The application of volume deformation to three-dimensional facial reconstruction: a comparison with previous techniques

A computerized facial approximation method for Homo sapiens based on facial soft tissue thickness depths and geometric morphometrics

Facial approximation (FA) provides a promising means of generating the possible facial appearance of a deceased person. It facilitates exploration of the evolutionary forces driving anatomical changes in ancestral humans and can capture public attention. Despite the recent progress made toward improving the performance of FA methods, a limited understanding of detailed quantitative craniofacial relationships between facial bone and soft tissue morphology may hinder their accuracy, and hence subjective experience and artistic interpretation are required. In this study, we explored craniofacial relationships among human populations based upon average facial soft tissue thickness depths (FSTDs) and covariations between hard and soft tissues of the nose and mouth using geometric morphometrics. Furthermore, we proposed a computerized method to assign the learned craniofacial relationships to generate a probable facial appearance of Homo sapiens, reducing human intervention. A smaller resemblance comparison (an average Procrustes distance was 0.0258 and an average Euclidean distance was 1.79 mm) between approximated and actual faces and a greater recognition rate (91.67%) tested by a face pool indicated that average dense FSTDs contributed to raising the accuracy of approximated faces. Results of partial least squares (PLS) analysis showed that nasal and oral hard tissues have an effect on their soft tissues separately. However, relatively weaker RV correlations (<0.4) and greater approximation errors suggested that we need to be cautious about the accuracy of the approximated nose and mouth soft tissue shapes from bony structures. Overall, the proposed method can facilitate investigations of craniofacial relationships and potentially improve the reliability of the approximated faces for use in numerous applications in forensic science, archaeology, and anthropology.

Facial reconstruction using 3-D computerized method: A scoping review of Methods, current Status, and future developments

Facial reconstruction (otherwise known as facial approximation) is an alternative method that has been widely accepted in forensic anthropological and archaeological circumstances. This method is considered useful for creating the virtual face of a person based on skull remain. Three-dimensional (3-D) traditional facial reconstruction (known as sculpture or manual method) has been recognized for more than a century; however, it was declared to be subjective and required anthropological training. Until recently, with the progression of computational technologies, many studies attempted to develop a more appropriate method, so-called the 3-D computerized facial reconstruction. This method also relied on anatomical knowledge of the face-skull relationship, divided into semi- and automated based computational method. The 3-D computerized facial reconstruction makes it more rapid, more flexible, and more realistic to generate multiple representations of faces. Moreover, new tools and technology are continuously generating fascinating and sound research as well as encouraging multidisciplinary collaboration. This has led to a paradigm shift in the 3-D computerized facial reconstruction to a new finding and new technique based on artificial intelligence in academia. Based on the last 10-years scientific-published documents, this article aims to explain the overview of the 3-D computerized facial reconstruction and progression as well as an issue relating to future directions to encourage further improvement.

A detailed review of forensic facial reconstruction techniques

Facial reconstruction is an effective forensic technique that can help recreate a victim's facial appearance from the skull. It is typically used to assist law enforcement agencies to identify missing deceased persons. Reconstruction techniques are usually based on the relationship between the underlying hard tissues, such as bone structure, and soft tissues such as the facial muscles and facial features. Facial reconstruction can be a feasible alternative to identify the remains from a decomposed, mutilated, or skeletonised corpse. It is important to remember that although the outcomes are empirical in nature, the technique has been applied widely in many situations. Recent advancements in technology and computer-based techniques have increased the accuracy and validity of this forensic discipline. We consider the most commonly used facial reconstruction techniques in this paper, with a detailed description of manual 3D techniques.

Using Computed Tomography (CT) Data to Build 3D Resources for Forensic Craniofacial Identification

Forensic craniofacial identification encompasses the practices of forensic facial approximation (aka facial reconstruction) and craniofacial superimposition within the field of forensic art in the United States. Training in forensic facial approximation methods historically has used plaster copies, high-cost commercially molded skulls, and photographs. Despite the increased accessibility of computed tomography (CT) and the numerous studies utilizing CT data to better inform facial approximation methods, 3D CT data have not yet been widely used to produce interactive resources or reference catalogs aimed at forensic art practitioner use or method standardization. There are many free, open-source 3D software packages that allow engagement in immersive studies of the relationships between the craniofacial skeleton and facial features and facilitate collaboration between researchers and practitioners. 3D CT software, in particular, allows the bone and soft tissue to be visualized simultaneously with tools such as transparency, clipping, and volume rendering of underlying tissues, allowing for more accurate analyses of bone to soft tissue relationships. Analyses and visualization of 3D CT data can not only facilitate basic research into facial variation and anatomical relationships relevant for reconstructions but can also lead to improved facial reconstruction guidelines. Further, skull and face surface models exported in digital 3D formats allow for 3D printing of custom reference models and novel training materials and modalities for practitioners. This chapter outlines the 3D resources that can be built from CT data for forensic craniofacial identification methods, including how to view 3D craniofacial CT data and modify surface models for 3D printing.

