Virtual anthropology : the forensic approach

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Thesis

Reference

Virtual anthropology : the forensic approach

ULDIN, Tanya

Abstract

MDCT-bone imaging is a recent and very specific research field in forensic anthropology. Its potential derives from daily routine post mortem MDCT that delivers an invaluable collection of permanent skeletal data, ante-mortem information as well as the possibility of non-invasive investigations. These digital data can be easily stored, examined and shared. The aim of the thesis was to understand how virtual objects are produced and to identify potential sources of error. We evaluated conventional morphoscopic scoring systems of age and sex estimation methods as well as linear distance measurements using real and 3D-volume rendered bones.

The results demonstrated that acquisition parameters have influence on the quality of bone reconstructions. Moreover, we could show that the application of conventional anthropological methods is possible, however, technical restrictions still must be solved.

ULDIN, Tanya. Virtual anthropology : the forensic approach. Thèse de doctorat : Univ.

Genève, 2016, no. Sc. 4926

DOI : 10.13097/archive-ouverte/unige:94270 URN : urn:nbn:ch:unige-942701

Available at:

http://archive-ouverte.unige.ch/unige:94270

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UNIVERSITÉ DE GENÈVE

Département de Génétique et Evolution FACULTÉ DES SCIENCES

Unité d'anthropologie Professeure Alicia Sanchez-Mazas

Centre Universitaire Romand de FACULTÉ DE MÉDECINE

Médecine Légale Lausanne-Genève Professeur Patrice Mangin

___________________________________________________________________

Virtual Anthropology – The Forensic Approach

THÈSE

présentée à la Faculté des sciences de l’Université de Genève pour obtenir le grade de Docteur ès sciences, mention anthropologie

par Tanya ULDIN

De Allemagne

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Acknowledgements

I would like to express my gratitude to my advisors, Professor Patrice MANGIN, former head of the University Center of Legal Medicine, Lausanne-Geneva and Professor Alicia SANCHEZ-MAZAS, head of the Laboratory of Anthropology, Genetics and Peopling History, University of Geneva, for their guidance, patience, and useful critiques. I would also like to express thanks to the committee members Prof. Reto MEULI, head of the Department of Diagnostic Imaging and Interventional Radiology, University Hospital of Lausanne and Prof. Gérald QUATREHOMME, head of the Department of Forensic Pathology and Forensic Anthropology, University of Nice for their insightful comments and the vivid discussion during my thesis defense.

Special thanks should be given to the forensic radiographers of the Unit of Forensic Imaging and Anthropology at the University Center of Legal Medicine, Lausanne- Geneva. I am particularly grateful for the assistance given by Alejandro DOMINGUEZ, technical manager of the Unit of Forensic Imaging and Anthropology.

I greatly appreciated the collaboration with my co-authors, the useful and constructive discussions and recommendations on this project by Professor Paul VAUCHER, School of Health Sciences, University of Applied Sciences, Fribourg, Dr.

Sébastien DE FROIDMONT, forensic pathologist at the Institute of Legal Medicine, University of Liège, and Dr. Jochen GRIMM, Departments of Medical Radiology and Legal Medicine, University Hospital of Lausanne, Switzerland.

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Abstract

Two decades ago computed tomography (CT) has found its way into physical anthropology. Paleo-anthropologists have been the first using CT-scans as a non- invasive tool to reconstruct fossil human remains. During the last decade, numerous studies have also been produced in forensic anthropology, showing the feasibility of virtual osteology. At the same time, forensic radiology has become of importance in the field of legal medicine. Nowadays multi-detector computed tomography (MDCT) is a common tool to complement conventional autopsy and to improve the quality of the diagnosis in many medico-legal institutes. The advantages are plain obvious for all disciplines: sample collection is non-invasive and the obtained digital data are easy to store and to access.

Since 2008, post mortem MDCT is conducted as routine investigation before medico-legal examinations (autopsy or external examination) at the University Centre of Legal Medicine, Lausanne–Geneva (CURML). Post mortem MDCT generates an invaluable data pool, which could serve for further basic research and method evaluation. In this respect, research in forensic anthropology is hampered by the difficulty of obtaining a reference population with a balanced distribution of sex and age groups (most deaths processed in a medico-legal institute relate to individuals between 40 and 70 years). However, recruitment in forensic anthropology often provides precise individual data unlike conventional anthropological collections where such information is generally incomplete or absent. For this reason, the aim of the present work is to establish a database of virtual skeletons recruited from forensic cases in our center in Lausanne and Geneva to achieve an anthropological database of virtual skeletons available for research as well as for training and routine

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However, before starting such a database it is essential to be familiar with the MDCT device and its basic technical conditions. It is necessary to understand how virtual objects are produced otherwise identification of error sources as well as image interpretation would not be possible.

A feasibility study and three comparative studies have been conducted with the aim to investigate whether morphoscopic age and sex indicators used in conventional anthropological methods are applicable to MDCT reconstructed bones. We also wanted to learn about the influence of MDCT scanning parameters on the accuracy of anthropological methods applied to virtual bones. Therefore, morphoscopic scoring systems of age and sex estimation methods as well as linear distance measurements have been examined using real and 3D-volume rendered bones.

The results demonstrated that acquisition parameters have influence on the quality of bone reconstructions. Moreover, we could show that the application of conventional anthropological methods is possible although technical restrictions still should be solved.

Key words

Virtual anthropology; forensic anthropology; forensic radiology; bone imaging;

anthropological database; virtual skeletons, osteometry; skeletal age assessment;

skeletal sex determination

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Résumé

La tomodensitométrie (CT) a trouvé sa place il y a deux décennies en anthropologie physique. Les paléoanthropologues ont été les premiers à utiliser le CT-scan comme un outil non invasif pour reconstruire les restes humains à l’état de fossiles. Au cours de la dernière décennie, de nombreuses études ont également été produites en anthropologie forensique, démontrant ainsi la faisabilité de l'ostéologie virtuelle. Dans le même temps, l’imagerie forensique a pris de l’importance dans le domaine de la médecine légale. Aujourd'hui la tomodensitométrie multi barrettes (MDCT) est actuellement un outil usuel en complément de l’autopsie conventionnelle permettant d'améliorer la qualité du diagnostic dans de nombreux instituts médico- légaux. Les avantages du MDCT sont clairement évidents pour toutes les disciplines concernées : la collecte des échantillons est non-invasive et les données numériques obtenues sont faciles à stocker et à exploiter.

