Technical validation of the Di3D stereophotogrammetry surface imaging system

Facial modeling and measurement based upon homologous topographical features

Measurement of human faces is fundamental to many applications from recognition to genetic phenotyping. While anthropometric landmarks provide a conventional set of homologous measurement points, digital scans are increasingly used for facial measurement, despite the difficulties in establishing their homology. We introduce an alternative basis for facial measurement, which 1) provides a richer information density than discrete point measurements, 2) derives its homology from shared facial topography (ridges, folds, etc.), and 3) quantifies local morphological variation following the conventions and practices of anatomical description. A parametric model that permits matching a broad range of facial variation by the adjustment of 71 parameters is demonstrated by modeling a sample of 80 adult human faces. The surface of the parametric model can be adjusted to match each photogrammetric surface mesh generally to within 1 mm, demonstrating a novel and efficient means for facial shape encoding. We examine how well this scheme quantifies facial shape and variation with respect to geographic ancestry and sex. We compare this analysis with a more conventional, landmark-based geometric morphometric (GMM) study with 43 landmarks placed on the same set of scans. Our multivariate statistical analysis using the 71 attribute values separates geographic ancestry groups and sexes with a high degree of reliability, and these results are broadly similar to those from GMM, but with some key differences that we discuss. This approach is compared with conventional, non-parametric methods for the quantification of facial shape, including generality, information density, and the separation of size and shape. Potential uses for phenotypic and dysmorphology studies are also discussed.

Frontiers in Three-Dimensional Surface Imaging Systems for 3D Face Acquisition in Craniofacial Research and Practice: An Updated Literature Review

Digitalizing all aspects of dental care is a contemporary approach to ensuring the best possible clinical outcomes. Ongoing advancements in 3D face acquisition have been driven by continuous research on craniofacial structures and treatment effects. An array of 3D surface-imaging systems are currently available for generating photorealistic 3D facial images. However, choosing a purpose-specific system is challenging for clinicians due to variations in accuracy, reliability, resolution, and portability. Therefore, this review aims to provide clinicians and researchers with an overview of currently used or potential 3D surface imaging technologies and systems for 3D face acquisition in craniofacial research and daily practice. Through a comprehensive literature search, 71 articles meeting the inclusion criteria were included in the qualitative analysis, investigating the hardware, software, and operational aspects of these systems. The review offers updated information on 3D surface imaging technologies and systems to guide clinicians in selecting an optimal 3D face acquisition system. While some of these systems have already been implemented in clinical settings, others hold promise. Furthermore, driven by technological advances, novel devices will become cost-effective and portable, and will also enable accurate quantitative assessments, rapid treatment simulations, and improved outcomes.

Can smartphones be used for routine dental clinical application? A validation study for using smartphone-generated 3D facial images

OBJECTIVES

To compare the accuracy of smartphone-generated three-dimensional (3D) facial images to that of direct anthropometry (DA) and 3dMD with the aim of assessing the validity and reliability of smartphone-generated 3D facial images for routine clinical applications.

MATERIALS AND METHODS

Twenty-five anthropometric soft-tissue facial landmarks were labelled manually on 22 orthognathic surgery patients (11 males and 11 females; mean age 26.2 ± 5.3 years). For each labelled face, two imaging operations were performed using two different surface imaging systems: 3dMDface and Bellus3D FaceApp. Next, 42 inter-landmark facial measurements amongst the identified facial landmarks were measured directly on each labelled face and also digitally on 3D facial images. The measurements obtained from smartphone-generated 3D facial images (SGI) were statistically compared with those from DA and 3dMD.

RESULTS

SGI had slightly higher measurement values than DA and 3dMD, but there was no statistically significant difference between the mean values of inter-landmark measures across the three methods. Clinically acceptable differences (≤3 mm or ≤5°) were observed for 67 % and 74 % of measurements with good agreement between DA and SGI, and 3dMD and SGI, respectively. An overall small systematic bias of ± 0.2 mm was observed between the three methods. Furthermore, the mean absolute difference between DA and SGI methods was highest for linear (1.41 ± 0.33 mm) as well as angular measurements (3.07 ± 0.73°).

CONCLUSIONS

SGI demonstrated fair trueness compared to DA and 3dMD. The central region and flat areas of the face in SGI are more accurate. Despite this, SGI have limited clinical application, and the panfacial accuracy of the SGI would be more desirable from a clinical application standpoint.

CLINICAL SIGNIFICANCE

The usage of SGI in clinical practice for region-specific macro-proportional facial assessment involving central and flat regions of the face or for patient education purposes, which does not require accuracy within 3 mm and 5° can be considered.

Accuracy (trueness and precision) of four tablet-based applications for three-dimensional facial scanning: an in-vitro study.: Tablet-based applications for 3D facial scanning

OBJECTIVES

This study aimed to investigate the overall and regional accuracy (trueness and precision) of digital three-dimensional (3D) facial scans obtained from four tablet-based applications, which were (Bellus) the Bellus Dental Pro® (Bellus3D, Inc. Campbell, CA, USA), (Capture) the Capture®: 3D Scan Anything (Standard Cyborg, Inc. San Francisco, CA, USA), (Heges) the Heges® (by Marek Simonik, Ostrava, North Moravia, Czech Republic), and (Scandy) the Scandy Pro 3D Scanner® (Scandy LLC, New Orleans, LA, USA).