Facial soft tissue thickness differences among different vertical facial patterns

In forensic facial approximation, facial soft tissue thickness (FSTT) measurements play a major role. These values are affected by many factors such as ethnicity, age and sex, in addition to measurement errors. We hypothesize that an additional source of error is the lack of consideration of facial type in the assessment of FSTT norms. The purpose of this study was to: 1- evaluate the presence of significant effects of vertical facial type within the FSTT measurements in adults and 2- assess the correlations between FSTT and hard and soft tissue cephalometric measurements. The sample consisted of the lateral cephalometric radiographs of 222 adult individuals (87 males; 135 females, 23.49±6.24 years of age) with normal occlusion and balanced profiles. Hard and soft tissue cephalometric measurements were taken, in addition to FSST at 10 facial landmarks. The sample was categorized into 3 vertical pattern groups based on the MP/SN angle: hypodivergent, normodivergent and hyperdivergent. Statistical analyses included MANOVA test and Pearson moment product for associations among variables. Statistically significant effect of vertical divergence on FSTT values was limited to the levels of Stomion, Labiomentale and Pogonion and FSTT measurements were associated with measurements related to the lower face (Lm and Pog) Moderate to high correlations between mandibular length and ramus length and FSTT values related to the lower face (LL, Lm and Pog mainly) emphasize further the important role of the underlying skeleton.

Will different sagittal and vertical skeletal types relate the soft tissue thickness: A study in Chinese female adults

Facial reconstruction is a classical technique in forensic anthropology to reestablish the contours of the soft tissues over the skull. The accurate facial soft tissue data plays an essential role in forensic facial reconstruction. However, according to previous studies, various skeletal types might relate to different thickness in facial soft tissue. Until now, there are few publications focusing on the relationship between facial soft tissue thickness (FSTT) and different skeletal types, and none of them analyze the FSTT according to various sagittal and vertical skeletal types. The aim of this study was to testify the possible existence of correlations between FSTT and different skeletal types. In order to exclude interference from age, sex, ethnicity and body mass index (BMI) factors, we collected lateral projection X-rays data of 270 Chinese female aged 19-26 years with nomal BMI and divided them into various skeletal groups. Soft tissue thickness measurements were mainly based on 10 anthropological landmarks of the skull and statistics were analyzed on the basis of different skeletal types. The greatest differences were observed in the upper lip region of maxilla and the mental region of mandible. The concave and hypodivergent skull types showed the thickest soft tissue in maxillary region, and the convex and hypedivergent skull types showed the thickest soft tissue in the mental region. This study provided a database for FSTT according to various skeletal types in Chinese female population, and our current studies demonstrated that considering various skeletal types will improve the accuracy of facial reconstruction.

Midsagittal facial soft tissue thickness norms in an adult Mediterranean population

The use of facial soft tissue thickness (FSTT) values is essential in forensic facial approximation. Few studies have assessed the FSTT norms in Mediterranean populations and none in the Lebanese population. The purpose of this study was to (1) present midsagittal facial FSTT norms for Lebanese adults with well-balanced faces and normal occlusion; (2) evaluate the presence of sexual dimorphism within these measurements; (3) establish a potential correlation between these measurements and (4) build on the existing database of FSTT data from previously published studies. FSTT measurements at 10 midsagittal locations were obtained from the lateral cephalometric radiographs of 87 males and 135 females (mean age of 23.49±6.24years). In additional to means, Shorth and 75-Shormax values are presented. Differences between sexes were assessed using the MANOVA test and correlations between different measurements were computed. The thinnest (3.07±0.72mm) and thickest (15.61±2.38mm) craniofacial soft tissue measurements existed at Rhinion and Subnasale, respectively. There was a statistically significant and large effect of sex on the combined FSTT variables (p<0.001; eta-squared=0.393). Males displayed larger FSTT values at all landmarks except at Glabella (p=0.162). Significant correlations were observed between almost all measurements with the highest being between the upper and lower lips (r=0.763) and between Pogonion and Gnathion (r=0.784). The descriptive values of FSTT values reported in this study add to the body of research necessary for the enhancement of facial approximation methods The uniquely strong effects of sex on FSTT measurements combined and on selected single FSTT measurements are an area for further research.

