Over the past decade computed tomography (CT) with conventional x-ray sources has evolved from an imaging method
in medicine to a well established technology for industrial applications in fields such as material science, light metals and
plastics processing, microelectronics and geology. By using modern microfocus and nanofocus X-ray tubes, parts can be
scanned with sub-micrometer resolutions. Currently, micro-CT is a technology increasingly used for metrology
applications in the automotive industry. CT offers big advantages compared with conventional tactile or optical
coordinate measuring machines (CMMs). This is of greater importance if complex parts with hidden or difficult
accessible surfaces have to be measured. In these cases, CT offers the advantage of a high density of measurement
points and a non-destructive and fast capturing of the sample's complete geometry.
When using this growing technology the question arises how precise a μCT based CMM can measure as compared to
conventional and established methods for coordinate measurements. For characterizing the metrological capabilities of a
tactile or optical CMM, internationally standardized parameters like length measurement error and probing error are
defined and used. To increase the acceptance of CT as a metrological method, our work seeks to clarify the definition
and usage of parameters used in the field of metrology as these apply to CT. In this paper, an overview of the process
chain in CT based metrology will be given and metrological characteristics will be described.
For the potential user of CT as 3D metrology tool it is important to show the measurement accuracy and repeatability on
realistic samples. Following a discussion of CT metrology techniques, two samples are discussed. The first compares a
measured CT Data set to CAD data using CMM data as a standard for comparison of results. The second data second
realistic data set will compare the results of applying both the CMM method of measurement and the CT method of
measurement within the same CT data set. A comparison of these results to the data obtained by means of CT shows
that state of the art high resolution CT can provide measurement accuracy on the order of established coordinate
Nowadays, X-ray tube-based high-resolution CT systems are widely used in scientific research and industrial applications. But the potential, convenience and economy of these lab systems is often underestimated. The present paper shows the comparison of sophisticated conventional μCT with synchrotron radiation-based μCT (SRμCT). The different aspects and characteristics of both approaches like spatial and density resolution, penetration depth, scanning time or sample size is described in detail. The tube-based μCT measurements were performed with a granite-based
nanotom®-CT system (phoenix|x-ray, Wunstorf, Germany) equipped with a 180 kV - 15 W high-power nanofocus® tube with tungsten or molybdenum targets. The tube offers a wide range of applications from scanning low absorbing samples in nanofocus® mode with voxel sizes below 500 nm and highly absorbing objects in the high power mode with focal spot and voxel sizes of a few microns. The SRμCT measurements were carried out with the absorption contrast set-up
at the beamlines W 2 and BW 2 at HASYLAB/DESY, operated by the GKSS Research Center. The range of samples examined covers materials of very different absorption levels and related photon energies for the CT scans. Both quantitative and qualitative comparisons of CT scans using biomedical specimens with rather low X-ray absorption such
as parts of the human spine as well as using composites from the field of materials science are shown.
Investigations of bony tissues are often performed using micro computed tomography based on X-rays, since the calcium distribution leads to superior contrast. Osteoporotic bone, for example, can be well compared with healthy one with respect to density and morphology. Degenerative and rheumatoid diseases usually start, however, at the bone-cartilage-interface, which is hardly accessible. The direct influence on the bone itself becomes only visible at later stage. For the development of suitable therapies against degenerative cartilage damages the exact three-dimensional description of the
bone-cartilage interface is vital, as demonstrated for transplanted cartilage-cells or bone-cartilage-constructs in animal models. So far, the morphological characterization was restricted to magnetic resonance imaging (MRI) with poor spatial resolution or to time-consuming histological sectioning with appropriate spatial resolution only in two rather arbitrarily chosen directions. Therefore, one should develop μCT to extract the features of low absorbing cartilage. The morphology and the volume of the inter-vertebral cartilage disc of lumbar motion segments have been determined for one PMMA embedded specimen. Tomograms were recorded using nanotom® (Phoenix|x-ray, Wunstorf, Germany), μCT 35TM
(Scanco Medical, Brütisellen, Switzerland), 1172TM and 1174TM (both Skyscan, Kontich, Belgium), as well as using the
SRμCT at HASYLAB/DESY. Conventional and SRμCT can provide the morphology and the volume of cartilage between bones. Increasing the acquisition time, the signal-to-noise ratio becomes better and better but the prominent artifacts in conventional μCT as the result of inhomogeneously distributed bony tissue prevents the exact segmentation of cartilage. SRμCT allows segmenting the cartilage but requires long periods of expensive beam-time to obtain
Synchrotron radiation based X-ray microtomography was applied for the morphometric analysis of polyurethane scaffolds (polymer foams) intended for the use as a biocompatible replacement material. The X-ray microtomography apparatus used for this study is described in detail. The full data evaluation process including X-ray image recording, tomographic reconstruction and the subsequent data reduction steps is explained. The 3-dim. segmentation of the scaffolds and the results of the morphometric analysis are presented.
The paper presents the three dimensional analysis of the geometric structure of different aluminium foams by means of micro tomography at spatial resolutions of 10 μm using a synchrotron radiation based setup, and 100 μm using a tabletop cone beam setup, repectively. The most important methods for the calculation of foam structure parameters by means of 3D image processing methods like feature segmentation and labelling as well as granulometry are described and applied to different closed-cell Al-foams produced by a powder-metallurgical processing route. The analysis steps can be used as a standard procedure to characterize the structure of closed as well as open cell foams or other kind of porous materials like e.g. sponges. As an example, the temporal development of foams during their ageing could be observed by ex-situ determination of the geometric structure parameters. Furthermore, the special properties of monochromatic synchrotron radiation have been used to study quantitatively not only the pore- and cell-wall space at a high resolution, but also the distribution and geometric parameters of the blowing agent TiH2.