Background Complex bilateral midface fractures necessitate a surgically challenging procedure to ... more Background Complex bilateral midface fractures necessitate a surgically challenging procedure to preserve or restore the occlusion and the sensitive eye area. In this case control study, we aim to show the potential of a statistical shape model (SSM) for measuring the quality of the midface reconstruction, compared to the estimated preoperative situation. Methods An individualized SSM was postoperatively registered on 19 reconstructed complex bilateral midface fractures. Using this SSM, the distances from the simulated preoperative situation to the postoperative positions of the fracture segments were calculated. The fracture lines for Le Fort II, Le Fort III, and NOE fractures were chosen as reference points for the distance measurements. Results The SSM could be registered on all 19 complex bilateral midface fractures. All analyzed fractures show a dorsal impaction (negative values) of the midface. Le Fort II fractures show deviation values of − 0.98 ± 4.6 mm, Le Fort III fractures show values of − 3.68 ± 3.6 mm, NOE type 2 fractures show values of − 0.25 ± 4.6 mm, and NOE type 1 fractures show values of − 0.25 ± 4.6 mm. Conclusion The SSM can be used to measure the quality of the achieved reduction of complex bilateral midface fractures based on the estimated preoperative situation. Trial registration DRKS00009719
PurposeMorphological variability of the skull is an important consideration for cranioplasty and ... more PurposeMorphological variability of the skull is an important consideration for cranioplasty and implant design. Differences in morphology of the skull based on the ethnicity are known. In a previous study we could show the accuracy and benefits of virtual reconstructions based on a statistical shape model (SSM) for neurocranial defects. As the SSM is trained on European data, the question arises how well this model fares when dealing with patients with a different ethnic background. In this study we aim to evaluate the accuracy and applicability of our proposed method when deploying a cranial SSM generated from European data to estimate missing parts of the neurocranium in a Chinese population.MethodsWe used the same data and methods as in our previous study and compared the outcomes when applied to Chinese individuals. A large unilateral defect on the right side and a bilateral defect were created. The outer surface of the cranial table was reconstructed from CT scans, meshed with triangular elements, and registered to a template. Principal component analysis together with Thin Plate Spines (TPS) deformation was applied to quantify modes of variation. The mesh to mesh distances between the original defects´ surfaces and the reconstructed surface were computed.ResultsComparing the Chinese test group with the European control group, regarding the entire defect the analysis shows no significant difference for unilateral defects (test vs. control group/0.46 mm ± vs. 0.44 mm). Reconstruction of bilateral defects exhibited only in slightly higher prediction errors than those of unilateral defects (0.49 mm ± vs. 0.45 mm).ConclusionThe proposed method shows a high accuracy that seems to be ethnical independent - with low error margins for virtual skull reconstruction and implant design.Clinical relevance: Metallic objects may severely impact image quality in several CBCT devices.
Journal of Cosmetic and Laser Therapy, May 16, 2017
Background: Facial rejuvenation is an expanding field with an increasing number of treatment moda... more Background: Facial rejuvenation is an expanding field with an increasing number of treatment modalities. Several non-autologous filler materials are available for soft tissue augmentation. Calcium hydroxylapatite (CaOH) is aimed at increasing collagen neosynthesis and thereby producing long-term augmentation effects. Despite a multitude of observational reports, the field is suffering from lack of quantitative morphometric evaluation methods. Objective: The objective of this proof-of-principle study was to investigate whether the effects of facial tissue augmentation with CaOH (RADIESSE™) can be quantified and followed up using 3D surface scanning. Methods: 3 female subjects received augmentation of the mid and lower face with CaOH. The faces were recorded prior, directly after, and two weeks and six months after the injection using standardized photos and 3D scanning. Computational analysis allowed quantifying the change in volume and displacement of the facial surface. Additionally, a patient satisfaction questionnaire was administered. Results: In all subjects, increase in facial volume could be quantified and was present after two weeks and six months. Conclusions: 3D surface scanning is an adequate tool for objective quantification of changes after facial augmentation with filler materials. Persistent volume augmentation after CaOH injections could be quantified after two weeks and six months. Evidence level: IV.
