Metric and morphological assessment of facial features: a study on three European populations

Anthropometry and Current Aesthetic Concept of the Lower Third of the Face and Lips in Caucasian Adult Population: A Systematic Review and Meta-Analysis

BACKGROUND

The lack of standardization of the norms and aesthetic concept of the lower third of the face and lips creates challenges in reconstructive surgery and aesthetic procedures. A large-scale, anthropometric measurements summary poses an alternative for establishing universal patterns.

METHODS

A systematic review was conducted by searching PubMed, Embase, Google Scholar and Web of Science using keywords: lip, face, aesthetics, beauty, anthropometry and Caucasian. Seventy records were included in the review and checked in detail in terms of available data.

RESULTS

The study contains a meta-analysis of twelve parameters with sufficient quantitative data-lip width, nose width, facial width, lower third of the face height, midline mandible height, total height of the upper and lower lip, upper and lower vermilion height, cutaneous upper lip height and nasolabial and mentolabial angle.

CONCLUSIONS

The review provides a detailed database of primary anthropometric studies of lips and perioral regions of the healthy Caucasian population. The attractiveness of the region is focused on uniformity of proportions. Notably, results acquired with different methods of measurement are not interchangeable. Despite many published anthropometric studies, systems for conducting the measurements and reporting the results are not sufficiently unified to quantitatively assess meticulous key aesthetic clinical parameters.

LEVEL OF EVIDENCE I

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 Table of Contents or online Instructions to Authors www.springer.com/00266 .

De Novo Dissecting the Three-Dimensional Facial Morphology of 2379 Han Chinese Individuals

Phenotypic diversity, especially that of facial morphology, has not been fully investigated in the Han Chinese, which is the largest ethnic group in the world. In this study, we systematically analyzed a total of 14,838 facial traits representing 15 categories with both a large-scale three-dimensional (3D) manual landmarking database and computer-aided facial segmented phenotyping in 2379 Han Chinese individuals. Our results illustrate that homogeneous and heterogeneous facial morphological traits exist among Han Chinese populations across the three geographical regions: Zhengzhou, Taizhou, and Nanning. We identified 1560 shared features from extracted phenotypes, which characterized well the basic facial morphology of the Han Chinese. In particular, heterogeneous phenotypes showing population structures corresponded to geographical subpopulations. The greatest facial variation among these geographical populations was the angle of glabella, left subalare, and right cheilion (p = 3.4 × 10-161). Interestingly, we found that Han Chinese populations could be classified into northern Han, central Han, and southern Han at the phenotypic level, and the facial morphological variation pattern of central Han Chinese was between the typical differentiation of northern and southern Han Chinese. This result was highly consistent with the results revealed by the genetic data. These findings provide new insights into the analysis of multidimensional phenotypes as well as a valuable resource for further facial phenotype-genotype association studies in Han Chinese and East Asian populations.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43657-023-00109-x.

Three-dimensional anthropometric study of the facial morphology of black African Senegalese: 3D photogrammetric approach

Introduction

Anthropometric features are important in determining gender and ethnic groups. The aim of this 3D photogrammetric study was to assess the face of Senegalese subjects.

Material and methods

A total of 104 3D facial photographs taken with the Bellus 3D application were studied. Measurements were taken at various anthropometric points using Meshlab software. The acquired data were recorded and processed using Jamovi software version 1.8.4.0. Correlations between the quantitative variables were tested and only one with a significance of p 0.05 was retained.

Results

Overall, measured distances were higher in men. A statistically significant difference between men and women was found for nose width (p0. 001), face width (p < 0.005) and face height (p0. 0002). Conclusion: 3D anthropometric analysis shows a fairly significant sexual dimorphism, with males having greater facial and nasal proportions. A leptoprosopic (long) facial shape and a mesorrhine nose were maintained.

