Hélène Coqueugniot

Three-dimensional computer-assisted craniometrics: A comparison of the uncertainty in measurement induced by surface reconstruction performed by two computer programs

Digital investigation of anthropological material through computed tomography (CT) offers several new opportunities in morphometrics. However, an object measured with computer-assisted methods does not necessarily exactly match the original one. The scanning and surface reconstruction of the object induce some alterations, and data acquisition is prone to measurement uncertainty. The purpose of this research is to evaluate the intra- and inter-observers variations in medical CT scan measurements of a known-size phantom and two dry crania. Two software packages, AMIRA and Treatment and Increased Vision for Medical Imaging (TIVMI), which use different techniques of surface reconstructions, were compared. The mean difference between the measurements was lower for TIVMI, using an objective algorithm based on the half-maximum height (HMH) protocol in three dimensions (3D). AMIRA can induce up to a 4% error in known measurements and 5% uncertainty in dry skull measurements. This study emphasises the risk of object shape alteration in each step of its digitisation.

Anatomical Placement of the Human Eyeball in the Orbit—Validation Using CT Scans of Living Adults and Prediction for Facial Approximation*

Abstract:u2002 Accuracy of forensic facial approximation and superimposition techniques relies on the knowledge of anatomical correlations between soft and hard tissues. Recent studies by Stephan and collaborators (6,8,10) reviewed traditional guidelines leading to a wrong placement of the eyeball in the orbit. As those statements are based on a small cadaver sample, we propose a validation of these findings on a large database (nu2003=u2003375) of living people. Computed tomography scans of known age and sex subjects were used to collect landmarks on three‐dimensional surfaces and DICOM with TIVMI. Results confirmed a more superior and lateral position of the eyeball relatively to the orbital rims. Orbital height and breadth were used to compute regression formulae and proportional placement using percentages to find the most probable position of the eyeball in the orbit. A size‐related sexual dimorphism was present but did not impact on the prediction accuracy.

3D surface reconstruction using HMH algorithm

3D surface reconstruction using the half maximum height (HMH) algorithm is a method to extract a surface of interest from a voxel data set. It is based on the original HMH method applied to each voxel of the segmented surface to reconstruct. From a 3D voxel grid, an initial segmentation is computed to extract a discrete surface of interest. For each of these voxels, HMH computes a segmentation and an orientation. The result of this step is then processed using a marching cube-like algorithm. The two major advantages of this method are the precision of the surface extraction and its non user-dependancy.

Discriminant study of the development of the mandibular units in a neural reference system

The mandible is a complex osteological structure composed of distinct units integrated into a single bone around the director axis of the mandibular nerve. In this study of the mandibular development, we use a method that synthesizes the contributions of each sub-unit, using the mandibular canal as reference system. This novel approach results in new informations and confirms the leading role of the mandibular nerve and of its curve in mandibular development. It would seem to be possible to explain a major part of mandibular development by the role of the nerve as guide.

Le dénombrement des sujets immatures dans les sépultures collectives : l’exemple néolithique de « La Truie Pendue » (Passy, Yonne)

RésuméL’examen des restes immatures de la sépulture collective néolithique récent de « La Truie Pendue », située à Passy dans le département de l’Yonne, a permis de développer une méthode de dénombrement des sujets immatures adaptée à une sépulture collective comprenant de nombreux restes fragmentés. En plus d’une estimation du nombre minimum de sujets immatures, cette méthode propose une répartition par classe d’âge de cette population immature. Les perspectives offertes pour appréhender la place des enfants dans les sépultures collectives néolithiques et dans ces sociétés se trouvent multipliées. Ainsi, les résultats obtenus pour « La Truie Pendue » ont permis de mettre en oeuvre une étude du recrutement qui semble indiquer que les sujets immatures ont eu accès à la sépulture dans des proportions compatibles avec un schéma de mortalité « naturelle ».AbstractIn this article, we describe a method to estimate the minimum number of immature individuals (MNI) in fragmentary and commingled skeletal assemblages. The method uses the principles of exclusion traditionally used in anthropological studies: overlapping bone and age-related size. We applied these principles to the anatomical features of bones and then to complete skeletons to estimate the MNI. By calculating the MNI with this protocol, we were also able to assess the age composition of the sample. Our analysis of the immature skeletal assemblage from the Neolithic mass grave known as “La Truie Pendue” (at Passy in Northern France) showed that the sample was made up of 30 infants. However, MNI estimations are limited by the lack of reliable methods to assess the ages of fragmentary immature remains. Having estimated the MNI and age composition of this assemblage, we were then able to conduct a palaeodemographic analysis. This showed that the age-specific mortality estimated at “La Truie Pendue” tallies with natural mortality. This might suggest that at least some immature individuals were buried in a mass grave as the adults were. However, only by studying other Neolithic mass graves will we be able to offer a hypothesis for the funerary and social treatment of children during the Neolithic.