Abstract The mathematical/statistical software platform R has seen an immense increase in popular... more Abstract The mathematical/statistical software platform R has seen an immense increase in popularity within the last decade. Its main advantages are its flexibility, a large repository of freely available extensions, its open-source nature and a thriving community. This tutorial gives an introduction into landmark/surface-mesh based statistical shape analysis in R – specifically using the packages Morpho and Rvcg. Beginning with examples based on sparse sets of anatomical landmarks, the tutorial will go on dealing with surface and curve landmarks and more challenging tasks such as mesh manipulations and surface registration. Apart from statistical analyses, emphasis will also be put on comprehensive visualization of the results. Extensive examples and code snippets are provided to allow the reader to easily replicate the analyses.
The 84th Annual Meeting of the American Association of Physical Anthropologists, St. Louis, MO, 2015
ABSTRACT In Physical Anthropology, an increasing number of studies relies on large amounts of dat... more ABSTRACT In Physical Anthropology, an increasing number of studies relies on large amounts of data. Standards and software tools for structured data collection are being developed. As a consequence, volumes of digital data accumulate on various systems, but pooling these sources remains complicated and time-consuming. We propose a digital standard for the representation of research data from human skeletal remains, enabling a free exchange between different types of data storage systems. Our aim is to enable institutions holding skeletal collections to curate related data and to make it available for future research. Our standard is defined as an ontology that represents data as a network of relations between objects and properties, rather than a relational set of tables. It is developed within the Resource Description Framework (RDF) as an integral part of technologies related to the semantic web. In practice, it facilitates data collection and recording of results. Additionally, it serves as an interoperability layer between existing collection management systems, skeletal documentation software and research data bases. The ontology is extensible, implementing existing data collection standards and allowing researchers to extend these to fit their specific research objectives. This approach reconciles the collections' interest to build up consistent stocks of data and the ambition of researchers to open up new areas of research and methodology. Here we present the ontology, which will be implemented in a server-based data base application. It is developed in collaboration with established skeletal collections and will be released for free under a permissive Open Source license.
BACKGROUND Botulinum toxin treatment for forehead wrinkles has been extensively studied and found... more BACKGROUND Botulinum toxin treatment for forehead wrinkles has been extensively studied and found to be a safe and reproducible procedure. However, the effect on the position of the eyebrows, which relies on the dynamic positioning of the treated muscles, has received less attention and has not been studied with 3-dimensional (3D) technology. OBJECTIVES The authors sought to evaluate the changes of eyebrow position after standardized botulinum toxin treatment of glabella or glabella and frontalis muscles with 3D imaging. METHODS In a prospective study, 2 groups of adult females were treated with botulinum toxin A at the glabella only (G) or at the glabella and the frontalis muscle (F/G). The brow position was measured at 5 positions with 3D photography before injection and 2 weeks, 3 months, and 6 months after injection. Results were statistically analyzed and related to patient age. RESULTS In the F/G group, the brow descended significantly almost across the whole brow length after 2 weeks. The descent lessened after 3 months and moved medially. No clear trend was evident in the G group. There was no significant change attributed to patient age in both groups. CONCLUSIONS Botulinum toxin treatment of the glabella and frontalis muscle impacts the position and configuration of the eyebrow. The degree of change is affected by the amount of frontalis weakening rather than by treatment of the glabella. While age in general is not a reliable predictor, individual factors play the major role in how pronounced a change of the brow can be expected. LEVEL OF EVIDENCE: 2
Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, Dec 21, 2016
The human zygomatic structure, consisting of the zygomatic bone and the zygomatic process of the ... more The human zygomatic structure, consisting of the zygomatic bone and the zygomatic process of the temporal bone, is an essential part of the masticatory apparatus and has been shown to reflect population history and sexual dimorphism to varying degrees. In this study, we analyzed the predictive value of the outlines vs. the complete surface shape of the zygomatic bone in a sample of 98 Chinese (50 $, 48 #) and 96 Germans (49 $, 47 #). We first applied a surface registration process based on statistical shape modeling. A dense set of 1,480 pseudo-landmarks was then sampled automatically from the surface of the pooled mean shape and three curves were digitized manually along the outlines of the zygomatic bone. Both sets of pseudo-landmarks were automatically transferred to all specimens. Analysis of sex and population affinity showed both factors to be independently significant, but the interaction between them was not. Population affinity could be predicted quite accurately with correct classification of 97.9% using the surface data and 93.3% with the curve data. Sexual dimorphism was less distinct with 89.2% correct sex determination when using surface information compared with 77.8% when using the curve data. Population-related shape differences were captured primarily in the outlines, while sexual dimorphism is distributed more uniformly throughout the entire surface of the zygomatic structure.
