Evaluation of Facial Anthropometry Using Three-Dimensional Photogrammetry and Direct Measuring Techniques:

Craniofacial identification standards: A review of reliability, reproducibility, and implementation

There are numerous anatomical and anthropometrical standards that can be utilised for craniofacial analysis and identification. These standards originate from a wide variety of sources, such as orthodontic, maxillofacial, surgical, anatomical, anthropological and forensic literature, and numerous media have been employed to collect data from living and deceased subjects. With the development of clinical imaging and the enhanced technology associated with this field, multiple methods of data collection have become accessible, including Computed Tomography, Cone-Beam Computed Tomography, Magnetic Resonance Imaging, Radiographs, Three-dimensional Scanning, Photogrammetry and Ultrasound, alongside the more traditional in vivo methods, such as palpation and direct measurement, and cadaveric human dissection. Practitioners often struggle to identify the most appropriate standards and research results are frequently inconsistent adding to the confusion. This paper aims to clarify how practitioners can choose optimal standards, which standards are the most reliable and when to apply these standards for craniofacial identification. This paper describes the advantages and disadvantages of each mode of data collection and collates published research to review standards across different populations for each facial feature. This paper does not aim to be a practical instruction paper; since this field encompasses a wide range of 2D and 3D approaches (e.g., clay sculpture, sketch, automated, computer-modelling), the implementation of these standards is left to the individual practitioner.

Facial Anthropometric Measurements and Principles - Overview and Implications for Aesthetic Treatments

Facial anatomy is highly individual in each patient. Anthropometric measurements can be a useful tool to objectively analyze individual facial anatomy to allow for better comparability before and after treatments to ultimately improve standardization of facial procedures, both nonsurgical and surgical. The aim of this study was to provide a comprehensive overview over clinically relevant and feasible facial anthropometric measurements and principles for aesthetic medicine. A literature review was conducted to describe the most important and clinically relevant anthropometric measurements and principles for both the entire face and for three aesthetically relevant facial regions: the periorbital region, the nose, and the perioral region. A multitude of different anthropometric measurements and principles have been described in the literature for both the overall facial appearance and specific facial regions. Certain generally accepted anthropometric principles and proportions need to be respected to achieve aesthetic and harmonious results. For the overall facial appearance, a focus on symmetry, certain proportions, facial angles, and indices has been described. Principles and measurements were also described for the periorbital region, the nose, and the perioral region. Although attractiveness and aesthetic perception are subjective, objective evaluation of facial surface anatomy via anthropometric measurements can improve pre- and postinterventional analysis of the face and help the treating physician to individualize treatments, both nonsurgical and surgical.

Intra-rater and inter-rater reliability of 3D facial measurements

Three-dimensional (3D) body scanning technology has applications for obtaining anthropometric data in human-centered and product development fields. The reliability of 3D measurements gathered from 3D scans must be assessed to understand the degree to which this technology is appropriate for use in place of manual anthropometric methods. The intra- and inter-rater reliabilities of 3D facial measurements were assessed among four novice raters using 3D landmarking. Intraclass correlation coefficient (ICC) statistics were calculated for the 3D measurement data collected in three phases to assess baseline reliabilities and improvements in reliabilities as the result of additional training and experience. Based on the results of this study, the researchers found that the collection of 3D measurement data, by multiple raters and using 3D landmarking methods, yielded a high percentage of ICC statistics in the good to excellent (>0.75 ICC) reliability range. Rater training and experience were important considerations in improving intra- and inter-rater reliabilities.

Comparison of methodologies for craniofacial soft-tissue cephalometrics: The value of virtual reality

BACKGROUND

Myriad options are available for plastic surgeons to perform soft-tissue analysis, which is vital to perioperative evaluation and research. Our objective is to compare the accuracy, precision, and efficiency of the available cephalometric modalities for conducting facial soft-tissue measurements.

METHODS

Twenty soft-tissue facial measurements were performed by 5 measurers with varying experiences on 5 adult subjects, using 6 methods-manual calipers, cone-beam CT, virtual reality (VR), 3D stereophotogrammetry, iPad-based 3D photogrammetry, and 2-dimensional photographs. Measurement sessions were timed and performed in triplicate, for a total of 9000 measurements. Intraclass correlation coefficient (ICC) was calculated for accuracy and one-way ANOVA was used for comparison. The coefficient of variation (CoV) was compared among groups to evaluate the precision of different methods by considering caliper measurements as the gold standard.