Automatic landmarking identifies new loci associated with face morphology and implicates Neanderthal introgression in human nasal shape

We report a genome-wide association study of facial features in >6000 Latin Americans based on automatic landmarking of 2D portraits and testing for association with inter-landmark distances. We detected significant associations (P-value <5 × 10-8) at 42 genome regions, nine of which have been previously reported. In follow-up analyses, 26 of the 33 novel regions replicate in East Asians, Europeans, or Africans, and one mouse homologous region influences craniofacial morphology in mice. The novel region in 1q32.3 shows introgression from Neanderthals and we find that the introgressed tract increases nasal height (consistent with the differentiation between Neanderthals and modern humans). Novel regions include candidate genes and genome regulatory elements previously implicated in craniofacial development, and show preferential transcription in cranial neural crest cells. The automated approach used here should simplify the collection of large study samples from across the world, facilitating a cosmopolitan characterization of the genetics of facial features.

Expanding the Classic Facial Canons: Quantifying Intercanthal Distance in a Diverse Patient Population

Background:

The intercanthal distance (ICD) is central to our perception of facial proportions, and it varies according to gender and ethnicity. Current standardized reference values do not reflect the diversity among patients. Therefore, the authors sought to provide an evidence-based and gender/ethnicity-specific reference when evaluating patients’ ICD.

Methods:

As per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, a systematic search of PubMed, Medline, and Embase was carried out for studies reporting on the ICD. Demographics, study characteristics, and ICDs were extracted from included studies. ICD values were then pooled for each ethnicity and stratified by gender. The difference between men and women, and that across ethnicities and measurement types were compared by means of independent sample t-test and one-way ANOVA (SPSS v.24).

Results:

A total of 67 studies accounting for 22,638 patients and 118 ethnic cohorts were included in this pooled analysis. The most reported ethnicities were Middle Eastern (n = 6629) and Asian (n = 5473). ICD values (mm) in decreasing order were: African 38.5 ± 3.2, Asian 36.4 ± 1.6, Southeast Asian 32.8 ± 2.0, Hispanic 32.3 ± 2.0, White 31.4 ± 2.5, and Middle Eastern 31.2 ± 1.5. A statistically significant difference (P < 0.05) existed between all ethnic cohorts, between genders among most cohorts, and between most values stratified by measurement type.

Conclusions:

Our standards of craniofacial anthropometry must evolve from the neoclassical canons using White values as references. The values provided in this review can aid surgeons in appreciating the gender- and ethnic-specific differences in the ICD of their patients.

3D‐3D facial registration method applied to personal identification: Does it work with limited portions of faces? An experiment in ideal conditions

Personal identification of faces represents a challenging issue, especially for what concerns the quantification of the comparison. The 3D‐3D superimposition approach proved to distinguish between matches and mismatches. However, the potential of this procedure applied to cases where only parts of faces are visible still has to be verified. This study aimed at verifying the applicability of a 3D‐3D procedure to faces divided into three thirds. 3D models of fifty male subjects acquired through stereophotogrammetry were used. The 3D facial models were divided into upper, middle, and lower thirds and registered onto other models belonging to the same and different individuals according to the least point‐to‐point distance. In total, 50 matches and 50 mismatches were analyzed. RMS value (root mean square) of point‐to‐point distance between the two facial surfaces was calculated through VAM® software. Statistically significant differences between matches and mismatches in each facial third were assessed through Mann–Whitney test (p < 0.05). On average, RMS value in matches was 0.32 ± 0.12 mm in upper third, 0.36 ± 0.15 mm in middle third, and 0.40 ± 0.20 mm in lower third, respectively; in mismatches, RMS value was 1.40 ± 0.32 mm in upper third, 1.96 ± 0.58 mm in middle third, and 2.39 ± 0.90 mm in lower third, respectively. Differences in RMS values between matches and mismatches were significantly different for all facial thirds, without superimpositions (p < 0.01). This study shows that the existing 3D‐3D superimposition methods may be useful also when only a limited portion of face is visible in ideal conditions. Their application to forensic cases of identification still needs to be verified.