Several important algorithms for machine learning and data analysis use pairwise distances as inp... more Several important algorithms for machine learning and data analysis use pairwise distances as input. On Riemannian manifolds these distances may be prohibitively costly to compute, in particular for large datasets. To tackle this problem, we propose a distance approximation which requires only a linear number of geodesic boundary value problems to be solved. The approximation is constructed by fitting a two-dimensional model space with constant curvature to each pair of samples. We demonstrate the usefulness of our approach in the context of shape analysis on landmarks spaces.
Intentional cranial deformations (ICD) were obtained by exerting external mechanical constraints ... more Intentional cranial deformations (ICD) were obtained by exerting external mechanical constraints on the skull vault during the first years of life to permanently modify head shape. The repercussions of ICD on the face are not well described in the midfacial region. Here we assessed the shape of the zygomatic bone in different types of ICDs. We considered 14 non-deformed skulls, 19 skulls with antero-posterior deformation, nine skulls with circumferential deformation and seven skulls with Toulouse deformation. The shape of the zygomatic bone was assessed using a statistical shape model after mesh registration. Euclidian distances between mean models and Mahalanobis distances after canonical variate analysis were computed. Classification accuracy was computed using a cross-validation approach. Different ICDs cause specific zygomatic shape modifications corresponding to different degrees of retrusion but the shape of the zygomatic bone alone is not a sufficient parameter for classifying populations into ICD groups defined by deformation types. We illustrate the fact that external mechanical constraints on the skull vault influence midfacial growth. ICDs are a model for the study of the influence of epigenetic factors on craniofacial growth and can help to understand the facial effects of congenital skull malformations such as single or multi-suture synostoses, or of external orthopedic devices such as helmets used to correct deformational plagiocephaly.
ABSTRACT Forensic cases where corpses remain unidentified, call for cranio-facial reconstructions... more ABSTRACT Forensic cases where corpses remain unidentified, call for cranio-facial reconstructions (CFR) to provide the media with material that might trigger recognition among those that used to be acquainted with the deceased. The task of reconstructing the face from the skull is usually done by an expert based on her/his knowledge and understanding of the correspondences between facial soft-tissue and the underlying skull. Reconstructions by different specialist often vary strongly in their outcomes. In response to this, various approaches towards computer-based CFR have been developed during the last tow decades, aiming at making the reconstructions less observer-dependent.. Additionally, computer based reconstructions are easily and fast altered and adapted by changing parameters such as age, gender or population affiliation, while manual CFRs are work- and time-consuming. Why is it necessary to analyse the nasal area separately? One of the major prerequisites for computer-driven CFRs are databases containing information about soft- and hard-tissue. A large repository of this data are hospitals, where medical 3D-imaging produces large amounts of three-dimensional representations of human heads. In order to minimise both unnecessary irradiation and costs, these scans are restricted to areas affected by pathologies. Creating separate databases for specific areas of the head allows for compiling larger amounts of data. As a result much larger databases can be obtained. The separate approach also helps to deal with another problem: while the osseous substructure of the nasal area is a relatively small part of the skull, the soft- tissue nose is a very prominent feature of the human face. This discrepancy might lead to larger prediction errors within this area, by methods estimating the facial surface as a whole. The development of a nose-specific procedure can solve these two problems, as a larger database can improve prediction results, and concentration on a specific sub-structure might reveal connections that are underrated in reconstructions based on global similarity measures. This dissertation provides solutions to the problem of predicting nasal soft- tissue shape, based on the shape of the underlying bone age, population affiliation and sex. To accomplish this, it has to be dealt with data acquisition as well as with problems concerning registration of 3D-structures. The main directive is to find the statistical interrelationship between soft-tissue and hard-tissue. This implies the need for a large database for building statistical models, estimating the most probable soft-tissue shape, based on the known hard-tissue information (and the additional attributes).