A facial reconstruction method based on new mesh deformation techniques

This article presents a new numerical method for facial reconstruction. The problem is the following: given a dry skull, reconstruct a virtual face that would help in the identification of the subject. The approach combines classical features as the use of a skulls/faces database and more original aspects: (1) an original shape matching method is used to link the unknown skull to the database templates; (2) the final face is seen as an elastic 3D mask that is deformed and adapted onto the unknown skull. In this method, the skull is considered as a whole surface and not restricted to some anatomical landmarks, allowing a dense description of the skull/face relationship. Also, the approach is fully automated. Various results are presented to show its efficiency.

A blind accuracy assessment of computer-modeled forensic facial reconstruction using computed tomography data from live subjects

A computer modeling system for facial reconstruction has been developed that employs a touch-based application to create anatomically accurate facial models focusing on skeletal detail. This article discusses the advantages and disadvantages of the system and illustrates its accuracy and reliability with a blind study using computed tomography (CT) data of living individuals. Three-dimensional models of the skulls of two white North American adults (one male, one female) were imported into the computer system. Facial reconstructions were produced by two practitioners following the Manchester method. Two posters were produced, each including a face pool of five surface model images and the facial reconstruction. The face pool related to the sex, age, and ethnic group of the target individual and included the surface model image of the target individual. Fifty-two volunteers were asked to choose the face from the face pool that most resembled each reconstruction. Both reconstructions received majority percentage hit rates that were at least 50% greater than any other face in the pool. The combined percentage hit rate was 50% above chance (70%). A quantitative comparison of the facial morphology between the facial reconstructions and the CT scan models of the subjects was carried out using Rapidform(™) 2004 PP2-RF4. The majority of the surfaces of the facial reconstructions showed less than 2.5 mm error and 90% of the male face and 75% of the female face showed less than 5 mm error. Many of the differences between the facial reconstructions and the facial scans were probably the result of positional effects caused during the CT scanning procedure, especially on the female subject who had a fatter face than the male subject. The areas of most facial reconstruction error were at the ears and nasal tip.

Is characterizing the digital forensic facial reconstruction with hair necessary? A familiar assessors' analysis

BACKGROUND

In the international scientific literature, there are few studies that emphasize the presence or absence of hair in forensic facial reconstructions. There are neither Brazilian studies concerning digital facial reconstructions without hair, nor research comparing recognition tests between digital facial reconstructions with hair and without hair. The miscegenation of Brazilian people is considerable. Brazilian people, and, in particular, Brazilian women, even if considered as Caucasoid, may present the hair in very different ways: curly, wavy or straight, blonde, red, brown or black, long or short, etc. For this reason, it is difficult to find a correct type of hair for facial reconstruction (unless, in real cases, some hair is recovered with the skeletal remains).

AIMS AND METHODS

This study focuses on the performance of three different digital forensic facial reconstructions, without hair, of a Brazilian female subject (based on one international database and two Brazilian databases for soft facial-tissue thickness) and evaluates the digital forensic facial reconstructions comparing them to photographs of the target individual and nine other subjects, employing the recognition method. A total of 22 assessors participated in the recognition process; all of them were familiar with the 10 individuals who composed the face pool.

RESULTS AND CONCLUSIONS

The target subject was correctly recognized by 41% of the 22 examiners in the International Pattern, by 32% in the Brazilian Magnetic Resonance Pattern and by 32% in the Brazilian Fresh Cadavers Pattern. The facial reconstructions without hair were correctly recognized using the three databases of facial soft-tissue thickness. The observed results were higher than the results obtained using facial reconstructions with hair, from the same skull, which can indicate that it is better to not use hair, at least when there is no information concerning its characteristics.