Validation of forensic facial comparison by morphological analysis in photographic and CCTV samples

Between the ever-increasing availability of surveillance evidence and expert-based forensic facial comparison being considered admissible in court, confirming its validity is paramount. Facial comparison is most commonly conducted using morphological analysis (MA), a largely untested feature-based approach. This study aimed at validating the current recommended practice of MA in both standardised and suboptimal surveillance samples. Face pools of 175 South African males were compiled with a series of facial photographs, using images from the Wits Face Database. The first 75 face pools consisted of wildtype (unstandardised) high-quality target photographs, while the remaining 100 face pools consisted of suboptimal closed-circuit television (CCTV) target images. Target images were compared to high-quality standardised photographs. Face pools were analysed using the Facial Identification Scientific Working Group's guidelines and feature list. Confusion matrices were used to determine the performance of MA in each cohort. MA was found highly accurate (chance-corrected accuracy (CCA): 99.1%) and reliable (κ = 0.921) in the photographic sample and less accurate (CCA: 82.6%) and reliable (κ = 0.743), in the CCTV sample. Higher false-positive and false-negative rates were noted for the CCTV sample, with the majority of errors resulting in false-negative outcomes. The decreased performance in the CCTV sample was attributed to various factors including image quality, angle of recording and lighting. Other studies testing facial comparison identified lower accuracies and reliability across various conditions. Better performance was found here and in other studies that included some form of facial feature list, reinforcing the importance of using a systematic facial feature list.

A GWAS in Latin Americans identifies novel face shape loci, implicating VPS13B and a Denisovan introgressed region in facial variation

To characterize the genetic basis of facial features in Latin Americans, we performed a genome-wide association study (GWAS) of more than 6000 individuals using 59 landmark-based measurements from two-dimensional profile photographs and ~9,000,000 genotyped or imputed single-nucleotide polymorphisms. We detected significant association of 32 traits with at least 1 (and up to 6) of 32 different genomic regions, more than doubling the number of robustly associated face morphology loci reported until now (from 11 to 23). These GWAS hits are strongly enriched in regulatory sequences active specifically during craniofacial development. The associated region in 1p12 includes a tract of archaic adaptive introgression, with a Denisovan haplotype common in Native Americans affecting particularly lip thickness. Among the nine previously unidentified face morphology loci we identified is the VPS13B gene region, and we show that variants in this region also affect midfacial morphology in mice.

Facial perception, self-esteem and psychosocial well-being in patients after nasal surgery due to trauma, cancer and aesthetic needs (cluster analysis of multiple interrelations)

Background: Facial anthropometric measurements in relation to self-esteem and self-perception have become a very popular topic, not only in anthropological and psychological research, but also in plastic reconstructive surgery.Aim: To compare the interrelations between facial perception, self-esteem and psychosocial well-being in patients after nasal surgery due to trauma, cancer and aesthetic needs.Subjects and methods: In total, ninety patients after nasal surgery (due to trauma, cancer and aesthetic reasons), and thirty control persons underwent facial anthropometry and answered questions related to facial perception (FP), self-esteem (SE) and psychosocial well-being (PW). Cluster analysis was performed.Results: Facial measurements were not related to the perception of the whole face in all investigated persons. The whole face and nasal perception were interrelated in the majority of male groups and in the control female group. SE in females from the control and cancer groups was not related to real facial parameters or FP, however, in females after aesthetic surgery it was related to nasal tip protrusion. SE in females after nasal surgery due to trauma was strongly related to FP. SE in almost all groups of males was related to real facial parameters, and in males after aesthetic surgery it was related to FP. PW was mostly linked to SE in males and females after aesthetic surgery, in other groups it was related to FP.Conclusions: FP was most frequently not related to real facial measurements; however, it was related to PW. Patients after aesthetic nasal surgery had specific relations between FP, SE and PW.

Three-dimensional shape variation and sexual dimorphism of the face, nose, and mouth of Japanese individuals

Three-dimensional (3D) shape variations of the face and facial parts in Japanese adults were examined to collect basic data to be used for facial comparison in forensics. In total, 1000 3D facial scans (500 males, 500 females) of Japanese individuals were re-meshed into anatomically homologous shape models and analyzed by principal component analysis (PCA) after Procrustes superimposition. Facial parts (the nose and the mouth) were segmented from homologous face models and analyzed by PCA, too. Among all kinds of objects (the face, the nose, and the mouth), the most predominant shape variation represented by the first principal component (PC1) was the height-width proportion. The second largest variation (PC2) in the face and the nose was depth; for the mouth, it was the relative protrusion of the upper and lower lips. We interpreted predominant shape variations represented by the first five principal components (PCs) in each object. Asymmetric shape variations were observed within these PCs for the nose and the mouth. Sexual dimorphism of the face and the facial parts was also examined by testing the significance of sex-linked differences in PC scores. A significant difference was found between males and females for many PCs. Sexual dimorphism was examined also by emphasizing the shape difference between average male and female faces. Our results revealed predominant 3D shape variations and sexual dimorphism of the face and facial parts. The results may be informative for performing facial comparison in police investigations, an increasingly used technique.