Images in paleoanthropology are of persuasive power, since they try to illuminate ancient life wh... more Images in paleoanthropology are of persuasive power, since they try to illuminate ancient life which is not otherwise visually documented. The scientific community, as well as public media and museums, aim to establish a window into the past in part through visualization of scenarios from prehistoric life and environments. The role of human ancestors in these settings is captured by body and especially facial reconstructions, which comparatively easily attract attention among nonscientific audiences and therefore raise public understanding of a complex field of research, allowing it to compete successfully with other, at times more tangible scientific subjects. Within the scientific community itself, reconstructions of early hominids play only a limited role, merely supplementing a whole range of field and laboratory research, evolutionary hypotheses, and the analysis of empirical data. Paleoanthropologists and paleontologists are aware of the interpretative character of facial reconstructions that go beyond the limited set of primary facts documented in the fossils themselves. The visual approach to paleoanthropology has changed strongly over time, varies with the media used, and depends on how we imagine our ancestors in coeval context. On the one hand, evolutionary theories and contemporary social ideas are influencing and shaping how we view and depict our ancestors. On the other hand, hominid reconstructions themselves, in turn, can influence our view and the underlying ideas. This chapter reflects on the development of facial reconstructions over time, along with influences such as the development of methods and techniques – from drawings to manual modeling to virtual 3D reconstructions. For exemplification, special emphasis will be put on Neanderthal reconstructions, as these are linked both to early attempts at facial reconstruction and to the subsequent methodological development of reconstruction techniques during the twentieth century. Starting with the first hominid fossils found, we trace the “evolution” of facial reconstructions of Neanderthals, in order to highlight contemporary perceptions and limiting factors in the visualization of our ancestors.
A fundamental impediment to the adoption of digital standards in physical anthropology is the vas... more A fundamental impediment to the adoption of digital standards in physical anthropology is the vast diversity of this area of research. Even within osteology, many investigations require some modification of existing standards to suit their specific study designs. This might be a reason for researchers not to use database software based exclusively on one particular standard. It also makes it difficult to keep track of research data compatibility and to process data from different investigations in one database system. Up to now, comprehensive and monolithic data standards have failed to address these issues. We propose a different approach, concentrating on the exact definition of individual data items. These are the building blocks researchers can use to describe the various aspects of their research, like skeletal inventories, research methods and work flows, resulting data and their processing employing mathematical transformations or textual conclusions. Because the building blocks of these descriptions are defined beforehand, the degree of compatibility between different investigations becomes evident. Our data standard, RDFBones, is an RDF (Resource Description Framework) ontology, containing a number of classes and properties for describing anthropological research and materials. Individual researchers can use these elements to define their methodology. That way, RDFBones helps to build standards, instead of prescribing them. Once a standard is formulated, however, it can be published and shared otherwise, supporting uniform methodology. RDFBones also creates a perfect means for sustained long-term data storage.
Genetic and climate-driven estimates of past population dynamics are increasingly influential in ... more Genetic and climate-driven estimates of past population dynamics are increasingly influential in broader models of hominin migration and adaptation, yet the contribution of stone artifact variability remains more contentious. Scientists are increasingly recognizing the potential of unretouched stone flakes ('flakes') in exploring existing models of hominin behavioral evolution. This is because flakes (1) were produced by all stone tool manufacturing groups in the past, (2) are abundant from the inception of the archaeological record up into the ethnographic present, and (3) preserve under most conditions. The statistical tools of 3D geometric morphometrics capture detailed approximations of flake form that are challenging to document with conventional artifact analyses. We analyze a collection of 717 3D scans of experimentally produced flakes from 5 production strategies that were practiced by hominins through large parts of the Pleistocene and that scientists have drawn on also to make demographic arguments about past human behavior (n ¼ 45 reduction sequences, n ¼ 3 knappers naive toward the study objectives). First, as a proof of concept, we demonstrate that we can estimate the strategies used to produce these flakes at a high success rate even when flakes from early stages of core reduction are included. We frame the significance of this finding against archaeological classifications from several key Middle Paleolithic assemblages in France (n ¼ 4 sites, n ¼ 28 layers, n ¼ 16,467 flakes). Second, we show that 3D geometric morphometrics captures subtle differences in these strategies that influence flake formation on a flake-by-flake basis and that reflect decisions made by knappers about platform selection, preparation, and core-surface management. We explore the broader potential of our model with a crossvalidation approach, and we describe a means of assessing flake form on a continuum wherein variability among assemblages separated by large expanses of space and time can be meaningfully explored.
