scanning system to provide basic clinical data for thread lifting.

MATERIAL AND METHODS

Thirty fixed Korean and Thai cadavers (male: 17, female: 13) were used. The depths of the skin and superficial fat were measured using a three dimensional (3D) structured-light scanner. Facial images of both undissected and removed skin and superficial fat were taken with the 3D scanner. The paths from the temple and the front of the tragus to the infraorbital, perioral, cheek, and mental areas were displayed on the 3D image. The thickness along the path was measured by calculating the difference between the undissected and dissected 3D images.

RESULTS

The means and standard deviations of thicknesses of the skin and superficial fat were 2.1 ± 0.4 mm and 5.2 ± 1.9 mm in the 11 pathways. The facial skin became thicker going toward the lower aspect of the face from temple to infraorbtial and perioral regions. The thickness of the superficial fat around the marionette line showed the biggest change.

CONCLUSIONS

The present findings indicate that a 3D scanning system can yield crucial anatomical information about the thickness of the facial skin and superficial fat for use in various minimally invasive clinical procedures including thread lifting.

Reliability and Agreement of 3D Anthropometric Measurements in Facial Palsy Patients Using a Low-Cost 4D Imaging System

The reliability (precision) and agreement (accuracy) of anthropometric measurements based on manually placed 3D landmarks using the RealSense D415 were investigated in this paper. Thirty facial palsy patients, with their face in neutral (resting) position, were recorded simultaneously with the RealSense and a professional 3dMD imaging system. First the RealSense depth accuracy was determined. Subsequently, two observers placed 14 facial landmarks on the 3dMD and RealSense image, assessing the distance between landmark placement. The respective intra- and inter-rater Euclidean distance between the landmark placements was 0.84 mm (±0.58) and 1.00 mm (±0.70) for the 3dMD landmarks and 1.32 mm (±1.27) and 1.62 mm (±1.42) for the RealSense landmarks. From these landmarks 14 anthropometric measurements were derived. The intra- and inter-rater measurements had an overall reliability of 0.95 (0.87 - 0.98) and 0.93 (0.85 - 0.97) for the 3dMD measurements, and 0.83 (0.70 - 0.91) and 0.80 (0.64 - 0.89) for the RealSense measurements, respectively, expressed as the intra-class correlation coefficient. Determined by the Bland-Altman analysis, the agreement between the RealSense measurements and 3dMD measurements was on average -0.90 mm (-4.04 - 2.24) and -0.89 mm (-4.65 - 2.86) for intra- and inter-rater agreement, respectively. Based on the reported reliability and agreement of the RealSense measurements, the RealSense D415 can be considered as a viable option to perform objective 3D anthropomorphic measurements on the face in a neutral position, where a low-cost and portable camera is required.

Accuracy and reliability of 2-dimensional photography versus 3-dimensional soft tissue imaging

Purpose

This study was conducted to objectively and subjectively compare the accuracy and reliability of 2-dimensional (2D) photography and 3-dimensional (3D) soft tissue imaging.

Materials and Methods

Facial images of 50 volunteers (25 males, 25 females) were captured with a Nikon D800 2D camera (Nikon Corporation, Tokyo, Japan), 3D stereophotogrammetry (SPG), and laser scanning (LS). All subjects were imaged in a relaxed, closed-mouth position with a normal smile. The 2D images were then exported to Mirror® Software (Canfield Scientific, Inc, NJ, USA) and the 3D images into Proplan CMF® software (version 2.1, Materialise HQ, Leuven, Belgium) for further evaluation. For an objective evaluation, 2 observers identified soft tissue landmarks and performed linear measurements on subjects' faces (direct measurements) and both linear and angular measurements on all images (indirect measurements). For a qualitative analysis, 10 dental observers and an expert in facial imaging (subjective gold standard) completed a questionnaire regarding facial characteristics. The reliability of the quantitative data was evaluated using intraclass correlation coefficients, whereas the Fleiss kappa was calculated for qualitative data.