Clinical application of human adipose tissue-derived mesenchymal stem cells in progressive hemifacial atrophy (Parry-Romberg disease) with microfat grafting techniques using 3-dimensional computed tomography and 3-dimensional camera

BACKGROUND

Parry-Romberg disease is a rare condition that results in progressive hemifacial atrophy, involving the skin, dermis, subcutaneous fat, muscle, and, finally, cartilage and bone. Patients have been treated with dermofat or fat grafts or by microvascular free flap transfer. We hypothesized that adipose-derived stem cells (ASCs) may improve the results of microfat grafting through enhancing angiogenesis. We evaluated the utility of ASC in microfat grafting of patients with Parry-Romberg disease by measuring the change in the hemifacial volumes after injection of ASCs with microfat grafts or microfat grafts alone.

METHODS

In April 2008, this investigation was approved by the Korean Food and Drug Administration and the institutional review board of the Asan Medical Center (Seoul, Korea) that monitor investigator-initiated trials. Between May 2008 and January 2009, 10 volunteers with Parry-Romberg disease (5 men and 5 women; mean age, 28 y) were recruited; 5 received ASC and microfat grafts and 5 received microfat grafts only. The mean follow-up period was 15 months. Adipose-derived stem cells were obtained from abdominal fat by liposuction and were cultured for 2 weeks. On day 14, patients were injected with fat grafts alone or plus (in the test group) 1 × 10 ASCs. Patients were evaluated postoperatively using a 3-dimensional camera and 3-dimensional CT scans, and grafted fat volumes were objectively calculated.

RESULTS

Successful outcomes were evident in all 5 patients receiving microfat grafts and ASCs, and the survival of grafted fat was better than in patients receiving microfat grafts alone. Before surgery, the mean difference between ipsilateral and contralateral hemiface volume in patients receiving microfat grafts and ASCs was 21.71 mL decreasing to 4.47 mL after surgery. Overall resorption in this ASC group was 20.59%. The mean preoperative difference in hemiface volume in those receiving microfat grafts alone was 8.32 mL decreasing to 3.89 mL after surgery. Overall resorption in this group was 46.81%. The preoperative and postoperative volume differences between the groups was statistically significant (P = 0.002; random-effects model [SAS 9.1]).

CONCLUSIONS

Adipose-derived stem cells enhance the survival of fat grafted into the face. A microfat graft with simultaneous ASC injection may be used to treat Parry-Romberg disease without the need for microvascular free flap transfer.

Three-dimensional evaluation of upper anterior alveolar bone dehiscence after incisor retraction and intrusion in adult patients with bimaxillary protrusion malocclusion

OBJECTIVE

The purpose of this study was to evaluate three-dimensional (3D) dehiscence of upper anterior alveolar bone during incisor retraction and intrusion in adult patients with maximum anchorage.

METHODS

Twenty adult patients with bimaxillary dentoalveolar protrusion had the four first premolars extracted. Miniscrews were placed to provide maximum anchorage for upper incisor retraction and intrusion. A computed tomography (CT) scan was performed after placement of the miniscrews and treatment. The 3D reconstructions of pre- and post-CT data were used to assess the dehiscence of upper anterior alveolar bone.

RESULTS

The amounts of upper incisor retraction at the edge and apex were (7.64±1.68) and (3.91±2.10) mm, respectively, and (1.34±0.74) mm of upper central incisor intrusion. Upper alveolar bone height losses at labial alveolar ridge crest (LAC) and palatal alveolar ridge crest (PAC) were 0.543 and 2.612 mm, respectively, and the percentages were (6.49±3.54)% and (27.42±9.77)%, respectively. The shape deformations of LAC-labial cortex bending point (LBP) and PAC-palatal cortex bending point (PBP) were (15.37±5.20)° and (6.43±3.27)°, respectively.

CONCLUSIONS

Thus, for adult patients with bimaxillary protrusion, mechanobiological response of anterior alveolus should be taken into account during incisor retraction and intrusion. Pursuit of maximum anchorage might lead to upper anterior alveolar bone loss.

Midline facial soft tissue thickness database of Turkish population: MRI study

Facial reconstruction is the approximation of an antemortem face from human skeletal remains. Since the nineteenth century, several methods have been developed for reconstruction of the face; all of them require the measurement of average tissue thicknesses at various points on the face. To our knowledge, there are no publications on soft tissue thickness in the Turkish population. In addition, there are few publications on the value of magnetic resonance imaging (MRI) in measuring soft tissue thickness for forensic sciences. The aim of this study was to create a reference database of facial tissue thickness in the Turkish population, and to present data illustrating the successful use of MRI for this purpose. The study included 161 patients (79 males and 82 females) between the ages of 18 and 78 who had undergone brain MRI in our radiology clinic, and showed no sign of maxillofacial pathology. Measurements were taken at 9 points at the midline; glabella, nasion, end of nasals, mid-philtrum, upper lip margin, lower lip margin, chin-lip fold, mental eminence, and beneath chin points. The mean values for these points in the patient sample population were determined, and differences related to age, sex, and body mass index (BMI) were calculated. The values were then compared to the findings of the Manhein study.