METHODS

A mannequin's face was marked with 63 landmarks. Subsequently, it was scanned 5 times using each scan application on an iPad Pro® (Apple Inc., Cupertino, CA, USA). The digital measurements were obtained with MeshLab® (CNR-ISTI, Pisa, Tuscany, Italy) and compared to the manual measurements using a digital vernier caliper (Truper Herramientas S.A., Colonia Granada, Mexico City, Mexico). The absolute mean difference and the standard deviation of the dimensional discrepancies were calculated. Moreover, the data were analysed by using one-way ANOVA, Levene's test, and Bonferroni´s correction.

RESULTS

The absolute mean trueness values were Bellus 0.41 ± 0.35 mm, Capture 0.38 ± 0.37 mm, Heges 0.39 ± 0.38 mm, and Scandy 0.47 ± 0.44 mm. Moreover, precision values were Bellus 0.46 mm, Capture 0.46 mm, Heges 0.54 mm, and Scandy 0.64 mm. Comparing the regions, Capture and Scandy showed the highest absolute mean difference, which was 0.81 mm in the Frontal and Zygomaticofacial regions, respectively.

CONCLUSIONS

The trueness and precision of all four tablet-based applications were clinically acceptable for diagnosis and treatment planning.

CLINICAL SIGNIFICANCE

The future of the three-dimensional facial scan is auspicious, and it has the potential to be affordable, accurate, and of great value for clinicians in their daily practice.

Present and future of extraoral maxillofacial prosthodontics: Cancer rehabilitation

Historically, facial prosthetics have successfully rehabilitated individuals with acquired or congenital anatomical deficiencies of the face. This history includes extensive efforts in research and development to explore best practices in materials, methods, and artisanal techniques. Presently, extraoral maxillofacial rehabilitation is managed by a multiprofessional team that has evolved with a broadened scope of knowledge, skills, and responsibility. This includes the mandatory integration of different professional specialists to cover the bio-psycho-social needs of the patient, systemic health and pathology surveillance, and advanced restorative techniques, which may include 3D technologies. In addition, recent digital workflows allow us to optimize this multidisciplinary integration and reduce the active time of both patients and clinicians, as well as improve the cost-efficiency of the care system, promoting its access to both patients and health systems. This paper discusses factors that affect extraoral maxillofacial rehabilitation's present and future opportunities from teamwork consolidation, techniques utilizing technology, and health systems opportunities.

Facial Scanning Accuracy with Stereophotogrammetry and Smartphone Technology in Children: A Systematic Review

The aim of the study was to systematically review and compare the accuracy of smartphone scanners versus stereophotogrammetry technology for facial digitization in children. A systematic literature search strategy of articles published from 1 January 2010 to 30 August 2022 was adopted through a combination of Mesh terms and free text words pooled through boolean operators on the following databases: PubMed, Scopus, Web of Science, Cochrane Library, LILACS, and OpenGrey. Twenty-three articles met the inclusion criteria. Stationary stereophotogrammetry devices showed a mean accuracy that ranged from 0.087 to 0.860 mm, portable stereophotogrammetry scanners from 0.150 to 0.849 mm, and smartphones from 0.460 to 1.400 mm. Regarding the risk of bias assessment, fourteen papers showed an overall low risk, three articles had unclear risk and four articles had high risk. Although smartphones showed less performance on deep and irregular surfaces, all the analyzed devices were sufficiently accurate for clinical application. Internal depth-sensing cameras or external infrared structured-light depth-sensing cameras plugged into smartphones/tablets increased the accuracy. These devices are portable and inexpensive but require greater operator experience and patient compliance for the incremented time of acquisition. Stationary stereophotogrammetry is the gold standard for greater accuracy and shorter acquisition time, avoiding motion artifacts.

Accuracy and Reliability of Kinect Motion Sensing Input Device’s 3D Models: A Comparison to Direct Anthropometry and 2D Photogrammetry

AIM: This study aims to evaluate the accuracy and reliability of Kinect motion sensing input device’s three-dimensional (3D) models by comparing it with direct anthropometry and digital 2D photogrammetry. MATERIALS AND METHODS: Six profiles and four frontal parameters were directly measured on the faces of 80 participants. The same measurements were repeated using two-dimensional (2D) photogrammetry and (3D) images obtained from Kinect device. Another observer made the same measurements for 30% of the images obtained with 3D technique, and interobserver reproducibility was evaluated for 3D images. Intraobserver reproducibility was evaluated. Statistical analysis was conducted using the paired samples t-test, interclass correlation coefficient, and Bland-Altman limits of agreement. RESULTS: The highest mean difference was 0.0084 mm between direct measurement and photogrammetry, 0.027 mm between direct measurement and 3D Kinect’s models, and 0.018 mm between photogrammetry and 3D Kinect’s. The lowest agreement value was 0.016 in the all parameter between the photogrammetry and 3D Kinect’s methods. Agreement between the two observers varied from 0.999 Sn-Me to 1 with the rest of linear measurements. CONCLUSION: Measurements done using 3D Images obtained from Kinect device indicate that it may be an accurate and reliable imaging method for use in orthodontics. It also provides an easy low-cost 3D imaging technique that has become increasingly popular in clinical settings, offering advantages for surgical planning and outcome evaluation.

A novel approach quantifying the periorbital morphology: A comparison of direct, 2-dimensional, and 3-dimensional technologies

BACKGROUND

The measurement of anatomical structures is critical in plastic and reconstructive surgery. However, few detailed and standardized measurements have been widely used in the periorbital region. This study aimed to evaluate the feasibility of a novel detailed and standardized protocol with 2D and 3D technologies, and explore the relationship between them and direct measurements.