RESULTS

ICC among raters was 0.932, indicating excellent reliability. VR was significantly faster than other methods (137 s vs. 217 s for caliper, p < 0.001). CoV was the highest for 2D photographs and the lowest for VR (11.0 vs. 6.4, p < 0.001). The CoV of the caliper was similar to that of other methods, except for 2D photography, which was significantly higher. Measurements with the greatest absolute difference from caliper measurements, across modalities, were those around the eyes (left to right exocanthion), tragion to antitragion, and tragion to exocanthion.

CONCLUSION

2D photography is not an accurate method for cephalometric measurements. VR had the lowest variation between measurements, and was the fastest and equivalent to caliper measurements in accuracy. For studies involving a large number of cephalometrics, VR measurements may be a good option to improve study throughput.

"Utility of Smartphone-based Three-dimensional Surface Imaging for Digital Facial Anthropometry"

Background

The utilization of three-dimensional (3D) surface imaging for facial anthropometry is a significant asset for patients undergoing maxillofacial surgery. Notably, there have been recent advancements in smartphone technology that enable 3D surface imaging.In this study, anthropometric assessments of the face were performed using a smartphone and a sophisticated 3D surface imaging system.

Methods

30 healthy volunteers (15 females and 15 males) were included in the study. An iPhone 14 Pro (Apple Inc., USA) using the application 3D Scanner App (Laan Consulting Corp., USA) and the Vectra M5 (Canfield Scientific, USA) were employed to create 3D surface models. For each participant, 19 anthropometric measurements were conducted on the 3D surface models. Subsequently, the anthropometric measurements generated by the two approaches were compared. The statistical techniques employed included the paired t-test, paired Wilcoxon signed-rank test, Bland-Altman analysis, and calculation of the intraclass correlation coefficient (ICC).

Results

All measurements showed excellent agreement between smartphone-based and Vectra M5-based measurements (ICC between 0.85 and 0.97). Statistical analysis revealed no statistically significant differences in the central tendencies for 17 of the 19 linear measurements. Despite the excellent agreement found, Bland-Altman analysis revealed that the 95% limits of agreement between the two methods exceeded ±3 mm for the majority of measurements.

Conclusion

Digital facial anthropometry using smartphones can serve as a valuable supplementary tool for surgeons, enhancing their communication with patients. However, the proposed data suggest that digital facial anthropometry using smartphones may not yet be suitable for certain diagnostic purposes that require high accuracy.

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.

Age-related changes of the periocular morphology: a two- and three-dimensional anthropometry study in Caucasians

PURPOSE

To determine age-and sex-related changes in periocular morphology in Caucasians using a standardized protocol.

METHODS

Healthy Caucasian volunteers aged 18-35 and 60-90 years old were recruited from the Department of Ophthalmology, Faculty of Medicine and University Hospital, Cologne, between October 2018 and May 2020. Volunteers with facial asymmetry, facial deformities, history of facial trauma, facial surgery, botox injection, eyelid ptosis, strabismus, or nystagmus, were excluded. Standardized three-dimensional facial photos of 68 young volunteers and 73 old volunteers were taken in this clinical practice. Position changes of endocanthion, pupil center, and exocanthion were analyzed in different age and gender groups, including palpebral fissure width (PFW): distance between endocanthions (En-En), pupil centers (Pu-Pu), exocanthions (Ex-Ex), endocanthion and nasion (En-Na), pupil center and nasion (Pu-Na), exocanthion and nasion (Ex-Na), endocanthion and pupil center (Pu-En), exocanthion and pupil center (Pu-Ex), and palpebral fissure inclination (PFI); angle of endocanthions to nasion (En-Na-En), pupils to nasion (Pu-Na-Pu), exocanthions to nasion (Ex-Na-Ex); endocanthion inclination (EnI), and exocanthion inclination (ExI).

RESULTS

PFW, En-En, Ex-Na, Pu-Ex, PFI, ExI, and Ex-Na-Ex were significantly different between the young and old groups (p ≤ 0.004). There were sex-related differences in PFW, Ex-Ex, En-Na, Pu-Na, Ex-Na, Pu-En, PFI, and EnI between both groups (p ≤ 0.041).