Depuis 2008, la tomodensitométrie post-mortem est utilisée comme une investigation de routine avant l’autopsie ou l'examen externe au Centre Universitaire Romand de Médecine Légale, Lausanne-Genève (CURML). En effet, la tomodensitométrie post mortem génère une masse de données inestimable en anthropologie physique pour des recherches tant au plan fondamental qu’appliquées.

A cet égard, la recherche en anthropologie forensique se heurte à la difficulté d’obtenir une population de référence de distribution équilibrée en sexe et en classe d’âge (la majorité des décès traités dans un institut de médecine légale concernent des individus d’âge compris entre 40 et 70 ans). En revanche, le recrutement en anthropologie forensique permet d’obtenir des données individuelles souvent précises contrairement aux populations anthropologiques classiques où ce type

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présent travail est d’obtenir la mise en place d’une base de données de squelettes virtuels à partir des cas médico-légaux recrutés dans notre centre à Lausanne et à Genève pour aboutir à une banque de données anthropologiques virtuelles disponible tant pour la recherche que pour la formation et les investigations de routine.

Toutefois, avant de commencer l’implémentation d’une telle base de données, il est essentiel de tester et de valider les capacités de la technologie tomodensitométrique afin de vérifier la faisabilité d’une telle méthode. Plus particulièrement, il est indispensable de contrôler et comprendre comment les objets sont produits afin de détecter toute source d’erreur ou d’interprétation des images virtuelles obtenues.

Une étude de faisabilité et trois études comparatives ont été menées dans le but de déterminer si les indicateurs morphognostique d'âge et de sexe utilisés dans les méthodes anthropologiques conventionnelles sont applicables aux os reconstitués par MDCT. Nous voulions aussi tester l’influence des paramètres du MDCT-scan sur la précision des méthodes anthropologiques appliquées aux os virtuels. Par conséquent, les systèmes de notation des méthodes morphognostiques d'estimation de l'âge et du sexe ainsi que des mesures de la taille ont été évalués à partir d'os reconstitués en 3D.

Les résultats ont montré que les paramètres d'acquisition ont une influence sur la qualité des reconstructions 3D des ossements. En outre, nous avons pu montrer que l'application de méthodes anthropologiques classiques est possible bien que des problèmes techniques doivent encore être résolus.

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List of Figures and Tables

Figures

Figure 1 Age and sex distribution of forensic cases at the CURML in 2008. ...18 Figure 2 Percentage of acquisition parameters published in forensic anthropological studies (2005-2015) used in this thesis (n=40). ...22 Figure 3 Scheme showing the skeletal regions of interest of the scanning protocol. ...31 Figure 4 (a–e) Example of reconstructions in 2D and 3D of case no. 15, a 17-year-old

female. ...35 Figure 5 (a–e) Example of reconstructions in 2D and 3D of case no. 12, a 49-year-old male.

...36 Figure 6 Demonstration of the results of the final age estimations in a chart. ...40 Figure 7 Chart showing the diminution of wrong estimations (more than 5 years’ difference between estimated age range and age at death). ...41 Figure 8 (a–c) Demonstration of the importance to choose correct scanning parameters. ...45 Figure 9 Schema for (a) measurement of the humeral and femoral caput diameter according to Martin (1914), and (b) the stages as per Nemeskéri et al. ...58 Figure 10 Schema dividing (a) the proximal part of the femur into four areas, and (b) the proximal part of the humerus into three areas to define a score of trabecular destruction for each area. ...58 Figure 11 Depictions of (a) a conv. X-ray image, (b) a MDCT-SS image, and (c) a MDCT- MIP image from a coronal plan, as well as (d) a MDCT-SS image from a transversal plan of one humerus, (e) a conv. X-ray image, (f) a MDCT-SS image, and (g) a MDCT-MIP image from a coronal plan, as well as (h) a MDCT-SS image from a transversal plan of one femur.

...60 Figure 12 Linear correlation between radiological methods in the staging as per Nemeskéri et al. (1960) (experienced observers). ...65 Figure 13 (a) A conv. X-ray image and (b) a MDCT-SS image of one humerus, illustrating an osteodensity (arrow) that is visible only on the MDCT image. ...65 Figure 14 (a) Cranial sutures and their subdivisions and (b) the five point rating scale of

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Figure 17 (a) Real bone versus (b) virtual bone (MDCT): sacro-iliac part of coxal bone with 3D-reconstruction artifact (substance loss). ...83 Figure 18 (a) Real bone versus (b) virtual bone (MDCT): superior aspect of the skull with 3D reconstruction artifact (surface smoothing). ...85 Figure 19 Four-point Likert-scale to assess image quality. ...95 Figure 20 (a) Maximum bone length according to Martin (1914), (b) Maximum length

projection on 3D-volume rendered bones. ...95 Figure 21 GE Lightspeed Ultra 8 (8-row unit). ... 105 Figure 22 GE Lightspeed VTC 64 (64-row unit). ... 106 Figure 23 Bones ex-situ; comparison of image quality between an 8-row (a, b) and a 64-row (c, d) MDCT unit, ST 0.625 mm (a, c) and 1.25 mm (b, d). ... 107 Figure 24 Comparison of 3D surface reconstructions obtained by (a) optical surface scan and by (b-d) MDCT scan (slice thickness 0.625 mm)... 110 Figure 25 Comparison of real bone (a), 3D-surface reconstructions by optical surface scan (b) and 3D-surface reconstructions (c-d) by MDCT scan (slice thickness 0.625 mm). ... 111 Figure 26 GOM ATOS Compact Scan 5M (5 million object points), TRITOP Photogrammetry System (Nikon D2X) ... 113

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Tables

Table 1 The secondary sex characters of the skull and the pelvis on which the determination

of the sex of the individuals were based ...32

Table 2 Detailed demonstration of the results of age estimation using the complex method and the final estimation of age of the three observers...37

Table 3 Results of age estimation by the three observers according to the complex method and the final interpretation giving the number of cases with results in the different groups explained in Table 2 ...38

Table 4 Overall inter-observer reliability of observations for humeri (n = 24). ...62

Table 5 Overall inter-observer reliability of observations for femora (n = 28). ...62

Table 6 Inter-observer reliability of stages as per Nemeskéri et al. (1960) in relation with the observer’s experience level. ...63

Table 7 Scoring system of the sacro-iliac area of the coxal bone according to Schmitt (2005). ...78

Table 8 Correlations of scores between real and virtual bones ...82

Table 9 Reliability (interclass correlation coefficients, ICCs) of scores used for real and virtual bone. ...83

Table 10 Scanning parameters. ...93

Table 11 Monitor parameters. ...94

Table 12 Average bone length measurements. ...96

Table 13 Difference between caliper and CT length measurements. ...97

Table 14 Subjective image quality. ...97

Table 15 Scanning parameters ‘ex-situ’ used during protocol development. ... 104

Table 16 Scanning parameters ‘in-situ’ used during protocol development. ... 104

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I. Introduction

The use of modern cross-sectional imaging such as computed tomography (CT) has influenced medicine and numerous other domains such as biology, geology, archaeology, forensic or materials science. As a non-invasive diagnostic tool, CT has many advantages. The digitized object can externally and internally be examined and, at the same time, be manipulated without damage. Investigations are repeatable and verifiable at any time. Moreover, the digital data or the 3D-printed hard copy of the object can easily be replicated and shared.