METHODS

Fifty healthy Caucasians (100 eyes) between 20 and 68 years old were recruited and captured for 3D photographs by VECTRA M3 3D Imaging System. Subsequently, 24 landmarks were located on each 3D photographs following a standardized protocol, and then 19 linear and 3 angular periorbital variables were measured. Furthermore, two-dimensional (2D) and direct measurements were conducted on each subject and compared with 3D measurements and one another.

RESULTS

The grand r means across all measurements were 0.77, 0.78, and 0.88 for direct vs. 2D values, direct vs. 3D values, and 3D vs. 2D values, respectively. The mean absolute differences were 1 mm (ranging from 0.2 mm to 3.7 mm) between direct and 3D measurements, 1 mm (ranging from 0.04 mm to 2.4 mm) between direct and 2D measurements, and 1 mm and 6.6° (ranging from 0.04 mm or 0.5° to 3 mm or 12.8°) between 2D and 3D measurements.

CONCLUSIONS

This study verified the feasibility of this detailed and standardized landmark localization protocol for assessing the periorbital morphology with 2D and 3D technologies. This protocol may work as a bridge communicating with all studies involving any of the three technologies in the future.

Three-dimensional facial capture using a custom-built photogrammetry setup: Design, performance, and cost

INTRODUCTION

Although stereophotogrammetry is increasingly popular for 3-dimensional face scanning, commercial solutions remain quite expensive, limiting its accessibility. We propose a more affordable, custom-built photogrammetry setup (Stereo-Face 3D, SF3D) and evaluate its variability within and between systems.

METHODS

Twenty-nine subjects and a mannequin head were imaged 3 times using SF3D and a commercially available system. An anthropometric mask was mapped viscoelastically onto the reconstructed meshes using MeshMonk (https://github.com/TheWebMonks/meshmonk). Within systems, shape variability was determined by calculating the root-mean-square error (RMSE) of the Procrustes distance between each of the subject's 3 scans and the subject's ground truth (calculated by averaging the mappings after a nonscaled generalized Procrustes superimposition). Intersystem variability was determined by similarly comparing the ground truth mappings of both systems. Two-factor Procrustes analysis of variance was used to partition the intersystem shape variability to understand the source of the discrepancies between the facial shapes acquired by both systems.

RESULTS

The RMSEs of the within-system shape variability for 3dMDFace and SF3D were 0.52 ± 0.07 mm and 0.44 ± 0.16 mm, respectively. The corresponding values for the mannequin head were 0.42 ± 0.02 mm and 0.29 ± 0.03 mm, respectively. The between-systems RMSE was 1.6 ± 0.34 mm for the study group and 1.38 mm for the mannequin head. A 2-factor analysis indicated that variability attributable to the system was expressed mainly at the upper eyelids, nasal tip and alae, and chin areas.

CONCLUSIONS

The variability values of the custom-built setup presented here were competitive to a state-of-the-art commercial system at a more affordable level of investment.

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.

Validity and reproducibility of the 3D VECTRA photogrammetric surface imaging system for the maxillofacial anthropometric measurement on cleft patients

OBJECTIVES

To validate the accuracy and reproducibility of linear measurements of three-dimensional (3D) images and to compare the measurements with the direct anthropometry method on cleft lip and palate (CLP) patients.

MATERIALS AND METHODS

Nineteen linear facial measurements were derived from 16 standardized surface landmarks obtained from 37 cleft patients (20 males, 17 females; mean age 23.84 years, standard deviation ± 6.02). They were taken manually with calipers and were compared with the digitally calculated distance on the 3D images captured using the VECTRA-M5 360° Imaging System with pre-marked landmarks. Another pair of 19 linear measurements were computed on the 3D images 2 weeks apart for intra- and inter-observer agreements. Statistical analyses used were paired t test, the Bland-Altman analysis, and the intra-class correlation coefficient (ICC) index.

RESULTS

Most of the linear measurements showed no statistically significant differences between the proposed method and direct anthropometry linear measurements. Nevertheless, bias of the 3D imaging system is present in the linear measurements of the nose width and the upper vermillion height. The measurements' mean biases were within 2 mm, but the 95% limit of agreement was more than 2 mm. Intra- and inter-observer measurements generally showed good reproducibility. Four inter-observer measurements, the upper and lower face heights, nose width, and pronasale to left alar base were clinically significant.

CONCLUSIONS

Measurements obtained from this 3D imaging system are valid and reproducible for evaluating CLP patients.

CLINICAL RELEVANCE

The system is suitable to be used in a clinical setting for cleft patients. However, training of the operator is strictly advisable.

Reliability of periocular anthropometry using three-dimensional digital stereophotogrammetry

PURPOSE

Non-invasive three-dimensional (3D) stereophotogrammetry is becoming increasingly popular in many fields. However, few studies have focused on its periocular application. We aimed to provide evidence for the periocular application of a novel anthropometric procedure using 3D stereophotogrammetry by evaluating its reliability.

METHODS

Fifty-one Caucasians were recruited (102 eyes; mean age, 31.9 ± 13.6 years). Two sets of 3D images were acquired for each subject, and two measurement sessions were performed on each image by two raters. Fifty-two periocular landmarks were identified, and then 49 corresponding linear, curvilinear, and angular measurements were evaluated for intrarater, interrater, and intramethod reliability.

RESULTS

Our findings showed highly reliable results for mean absolute difference (0.59 and 0.68 unit), relative error measurement (2.66% and 3.08%), technical error of measurement (0.59 and 0.66 unit), relative technical error of measurement (2.71% and 2.96%), and intraclass correlation coefficient (0.98) for intrarater 1 and intrarater 2 reliability; respectively 0.94 unit, 4.06%, 0.89 unit, and 3.94%, as well as 0.97 for interrater reliability; and respectively 0.98 unit, 4.66%, 0.96 unit, and 4.64%, as well as 0.96 for intramethod reliability.