Results

Linear and angular measurements carried out on 2D and 3D images showed excellent inter-observer and intra-observer reliability. The 2D photographs displayed the highest combined total error for linear measurements. SPG performed better than LS, with borderline significance (P=0.052). The qualitative assessment showed no significant differences among the 2D and 3D imaging modalities.

Conclusion

SPG was found to a reliable and accurate tool for the morphological evaluation of soft tissue in comparison to 2D imaging and laser scanning.

Scan time, reliability and accuracy of craniofacial measurements using a 3D light scanner

Aim

To evaluate time, reliability and accuracy of craniofacial measurements with a 3D light scanner, considering prior demarcation of surface points on the face.

Materials and methods

Eleven facial measurements of 15 volunteers were obtained by a scanner (Artec Eva TM) and by a caliper directly on the face, with or without demarcation of facial reference points. Inter and intra-method comparison were examined by intraclass correlation coefficient and analysis of random error by the Dahlberg formula. Agreement between the methods was analyzed by the Bland-Altman. A Wilcoxon test was used to compare the time for each method, at p < 0.05.

Results

Marking points on the face improved accuracy for both methods. In the inter-methods analysis with landmarks, the scanner showed excellent reliability in all measures (ICC = 0.92-0.97, p < 0.0001). Measurements accuracy with scanner was around 2 mm when the points were not previously marked and about 1 mm when the points were marked. Measures taken with the scanner, however, took twice as long, compared with the direct method.

Conclusions

Craniofacial measurements obtained with scanner showed excellent reliability and accuracy, which qualifies this method for clinical and scientific use. Accuracy is improved when the points were previously marked on face. However, the time needed to obtain measurements is greater than about 4 min for the direct method.

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.

The effect of closed septorhinoplasty on nasal functions and on external and internal nasal valves: A prospective study

BACKGROUND

Because nasal function and shape are so closely intertwined, quantitative assessments can better define their relationship and how they are affected by septorhinoplasty.

OBJECTIVE

The aim of this prospective study was to perform an analysis of the nasal airflow resistances and a three-dimensional (3D) evaluation of the soft-tissue changes after closed septorhinoplasty.

METHODS

Before surgery (T0) and 6 months after closed septorhinoplasty (T1), 30 patients underwent symptoms evaluation by means of the Italian version of the Nasal Obstruction Symptom Evaluation scale, endoscopic fiberoptic nasal examination, and visual analog scale for subjective assessment of nasal obstruction. Nasal airflow resistances were investigated with active anterior active rhinomanometry. A 3D laser scanner was used to evaluate facial soft-tissues, with specific nasal points and angles.

RESULTS

Subjective nasal obstruction decreased. Anterior active rhinomanometry demonstrated a reduction in total inspiratory and expiratory resistances between T0 and T1 but without statistical significance. The significance was still absent after decongestion, excluding turbinate hypertrophy as a cause of failed objective amelioration of nasal resistance. Facial laser scanning showed statistically significant reduction of the superior nasal width and superior alar angle, and a weak negative correlation between the superior alar angle and nasal resistances.

CONCLUSION

The absence of objective reduction of nasal airflow resistances could be the result of concurrent surgery on nasal septum and nasal valve. In particular, the ameliorating effect on nasal airflow resistances is counterbalanced by the worsening effect of the narrowing of nasal valve.

Comparison of 3D Scanning Versus 2D Photography for the Identification of Facial Soft-Tissue Landmarks

Background:

Three dimensional facial scanning is an innovation that provides opportunity for digital data acquisition, smile analysis and communication of treatment plan and outcome with patients.

Objectives:

To assess the applicability of 3D facial scanning as compared to 2D clinical photography.