Forensic Facial Reconstruction: A Systematic Review of Nasal Prediction Techniques

Prediction facial features from the skull are recurring theme on the forensic literature. The nose has been investigated since it has a significant role in facial recognition and the literature shows that there is not an universal method for nasal prediction. This study aimed to conduct a systematic review to analyze what are the most consistent techniques of nasal reconstruction. Primary studies describing or validating nasal reconstruction techniques in adults and published in journals of Forensic Sciences were included in this review. Tedeschi-Oliveira's method positioned nasal tip with acceptable accuracy as Gerasimov's method. The Krogman's and Iscan's technique underestimated nasal projection in North Americans. The Prokopec's and Ubelaker's method obtained accuracy in Caucasoid. George's method presented results similar to reference standard in Caucasoid. In a supplementary way, studies are needed to accurately estimate the nasal width.

Automatic classification of human facial features based on their appearance

Classification or typology systems used to categorize different human body parts have existed for many years. Nevertheless, there are very few taxonomies of facial features. Ergonomics, forensic anthropology, crime prevention or new human-machine interaction systems and online activities, like e-commerce, e-learning, games, dating or social networks, are fields in which classifications of facial features are useful, for example, to create digital interlocutors that optimize the interactions between human and machines. However, classifying isolated facial features is difficult for human observers. Previous works reported low inter-observer and intra-observer agreement in the evaluation of facial features. This work presents a computer-based procedure to automatically classify facial features based on their global appearance. This procedure deals with the difficulties associated with classifying features using judgements from human observers, and facilitates the development of taxonomies of facial features. Taxonomies obtained through this procedure are presented for eyes, mouths and noses.

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.

Population specific data improves Fordisc®'s performance in Italians

Using discriminant functions based on morphometric data is one of the most approved methods for sex and ancestry estimation on skeletons. Nevertheless, population data from various parts of the world is needed in order to reliably classify an individual into a group. Due to population variation even sex estimation is biased when there is a lack of adequate data. Software that computes discriminant functions based on morphometric data is Fordisc^®. Unfortunately, the above mentioned effects reduce its applicability in countries other than the US. For improvement of this situation data collection is currently performed extensively. The present paper shows a comparison of an Italian sample from the identified modern skeletal collection of CAL (Collezione Antropologica Labanof) [1] (Cattaneo, 2018) at the Institute of Legal Medicine Milan, Italy with a Euro-American sample from the Forensic Data Bank at the University of Tennessee Knoxville, USA. Fordisc^® 3.1 was used to study population differences and sexual dimorphism. The analyzes were performed on a selection of 19 highly influential measurements that are present in most individuals of both groups respectively. Italian crania show in relation to Euro-Americans wider and lower vaults with shorter cranial bases and wider faces. The degree of sexual dimorphism is similar in both groups. Yet there is a shift in the absolute value range for males and females that biases sex estimation by almost 25% when an individual is classified on the respective other discriminant function. Our results provide explanations for Fordisc^®'s unsatisfying performance on non-US individuals. At the same time they show that significant improvement is achieved by adding more population samples to its dataset.

Variation of facial features among three African populations: Body height match analyses

Body height is one of the variables that show a correlation with facial craniometry. Here we seek to discriminate the three populations (Nigerians, Ugandans and Kenyans) using facial craniometry based on different categories of body height of adult males. A total of 513 individuals comprising 234 Nigerians, 169 Ugandans and 110 Kenyans with mean age of 25.27, s=5.13 (18-40 years) participated. Paired and unpaired facial features were measured using direct craniometry. Multivariate and stepwise discriminate function analyses were used for differentiation of the three populations. The result showed significant overall facial differences among the three populations in all the body height categories. Skull height, total facial height, outer canthal distance, exophthalmometry, right ear width and nasal length were significantly different among the three different populations irrespective of body height categories. Other variables were sensitive to body height. Stepwise discriminant function analyses included maximum of six variables for better discrimination between the three populations. The single best discriminator of the groups was total facial height, however, for body height >1.70m the single best discriminator was nasal length. Most of the variables were better used with function 1, hence, better discrimination than function 2. In conclusion, adult body height in addition to other factors such as age, sex, and ethnicity should be considered in making decision on facial craniometry. However, not all the facial linear dimensions were sensitive to body height.