CONCLUSIONS

This imaging system and the landmark identification protocol are highly reliable. The collected measurements and their errors can be applied for the comparison of reliability among various 3D imaging systems and populations. It could be utilized for planning surgeries and evaluating treatment outcomes for physicians in ophthalmology, plastic and esthetic surgery, and in the maxillofacial field where periocular morphology alterations are made.

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.

Soft tissue changes: a comparison between changes caused by the construction bite and by successful treatment with a modified Twin-block appliance

Background/objectives

Functional appliances are commonly used to correct Class II malocclusion. This study aimed to compare the facial soft tissue changes in Caucasians between pre-treatment and with the construction bite versus pre-treatment and completion of treatment with a modified Twin-block appliance (MTBA).

Materials and methods

Fifty-eight Caucasian subjects with Class II division 1 malocclusion had 3D stereophotogrammetric images captured pre-treatment (T1), with the construction bite (T2), and on completion of MTBA treatment (T3). Twenty-six landmarks were located on each image and 10% were re-landmarked 1 month later. Soft-tissue linear and volumetric changes (T1-T2 and T1-T3) were analyzed using linear mixed effect models (SAS® Version 9.4, www.sas.com).

Results

Forty-seven subjects [mean age 13.2 (SD 1.7) years] completed treatment [mean duration 9.8 (SD 3.8) months]. Differences between the changes from T1 to T2 versus T1 to T3 for upper facial and upper lip landmarks were insignificant (all P > 0.05) except for nasion, orbitale right, pronasale, and subnasale. For the same comparisons, lower lip and chin landmarks changed significantly (all P < 0.05) as did facial soft tissue volume (P< 0.0001).

Limitations

There was no control group.

Conclusion

The facial soft tissue changes from pre-treatment to with the construction bite were considerably more than those from pre-treatment to completion of treatment with a MTBA.

Implication

With MTBA treatment, the soft tissue changes from pre-treatment to with the construction bite in situ, overestimate those from pre- to post-treatment.

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.

An overview of the latest developments in facial imaging

Facial imaging is a term used to describe methods that use facial images to assist or facilitate human identification. This pertains to two craniofacial identification procedures that use skulls and faces-facial approximation and photographic superimposition-as well as face-only methods for age progression/regression, the construction of facial graphics from eyewitness memory (including composites and artistic sketches), facial depiction, face mapping and newly emerging methods of molecular photofitting. Given the breadth of these facial imaging techniques, it is not surprising that a broad array of subject-matter experts participate in and/or contribute to the formulation and implementation of these methods (including forensic odontologists, forensic artists, police officers, electrical engineers, anatomists, geneticists, medical image specialists, psychologists, computer graphic programmers and software developers). As they are concerned with the physical characteristics of humans, each of these facial imaging areas also falls in the domain of physical anthropology, although not all of them have been traditionally regarded as such. This too offers useful opportunities to adapt established methods in one domain to others more traditionally held to be disciplines within physical anthropology (e.g. facial approximation, craniofacial superimposition and face photo-comparison). It is important to note that most facial imaging methods are not currently used for identification but serve to assist authorities in narrowing or directing investigations such that other, more potent, methods of identification can be used (e.g. DNA). Few, if any, facial imaging approaches can be considered honed end-stage scientific methods, with major opportunities for physical anthropologists to make meaningful contributions. Some facial imaging methods have considerably stronger scientific underpinnings than others (e.g. facial approximation versus face mapping), some currently lie entirely within the artistic sphere (facial depiction), and yet others are so aspirational that realistic capacity to obtain their aims has strongly been questioned despite highly advanced technical approaches (molecular photofitting). All this makes for a broad-ranging, dynamic and energetic field that is in a constant state of flux. This manuscript provides a theoretical snapshot of the purposes of these methods, the state of science as it pertains to them, and their latest research developments.

A novel approach for intra-operative shape acquisition of the tibio-femoral joints using 3D laser scanning in computer assisted orthopaedic surgery

BACKGROUND

Image registration (IR) is an important process of developing a spatial relationship between pre-operative data and the physical patient in the operation theatre. Current IR techniques for Computer Assisted Orthopaedic Surgery (CAOS) are time consuming and costly. There is a need to automate and accelerate this process.

METHODS

Bespoke quick, cost effective, contactless and automated 3D laser scanning techniques based on the DAVID Laserscanner method were designed. 10 cadaveric knee joints were intra-operatively laser scanned and were registered with the pre-operative MRI scans. The results are supported with a concurrent validity study.

RESULTS

The average absolute errors between scan models were systematically less than 1 mm. Errors on femoral surfaces were higher than tibial surfaces (P<0.05). Additionally, scans acquired through the large exposure produced higher errors than the smaller exposure (P<0.05).

CONCLUSION

This study has provided proof of concept for a novel automated shape acquisition and registration technique for CAOS.