Background Complex bilateral midface fractures necessitate a surgically challenging procedure to ... more Background Complex bilateral midface fractures necessitate a surgically challenging procedure to preserve or restore the occlusion and the sensitive eye area. In this case control study, we aim to show the potential of a statistical shape model (SSM) for measuring the quality of the midface reconstruction, compared to the estimated preoperative situation. Methods An individualized SSM was postoperatively registered on 19 reconstructed complex bilateral midface fractures. Using this SSM, the distances from the simulated preoperative situation to the postoperative positions of the fracture segments were calculated. The fracture lines for Le Fort II, Le Fort III, and NOE fractures were chosen as reference points for the distance measurements. Results The SSM could be registered on all 19 complex bilateral midface fractures. All analyzed fractures show a dorsal impaction (negative values) of the midface. Le Fort II fractures show deviation values of − 0.98 ± 4.6 mm, Le Fort III fractures show values of − 3.68 ± 3.6 mm, NOE type 2 fractures show values of − 0.25 ± 4.6 mm, and NOE type 1 fractures show values of − 0.25 ± 4.6 mm. Conclusion The SSM can be used to measure the quality of the achieved reduction of complex bilateral midface fractures based on the estimated preoperative situation. Trial registration DRKS00009719
PurposeMorphological variability of the skull is an important consideration for cranioplasty and ... more PurposeMorphological variability of the skull is an important consideration for cranioplasty and implant design. Differences in morphology of the skull based on the ethnicity are known. In a previous study we could show the accuracy and benefits of virtual reconstructions based on a statistical shape model (SSM) for neurocranial defects. As the SSM is trained on European data, the question arises how well this model fares when dealing with patients with a different ethnic background. In this study we aim to evaluate the accuracy and applicability of our proposed method when deploying a cranial SSM generated from European data to estimate missing parts of the neurocranium in a Chinese population.MethodsWe used the same data and methods as in our previous study and compared the outcomes when applied to Chinese individuals. A large unilateral defect on the right side and a bilateral defect were created. The outer surface of the cranial table was reconstructed from CT scans, meshed with triangular elements, and registered to a template. Principal component analysis together with Thin Plate Spines (TPS) deformation was applied to quantify modes of variation. The mesh to mesh distances between the original defects´ surfaces and the reconstructed surface were computed.ResultsComparing the Chinese test group with the European control group, regarding the entire defect the analysis shows no significant difference for unilateral defects (test vs. control group/0.46 mm ± vs. 0.44 mm). Reconstruction of bilateral defects exhibited only in slightly higher prediction errors than those of unilateral defects (0.49 mm ± vs. 0.45 mm).ConclusionThe proposed method shows a high accuracy that seems to be ethnical independent - with low error margins for virtual skull reconstruction and implant design.Clinical relevance: Metallic objects may severely impact image quality in several CBCT devices.
Journal of Cosmetic and Laser Therapy, May 16, 2017
Background: Facial rejuvenation is an expanding field with an increasing number of treatment moda... more Background: Facial rejuvenation is an expanding field with an increasing number of treatment modalities. Several non-autologous filler materials are available for soft tissue augmentation. Calcium hydroxylapatite (CaOH) is aimed at increasing collagen neosynthesis and thereby producing long-term augmentation effects. Despite a multitude of observational reports, the field is suffering from lack of quantitative morphometric evaluation methods. Objective: The objective of this proof-of-principle study was to investigate whether the effects of facial tissue augmentation with CaOH (RADIESSE™) can be quantified and followed up using 3D surface scanning. Methods: 3 female subjects received augmentation of the mid and lower face with CaOH. The faces were recorded prior, directly after, and two weeks and six months after the injection using standardized photos and 3D scanning. Computational analysis allowed quantifying the change in volume and displacement of the facial surface. Additionally, a patient satisfaction questionnaire was administered. Results: In all subjects, increase in facial volume could be quantified and was present after two weeks and six months. Conclusions: 3D surface scanning is an adequate tool for objective quantification of changes after facial augmentation with filler materials. Persistent volume augmentation after CaOH injections could be quantified after two weeks and six months. Evidence level: IV.