Within the last two decades, utilization of multi-detector computed tomography (MDCT) was increasingly growing in clinical research and the demand for specific data-acquisition and post-processing parameters has led to various recommendations and protocols (e.g., Geijer and El-Khoury, 2006; Kalra et al., 2008;

Ringl et al., 2009; Davies and Pettersson, 2012; Halliburton et al., 2012; Parmar et al., 2014). However, different research settings demand field-specific solutions. In contrast to medicine, the history of MDCT-implementation in physical and forensic anthropology has developed differently as following chapters will show.

I.1 Virtual anthropology - the use of CT in physical anthropology

As soon as Hounsfield (1973) introduced CT, physical anthropology and paleo- biology were benefitting from such non-invasive procedures, which are essential for the conservation of precious and often fragile fossil and prehistoric human skeletal or mummified remains (Jungers and Minns, 1979; Harwood-Nash, 1979). Specific scanning protocols and recommendations have been published since then (e.g., Tate

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and Cann, 1982; Conroy and Vannier, 1984; Sumner et al., 1985; Ruff and Leo, 1986; Spoor et al., 1993).

Especially the studies of Ruff and Leo (1986) and Spoor et al. (1993) revealed precisely potential error sources of the new technique and provided specific guidelines for scanning bones, image processing, and interpreting the obtained data.

Both studies have described, for the first time, basic issues such as measurement inaccuracies due to partial volume effect and wrong threshold values, or the problematic relation of CT numbers and bone densities; issues that still occur in modern medical research (e.g., Whyms et al., 2013; Molteni, 2013; Cotter et al., 2015).

The development of spiral CT in 1989 (Kalender et al., 1990) provided enhanced cross-sectional data acquisition and better image processing software for 3D surface reconstructions. This has been proved to be advantage for the investigation of the Tyrolean iceman (Höpfel et al., 1992; Seidler et al., 1992). The examination of the precious mummy called also attention to the advantages of stereolithography; today known too as 3D-Printing or reversed engineering (used for surgical planning and implant design). Zur Nedden et al. (1994a-b) have utilized MDCT data to reconstruct the skull of the Tyrolean iceman three-dimensionally, and they could prove the accuracy of measurements taken from the model in comparison to the mummy’s head. The study has also shed light on artifacts such as pseudo-lesions that can occur due to volume averaging effects (Zur Nedden et al., 1994a); a problem not yet

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devices that are commonly used depending on the research purpose (Weber and Bookstein, 2011). Weber and co-workers, who took part in the study group of the Tyrolean iceman, invented the term “virtual anthropology” first (Weber, 2001; Weber et al., 2001; Weber, 2015). They have pointed out the enormous advantages of digitized data, such as accessibility of even hidden anatomical structures, permanent availability of the virtual object, reproducibility of measurements, application of advanced methods (geometric-morphometrics), and the possibility of easy data sharing (Weber 2015). Research in paleoanthropology has mainly focused on computer-aided reconstruction of fossil skulls and MDCT-based morphometric and shape analyses since then (Zollikofer et al., 1998; Weber et al., 2001; Zollikofer and Ponce de Léon, 2002; Gunz et al., 2009; Neeser et al., 2009; Benazzi et al., 2011;

Guipert et al., 2014). Accordingly, two textbooks have been published providing profound technological insight and specific guidelines (Zollikofer and Ponce de León, 2005; Weber and Bookstein, 2011). Latest developments in paleo-anthropology show the positive impact of this digital revolution. The discovery of Homo naledi, an extinct hominin species found in South Africa (Berger et al., 2015b), demonstrates the consequent realization of Weber’s demand for ‘Glasnost in Paleoanthropology’

(Weber, 2001). Surface scans of several skeletal parts have been published with open-access on the website of MorphoSource, a data archive for 3D data of fossils (Berger et al., 2015a), which permits an immediate scientific exchange with the research community. Meanwhile, clinical research and forensic sciences have also benefited from these developments in paleoanthropology (e.g., Benazzi and Senck, 2011; Guyomarc’h et al., 2012).

Paleontology and zoo-archaeology are related research fields to

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established for several years, to reconstruct extinct species, to apply advanced statistical methods, and to facilitate data sharing (Cunningham et al., 2014).

Furthermore, comparative osteological collections have been set up to examine skeletal anatomy of different species, especially when access to reference collections of real bones is restricted or not available (Niven et al., 2009; Betts et al., 2011).

Lately, fossil bones have been ‘excavated’ from surrounding rocks using a micro-CT scan and then transmitting obtained volumetric data to a scanning laser to separate both materials (Du Plessis et al., 2013), which demonstrates the far-reaching usage of CT data.

I.2 Post mortem MDCT and forensic anthropology

Radiographic methods are well established in forensic medicine and forensic anthropology (Hines et al., 2007; Brogdon and Lichtenstein, 2011; Leo et al., 2013).

They serve either to identify unknown deceased by comparison of individual characteristics in ante and post mortem radiographies, to develop a biological profile by estimating age, sex or stature, or to evaluate recent injuries (Riddick, 2011;

Brogdon, 2011a-b). Plain radiography is inexpensive and simple to apply; therefore, methods of forensic-radiographic identification are still newly developed.