Validation of the Vectra H1 portable three-dimensional photogrammetry system for facial imaging

Three-dimensional (3D) surface imaging using stereophotogrammetry has become increasingly popular in clinical settings, offering advantages for surgical planning and outcome evaluation. The handheld Vectra H1 is a low-cost, highly portable system that offers several advantages over larger stationary cameras, but independent technical validation is currently lacking. In this study, 3D facial images of 26 adult participants were captured with the Vectra H1 system and the previously validated 3dMDface system. Using error magnitude statistics, 136 linear distances were compared between cameras. In addition, 3D facial surfaces from each system were registered, heat maps generated, and global root mean square (RMS) error calculated. The 136 distances were highly comparable across the two cameras, with an average technical error of measurement (TEM) value of 0.84mm (range 0.19-1.54mm). The average RMS value of the 26 surface-to-surface comparisons was 0.43mm (range 0.33-0.59mm). In each case, the vast majority of the facial surface differences were within a ±1mm threshold. Areas exceeding ±1mm were generally limited to facial regions containing hair or subject to facial microexpressions. These results indicate that 3D facial surface images acquired with the Vectra H1 system are sufficiently accurate for most clinical applications.

Monoscopic photogrammetry to obtain 3D models by a mobile device: a method for making facial prostheses

Purpose

The aim of this study is to present the development of a new technique to obtain 3D models using photogrammetry by a mobile device and free software, as a method for making digital facial impressions of patients with maxillofacial defects for the final purpose of 3D printing of facial prostheses.

Methods

With the use of a mobile device, free software and a photo capture protocol, 2D captures of the anatomy of a patient with a facial defect were transformed into a 3D model. The resultant digital models were evaluated for visual and technical integrity. The technical process and resultant models were described and analyzed for technical and clinical usability.

Results

Generating 3D models to make digital face impressions was possible by the use of photogrammetry with photos taken by a mobile device. The facial anatomy of the patient was reproduced by a *.3dp and a *.stl file with no major irregularities. 3D printing was possible.

Conclusions

An alternative method for capturing facial anatomy is possible using a mobile device for the purpose of obtaining and designing 3D models for facial rehabilitation. Further studies must be realized to compare 3D modeling among different techniques and systems.

Clinical implication

Free software and low cost equipment could be a feasible solution to obtain 3D models for making digital face impressions for maxillofacial prostheses, improving access for clinical centers that do not have high cost technology considered as a prior acquisition.

Breast volumetric analysis for aesthetic planning in breast reconstruction: a literature review of techniques

BACKGROUND

Accurate volumetric analysis is an essential component of preoperative planning in both reconstructive and aesthetic breast procedures towards achieving symmetrization and patient-satisfactory outcome. Numerous comparative studies and reviews of individual techniques have been reported. However, a unifying review of all techniques comparing their accuracy, reliability, and practicality has been lacking.

METHODS

A review of the published English literature dating from 1950 to 2015 using databases, such as PubMed, Medline, Web of Science, and EMBASE, was undertaken.

RESULTS

Since Bouman's first description of water displacement method, a range of volumetric assessment techniques have been described: thermoplastic casting, direct anthropomorphic measurement, two-dimensional (2D) imaging, and computed tomography (CT)/magnetic resonance imaging (MRI) scans. However, most have been unreliable, difficult to execute and demonstrate limited practicability. Introduction of 3D surface imaging has revolutionized the field due to its ease of use, fast speed, accuracy, and reliability. However, its widespread use has been limited by its high cost and lack of high level of evidence. Recent developments have unveiled the first web-based 3D surface imaging program, 4D imaging, and 3D printing.

CONCLUSIONS

Despite its importance, an accurate, reliable, and simple breast volumetric analysis tool has been elusive until the introduction of 3D surface imaging technology. However, its high cost has limited its wide usage. Novel adjunct technologies, such as web-based 3D surface imaging program, 4D imaging, and 3D printing, appear promising.

Accuracy and reliability of 3D stereophotogrammetry: A comparison to direct anthropometry and 2D photogrammetry

OBJECTIVE

To evaluate the accuracy of three-dimensional (3D) stereophotogrammetry by comparing it with the direct anthropometry and digital photogrammetry methods. The reliability of 3D stereophotogrammetry was also examined.

MATERIALS AND METHODS

Six profile and four frontal parameters were directly measured on the faces of 80 participants. The same measurements were repeated using two-dimensional (2D) photogrammetry and 3D stereophotogrammetry (3dMDflex System, 3dMD, Atlanta, Ga) to obtain images of the subjects. Another observer made the same measurements for images obtained with 3D stereophotogrammetry, and interobserver reproducibility was evaluated for 3D images. Both observers remeasured the 3D images 1 month later, and intraobserver reproducibility was evaluated. Statistical analysis was conducted using the paired samples t-test, intraclass correlation coefficient, and Bland-Altman limits of agreement.

RESULTS

The highest mean difference was 0.30 mm between direct measurement and photogrammetry, 0.21 mm between direct measurement and 3D stereophotogrammetry, and 0.5 mm between photogrammetry and 3D stereophotogrammetry. The lowest agreement value was 0.965 in the Sn-Pro parameter between the photogrammetry and 3D stereophotogrammetry methods. Agreement between the two observers varied from 0.90 (Ch-Ch) to 0.99 (Sn-Me) in linear measurements. For intraobserver agreement, the highest difference between means was 0.33 for observer 1 and 1.42 mm for observer 2.

CONCLUSIONS

Measurements obtained using 3D stereophotogrammetry indicate that it may be an accurate and reliable imaging method for use in orthodontics.

Automatic Detection and Reproduction of Natural Head Position in Stereo-Photogrammetry

The aim of this study was to develop an automatic orientation calibration and reproduction method for recording the natural head position (NHP) in stereo-photogrammetry (SP). A board was used as the physical reference carrier for true verticals and NHP alignment mirror orientation. Orientation axes were detected and saved from the digital mesh model of the board. They were used for correcting the pitch, roll and yaw angles of the subsequent captures of patients' facial surfaces, which were obtained without any markings or sensors attached onto the patient. We tested the proposed method on two commercial active (3dMD) and passive (DI3D) SP devices. The reliability of the pitch, roll and yaw for the board placement were within ±0.039904°, ±0.081623°, and ±0.062320°; where standard deviations were 0.020234°, 0.045645° and 0.027211° respectively.

