Application of Nano-CT and High-Resolution Micro-CT to Study Bone Quality and Ultrastructure, Scaffold Biomaterials and Vascular Networks

Abstract

The application of micro-CT technology to biomedical and bone research is considerable and growing. This chapter focuses on applications requiring particularly high spatial image resolution in micro- and nano-CT imaging. Specific examples described here include the analysis of bone for fine-scale architecture and material quality, the study of synthetic bone scaffolds for orthopaedic research and the imaging of vascular networks. The range of potential research applications of microtomographic technology is both facilitated and limited by technical and physical factors related to the technology. Some technical requirements can be mutually exclusive, such as increased X-ray source power for dense materials and decreasing micro-focus X-ray source spot size for better spatial resolution. Such challenges necessitate innovative solutions at the forefront of the developing technology and include (a) attaining submicron resolution (“nano-CT”) tomographic imaging, (b) obtaining optimum resolution and image quality from a desktop system over a wide range of sample sizes, and (c) obtaining sufficient X-ray transmission and detection to image high-density samples at a useful resolution The first of these challenges is addressed by the development by Skyscan of the 2011 nano-CT scanner. This employs an X-ray source using new technology to obtain a spot size of 0.3µm, combined with an extremely high precision sample manipulator and highly sensitive X-ray camera. With this instrument, pixel sizes of down to 150nm are possible. Structural features linked to bone quality, such as osteocytes and microcracks in bone, and resorption lacunae, are readily visualised. The latter two challenges relate to more “conventional” micro-CT applications are addressed by the unique design of the Skyscan 1172 scanner with adaptive geometry in which both the sample and the X-ray camera can move in order to optimise X-ray imaging geometry. Also, the use of a very large 10-megapixel camera format broadens the possible scan parameters to very small pixel sizes and large objects.