Quatrehomme et al. (2014), for example, have pointed out that trabecular bone morphology can lead to positive identification. Stephan and co-workers have developed a geometric-morphometric method for clavicle-shape comparison by the

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In contrast, routine application of MDCT in forensic medicine and forensic anthropology is a recent development. High costs and limited accessibility may have been reasons that impeded regular utilization for many years. The term post mortem computed tomography (PMCT) was introduced in the early 1980s (Krantz and Holtås, 1983). However, CT was only frequently used until the mid-1990s. Reichs (Reichs and Dorion, 1992; Reichs, 1993) applied, for the first time, radiographic frontal sinus comparison to CT. Donchin et al. (1994) conducted one of the first studies comparing whole-body CT scan versus conventional autopsy. They could demonstrate that none of the methods are superior to the other, but combining both methods would ameliorate the results of medico-legal investigations. Other studies have been evaluating the potential of CT data enhancing forensic facial reconstructions methods (Phillips and Smut, 1996; Quatrehomme et al., 1997).

Dirnhofer and co-workers finally invented an image-guided virtual autopsy as a supporting tool for conventional autopsy techniques more than ten years ago (Dirnhofer et al., 2006; Thali et al., 2009). As Weber (2001) already pointed out for virtual anthropology, the advantages of virtual autopsy such as permanent availability of the digitized objects / bodies, reproducibility of methods and data sharing will lead to investigations that are more objective. Nowadays, forensic radiology has become routine application in many medico-legal institutes and the opportunity for forensic anthropologist having permanent access to MDCT is increasing. Hence, research in post mortem MDCT is rapidly growing.

As far as forensic anthropology is concerned we can differentiate following publication topics: the first group includes papers describing the general utilization of MDCT for disaster victim identification (DVI) purposes that covers medico-legal and

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al., 2007a; O’Donnell et al., 2011; Brough et al., 2014), or case reports presenting the application of identification methods to MDCT-images (Dedouit et al., 2007b; 2011;

2014; Blau et al., 2008; Bassed and Hill, 2011).

The second group consists of more specific studies evaluating main anthropological characteristics that are building the biological profile of unknown human remains such as age (Pasquier et al., 1999; Telmon et al., 2005; Dedouit et al., 2008; Barrier et al., 2009; Ferrant et al., 2009; Grabherr et al., 2009; Pommier et al., 2009; Dang-Tran et al., 2010; Moskovitch et al., 2010; Wade et al., 2011; Chiba et al., 2013; 2014; Lottering et al., 2013; 2014a-b; Villa et al., 2013; Minier et al., 2014; Wink, 2014; Boyd et al., 2015), sex (Mahfouz et al., 2007; Grabherr et al., 2009; Ramsthaler et al., 2010; Uysal Ramadan et al., 2010; Decker et al., 2011;

Uthman et al., 2011, Bilfeld et al., 2012; Karakas et al., 2013; Mokrane et al., 2013;

Rodriguez et al., 2014; Petaros et al., 2015; Hishmat et al., 2015; Michel et al., 2015), and stature (Karakas et al., 2011; Rodriguez et al., 2014; Torimitsu et al., 2014a-b;

Hishmat et al., 2015; Macaluso, 2015), or measurements in general (Robinson et al., 2008; Verhoff et al., 2008; Guyomarc’h et al., 2012; Franklin et al., 2013; de Froidmont et al., 2013; Brough et al., 2013; Lorkiewicz-Muszyńska et al., 2013; 2015;

Richard et al., 2014; Stull et al., 2014).

Additionally, several studies are investigating in the application of conventional radiographic methods to MDCT. For example, the comparison of ante and post mortem radiographies of frontal sinus patterns, which has been proven reliable in

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Furthermore, Wade et al. (2011) and de Froidmont et al. (2013) have conducted studies comparing conventional radiography and MDCT in investigating trabecular bone for age-at-death estimation. Both studies are indicating that MDCT is superior to conventional radiography in analyzing fine anatomical structures. Other studies have been testing the potential of MDCT in investigating trabecular bone for age-at- death estimation (Pasquier et al., 1999; Barrier et al., 2009; Ferrant et al., 2009;

Grabherr et al., 2009; Villa et al., 2013). Nevertheless, further investigations are needed to develop methods appropriate for MDCT.

Beside the identification of unknown deceased, age estimation in the living is a medico-legal field of activity using also radiography and MDCT. Specialists of different disciplines such as forensic pathologists, odontologists, radiologists, and anthropologists must take into consideration mainly physical, dental and osseous (hand wrist, medial clavicle) development to assess age of minor or young adult individuals (Schmeling et al., 2008; 2011; Black et al., 2010). In contrast to the studies mentioned before that have examined mostly MDCT-images of dry bones, studies on age estimation in the living have evaluated data acquired from bones within the body. Hereby, acquisition protocols should follow clinical guidelines to keep radiation dose as low as possible. MDCT acquisition parameters such as tube potential, tube current, beam collimation, and others thus must be adequately balanced to obtain appropriate image quality (Schmeling et al., 2000; Kalra et al., 2008; Mahesh, 2012). Schmeling and co-workers, who mainly worked on the ossification of the medial clavicle epiphyses (Schmeling et al., 2004; Schulz et al., 2005; Kellinghaus et al., 2010a-b), therefore, have tested different reconstructed slice thicknesses. They found that this parameter considerably influences the results of

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(Mühler et al., 2006). This example shows clearly the importance of CT scanning parameters. However, many questions should be answered yet to better understand the utilization and the potential of MDCT. Regarding MDCT application in forensic anthropological studies, only a few of them have published sufficiently protocols for data acquisition and imaging processing until now. Hence, data comparability, which is essential for sound science, remains limited.

I.3 Virtual anthropology – the forensic approach

Post-mortem identification is still a difficult issue in the daily medico-legal routine.

Human remains of unknown deceased are often heavily decomposed or even skeletonized or incomplete. The first steps in the identification procedure are usually odontological examinations and DNA profiling if ante mortem data and reference samples are available. In case no reference data exists, due to missing teeth or lack of DNA preservation, a biological profile must be established by the anthropologist including age, sex, stature, and any other information on origin, anomalies or individual anatomical traits. Such parameters are less reliable than positive identification by dental traits or DNA. However, a combination of them can lead to a presumptive identification and narrow down the list of missing persons (Thompson and Black, 2007). For the best approach, the anthropologist is obliged to choose the most appropriated techniques. Additionally, those methods should meet specific requirements in forensic practice (Ritz-Timme et al., 2000a-b; Christensen, 2004;

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mean they should not be evaluated or revised, but the most important challenge in forensic anthropology and bio-archeology remains age-at-death assessment.

Age-at-death assessment

Chronological age, which is documented by the individual’s birth date, is only slightly correlated with biological or skeletal age, which is influenced by different factors such as physical activity, nutrition, health, environment or genetics.