A genome-wide association scan implicates DCHS2, RUNX2, GLI3, PAX1 and EDAR in human facial variation

We report a genome-wide association scan for facial features in ∼6,000 Latin Americans. We evaluated 14 traits on an ordinal scale and found significant association (P values<5 × 10⁻⁸) at single-nucleotide polymorphisms (SNPs) in four genomic regions for three nose-related traits: columella inclination (4q31), nose bridge breadth (6p21) and nose wing breadth (7p13 and 20p11). In a subsample of ∼3,000 individuals we obtained quantitative traits related to 9 of the ordinal phenotypes and, also, a measure of nasion position. Quantitative analyses confirmed the ordinal-based associations, identified SNPs in 2q12 associated to chin protrusion, and replicated the reported association of nasion position with SNPs in PAX3. Strongest association in 2q12, 4q31, 6p21 and 7p13 was observed for SNPs in the EDAR, DCHS2, RUNX2 and GLI3 genes, respectively. Associated SNPs in 20p11 extend to PAX1. Consistent with the effect of EDAR on chin protrusion, we documented alterations of mandible length in mice with modified Edar funtion.

Humans show great diversity in facial appearance and this variation is highly heritable. Here, Andres Ruiz-Linares and colleagues examined facial features in admixed Latin Americans and identify genome-wide associations for 14 facial traits, including four gene loci (RUNX2, GLI3, DCHS2 and PAX1) influencing nose morphology.

Quantitative assessment of the facial features of a Mexican population dataset

The present study describes the morphological variation of a large database of facial photographs. The database comprises frontal (386 female, 764 males) and lateral (312 females, 666 males) images of Mexican individuals aged 14-69 years that were obtained under controlled conditions. We used geometric morphometric methods and multivariate statistics to describe the phenotypic variation within the dataset as well as the variation regarding sex and age groups. In addition, we explored the correlation between facial traits in both views. We found a spectrum of variation that encompasses broad and narrow faces. In frontal view, the latter is associated to a longer nose, a thinner upper lip, a shorter lower face and to a longer upper face, than individuals with broader faces. In lateral view, antero-posteriorly shortened faces are associated to a longer profile and to a shortened helix, than individuals with longer faces. Sexual dimorphism is found in all age groups except for individuals above 39 years old in lateral view. Likewise, age-related changes are significant for both sexes, except for females above 29 years old in both views. Finally, we observed that the pattern of covariation between views differs in males and females mainly in the thickness of the upper lip and the angle of the facial profile and the auricle. The results of this study could contribute to the forensic practices as a complement for the construction of biological profiles, for example, to improve facial reconstruction procedures.

Three-dimensional prediction of the human eyeball and canthi for craniofacial reconstruction using cone-beam computed tomography

An anatomical relationship between the hard and soft tissues of the face is mandatory for facial reconstruction. The purpose of this study was to investigate the positions of the eyeball and canthi three-dimensionally from the relationships between the facial hard and soft tissues using cone-beam computed tomography (CBCT). CBCT scan data of 100 living subjects were used to obtain the measurements of facial hard and soft tissues. Stepwise multiple regression analyses were carried out using the hard tissue measurements in the orbit, nasal bone, nasal cavity and maxillary canine to predict the most probable positions of the eyeball and canthi within the orbit. Orbital width, orbital height, and orbital depth were strong predictors of the eyeball and canthi position. Intercanine width was also a predictor of the mediolateral position of the eyeball. Statistically significant regression models for the positions of the eyeball and canthi could be derived from the measurements of orbit and maxillary canine. These results suggest that CBCT data can be useful in predicting the positions of the eyeball and canthi three-dimensionally.