Abstract The mathematical/statistical software platform R has seen an immense increase in popular... more Abstract The mathematical/statistical software platform R has seen an immense increase in popularity within the last decade. Its main advantages are its flexibility, a large repository of freely available extensions, its open-source nature and a thriving community. This tutorial gives an introduction into landmark/surface-mesh based statistical shape analysis in R – specifically using the packages Morpho and Rvcg. Beginning with examples based on sparse sets of anatomical landmarks, the tutorial will go on dealing with surface and curve landmarks and more challenging tasks such as mesh manipulations and surface registration. Apart from statistical analyses, emphasis will also be put on comprehensive visualization of the results. Extensive examples and code snippets are provided to allow the reader to easily replicate the analyses.
The 84th Annual Meeting of the American Association of Physical Anthropologists, St. Louis, MO, 2015
ABSTRACT In Physical Anthropology, an increasing number of studies relies on large amounts of dat... more ABSTRACT In Physical Anthropology, an increasing number of studies relies on large amounts of data. Standards and software tools for structured data collection are being developed. As a consequence, volumes of digital data accumulate on various systems, but pooling these sources remains complicated and time-consuming. We propose a digital standard for the representation of research data from human skeletal remains, enabling a free exchange between different types of data storage systems. Our aim is to enable institutions holding skeletal collections to curate related data and to make it available for future research. Our standard is defined as an ontology that represents data as a network of relations between objects and properties, rather than a relational set of tables. It is developed within the Resource Description Framework (RDF) as an integral part of technologies related to the semantic web. In practice, it facilitates data collection and recording of results. Additionally, it serves as an interoperability layer between existing collection management systems, skeletal documentation software and research data bases. The ontology is extensible, implementing existing data collection standards and allowing researchers to extend these to fit their specific research objectives. This approach reconciles the collections' interest to build up consistent stocks of data and the ambition of researchers to open up new areas of research and methodology. Here we present the ontology, which will be implemented in a server-based data base application. It is developed in collaboration with established skeletal collections and will be released for free under a permissive Open Source license.
BACKGROUND Botulinum toxin treatment for forehead wrinkles has been extensively studied and found... more BACKGROUND Botulinum toxin treatment for forehead wrinkles has been extensively studied and found to be a safe and reproducible procedure. However, the effect on the position of the eyebrows, which relies on the dynamic positioning of the treated muscles, has received less attention and has not been studied with 3-dimensional (3D) technology. OBJECTIVES The authors sought to evaluate the changes of eyebrow position after standardized botulinum toxin treatment of glabella or glabella and frontalis muscles with 3D imaging. METHODS In a prospective study, 2 groups of adult females were treated with botulinum toxin A at the glabella only (G) or at the glabella and the frontalis muscle (F/G). The brow position was measured at 5 positions with 3D photography before injection and 2 weeks, 3 months, and 6 months after injection. Results were statistically analyzed and related to patient age. RESULTS In the F/G group, the brow descended significantly almost across the whole brow length after 2 weeks. The descent lessened after 3 months and moved medially. No clear trend was evident in the G group. There was no significant change attributed to patient age in both groups. CONCLUSIONS Botulinum toxin treatment of the glabella and frontalis muscle impacts the position and configuration of the eyebrow. The degree of change is affected by the amount of frontalis weakening rather than by treatment of the glabella. While age in general is not a reliable predictor, individual factors play the major role in how pronounced a change of the brow can be expected. LEVEL OF EVIDENCE: 2
Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, Dec 21, 2016
The human zygomatic structure, consisting of the zygomatic bone and the zygomatic process of the ... more The human zygomatic structure, consisting of the zygomatic bone and the zygomatic process of the temporal bone, is an essential part of the masticatory apparatus and has been shown to reflect population history and sexual dimorphism to varying degrees. In this study, we analyzed the predictive value of the outlines vs. the complete surface shape of the zygomatic bone in a sample of 98 Chinese (50 $, 48 #) and 96 Germans (49 $, 47 #). We first applied a surface registration process based on statistical shape modeling. A dense set of 1,480 pseudo-landmarks was then sampled automatically from the surface of the pooled mean shape and three curves were digitized manually along the outlines of the zygomatic bone. Both sets of pseudo-landmarks were automatically transferred to all specimens. Analysis of sex and population affinity showed both factors to be independently significant, but the interaction between them was not. Population affinity could be predicted quite accurately with correct classification of 97.9% using the surface data and 93.3% with the curve data. Sexual dimorphism was less distinct with 89.2% correct sex determination when using surface information compared with 77.8% when using the curve data. Population-related shape differences were captured primarily in the outlines, while sexual dimorphism is distributed more uniformly throughout the entire surface of the zygomatic structure.