Age assessment of non-adults up to young adulthood, about 25 to 30 years, is quite satisfactory. Skeletal development (epiphyseal union, long bone length, and dental formation) is more influenced by genetics than by external factors; whereas dental growth is the most reliable parameter as it is the less influenced (Scheuer and Black, 2000). Latest development in forensic age estimation in the living have initiated research on sterno-clavicular joints (e.g., Kellinghaus et al., 2010a-b; Bassed et al., 2011; Wittschieber et al., 2014), hand wrist (e.g., Thiemann et al., 2006;

Schmidt et al., 2008; Baumann et al., 2009; Tisé et al., 2011), and other skeletal parts (e.g., Camiere et al., 2012; Saint-Martin et al., 2013; Wittschieber et al., 2013) that could serve assessing age of minors and young adults. However, all this research is performed using radiological imaging that is not yet sufficiently correlated to conventional morphoscopic methods.

Adult age assessment is mainly measured by degenerative morphological changes, which are highly influenced by individual factors, and may even vary in different skeletal traits. Thus, estimation error is increasing and age range becomes broader. Decades of research have passed by and numerous studies have been conducted to overcome those issues. Early research investigated single traits like

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cranial suture obliteration (Broca, 1875; Todd and Lyon Jr., 1924; 1925a-c; Krogman, 1930), morphological changes in the pubic symphysis (Todd, 1920; 1921a-c; 1923;

1930; Hanihara, 1952; McKern, 1957; McKern and Stewart, 1957), or changes in the trabecular structure of long bones (Schranz, 1933; 1959; Hansen, 1953/54). By these methods, age-at-death is estimated according to documented changes of single- traits.

Since the mid-20th-century, multiple-trait approaches have been put forward to ameliorate age estimation methods (Lee, 1971; Meindl et al., 1983; 1985; 1990;

Lovejoy et al., 1985a; Mensforth and Lovejoy, 1985; Bedford et al., 1993; Fairgrieve and Oost, 1995; Meindl et al., 1995).

Nemeskéri and co-workers (Nemeskéri et al., 1960; Acsádi and Nemeskéri, 1970) developed the ‘complex method’ using a combination of cranial suture closure, changes of the pubic symphysis and changes of trabecular bone structures of proximal humerus and femur. The method became very popular since it was included in the “Recommendations for Age and Sex Diagnoses of Skeletons” by the

“Workshop of European Anthropologist” in 1978 (Ferembach et al., 1979; 1980).

Despite all criticism (e.g. Meindl et al., 1985; Brooks and Suchey, 1990) it is still used in German-speaking countries in the context of bio-archeology.

Lovejoy and co-workers (Lovejoy et al., 1985a; Bedford et al., 1993) introduced the ‘multifactorial summary age method’, which includes as much age indicators as possible. The main five aspects are auricular surface, pubis symphysis, ecto-cranial

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At the same time, single and multiple trait approaches have been either newly developed, tested or revised (Kemkes-Grottenthaler, 1993; Baccino et al., 1999;

Gehring et al., 2002; Schmitt et al., 2002; Nagar and Hershkovitz, 2004; Wittwer- Backofen et al., 2008; Martrille et al., 2007; Kimmerle et al., 2008; Konigsberg et al., 2008). In particular cranial suture obliteration (Brooks, 1955; Dérobert and Fully, 1960; Schmitt and Tamaska, 1970; Masset, 1971; Perizonius, 1984; Meindel and Lovejoy, 1985; Key et al., 1994; Kemkes-Grottenthaler, 1996; Hershkovitz et al., 1997; Galera et al., 1998; Lynnerup and Jacobsen, 2003, Dorandeu et al., 2008;

Beauthier et al., 2010), pubic symphysis (Brooks, 1955; Gilbert and McKern, 1973;

Hanihara and Suzuki, 1978; Suchey, 1979; Katz and Suchey, 1986; Sucheey et al., 1986; Brooks and Suchey, 1990; Suchey and Katz, 1998; Klepinger et al., 1992;

Hartnett et al., 2010a; Buk et al., 2012; Milner and Boldsen, 2012; Wescott and Drew, 2015), sacro-iliac joints (Kobayashi, 1967; Lovejoy et al., 1985b; Murray and Murray, 1991; Schmitt and Broqua, 2000; Buckberry and Chamberlain, 2002; Malgosa et al., 2004; Osborne et al., 2004; Schmitt, 2004; 2005; Igarashi et al., 2005; Mulhern and Jones, 2005; Falys et al., 2006; Hens et al., 2008; Rougé-Maillart et al., 2009; Buk et al., 2012; Hens and Belcastro, 2012; Martins et al., 2012; Milner and Boldsen, 2012;

Moraitis et al., 2014; Wescott and Drew, 2015), and the sternal end of the ribs (İsçan et al., 1984a-b; 1985; 1987; İsçan and Loth, 1986a-b; 1989; İsçan, 1991; Kunos et al., 1999; Schmitt and Murail, 2004; Hartnett et al., 2010b) became the most investigated age traits.

In addition, advanced statistical methods have been developed (Aykroyd et al., 1997; 1999; Boldsen et al., 2002; Lucy et al., 2002; Corsini et al., 2005; Samworth and Gowland, 2007; Buk et al. 2012) to eliminate statistical errors and augment age

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Boldsen and co-workers (Boldsen et al., 2002; Milner and Boldsen, 2012), for example, introduced transition analysis (TA), an advanced statistical method to overcome issues concerning aging older adults, the influence of a small sample size and the fact that age estimates will mimic the age distribution of the reference sample. Information on nineteen different age indicators from the pubic symphysis, the sacro-iliac joint and cranial sutures is collected using newly developed scores and the ADBOU computer program. ADBOU weights age information based on their accuracy and precision. Then, maximum likelihood as well as multifactorial likelihood estimates for each single trait is calculated. Maximum likelihood is calculated by choosing uniform or informed priors. Uniform prior would indicate that all ages are equally distributed in a population, while by choosing informed priors (archaeological or forensic), either a reference population from a 17^th century cemetery of Denmark or North American homicide data from 1996 are used for calculating the maximum likelihood estimate. One advantage of TA is that it can handle missing data, which makes the program superior to other statistical approaches. Moreover, the use of various anatomical parts has augmented the probability to better assess advanced ages. Milner and Boldsen (2012) later conducted a validation study on TA using skeletons of modern Americans with known age. They concluded that the number of age indicators used is too limited to particularly estimate age of persons between 40 and 70 years. Thus, they recommend including experience-based assessments deriving information from skeletal parts that are not yet used as standardized methods.