An accuracy assessment of forensic computerized facial reconstruction employing cone-beam computed tomography from live subjects

The utilization of 3D computerized systems has allowed more effective procedures for forensic facial reconstruction. Three 3D computerized facial reconstructions were produced using skull models from live adult Korean subjects to assess facial morphology prediction accuracy. The 3D skeletal and facial data were recorded from the subjects in an upright position using a cone-beam CT scanner. Shell-to-shell deviation maps were created using 3D surface comparison software, and the deviation errors between the reconstructed and target faces were measured. Results showed that 54%, 65%, and 77% of the three facial reconstruction surfaces had <2.5 mm of error when compared to the relevant target face. The average error for each reconstruction was -0.46 mm (SD = 2.81) for A, -0.31 mm (SD = 2.40) for B, and -0.49 mm (SD = 2.16) for C. The facial features of the reconstructions demonstrated good levels of accuracy compared to the target faces.

A novel skull registration based on global and local deformations for craniofacial reconstruction

Craniofacial reconstruction is important in forensic identification. It aims to estimate a facial appearance for human skeletal remains using the relationship between the soft tissue and the underlying bone structure. Various computerized methods have been developed in recent decades. An effective way is to deform a reference skull to the discovered skull, and then apply the same deformation to the skin associated with the reference skull to provide an approximate face for the discovered skull. For this method, the better the two skulls match each other, the more face-like the reconstructed skin surface will be. In this paper, we present a novel skull registration method that can match the two skulls closely, so as to improve the accuracy of the reconstruction. It combines both global and local deformations. A generic thin-plate spline (TPS)-based deformation, which is global, is applied first to roughly align the two skulls based on two groups of manually defined landmarks. Afterwards, the two skulls are largely matched, except some regions, on which some new landmarks are automatically marked. A compact support radial basis functions (CSRBF)-based deformation, which is local, will then be performed on these regions to adjust the initial alignment of the two skulls. Such adjustment can be repeatedly implemented until the two skulls have optimal alignment. In addition, all the skulls and face involved in the registration are represented by their single outer surfaces to facilitate the reconstruction procedure. The experiments demonstrate that our method can create a plausible face even when the reference skull is very different from the discovered skull. As a result, we can make full use of our database to provide multiple estimates for a principle components analysis (PCA) for the final reconstruction.

Effective orbital volume and eyeball position: an MRI study

PURPOSE

Previous studies have examined factors affecting the position of the eyeball to the orbit. This study examined the role of effective orbital volume (EOV), defined as the difference between orbital and eyeball volume, as a determinant of eyeball position, using MRI scans.

METHODS

Forty-six patients were recruited from the Department of Ophthalmology of the University Hospital of Heraklion, Crete Greece. Patients with a history of orbital disease were excluded. Distances between eyeball poles and orbital landmarks were measured in T1 weighted transverse, sagittal and coronal orbital images. The protrusion of the eyeball in the sagittal and transverse planes was recorded. The volume of the eyeball and bony orbit, the EOV, the volume of the extraocular muscles as well as clinical information (age, gender, Hertel exophthalmometry) were also recorded.

RESULTS

EOV was significantly associated with orbital volume but not with eyeball volume. EOV was also significantly associated with transverse and sagittal globe protrusions. Females displayed significantly lower orbital and eyeball volumes as well as EOV than males but higher transverse globe protrusion than males.

CONCLUSIONS

Variations in EOV are associated with orbital volume rather than with eyeball volume. EOV is associated with globe protrusion and may be taken into account in the planning of various procedures, including orbital decompression, treatment of enophthalmos or the size of orbital implants following enucleation.