Several important algorithms for machine learning and data analysis use pairwise distances as inp... more Several important algorithms for machine learning and data analysis use pairwise distances as input. On Riemannian manifolds these distances may be prohibitively costly to compute, in particular for large datasets. To tackle this problem, we propose a distance approximation which requires only a linear number of geodesic boundary value problems to be solved. The approximation is constructed by fitting a two-dimensional model space with constant curvature to each pair of samples. We demonstrate the usefulness of our approach in the context of shape analysis on landmarks spaces.
Intentional cranial deformations (ICD) were obtained by exerting external mechanical constraints ... more Intentional cranial deformations (ICD) were obtained by exerting external mechanical constraints on the skull vault during the first years of life to permanently modify head shape. The repercussions of ICD on the face are not well described in the midfacial region. Here we assessed the shape of the zygomatic bone in different types of ICDs. We considered 14 non-deformed skulls, 19 skulls with antero-posterior deformation, nine skulls with circumferential deformation and seven skulls with Toulouse deformation. The shape of the zygomatic bone was assessed using a statistical shape model after mesh registration. Euclidian distances between mean models and Mahalanobis distances after canonical variate analysis were computed. Classification accuracy was computed using a cross-validation approach. Different ICDs cause specific zygomatic shape modifications corresponding to different degrees of retrusion but the shape of the zygomatic bone alone is not a sufficient parameter for classifying populations into ICD groups defined by deformation types. We illustrate the fact that external mechanical constraints on the skull vault influence midfacial growth. ICDs are a model for the study of the influence of epigenetic factors on craniofacial growth and can help to understand the facial effects of congenital skull malformations such as single or multi-suture synostoses, or of external orthopedic devices such as helmets used to correct deformational plagiocephaly.
ABSTRACT Forensic cases where corpses remain unidentified, call for cranio-facial reconstructions... more ABSTRACT Forensic cases where corpses remain unidentified, call for cranio-facial reconstructions (CFR) to provide the media with material that might trigger recognition among those that used to be acquainted with the deceased. The task of reconstructing the face from the skull is usually done by an expert based on her/his knowledge and understanding of the correspondences between facial soft-tissue and the underlying skull. Reconstructions by different specialist often vary strongly in their outcomes. In response to this, various approaches towards computer-based CFR have been developed during the last tow decades, aiming at making the reconstructions less observer-dependent.. Additionally, computer based reconstructions are easily and fast altered and adapted by changing parameters such as age, gender or population affiliation, while manual CFRs are work- and time-consuming. Why is it necessary to analyse the nasal area separately? One of the major prerequisites for computer-driven CFRs are databases containing information about soft- and hard-tissue. A large repository of this data are hospitals, where medical 3D-imaging produces large amounts of three-dimensional representations of human heads. In order to minimise both unnecessary irradiation and costs, these scans are restricted to areas affected by pathologies. Creating separate databases for specific areas of the head allows for compiling larger amounts of data. As a result much larger databases can be obtained. The separate approach also helps to deal with another problem: while the osseous substructure of the nasal area is a relatively small part of the skull, the soft- tissue nose is a very prominent feature of the human face. This discrepancy might lead to larger prediction errors within this area, by methods estimating the facial surface as a whole. The development of a nose-specific procedure can solve these two problems, as a larger database can improve prediction results, and concentration on a specific sub-structure might reveal connections that are underrated in reconstructions based on global similarity measures. This dissertation provides solutions to the problem of predicting nasal soft- tissue shape, based on the shape of the underlying bone age, population affiliation and sex. To accomplish this, it has to be dealt with data acquisition as well as with problems concerning registration of 3D-structures. The main directive is to find the statistical interrelationship between soft-tissue and hard-tissue. This implies the need for a large database for building statistical models, estimating the most probable soft-tissue shape, based on the known hard-tissue information (and the additional attributes).