CONCLUSION

Orientation-calibrated stereo-photogrammetry is the most accurate method (angulation deviation within ±0.1°) reported for complete NHP recording with insignificant clinical error.

A Pilot Study on the Influence of Facial Expression on Measurements in Three-Dimensional Digital Surfaces of the Face in Infants With Cleft Lip and Palate

OBJECTIVE

Three-dimensional surface imaging is an increasingly popular modality for face measurements in infants with cleft lip and palate. Infants are noncompliant toward producing specific facial expressions, and selecting the appropriate moment of acquisition is challenging. The objective was to estimate amount and spatial distribution of deformation of the face due to facial expression in infants with cleft lip and palate and provide recommendations for an improved acquisition protocol, including a method of quality control in terms of obtaining images with true neutral expression.

MATERIAL AND METHODS

Three-dimensional surface images of ten 4-month-old infants with unrepaired cleft lip and palate were obtained using a 3dMDface stereophotogrammetric system. For each subject, five surface images judged as representing a neutral expression were obtained during the same photo session. Mean and maximum deformations were calculated. A formalized review was performed, allowing the image exhibiting the "best" neutral expression to be selected, thus decreasing errors due to residual facial expression.

RESULTS

Deformation due to facial expression generally increased from forehead to chin. The amount of deformation in three selected regions were determined: nose (mean, 1 mm; maximum = 3 mm); cleft region (mean, 2 mm; maximum = 5 mm); chin region (mean, 5 mm; maximum = 12 mm). Analysis indicated that introduction of a formalized review of images could reduce these errors by a factor of 2.

CONCLUSIONS

The continuous change of facial expression in infants represents a substantial source of error; however, this may be reduced by incorporating a formalized review into the acquisition protocol.

Comparison of three-dimensional surface-imaging systems

BACKGROUND

In recent decades, three-dimensional (3D) surface-imaging technologies have gained popularity worldwide, but because most published articles that mention them are technical, clinicians often have difficulties gaining a proper understanding of them. This article aims to provide the reader with relevant information on 3D surface-imaging systems. In it, we compare the most recent technologies to reveal their differences.

METHODS

We have accessed five international companies with the latest technologies in 3D surface-imaging systems: 3dMD, Axisthree, Canfield, Crisalix and Dimensional Imaging (Di3D; in alphabetical order). We evaluated their technical equipment, independent validation studies and corporate backgrounds.

RESULTS

The fastest capturing devices are the 3dMD and Di3D systems, capable of capturing images within 1.5 and 1 ms, respectively. All companies provide software for tissue modifications. Additionally, 3dMD, Canfield and Di3D can fuse computed tomography (CT)/cone-beam computed tomography (CBCT) images into their 3D surface-imaging data. 3dMD and Di3D provide 4D capture systems, which allow capturing the movement of a 3D surface over time. Crisalix greatly differs from the other four systems as it is purely web based and realised via cloud computing.

CONCLUSION

3D surface-imaging systems are becoming important in today's plastic surgical set-ups, taking surgeons to a new level of communication with patients, surgical planning and outcome evaluation. Technologies used in 3D surface-imaging systems and their intended field of application vary within the companies evaluated. Potential users should define their requirements and assignment of 3D surface-imaging systems in their clinical as research environment before making the final decision for purchase.

Outcome analysis after helmet therapy using 3D photogrammetry in patients with deformational plagiocephaly: the role of root mean square

Deformational plagiocephaly (DP) is a multifactorial non-synostotic cranial deformity with a reported incidence as high as 1 in 7 infants in North America. Treatment options have focused on non-operative interventions including head repositioning and the use of an orthotic helmet device. Previous studies have used linear and two dimensional outcome measures to assess changes in cranial symmetry after helmet therapy. Our objective was to demonstrate improvement in head shape after treatment with a cranial molding helmet by using Root Mean Square (RMS), a measure unique to 3D photogrammetry, which takes into account both changes in volume and shape over time. Three dimensional photographs were obtained before and after molding helmet treatment in 40 infants (4-10 months old) with deformational plagiocephaly. Anatomical reference planes and measurements were recorded using the 3dMD Vultus(®) analysis software. RMS was used to quantify symmetry by superimposing left and right quadrants and calculating the mean value of aggregate distances between surfaces. Over 95% of the patients demonstrated an improvement in symmetry with helmet therapy. Furthermore, when the sample of infants was divided into two treatment subgroups, a statistically significant correlation was found between the age at the beginning of treatment and the change in the RMS value. When helmet therapy was started before 7 months of age a greater improvement in symmetry was seen. This work represents application of the technique of RMS analysis to demonstrate the efficacy of treatment of deformational plagiocephaly with a cranial molding helmet.