A local technique based on vectorized surfaces for craniofacial reconstruction

In this paper, we focus on the automation of facial reconstruction. Since they consider the whole head as the object of interest, usual reconstruction techniques are global and involve a large number of parameters to be estimated. We present a local technique which aims at reaching a good trade-off between bias and variance following the paradigm of non-parametric statistics. The estimation is localized on patches delimited by surface geodesics between anatomical points of the skull. The technique relies on a continuous representation of the individual surfaces embedded in the vectorial space of extended normal vector fields. This allows to compute deformations and averages of surfaces. It consists in estimating the soft-tissue surface over patches. Using a homogeneous database described in [31], we obtain results on the chin and nasal regions with an average error below 1mm, outperforming the global reconstruction techniques.

Construction and analysis of a head CT-scan database for craniofacial reconstruction

This paper is devoted to the construction of a complete database which is intended to improve the implementation and the evaluation of automated facial reconstruction. This growing database is currently composed of 85 head CT-scans of healthy European subjects aged 20-65 years old. It also includes the triangulated surfaces of the face and the skull of each subject. These surfaces are extracted from CT-scans using an original combination of image-processing techniques which are presented in the paper. Besides, a set of 39 referenced anatomical skull landmarks were located manually on each scan. Using the geometrical information provided by triangulated surfaces, we compute facial soft-tissue depths at each known landmark positions. We report the average thickness values at each landmark and compare our measures to those of the traditional charts of [J. Rhine, C.E. Moore, Facial Tissue Thickness of American Caucasoïds, Maxwell Museum of Anthropology, Albuquerque, New Mexico, 1982] and of several recent in vivo studies [M.H. Manhein, G.A. Listi, R.E. Barsley, et al., In vivo facial tissue depth measurements for children and adults, Journal of Forensic Sciences 45 (1) (2000) 48-60; S. De Greef, P. Claes, D. Vandermeulen, et al., Large-scale in vivo Caucasian facial soft tissue thickness database for craniofacial reconstruction, Forensic Science International 159S (2006) S126-S146; R. Helmer, Schödelidentifizierung durch elektronische bildmischung, Kriminalistik Verlag GmbH, Heidelberg, 1984].

Hand skin reconstruction from skeletal landmarks

Many studies related to three-dimensional facial reconstruction have been previously reported. On the other hand, no extensive work has been found in the literature about hand reconstruction as an identification method. In this paper, the feasibility of virtual reconstruction of hand skin based on (1) its skeleton and (2) another hand skin and skeleton used as template was assessed. One cadaver hand and one volunteer's hand have been used. For the two hands, computer models of the bones and skin were obtained from computerized tomography. A customized software allowed locating spatial coordinates of bony anatomical landmarks on the models. From these landmarks, the spatial relationships between the models were determined and used to interpolate the missing hand skin. The volume of the interpolated skin was compared to the real skin obtained from medical imaging for validation. Results seem to indicate that such a method is of interest to give forensic investigators morphological clues related to an individual hand skin based on its skeleton. Further work is in progress to finalize the method.

Assessment of the accuracy of three-dimensional manual craniofacial reconstruction: a series of 25 controlled cases

The aim of this work was to estimate the accuracy of craniofacial reconstruction (CFR), from a series of 25 controlled cases. Three protocols of blind CFRs (exhibiting an increasing complexity from A to C) were assessed in this paper, allowing comparison of the CFR with the actual face of the deceased. The whole results showed that an excellent, or good, to middle resemblance (between the blind CFR and the actual face of the subject) was reached in 9 out of 25 cases, but the success gradually increased from the A to the C protocol of CFR, reaching six cases out of eight in the latter. Statistical comparison of measurements (between the blind CFR and the actual face) was also achieved, revealing that some anthropological distances were constantly underestimated or overestimated. This experiment shows that a thorough anthropological, odontological, and X-ray analysis is indispensable before performing a CFR, and these encouraging results justify further efforts of research in this field.

Computerized craniofacial reconstruction using CT-derived implicit surface representations

In forensic craniofacial reconstruction, facial features of an unknown individual are estimated from an unidentified skull, based on a mixture of experimentally obtained guidelines on the relationship between soft tissues and the underlying skeleton. In this paper, we investigate the possibility of using full 3D cross-sectional CT images for establishing a reference database of densely sampled distances between the external surfaces of the skull and head for automated craniofacial reconstruction. For each CT image in the reference database, the hard tissue (skull) and soft tissue (head) volumes are automatically segmented and transformed into signed distance transform (sDT) images, representing for each voxel in this image the Euclidean distance to the closest point on the skull and head surface, respectively, distances being positive (negative) for voxels inside (outside) the skull/head. Multiple craniofacial reconstructions are obtained by first warping each reference skull sDT maps to the target skull sDT using a B-spline based free form deformation algorithm and subsequently applying these warps to the reference head sDT maps. A single reconstruction of the target head surface is defined as the zero level set of the arithmetic average of all warped reference head sDT maps, but other reconstructions are possible, biasing the result to subject specific attributes (age, BMI, gender). Both qualitative and quantitative tests (measuring the similarity between the 3D reconstructed and corresponding original head surface) on a small (N = 20) database are presented to proof the validity of the concept.

