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Precautions in the generation of surfaces from CT images should be the rule. Two different data sets of the bust of Nefertiti and additional data from an industrial CT scanner will show the conflicts that arise when defining a surface. The recent trend in CT is to extract surfaces from CT measurements which can compete with the accuracy of tactile measurements. As CT is complicated by artefacts, a lot of precautions need to be taken in order to get exact results. More errors are introduced, if the surface of an object made from different dense materials is calculated. A publication in April 2009 of "Radiology" dealt with the surface of the stone behind the stucco layer of the famous bust of the Egyptian Queen Nefertiti in the Ägytische Museum Berlin. Using this data, we will show the different problems that arise from inadequate image processing. Furthermore, a detailed comparison of the two CT measurements made 14 years apart is given. Conclusions: Respect the traps in virtual imaging.
Ein dreidimensionaler Prüfkörper für die Lunkererkennung in Gussteilen mittels Computertomographie
(2010)
Since the advent of industrial computed tomography (CT), this new analysis method has been used also for the investigation of objects of cultural heritage and art. CT provides the possibility to determine the inner and outer surfaces and to investigate the material structure without causing damage to the valuable objects.
In this talk I will present examples of measurements performed at BAM, which demonstrate what CT can do for objects of diverse materials and for different objectives.
Die Computertomographie (CT) ist in der Medizin als Standardtechnik etabliert, in der zerstörungsfreien Prüfung wird sie zunehmend angewendet, in einzelnen Fällen sogar als Referenzverfahren eingesetzt. Gegenwärtig ist eine starke Zunahme von Anwendungen der CT in der Materialcharakterisierung zu verzeichnen. Zudem werden weitere moderne 3D-Techniken für werkstoffwissenschaftliche Fragestellungen genutzt, um die Mikrostruktur - auch in situ (z.B. Druck, Temperatur) - aufzuklären. Hier werden neben der konventionellen Absorptions-CT auch die Potenziale der Refraktions-CT zur Beantwortung prozesstechnischer sowie werkstofflicher Fragestellungen aufgezeigt, die ein „ganzheitliches Bild“ des jeweiligen Werkstoffs zum Ziel haben.
Numerical measurement uncertainty determination for dimensional measurements of microparts with CT
(2016)
Up to now, the only standardized method to determine the measurement uncertainty for computed tomography (CT) is to use calibrated workpieces as specified in the Guideline VDI/VDE 2630 Part 2.1. This paper discusses a promising numerical method for uncertainty determination with help of a virtual metrological CT (VMCT). It gives an explanation of the adjustments, the input parameters and the execution of the simulation. Furthermore, it discusses the first results of uncertainty determination compared to the method of using calibrated workpieces with the aid of two example cases.
In this paper we present the results of imaging studies of ancient Egyptian metallic artifacts using micro-Computed Tomography (micro-CT). Micro-CT is a non-destructive imaging method with high spatial resolution, which enables the examination of the internal structure of objects. It is thus especially suitable for the investigation of cultural heritage and archaeological findings, when it is not possible to sample or difficult to manipulate the object. Using specialized software for 3D visualization and segmentation, data sets of two objects were analyzed. We gained a clear view of the inner structure of a metallic archaeological artifact from the necropolis of Abusir el-Meleq, which is believed to be very ancient in the Egyptian archaeological context (from the Predynastic Era), and were able to distinguish its different omponents under the thick layers of external concretions. These components give hints about the production technology of the object. We also investigated the contents of a closed metal box found near Abusir dated to the Late/Greco-Roman Period. The identified Content corresponds either to sediments or to mineral remains of the original content of the box. Both artifacts are from excavations conducted in Egypt and are part of the archeological collection of the Ägyptisches Museum und Papyrussammlung in Berlin.