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broad age classes (younger than 30, 30-60, and older than 60 years). The results of both, Milner and Boldsen (2012) and Buk et al. (2012), support our empirically derived observations from daily forensic-anthropological routine work.

Regarding the development of age estimation methods, Kemkes-Grottenthaler (2002) also calls attention to innovative approaches that should consider information of gerontology, intra- and inter-personal as well as inter-population differences.

Investigations on age factors should also consider sexual dimorphism, laterality, or geo-climatic, cultural and socio-economic influences.

Beside all issues concerning age estimation methods resulting from varying biological and environmental aging factors, observer’s experience or inappropriate statistical approaches, the reference data derived from documented skeletal or cemetery collections are another source of error.

Reference series

The main need in anthropology remains a comprehensive collection of documented skeletons. Commonly, reference series used in anthropological research consist of skeletal collections of at least known age and sex. These series represent anatomical, medico-legal or cemetery populations that are made up of cadaver donors, forensic cases, and historic or modern exhumation, respectively. Even if age, sex and at best ethnicity is known, information such as occupation, weight, medical history (e.g. pregnancies, pathologies) are missing or are not throughout available (Usher, 2002). Due to its origin, most present skeletal samples are covering only specific parts of a population or selected parts of an individual. Therefore, criticism has been passed many times on the representativeness of these reference samples;

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either sex ratio is inhomogeneous, ethnic diversity is lacking, age groups are missing or documented data of the deceased person are not reliable. Moreover, secular changes should be considered when, for example, evaluating methods derived from cemetery populations of the 19^th century (Usher, 2002; Komar and Grivas, 2008;

Weis, 2015).

The famous ‘Robert J. Terry Anatomical Collection’ held today by the National Museum of Natural History in Washington D.C. is mainly composed of individuals born in the 19^th and early 20^th century donated by hospitals in St. Louis, Missouri (Hunt and Albanese, 2005). Those individuals belong only to a low socio-economic level. Thus, the collection cannot represent the whole living population, which should be taken into consideration when evaluating or developing methods.

Komar and Grivas (2008) examined also the composition of the ‘Maxwell Museum Documented Collection’ in Albuquerque, New Mexico. They could demonstrate that the collection of body donations neither represent the living nor the deceased population of New Mexico from which it differs significantly in sex, age and ethnicity composition. White males, older than 45 years are overrepresented, which proves a donation bias. Ethnic bias in body donation has been recently reported for several collections in the USA that consist of mainly elderly people with European origin (Weiss, 2015).

Likewise, bias in reference samples from clinical studies demands attention.

Gelbrich et al. (2010) demonstrated with a study on quality of reference data, how

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Regarding appropriate data collection, Usher (2002) has recommended a list of basic parameters that could optimize the composition of reference series:

• Age-at-death is known (not self-reported) and verified by documents

• Both sexes are equally represented

• Various socio-economic statuses are included as well as

• Different health conditions and

• Different ethnicities [Sanchez-Mazas et al. (2012, p 1; 3-5) recommend as strategies for characterizing human population “… avoiding outdated racial classifications and population names (e.g. ‘Caucasian’) and using instead geographic and/or cultural (e.g. linguistic) criteria to describe human populations (e.g. ‘pan-European’).” Moreover, origin should be self-reported and not only documented by a third person]

• The collection should be easily accessible.

While it is difficult for anatomical or cemetery collection to meet these criteria, a collection of post mortem MDCT scanned individuals might be a solution.

Post mortem MDCT at the University Center of Legal Medicine, Lausanne- Geneva

Since 2008, post mortem MDCT is conducted as routine investigation before medico-legal examinations (autopsy or external examination) at the University Centre of Legal Medicine, Lausanne–Geneva (CURML). Due to this practice, about 400 to 500 cases a year are passing through MDCT whole-body scan using a standard routine scanning protocol (head, thorax and abdomen; slice thickness of 1.25 mm;

reconstruction algorithms for bone, soft tissue and lungs). Lately, specialized forensic

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radiographers have been introduced to pre-autopsy imaging to perform all radiological examinations including post mortem angiography. The implementation of forensic radiographers has clearly improved image quality and allows complex radiological examinations in daily routine. The workload of forensic pathologists and other experts has been reduced significantly. Moreover, they are involved in research studies of virtual anthropology on developing new scanning protocols (Schneider et al., 2012). Furthermore, quality of radiological diagnosis is guaranteed by board certified radiologists with more than 10 years of experience who evaluate MDCT data, including neuro-radiologists, pediatric radiologists, and osteo-radiologists.

Anthropological database

Post mortem MDCT generates an invaluable data pool, which could serve for further basic research and method evaluation, opening new opportunities in several research fields. With the regard to forensic anthropology, issues such as insufficient sample composition and lack of individual data could be solved. Thus, we have planned to set up a database of virtual skeletons (anthropological database). We expect about 300 to 500 cases a year to augment such a database. Unidentified or heavily mutilated bodies will be excluded. Besides age and sex, additional information such as ancestry, socioeconomic status, and medical history will be collected by the aid of a questionnaire integrated to daily medico-legal routine work (see chapter II.7).

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This is in line with previous studies on the composition of reference collections (Komar and Grivas, 2008; Weis, 2015), where it could be demonstrated that reference samples derived by body donation or in medico-legal context do not represent the living population as their input is biased in several aspects such as unbalanced age classes or ethnicity as well as underrepresentation of women. To overcome these problems, we propose to predefine a sample size of 100 men and women (each per 5-year-classes) as a statistical requirement to obtain a well- balanced population of virtual skeletons. It will take about 5 to 10 years to establish a scientific basis for comparative studies where almost all age classes are adequately represented. Nevertheless, research can be started earlier with smaller sub-samples, or within a specific age group. Previous research (Buk et al., 2012; Milner and Boldsen, 2012) has shown that wide age ranges occur in the group of 30 to 70 years.

Moreover, constant underestimation of the age of individuals older than 40 years could be observed. Therefore, they call for a revision of age indicators commonly used in the group of middle-aged individuals. Additionally, further age indicators should be identified and integrated to augment existing age assessment methods. A sub-sample of adults between 40 and 70 years using the 5-year class will yield about 1200 and could be established within 5 years given technical requirements provide high resolution imaging.

