New approaches in the virtual reconstruction of fragmented specimen

Das Hauptaugenmerk dieser Arbeit liegt auf der virtuellen Rekonstruktion von Schädeln, die sich durch das Fehlen eines großen Teils der Schädelknochen auszeichnen. Mithilfe von Methoden der virtuellen Anthropologie und Geometrischen Morphometrie kann dabei eine Vielzahl von Problemen konfrontiert werden, die während der Rekonstruktion von fragmentierten fossilen Schädeln entstehen können. Denn jede Schädelrekonstruktion weisst generell eine gewisse Ungenauigkeit auf. Diese wird von verschiedenen Faktoren beeinflusst, z.B. Größe der fehlenden Schädelteile oder der Rekonstruktionsmethode. Ein Schwerpunkt dieser Arbeit liegt deshalb in der Untersuchung der Auswirkungen verschiedener Faktoren auf die Ungenauigkeit fossiler Rekonstruktionen mithilfe von landmarks und semilandmarks. Darüber hinaus werden neue Ansätze für die anatomische Rekonstruktion von stark beschädigten Schädeln eingeführt. Bei der Rekonstruktion von fossilen Schädelfragmenten in einer virtuellen Umgebung wird jeder einzelne Schritt in einem ausführlichen Protokoll gespeichert. Dies ermöglicht die Erstellung einer großen Anzahl von verschiedenen Rekonstruktionen. Da eine Rekonstruktion niemals perfekt sein wird, berücksichtigt dieser Ansatz das mangelnde Wissen darüber, wie das Original-Indiviuum wirklich aussah. Mit anderen Worten zeichnet sich jede Rekonstruktion durch einen gewissen Grad an Ungenauigkeit aus. Die Ermittlung dieser Ungenauigkeit ist umso wichtiger, da heute hohe Maßstäbe an die Qualität von virtuellen Modellen gestellt werden, die in unterschiedlichen Studien der Ontogenie, Phylogenie und Biomechanik eingesetzt werden. Ich veranschauliche diese Ansätze durch die Rekonstruktion mehrerer virtuell fragmentierter Individuen und wende die gewonnenen Informationen unter anderem in der Rekonstruktion des Australopithecus afarensis Individuums A.L. 444-2 an. Desweiteren untersuche ich die morphologische Integration im kraniofazialen Komplex von Individuen der Überfamilie Hominoidea, um Kovariationsmuster aufzuzeigen, die während der Schätzung der Ungenauigkeit von anatomischen Rekonstruktionen von potenzieller Hilfe sein konnten.The main theme of this thesis is how different scenarios of missing data estimation influence the uncertainty of virtual reconstructions. Using a combination of tools from Virtual Anthropology and Geometrics Morphometrics, a variety of problems is approached comprising major problems that arise during the anatomical reassembly of fragmented fossil crania and the geometrical reconstruction of missing data. The focus is on the quantitavive description of accuracies and uncertainties in fossil reconstructions using landmarks and semilandmarks from different reference samples. Furthermore, new approaches for the anatomical reconstruction of severly damaged crania are introduced. When dealing with the reassembly of fragments in a virtual environment, every single step can be saved in a detailed protocol and used as a basis for subsequent modifications. This creates a large number of different reconstructions, considering the uncertainty of the reconstruction itself. Reconstructions of incomplete fossil specimens are needed in varying contexts from studies of ontogeny, phylogeny or biomechanics. I exemplify these approaches by reconstructing several virtually fragmented specimens from extant and extinct species, and applying part of this information to the Australopithecus afarensis specimens A.L. 444-2. Furthermore I investigate morphological integration in the hominoid craniofacial complex, showing patterns of covariation that could be of potential help estimating the uncertainty in the anatomical reconstruction of fragmented specimens