Dissociating task difficulty from incongruence in face-voice emotion integration

In the everyday environment, affective information is conveyed by both the face and the voice. Studies have demonstrated that a concurrently presented voice can alter the way that an emotional face expression is perceived, and vice versa, leading to emotional conflict if the information in the two modalities is mismatched. Additionally, evidence suggests that incongruence of emotional valence activates cerebral networks involved in conflict monitoring and resolution. However, it is currently unclear whether this is due to task difficulty—that incongruent stimuli are harder to categorize—or simply to the detection of mismatching information in the two modalities. The aim of the present fMRI study was to examine the neurophysiological correlates of processing incongruent emotional information, independent of task difficulty. Subjects were scanned while judging the emotion of face-voice affective stimuli. Both the face and voice were parametrically morphed between anger and happiness and then paired in all audiovisual combinations, resulting in stimuli each defined by two separate values: the degree of incongruence between the face and voice, and the degree of clarity of the combined face-voice information. Due to the specific morphing procedure utilized, we hypothesized that the clarity value, rather than incongruence value, would better reflect task difficulty. Behavioral data revealed that participants integrated face and voice affective information, and that the clarity, as opposed to incongruence value correlated with categorization difficulty. Cerebrally, incongruence was more associated with activity in the superior temporal region, which emerged after task difficulty had been accounted for. Overall, our results suggest that activation in the superior temporal region in response to incongruent information cannot be explained simply by task difficulty, and may rather be due to detection of mismatching information between the two modalities.

A comparison study of different facial soft tissue analysis methods

OBJECTIVES

The purpose of this study was to evaluate several different facial soft tissue measurement methods.

MATERIALS AND METHODS

After marking 15 landmarks in the facial area of 12 mannequin heads of different sizes and shapes, facial soft tissue measurements were performed by the following 5 methods: Direct anthropometry, Digitizer, 3D CT, 3D scanner, and DI3D system. With these measurement methods, 10 measurement values representing the facial width, height, and depth were determined twice with a one week interval by one examiner. These data were analyzed with the SPSS program.

RESULTS

The position created based on multi-dimensional scaling showed that direct anthropometry, 3D CT, digitizer, 3D scanner demonstrated relatively similar values, while the DI3D system showed slightly different values. All 5 methods demonstrated good accuracy and had a high coefficient of reliability (>0.92) and a low technical error (<0.9 mm). The measured value of the distance between the right and left medial canthus obtained by using the DI3D system was statistically significantly different from that obtained by using the digital caliper, digitizer and laser scanner (p < 0.05), but the other measured values were not significantly different. On evaluating the reproducibility of measurement methods, two measurement values (Ls-Li, G-Pg) obtained by using direct anthropometry, one measurement value (N'-Prn) obtained by using the digitizer, and four measurement values (EnRt-EnLt, AlaRt-AlaLt, ChRt-ChLt, Sn-Pg) obtained by using the DI3D system, were statistically significantly different. However, the mean measurement error in every measurement method was low (<0.7 mm). All measurement values obtained by using the 3D CT and 3D scanner did not show any statistically significant difference.

CONCLUSION

The results of this study show that all 3D facial soft tissue analysis methods demonstrate favorable accuracy and reproducibility, and hence they can be used in clinical practice and research studies.

Three-dimensional methodology for photogrammetric acquisition of the soft tissues of the face: a new clinical-instrumental protocol

Background

The objective of this study is to define an acquisition protocol that is clear, precise, repeatable, simple, fast and that is useful for analysis of the anthropometric characteristics of the soft tissue of the face.

Methods

The analysis was carried out according to a new clinical-instrumental protocol that comprises four distinct phases: (1) setup of portable equipment in the space in which field analysis will be performed, (2) preparation of the subject and spatial positioning, (3) scanning of the subject with different facial expressions, and (4) treatment and processing of data. The protocol was tested on a sample comprising 66 female subjects (64 Caucasian, 1 Ethiopian, and 1 Brazilian) who were the finalists of an Italian national beauty contest in 2010. To illustrate the potential of the method, we report here the measurements and full analysis that were carried out on the facial model of one of the subjects who was scanned.

Results

This new protocol for the acquisition of faces is shown to be fast (phase 1, about 1 h; phase 2, about 1.5 min; phase 3, about 1.5 min; phase 4, about 15 min), simple (phases 1 to 3 requiring a short operator training period; only phase 4 requires expert operators), repeatable (with direct palpation of anatomical landmarks and marking of their positions on the face, the problem of identification of these same landmarks on the digital model is solved), reliable and precise (average precision of measurements, 0.5 to 0.6 mm over the entire surface of the face).

Conclusions

This standardization allows the mapping of the subjects to be carried out following the same conditions in a reliable and fast process for all of the subjects scanned.

Validity of the 3D VECTRA photogrammetric surface imaging system for cranio-maxillofacial anthropometric measurements

PURPOSE

The use of three-dimensional (3D) photography for anthropometric measurements is of increasing interest, especially in the cranio-maxillofacial field. Before standard implementation, accurate determination of the precision and accuracy of each system is mandatory.

METHODS

A mannequin head was labelled with 52 landmarks, and 28 three-dimensional images were taken using a commercially available five-pod 3D photosystem (3D VECTRA; Canfield, Fairfield, NJ) in different head positions. Distances between the landmarks were measured manually using a conventional calliper and compared with the digitally calculated distances acquired from labelling by two independent observers. The experimental set-up accounted for clinical circumstances by varying the positioning (vertical, horizontal, sagittal) of the phantom.

RESULTS

In the entire calliper measurement data set (n = 410), a significant difference (p = 0.02) between the directly measured and corresponding virtually calculated distances was found. The mean aberration between both modalities covering all data was 7.96 mm. No differences (p = 0.94) between the two groups were found using a cut-off of 10 % (leaving n = 369 distances) due to considerable errors in direct measurements and the necessary manual data translation. The mean diversity of both measurement modalities after cut-off was 1.33 mm (maximum, 6.70 mm). Inter-observer analysis of all 1,326 distances showed no difference (p = 0.99; maximal difference, 0.58 mm) in the digital measurements.