Are human faces unique? A metric approach to finding single individuals without duplicates in large samples

In the forensic sciences it is inferred that human individuals are unique and thus can be reliably identified. The concept of individual uniqueness is claimed to be unprovable because another individual of same characteristics may exist if population size were infinite. It is proposed to replace "unique" with "singular" defined as a situation when only one individual in a specific population has a particular set of characteristics. The likelihood that in a population there will be no duplicate individual with exactly the same set of characteristics can be calculated from datasets of relevant characteristics. To explore singularity, the ANSUR database which contains anthropometric measurements of 3982 individuals was used. Eight facial metric traits were used to search for duplicates. With the addition of each trait, the chances of finding a duplicate were reduced until singularity was achieved. Singularity was consistently achieved at a combination of the maximum of seven traits. The larger the traits in dimension, the faster singularity was achieved. By exploring how singularity is achieved in subsamples of 200, 500, etc. it has been determined that about one trait needs to be added when the size of the target population increases by 1000 individuals. With the combination of four facial dimensions, it is possible to achieve a probability of finding a duplicate of the order of 10(-7), while, the combination of 8 traits reduces probability to the order of 10(-14), that is less than one in a trillion.

Photo anthropometric variations in Japanese facial features: Establishment of large-sample standard reference data for personal identification using a three-dimensional capture system

This study clarifies the anthropometric variations of the Japanese face by presenting large-sample population data of photo anthropometric measurements. The measurements can be used as standard reference data for the personal identification of facial images in forensic practices. To this end, three-dimensional (3D) facial images of 1126 Japanese individuals (865 male and 261 female Japanese individuals, aged 19-60 years) were acquired as samples using an already validated 3D capture system, and normative anthropometric analysis was carried out. In this anthropometric analysis, first, anthropological landmarks (22 items, i.e., entocanthion (en), alare (al), cheilion (ch), zygion (zy), gonion (go), sellion (se), gnathion (gn), labrale superius (ls), stomion (sto), labrale inferius (li)) were positioned on each 3D facial image (the direction of which had been adjusted to the Frankfort horizontal plane as the standard position for appropriate anthropometry), and anthropometric absolute measurements (19 items, i.e., bientocanthion breadth (en-en), nose breadth (al-al), mouth breadth (ch-ch), bizygomatic breadth (zy-zy), bigonial breadth (go-go), morphologic face height (se-gn), upper-lip height (ls-sto), lower-lip height (sto-li)) were exported using computer software for the measurement of a 3D digital object. Second, anthropometric indices (21 items, i.e., (se-gn)/(zy-zy), (en-en)/(al-al), (ls-li)/(ch-ch), (ls-sto)/(sto-li)) were calculated from these exported measurements. As a result, basic statistics, such as the mean values, standard deviations, and quartiles, and details of the distributions of these anthropometric results were shown. All of the results except "upper/lower lip ratio (ls-sto)/(sto-li)" were normally distributed. They were acquired as carefully as possible employing a 3D capture system and 3D digital imaging technologies. The sample of images was much larger than any Japanese sample used before for the purpose of personal identification. The measurements will be useful as standard reference data for forensic practices and as material data for future studies in this field.

Three-dimensional facial distances of Northern Sudanese persons from childhood to young adulthood

No current age- and gender-related normative data exist for the dimensions of facial structures in Northern Sudanese subjects. In the current study information about normal sex- and age-related linear distances is provided. The three-dimensional coordinates of 14 landmarks on the facial soft tissues were obtained using a hand-held laser scanner in 653 healthy Northern Sudanese subjects (326 males and 327 females) aged 4-30 years. From the landmarks, 13 linear distances were calculated, and averaged for age and sex. Comparisons were performed by factorial analysis of variance. All analyzed linear soft tissue facial dimensions were significantly larger in men than in women (p < 0.01), except mouth width (ch-ch), upper facial height (n-sn), mandibular body length (pg-go) and width (go-go). All measurements underwent significant modifications as a function of age (p < 0.01), with significant age × sex interactions (p < 0.01) for all linear dimensions except lower face height (sn-pg). Overall, when compared to literature data for African and Caucasoid subjects, several differences were found, pointing to the necessity of ethnic-specific data. Data collected in the present investigation could serve as a database for the quantitative description of human facial morphology during normal growth and development.

