Shape memory alloys (SMAs) belong to 'intelligent' materials since the metal alloy can change its macroscopic shape as
the result of the temperature-induced, reversible martensite-austenite phase transition. SMAs are often applied for
medical applications such as stents, hinge-less instruments, artificial muscles, and dental braces. Rapid prototyping
techniques, including selective laser melting (SLM), allow fabricating complex porous SMA microstructures. In the
present study, the macroscopic shape changes of the SMA test structures fabricated by SLM have been investigated by
means of micro computed tomography (μCT). For this purpose, the SMA structures are placed into the heating stage of
the μCT system SkyScan 1172™ (SkyScan, Kontich, Belgium) to acquire three-dimensional datasets above and below
the transition temperature, i.e. at room temperature and at about 80°C, respectively. The two datasets were registered on
the basis of an affine registration algorithm with nine independent parameters - three for the translation, three for the
rotation and three for the scaling in orthogonal directions. Essentially, the scaling parameters characterize the
macroscopic deformation of the SMA structure of interest. Furthermore, applying the non-rigid registration algorithm,
the three-dimensional strain field of the SMA structure on the micrometer scale comes to light. The strain fields obtained
will serve for the optimization of the SLM-process and, more important, of the design of the complex shaped SMA
structures for tissue engineering and medical implants.
The radio-contrast agent Angiofil has recently been developed to be predominantely applied in forensic medicine. Angiofil is a liquid radio-contrast agent based on iodine. Its viscosity is easy to adjust by the choice and the concentration of the solvent. Therefore, it is well suited for penetrating vessels of different diameters. The liquid Angiofil avoids the sedimentation of suspensions containing radio-opaque materials such as barium sulfate. The injection of
Angiofil into the vascular system of mice post-mortem results in remarkable data showing the vascular trees of tissues and entire organs. Penetration into the surrounding tissue was not observed. Consequently, Angiofil has the potential to reach the performance of the established casting agent Microfil.
In the field of tissue engineering, micro computed tomography (μCT) should allow non-destructively assessing the extra-cellular
matrix deposited by cells within porous scaffolds in-vitro. While synchrotron radiation-based μCT combines micrometer resolution with a high signal-to-noise ratio (contrast), recent advances in desktop μCT devices have achieved comparable results with benefits in availability and user-friendliness. In this study we compare the performance of the commercially available, entry-level desktop device 1174 (SkyScan, Belgium) with the μCT at HASYLAB (DESY,
Hamburg, Germany) by characterizing porous interconnected 3D scaffolds and monitoring the development of engineered human bone constructs upon culture in such an environment. Expansion of human osteogenic cells has been performed with the use of perfusion bioreactors and 3D scaffolds, serving as cell carriers. Constructs based on low X-ray absorbing, rapid-prototyped fibrous scaffolds were analyzed with a nominal spatial resolution of better than 5 μm. Direct 3D image analysis allowed for the accurate quantification of the scaffold morphometry parameters, where both μCT techniques yielded comparable results. However, due to the monochromatic nature of X-rays available at the synchrotron radiation source, drastically reduced beam hardening effects and higher density resolution (higher dynamic range) has been obtained at HASYLAB. Studies in this direction could be useful to highlight the mechanisms that are involved in bone-like tissue growth and to further understand how it can be affected by the choice of cell type, 3D culture environment and scaffold type and architecture.
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 35<sup>TM</sup>
(Scanco Medical, Brütisellen, Switzerland), 1172<sup>TM</sup> and 1174<sup>TM</sup> (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