CONCLUSION

The precision and accuracy of this five-pod 3D photosystem suggests its suitability for clinical applications, particularly anthropometric studies. Three-hundred-and-sixty degree surface-contour mapping of the craniofacial region within milliseconds is particularly useful in paediatric patients. Proper patient positioning is essential for high-quality imaging.

Assessment of Volumetric Changes with a Best-Fit Method in Three-Dimensional Stereophotograms

Objective

Different three-dimensional stereophotogrammetry systems and analyzing methods exist that often use landmarks for comparison. Measurement errors in landmark or surface comparison are mostly within 1 mm, which seems clinically acceptable. The aim of this study was to validate a three-dimensional stereophotogrammetric best-fit method of assessing volumetric changes and to compare three devices.

Methods

The validation of the best-fit method was at first done on a life-size dummy head. Scans were made in the ideal position, as well as in four additional positions, and a scan was made in which a soft putty specimen was added to the dummy head. The comparison was executed with a best-fit method using triangulation. Student's t tests were used to detect statistically significant differences. Second, comparisons were made among scans of a white man in the ideal position and with volume changes added.

Results

The different positions tested for the dummy head showed no significant volume differences within each system or among systems. The differences found when adding a soft putty specimen fell into the same range as the differences between various positions. The differences within a live situation were 10 times greater compared with the dummy-head situation.

Conclusions

In a dummy-head situation, the different systems gave similar results when tested with a best-fit method. However, in live situations the differences may become 10 times greater, possibly due to different facial expressions. These differences may become clinically relevant and, therefore, further research in volumetric changes is needed.

Accurate facial morphologic measurements using a 3-camera photogrammetric method

OBJECTIVES

A new, low-cost photogrammetric method has been developed for facial morphometry applications. To evaluate the system, tests for the measurement and comparison of three-dimensional virtual faces were carried out in different subjects.

MATERIALS AND METHODS

Twenty adult white Italian subjects, 10 men and 10 women, of ages ranging from 23 to 37 years, were included in this study. Three cameras were finely calibrated, and the point precision vector length was calculated, together with the quality parameters. For each subject, 3 different acquisitions were performed. A tessellated surface was obtained from each point cloud. The comparison was made by aligning three-dimensional information from different models. Differences between 2 different models were estimated by analysis of the distances.

RESULTS

For the cases analyzed, the mean point precision overall root-mean-square vector length was 0.07 mm, with a SD of 0.027 mm. The results are reported for the system's capability of discriminating between the faces of different people. Results of comparisons between facial models of a single person were compared with those of comparisons between different subjects. Student's t-test revealed that the system was able to discriminate among different people, with a P > 95%. Two sex subgroups were formed: the mean error between subgroups ranged from 1.65 to 3.43 mm, and the mean ranged from 1.76 to 2.72 mm.

CONCLUSIONS

The experiments confirmed the capabilities and the accuracy of the proposed photogrammetric system. Facial comparison was performed by analysis of distances on three-dimensional virtual models.

Validation of a passive stereophotogrammetry system for imaging of the breast: a geometric analysis

The overall aim of this study was to assess the accuracy, reproducibility and stability of a high resolution passive stereophotogrammetry system to image a female mannequin torso, to validate measurements made on the textured virtual surface compared with those obtained using manual techniques and to develop an approach to make objective measurements of the female breast. 3D surface imaging was carried out on a textured female torso and measurements made in accordance with the system of mammometrics. Linear errors in measurements were less than 0.5mm, system calibration produced errors of less than 1.0mm over 94% over the surface and intra-rater reliability measured by ICC=0.999. The mean difference between manual and digital curved surface distances was 1.36 mm with maximum and minimum differences of 3.15 mm and 0.02 mm, respectively. The stereophotogrammetry system has been demonstrated to perform accurately and reliably with specific reference to breast assessment.

3D digital stereophotogrammetry: a practical guide to facial image acquisition

The use of 3D surface imaging technology is becoming increasingly common in craniofacial clinics and research centers. Due to fast capture speeds and ease of use, 3D digital stereophotogrammetry is quickly becoming the preferred facial surface imaging modality. These systems can serve as an unparalleled tool for craniofacial surgeons, proving an objective digital archive of the patient's face without exposure to radiation. Acquiring consistent high-quality 3D facial captures requires planning and knowledge of the limitations of these devices. Currently, there are few resources available to help new users of this technology with the challenges they will inevitably confront. To address this deficit, this report will highlight a number of common issues that can interfere with the 3D capture process and offer practical solutions to optimize image quality.

Accuracy and reproducibility of a 3-dimensional stereophotogrammetric imaging system

PURPOSE

To test the accuracy and reproducibility of a 3-dimensional (3D) stereophotogrammetric imaging system for measuring the facial soft tissues of healthy subjects.

MATERIALS AND METHODS

Three-dimensional soft tissue facial landmarks were obtained from the faces of 10 adult subjects, by use of a 3D stereophotogrammetric imaging system (Vectra; Canfield Scientific, Fairfield, NJ). Sixteen linear measurements were computed. Systematic and random errors between operators, calibration steps, and acquisitions were calculated.

RESULTS

No systematic errors were found for all performed tests (P > .05, paired t test). The method was repeatable, and random errors were always lower than 1 mm, except for the distance from cheilion to cheilion. Repeated sets of acquisition showed random errors up to 0.91 mm, without systematic biases.

CONCLUSION

The 3D stereophotogrammetric imaging system can assess the coordinates of facial landmarks with good precision and reproducibility. The method is fast and can obtain facial measurements with few errors.