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Figure 1 Age and sex distribution of forensic cases at the University Center of Legal Medicine, Lausanne-Geneva in 2008.

Preconditions

A feasibility study (Grabherr et al., 2009; chapter II.1) has been performed with the objective to investigate the potential of MDCT in the estimation of skeletal age and

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resulting data. Sex was determined by investigating 3D-models of the skull and pelvis. For the age estimation, the complex method according to Nemeskéri et al.

(1960) was applied on 2D- and 3D-reconstructions. The age estimation was refined using additional parameters such as the state of dentition, degeneration of the spine etc. according to the personal experience of the anthropologists.

The study has demonstrated that estimation of sex and age by MDCT is possible and that specific scan parameters are necessary. We encountered the same difficulties as described in the literature concerning the investigation of real skeletal remains (e.g. overestimation of young adults and underestimation of the elderly). As additional difficulties of the virtual approach, artifacts due to gas bubbles in decomposed bodies, and initial technical problems due to the unfamiliar radiological approach have been observed. Nevertheless, “virtual skeletons” present an ideal sample for anthropological studies, because they can be investigated ad infinitum and easily made accessible for specialists around the world.

Before starting such a collection, basic technical conditions should be set up and tested. MDCT-scanning parameters should be optimized to receive high-resolution image quality. A thorough investigation of those technical parameters should be conducted to understand limitations that occur when applying conventional anthropological methods to 2D- and 3D- bone reconstructions. Therefore, we selected anatomical areas of different bone qualities that are commonly examined in age-at-death estimation methods:

• Changes in bone surface – the sacro-iliac joint

Kobayashi (1967) has first introduced the sacro-iliac area of the ilium as age indicator. Then, Lovejoy et al. (1985b) have published a method

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proposed a simplified method based on four traits describing organization and modification of the auricular surface, the apical modification, and changes of the sacro-iliac tuberosity (for details, see chapter II.3, Tab. 7, Fig. 15). We have decided for this method as it is easy applicable and less time consuming. Moreover, the probabilistic approach to assess age-at- death is convincing (Schmitt and Broca, 2000).

• Obliteration of cranial sutures

Anatomists such as Broca have already described cranial suture closure in relation to the aging process in the 19th century (Broca, 1875; for details, see chapter II.3, Fig. 14). Since then endocranial suture closure has been figured out as the more continuous and reliable process (Nemeskéri et al., 1960; Schmitt and Tamaska, 1970). Nevertheless, the validity of this method has been questioned in many studies (e.g., Masset, 1971;

Hershkovitz et al., 1997), but it remains the only possibility of age estimation, if fragmented or cremated skeletal remains are concerned.

Usually the stage of closure of the three main cranial sutures will be observed by sections on the internal and external surface of the skull. By using computed tomography, the opportunity is given not only to document the horizontal but also the vertical progress of suture closure inside the bone.

• Changes in trabecular bone

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Kritschner, 1990; Gehring et al., 2002; Zydek et al., 2011). In the beginning, macerated bones were cut mid-transversally to examine the trabecular bone structure. Later, radiographs were used to determine the age-related bone modification (for details, see chapter II.2, Fig. 9b, 10, 11). However, both methods are limited. Although cut bones permit the examination of the internal bone topology, maceration can cause damage that affects the determination. On the other hand, radiographs are non-invasive but they produce superimposed 2D-images, which can be misinterpreted as anatomical structures cover each other. At present, computed tomography will help us to upgrade the observation potential, because the superimposition of images is eliminated and high-contrast resolution images in axial, coronal, or sagittal planes permit a non-invasive examination of the complete interior bone topology.

Those selected anatomical parts and age indicators cover most of the osseous structures of the skeleton; cortical and trabecular bone as well as different grades of densities are represented. This will be helpful in detecting potential sources of error.

Even though a couple of studies have already been performed on scanned bones until today, not many of them have published an appropriate scanning protocol. Data comparability and method reproducibility thus are hampered. Regarding studies investigating CT imaging of human mummies, O’Brien et al. (2009) have criticized the lack of reproducibility due to insufficient published technical parameters. In a review of the literature, they could show that a clearly defined imaging protocol is missing in 1/3 of the papers (n=31) published between 1979 and 2005. This is in line with our observations concerning the literature selected for this thesis.

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The following observations are not supposed to be representative as they just concern studies selected for this thesis. They are meant as a brief overview that illustrates issues we have been confronted with. While most of the studies (n=40) dealing with MDCT bone imaging in forensic anthropology (published between 2005 and 2015) mention device manufacturer, post-processing software (or at least the workstation) and slice thickness, only eight of them cover most of the parameters shown in Figure 2 (Telmon et al., 2005; Robinson et al., 2008; Guyomarc’h et al., 2012; Villa et al., 2012; Chiba et al., 2013; 2014; Lottering et al., 2013; 2014b).

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Objectives

The aim of this thesis was on the one hand to use medical imaging as a new instrument in medico-legal context to build up a database of virtual skeleton and on the other hand to evaluate on this basis conventional anthropological methods such as sex, age, or stature estimation. Non-destructive insight of objects can help us finding further criteria for method development, and easy data storing gives the opportunity to distribute and to use data multiple times without any material loss.

Thus, we can collect adequate cases to cover successively all age and sex groups to reach a balanced reference series.

We have conducted comparative studies using age estimation methods and bone measurements (see chapter II.2-4) with the aim

• To find appropriate scanning parameters,

• To optimize the scanning protocol established in our feasibility study,

• To perform a direct comparison between the investigation of bones and their digital reconstruction (virtual bones).

Technical understanding of scanning parameters (such as tube voltage and current, spatial resolution, or reconstructed slice thickness) might be useful, because wrong adjustment can influence imaging results. These factors and error sources should be taken into consideration when evaluating anthropological methods by the aid of virtual bones.

Those basic technical conditions should be accomplished before we can turn toward future objectives such as

• Building up a large collection of virtual skeletons with known age, sex,

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• Evaluating existing methods of age, sex and stature estimation,

• Developing new methods about the biological profile of human skeletal remains,

• Performing studies on bone pathologies and trauma analysis.

Such a database together with adequate technical conditions will deliver new ideas and inspiration to conventional anthropological methods.

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II. Scanning Bones

II.1 Estimation of sex and age of “virtual skeletons” – a feasibility study The article has been written by S. Grabherr. T. Uldin contributed to study design, data acquisition, discussion and revision of the article.