Images in paleoanthropology are of persuasive power, since they try to illuminate ancient life wh... more Images in paleoanthropology are of persuasive power, since they try to illuminate ancient life which is not otherwise visually documented. The scientific community, as well as public media and museums, aim to establish a window into the past in part through visualization of scenarios from prehistoric life and environments. The role of human ancestors in these settings is captured by body and especially facial reconstructions, which comparatively easily attract attention among nonscientific audiences and therefore raise public understanding of a complex field of research, allowing it to compete successfully with other, at times more tangible scientific subjects. Within the scientific community itself, reconstructions of early hominids play only a limited role, merely supplementing a whole range of field and laboratory research, evolutionary hypotheses, and the analysis of empirical data. Paleoanthropologists and paleontologists are aware of the interpretative character of facial reconstructions that go beyond the limited set of primary facts documented in the fossils themselves. The visual approach to paleoanthropology has changed strongly over time, varies with the media used, and depends on how we imagine our ancestors in coeval context. On the one hand, evolutionary theories and contemporary social ideas are influencing and shaping how we view and depict our ancestors. On the other hand, hominid reconstructions themselves, in turn, can influence our view and the underlying ideas. This chapter reflects on the development of facial reconstructions over time, along with influences such as the development of methods and techniques – from drawings to manual modeling to virtual 3D reconstructions. For exemplification, special emphasis will be put on Neanderthal reconstructions, as these are linked both to early attempts at facial reconstruction and to the subsequent methodological development of reconstruction techniques during the twentieth century. Starting with the first hominid fossils found, we trace the “evolution” of facial reconstructions of Neanderthals, in order to highlight contemporary perceptions and limiting factors in the visualization of our ancestors.
A fundamental impediment to the adoption of digital standards in physical anthropology is the vas... more A fundamental impediment to the adoption of digital standards in physical anthropology is the vast diversity of this area of research. Even within osteology, many investigations require some modification of existing standards to suit their specific study designs. This might be a reason for researchers not to use database software based exclusively on one particular standard. It also makes it difficult to keep track of research data compatibility and to process data from different investigations in one database system. Up to now, comprehensive and monolithic data standards have failed to address these issues. We propose a different approach, concentrating on the exact definition of individual data items. These are the building blocks researchers can use to describe the various aspects of their research, like skeletal inventories, research methods and work flows, resulting data and their processing employing mathematical transformations or textual conclusions. Because the building blocks of these descriptions are defined beforehand, the degree of compatibility between different investigations becomes evident. Our data standard, RDFBones, is an RDF (Resource Description Framework) ontology, containing a number of classes and properties for describing anthropological research and materials. Individual researchers can use these elements to define their methodology. That way, RDFBones helps to build standards, instead of prescribing them. Once a standard is formulated, however, it can be published and shared otherwise, supporting uniform methodology. RDFBones also creates a perfect means for sustained long-term data storage.
Genetic and climate-driven estimates of past population dynamics are increasingly influential in ... more Genetic and climate-driven estimates of past population dynamics are increasingly influential in broader models of hominin migration and adaptation, yet the contribution of stone artifact variability remains more contentious. Scientists are increasingly recognizing the potential of unretouched stone flakes ('flakes') in exploring existing models of hominin behavioral evolution. This is because flakes (1) were produced by all stone tool manufacturing groups in the past, (2) are abundant from the inception of the archaeological record up into the ethnographic present, and (3) preserve under most conditions. The statistical tools of 3D geometric morphometrics capture detailed approximations of flake form that are challenging to document with conventional artifact analyses. We analyze a collection of 717 3D scans of experimentally produced flakes from 5 production strategies that were practiced by hominins through large parts of the Pleistocene and that scientists have drawn on also to make demographic arguments about past human behavior (n ¼ 45 reduction sequences, n ¼ 3 knappers naive toward the study objectives). First, as a proof of concept, we demonstrate that we can estimate the strategies used to produce these flakes at a high success rate even when flakes from early stages of core reduction are included. We frame the significance of this finding against archaeological classifications from several key Middle Paleolithic assemblages in France (n ¼ 4 sites, n ¼ 28 layers, n ¼ 16,467 flakes). Second, we show that 3D geometric morphometrics captures subtle differences in these strategies that influence flake formation on a flake-by-flake basis and that reflect decisions made by knappers about platform selection, preparation, and core-surface management. We explore the broader potential of our model with a crossvalidation approach, and we describe a means of assessing flake form on a continuum wherein variability among assemblages separated by large expanses of space and time can be meaningfully explored.
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