Andreas Staude

Achieving Traceability of Industrial Computed Tomography

Achieving traceability is crucial for complex measurement techniques, especially for coordinate measuring machines (CMMs). For CMMs using tactile probes, traceability can for certain measurements be achieved using model-based uncertainty budgets. Up to now, uncertainty simula-tions could be used applicable only for tactile CMM measurements of regular geometries, but are available as an add-on for different CMMs. This procedure is accepted by guidelines and inter-national standards (VDI/VDE 2617-7, supplement 1 [1] to GUM). Furthermore, empirical ap-proaches to assess the measurement uncertainty by means of calibrated workpieces or prior know-ledge exist or are under development. These approaches can as a matter of principle also be used for CMMs featuring computed tomography (CT). In this paper, the empirical assessment of the mea-surement uncertainty of the upcoming measurement technology CT [2, 3] will be discussed uniting the present approaches and the current knowledge, with the focus being on the applicability of con-cepts for users in industry. For this purpose, the influences on dimensional CT measurements are analyzed and evaluated, taking the measurement data of a current industrial micro CT system as a basis.

Synchrotron radiation and laboratory micro X-ray computed tomography—useful tools for the material identification of prehistoric objects made of ivory, bone or antler

Archaeological bone, ivory and antler, as well as objects manufactured from them, are largely studied to extract as much information as possible from these materials. Among others, one key question in archaeology is the exact identification of the material. Even if the identification of different kinds of osseous material seems to be trivial in many cases, it can be a difficult issue when small, heavily carved and more or less altered ancient objects are concerned. This study was focused on the determination of parameters allowing the distinction of archaeological ivory, bone and antler in order to identify the raw material used for the manufacture of prehistoric objects. The high performance of synchrotron radiation (SR) and laboratory-based micro X-ray computed tomography (microCT), providing highly resolved three-dimensional information on the micromorphology, permitted the establishment of such distinctive features of modern references of ivory, antler, land mammal and whale bones: ivory shows characteristic tubular pores with a diameter of about 1 to 2 μm, bone and antler show typical osteon structures. In our measured references, antler shows on average larger and more elongated shaped pores of the osteons compared to terrestrial mammal bone. This feature however depends very much on the original localization of the studied sample within the antler. Whale bones can be distinguished from the other osseous materials by a cancellous, osteoporotic-like structure with irregularly distributed rounded porosities with diameters reaching up to 500 μm. These characteristics have also been tested on determined Palaeolithic fragments, as diagenetic changes during burial have to be considered and may lead to the modification of the parameters established on the basis of modern bone references. In general, the chemical composition of bone objects can change drastically over time while micromorphological features, as evidenced by microCT, seem to be less susceptible to such alterations. In addition, microCT enables the comparison of inner and possibly less altered parts of the objects, and can be considered as completely non-destructive for small mineralised prehistoric objects. In this study, specific morphological features allowing the distinction of ivory and of whale bone from other bone and antler material were determined, even for altered materials dating back to Palaeolithic periods. Thus, we provide, in addition to archaeozoological, chemical and isotopic markers, a new non-destructive tool to identify some raw materials used for the fabrication of osseous objects ranging from recent to prehistoric periods.

Flint arrowhead embedded in a human humerus from the Bronze Age site in the Tollense valley, Germany – A high-resolution micro-CT study to distinguish antemortem from perimortem projectile trauma to bone

The Bronze Age site in the Tollense valley, Germany, has yielded thousands of human and animal bones and a number of archaeological artifacts. Several of the human bones exhibit blunt and sharp force lesions, and the assemblage has been interpreted as representing victims of a large scale conflict. One of the earliest finds is a human humerus with an embedded flint arrowhead. Alleged signs of healing initially reported for this humerus based on clinical CT imaging were interpreted as evidence of an antemortem lesion. The present study, using micro-CT imaging, revealed that the arrowhead lesion in the humerus, contrary to the previous interpretation, shows no signs of healing. The structure previously assumed to represent a sclerotic margin around the wound canal was shown to actually represent compacted trabecular debris. Thus, our re-analysis of the specimen led to a re-classification of the arrow wound as a perimortem lesion. The findings of the present study demonstrate the value of micro-CT imaging as a non-destructive method for obtaining information on the nature of bone lesions and healing reactions critical for the reconstruction of interpersonal conflict scenarios in the past.