Large-scale in-vivo Caucasian facial soft tissue thickness database for craniofacial reconstruction

A large-scale study of facial soft tissue depths of Caucasian adults was conducted. Over a 2-years period, 967 Caucasian subjects of both sexes, varying age and varying body mass index (BMI) were studied. A user-friendly and mobile ultrasound-based system was used to measure, in about 20min per subject, the soft tissue thickness at 52 facial landmarks including most of the landmarks used in previous studies. This system was previously validated on repeatability and accuracy [S. De Greef, P. Claes, W. Mollemans, M. Loubele, D. Vandermeulen, P. Suetens, G. Willems, Semi-automated ultrasound facial soft tissue depth registration: method and validation. J. Forensic Sci. 50 (2005)]. The data of 510 women and 457 men were analyzed in order to update facial soft tissue depth charts of the contemporary Caucasian adult. Tables with the average thickness values for each landmark as well as the standard deviation and range, tabulated according to gender, age and BMI are reported. In addition, for each landmark and for both sexes separately, a multiple linear regression of thickness versus age and BMI is calculated. The lateral asymmetry of the face was analysed on an initial subset of 588 subjects showing negligible differences and thus warranting the unilateral measurements of the remaining subjects. The new dataset was statistically compared to three datasets for the Caucasian adults: the traditional datasets of Rhine and Moore [J.S. Rhine, C.E. Moore, Tables of facial tissue thickness of American Caucasoids in forensic anthropology. Maxwell Museum Technical series 1 (1984)] and Helmer [R. Helmer, Schädelidentifizierung durch elektronische bildmischung, Kriminalistik Verlag GmbH, Heidelberg, 1984] together with the most recent in vivo study by Manhein et al. [M.H. Manhein, G.A. Listi, R.E. Barsley, R. Musselman, N.E. Barrow, D.H. Ubelbaker, In vivo facial tissue depth measurements for children and adults. J. Forensic Sci. 45 (2000) 48-60]. The large-scale database presented in this paper offers a denser sampling of the facial soft tissue depths of a more representative subset of the actual Caucasian population over the different age and body posture subcategories. This database can be used as an updated chart for manual and computer-based craniofacial approximation and allows more refined analyses of the possible factors affecting facial soft tissue depth.

Craniofacial reconstruction using a combined statistical model of face shape and soft tissue depths: methodology and validation

Forensic facial reconstruction aims at estimating the facial outlook associated with an unidentified skull specimen. Estimation is generally based on tabulated average values of soft tissue thicknesses measured at a sparse set of landmarks on the skull. Traditional 'plastic' methods apply modeling clay or plasticine on a cast of the skull, approximating the estimated tissue depths at the landmarks and interpolating in between. Current computerized techniques mimic this landmark interpolation procedure using a single static facial surface template. However, the resulting reconstruction is biased by the specific choice of the template and no face-specific regularization is used during the interpolation process. We reduce the template bias by using a flexible statistical model of a dense set of facial surface points, combined with an associated sparse set of skull-based landmarks. This statistical model is constructed from a facial database of (N = 118) individuals and limits the reconstructions to statistically plausible outlooks. The actual reconstruction is obtained by fitting the skull-based landmarks of the template model to the corresponding landmarks indicated on a digital copy of the skull to be reconstructed. The fitting process changes the face-specific statistical model parameters in a regularized way and interpolates the remaining landmark fit error using a minimal bending thin-plate spline (TPS)-based deformation. Furthermore, estimated properties of the skull specimen (BMI, age and gender, e.g.) can be incorporated as conditions on the reconstruction by removing property-related shape variation from the statistical model description before the fitting process. The proposed statistical method is validated, both in terms of accuracy and identification success rate, based on leave-one-out cross-validation tests applied on the facial database. Accuracy results are obtained by statistically analyzing the local 3D facial surface differences of the reconstructions and their corresponding ground truth. Identification success rate is obtained by comparing, based on correlation, Euclidean distance matrix (EDM) signatures of the reconstructed and the original 3D facial surfaces in the database. A subjective identification success rate is quantified based on face-pool tests. Finally a qualitative comparison is made between facial reconstructions of a real-case skull, based on two typical static face models and our statistical model, showing the shortcomings of current face models and the improved performance of the statistical model.