Materials & Methods:

Sample consisted of thirty Caucasians aged between 25 and 50 years old, without any dentofacial deformities. Fifteen soft-tissue facial landmarks were identified twice by 3 observers on 2D and 3D images of the 30 subjects. Five linear proportions and nine angular measurements were established in the orbital, nasal and oral regions. These data were compared to anthropometric norms of young Caucasians. Furthermore, a questionnaire was completed by 14 other observers, according to their personal judgment of the 2D and 3D images.

Results:

Quantitatively, proportions linking the three facial regions in 3D were closer to the clinical standard (for 2D 3.3% and for 3D 1.8% error rate). Qualitatively, in 67% of the cases, observers were as confident about 3D as they were about 2D. Intra-observer Correlation Coefficient (ICC) revealed a better agreement between observers in 3D for the questions related to facial form, lip step and chin posture.

Conclusion:

The laser facial scanning could be a useful and reliable tool to analyze the circumoral region for orthodontic and orthognathic treatments as well as for plastic surgery planning and outcome.

Fast, accurate, small-scale 3D scene capture using a low-cost depth sensor

Commercially available depth sensing devices are primarily designed for domains that are either macroscopic, or static. We develop a solution for fast microscale 3D reconstruction, using off-the-shelf components. By the addition of lenses, precise calibration of camera internals and positioning, and development of bespoke software, we turn an infrared depth sensor designed for human-scale motion and object detection into a device with mm-level accuracy capable of recording at up to 30Hz.

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.

Unilateral mandibular hypoplasia in adult patients: distraction osteogenesis and conventional osteotomies in a standardized sequence

INTRODUCTION

This study analyzed the outcomes of nongrowing patients with unilateral mandibular hypoplasia treated according to a specific protocol, which combines distraction osteogenesis, orthodontic treatment, and conventional osteotomies.

MATERIALS AND METHODS

The patients treated were objectively evaluated. Patient's satisfaction was assessed by questionnaire. Surgical changes were analyzed using cephalometry and three-dimensional facial surface data before surgery (T0) and at long-term (T1) follow-up.

RESULTS

Four patients were included in this study. The normalization of facial proportion and a high increase in symmetry were evident. Residual defects were documented in the postoperative symmetry of the chin. In the questionnaire, all patients gave favorable responses to their facial changes; for most of the objective parameters, all patients improved.

CONCLUSIONS

A multistage treatment protocol for the correction of facial deformities in patients with unilateral mandibular hypoplasia is a valid procedure for skeletal and occlusal stability. An evident improvement of the facial appearance is also achieved.

Three-dimensional laser scanner evaluation of facial soft tissue changes after LeFort I advancement and rhinoplasty surgery: patients with cleft lip and palate vs patients with nonclefted maxillary retrognathic dysplasia (control group)

OBJECTIVE

The aim of this study was to analyze the differences in facial soft tissue changes, despite the same extent of upper jaw forward movement, between patients with unilateral cleft lip and palate (uCLP) and those without, after LeFort I osteotomy and secondary rhinoplasty.

STUDY DESIGN

Twelve patients with maxillary retrognathic dysplasia and nose deformity were divided in 2 groups, A (uCLP) and B (control), and compared on the basis of the same maxillary advancement. Cephalometry and 3D mean facial model of groups A and B were obtained before and after surgery. Linear and angular measurements were calculated.

RESULTS

Upper vermilion and alar base remained unchanged in group A but increased in group B. In both groups, symmetry of the nasal base was improved, and an increase of the sagittal projection of the lips was observed.

CONCLUSIONS

3D analysis showed that surgical procedures for uCLP can provide a satisfactory aesthetic outcome, but some differences are evident in comparison with the control group.

Three-dimensional computed tomographic analysis of changes to the external features of the nose after surgically assisted rapid maxillary expansion and orthodontic treatment: a prospective longitudinal study

INTRODUCTION

The aim of this prospective, longitudinal study was to evaluate changes to the external shape and form of the nose after surgically assisted rapid maxillary expansion and orthodontic treatment. The changes were registered using a 3-dimensional computer tomography technique, based on superimposition on the anterior base of the skull.