IN-SITU COMPRESSION TEST OF ARTIFICIAL BONE FOAMS IN CONTROLLED ENVIRONMENT USING X-RAY MICRO-COMPUTED TOMOGRAPHY

In this study, we investigated specimens of artificial bone foams, developed by the research group for surgical simulators at the UAS Linz, which are used to mimic the haptic feedback of physiologic and pathologic bone for more realistic surgery training. Specimens with two kinds of mineral filler material as well as different amounts of foaming agent were tested in an environmental in-situ loading stage developed by the ITAM CAS and scanned via X-ray micro-computed tomography. In this in-situ stage, specimens can be immersed in liquid and tested under temperature-controlled conditions. Consequently, a total amount of 12 specimens was subjected to compression loading; half of them immersed in water at 36.5◦C and half in dry condition. Results showed that there is no significant influence of liquid immersion to the compression outcome. However, foams with less amount of foaming agent appeared to have smaller pores resulting in higher compression strength

BASIC BIOMECHANICAL CHARACTERIZATION OF POLYURETHANE BASED ARTIFICIAL CANCELLOUS STRUCTURES

The main goal of this study is to validate elementary mechanical parameters of a newly designed open-cell foam. The purpouse for investigating artificial material is to approach the properties of the human bone in the case of its adequate replacement. Investigated material can be also used as an artificial bone to train surgical procedures and to improve the skills of the surgeons. Four sets of the foam with different chemical composition were subjected to an uniaxial quasi-static loading to describe basic mechanical behaviour of these samples. Based on these experiments, the stress-strain diagrams were created as a comparative tool including calculation of the effective Young’s modulus. The acquired knowledges will be used as input parameters of a follow-up study aimed at describing the morphology of presented structures and their response to mechanical experiments. A distortion effect of porosity on the results is not considered in this study

Fast continuous in-situ XCT of additively manufactured carbon fiber reinforced tensile test specimens

The reinforcement of fused filament fabricated (FFF) components with continuous fibers allows for high versatility in the design of mechanical properties for a specific applications needs. However, the bonding quality between continuous fibers and the FFF matrix material has high impact on the overall performance of the composite. To investigate the bonding quality within additively manufactured (AM) continuous fiber reinforced specimens, tensile tests have been performed which revealed a sudden reduction in tensile stress, that most likely was not related to actual rupture of continuous fibers. Consequently, within this work we will expand upon these findings and present results of fast on-the-fly in-situ investigations performed on continuous carbon fiber reinforced specimens of the same AM build. During these investigations, specimens are loaded under the same conditions while fast XCT scans, with a total scan time of 12 seconds each, were performed consecutively. The resulting three-dimensional image data reveals internal meso- and macro-structural changes over time/strain to find the cause of the aforementioned reduction in tensile stress

Fast continuous in-situ XCT of additively manufactured carbon fiber reinforced tensile test specimens

The reinforcement of fused filament fabricated (FFF) components with continuous fibers allows for high versatility in the design of mechanical properties for a specific applications needs. However, the bonding quality between continuous fibers and the FFF matrix material has high impact on the overall performance of the composite. To investigate the bonding quality within additively manufactured (AM) continuous fiber reinforced specimens, tensile tests have been performed which revealed a sudden reduction in tensile stress, that most likely was not related to actual rupture of continuous fibers. Consequently, within this work we will expand upon these findings and present results of fast on-the-fly in-situ investigations performed on continuous carbon fiber reinforced specimens of the same AM build. During these investigations, specimens are loaded under the same conditions while fast XCT scans, with a total scan time of 12 seconds each, were performed consecutively. The resulting three-dimensional image data reveals internal meso- and macro-structural changes over time/strain to find the cause of the aforementioned reduction in tensile stress