Morphometry of the soft tissues of the orbital region in Northern Sudanese persons

The orbital region plays a predominant role in the evaluation of the craniofacial complex. No current normative data exist for Northern Sudanese subjects. In the current study information about normal sex- and age-related dimensions of the orbital region was provided. The three-dimensional coordinates of ten landmarks on the orbital soft tissues were obtained using a hand-held laser scanner in 654 healthy Northern Sudanese subjects aged 4-30 years. From the landmarks, biocular and intercanthal widths, paired height and inclination of the orbit relative to both the true horizontal (head in natural head position) and Frankfurt plane, length and inclination of the eye fissure, the relevant ratios, were calculated, and averaged for age and sex. Comparisons were performed by factorial analysis of variance. All analysed linear soft-tissue orbital dimensions, except intercanthal width and left orbital height, were significantly larger in men than in women (p<0.01). A significant sexual dimorphism was found also for the height-to-width ratios (larger in women in most age groups), the orbital inclinations vs. the true horizontal and Frankfurt plane (both measurements were almost always larger in men than in women), and the right side inclination of the eye fissure vs. the true horizontal (larger in women than in men), while no sex-related differences were observed for the left side inclination of the eye fissure vs. the true horizontal. All measurements but the right side inclination of the eye fissure vs. the true horizontal underwent significant modifications as a function of age, with several significant age×sex interactions. Biocular and intercanthal widths, orbital height, length of the eye fissure, all increased from childhood to young adulthood; in the second decade of life all age-related increments were larger in men than in women. Overall, when compared to literature data for African and Caucasoid subjects, several differences were found, pointing to the necessity of ethnic-specific data. Data collected in the present investigation could serve as a database for the quantitative description of human orbital morphology during normal growth and development. Forensic applications (evaluations of traumas, craniofacial alterations, teratogenic-induced conditions, facial reconstruction, ageing of living and dead people, personal identification) may also benefit from age- and sex-based data banks.

Skin injury model classification based on shape vector analysis

Background: Skin injuries can be crucial in judicial decision making. Forensic experts base their classification on subjective opinions. This study investigates whether known classes of simulated skin injuries are correctly classified statistically based on 3D surface models and derived numerical shape descriptors.

Methods: Skin injury surface characteristics are simulated with plasticine. Six injury classes – abrasions, incised wounds, gunshot entry wounds, smooth and textured strangulation marks as well as patterned injuries - with 18 instances each are used for a k-fold cross validation with six partitions. Deformed plasticine models are captured with a 3D surface scanner. Mean curvature is estimated for each polygon surface vertex. Subsequently, distance distributions and derived aspect ratios, convex hulls, concentric spheres, hyperbolic points and Fourier transforms are used to generate 1284-dimensional shape vectors. Subsequent descriptor reduction maximizing SNR (signal-to-noise ratio) result in an average of 41 descriptors (varying across k-folds). With non-normal multivariate distribution of heteroskedastic data, requirements for LDA (linear discriminant analysis) are not met. Thus, shrinkage parameters of RDA (regularized discriminant analysis) are optimized yielding a best performance with λ = 0.99 and γ = 0.001.

Results: Receiver Operating Characteristic of a descriptive RDA yields an ideal Area Under the Curve of 1.0for all six categories. Predictive RDA results in an average CRR (correct recognition rate) of 97,22% under a 6 partition k-fold. Adding uniform noise within the range of one standard deviation degrades the average CRR to 71,3%.

Conclusions: Digitized 3D surface shape data can be used to automatically classify idealized shape models of simulated skin injuries. Deriving some well established descriptors such as histograms, saddle shape of hyperbolic points or convex hulls with subsequent reduction of dimensionality while maximizing SNR seem to work well for the data at hand, as predictive RDA results in CRR of 97,22%. Objective basis for discrimination of non-overlapping hypotheses or categories are a major issue in medicolegal skin injury analysis and that is where this method appears to be strong. Technical surface quality is important in that adding noise clearly degrades CRR.

Trial registration: This study does not cover the results of a controlled health care intervention as only plasticine was used. Thus, there was no trial registration.