A New Experimental Approach to Computer-Aided Face/Skull Identification in Forensic Anthropology

The present study introduces a new approach to computer-assisted face/skull matching used for personal identification purposes in forensic anthropology. In this experiment, the authors formulated an algorithm able to identify the face of a person suspected to have disappeared, by comparing the respective person's facial image with the skull radiograph. A total of 14 subjects were selected for the study, from which a facial photograph and skull radiograph were taken and ultimately compiled into a database, saved to the hard drive of a computer. The photographs of the faces and corresponding skull radiographs were then drafted using common photographic software, taking caution not to alter the informational content of the images. Once computer generated, the facial images and menu were displayed on a color monitor. In the first phase, a few anatomic points of each photograph were selected and marked with a cross to facilitate and more accurately match the face with its corresponding skull. In the second phase, the above mentioned cross grid was superimposed on the radiographic image of the skull and brought to scale. In the third phase, the crosses were transferred to the cranial points of the radiograph. In the fourth phase, the algorithm calculated the distance of each transferred cross and the corresponding average. The smaller the mean value, the greater the index of similarity between the face and skull.A total of 196 cross-comparisons were conducted, with positive identification resulting in each case. Hence, the algorithm matched a facial photograph to the correct skull in 100% of the cases.

A novel method of automated skull registration for forensic facial approximation

Modern forensic facial reconstruction techniques are based on an understanding of skeletal variation and tissue depths. These techniques rely upon a skilled practitioner interpreting limited data. To (i) increase the amount of data available and (ii) lessen the subjective interpretation, we use medical imaging and statistical techniques. We introduce a software tool, reality enhancement/facial approximation by computational estimation (RE/FACE) for computer-based forensic facial reconstruction. The tool applies innovative computer-based techniques to a database of human head computed tomography (CT) scans in order to derive a statistical approximation of the soft tissue structure of a questioned skull. A core component of this tool is an algorithm for removing the variation in facial structure due to skeletal variation. This method uses models derived from the CT scans and does not require manual measurement or placement of landmarks. It does not require tissue-depth tables, can be tailored to specific racial categories by adding CT scans, and removes much of the subjectivity of manual reconstructions.

Facial soft tissue thickness in Japanese female children

Facial reconstruction techniques used in forensic anthropology are based on soft tissue thickness measurements. Many studies of facial tissue thickness in adults have been published that take racial background into account. However, the only data on facial thickness in children are derived from studies of American, British, and Hispanic children. The authors therefore measured facial tissue thickness in Japanese children, with the aim of providing data for producing accurate facial likenesses and to evaluate matching of skull-photo superimposition images. Cephalometric X-ray images give an approximately 10% enlargement from true size and can demonstrate the relationship between soft and hard tissue. Facial soft tissue thickness was measured at 12 anthropological points using X-ray cephalometry.

Anthropological facial ‘reconstruction’ – recognizing the fallacies, ‘unembracing’ the errors, and realizing method limits

Despite being practiced for over the last 200 years, facial approximation methods remain in their infancy as the soft tissue prediction methods employed have not been tested and justified. Scientific testing is the only way forward and much of it is needed. The lack of systematic scientific tests in the past has enabled many misleading notions to become established. Many of these notions appear to have arisen and been sustained as a result of practitioner biases--this is clearly evident even in the name commonly used to describe the method of building faces from skulls, for "facial reconstruction" implies everything the method is not, e.g., technical/scientific, exact, and credible. Although facial approximation methods are useful for forensic investigation (even if they do not generate identifications through true positive recognitions of the faces), the public should beware of the marketing and political ploys employed within the profession. These ploys give rise to some impressive, but unjustifiable claims--but do not just take my word for it; evaluate the evidence for yourself with disregard to the indoctrination waged by the facial "reconstruction" field in general, including that promoted by what I have had to say here. Use your own reason and intellect and see which conclusions you reach.