Comparing 3-Dimensional Virtual Methods for Reconstruction in Craniomaxillofacial Surgery

none2Purpose: In the present project, the virtual reconstruction of digital osteomized zygomatic bones was simulated using different methods. Materials and Methods: A total of 15 skulls were scanned using computed tomography, and a virtual osteotomy of the left zygomatic bone was performed. Next, virtual reconstructions of the missing part using mirror imaging (with and without best fit registration) and thin plate spline interpolation functions were compared with the original left zygomatic bone. Results: In general, reconstructions using thin plate spline warping showed better results than the mirroring approaches. Nevertheless, when dealing with skulls characterized by a low degree of asymmetry, mirror imaging and subsequent registration can be considered a valid and easy solution for zygomatic bone reconstruction. Conclusions: The mirroring tool is one of the possible alternatives in reconstruction, but it might not always be the optimal solution (ie, when the hemifaces are asymmetrical). In the present pilot study, we have verified that best fit registration of the mirrored unaffected hemiface and thin plate spline warping achieved better results in terms of fitting accuracy, overcoming the evident limits of the mirroring approach.noneStefano Benazzi;Sascha SenckStefano Benazzi;Sascha Senc

Influence of Process Energy on the Formation of Imperfections in Body-Centered Cubic Cells with Struts in the Vertical Orientation Produced by Laser Powder Bed Fusion from the Magnesium Alloy WE43

The low specific density and good strength-to-weight ratio make magnesium alloys a promising material for lightweight applications. The combination of the properties of magnesium alloys and Additive Manufacturing by the Laser Powder Bed Fusion (LPBF) process enables the production of complex geometries such as lattice or bionic structures. Magnesium structures are intended to drastically reduce the weight of components and enable a reduction in fuel consumption, particularly in the aerospace and automotive industries. However, the LPBF processing of magnesium structures is a challenge. In order to produce high-quality structures, the process parameters must be developed in such a way that imperfections such as porosity, high surface roughness and dimensional inaccuracy are suppressed. In this study, the contour scanning strategy is used to produce vertical and inclined struts with diameters ranging from 0.5 to 3 mm. The combination of process parameters such as laser power, laser speed and overlap depend on the inclination and diameter of the strut. The process parameters with an area energy of 1.15–1.46 J/mm2 for struts with a diameter of 0.5 mm and an area energy of 1.62–3.69 J/mm2 for diameters of 1, 2 and 3 mm achieve a relative material density of 99.2 to 99.6%, measured on the metallographic sections. The results are verified by CT analyses of BCCZ cells, which achieve a relative material density of over 99.3%. The influence of the process parameters on the quality of struts is described and discussed

Immunological and morphological analysis of heterotopic ossification differs to healthy controls

Abstract Background Formation of lamellar bone in non-osseus tissue is a pathological process called heterotopic ossification. It is the aim of this study to analyse the morphology and immunological status of patients with heterotopic ossification compared to individual healthy persons. Methods Human bone marrow and blood samples were obtained from 6 systemically healthy individuals and 4 patients during resection of heterotopic ossification from bone at hip arthroplasty. Bone was fragmented and treated with purified collagenase. Immunofluorescence surface staining was performed and analyzed with flow cytometry. Microcomputed tomography scanning was done performed at a resolution of 11 and 35 μm isometric voxel size respectively using a two different cone beam X-computer tomography systems and a microfocus X-ray tube. Subsequently the volume data was morphometrically analysed. Results The monocytes, stem cells, stroma cells and granulocytes progenitor cells were strongly reduced in the heterotopic ossification patient. Additionally a significant reduction of stromal stem cells cells and CD34 positive stem cells was observed. The frequency of NK-cells, B cells and T cells were not altered in the patients with heterotopic ossification compared to a healthy person. Micromorphometric parameters showed a lower content of mineralized bone tissue compared to normal bone. Mean trabecular thickness showed a high standard deviation, indicating a high variation in trabecular thickness, anisotropy and reducing bone strength. Conclusions This work shows altered immunological distribution that is accompanied by a low decrease in bone volume fraction and tissue mineral density in the heterotopic ossification sample compared to normal bone. Compared to healthy subjects, this might reflect an immunological participation in the development of this entity