Non-sexual abdominal appendages in adult insects challenge a 300 million year old bauplan

Summary Despite their enormous diversity, the bauplan of adult winged insects (pterygotes) is remarkably conservative since the Lower Devonian: a five-segmented head, a three-segmented thorax with three pairs of walking legs and an eleven-segmented abdomen without any non-sexual appendages [1,2]. The only known exceptions are the abdominal appendages of adult male sepsid flies on the fourth segment; however, these are also used as copulatory organs and are supposedly maintained through sexual selection [3]. Here, we report a rod-like paired appendage from the third and fourth abdominal segments in adults of the Southeast-Asian Hemiptera taxon Bennini (Figure 1A,B; Supplemental information). These are fully musculated, innervated, and movable and bear highly organized sensory and secretory units. The appendages, termed LASSO (lateral abdominal sensory and secretory organs), are consistent in topology and structure in all species studied and not sexually dimorphic. The existence of these non-sexual abdominal appendages reveals the potential of the 300 million year old conserved bauplan of insects.

Measurement of micro gears: comparison of optical, tactile-optical, and CT measurements

Micro gears are applied in an increasing quantity in many applications. Therefore, precise measurements are of growing importance to ensure their quality. This contribution describes the measurement of gears of a micro planetary gear set with a tactile probe, a tactile-optical probe, an optical sensor, and computed tomography (CT). For the tactile measurements, a high precision piezoresistive microprobe was used. A so-called fiber probe was applied for tactile-optical measurements. This probe applies image processing to determine the position of the tactile probing element. For all tactile and tactile-optical measurements, single point probing was used. The optical measurements were carried out with an imaging sensor based on focus variation. Due to limited accessibility, on some gears not all regions could be measured by the optical sensor and the tactile-optical probe. In contrast to this, with CT the whole part could be measured with high point density. We used a micro-CT system and carried out measurements with Synchrotron-CT. All the sensors used deliver measurement data in Cartesian coordinates. It is a challenge to transfer these data into coordinates in which gear parameters are defined. For this, special attention must be paid to the determination of the gear axis and to the orientation of the teeth. The applied procedures are detailed for different micro gears. The comparison between data of different measurements was carried out successfully. The deviations between the CT data and the tactile or tactile-optical data lie in the range of only a few micrometers.

Fusion multimodaler Daten am Beispiel eines Mikrolinsen-Arrays (Multimodal Data Fusion Exemplified on a Microlens Array)

Die Zusammenführung von Messinformationen aus verschiedenen Verfahren ermöglicht eine einheitliche und umfassende Charakterisierung von 3D-Geometrien und deren Kenngrößen. Es werden Methoden zur Verarbeitung, Vereinigung und Auswertung von multimodalen und multiskaligen Messdaten vorgestellt und anhand beispielhafter Messungen konkretisiert. Ein eingesetzter Probenkörper, basierend auf einem Mikrolinsenarray, wird mittels taktiler, konfokaler, interferometrischer Verfahren sowie Röntgentomographie und Streulicht untersucht. Anhand der resultierenden Messdatensätze werden Rauheitsspektren berechnet und diese wiederum zu einem gemeinsamen Rauheitsspektrum des Probenkörpers fusioniert. Nach der Registrierung der Datensätze mittels einer Pyramidenstruktur und Referenzmarken wird ein multimodaler Vergleich der verwendeten Messgeräte möglich. Merging information from different measurement procedures enables consistent and extensive characterization of 3D geometries and features. Methods of processing, merging, and analyzing multimodal measurement data are shown and used with exemplary measurements. The test specimen, based on a microlens array, is examined by means of atomic force and confocal microscopy, white-light interferometry, computed tomography, and angle-resolved scattering. The power spectral densities of selected data sets are evaluated and merged to a single power spectral density of the test specimen. The different data sets are registered using a reference structure with reference markers, thus enabling a multimodal comparison of the respective measurement instruments.

Perimortem Lesions on Human Bones from the Bronze Age Battlefield in the Tollense Valley: An Interdisciplinary Approach

The Tollense Valley extended site (northeast Germany) is the only known battlefield from the European Bronze Age. It has yielded a large number of human remains showing traces of violence, along with animal remains and weapons. The chapter discusses the results of new, interdisciplinary research focusing in particular on the penetrating injuries, which have yielded some of the most important information for reconstructing the Tollense Valley conflict scenario. This chapter aims to demonstrate how specific questions regarding the characteristic features of the injuries, the possible type of weapon, and the direction of the attack can be answered by using non-destructive high-resolution imaging and 3D reconstruction combined with experimental weapon testing. While experimental weapon testing is crucial for providing information concerning the injury patterns and weapon types, it may not offer any clues as to whether the injury originates from a stab or a shot. In order to address this problem, this chapter discusses a method enabling the secure identification of the weapon used in such ambiguous cases. This research allows discrimination between arrow and spearheads and thus between ranged and handheld weapons. This is especially important for the interpretation of the Tollense Valley conflict scenario, for which this study confirms that nonstandardized weapons were utilized on the battlefield.