CONCLUSION

The position change of the pupil is minimal relative to age; it is preferred to establish the reference plane to describe periocular changes. The endocanthion tends to move temporally and inferiorly, while the exocanthion tends to shift nasally and inferiorly with age.

Cloner 3D photogrammetric facial scanner: Assessment of accuracy in a controlled clinical study

OBJECTIVE

To evaluate the accuracy of facial measurements on three-dimensional images obtained using a new photogrammetric scanner.

MATERIAL AND METHODS

A total of 11 participants were included in the study. Nine customized adhesive labels were used to identify the facial landmarks: Trichion (Tri), Glabella (G), Right (Exr) and Left (Exl), Pronasal (Pn), Subnasal (Sn), Chelion right (Chr) and left (Chl) and Mentonian (Me). Two trained and calibrated examiners were responsible for performing seven linear measurements for each participant (Tri-G, Sn-Me, Exr-Exl, Chr-Chl, Exr-Chr, Exl-Chl, Pn-Sn) first with a digital caliper and later with a three-dimensional model obtained after digitalization with photogrammetric technology. The intraclass correlation coefficient (ICC), mean difference, SD, and Bland-Altman correlation were used to compare the measurements performed.

RESULTS

Intra and inter-examiner reliability were excellent (ICC >0.9). In general, the measurements presented a variation of a minor 2.0 mm. However, only three measures (Sn-Me, Exr-Exl, and Exr-Chr) were outside the clinical acceptability range.

CONCLUSIONS

The 3D Cloner scanner showed clinically acceptable accuracy comparable to the digital caliper with a variation of -0.8 ± 1.2 mm. Inter- and intra-examiner agreement on digital measurements was also observed.

CLINICAL SIGNIFICANCE

Scanners with accurate 3D model reproductions associated with reliable digital measurements provide a more precise diagnosis and better planning in orofacial treatment.

Accuracy of three-dimensional optical devices for facial soft-tissue measurement in clinical practice of stomatology: A PRISMA systematic review

BACKGROUND

The accuracy of 3-dimensional (3D) optical devices for facial soft-tissue measurement is essential to the success of clinical treatment in stomatology. The aim of the present systematic review was to summarize the accuracy of 3D optical devices used for facial soft-tissue assessment in stomatology.

METHODS

An extensive systematic literature search was performed in the PubMed/MEDLINE, Embase, Scopus and Cochrane Library databases for studies published in the English language up to May 2022 in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Peer-reviewed journal articles evaluating the facial soft-tissue morphology by 3D optical devices were included. The risk of bias was performed using the Quality Assessment Tool for Diagnostic Accuracy Studies-2 guidelines by the 2 reviewers. The potential publication bias was analyzed using the Review Manager software.

RESULTS

The query returned 1853 results. A total of 38 studies were included in this review. Articles were categorized based on the principle of devices: laser-based scanning, structured-light scanning, stereophotogrammetry and red, green, blue-depth camera.

CONCLUSION

Overall, the 3D optical devices demonstrated excellent accuracy and reliability for facial soft-tissue measurement in stomatology. red, green, blue-depth camera can collect accurate static and dynamic 3D facial scans with low cost and high measurement accuracy. Practical needs and availability of resources should be considered when these devices are used in clinical settings.

Anthropometric Landmarking for Diagnosis of Cranial Deformities: Validation of an Automatic Approach and Comparison with Intra- and Interobserver Variability

Shape analysis of infant's heads is crucial to diagnose cranial deformities and evaluate head growth. Currently available 3D imaging systems can be used to create 3D head models, promoting the clinical practice for head evaluation. However, manual analysis of 3D shapes is difficult and operator-dependent, causing inaccuracies in the analysis. This study aims to validate an automatic landmark detection method for head shape analysis. The detection results were compared with manual analysis in three levels: (1) distance error of landmarks; (2) accuracy of standard cranial measurements, namely cephalic ratio (CR), cranial vault asymmetry index (CVAI), and overall symmetry ratio (OSR); and (3) accuracy of the final diagnosis of cranial deformities. For each level, the intra- and interobserver variability was also studied by comparing manual landmark settings. High landmark detection accuracy was achieved by the method in 166 head models. A very strong agreement with manual analysis for the cranial measurements was also obtained, with intraclass correlation coefficients of 0.997, 0.961, and 0.771 for the CR, CVAI, and OSR. 91% agreement with manual analysis was achieved in the diagnosis of cranial deformities. Considering its high accuracy and reliability in different evaluation levels, the method showed to be feasible for use in clinical practice for head shape analysis.