METHODS

The subjects comprised 35 patients (mean age, 19.7 years; range, 16.1-43.9 years). Low-dose, helical computerized tomography images were taken at treatment start and after orthodontic treatment, about 18 months postsurgery. The 3-dimensional models were registered and superimposed on the anterior cranial base.

RESULTS

There were in general significant widening and overall anterior and inferior displacement of the nasal soft tissues. The changes varied in size and direction. No correlation was found between the initial and final widths of the nose, or between the initial and final widths of the nostrils.

CONCLUSIONS

After surgically assisted rapid maxillary expansion, the most obvious changes to the external features of the nose were at the most lateral alar bases. The difference in lateral displacement profoundly influenced the perception of a more rounded nose. Patients with narrow and constrained nostrils can benefit from these changes. The 3-dimensional superimposition applied in this study is a reliable method, circumventing projection and measurement errors.

Comparison of a novel surface laser scanning anthropometric technique to traditional methods for facial parameter measurements

This study was designed to determine if three-dimensional (3D) laser scanning techniques could be used to collect accurate anthropometric measurements, compared with traditional methods. The use of an alternative 3D method would allow for quick collection of data that could be used to change the parameters used for facepiece design, improving fit and protection for a wider variety of faces. In our study, 10 facial dimensions were collected using both the traditional calipers and tape method and a Konica-Minolta Vivid9i laser scanner. Scans were combined using RapidForm XOR software to create a single complete facial geometry of the subject as a triangulated surface with an associated texture image from which to obtain measurements. A paired t-test was performed on subject means in each measurement by method. Nine subjects were used in this study: five males (one African-American and four Caucasian females) and four females displaying a range of facial dimensions. Five measurements showed significant differences (p<0.05), with most accounted for by subject movements or amended by scanning technique modifications. Laser scanning measurements showed high precision and accuracy when compared with traditional methods. Significant differences found can be very small changes in measurements and are unlikely to present a practical difference. The laser scanning technique demonstrated reliable and quick anthropometric data collection for use in future projects in redesigning respirators.

Three-dimensional facial surface analysis of patients with skeletal malocclusion

Three-dimensional (3D) laser surface scanning analysis has taken hold in orthodontics, as well as craniomaxillofacial and plastic surgery as a new tool that can navigate away from the limitations of conventional two-dimensional methods. Various techniques for 3D reconstruction of the face have been used in diagnosis, treatment planning and simulation, and outcomes follow-up. The aim of the current prospective study was to present some technical aspects for the assessment of facial changes after orthodontic and orthognathic surgery treatment using 3D laser surface scanning. The technique proposed for facial surface shape analysis represented three-dimensionally the expected surgical changes, and the reduction of the postoperative swelling was verified. This study provides technical information from the data collection to the 3D virtual soft-tissue analysis that can be useful for diagnostic information, treatment planning, future comparisons of treatment stability or facial postoperative swelling, and soft-tissue profile assessment.

Laser surface scanning analysis in reconstructive rhytidectomy

The implementation of laser surface scanning to assess facial symmetry after unilateral face-lift procedures used to reconstruct defects after skin tumor resection is presented. Six patients who had undergone defect reconstruction with a flap raised from the subcutaneous plane were included in the study. Immediate postoperative photographic evaluation confirmed facial asymmetry because of unilateral skin tension. After a minimum follow-up period of 1 year, photographic and laser surface scanning analysis showed restored facial symmetry. In conclusion, laser surface scanning is a promising technology for objectifying results obtained and could be implemented for evaluation of the immediate and long-term effects from rhytidectomy procedures. Subcutaneous flaps without duplication or resection of the superficial musculoaponeurotic system are ideal for unilateral procedures because facial symmetry is restored after 1 year.