The article has been published in European Radiology 19 (2009), pp 419-429.

MDCT provides a comfortable opportunity for anthropological-osteological investigations. In only one session at the workstation, internal and external structures can be examined non-invasively, measurements can easily be taken from the reconstructed bone, and pictures can be taken of the region of interest. Finally, all data can be recorded for further studies. In contrast to the commonly used scanning protocol in post mortem whole-body CT, high-resolution imaging was chosen as precondition to adequately examine skeletal details. Therefore, we decided to work with thinner slice thickness, thinner increment and a bone reconstruction filter. Our results let us conclude that the implementation of MDCT is a useful diagnostic tool to investigate the entire skeleton.

During this feasibility study, we developed additionally the idea to set up an anthropological database by means of MDCT data using the potential of daily routine post mortem MDCT. However, further research is needed on technical conditions to guarantee comparable quality between virtual and real bones.

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In recent years, modern cross-sectional imaging techniques have revolutionized forensic medicine. Magnetic resonance (MR) imaging and especially multi-detector computed tomography (MDCT) are becoming more and more widely used for post- mortem examinations (Dirnhofer et al., 2006). Computed tomography (CT) systems have already been installed in institutes of forensic medicine all over the world, and in the future, this trend will continue (Grabherr et al., 2007). The advantage of having access to CT and MR can also influence other specialists working in collaboration with institutes of forensic medicine. In this context, the Institute of Forensic Medicine of the University of Lausanne is working on creating an “anthropological database”

that should contain data from many cadavers which have been examined by CT.

These data will consist of “virtual skeletons” with well-documented age, sex, illnesses, origin, etc. that can be used to perform anthropological studies to optimize anthropological methods or to develop new techniques.

This article deals with a feasibility study that demonstrates how CT can be used for anthropological purposes. In the context of the Virtopsy project, the potential of MDCT to perform anthropological estimation of skeletal sex and age was evaluated.

The aim of this first study was to show if different parts of the skeleton can be visualized by MDCT in a quality that allows examinations as they are performed on real skeletons. Therefore, MDCT data of 22 cases were collected at the Institute of Forensic Medicine in Bern. A special CT protocol that should allow detailed high- resolution imaging with reconstruction of high quality three-dimensional (3D) models was developed. The obtained “virtual skeletons” were examined by three anthropologists with different professional experience.

All the disposable methods for age estimation lead to an appraisal of the biological

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Examples of well-established methods for age estimation on adult skeletons are aspartic acid racemization (Ritz-Timme et al., 2000b) and tooth cementum annulation (Wittwer-Backofen et al., 2004), both techniques that are not adaptable for our question. For a first appraisal of the age, we decided to use the complex method of Nemeskéri et al. (Nemeskéri et al., 1960). Despite the criticism concerning this method (Kemkes-Grottenthaler 1993; Rösing et al., 2007), it seemed to us to be the most interesting choice for our question because it consists of a unique multi-factor concept, including four different skeletal age parameters, which are combined and put in relation to each other. This aspect was important, as the goal of this study was to investigate different parts of the skeleton and not just one parameter, as has already been reported (Verhoff et al., 2008).

The complex method according to Nemeskéri et al. (1960) includes the following parameters: (1) the endocranial obliteration of the sutures; (2) the structure of the spongiosa of the proximal humerus; (3) the proximal femur; (4) the texture of the symphyseal surface of the pubic bone. Optimally, the deviation should be ±2.5 years (confidence ca. 80–85%). After assigning a state to each parameter as depicted in (Nemeskéri et al., 1960), the estimated age range can be withdrawn from tables published by Ferembach et al. (1979) and Sjøvold (1975). In German speaking regions, the method according to Nemeskéri and co-workers is widely applied by anthropologists, especially those who are working with historical skeletal materials.

To test the work on virtual bones, the involved anthropologists preferred to apply this

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of the symphysis, which is used for this kind of age estimation, is nearly impossible in individuals of more than 40 years old, whereas the complex method allows differentiation up to an age of over 50 years. These factors contributed to our decision to use the Nemeskéri method in this study despite the criticism concerning this method.

Acsádi and Nemeskéri (1970) emphasized that an oversimplified mechanistic employment of the method should be avoided and that the final age diagnosis should be established in a most circumspect manner. In our study, the age estimated by the complex method was used as a starting point for further estimations. These depended mostly on the experience and preferences of the three observers and did not follow rules of specific methods. Characteristics of interest here were the obliteration of ectocranial sutures, degenerative joint disease, degree of epiphyseal fusion, presence of osteophytes, the ossification of the rib and laryngeal cartilage, degeneration of the spine, the state of the dentition and the texture of the clavicle. In the most general of terms, the absence of degenerative changes, osteophytes and advanced ossification of epiphyses, sutures and cartilages is indicative of a younger age, their presence however points towards a more mature age. Such age changes are highly individual, though, and depend on different factors like lifestyle and genetic disposition. The assessment of these skeletal changes and the weight attached to them depends on the observer’s judgement. Thus, the final age estimation is a process of weighing and balancing, therefore including many factors that cannot be assessed by an exact method. Regarding these aspects, an aggregated interpretation (final estimation) was performed by each observer which revealed the estimated age of each individual.

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Materials and methods

Subjects

The study was performed on 22 blinded cases of the Institute of Forensic Medicine in Bern. The cases were chosen by the following criteria: (1) known and confirmed age at death, (2) intact skeletal system. The study group was composed of seven female and 15 male corpses, representing ages between 17 and 92 years at the time of death. Cause of death was either intoxication (drugs and/or medicine) or sudden death due to cardiac insufficiency.

MDCT

MDCT was performed on a Siemens Somatom Sensation 6 unit, using a special CT protocol including high-resolution imaging of regions relevant for the complex analysis: skull, shoulder girdle including the upper half of the humeri, the symphysis pubis and the upper halves of the femora (Fig. 3).

CT parameters were 0.63-mm slice width, 6×0.5-mm detector-collimation and a reconstruction increment of 0.5-mm (tube voltage: 130 kV; effective mAs: 90;

radiation dose: 12.24 mGy). Reconstructions were performed using a kernel of B30 (soft-tissue reconstruction) andB90 (bone reconstruction).

Virtual anthropology : the forensic approach

Thesis

Reference

Virtual anthropology : the forensic approach

Virtual Anthropology – The Forensic Approach

Acknowledgements

Abstract

Résumé

Table of contents

List of Figures and Tables

I. Introduction

II. Scanning Bones