Reliability of Stereophotogrammetry for Area Measurement in the Periocular Region

Three-dimensional (3D) stereophotography area measurements are essential for describing morphology in the periocular region. However, its reliability has not yet been sufficiently validated. The objective of this study was to evaluate the reliability of 3D stereophotogrammetric area measurements in the periocular region. Forty healthy volunteers had five flat paper objects placed at each of the seven periocular positions including the endocanthion and the upper medial, upper middle, upper lateral, lower medial, lower middle, and the lower lateral eyelid. Two series of photographic images were captured twice by the same investigator. Each image of the first series was measured twice by the same rater, while images of both series were measured once by a second rater. Differences between these measurements were calculated, and the intrarater, interrater, and intramethod reliability was evaluated for intraclass correlation coefficients (ICCs), mean absolute differences (MADs), technical errors of measurements (TEMs), relative errors of measurements (REMs), and relative TEM (rTEM). Our results showed that 21.2% of all ICCs were considered as excellent, 45.5% were good, 27.3% were moderate, and 6.1% were poor. The interrater ICC for the endocanthion location was 0.4% on a low level. MAD values for all objects were less than 0.3 mm², all TEM were less than 1 mm², the REM and rTEM were less than 2% for all objects, showing high reliability. 3D stereophotogrammetry is a highly reliable system for periocular area measurements and may be used in the clinical routine for planning oculoplastic surgeries and for evaluating changes in periocular morphology.

Level of Evidence IV This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Integration of digital maxillary dental casts with 3D facial images in orthodontic patients

OBJECTIVE

To evaluate three-dimensional (3D) accuracy and reliability of nonradiographic dentofacial images integrated with a two-step method.

METHODS

3D facial images, cone-beam computed tomography (CBCT) images and digital maxillary dental casts were obtained from 20 pre-orthodontic subjects. Digital dental casts were integrated into 3D facial images using a two-step method based on the anterior tooth area. 3D coordinate values of five dental landmarks were identified in both dentofacial images and CBCT images. The accuracy of the integration method was assessed with paired t-tests between dentofacial images and CBCT-based reference standards. Intraclass correlation coefficients (ICCs) were assessed for the reliability of dentofacial images and CBCT-based images. Analysis of variance and Kruskal-Wallis tests evaluated the accuracy of the method in different dimensions.

RESULTS

There was no statistical difference between dentofacial images and CBCT reference standards in both translational and rotational dimensions (P > .05). Translational mean absolute errors for full dentitions were within 0.42 mm and ICCs were over 0.998 in x, y, and z directions. Rotational mean absolute errors for full dentitions were within 0.92° and ICCs over 0.734 in pitch, yaw, and roll orientations. Integration errors were significantly greater in the first molar, z-translation, and pitch rotation (P < .05).

CONCLUSIONS

Integrating 3D dentofacial images with the two-step method is precise and acceptable for clinical diagnostics and scientific purposes. Errors were greater in the molar region, z-translation, and pitch rotation.

Reliability of optical devices for three-dimensional facial anatomy description: a systematic review and meta-analysis

The use of three-dimensional (3D) optical instruments to measure soft tissue facial characteristics is increasing, but systematic assessments of their reliability, practical use in research and clinics, outcome measurements, and advantages and limitations are not fully established. Therefore, a review of the current literature was performed on the reliability of facial anthropometric measurements obtained by 3D optical facial reproductions as compared to conventional anthropometry or other optical devices. The systematic literature search was conducted in electronic databases following the PRISMA guidelines (PROSPERO registration: CRD42018085473). Overall, 815 studies were identified, with 27 final papers included. Two meta-analyses were conducted. Tested devices included conventional cameras, laser scanning, stereophotogrammetry, and structured light. Studies measured living people or inanimate objects. Overall, the optical devices were considered reliable for the measurement of linear distances. Some caution is needed for surface assessments. All instruments are suitable for the analysis of inanimate objects, but fast scan devices should be preferred for living subjects to avoid motion artefacts in the orbital and nasolabial areas. Prior facial landmarking is suggested to improve measurement accuracy. Practical needs and economic means should direct the choice of the most appropriate instrument. Considering the increasing interest in surface-to-surface measurements, fast scan devices should be preferred, and dedicated protocols devised.